Convertible Static Compensator.doc

7/28/2019 Convertible Static Compensator.doc

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NEW FACTS DEVICE: CONVERTIBLE STATIC

COMPENSATOR

Abstract:-

In these recent days power electronic based devices are in demand to

improve the performance of the power system. FACTS technology is one of the

leading technologies based on power electronics. In this paper we are going to

introduce new compensation device CONVERTIBLE STATIC

COMPENSATOR (CSC). Voltage, small signal & transient stability simulations

are conducted using the developed models of these configurations within the user

defined capability. The focus of studies is on finding which configuration of the

CSC provides the highest performance improvement from all stability points of

View. Modulation Controls are developed to improve inters area oscillationdamping. In general this paper focuses on how CSC helps to improve voltage,

small signal, transient stability margins of the system. The performance of the

individual devices resulting from CSC configurations and their capabilities in the

studied case is presented. The models used in this paper for various CSC

configurations are based on active and reactive components of the injected current

and the inserted voltage. These are implemented in the user defined controls,

which incorporate all user relevant dynamics limits and their ratings.


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Introduction:-

Alternating current transmission system incorporating power electronic

based & other static controllers to enhance controllability & increase power

transfer capabilities is known as Flexible AC Transmission System (FACTS).

Power system of today, by & large, are mechanically controlled .There is

widespread use of microelectronics, computers, high speed communications for

control & protection of present transmission system however when operating

signals are sent to the power circuits, where the final power control action istaken. The switching devices are mechanical and there is little high speed control.

Another problem with mechanical devices is that control cannot be initiated

frequently, because these mechanical devices tend to wear out very quickly

compared to static devices. In effect, from the point of view of both dynamic &

steady state operation, the system is really uncontrolled.

It is flexible, in the sense; power angle curve can be varied in the wide

range to control active & reactive power flow in the system. FACTS converters

can work as voltage sourced converter (VSC) &current sourced converter (CSC).

Benefits From Facts Technology:-

Control of power flow as ordered.

Increase the loading capability of lines to their thermal capabilities, including

short term &seasonal.

Increase the system security.

Provide greater flexibility in siting new generation.

Upgrade of lines.


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Reduce reactive power flow.

Reduce loop flows.

Increase utilization of lowest cost generation.

Main Facts Device:-

1. STATCOM.

2. SSSC.

3. UPFC.

4. IPFC.

1. STATCOM:-

line

C-+

Fig 1:- STATCOM

Definition:-

A static synchronous generator operated as a shunt connected static VAR

compensator whose capacitive or inductive o/p current can be controlledindependent of the system voltage.

STATCOM is based on voltage sourced converter & current source

converter. For the voltage source converter its ac o/p voltage is controlled such

that it is just right for the required reactive current flow for any bus voltage .DC

capacitor voltage is automatically adjusted as required to surve as a voltage source


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for the converter. STATCOM includes the possibility of an active power source

or storage on the dc side so that the injected current may include active power.

2. SSSC:-

Definition:-

A static synchronous generator operated without an external electric

energy source as a series compensator whose o/p voltage is in quadrature with &

controllable independently of the line current for the purpose of increasing or

decreasing the overall reactive voltage drop across the line & thereby controlling

the transmitted electric power.

C

-+

Fig 2:- SSSC

SSSC is like a STATCOM except that the o/p ac voltage is in series with

the line. It can also be based on voltage source converter & current source

converter .Usually the injected voltage in series would be quite small compared tothe line voltage & insulations to ground would be quite high. Without an extra

energy source, SSSC can only inject variable voltage, which is 90 degree lagging

or leading the current.

3. UPFC:-


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Definition:-

The combination of STATCOM & SSSC which are coupled via a

common dc link to allow bidirectional flow of real power between the series o/p

terminal of SSSC & the shunt o/p terminal of STATCOM & are controlled to

provide real & reactive series line compensation without an external energy

source.

This is complete controller for controlling active & reactive power control

through the line as well as for line voltage control.

