Ng Dung Mang No Ron Nhan Tao Trong Du Bao Ngan

B GIO DC V O TO

TRNG I HC NNG NGHIP I ------------ c a -------------

DIP XUN TRNG

NG DNG MNG N RON NHN TO TRONG D BO NGN HAN PHU TI IN

KHU Vc TNH SC TRNG

LUN VN THC s K THUT

H NI - 2007

Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

B GIO DC V O TO

TRNG I HC NNG NGHIP I ------------ c a -------------

DIP XUN TRNG

NG DUNG MANG N RON NHN TAO TRONG D BO NGN HN PH TI IN

KHU vc TNH SC TRNG

LUN VN THC s K THUT

Chuyn ngnh: in kh ho sn xut nng nghip v nng thn

M s: 60 52 54

N gi hng dn khoa hc: TSK H TR N H O I LINH

H NI - 2007


LI CAM OAN

Ti xin cam oan y l cng trnh nghin cu ca ring ti. Cc s liu, kt qu

nu ong lun vn l trung thc v cha tng c ai cng b ong bt k cng trnh

no khc.

Ti xin cam oan rng cc thng tin trch dn trong lun vn u c ch r

ngun gc.

Hc vin

Dip Xun Trng

iTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

LI CM N

Sau hn hai nm hc tp v nghin cu ti Trng i hc Nng Nghip I vi

mc ch l nng cao kin thc ca bn thn v honh thnh lun vn cao hc, ti

nhn c s quan tm gip to ln v tn tnh ca cc thy c gio v bn b cng

lp. Cho php ti c by t cm n su sc n thy gio hng dn: Tin s khoa

hc Trn Hoi Linh, ngi tn tnh hng dn, ch bo v gip ti hon thnh

lun vn. Trong thi gian hc tp ti trng ti xin cm n n cc thy c gio trc

tip ging dy v ch bo ti.

Xin chn thnh cm n K s Nguyn Vn Nhim v cc anh ch vn hnh Trm

bin p 220 k v ca Cng ty in lc Sc Trng gip v to iu kin cho ti

lm vic.

Xin c by t s cm n n cc cn b khoa Sau i hc, Cc cn b b mn

Cung cp v S dng in cng nh cc hc vin lp cao hc C in 14 quan tm

gip , to iu kin cho ti hc tp v nghin cu.

Chn thnh cm n cc cn b Vin C in Nng Nghip v Cng ngh Sau thu

hoch n v qun l to iu kin tt nht cho ti hon thnh kho hc.

Ti v cng bit n nhng ngi thn trong gia nh quan tm, ng vin v l

ch da tinh thn vng chc gip ti hon thnh lun vn ny.

H ni, thng 9 nm 2007

Hc vin

Dip Xun Trng

iiTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

Li cam oan i

Li cm n ii

Mc lc iii

Bng k hiu vi

Danh mc hnh vii

Danh mc bng X

M u 1

Chng l Nhu cu thc tin v d bo ph ti in v mt s phng

php d bo hin c 7

1.1 Nhu cu thc tin v d bo ph ti in 7

1.2 Cc phng php d bo ang c nghin cu v ng dng 9

1.2.1 Phn loi cc phng php d bo ph ti in 9

1.2.2 Mt s phng php d bo in hnh 10

1.3 C s xy dng phng php d bo ph ti mi s dng mng

n ron nhn to 13

Chng 2. Gii thiu v mng n ron nhn to 14

2.1 Tr tu nhn to 14

2.2 N ron sinh hc 15

2.3 Mng n ron nhn to 16

2.3.1 Lch s hnh thnh v pht trin 17

2.3.2 M hnh mng n ron nhn to 17

2.3.3 Cc hm kch hot 19

2.3.4 Phn loi cc mng n ron 21

2.4 Hun luyn mng n ron 22

2.5 Hm mc tiu 24

2.6 Mt s ng dng ca mng n ron 25

MC LC

iiiTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

Chng 3 c im biu ph ti tnh Sc Trng 27

3.1 Biu ph ti in 27

3.2 Cc yu t nh hng n ph ti in 28

3.3 Dng biu ph ti 35

3.4 nh v y biu ph ti 3 6

Chng 4. n g dng mng n ron nhn to trong bi ton

phn loi kiu ngy 38

4.1 i tng phn loi 38

4.2 Phng php phn loi dng biu ph ti 38

4.3 Mng Kohonen v ng dng trong phn loi kiu ngy 39

4.3.1 Gii thiu 39

4.3.2 Thut gii SOM 40

4.4 Phng php trng tm m ng dng phn loi kiu ngy 41

4.5 n g dng thut ton v chy th mng 43

4.5.1 X l s liu thu thp 43

4.5.2 Phn nhm biu ph ti 44

4.6 Xy dng giao din d bo hnh dng biu ph ti 50

Chng 5. Xc nh cc thng s u vo cho mng MLP v thut ton

Levenberg - Martquardt 53

5.1 La chn cc thng s u vo phc v qu trnh hun luyn

mng n ron 53

5.1.1 Phn tch tng quan 54

5.1.2 Tm h s tng quan gia cng sut vi cng sut

trong qu kh 56

5.1.3 Mt s kt qu thu c 57

5.2 La chn mng n ron cho bi ton d bo nh v y BPT 62

5.2.1 Mng Perceptron MLP 62

ivTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

5.2.2 Thut ton Levenberg Marquardt 65

5.3 S lc v bi ton d bo d liu 68

Chng 6 Kt qu tnh ton m phng 73

6.1 Xy dng m hnh d bo ph ti cao im v thp im 73

6.2 Phng thc xy dng m hnh 73

6.3 Cc bc tin hnh hun luyn mng vi m hnh 3 75

6.3.1 Xy dng mng d bo nh BPT 75

6.3.2 Xy dng mng d bo y BPT 81

6.4 Xy dng mng cho m hnh 1 83

6.4.1 Cc m hnh d bo nh BPT 83

6.4.2 Cc m hnh d bo y BPT 84

6.5 Xy dng mng cho m hnh 2 85

6.5.1 Cc m hnh d bo nh BPT 85

6.5.2 Cc m hnh d bo y BPT 86

6.6 Tin hnh d bo Pmax Pmin v nh gi sai s 88

6.7 D bo ph ti cho 24 gi sau 91

6.8 Xy dng giao din phn mm d bo BPT 100

Kt lun v kin ngh 104

Ti liu tham kho 108

Ph lc I: 110

Ph lc II: 111

V


CC T VIT TT

HT: H thng in

MNR: Mng n ron

FCM: Phng php trng tm m (Fuzzy Clustering Method)

SOM: Self-Organizing Maps

MBU: Mau khp tt nht (Best Matching Unit)

Pmax: Ph ti cao im

Pmin: Ph ti thp im

Tmax: Nhit cao nht

Tmin: Nhit thp nht

BPT: Biu ph ti

MLP: Mng nhiu lp truyn thng (Multi Layer Percepon)

LVQ: Mng lng t ha vc t (Learning Vector Quantization network)

L-M: Levenberg - Marquardt

viTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

DANH MC CC HNH

S hnh Tn hnh Trang

2.1 Cu to N ron sinh hc 15

2.2 N ron n v x l 18

2.3 Hm tuyn tnh 19

2.4 Hm ngng 19

2.5 Hm ngng tuyn tnh 19

2.6 Hm dc 20

2.7 Hm sigmoid 20

2.8 Hm Sigmoid lng cc 20

2.9 a) Mng mt lp b) Mng nhiu lp 21

2.10 Mng truyn thng 22

2.11 Mng hi qui 22

2.12 M hnh hun luyn mng c gim st 23

2.13 M hnh hun luyn mng khng gim st 23

2.14 M hnh hun luyn mng tng cng 24

3.1 Biu ph ti c trng ngy h thng in Sc Trng 28

3.2 Biu ph ti ong hai nm 2004 n 2005 29

3.3 Biu ph ti t 3/1 n 9/1 nm 2005 30

3.4 nh hng nhit n thi quen tiu th in 31

3.5 th ph ti mt ngy thng v ngy quc khnh 32

3.6 th ph ti mt ngy thng v ngy tt dn tc 32

3.7 th ph ti mt ngy thng v ngy c l hi 33

3.8 th ph ti m c chung kt Euro v m bnh thng 34

3.9 th ph ti ngy bnh thng v ngy c ct in

vii

34


3.10 Biu ph ti in hnh ca mt ngy 3 5

3.11 Biu ph ti mt ngy sau khi qui chun 36

4.1 Qu trnh dch chuyn ca cc trng tm t v tr ngu nhin ban u

v cc vng s liu 43

4.2 S khi d bo hnh dng th ph ti 50

4.3 Giao din chng trnh d bo hnh dng th ph ti 51

5.1 th ph thuc ca Pmax vo Pmax-1 57

5.2 th ph thuc ca Pmax vo Pmax-7 57

5.3 th ph thuc caPm in vo Pmin-1 58

5.4 th ph thuc ca Pmin vo Pmin-7 58

5.5 th tng quan gia Pmax v cc Pmax trong qu kh 59

5.6 th tng quan gia Pmax v cc Pmin ong qu kh 60

5.7 th tng quan gia Pmin v cc Pmin ong qu kh 60

5.8 th tng quan gia Pmin v cc Pmax trong qu kh 61

5.9 Cu trc mng MLP vi mt lp n 63

6.1 Cu trc mng d bo ph ti cao im Pmax 76

6.2 Sai s phn trm khi thay i phn t lp n vi s ln tnh lp 200 79

6.3 Sai s phn trm khi thay i s ln tnh lp vi 22 phn t c nh 79

6.4 Qu trnh hun luyn mng vi 22 phn t lp n 50 ln lp 80

6.5 Sai s luyn mng gim sau mi chu k tnh lp vi thut ton L-M 81

6.6 Sai s phn trm khi thay i s phn t lp n vi s ln tnh lp 200 83

6.7 Sai s phn trm khi thay i s ln tnh lp vi 9 phn t c nh 83

6.8 Sai s phn trm Pmax khi thay i s phn t lp n vi s ln tnh lp 200 84

6.9 Sai s phn trm Pmin khi thay i s phn t lp n vi s ln tnh lp 200 85

6.10 Sai s phn trm Pmax khi thay i s phn t lp n vi s ln tnh lp 200 86

6.11 Sai s phn trm Pmin khi thay i s phn t lp n vi s ln tnh lp 200 87

6.12 Sai s phn trm tt nht trn 3 m hnh khc nhau 88

viiiTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

6.13 BPT d bo v thc t ca Pmax v Pmin t 1 n 31/7 nm 2006 91

6.14 Biu ph ti thc t v d bo ngy 19-23 thng 6 100

6.15 BPT H i cc ngy lm vic thng 2/2004, 2005 100

6.16 Giao din d bo biu ph ti cho 24 gi sau 101

ixTrng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

DANH MC CC BNG

S bng Tn bng Trang

4.1 Kt qu phn nhm th su thng 7 47

4.2 Kt qu phn nhm ngy th by thng 7 48

4.3 Kt qu phn nhm ch nht thng 7 49

4.4 Kt qu phn nhm th hai thng 7 49

4.5 Kt qu phn nhm cho c hai nm 2004, 2005 50

5.1 Kt qu phn tch tng quan gia Pmax v 20 yu t 51

5.2 Kt qu phn tch tng quan gia Pmin v 20 yu t 58

6.1 S liu hun luyn cho hai nm 2004 v 2005 77

6.2 S liu dng kim tra nm 2006 77

6.3 Kt qu d bo Pmax v Pmin t 1/7 n 31/7 89

6.4 Kt qu d bo Pmax v Pmin t 13/2 n 19/2 92

6.5 Kt qu d bo ph ti 24 gi, ngy 13/2/2006 91







X


M U

l Tnh cp thit ca ti

Trong nhng nm gn y, thc hin tin trnh cng nghip ha, hin i ha

t nc y nhanh s pht in ca nn kinh t, ng dng cc thnh tu khoa

hc cng ngh dn n nhu cu s dng in tng cao. Theo d bo ca Tng cng

ty in lc Vit Nam nhu cu ph ti in ong giai on 2006-2010 tng 16-

17%/nm. Tnh n ht 12/2006 in li Quc gia ph n 97,84% s x, 98%

s huyn v hn 93% s h dn c dng in. Vi tc pht trin ph ti n

th cng tc d bo ph ti l mt trong nhng ti quan tm ch yu trong lnh

vc pht in, truyn ti v phn phi in nng.

Bn cnh vic xy dng thm nhiu nh my, ng dy ti in, trm bin p

nhm p ng nhu cu ngy cng tng cao ca cc trung tm ph ti, dn n cc h

thng truyn ti phn phi hot ng khng m bo k thut, thiu ng b, c

bit vic nng cp h thng in khng da trn qui hoch tng th vn cn mang

tnh t pht, ty tin. Hu qu li hng lot vn cn khc phc nh: mt cn

i ngun v li in, gia cung v cu, tinh cy cung cp in, cht lng

in nng khng cao, tn tht cng sut, tn tht in nng trong h thng qu ln

[2] cc nguyn nhn l do hn ch v vn u t, nhng nguyn nhn quan trng

ch yu l lp k hoch vn hnh HT. Trong k hoch ha vn hnh HT nh

phn phi mt cch kinh t, hiu qu, ln k hoch bo dng v sa cha,... nhiu

hot ng thng c thc hin da trn vic d bo ph ti.

D bo ph ti c th c phn thnh: D bo di hn t 10 n 30 nm, d

bo trung hn t 3 n 10 nm v d bo ngn hn (gi, ngy, thng, ma nm). D

bo ngn hn ch yu phc v vic iu hnh sn xut, truyn ti v phn phi nng

lng phc v cho nhu cu trc tip ca sn xut v i sng, lp k hoch sn xut

v kinh doanh.

1Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-

Nu d bo ph ti in qu tha so vi nhu cu thc t th dn n vic phi

huy ng mt s lng ln ngun pht, nhng thc t khng dng ht cng sut ca

chng s gy lng ph. Nu kt qu d bo ph ti in qu thp so vi nhu cu thc

t s dn n tnh trng thiu ngun in, nh hng n pht trin ca nn kinh t

quc dn. Khi kt qu d bo tt s gip cho vic huy ng ngun tt v iu

cng tt c li ch v kinh t.

nc ta d bo ph ti ngn hn cng thu ht s quan tm nht nh trong

ngnh in, cc trng i hc v Vin nghin cu. Mt vi cng ty in lc, c

quan iu quc gia bt u xy dng chng trnh d bo ph ti in. Ngoi

mt s nghin cu ng dng m hnh hi quy. C th thy rng nhu cu d bo ph

ti ngn hn cc cng ty in lc ch c thc hin bng phng php chuyn

gia da trn kinh nghim ca cc k s iu . Nn mang tnh ri ro v chnh

xc khng cao. Mc khc, d bo ph ti trc y ch tp trung d bo cho cc

thnh ph ln nh H Ni hay TP H Ch Minh cn cc tnh vng nng nghip,

nng thn m c bit l tinh Sc Trng cha c chng trnh d bo ph ti, hot

ng d bo da vo kinh nghim v iu hnh trc tip. Vic p dng mng n

ron nhn to cho d bo ph ti in cho mt tinh thun nng nghip nh Sc

Trng da n yu cu n gin, c tnh n nh hng ca nhit v c th

ngy, cho kt qu d bo vi sai s chp nhn c l hng ca nghin cu ny.

2 Kh nng ng dng mng n ron nhn to trong bi ton d bo

Bi ton d bo ph ti c pht in t rt lu vi rt nhiu m hnh

c xut. u thp nin 90 m hnh d bo bng cng ngh mng n ron bt

u c nghin cu v pht trin v cng c mng n ron c th p dng trong cc

d bo di hn, trung hn v c ong d bo ph ti ngn hn, cho kt qu kh

chnh xc. M hnh mng n-ron d bo ph ti ang c ng dng nhiu nc

c th trng in pht trin nh M, c, Anh, Php... Cc m hnh mng thng

c cu trc tng th ging nhau. Hin nay khng ch Vit Nam m ngay c cc

cng ty in lc v th trng in n th gii vn tip tc tm kim cc thut ton

mi phc v cng tc d bo t mc chnh xc v nhanh chng hn. Tuy nhin i


vi tng h thng vi nhng c trng ring ta khng th s dng cc m hnh vi

cc thng s ca h thng khc m vn cn phi xc nh cc cu trc v thng s

ti u cho h thng ca ring mnh.

Vit Nam bi ton d bo ph ti ngn hn c gii quyt bng nhiu

phng php khc nhau nh: Phng php ngoi suy, phng php san bng hm

m, phng php hi qui a bin,... c xut ong d bo ph ti ngn hn.

C th nhn thy rng nhc im ca cc phng php trn l m hnh d bo

lng in nng tiu th ch hiu qu i vi mt s ngy bnh thng nhng li

khng hiu qu i vi tt c cc ngy. Vi nhc im n thc cc

chuyn gia vn hnh pht trin phng php chuyn gia: phng php da n mt

s qui tc (lut) ca cc chuyn gia v chuyn ngnh d bo, nn mang tnh kinh

nghim, nh hng, ph thuc vo nh ca c nhn chuyn gia. Thng cc

quy lut ny c m t bi quan h hm n gin nn khng th hin cc

mi lin h phc tp gia cc thng tin h thng in.

Cc phng php trn v ang c s dng nhng vn cn mt s hn ch

nh: Ph ti l mt i lng ph thuc (phi tuyn) vo rt nhiu yu t, c th k

ti s ph thuc ca lng in tiu th vo cc thng s thi tit nh nhit ,

Nn s gi chiu sng, cc s ph thuc ny c quan h rt mt thit nhng ht sc

phc tp, kh xc nh cc qui lut hm chnh xc. Hin nay, vic pht trin ca

my tnh cho php ta s dng cc m hnh phc tp m vn m bo thi gian tnh

ton ph hp.

Mt khc, h thng in l mt ong nhng h thng c tnh phi tuyn cao.

Phn tch, gim st v iu khin HT lm vic vi hng trm bin trung gian

khng phi lc no cng o lng c. Trong khi , mng n ron nhn to c

thit k tm hm quan h trc tip gia cc bin u vo v u ra, khng cn

phi tm cc mi lin h gia cc bin trung gian. Mng n ron l phng tin c

kh nng hc t cc s liu qu kh v tm ra cc mi quan h ph thuc phc tp


gia cc bin thm ch khi khng xy dng c m hnh ton hc ca bi ton.

Mng n-ron c th lm vic vi cc d liu khng y hoc d liu b nhiu.

khc phc cc hn ch trong x l cc hm quan h phi tuyn, lun vn s

s dng cng ngh tr tu nhn to m mng n ron l mt i din ng dng

ong d bo ph ti Vit Nam. Cc nghin cu hin nay v lnh vc ny vn cn

giai on bt u pht trin. Cc nghin cu v ng dng cc cng c d bo

ong v ngoi nc vn ang c thc hin, nhng nhu cu thc t vn cha c

p ng y .

3. i tng, mc tiu v nhim v nghin cu

i tng nghin cu ca lun vn l d bo ph ti ngn hn da trn cc

biu ph ti ong qu kh, cc c im, tnh cht ca biu ph ti, cc thng

s kh tng. M hnh d bo mng n ron.

Mc tiu ca lun vn l nghin cu, xy dng m hnh d bo ph ti in c

chnh xc cao. M hnh s s dng mng n ron ong tnh ton, s c chng

trnh m phng vi giao din thun tin cho ngi s dng. t c mc tiu

n ti cn thc hin nhng nhim v sau:

1) Nghin cu v cc phng php d bo v ang c s dng trong bi

ton d bo ph ti in ngn hn, c xem xt cc u nhc im tng

phng php.

2) T xut gii php s dng MNR theo m hnh hai bc:

Bc 1: Phn nhm cc biu ph ti (BPT) trong qu kh d bo

hnh dng BPT da trn tng mng t t chc Kohonen (Self-

Organization Map) vi thut ton tm trng tm c p dng l Fuzzy

Clustering Method (FCM). Thut ton s xp cc BPT ong qu kh ca cc

ngy theo th trong thng tng i ging nhau vo mt nhm nh (th by,

ch nht, th hai - th su.. .)


Bc 2: T BPT d bo, dng mng n ron nhiu lp Multi-layer

percepon (MLP) vi thut ton Levenberg-Marquardt c s dng xy

dng m hnh d bo cng sut cc i v cng sut cc tiu. Cc b thng s

u vo l cc cng sut cc i, cc cng sut cc tiu trong qu kh v

thng s thi tit (c th l nhit ). Vic tnh ton c thc hin n my

tnh vi phn mm Matlab.

3) Lp trnh tnh ton, m phng xc nh cc thng s ti u cho m hnh,

chnh xc ca kt qu d bo.

4) Nghin cu cc hng pht trin lun vn

ngha khoa hc: ng dng mt phng php mi phc v cng tc d bo

ph ti. Rt ngn thi gian d bo ph ti.

ngha thc tin lun vn: Xy dng phng php d bo ph ti mi cho

mt tnh thun nng nghip nh Sc Trng, l ti liu tham kho cho nhn vin iu

hnh h thng in.

Trong khun kh lun vn ny, ch nghin cu phng php d bo ph ti ngn

hn. i tng c th ca nghin cu l d bo ph ti cho 24 gi sau, nhm a ra

cc thng s ph ti ca ngy hm sau phc v cng tc vn hnh v iu HT.

Vic xy dng v kim tra m hnh d bo da trn s liu ph ti thc do in lc

Sc Trng cung cp, cng vi b s liu nhit cao nht, thp nht trong ngy do

Trung tm d bo kh tng thy vn tnh Sc Trng thu thp.

Gm nhng ni dung chnh sau:

Phn m u trnh by tm tt cc vn , ang v s gii quyt trong lun

vn, d kin cc gii php s dng, d kin cc kt qu ca lun vn.

Chng 1 trnh by c th nhu cu thc tin v m hnh d bo ph ti in v

cc phng php ang c ng dng trong v ngoi nc, kho st cc phng

php d bo in hnh ang c ng dng v nhu cu xy dng phng php mi.


Chng 2 trnh by nhng nghin cu c bn v mng n ron nhn to: Qu

trnh hnh thnh pht in, mt s khi nim c bn, cu trc, cc loi mng v kh

nng ng dng ca mng n ron nhn to

Chng 3 tm hiu cc c im biu ph ti tinh Sc Trng bao gm cc

nguyn nhn nh hng n biu ph ti in nh thi quen sinh hot, thi v,

cc ngy l tt v nh hng ca thi tit n BPT in.

Trong chng 4 l phn ng dng tng mng Kohonen trong vic phn

nhm cc loi kiu ngy: Trnh by tng c bn mng Kohonen xut thut

ton FCM gii bi ton Kohonen, phn loi BPT v chng nh d bo hnh

dng th ph ti cho mt ngy.

Chng 5 i v phn xc nh cc thng s u vo cho mng MLP bng vic

xt mi tng quan gia cc yu t, k thut lan truyn ngc v thut ton

Levenberg - Marquardt.

Chng 6 l phn in khai m hnh thc t mng n ron ong d bo ph ti

ngn hn. Trn c s cc u vo xc nh kt hp vi yu t thi tit s xy

dng cc m hnh d bo khc nhau, mi m hnh c nh gi sai s, la chn

m hnh d bo cho sai s thp nht. Xy dng giao din d bo cho 24 gi trong

ngy.

Tip sau chng 6 l phn kt lun chung ca lun vn.

Cui cng l ti liu tham kho.


CHNG 1

NHU CU THC TIN V D BO PH TI IN V MT S

PHNG PHP D BO HIN C

l l Nhu cu thc tin v d bo ph ti in:

in nng l mt sn phm c bit quan trng i vi s pht trin kinh t,

x hi, i sng dn sinh v chnh i vi bt c quc gia no trn th gii.

Khng ging nh cc sn phm khc trong nn kinh t th trng vi mc tiu l li

nhun, khi khng c li nhun th ngng sn xut, in l mt sn phm c bit

khng th thiu c, nn ngnh in c xem l mt mt ngnh thuc c s h

tng. in nng khc vi cc sn phm hng ha nh n c kh nng p ng

nhanh chng nhng bin i ca nhu cu ti mi thi im v tnh hu nh khng

th d tr c. Do , vn d bo ph ti mt cch chnh xc cng nh ton b

cc khu sn xut, truyn ti, phn phi, phi lun tnh trng sn sng p ng

nhu cu ph ti l yu t c bn nh hng n hiu qu phc v khch hng ca h

thng.

Hin nay, vi s ra i ca Lut in lc, sc p v nng cao hiu qu kinh t

trong sn xut, truyn ti v phn phi i vi ngnh in ngy cng tng. c bit

trong thi gian ti, khi th trng in ra i v in nng tr thnh mt mt hng

mua v bn theo gi c th trng, d bo ph ti ong iu kin s ng vai

tr quan trng hng u trong vic hnh thnh gi in v v vy n thnh mt

vn sng cn ca ngnh in.

Trong cng tc vn hnh, lp phng thc vn hnh ngy v phng thc vn

hnh tun ca ngi lm cng tc iu , d bo ph ti ngn hn bao gm: d

bo trc mt gi, mt ngy hoc mt tun, ng mt vai tr v cng quan ng.

Nhng phng thc vn hnh c bn trong ngy nh huy ng ngun, phi hp

thy in v nhit in, truyn ti cng sut gia cc min, gii quyt cc cng tc


sa cha n li in v nh gi an ton HT u i hi phi c d bo ph

ti chnh xc.

Chng ta bit rng nhu cu tiu dng in nng ph thuc vo trinh pht

trin ca nn kinh t quc dn, v th d bo ph ti in l mt b phn ca d bo

pht trin kinh t. Nu chng ta d bo cao hn thc t s lm chi ph tng mnh, do

phi huy ng khng cn thit cc ngun in d phng t tin nh diesel, cc

my pht chy du DO.. .Ngc li nu d bo thp hn thc t s dn n kt qu

ngun d phng thp, gim an ton cung cp in, c th phi ct in do vic

huy ng thiu ngun, khng nhng gy thit hi v kinh t, an ninh x hi, i

sng sinh hot nhn dn m cn m cn lm gim uy tn phc v khch hng.

Theo EVN, nm 2006 c cu tiu th in Vit nam c nhiu chuyn bin,

thnh phn ph ti sinh hot gim t 43,3%, cng nghip tng t 47,43%, tuy

nhin s chnh lch ph ti cao im (ph ti cao nht trong ngy Pmax l khong

7000MW) v thp im (ph ti thp nht ong ngy Pmax l khong 4500 MW)

c t s p max/ p min khong 1,6 y l mt s chnh lch ln. Pmax v Pmin

cng chnh l hai gi tr ph ti c bit trong th ph ti ngy v c ngi lm

cng tc iu quan tm nhiu nht trong qu trnh vn hnh, v mt vn hnh vi th ph ti bin ng ln, thnh phn thay i, qu trnh khi ng my pht

din ra thng xuyn nh hng n tui th v ch tiu kinh t k thut ca nh

my, tn tht cng sut v in nng cng s gy nhiu bt li. Ph ti cao im l

nhn t quyt nh vic huy ng cc ngun nhit in, tua bin kh, iesel d phng

nhm m bo ngun ph nh v d phng nng, tng an ton cung cp

in. Ph ti thp im quyt nh vic phi hp v iu chnh cc ngun tua bin

kh, nhit in, thy in m bo vn hnh kinh t. Trong d bo ph ti lc

cao im Pmax l khu quan trng nht.

