302 The Transactions of the Korean Institute of Power Electronics, Vol. 21, No. 4, August 2016

http://dx.doi.org/10.6113/TKPE.2016.21.4.302

ESS PCS

1, 1, , 2, 3

A PCS Control Strategy for Hybrid ESS

with Function of Emergency Power Supply

Sang-Jin Kim1, Min-Ho Kwon1, Se-Wan Choi, Seok-Min Paik2, and Mi-Sung Kim3

Abstract

This paper proposes a hybrid ESS that integrates an energy storage system (ESS) with an uninterruptible

power supply (UPS). The hybrid ESS has a demand management and emergency power supply function while

increasing the battery utilization of the UPS, which has just been used in a power failure. In addition to the

critical load, the proposed system augments the capacity of emergency generation using an additional load,

which has voltage and frequency-dependent characteristics to the grid side. The control algorithm of the

AC-DC converter and bidirectional DC-DC converter is proposed for demand management and emergency

power supply. Furthermore, seamless and autonomous transfer methods to alleviate the transient during mode

transfer are proposed. To validate the proposed control scheme, experimental results from a 5 kW prototype

are provided.

Key words: Hybrid ESS, ESS(Energy Storage System), UPS(Uninterruptible Power Supply), Seamless transfer

Paper number: TKPE-2016-21-4-4Print ISSN: 1229-2214 Online ISSN: 2288-6281

Corresponding author: schoi@seoultech.ac.kr, Dept. ofElectrical & Information Eng., Seoul Nat'l Univ. ofScience and TechnologyTel: +82-2-970-6542 Fax: +82-2-972-28661 Dept. of Electrical & Information Eng., Seoul Nat'l Univ.of Science and Technology2 Dept. Technology Research Institute KUKJE Electric Mfg.co., Ltd.3 Dept. EMC Research Institute Energy Industry Team,Korea Testing & Research Institute.Manuscript received Mar. 21, 2016; revised Apr. 1, 2016;accepted Jun. 2, 2016 2015 Fig. 1. Grid disturbances and UPS classes[1].

1.

ESS(Energy storage system)

. ESS

,

. , UPS(Uninterruptible power

supply)

,

. 1 UPS

[1]. Online UPS , ,

1 10

VFI(Voltage and frequency independent)

. Offline UPS ,

,

VFD(Voltage and

frequency dependent) .

Offline UPS VFD, Online UPS

ESS PCS 303

Fig. 2. Configuration of the conventional ESS and UPS. Fig. 3. Configuration of the proposed hybrid ESS.

Fig. 4. Circuit diagram of the proposed hybrid ESS.

VFI . 2

250kW ESS

UPS, VFI .

UPS

. ESS

,

.

ESS UPS

ESS . 3

ESS

. ESS UPS

PCS

.

250kW VFI 250kW VFD

. ESS

, VFD

.

5kW .

2. ESS

4 ESS

. ,

250kW AC-DC DC-AC, 500kW

DC-DC, , VFI, VFD,

.

[2] VFI

,

.

ESS

AC-DC DC-AC

3- [3]. 3-

NPC , 5

20kHz

T-type [4][5]. DC-DC

DC

.

2.1

5 4

. 5.(a)(c)

(Demand management mode)

, 5.(d) (Emergency power

supply mode) .

5.(a) AC-DC

DC-DC

304 The Transactions of the Korean Institute of Power Electronics, Vol. 21, No. 4, August 2016

(a) (b)

(c) (d)

Fig. 5. Operation mode of the proposed hybrid ESS. (a) Mode 1 (b) Mode 2 (c) Mode 3 (d) Mode 4.

(a)

(b)

Fig. 6. Control targets of PCSs depending on operation

mode. (a) Demand management mode.(Mode 1Mode 3)

(b) Emergency power supply mode. (Mode 4).

. VFD

VFI AC-DC

DC-AC .

.

5.(b)

, VFI

. DC-DC

DC-AC VFI

.

5.(c) 5.(b)

,

VFI

.

DC-DC AC-DC

VFD DC-AC

VFI . VFI, VFD,

.

5.(d)

.

DC-DC VFD,

VFI . SOC VFI

VFD ,

AC-DC VFD

. DC-DC

DC-AC VFI .

2.2

6 ESS

.

6.(a)

, 6.(b)

.

6.(a) (Mode 1

Mode 3) VFD

3

AC-DC . AC-DC

DC DC

. DC-DC

(CC-CV)

DC-AC DC VFI

3

.

.

6.(b)

(Mode 4) AC-DC

VFD .

DC-DC DC

DC-AC

ESS PCS 305

Fig. 7. Control block diagram of the proposed DC-DC

converter for autonomous and seamless mode change.

VFI

.

2.3

ESS DC

AC-DC VFD

.

(clearing

time)

DC-DC DC

. DC

.

ESS AC-DC DC-DC

.

2.3.1 DC-DC

7 DC-DC

[6][7]

.