D C L IN K

L I N E

S T A T C O M

S S S C

Fig 3:- UPFC

4. IPFC:-

Definition:-

A combination of two or more SSSC which are coupled through acommon dc link to facilitate bidirectional flow of real power between the ac

terminal of the SSSC & are controlled to provide independent reactive

compensations for the adjustment of real power flow in each line and maintain the

desired distribution of reactive power flow among the lines.


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The IPFC addresses the problem of compensating a number of

transmission lines at a given substation

C O N V E R T E R 1 C O N V E R T E R 2C O N V E R T E R n

C O N T R O L

. . . .

H V 1

H V 2

H V 3

.

Fig 4 :- IPFC

Introducing Convertible Static Converter

Definition:-Convertible Static Converter (CSC) is a combination of two converters,

two series & one shunt transformer.

This arrangement of the converter allows the STATCOM, SSSC, UPFC &

IPFC de-employed of the bus & lines (e.g. Marcy Cooper Corners & Marcy

New Scotland both is 345KV lines.)


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There are many possible combinations by using CSC according to

requirements .Some of combinations are given below:

S S S C 1

1 0 0 M V A

3 4 5 K V L IN E

S S S C 2

1 0 0 M V A

3 4 5 K V L IN E# 2

G 1 `

# 1

G 1 `

S T A TC O M 1 S T A T C O M 2

Fig. 5 :- Convertible Static Compensator

1 .100 MVA STATCOM;

2. Two 100 MVA STATCOMS;

3. 100MVA SSSC on line #1;4. 100MVA SSSC on line #2;

5. 100MVA SSSC on line #1 & 100MVA SSSC on line #2;

6. 100 MVA STATCOM & 100MVA SSSC on line #1;

7. 100 MVA STATCOM & 100MVA SSSC on line #2;

8. 100/100MVA UPFC on line #1;

9. 100/100MVA UPFC on line #2;

10. 100/100MVA IPFC on line #1 & #2;

These configurations are based on derivations of active and reactive

component of the injected current for shunt converter & the inserted voltage for

series converter. These implementations can be controlled fully by user under all

relevant conditions like dynamics, limits & ratings.


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The transformations of these components (active & reactive) to magnitude

& phase are instantaneously. The computed magnitude & phase defines the

controlled ac voltage source of the converter model which is inserted behind its

transformer reactance. Voltage, small signal & transient stability simulations are

conducted using the developed models of these configurations within the user

defined capability of the EPRIS power system analysis package.

DESCRIPTION OF EACH CONFIGURATION:-

1. 100 MVA STATCOM:-

S S S C 1

1 0 0 M V A

3 4 5 K V L IN E

S S S C 2

1 0 0 M V A

3 4 5 K V L IN E# 2

G 1 `

# 1

G 1 `

S T A T C O M 1 S T A TC O M 2

Fig 6 :-100 MVA STATCOM

In this CSC configuration, 100 MVA STATCOM is acting alone. It is

connected in shunt with bus bar 1 as shown in fig 6. Its function is to control

voltage.

2. TWO 100 MVA STATCOMS:-

S S S C 1

1 0 0 M V A

3 4 5 K V L I N E

S S S C 2

1 0 0 M V A

3 4 5 K V L I N E# 2

G 1 `

# 1

G 1 `



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Fig 7 :-TWO 100MVA STATCOMS

In this CSC configuration, two 100 MVA STATCOMs are acting alone.

Both 100 MVA STATCOMs are connected in shunt with bus bar1 as shown in fig

7.Here both converters functions to control voltage.

3.100 MVA SSSC ON LINE #1:-

S S S C 1

1 0 0 M V A

3 4 5 K V L I N E

S S S C 2

1 0 0 M V A

3 4 5 K V L I N E# 2

G 1 `

# 1

G 1 `

S T A TC O M 1 S T A TC O M 2

Fig 8 :-100MVA SSSC ON LINE #1

In this CSC configuration, 100 MVA SSSC on line#1 is acting alone. It is

connected in series with bus bar as shown in fig 8. Here converter functions tocontrol power.