Trong thi gian ti khi HT Vit Nam c u ni vi cc HT ca Trung

Quc, Lo v cc nc trong khu vc, th vn tng tin cy cung cp in, vn

hnh kinh t v an ton HT cng tr nn bc thit. Do , gii quyt tt vn


cung cp in c vai tr v ngha v cng to ln. V vy, vic nghin cu v p

dng m hnh d bo khc nhau nhm tm ra m hnh d bo ti u cho vn d

bo ph ti l ti nghin cu khoa hc rt cn thit i vi cc trung tm iu

trong vn hnh ti u HT ca mnh.

l 2 Cc phng php d bo ang c nghin cu v ng dng

l 2l Phn loi cc phng php d bo ph ti in ngn hn [5]

D bo lun gi vai quan trng trong nhiu lnh vc, quyt nh k hoch

sn xut, hng u t pht in trong tng lai, do c rt nhiu cc m hnh

ton hc p dng cho d bo. Phng php thng c dng nht l phng php

tip cn v m i vi bi ton d bo v c gng lp m hnh ca ph ti ong

tng lai sao cho n phn nh hnh vi v tnh cht ca n trong qu kh.

C nhiu cch phn loi phng php d bo ph ti in ngn hn ta c th

ly v d mt s phn loi nh sau:

> Phn loi theo tnh ng. Chia lm hai loi c bn: Phng php m hnh thi

gian trong ngy v phng php m hnh ng.

Trong m hnh thi gian trong ngy, ph ti c biu din mt ln di dng

chui thi gian ri rc (discrete) cha cc gi tr d bo cho tng gi cho c giai

on d bo. Thng thng ph ti c m hnh ha di dng tng ca mt biu

ph ti tiu chuNi (Standard Load Curve - SLC) v phn d.

Cc m hnh ng th cho rng khng ch l hm ca thi gian trong ngy m

cn ph thuc vo hnh vi trong qu kh ca ph ti - cc gi tr ph ti ca cc gi

trc .

> Phn loi theo m hnh xc nh/bt nh (deterministic/stochastic)

Cc m hnh xc nh ch cung cp cc gi tr ph ti d bo m khng nh

gi sai s d bo. Trong khi , m hnh bt nh a ra gi ph ti d bo nh

gi tr k vng ca mt qu nh bt nh, ngu nhin. M hnh bt nh cho php

tnh cc c tnh thng k ca gi tr ph ti d bo, trong c sai s d bo.


> Phn loi theo m hnh ph ti tng/ph ti theo thnh phn tiu th

Thng d bo ph ti ngn hn s dng m hnh ph ti tng. Mt s cng

trnh nghin cu cng chia ph ti thnh cc thnh phn tiu th khc nhau, tin

hnh d bo cho tng thnh phn tiu th, sau gp ph ti d bo ca tt c cc

thnh phn li thnh ph ti tng d bo. Phng php ny i hi s lng ln

cng vic cn xy dng m hnh hp l cho tng thnh phn tiu th.

1.2.2 Mt s phng php d bo in hnh:

a) Phng php hi qui tuyn tnh:

Hi qui tuyn tnh l m hnh ton hc xc sut v thng k, phn tch mi

tng quan gia hai hay nhiu bin. M hnh hi qui tuyn tnh c xy dng trn

c s gi thuyt quan h gia hai bin ngu nhin l tuyn tnh, sau xc nh

phng trnh ng thng biu din quan h v phng trnh ng thng ny

d bo bin m ta cn tm. M hnh hi qui tuyn tnh l m hnh kinh in, n

gin v kh hiu qu trong thng k v d bo, do c rt nhiu d bo da trn

phng php ny.

Phng php hi qui da trn vic phn tch bn cht hin tng hay s vic

cn nghin cu tm ra qui lut, d on c xu th bin ng ca hin tng, s

vic trong tng lai, l phn tch mi quan h ph thuc gia cc i lng

ngu nhin lin quan n hin tng, s vic cn nghin cu.

Theo nghin cu ca [1] phng php hi qui c ng dng trong d bo

ph ti Pmax v Pmzn ong ngy c xt n yu t nhit cho kt qu sai s trung

bnh l 4%. Phng php ny cho kt qu kh tt khi quan h gia cc bin ngu

nhin l tuyn tnh v ngc li.

b) Phng php chuyn gia:

Phng php chuyn gia d bo c kt qu l cc thng s do cc chuyn

gia a ra, da n trnh uyn bc v l lun, thnh tho v chuyn mn, phong

ph v kh nng thc tin cng vi kh nng mn cm, nhy bn v thin hng

su sc v tng lai (i vi i tng d bo) ca mt tp th cc nh khoa hc,


cc nh qun l cng i ng cc nh cn b lo luyn thuc cc chuyn mn hay

nm ong min ln cn ca i tng d bo a ra cc d bo.

Phng php chuyn gia c u th hn hn khi d bo nhng hin tng hay

qu trnh c tm bao qut rng, cu trc ni chung phc tp nhiu ch tiu, nhiu

nhn t chi phi lm cho xu hng vn ng cng nh hnh thc biu din a dng,

kh nh lng bng con ng tip cn trc tip tnh ton, o c thng qua cc

phng php c lng v cng c chnh xc.

y l phng php tng i n gin, d p dng v c kh nng tm ra tc

thi cc thng s, m cc thng s ny khng d dng lng ha c v m t quy

lut vn ng di dng hm s.

Phng php chuyn gia thch ng c vi c im v yu cu ca mt d

bo nhu cu v tnh hnh hin ti l tnh kh thi cao, cho kt qu nhanh, to ngay

cn c ra cc quyt nh, ng x tc thi, ph hp vi din bin si ng v

trng thi mun v ca i tng. Mc khc, phng php ny cho php d bo

c nhng hin tng t bin ca i tng m thc t xy ra, nu s dng

cc phng php d bo khc rt kh v rt lu a ra kt qu v tin cy cng

khng cao.

Khng phi bt c trng hp no, bt c lc no cng i hi kt qu d bo

phi th hin di dng cc thng s xc nh, m nhiu khi kt qu d bo cng c

th tn ti di dng nhng nhn nh mang tnh cht nh tnh, nhng xu hng,

chiu hng vn ng. Phng php chuyn gia cng rt hu hiu i vi d bo

nng v cht hn lng. Tuy nhin phng php ny c nhc im l thng

mang tnh ch quan nu chn chuyn gia khng ng tiu chuNi th tin cy d

bo thp. Khi kin chuyn gia tn mn tri ngc nhau th qu trnh x l kin

chuyn gia s kh phc tp. Nhiu chuyn gia a ra s liu d bo, nhng c s l

gii li khng r rng, bin giao ng ln, kin cho vic nh gi sai s v

khong tin cy gp kh khn. Vic tp trung cc chuyn gia y ong mt cuc

hp, vic thu hi phiu tr li ng thi hn cng khng c d dng.


c) M hnh thi gian trong ngy (time of day)

dng n gin nht, m hnh thi gian trong trong ngy ly mu ph ti thc

t tun trc lm m hnh d bo ph ti tun sau. Ngi ta c th s dng mt

cch khc l chn ly mt tp mu ph ti ca mt s tun c trng cho cc iu

kin thi tit khc nhau.

Mt m hnh thi gian trong ngy khc l phng php tch ph. Khc bit

gia phng php tch ph vi m hnh trn l hm thi gian. Theo [5] phng

php tch ph cho kt qu c chnh xc cao hn so vi cc hm thi gian.

d) Cc m hnh chui thi gian ngu nhin (bt nh)

Nguyn tc c bn ca phng php ny l u tin chui ph ti theo thi

gian c chuyn thnh chui thi gian dng (Stationary Time Series - tc chui

khng bin i theo thi gian), sau chui dng cn li s c lc nhiu trng.

M hnh ARIMA khng ph hp m t chui ph ti v chui ph ti c cha

yu t ma. V vy, tnh n yu t ma v c bin s nhit thng c gi

l SARIMAX.

Cc m hnh chui thi gian c nhiu u im. Trc ht, l thuyt m hnh

chui thi gian c c s ton hc cht ch v r rng nn d thc hin d bo n

c s l thuyt ny. Cc thng s ca m hnh cng c tnh ton mt cch d

dng. Th tc nh gi thng s m hnh cng khng kh.

Tuy nhin, m hnh chui thi gian c mt s im yu rt ln l tnh kh

thch nghi. V d nh khi ph ti in hay i rt nhanh mt s thi k nht nh

trong nm. Trong m hnh ARIMA, ph ti d bo cho mt gi no v nguyn

tc li l hm ca tt c cc gi tr ti trc , v vy m hnh khng th thch nghi

nhanh vi iu kin mi. gii quyt vn ny, tc tng tnh thch nghi ca m

hnh, ngi ta thng s dng h s qun a vo cc ng s ln hom cho cc

hnh vi gn nht ca ph ti.

Mt nhc im na ca m hnh chui thi gian l x l cc ph ti bt

thng. Nu hnh vi ca ph ti l bt thng trong mt ngy no th s sai lch


ny s c phn nh ong chui ph ti d bo trong tng lai. V vy, gii

quyt vn ny, ngi ta ngi ta thng thay cc gi tr ph ti bt thng ong

chui ph ti qu kh bng gi tr d bo tng ng, tc gi khng bt thng

gi s ca ngy hm .

1.3 Ctf s xy dng phng php d bo ph ti mi s dng mng ntf ron

nhn to

D bo ph ti in ngn hn ong nhng nm gn y c quan tm nghin

cu bi v cc nguyn nhn sau y:

- S dch chuyn th trng in lc Vit Nam t c quyn ngnh in sang

mi trng cnh tranh cao hn trong th trng in, do i hi cc bi

ton d bo phi t c chnh xc cao;

- Khoa hc k thut ngy cng pht trin to nn tng cho mt s l thuyt

d bo mi pht in;

- S pht in ca cng ngh thng tin m ra cc kh nng trin khai cc m

hnh l thuyt cc h thng tnh ton trong thi gian thc.

Mng n ron nhn to c xy dng da n c s m phng hot ng ca

h thng n ron thn kinh sinh hc, do mng n ron nhn to c mt s c im

quan trng ging b no con ngi: l kh nng hc c nhng g c

dy. Qu trnh hc ny c a vo mng theo nhng mu cho trc. Trong qu

trnh ny cc mu th hin quan h gia cc bin c a vo trong mng n ron,

mng s nhn bit c cc quan h sau khi kt thc qu trnh hun luyn. Chnh

do c im ny m mng n ron c ng dng mnh trong lnh vc d bo. Hin

nay m hnh ny cng ang c p dng ph bin mt s nc pht in ong

d bo ph ti. Cc nghin cu ng dng mng n ron ong d bo ph ti cng

bt u thc hin cc trng, vin nghin cu. Tuy nhin, s lng nghin cu t

i cha c s xy dng mt phng php lun c bn ph hp cho cng tc

d bo ph ti ngn hn nc ta.


CHNG 2

GII THIU V MNG N RON NHN TO

2l Tr tu nhn to

Con ngi t nhng ngy u hnh thnh thi k c i vi nhng con s

m nguyn dng c bn. Cho n tn thi im khong gia th k 20, khoa hc

vn ch mi dng li hnh thc cht ch, l gc, ong khi nhng vn thc t

do con ngi c th cm nhn c th ngy li cng phc tp. Chnh v vy, nhng

t tng v cch gii quyt vn hin thc bng hnh thc pht trin cao hn l

khoa hc tu nhn to c hnh thnh trong giai on t cui th k 20 n

nay ong giai on tin hc ang dn pht trin.

Tr tu nhn to c kh nng gii quyt vn bng cch bt chc li suy

ngh ca con ngi iu ny c thc hin da trn cc cng c hin i ngy nay

l cc phn cng x l cao, vi mi trng v kh nng tnh ton ph hp. C th

c ng dng thit k, ch to b no cho cc thit b iu khin thng minh.

Vi tn hiu u vo l nhng tham s qu trnh ca i tng cn iu khin, kt

hp vi nhng tc ng bn ngoi, loi thit b ny s a ra c nhng tn hiu

u ra thng minh, iu chinh thch hp nhng tham s ny a i tng lun

lm vic nh mong mun. Do , tr tu nhn to c bit hiu qu gii cc bi

ton nhiu bin a mc tiu c rng buc, ong khi khoa hc c bn cha th

hoc kh khn trong qu trnh tm li gii ng. Cc cng ngh tu nhn to

thng dng c th k ti l:

MngNron;

L thuyt l-gc m;

Gii thut di truyn.

14


2.2 N ron sinh hc

T hng ngn nm trc y con ngi dy cng nghin cu phng cch

lm cho b no c kh nng t duy. Tuy vy, phi ti th k th 18-19 ngi ta mi

xc nhn c rng b no thc s ng vai tr quan ng bc nht trong nhn

thc v khng nh rng hot ng nhn thc ca con ngi cn gn lin vi hot

ng ca cc b phn c th khc.

B no ca con ngi c khong 15 t n ron thn knh l oa v c s m

nhim nhng chc nng x l nht nh trong h thn kinh bao gm no, tu sng

v cc dy thn kinh. Mi n ron c phn thn vi nhn bn trong, mt u thn

knh ra (gi l si trc axon) v mt h thng dng cy cc dy thn kinh vo (gi l

dendrite). Cc dy thn kinh vo to thnh mt li dy c xung quanh thn t

bo, chim din tch khong 0,25 mm2, cn dy thn kinh ra to thnh trc di c

th t lcm cho n hng mt. ng knh ca nhn t bo thng ch l 1(T* m.

Trc dy thn kinh ra cng c th phn nhnh theo dng cy ni vi cc dy thn

kinh vo hoc trc tip vi nhn t bo cc n ron khc thng qua cc khp n thn

kinh (gi l synapse). Thng thng, mi n ron c th gm vi chc cho ti hng

trm ngn khp ni ni vi cc n ron khc. Ngi t c lng rng li cc

dy thn kinh ra cng vi cc khp ni bao ph din tch khong 90% b mt n

ron (Hnh 2.1).