.

,

(Anti-windup)[8] .

3 DC DC

.

(1)

(2)

AC-DC DC

5% ,

.

DC AC-DC

.

(3)

PI1 ( ) PI3

( ) .

SOC ( )

PI2 ( )

.

.

(4)

.

(5)

. SOC

PI2

.

.

(6)

PI3

( ) .

(7)

PI3 .

(8)

.

(4)

.

(9)

306 The Transactions of the Korean Institute of Power Electronics, Vol. 21, No. 4, August 2016

Fig. 8. Control block diagram of the proposed AC-DC converter for seamless mode change.

PI1 .

(10)

DC

.

AC-DC

DC DC

.

2.3.2 AC-DC

8 ESS 3

[9][10] AC-DC

[11]-[13] .

DC

,

.

LCL AC-DC

DC

.

( ) ( ) ( )

.

(11)

(12)

(13)

,

. (13)

dq .

(14)

() ,

( ) 0

. (14)

() (

)

.

(15)

(15) 8

DC

.

() (

)

.

(16)

(17)

. (16) (17)

.

.

(18)

(19)

AC-DC

VFD

.

ESS PCS 307

(a) (b) (c)

Fig. 9. Simulation waveforms of the operation modes. (a) Mode 1, (b) Mode 2, (c) Mode 3.

. DC

VFD

, VFD

.

3.

220V, DC

450V, 280V 9.(a)

(c) 5.(a) 5.(c)

. 9.(a)

Mode 1

. 10A ( )

VFI( ) VFD( ) 2.5kW

. 9.(b)

DC-DC

Mode 2 . 10A

VFI 5kW DC-DC

2.5kW . VFD

2.5kW . 9.(c)

35A

Mode 3 . VFI,

VFD 5kW, 2.5kW

. 10 5.(d)

.

10.(a) Mode 1 Mode 4

, DC-DC

AC-DC DC-DC

.

VFI () ( )

.

( ) 0 ,

DC ( )

. clearing time AC-DC

,

DC-DC DC

DC 430V . DC-DC

VFD VFI

VFD ( )

. 10.(b) Mode 3

Mode 4 , DC-DC

AC-DC DC-DC

. 10.(a)

AC-DC VFD

DC-DC DC 470V

.

4.

11 ESS 5kW

308 The Transactions of the Korean Institute of Power Electronics, Vol. 21, No. 4, August 2016

(a) (b)

Fig. 10. Simulation waveforms of the mode change. (a) Mode transition from Mode 1 to Mode 4. (b) Mode transition

from Mode 3 to Mode 4.

Fig. 11. Prototype of the proposed hybrid ESS.

Symbol Value Unit

P 5 kW

Vg 220 Vac

Vb 210310 Vdc

Vdc,P+Vdc,N 430470 Vdc

Lg 560 H

Lf 540 H

Cf 16 F

Li 540 H

Ci 16 F

L1 , L2 1.17 mH

Co 165 F

TABLE

SPECIFICATION OF THE PROTOTYPE

.

DSP TMS320F28377D CPLD 3-

AC-DC 3- DC-AC,

DC-DC . 3 PCS

28 PWM CPLD

.

ESS 1 .

1216 5

. 12 Mode 1

DC-DC AC-DC

DC-DC .

, ,

,

. 13 DC-DC Mode 2

ESS PCS 309

(a)

(b)

Fig. 12. Experimental waveforms of the AC-DC

converter and the DC-DC converter during charging the

battery. (a) AC-DC converter. (b) DC-DC converter.

(a)

(b)

Fig. 13. Experimental waveforms of the AC-DC

converter and the DC-DC converter during discharging

the battery. (a) AC-DC converter. (b) DC-DC converter.

Fig. 14. Experimental waveforms of the DC-AC inverter.(a)

(b) (c)

Fig. 15. Experimental waveforms of the battery current

direction change. (a) the waveform of the current

direction change from charging to discharging. (b)

charging mode, (c) discharging mode.

AC-DC DC-DC

. 14 DC-AC 3

. 15.(a)

DC-DC

. 15.(b)

15.(c)

. 16.(a)

DC-DC

.

AC-DC 450V DC

DC-DC 430V

. 16.(b)

16.(a)

.

310 The Transactions of the Korean Institute of Power Electronics, Vol. 21, No. 4, August 2016

(a) (b)

Fig. 16. Experimental waveforms of the mode change. (a) Mode transition from Mode 1 to Mode 4. (b) Mode transition

from Mode 3 to Mode 4.

DC DC-DC 470V

. DC

AC-DC

VFD

. 16 AC-DC

DC-DC

.

4.

ESS UPS

ESS .

UPS

.

ESS ,

.

VFI VFD

. PSIM

5kW

.

2014

(KETEP)

.(No. 20142010102600)

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ESS PCS 311

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ESS PCS Abstract1. 2. ESS3. 4. References