T hn t bna

Hnh 2.1: cu to n-ron snh hc

Cc tn hiu truyn trong cc dy thn kinh vo v dy thn kinh ra ca cc n

ron l ta hiu in p v c thc hin thng qua cc qu trnh phn ng v gii

15

Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------

phng cc cht hu c. Cc cht ny c pht ra t cc khp ni dn ti cc dy

thn kinh vo s lm tng hay gim in th ca nhn t bo. Khi in th ny t

ti mt ngng no s to ra mt xung in dn ti trc dy thn kinh ra. Xung

ny c truyn theo trc, ti cc nhnh r khi chm ti cc khp ni vi cc n

ron khc s gii phng cc cht truyn in.

C th ni rng h thng thn kinh con ngi c tnh mm do do cho php

n c th pht trin thch nghi vi mi trng xung quanh. Tnh mm do c

th hin bi hai hot ng: s to ra cc khp ni thn kinh (synapse) mi gia cc

n ron v s bin i cc khp ni thn kinh hin c. Mi n ron c th nhn hng

vn tn hiu v cng c th gi hng vn tn hiu i. Cc n ron lin kt vi nhau

to thnh mng. Mt iu c bit l cc n ron rt n gin trong c ch lm vic,

nhng MNR lin kt vi nhau li c kh nng tnh ton, suy ngh, iu khin v lu

tr thng tin.

2.3 Mng ntf ron nhn to

2.3.1 Lch s hnh thnh v pht trin

Mt s cng trnh nghin cu c s cho lnh vc mng n ron c cng b

vo cui th k 19, u th k 20. Cc cng trnh ny tng hp v vt l, sinh l v

vt l hc n ron do cc nh khoa hc: Hermann von Helmholtz, Emst Mach v

Ivan Palov thc hin. Cng trnh u tin ny nhn mnh vo l thuyt hc tp, tm

nhn v hun luyn v.v... m khng c cc m hnh ton c th ca hot ng n

ron.

Nm 1943, khoa hc tr tu nhn to t ct mc hnh thnh vi s pht in

mng n ron u tin do Warren McCulloch v Walter Pitts a ra. K t ,

tng v vic xy dng mt h thng x l hin thc vi tn gi mng n-ron nhn

to {Artificial Neural Network) ra i; bi n c cu trc gn ging vi cu trc b

no con ngi v cch hc tp, lm vic ging nh con ngi.

Nhng nm 50 v 60 l thi k hng thnh ca mng n ron vi cc cng trnh

ca Rosenblan (1960) v mng Perceptron. Nm 1959, Bernard Widrow v Marcian

16


Hoff pht trin mng ADALINE v bi bo bnh gii ca Minsky v Papert v

mng percetron.

Nhng nm 70 MNR ri vo trng thi im lng c v nghin cu v ng dng.

Tuy vy c th k n cc nghin cu v qu trnh hc ca mng nhiu lp, mng t

t chc ca Kohonen, mng kiu b nh kt hp (BAM) ca Anderson, mng

ART1 (Adaptive Resonace Theory NN ) ca Capenter.

Nhng nm 80 l thi k phc hng ca cc nghin cu v ng dng mnh

m ca cc MNR vi nghin cu v thut gii hc da n lan truyn ngc sai s

luyn cc mng nhiu lp c mt vi nh nghin cu c lp tm ra nh:

David Rumelhart, James McCelland... Ngoi ra cn c mt s mng khc nh

mng mt lp ca Hopfield, mng theo kiu my Boltzmann v mng Neoconitron

ca Fukushima.

T u nhng nm 90 n nay vic nghin cu MNR nhn to c nhng

thnh cng to ln v ng dng nhiu lnh vc khc nhau. Ngoi ra MNR cn c

kt hp vi cc k thut khc ca tr tu nhn to: gii thut duy truyn, logic m,

h chuyn gia phn tch d liu v thu thp tri thc phc v cho vic xy dng

cc h thng thng minh lai.

2.32 M hnh mng Ntf ron nhn to

m phng cc t bo thn kinh v cc khp ni thn kinh ca b no

con ngi, trong mng n ron nhn to cng c cc thnh phn c vai tr tng

t l cc n ron nhn to cng cc khp ni.

Mt n ron nhn to l mt n v tnh ton hay n v x l thng tin c

s cho hot ng ca mt MNR. S khi ca hnh 2.2 ch ra m hnh ca

mt n ron nhn to. Quan h gia cc n ron c th hin bng ng ni c

trng s gia chng. y, chng ta xc nh ba thnh phn c bn ca mt

m hnh n ron:

17


Hnh 2.2: N-ron n v x l

Mt tp hp cc cc khp ni, m mi mt trong chng c c trng

bi mt trng s ca ring n. Tc l mt tn hiu Xn ti u vo ca khp ni

s c nhn vi trng s w n. Cc trng s w c th nhn c cc gi tr m v

cc gi tr dng.

Mt b cng tnh tng trng h cc tn hiu u vo ca n ron,

c nhn vi cc trng s tng ng, ri cng kt qu ny vi trng ngng

0, trng ny c lu trong b nh, theo [3] trng ngng c vai tr lm tng

tnh thch nghi v kh nng tnh ton c mng n ron. Php ton c m t

y to nn mt b t hp tuyn tnh.

Mt hm kch hot / (u) gii hn bin u ra ca n ron. Hm kch

hot cng c xem xt nh mt hm nn; n nn (gii hn) phm vi bin

cho php ca tn hiu u ra trong mt khong gi tr hu hn.

Di dng cng thc ton hc, chng ta c th m t mt n ron k bng

cp cng thc sau:

nu = + wx -

=1 *

V y = /( )

18


Ging nh con ngi khi cha tip cn tri thc chuyn mn, MNR nhn

to khi mi hnh thnh cu trc cha c tri thc, c ngha l cc trng s ghp

ni cn c cc gi tr ngu nhin v u ra tn hiu ca n ron cng c gi tr

ngu nhin.

2.33 Cc hm kch hot:

Hm tuyn tnh (Linear funtion) fill)

y = f (u ) = au

Vi a l dc ca hm tuyn tnh, khi dc

a = 1 th hm tuyn tnh c gi l hm ng nht -

hm lp.

Hnh 2.3: Hm tuyn tnh

Hm ngng {Binary step function, Hard limiter

funtion).

u ra hm ny c gii hn vo mt trong

hai gi tr:

U

u

Hnh 2.4: Hm ngng

Hm ngng i xng (Symmetrical Hard limiter

funtion)+1

-1

Hnh 2.5: Hm ngng tuyn tnh

19


Hm dc {Ramp function)

( 1 nu u < - 1y = f { u ) = j u n t - 1 > 1

( 1 nu u 1

Hm Sigmoid (Sigmoid function)

y = / ( ) = ~ rl + e_ *

Hm ny c bit iun li khi s

dng cho cc mng c hun luyn bi

thut ton lan truyn ngc (back-

propagation), bi v n d ly o hm, do

c th gim ng k tnh ton trong qu

trnh hun luyn. Hm ny c ng dng

cho cc chng trnh ng dng m cc u

ra mong mun rod vo khong [0,1].

Hm Sigmoid lng cc (Bsigmoid

function(tansig))

\ - e ~ xy = m = ^

l + e ~ x

Hm ny c cc thuc tnh tng t

hm sigmoid. N lm vic tt i vi cc

ng dng c u ra yu cu trong khong [-

1, 1].

Hnh 2.6: Hm dc

Hnh 2.8: Hm Sigmoid lng cc

i vi cc om v u ra, cc hm kch hot cn c chn sao cho ph hp

20


vi s phn phi ca cc gi tr ch mong mun. Chng ta thy rng i vi cc

gi tr ra ong khong [0,1], hm sigmoid l c ch; i vi cc gi tr ch mong

mun l lin tc trong khong th hm ny cng vn c ch, n c th cho ta cc

gi tr ra hay gi tr ch c cn ong mt khong ca hm kch hot u ra.

Nhng nu cc gi tr ch khng c bit trc khong xc nh th hm hay

c s dng nht l hm ng nht (identity function). Nu gi tr mong mun l

dng nhng khng bit cn trn th nn s dng mt hm kch hot dng m

{exponential output activation function).

2.3.4 Phn loi cc mng Ntf ron:

a) Theo s lp ngi ta chia lm hai loi:

Trong hnh 2.9 (a) Mng mt lp (Perceptron) l mng ch c mt lp vo cng

l lp n v lp ra. Hnh (b), mng gm ba lp hay cn gi l mng (Multi layer

Perceptron). Lp nhp (input), lp n, v lp xut (output). Mi nt trong lp nhn

nhn gi tr ca mt bin c lp v chuyn vo mng. D liu t tt c cc nt

trong lp nhp c tch hp - ta gi l tng ng ha - v chuyn kt qu cho cc

nt trong lp n.

Tng vo Tng ra lang vo rngn rng ra(input) (ouput) (input) (hide) auput)

Hnh 2.9 a) Mng mt lp b) Mng nhiu lp

Gi l n, v cc nt ong lp ny ch lin lc vi cc nt trong cc lp nhp

xut, tng t nt trong lp xut cng nhn cc tn hiu tng trng ha t cc nt

n. Mi nt ong lp xut tng ng mt bin ph thuc. Phn ln cc bi ton ch

c mt bin ph thuc, nhng vi m hnh nh trn, M R cho php s bin ty .

21


Th d, nu mng cn nhn dng cc ch s tn ta c th xy dng mt mng vi 10

nt xut; hoc d bo ph ti chi cn mt nt xut cho c chui gi cn d bo

b) Theo kiu lin kt c th phn thnh:

Mng truyn thng: Cc lin kt n ron i theo mt hng nht nh, khng

to thnh chu trnh vi cc nh l cc n ron

Mng hi qui: Cho php cc n ron to thnh chu trnh, trong mt hoc

nhiu u ra ca phn t lp sau truyn ngc ti u vo ca lp trc.

Hnh 2.10 Mng truyn thng Hnh 2.11 Mng hi qui

Mng t t chc: Xy dng da trn pto ging b no ngi, cc n ron

c phn b trong lp sao cho c mi lin h v khng gian, gha l tn hiu vo

tng t nhau s kch hot cc n ron gn nhau ong khng gian

2.4 Hun luyn mng Nor ron:

Mng n ron khi mi hnh thnh cha c tri thc, tr thc ca mng hnh thnh

dn sau mi ln hun luyn (hc). M R c dy bng cch a vo u vo

nhng kch thch v mng hnh thnh nhng p ng tng ng, nhng p ng

ph hp vi tng loi kch thch s c lu gi Cc k thut hc nhm vo vic

hiu chnh cc trng s v vic iu chnh, sa i cu trc ca mng nh s lp, s

n ron, kiu v cch m cc lp lin kt vi nhau l c nh trong sut qu trnh

hun luyn... M R khi hnh thnh tri thc c th gii quyt cc vn c th

mt cch ng n. l nhng vn rt khc nhau, c gii quyt da trn s

t chc hp nht gia thng tin u vo v p ng u ra ca mng. C rt nhiu

thut ton hc c pht minh tm ra tp trng s ti u lm gii php cho cc

22

Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------

bi ton. Cc thut ton c th chia lm ba nhm chnh: Hc c gim st, hc

khng c gim st, hc tng cng.

Hc c gim st: ln hc u tin mng c cung cp mt mu hc cng

vi b trng s t do, u ra thc t ca mng s c so snh vi u ra mong

mun, sai khc gia hai gi tr ny l c s cho vic hiu chinh trng s ca mng,

qu trnh hun luyn din ra lin tc cng vi b thng s u vo cho n khi

mng t c mt gi tr sai s nh mong mun.

u vo

=r>Mng N ron

u ra thc t

H iu chnh trng s

VSo snh

u ra m ong m un

Hnh2.12 M hnh hun luyn mng c gim st

Hc khng gim st: Trong hc khng gim st th khng c bt k mt thng

tin phn hi t mi trng. Mng phi t tm ra cc c tnh, quy lut, tng quan

trong d liu u vo v tp hp li to u ra. Khi t tm ra cc c im ny,

mng tri qua cc thay i v tham s ca n. Qu nh ny c gi l t t

chc.

u vo M ng N ron

A

u ra thc t

Hiu chnh trng s

Hnh2.13 M hnh hun luyn mng khng gim st

Hc tng cng: Trong lut hc c gim st, cc gi tr u ra c bit chnh

xc i vi mi u vo. Tuy nhin, ong thc t c mt s trng hp ch bit t

thng tin chi tit, chng hn mng ch bit rng gi tr u ra thc s qu cao hay c

th mng ch c c thng tin phn hi bo rng u ra ng hay sai. Thut hc

23


da trn thng tin nh gi ny c gi l thut hc cng c, thng tin phn hi

c gi l tn hiu tng cng.

Hnh2.13 M hnh hun luyn mng tng cng

2.5 Hm mc tiu

hun luyn mt mng v xt xem n thc hin tt n u, ta cn xy dng

mt hm mc tiu (hay hm cht lng) cung cp cch thc nh gi kh nng

ca mng. Vic chn hm mc tiu l rt quan ng bi v hm ny th hin cc

mc tiu thit k v quyt nh thut ton hun luyn no c th c p dng.

pht trin mt hm mc tiu o c chnh xc ci chng ta mun khng phi l

vic d dng. Mt vi hm c bn c s dng rt rng ri.

Hm tng bnh phng li SSE (Sum of squares error function)

Hm trung bnh tng bnh phng li MSE (Mean sum of squares eor

function)

pal .=1

Trong :

P: S th t mu ong tp hun luyn

Z: S th t ca n v u ra

24


tpi v yPi : Tng ng l u ra mong mun v u ra thc t ca mng cho

n v u ra th i n mu th p.

v mt hnh hc c th xem E nh mt mt li. Trong qu trnh luyn mng gi tr E cng nh cng tt.

2.6 Mt s ng dng ca mng n ron nhn to:

T khi ra i v pht trin M R tm v khng nh c v tr ca mnh

trong rt nhiu ng dng c th nh:

+ Mng n ron c th c hun luyn nhn bit vn phong vit ca cc c

nhn v cc nh nghin cu dng so snh cc tc phm ca

Shakespeare v cc nh vn ng thi vi ng do i hc Aston cng b.

+ Mt chng trnh truyn hnh khoa hc ph bin gn y a ra vic s

dng M R do mt vin nghin cu Italia kim a tinh khit ca du

liu.

+ Vin nghin cu in lc hoa k EPRI nghin cu v thng mi ha

phn mm A SLTF (Phn mm d bo ph ti in ngn hn dng M R

nhn to).

Cc v d ny cho thy cc ng dng rng ri ca M R. Cc ng dng ny

ngy cng m rng bi v M R gii quyt vn tt khng ch trong khoa hc, k

thut v ton hc m cn trong y t, kinh doanh, ti chnh, vn hc. ..Cc ng dng

ca M R ti nhiu bi ton trong cc lnh vc khc nhau lm cho M R thm

hp dn. My tnh tc cao hn v cc thut ton nhanh hn cng lm cho vic

s dng M R c th gii c cc bi ton phc tp m trc y i hi mt khi

lng tnh ton to ln.

+ Lnh vc dn dng: iu khin cc thit b gia nh nh my git, iu ha,

cc thit b cnh bo chng trm, bo ng bo chy, d bo thi tit, gi

c...

25


+ Lnh vc cng nghip: Cnh bo pht hin s c, xy dng cc b iu khin

thch nghi, thng minh ha cc cm bin trong o lng, nhn dng v x l

tn hiu, phn loi mu, nhn dng ting ni. D bo ph ti in ngn hn,

trung hn, di hn, vn hnh h thng in. D bo gi in ...

+ Lnh vc y t: hn dng sng in tim, in no , cc t bo ung th.

Trong in no M R dng nhn dng cc sng Alpha, Beta, Theta v

Delta chn on bnh....

+ Lnh vc qun s: iu khin cc v kh thng minh, iu khin bm. hn

dng vn tai, hnh nh ting ni....

+ Lnh vc thng mi, kinh t: D bo tnh hnh kinh t, d on tin t, phn

tch mc ri ro, phn tch th trng, d bo mc tng trng...

Ring ong lnh vc h thng in c ng dng ong chun on s c

(thit b in, in t, c kh trm bin p, ng dy, nh my in), phn lp v

iu khin cc h thng ng ( h my in, trm bin p....), ti u ha, d bo,

nh gi an ton h thng in.

Mng n ron nhn to m chng ta s dng xy dng nn cc M R nhn

to thc s l cn rt th s so vi nhng g c tm thy trong b no. Cc M R

m chng ta xy dng c cng ch l mt s phc tho th kch nu em so

snh vi cc mch thn kinh trong b no. hng vi nhng tin b ng ghi nhn

trn rt nhiu lnh vc ong cc thp k va qua, chng ta c quyn hy vng rng

trong tng lai cc M R nhn to s tinh vi hn nhiu so vi hin nay.

26


CHNG 3

C IM BIU PH TI TNH SC TRNG

3.1 Biu ph ti in

Ph ti ca h thng l mt hm theo thi gian, ph thuc vo nhiu yu t

nh c im ca qu trnh cng ngh, ch vn hnh.v.v.. Tuy nhin i vi mi

h thng ring s c dng biu ph ti in hnh.

Khi bit c biu ph ti in hnh th s c cn c chn cc thit b

in, tnh in nng tiu th. Lc vn hnh nu bit BPT in hnh th c th nh

phng thc vn hnh cc thit b in sao cho kinh t v hp l nht. Cc nh my

pht in cn nm c BPT ca tng h thng nh phng thc vn hnh

ca cc nh my pht in cho ph hp vi yu cu. V vy, BPT l mt ti liu

quan ng ong thit k cng nh vn hnh h thng cung cp in.

Ty theo nhu cu s dng m ngi ta xy dng cc loi biu ph ti in

khc nhau. ng biu din s thay i ca ph ti tc dng p, ph ti phn khng

Q hoc dng in I theo thi gian. Nu theo thi gian kho st c th ph ti

hng ngy, hng thng, hng nm.

Nghin cu BPT ngy ta c th bit c tnh trng lm vic ca h thng

in t nh qui trnh vn hnh mt cch hp l nht m bo vn hnh kinh t

ca h thng in.

Hnh 3.1 l BPT tc dng ngy in hnh ca cng ty in lc Sc Trng.

th bin thin theo gi tr ph ti 24 gi trong ngy. Ph ti Pmax ln gp 1,9-2 ln

so vi ph ti thp nht trong ngy Pmin. Cao im thng xy ra vo chiu ti

khong t 19h-20h. Thp im thng xy ra vo ban m khong 2h-3h.


Hnh 3.1 Biu ph ti c trng ngy h thng in Sc Trng

Nu d bo c Pmax v Pmin cc k s iu hnh c th huy ng v iu

chinh ngun hp l, cng nh vn hnh ngun an ton v hp l hn.

3.2 Cc yu t nh hng n ph ti in:

D bo ph ti l mt bi ton kh. Bi v trc ht chui ph ti in l

chui s liu kh phc tp, ph thuc vo nhiu yu t. Ph ti in ca mt h

thng c cu thnh t cc om v tiu th in khc nhau m ch yu l cc thnh

phn nng nghip, cng nghip, sinh hot v dch v...

Cc yu t nh hng n ph ti ph thuc vo tnh cht ca om v tiu th

in. Ph ti cng nghip ph thuc ch yu vo mc sn xut. Ph ti ny

thng n nh tng i v c th nh gi s ph thuc ph ti cng nghip vo

trnh v quy m sn xut. Tuy nhin, t gc bn bn in, ph ti cng nghip

c tnh bt nh v gy tr ngi cho d bo, bi v c nhng s c my mc thit b

cng nghip hu nh khng d bo c v gy ra nhng bin ng ln trong tng

ph ti ca khu vc v ton h thng.

i vi ph ti nh sng sinh hot, l thnh phn ph ti ph thuc rt nhiu

vo hnh vi ca cc c nhn v cc nhm c nhn ring bit, do rt kh xc nh


nh hng n ph ti in. Mi c nhn thng hnh ng theo cch ring ca

mnh v hnh vi ca h nh hng n tiu th in nng. C th ch ra mt s yu

t hnh vi v x hi nh hng n ph ti nh: Cc ngy l ln, cc ngy ngh,

chng trnh truyn hnh, thi tit thay i lm tng hay gim nhu cu s dng iu

ha, qut in, t lnh...

Sc trng c khong 1,2 triu dn trong c 80% dn s lm nng nghip,

do ph ti in ch yu phc v sinh hot v ph ti nng nghip. i vi ph

ti nng nghip, y l loi ph ti c nh hng ln i vi cc ph ti in ca

a phng ch yu l sn xut nng nghip. y l loi ph ti phc v cc cng

vic nh ti tiu, chn nui, iu tit thy li, ch bin lng thc, ong nui

trng v ch bin thy hi sn l mt loi ph ti in c bit quan trng v s

dng mt lng ph ti ln v phi m bo cung cp lin tc ong mt thi gian

di khi vo ma thu hoch, do ph ti nng nghip thng mang tnh thi v

60

55

50

45

s 40

35

30

25

20

15 500 10000 15000

Gio

Hnh 3.2: th ph ti trong hai nm 2004 n 2005

Hnh 3.2 biu din biu ph ti lin tc trong 2 nm vi s liu c thu

thp ti trm bin p 220 k v ca Cng ty in lc Sc Trng. Ta c th nhn thy

mc dao ng ln trong ng th ph ti ny. Ngoi ra ta c th nhn thy

mt s c im sau:


Thi v:

Da vo ng th thy rng u nm th bt u tng v ph ti t cc

i khong thng 8-9 trng vi khong thi gian thu hoch v h-thu. Mt yu t

nh hng ln lm cho sn in tng cao l vo 2 thng ny v trng vi thi im

thu hoch tm mt sn lng in ln phc v cho ng c to dng chy, thp

sng v st kh oxi vo hai thng cui trc lc thu hoch, bn cnh cng vi vic

thu hoch tm, ph ti cung cp cho cc c s ch bin tm cng tng cao. Ngoi

ra, t thng 1 n thng 4 ng th tng nhanh sau mi gim tc y cng

trng vi thi im cui ma kh khong thng 4.

Biu ph ti ngy trong tun:

Thu hai Thu ba Thu tu Thu nam l iu sa u T1U b a y C hu nhat

Hnh 3.3 th ph ti t 3/1 n 9/1 nm 2005

Xt th ph ti HT hnh 3.3. y l biu ph ti cc ngy trong mt

tun t 3 n 9/1 nm 2005 c xy dng lin tc ong 168 gi. Khng ging nh

ph ti cc thnh ph ln nh H Ni hay TP HCM ph ti thng gim thp

cc ngy ngh th by, ch nht v tng cao cc ngy lm vic. Ph ti Sc Trng

khng tun theo chu k tun, s khc bit BPT trong mt tun cc ngy lm

vic (th 2 n th 6) v ngy ngh (th 7 v Ch nht) thng khng c s thay


i ln, ng BPT trong mt ngy c nhiu nh nhn. y cng l mt s khc

bit ca ph ti gia thnh ph ln v cc tinh nng nghip nh Sc Trng.

Thi tit trong ngy

Thi tit ong ngy l mt tp hp, bao gm cc thng thng s t nhin nh:

nhit , m, tc gi, hng gi v cng nh sng.. .trong tp hp cc

thng s , nhit l yu t nh hng mnh nht ti ph ti. C th xem ph ti

l mt hm s ph thuc vo nhit .

Gia ph ti v nhit l c qui lut ph thuc nh sau: hit tng th

ph ti tng v ngc li. Hnh 3.4 l th ph ti ngy ca hai ngy lm vic ca

HT Sc Trng c nhit khc nhau. Hnh 3.4 gi tr ph ti tng kh lm khi

nhit mi trng tng. Biu ph ti ngy 6/5/2005 l ngy c nhit cao (25.8-

36.2 c) v ngy 19/2/2005 c nhit thp (20.4-25.2 c). C s chnh lch gia BPT

gia hai ngy l l kh ln.

Hnh 3.4 nh hng nhit n thi quen tiu th in

Ngy c bit trong nm:

Sc Trng c 3 thnh phn dn tc l Kinh, Khmer v Hoa sinh sng, ngoi

ngi Kinh chim khong 65% dn s, ngi Khmer chim khong 29% v ngi

hoa chim 6%. Do c cc ngy c bit trong nm nh ngy l, ngy tt, nh tt

m lch, tt (Chn Chm My) v l hi ca ngi Khmer. Cc ngy l ln nh


30/4, 1/5 v 2/9... ph ti cc ngy ny trn u gim so vi ngy thng. S khc

bit trong biu ph ti gia ngy l 2/9 v mt ngy lm vic bnh thng ngy

5/9/2005 ti Sc Trng c th hin n hnh hnh 3.5.

Hnh 3.5 th ph ti mt ngy thng v ngy quc khnh

Hnh 3.6 th ph ti mt ngy thng v ngy tt dn tc

Hnh dng ng ph ti cc ngy tt dn tc hnh 3.6 cng b nh hng do

thi quen sinh hot ca khch hng thay i. D bo ph ti cho cc ngy c bit

khng p dng nh ngy thng m phi theo phng php ring, da vo s thay

i ph ti ca cc ngy ny so vi ngy thng trong cc nm trc. Biu ph

ti ngy mng mt tt ngy 6/2/2005 ng ph ti lc ban ngy thp trong khi ph

ti ban m li tng cao so vi ng ph ti cc ngy bnh thng.


Hnh 3.7 th ph ti mt ngy thng v ngy c l hi

Hnh 3.7 biu din ph ti b gim st ngy 16/10/2005 din ra l hi ua ghe

go (oc Om Bc) ca ngi Khmer v mt ngy bnh thng trc , ngy

15/10/2005.

Cc chng trnh truyn hnh trc tip cc s kin th thao vn ho ln, thu

ht ng o qun chng hm m, c bit l bng c nh hng khng nh n

nhu cu tiu th in nng. Hnh 3.8, dng biu ph ti trong cc ngy truyn

hnh trc tip cc s kin th thao vn ho cng thay i. Cng sut tiu th vo cc

gi truyn hnh trc tip (Cp bng th gii, cp Cl, Euro, Tiger Cup....) BPT

t ngt tng cao.


Hnh3.8 th ph ti m c chung kt Euro v m bnh thng

K hoch sa cha ln:

Sc Trng l mt tnh nh h thng in hin nay c xem l ang pht trin

do nhu cu nh ci to trm bin p, ct in ng dy ang vn hnh ko

ng dy mi, ci to nng cp ng dy.. .vn phi ct in trn din rng, dn

n in nng tiu th gim mt cch ng k.

Hnh 3.9 th ph ti ngy bnh thng v ngy c ct in

D bo cho cc ngy ny cn phi tnh ton khu tr ph ti do ngng cung

cp in. Dng biu ph ti trong ngy c ct in cng mang tnh c th ring,

thay i theo thi gian v khu vc ct in.

Nhn xt:

i vi nhng ngy l tt, cc ngy c bit, nht l nhng ngy ct in trong

nm nh hng n cng tc d bo ph ti. Cc ngy ny xut hin tng i t

ngoi tr nhng ngy ct in. Trong mt nm c khong 20 ngy iu ct in

mt s tuyn phn nh trong tp s liu thu thp c. e m bo tp s liu

hun luyn c lin tc. i vi nhng ngy b ct in ta c th ly trung hnh

ca hai ngy k cn. iu ny l cho php khi ta c tp s liu ln.

Qua qu trnh nghin cu, thng k s liu v kinh nghim vn hnh cc nh

nghin cu, chuyn gia iu i n kt lun: nhit mi trng - thng s thi


tit quan trng nht ong ngy, yu t ma v v cc ngy c bit nh ngy l l

bin nh hng mnh nht n gi ph ti ngy.

3.3 Dng biu ph ti:

Xt th ph ti HT hnh 3.10. y l biu ph ti HT Sc Trng ngy

lm vic 12/12/2004 c xy dng theo gi tr ph ti 24 gi trong ngy. th

ph ti phn b khng u, dng th nhn v chnh lch gia cng sut cc

Hnh 3.10 Biu ph ti in hnh ca mt ngy

t: Trong lun vn ta s s dng k hiu nh sau:

p = \p yP ^ ,...,p ^ - th ph ti ca ngy ang xt

pn = \PnVPnT",P n2A] " ^ chun ha t p

theo cng thc p (z) = Pmin p ^ n Pmax - Pmin

Vi Pmin = min P(i)

Pmax = max P(i)

Ta c th chun ha c max p n(i) = 1

min p(i)= 0


nh trn hnh 3.11

Hnh 3.11 Biu ph ti mt ngy sau khi qui chun

Hnh 3.11 l th ph ti c chun ho ca cc ngy trong tun c

xy dng theo cc bin i v bin P(). Biu ph ti c quy chun vn gi

nguyn dng bin thin ca mnh v cc gi tri ph ti c quy chun nm trong

khong t 0 -- 1, vi Pmax = 1 v Pm in = 0. c im ny khng ph thuc vo

gi tr nh v y ca biu ph ti gi trong ngy c quy chun nhn cc gi

tr ln hay nh n mc no.

3.4 nh v y biu ph ti (BPT):

Xc nh hai gi tr c bit trn th ph ti, ph ti cao im v thp im

l mc tiu quan trng hng u ca ngi lm cng tc d bo. Sau khi xc nh

c hai gi tri quan trng nht BPT Pmax v Pmin cn cc gi tr khc trong

ngy s c xc nh theo mi quan h ca chng vi nh v y ca BPT

thng qua dng BPT ca ngy d bo.

Vy nu bit dng biu ph ti qui chun cn gi l vc t BPT, tc l

bit Pn xc nh c Pmax v Pmin ca TPT trong ngy ta s tnh c ph ti

ca tng gi trong ngy nh sau:


P(i) = Pmn + (Pmax - Pmin)P i

Kt lun:

Da vo cc phn tch trn c th i n kt lun: d bo c ph ti tng

gi P(i) cho mt ngy c th, ta cn xc nh dng biu ph ti - vc t biu

ph ti p(i) vi i=,2,3...24 ca ngy cn d bo v d bo c gi tr ph ti

nh Pmax, gi tr ph ti y Pmn ca ngy .

Cng nh cc phng php d bo khc, d bo ph ti ngy phi da vo

thng k s liu, phn tch v p dng cc thut ton tm ra mi quan h gia ph

ti v cc yu t nh hng v t c th xy dng phng php d bo ph ti

ngy.

Phn tip theo, chng ta s nghin cu gii quyt bi ton d bo hnh dng

biu ph ti, thng qua vic s dng thut ton trng tm m. Tu thuc vo c

im ca b s liu thu thp c s tin hnh phn tch v la chn cch phn

nhm th ph ti sau cho ph hp nht.


CHNG 4

NG DNG MNG N RON NHN TO TRONG BI

TON PHN LOI KIU NGY

4.1 i tng phn loi

i tng phn loi l cc dng biu trong qu kh. Thng thng cc

s liu ny thng c o trong khong thi gian lin tc. tin hnh phn loi

t cc s liu o lng ban u, ngi ta tin hnh gia cng s liu, tm ra cc c

th ca i tng thuc cc nhm khc nhau xp cc biu tng i ging

nhau vo mt nhm. Khi tin hnh phn loi BPT in c th tm ra cc du hiu,

cc du hiu chnh l c s quyt nh s nhm n phn nh thi quen s dng in

ca h thng in , do n mang tnh c th ring i vi tng h thng in.

Bi ton phn loi BPT c hiu l i tm cc quy tc xp cc biu tng

i ging nhau vo cng mt lp.

4.2 Phng php phn loi dng BPT

Thng thng, bng kinh nghim vn hnh ca bn thn, cc chuyn gia lu

nm c th phn bit c cc kiu ngy gc c trng trong qu kh. Tuy nhin,

trong qu trnh vn ng khng ngng ca x hi, c cu kinh t v t ng cc

ngnh cng nghip thay i, thi quen sinh hot khch hng thay i..., theo thi

gian s xut hin mt s kiu ngy mi hoc mt s kiu ngy trong qu kh s

khng xut hin na trong tp hp cc kiu ngy gc c trng m ch vi kinh

nghim ca cc chuyn gia nhiu khi khng pht hin c v cp nht kp thi. V

chnh l nhc im ln trong qu trnh d bo theo kinh nghim ca chuyn

gia.

Vic s dng MNR nhn to phn loi kiu ngy l mt gii php khc

phc c hn ch n. Nh c ch hun luyn li MNR vi cc s liu c cp

nht nh k, h thng d bo c th tm ra v thch ng vi kiu ngy mi pht


sinh khng ging vi mt trong cc dng gc hoc loi b cc kiu ngy khng cn

xut hin na.

Trong qu trnh hun luyn mng, khi a cc mu dng biu ph ti vo

mng, ta hon ton khng a yu cu cn phi thu c kt qu g - bao nhiu

biu mu u ra. Qu trnh hc ny gi l hc khng gim st m MNR nh x

c trng t t chc Kohonen l mt i din mang trong vic phn loi cc biu

ngy trong nm.

Theo cc nghin cu ca [2,6,11] mng Kohonen c ng dng trong vic

phn loi BPT u cho kt qu tt. Hu ht cc nghin cu ny u s dng mng

Kohonen kinh in vi thut ton thng s dng l LQV, tuy nhin lut hc ny

cho kt qu hi t kh chm v mt kh nhiu thi gian hun luyn, hin nay xut

hin mt s thut ton hc mi c ng dng cho vic xy dng mng Kohonen

m in hnh l thut ton ng tm m Fuzzy Clustering Method (FCM) cho kt

qu hi t nhanh hn, thut ton ny s c ng dng phn loi BPT ong

lun vn ny.

4.3 Mng Kohonen v ng dng trong phn loi kiu ngy

4.3.1 Gii thiu

SOM {Self Organization Map) l k thut trc quan ha d liu. Gii thut

c xy dng bi gio s Teuvo Kohonen da trn kin trc mng Kohonen.

im ni bt ca thut gii SOM l n s chuyn cc dng quan h phc tp, thng

k ri rc gia cc i tng d liu a chiu (n chiu) v cc quan h hnh hc trc

quan om gin vi s chiu c rt gn i nhiu ln - thng l mt hoc hai

chiu, v bn cht thut gii c bit n nh l k thut nn d liu da trn vc- t trng s.

Thut gii s xy mng Kohonen lu tr thng tin nh l cch duy tr ca

cc quan h hnh hc bn trong tp hun luyn.

Mt trong nhng kha cnh th v nht l SOM l mt dng ca thut ton

hc phn loi d liu hun luyn m khng cn bt c s gim st bn ngoi no


so vi cc gii thut hc c s gim st truyn thng. Th nn SOM cn c

xem l mt gii thut hc khng gim st.

4.3.2 Thut gii SOM

Thut gii hun luyn SOM c th c m t theo cc bc c bn nh sau:

a. Khi to: Cc vc t trng s cho tng nt trong mng c khi to. Cc

gi tr khi to ny thng c chn mt cch ngu nhin v tha tiu

chun nh.

b. Chn phn t i din: Mt vc t s c chn ngu nhin t tp hun

luyn v tr thnh phn t i din ca nhm.

c. Tm mu khp tt nht (MBU-Best Matching Unit) - phn t neuron chin

thng: Mi nt trn mng s c kim tra tnh xem nt no c ng s

gn vi vector nhp nht. Phn t chin thng c xem l phn t so khp

tt nht MBU.

Thut gii tm mu khp tt nht c thc hin nh sau:

> Duyt tt c cc nt v tnh khong cch Euclide gia vector trng s ca

mi nt v vc t nhp hin hnh.

Cng thc tnh khong cch Euclide c cho nh sau:

V: vc t nhp hin hnh

W: vc t trng s ca phn t c chn

> t c vector trng s gn nht vi gi tr ca vc t nhp s c chn l

MBU

d. Xy dng cc phn t ln cn: Bn knh ln cn ca MBU s c tnh li.

Bn knh c xc nh ln nht thng s l bn knh ca mng, nhng sau


gi tr ny s gim dn sau nhng bc thc hin. Tt c nhng phn t

nm trong bn knh trn s c xem l phn t ln cn ca BMU.

4.4 Phng php trng tm m Fuzzy Clustering Method (FCM):

Thut ton nhm trung bnh (C-means clusterings) c cng b ln u tin

bi Duda v Hart c gi l thut ton Hard C-mean (hay cn gi l Hard

ISODATA). Phin bn ci tin cui cng ca thut ton c Bezdek gii thiu.

Khng ging nh thut ton Kohonen cc trng tm c lin kt bng mt

li, phng php trng tm m cc ng tm hon ton chuyn ng c lp

trong khng gian v ch ph thuc vo s liu.

Phng php trng tm m ngoi vic xt n nt c ta gn vi vc t u

vo nht, cn xt n c nhng nt khc nhng vi ng s nh hom, t l nghch

vi khong cch t nt ti vc t u vo. iu c ngha l mt vc t s ph

thuc vo nhiu nt trn mng, khong cch cng xa ph thuc cng thp. Trn

c s cc trng tm, khng gian s liu u vo c chia thnh nhiu nhm. Mi

nhm c i din bng ng tm ca chng. i din ca mt nhm c gi l

mt nguyn mu.

Trong thut ton ny cc d liu c tnh cht c bit gn nhau c tp hp

thnh nhm, chng c ma trn ph thuc u . Cho tp X mu vi X={xl,x2,..xj},

trong mi nhm xl,x2,..xj c ta 24 chiu. Vc t th xj thuc v nhm th i

vi quan h hm cho bi.

C - l vc t trng tm v r l thng s rng ca hm. Vc t X ph thuc

mt vi nhm vi bc khc nhau c gi tr t 0 n 1 (tng mc ph thuc ca mt

vc t X vo cc tt c cc trng tm bng 1).

= 1=1


Tng hp cc mc ph thuc, ta c ma n ph thuc u . Cc h s ca ma

trn ny cho bit khong cch t cc mu d liu n tng nhm, h s ph thuc

cng ln th khong cch gia trng tm v mu d liu cng gn nhau.

Cc trng tm c tm kim trn c s ti u ha hm chi ph. Hm ny c

nh ngha bi:

trong : d l khong cch Elt t trng tm Ci n vc t Xj

dkj l khong cch Elt t trng tm Ck n vc t Xj

Thut ton FCM c thc hin theo cc bc sau:

- u vo ma trn u c th khi to ngu nhin vi cc gi tr t 0 n 1;

- Tm K trng tm nhm m Cj s dng cng thc nh trn;

- Tm gi tr ca hm E. u E t ngng t trc hoc nu E khng c

ci tin so vi bc trc th kt thc qu trnh lp, ngc li thc hin bc

k tip;

- Tnh ton bc t do mi ca ma trn u s dng cc cng thc trn v v

ff

E II ci ~X1 II2

ta c th s dng

(4.1)1

bc 2.


Bc tnh lp ny c thc hin nhiu ln. chnh xc ca li gii c xc

nh bng cch la chn trng tm ca nhm t gi tr t do ca ma trn u . Cc

trng tm ny tp trung xung quanh ni c nhiu im d liu nht.

V d hot ng ca thut ton n c trnh by trn hnh 4.1 vi 3 trng tm

c khi to trng ti mt im. Sau khong 20 vng lp, cc trng tm dch

chuyn v cc trung im ca vng tp trung d liu v hi t ti .

(* Label Data

Clear Traj.

MF Plot

2- Fuzzy -Mpanc

File Edit V iew Insert Tools Desktop W indow Help

A A B I mm a | \ \ \ ^ T go -Hi

Close

Hnh 4.1: Qu trnh dch chuyn ca cc trng tm t v tr ngu nhin ban u v cc

vng s liu

4.5 ng dng thut ton v chy th mng

4.5l X l s liu thu thp

Trc khi d liu a vo phn loi, chng ta phi x l s b gip cho

gii quyt kt qu phn loi c tt hn. Tin x l c th gip lm gim kch

thc ca vc t u vo bng cch loi b nhng ngy ph ti b ct do sa cha

hoc iu .


Theo cc nghin cu trc y [1,2,4,9] vic phn loi th ph ti trong

nm phn ln da vo phng php ngy trong tun, biu ph ti ngy lm vic

ny thng khc vi ngy ngh cui tun. M hnh ny thng phn bit cho cc

nhm ngy lm vic t Th Hai cho n Th Su, v nhm ngy ngh cui tun v

l tt. Yu im ca phng php ny l cc ngy ngh cui tun v l tt thng

cho kt qu d bo c chnh xc kh thp, thnh thong cc ngy lm vic trc

Th by v Ch ht b nh hng bi cc ngy ngh ny. Vi cch phn loi ny

cng khng hon ton ng cho tt c cc vng. Vic phn loi cng cn da vo

c th iu kin, thi quen, tp qun s dng in ca tng a phng.

Vi c th th ph ti ca hai nm 2004 v 2005 ti Sc Trng vic p

dng phng php phn nhm theo ngy trong tun l khng hiu qu v BPT cc

ngy lm vic v ngy ngh hu nh khng thay i nhiu, gy kh khn trong vic

phn nhm. Mt trong nhng cch phn loi c th p dng cho h thng in t c

s thay i nhiu ong tun l m hnh th trong thng lnh hot.

452 Phn nhm biu ph ti:

Chn mng bao gm:

S u vo l c nh, ph thuc vo s nhn t s dng: ong bi ton phn

loi kiu ngy ta s dng 24 gi tr (ng vi 24 gi trn th ph ti), do s u

ra l 24. s n ron u ra bng s nhm cc kiu ngy khc nhau m ta cn phn

bit.

Cch thc phn nhm nh sau: Cc ngy cng th trong mt thng ca hai

nm c a vo mng tm trng tm cch thc tm ng tm theo tiu ch th t

u tin:

1. Cc ngy trong thng chia lm 4 nhm: t mng 1 n mng 7, t

mng 8 n 15, t 16 n 23, t 24 n cui thng.

2. Cc ngy ong thng chia lm 3 nhm: t mng ln mng 10, t 11

n 20, t 21 n cui thng.


3. Cc ngy ong thng chia lm 2 nhm: tng mng 1 n ngy 15,

tng ngy 16 n cui thng.

4. Cc ngy trong thng c dng th ph ti tng ng nhau v c

th xp chung trong 1 nhm.

Tm trng tm theo cch chia: Cc phn t thuc cng mt nhm ch t

[1 ..10], [11..20], [21..31] cc trng tm ca nhm s l i din cho nhm nu

ngy cn d bo ri vo nhm ca ngy no s ly trng tm lm th ph ti

mu.

Chn s liu thng 07 nm 2004 v 2005

2004_________________ ______ Thng 7 2005_________________ ______ Thng 7c Hai Ba T m Su By

1 2 34 5 6 7 8 9 1011 12 13 14 15 16 1718 19 20 21 22 23 2425 26 27 28 29 30

c Hai Ba T m Su By1 2

3 4 5 6 7 8 910 11 12 13 14 15 1617 18 19 20 21 22 2324 25 26 27 28 29 30

Kt qu phn nhm ngy th 6 thng 7 bao gm cc ngy 2,9,16,23,30,1,8,15,22,29

theo th t t l-> 10 trc khi a vo phn nhm vi:

> u chia lm 2 nhm:

Vi center l trng tm c ma trn 2x24: Vi hai trng tm (mi hng l mt

trng tm)

hm th nht bao gm cc ngy: 9,23,30,1,29 vi 1 trng tm lm i in

hm th hai bao gm cc ngy: 2,16,8,15,22 vi 1 trng tm lm i in


11 File Edit Debug Desktop Window Help

D c Jt % w H I f Current Directory: C: 'Program FilesyMATLAB704\wark i l j

c e n t e r = -1

C o lum ns 1 t h r o u g h 15

0 .04 0 .0 2 6 5 0 .0 4 8 2 . 24 5 0 057 0 . 3 1 5

0 .0 9 4 4 0 .0 8 1 0

0 . 20 93 Q .181 6

D.2 5 2 1 .2 4 4 7

0 . 321 Q .2 719

0 .4 8 3 5 .780 .3 9 5 3 0 .5 9 4 3

0 . S3 8 8 Q.5 5 66

0 .3 3 3 2 0 .3 3 1 0 .2 3 6 6 0 .2 0 8 5

C o lum ns 1 t h r o u g h 24

. 9 0 H 0 81210 0 .7 2 4 0 0 .B 15 0 . 8 3 2 0 .6 0 5

0 .9 4 0 8 0 .9 5 3 6

. 85 92 0 .8 9 4 2

.J457 0 .8 7 2 2

.3 8 2 3 0 . 5 071

0 .1 7 94 0 . 0 64 9 0 .2 8 1 1 0 .1 3 1

u =

.4 98 9 0 .5 3 1 4 0 .1 8 93 D.5 0 1 1 0 .4 8 6 0 .8 1 0 7

0 .8 7 9 3 0 .1 2 0 7

.8 3 4 8 0 . 152

0 . S 8 9 1

0 .3 1 0 90 . 391 0 .6 0 3 9

.2 0 0 3 0 .2 2 4 4 0 .7 9 9 7 0 .7 7 5

. 51&1 D.4 2 3 3

nhom =

2 4 5 6 10

nhom =

1 3 7 8 9

u chia lm 3 nhm

File Edt PtlHig 0#tQ p Window Hlp

t % * - - K Of CTwlCwoc1y. Trap m i j jA * =

c o lu m tn i icQUth S

0 .0 4 4 9 O .fttST G.OiOfl 0 .0 8 6 9 6 .0 4 S 0 . 491 0 - J l S i 0 . 4 ? O .S iS l 0 .M H 0 .1 * 5 1 0 -S 1 1 t . n t l0 .0 2 * 9 n .0514 0 .0 1 1 4 O .0 7 o . i e a ? 0 . S 9 0 .2 4 5 2 0.3 G.Q103 0 .7 5 5 1 0 ,3 9 3 0 0 .1 8 3 ? O-0S330 .7 9 2 0 .6 5 9 ? 0 . 5 ? 0 .9 3 9 3 0 12 0 . 9373 0 .5 1 2 1 a . 3262 0 .1 7 0 30 ,0 4 5 9 0 .727 0 .f i2 ? a 0 . S>S2i D.0557 0 .7 4 0 4 0 .3 1 9 0 0 .1 7 4 3 0 ,0 7 1 ?

a

0.2 5 4 4 O .3 5 0 0 .1 6 0 0 0.D.7 0 .70 a . *581 0 .1 3 9 9 O . n 0 .1 1 1 2 0 .4 3 3 20 . 0 5 l 0 ,2 1 7 3 0 .S 2 2 1 O.04T8 0.01ST 0 .1 7 2 0 0.1.344 O.KT7* 0 .7 2 0 0 0 , 0 0 3.S405 0 .12 S 0.31SG 0 . H i s 0.2119 0 3691 O .b S iS 0 .1 1 1 1 0.1B8 0,2862

* i 6 u>nlwn -

ft

n-lin =

I 1

* I I .JH T ,

Vi center l trng tm c ma n 3x24: vi ba trng tm (mi hng l mt

trng tm)

hm th nht bao gm cc ngy: 23,30,1,29

hm th hai bao gm cc ngy: 16,15,22


hm th ba bao gm cc ngy: 2,9,8

> u chia lm 4 nhm- MA71AB 377

Pile Kett Obq 0*5* top Window Mflp

D w f tULHMKHMbnk l l J B

...... ............. d

Colum ns l th ro u g h 24

0 ,9 0 4 1 0 ,8 1 3 3 D.7555 0 .9 0 4 2 0.0094 0 .7 0 0 6 0 .4 7 0 .1 9 2 0 0.Q3?O.B20? 0.B52 o . f i i n 0 .9 8 8 0 O.S7S> 0 ?BS6 0.414 0 .2 0 4 3 0 .0 9 3 10 .9 9 6 1 . 616 9 0 .-d 2 B .m & s t.4 3 f il O.OSU a . 11 48 n 0-T40 .7 5 0 2 0 . 6030 0.5 4 3 2 0 . 9264 .8Q 0 . STlO o . ta 0.334'? 0 .1 7 0 6

l

0,534 o . m s 0 ,* i2 IXTJ< O.OO 0-194 O-IS 0-093 9 . Ho.it 0.4516 0.0900 0.13? 0,001? 0.1639 Q.311 o . r m

0.0977 o .o s n 0.0508 0.0303 O-Cne 0.99*7 0 .0 W 0.0440 0 .0 iee 0*15 ?O.ISSS 0,1420 0.3X-J-? o .o s e s 0.CH 3 0 . 0 1 0 0 ,0 1 7 7 0 ,* 7 S o,S X i 0 .2 0 9 2

nJn -

4 5 10

t. =

3 7

SlttCO -

8 9

1 1 st*n P

Vi center l trng tm c ma trn 4x24: vi bn trng tm (mi hng l mt

trng tm)

hm th nht bao gm cc ngy: 9,23,30,29

hm th hai bao gm cc ngy: 2,16,8

hm th ba bao gm cc ngy: 1

hm th t bao gm cc ngy: 15,22

Bng 4.1 Kt qu phn nhm th su thng 7:

Th su: 2,9,16,23,30,1,8,15,22,29

2 nhm:

[1..15][16..30]

- 9,23,30,1,29

- 2,16,8,15,22

3 nhm:

[1..10][11..20][21..30]

- 23,30,1,29

- 16,15,22

4 nhm:

[1..7][8..15][16..21][22..30]

- 9,23,30,29

- 2,16,8


- 2,9,8 - 1

- 15,22

Phn tch:

- Trng hp 2 nhm: Vi kt qu hai nhm ta khng th chn c s nhm

nh mong mun vi nhm th nht bao gm cc ngy t 9,23,30,1,29 nhm

th hai bao gm 2,16,8,15,22.

- Trng hp 3 nhm: C th chia nhm th nht bao gm cc ngy

23,30,1,29 s i din cho cc ngy t [21...30], nhm th hai bao gm cc

ngy 16,15,22 s i in cho cc ngy t [11...20], nhm th ba c cc

ngy 2,9,8 s i din cho cc ngy t [1..10]. C th nhn thy vi cch chia

ny cc ngy cng kiu u c xp vo mt nhm mong mun, goi tr

ngy 1 ca nhm th nht c xp vo cc nhm ngy [21.. .30] v ngy 22

ca nhm th hai c xp vo cc nhm ngy [11 ..20], guyn nhn c th

do thi tit hoc do c s kin nh hng n ch tiu th in v cung

cp in.

- Trng hp 4 nhm: Vi kt qu phn loi bn nhm ta khng th chn

c s nhm nh mong mun vi nhm 1 bao gm cc ngy t 9,23,30,29

nhm th hai bao gm 2,16,8 nhm th ba ch c 1 ngy nhm th 4 bao

gm hai ngy 15,22.

h vy vi cch chia 3 nhm l ph hp nht v t c mc tiu nh yu cu.

Bng 4.2 Kt qu phn nhm ngy th by thng 7:

Th by: 10 17 24 9 16 23 30

2 nhm:[1..15][16..30]

- 17,24,9- 10,16,23,30

3 nhm:[1..10][11..20][21..30]

- 17,24,9- 30- 10,16,23

4 nhm:[1..7][8..15][16..21][22..30]

- 16- 17,24- 23,30- 10,9


Vi cch chia n ta c th chn cch chia 4 nhm chn 3: nhm 1 bao gm

hai ngy 17,24 s i din cho cc ngy t [11..20], nhm 2 bao gm hai ngy

23,30 s i din cho cc ngy t [21..30], nhm 3 bao gm hai ngy 10,9 s i

din cho cc ngy t [1..10],

Bng 4.3 Kt qu phn nhm ch nht thng 7:

Ch nht: 4 11 25 10 17 24 31

2 nhm:[1..15][16..30]

- 10,31- 4,11, 25,17, 24

3 nhm:[1..10][11..20][21..30]

- 4,11,24- 25, 17- 10,31

4 nhm:[1..7][8..15][16..21][22..30]

- 4,11- 10,31- 25, 17- 24

Vi cch chia trn c th chn cch chia 2 nhm chn 1: 1 nhm gm cc

ngy 4,11, 25,17, 24 s i din cho tt c cc ngy [1..30] trong th.

Bng 4.4 Kt qu phn nhm th hai thng 7:

Th hai: 5 12 19 4 11 18 25

2 nhm:[1..15][16..30]

- 12, 19,4- 5 ,11,18,25

3 nhm:[1..10][11..20][21..30]

- 12,4- 19,11- 5 ,18, 25

4 nhm:[1..7][8..15][16..21][22..30]

- 12,4- 11- 5,25- 19, 18

C th chn cch chia 3 nhm chn 2: nhm 1 bao gm hai ngy 12, 4 s i

din cho cc ngy t [1..15], nhm 2 bao gm hai ngy 5,18,25 s i din cho cc

ngy t [16..30].


Bng 4.5: Kt qu phn nhm cho c hai nm 2004, 2005

xThng

Th \1 2 3 4 5 6 7 8 9 10 11 12

c 3 2 2 3 3 1 1 2 2 3 2 1Hai 2 2 2 2 2 2 2 3 1 2 1 1

Ba 1 1 2 1 1 2 2 2 2 2 2 2

T 1 2 2 2 2 2 2 2 2 2 2 1

m 1 2 2 2 2 2 2 2 2 2 1 1

Su 2 1 2 3 2 2 3 3 1 2 2 2

By 1 2 2 2 1 2 3 1 1 1 1 1

h vy: Ty thuc vo kt qu ca mi ln phn nhm m s nhm c

chn c th l 1 nhm, 2 nhm, 3 nhm cho mt th. d bo hnh dng ph ti

cho mt ngy cc thng tin cn thit l th, ngy v thng.

4.6 Xy dng giao din d bo hnh dng biu ph ti:

Cc nhm sau khi c phn loi theo tiu ch th ong thng. Trng tm ca

mi nhm c lu li thnh c s d liu phc v cng tc d bo hnh dng biu

ph ti. Chng trnh d bo biu ph ti c xy dng n phn mm

Matlab, d bo biu ph ti mt ngy ta cn xc nh cc thng tin v Thng

v Th ca ngy cn d bo, hai thng tin ny l c s cho vic la chn cc nhm

trong th ca thng cn d bo, kt hp vi yu t gy cn d bo s cho ra biu

ph ti ngy cn d bo.

Hnh 4.2: S khi d bo hnh dng th ph ti


V d d bo hnh dng BPT ngy 1 thng 1 nm 2006: Ta s chn ngy

v thng chng trnh s t ng cp nht th v hin th biu ph ti nh sau:

th bn tri hin th cc nhm ca thng 1 ngy ch nht, s c 3 nhm. Kt hp

vi yu t ngy s cho ta hnh dng biu ph ti. th bn phi, v ngy l ngy

1 nn chng trnh s cho ta hnh dng biu ph ti ca nhm 1. Chng trnh

tm trng tm c trnh by phn ph lc I.

Kt lun:

Mng Kohonen vi thut ton tm trng tm FCM cho kt qu phn nhm nhanh

do c th th nghim vi nhiu cc phn loi khc nhau, lun xp cc i

tng ging nhau vo cng mt nhm.

Vi cch phn loi ny mt mt c th tm ra cc du hiu ging nhau trong mt

th v xp chng vo mt nhm, mt khc vi cch phn loi ny cc gi tr ph

ti ca nhng ngy b ct ti hoc iu u b tch ra khi nhm do s loi

b c nhng ngy ph ti khng bnh thng.


Khc vi cc thnh ph khc nh H i hay TP H Ch Minh ph ti tng cao

cc ngy lm vic v st gim ngy ngh do c th chia lm ba nhm

ong tun (cc ngy lm vic, th by v ch nht), m hnh trn c gi l

m hnh ngy ong tun. Tuy nhin, ph ti cc vng nng nghip nh Sc

Trng khng tun theo quy lut , yu t nh hng th ph ti l theo thi

v, thi quen sinh hot v iu kin thi tit do s dng phng php phn

loi theo th trong thng lnh hot l gii php hp l nht v m bo chnh

xc nht nh.

h vy nhn thy rng i vi tng vng tng a phng s phi xy dng

m hnh khc nhau ph hp vi tng a phng c th, ta khng th a mt

m hnh d bo thnh cng vng ny s dng cho vng khc.


CHNG 5

XC NH CC THNG S U VO CHO MNG NHIU LP MLP

Trong lun vn ny, mng MLP (Multi Layer Perceptron) c s dng

tnh c lng gi tri cng sut cc i v cng sut cc tiu ca ngy hm sau da

trn cc thng s v cng sut cng nh nhit ca cc ngy trc . Mng MLP

ni ring v MNR ni chung c c trng bi cc thut ton hc - cc thut

ton cho php xc nh cc thng s mng ti u cho mt b s liu mu cho trc

no . Qu trnh hun luyn MNR nhn to c th c chia thnh: Hc c gim

st v hc khng gim st. Mng nh x c trng t t chc Kononen l loi mng

hc khng gim st, c dng phn loi biu ph ti chng 4, v trong

qu trnh phn loi ta khng nh r u ra mong mun cho mi biu u vo, v

khi bit c hnh dng biu ph ti ngy cn d bo th vic d bo c

cng sut cc i v cng sut cc tiu li cng quan trng hn na. i vi vn

d bo ph ti nh v y, khi ta bit r u ra (ph ti nh v ph ti y) ca

mi thng s u vo (d liu thi tit, biu ph ti trong qu kh v cc d liu

khc) ca cc mu hc, th cn s dng MNR vi qu trnh hun luyn c gim st.

MNR MLP vi k thut hun luyn lan truyn ngc sai s trong qu trnh hc

(Back - propagation Neural Network) s c dng gii quyt bi ton d bo

ph ti nh, ph ti y ca biu ph ti.

Chng 5 ny s trnh by cch chn la cc thng s u vo hun luyn

mng bng phng php phn tch tng quan gia hai yu t, mng MLP, l

thuyt thut ton L-M, nh by cu trc, v phng thc hun luyn mng.

5l La chn cc thng s u vo phc v qu trnh hun luyn mng n ronTheo cc nghin cu c thc hin [1,7,16] mt ong nhng mc tiu

trong vic la chn lm thng s u vo trong qu trnh hun luyn mng n ron l


nhit max, Tmin, Taver), m, tc gi, biu ph ti trong qu kh (1

gi trc, 1 ngy trc, 2 ngy trc, 7 ngy trc..)... s l cc thng s u vo

phc v qu trnh hun luyn M R. Tuy nhin hu nh cc nghin cu ny cha

ch ra c ti sao li s dng cc thng s ny phc v qu trnh hun luyn v s

u vo cho mng bao nhiu l hp l.

Trong lun vn ny vi s liu thu thp c biu ph ti v nhit Tmax

Tmin trong ba nm ong s ch s liu ca hai nm u phc v qu trnh hun

luyn mng v mt nm cui dng chy th mng. Lun vn s da vo mi

tng quan ca biu ph ti trong qu kh, phn tch tng quan gia cng sut

cc i v cng sut cc tiu. S tng quan ny l c s la chn cc thng s

u vo phc v qu trnh hun luyn mng. Ring yu t thi tit c mi quan h

phi tuyn vi ph ti, do s khng xt mi tng quan gia thi tit v ph ti,

yu t thi tit s kt hp vi cc u vo ph ti hnh thnh cc m hnh mng

khc nhau.

5.1l Phn tch tng quan:Mt trong nhng mc tiu nghin cu ph ti v khoa hc ni chung l tm ra

mi nhng mi tng quan gia cc yu t ph thuc ln nhau v qua c th tin

lng mt yu t ph thuc t cc yu t c lp. Mi tng quan y bao gm

cc c im nh mc tng quan.

Chng hn tm mi lin h gia Cng sut Pmax v cng sut Pmin c

ngha l tm mi tng quan gia hai bin ny ra sao v c th s dng Pmax

tin lng Pmin cho mt ngy hay khng. Trong mi lin h ny, chng ta xc nh

Pmin l bin ph thuc v Pmax l bin c lp. Vy nu gi X l bin Pmax v y l

bin Pmin, chng ta tm hiu mi tng quan gia X v y, h s tng quan cng

cao mi quan h gia X v y cng ln v ngc li.

Gi X vyi l hai bin quan st c. Gi s ta c n i tng th i=l,2,3.. .n.

Gi X v l hai s trung bnh ca bin quan st c; S 2X v s 2y ln lc l

phng sai ca hai bin, c nh ngha nh sau:


Hip phng sai:

1 nC O v(jC ,y ) = - = - r 2 , ( j C ( - * K > / - )

n 1 (= 1

H s tng quan:

c o v f o y ) _ cov(x,y) yjvax(x).vai(y) sx x s y

Cng thc trn cn c bit n nh l h s Pearson (Pearsons correlation

coeffcient) ngh nhn cng hin ca nh thng k hc ni ting Karl Pearson,

ngi u tin pht trin l thuyt tng quan vo u th k 20.

i vi X, y nh trn hnh (a) mi lin h ca X v y hon ton xc nh v

tuyn tnh; c ngha l cho bt c gi tr no ca X chng ta u c th xc nh

c gi tr ca y th ta s c r=l.

Kh mi lin h gia X v y hnh (b) l o ngc tc X tng th y gim kh

gi tr ca r l m.

V kh hai bin X v y l ton ton c lp hay nh trn hnh (c) gi tr c l

hng s v khng ph thuc gi tr ca X kh r=0

I----------1----------1----------1----------1----------1----------1

2 4 s s ID 12 1+

(a) (b) (c)


Mi lin h gia X v y: (a) r=l, (b) r= -1, (c)=0 (c lp).

Trong thc t khoa hc thc nghim, t khi no chng ta c nhng mi lin h

xc nh nh va trnh by. Cc mi lin h gia X v y thng dao ng cao hn -

1 v thp hn 1.

5l 2 Tm h s tng quan gia cng sut vi cng xut trong qu khKhi xy dng bt k m hnh no th vic m hnh hot ng c tt hay khng

ph thuc rt ln vo mi quan h u vo v u ra, bn cnh ty thuc vo

tng bi ton m ta phi la chn cc thng s u vo khc nhau. Trong hm

tng quan l mt thc o la chn thng s u vo cho m hnh.

Vi s liu ph ti v nhit hai nm 2004 - 2005 cc thng s u ra cn

xc nh l cng sut cc i v cng sut cc tiu, chng ta s xem xt mi tng

quan cng sut cc i ca mt ngy vi cc ngy trc .

t:Pmax(d), Pmin(d)\ L cng sut ph ti cao nht, thp nht trong ngy d

Pmax(d-x), Pmn(d-x): L cng sut ph ti cao nht v thp nht cch ngy trc X

ngy (x=l, 2...7, 14,21,28)

Xt cc mi tng quan gia Pmaxd vi 20 yu t nh hng khc:

1. Pmax(d), Pmax(d-l): Cng sut cc i ngy hin ti vi cng sut cc i

ngy hm trc

2. Pmax(d), Pmax(d-2): Cng sut cc i ngy hin ti vi cng sut cc i

cch hai ngy

3. ...


cch by ngy(l tun)


cch 14 ngy (2 tun)

56Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------


cch 21 ngy (3 tun)

10.Pmax(d), Pmax(d-28): Cng sut cc i ngy hin ti vi cng sut cc i

cch 28 ngy (4 tun)

11 .Pmax(d), Pmn(d-l): Cng sut cc i ngy hin ti vi cng sut cc tiu

gy hm trc

12. Pmax(d), Pmn(d-2): Cng sut cc i ngy hin ti vi cng sut cc tiu

gy hm trc


cch by ngy(l tun).


cch 14 ngy (2 tun)


cch 21 ngy (3 tun)


cch 28 ngy (4 tun)

5.13 Mt s kt qu thu c sau khi phn tch tng quan

Hnh 5.1 Hnh 5.2


Hnh 5.1: th ph thuc ca Pmax(d) vo Pmax(d-l) vi h s tng quan r=0,81

Hnh 5.2: th ph thuc ca Pmax(d) vo Pmax(d-7) vi h s tng quan r=0,61

Tng t vi Pmin: Ta cng xt nh hng ca 20 yu t n Pmn kt qu xt tng quan c trnh by hnh bn di.

MW MW

Hnh 5.3 Hnh 5.4

Hnh 5.3: th ph thuc ca Pmin(d) vo Pmin(d-l) vi h s tng quan r=0,93

Hnh 5.4: th ph thuc ca Pmin(d) vo Pmin(d-7) vi h s tng quan r=0,81

Bng 5.1 Kt qu phn tch tng quan gia Pmax v 20 yu t

gy Pmaxd, Pmaxd-1 Pmaxd, Pmaxd-2 Pmaxd, Pmaxd-3 Pmaxd, Pmaxd-4

r 0,8058 0,7461 0,7023 0,6723

gy Pmaxd, Pmaxd-5 Pmaxd, Pmaxd-6 Pmaxd, Pmaxd-7 Pmaxd, Pmaxd-14

r 0,652 0,6166 0,6149 0,5164

gy Pmaxd, Pmaxd-21 Pmaxd,Pmaxd-28 Pmaxd, Pmind-1 Pmaxd, Pmind-2

r 0,5108 0,4243 0,7776 0,7337

gy Pmaxd, Pmind-3 Pmaxd, Pmind-4 Pmaxd, Pmind-5 Pmaxd, Pmind-6

r 0,7078 0,6704 0,6496 0,6322

gy Pmaxd, Pmind-7 Pmaxd, Pmind-14 Pmaxd, Pmind-21 Pmaxd,Pmind-2 8

r 0,6226 0,5422 0,526 0,458

Bng 5.2 Kt qu phn tch tng quan gia Pmin v 20 yu t

gy Pmind, Pmind-1 Pmind, Pmind-2 Pmind, Pmind-3 Pmind, Pmind-4

r 0,9312 0,8966 0,8678 0,8495


gy Pmind, Pmind-5 Pmind, Pmind-6 Pmind, Pmind-7 Pmind, Pmind-14

r 0,8314 0,8183 0,8090 0,7569

gy Pmind, Pmind-21 Pmind,Pmind-28 Pmin, Pmax-1 Pmind, Pmaxd-2

r 0,7495 0,6689 0,7492 0,7122

gy Pmind, Pmaxd-3 Pmind, Pmaxd-4 Pmind, Pmaxd-5 Pmind, Pmaxd-6

r 0,6817 0,668 0,6536 0,6407

gy Pmind, Pmaxd-7 Pmind, Pmaxd-14 Pmind, Pmaxd-21 Pmind,Pmaxd-28

r 0,6321 0,5918 0,598 0,5491

.9

0.8

0.7

.6

0.5

0.4

.3

0.2

0.1

0 1 2 3 4 5 6 7 8 9 10 11Pmax-1 Pmax-2 Pmax-3 Pmax-4 Pmax-5 Pmax-6 Pmax-7 Pmax-14 Pmax-21 Pmax-28

Hnh 5.5 th tng quan gia Pmax v cc Pmax trong qu kh

hn thy h s tng quan ca Pmax v cc ngy trong qu kh cng xa

cng gim, hng th h s tng quan gim nhanh Pmax(d-14), Pmax(d-21),

Pmax(d-28). Do c th chn Pmax(d-l) n Pmax(d-7) lm thng s u vo

d bo Pmaxd.

th biu din mi quan h Pmax v cc yu t u vo-------- 1--------1--------1--------1--------1-------- 1--------1--------1--------1

a a


1 2 3 4 5 6 7 8 9 10 11

Pmin-1 Pmin-2 Pmin-3 Pmin-4 Pmin-5 Pmin-6 Pmin-7 Pmin-14 Pmin-21 Pmin-28

Hnh 5.6 th tng quan gia Pmax v cc Pmin trong qu kh

H s tng quan ca Pmax v cc Pmn trong qu kh cng xa cng gim,

hng th h s tng quan gim nhanh Pmn(d-14), Pmn(d-21), Pmin(d-28).

Do c th chn Pmin(d-l) n Pmn(d-7) lm thng s u vo d bo

Pmaxd.

1

.9

0.8

0.7

0.6

0.5

0.4

0 3

0.2

0.1

0 1 2 3 4 5 6 7 8 3 10 11

Pmin-1 Pmin-2 Pmin-3 Pmin-4 Pmin-5 Pmin-6 Pmin-7 Pmin-14 Pmin-21 Pmin-28

Hnh 5.7 th tng quan gia Pmn v cc Pmin trong qu kh

60Trng i hc Nng nghip H Ni - Lun vn thc s khoa hc-----------------------

th biu din mi quan h Pmin v cc yu t u vo~r~

I r ~--------------1-------------- 1--------------r

0 8 1------------------1------------------1----------------- 1------------------1----------------- 1------------------1------------------1----------------- 1------------------1----------------- r

9

0 5 -

0 4 -

0.3 -

0.2 -

0 1 -

0 1 2 3 4 5 6 7 0 9 10 11

Pmax-1 Prnax-2 Pmax-3 Pmax-4 Pmax-5 Prnax-6 Pmax-7 Ptnax-14 Pmax-21 Pmax-20

Hnh 5.8 th tng quan gia Pmn v cc Pmax ong qu kh

Tng t nh xt cc u vo d bo cho Pmax, chn thng s u vo cho

Pmin cng tng t nh vy.

Nhn xt: Qu vic tm h s tng quan ph ti cc i v cc tiu ca ngy

hin ti v cc ngy trc c th nhn ra rng h s tng quan s theo chu

Ng Dung Mang No Ron Nhan Tao Trong Du Bao Ngan

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