4.100MVA SSSC ON LINE #2:-

S S S C 1

1 0 0 M V A

3 4 5 K V L I N E

S S S C 2

1 0 0 M V A

3 4 5 K V L I N E# 2

G 1 `

# 1

G 1 `

S T A T C O M 1 S T A T C O M 2


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Fig 9 :- 100MVA SSSC ON LINE #2

In this CSC configuration, 100 MVA SSSC on line #2 is acting alone. It is

connected in series with bus bar as shown in fig 9. Here the converter functions to

control power.

5. 100 MVA SSSC ON LINE #1 AND A 100 MVA SSSC

ON LINE #2:-

S S S C 1

1 0 0 M V A

3 4 5 K V L IN E

S S S C 21 0 0 M V A

3 4 5 K V L IN E# 2

G 1 `

# 1

G 1 `

S T A TC O M 1 S T A T C O M 2

Fig 10 :-100 MVA SSSC ON LINE #1 AND A 100 MVA SSSC ON LINE #2

In this CSC configuration, 100 MVA SSSC on line #1& 100MVA SSSC

on line #2 are acting alone. Both 100 MVA SSSCs are connected in series with

bus bar as shown in fig 10. Here converters functions to control power.

6.100 MVA STATCOM AND 100 MVA SSSC ON LINE

#1:-

S S S C 1

1 0 0 M V A

3 4 5 K V L IN E

S S S C 2

1 0 0 M V A

3 4 5 K V L IN E# 2

G 1 `

# 1

G 1 `

S T A T C O M 1 S T A T C O M 2


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Fig11 :-100 MVA STATCOM AND 100 MVA SSSC ON LINE #1

In this CSC configuration, 100 MVA SSSC & 100MVA STATCOM

acting alone.100MVA SSSC is connected in series and 100MVA STATCOM is

connected in shunt as shown in fig 11. In this case, both voltage and power can be

controlled.

7.100 MVA STATCOM AND 100 MVA SSSC ON LINE

#2:-

S S S C 1

1 0 0 M V A

3 4 5 K V L I N E

S S S C 2

1 0 0 M V A

3 4 5 K V L I N E# 2

G 1 `

# 1

G 1 `

S T A TC O M 1 S T A TC O M 2

Fig 12 :-100 MVA STATCOM AND 100 MVA SSSC ON LINE #2

In this CSC configuration, 100 MVA SSSC & 100MVA STATCOM

acting alone.100 MVA SSSC is connected in series and 100MVA STATCOM is

connected in shunt as shown in fig12. In this case, both voltage and power can be

controlled.

8. 100/100 MVA UPFC ON LINE #1:-

In this CSC configuration, 100 MVA SSSC is connected in series and

100MVA STATCOM is connected in shunt with common dc link to function as

UPFC. In this case, both converters controls voltage, real and reactive power

flow.

For this configuration refer the figure of configuration no. 6.


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9. 100/100 MVA UPFC ON LINE #2:-

In this configuration, 100 MVA SSSC is connected in series and 100MVA

STATCOM is connected in shunt with common dc link to function as UPFC. In

this case, both converters controls voltage controls real and reactive power flow.

For this configuration refer the figure of configuration no.7.

10.100/100 MVA IPFC ON LINE #1 AND #2:-

S S S C 1

1 0 0 M V A

3 4 5 K V L I N E

S S S C 2

1 0 0 M V A

3 4 5 K V L I N E# 2

G 1 `

# 1

G 1 `


Fig13 :-100/100 MVA IPFC ON LINE #1 AND #2

In this CSC configuration, both 100 MVA SSSCs are connected in series

with each line and are connected through a common dc link with each other. Here

the function of both the converters is to control real and reactive power flow in

both lines.

By using CSC the power system can be fully flexible & robust. The

relevant improvements are as follows:Voltage security increases.

Improve small signal stability.

Improve transient stability.

Effective oscillations damping.


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In general all CSC configurations improve the voltage stability margin of the

system.

CONCLUSION: -

Voltage, small signal & transient stability studies using appropriate static &dynamic models developed for various configurations of CSC. In general, all CSC

configurations improve the voltage stability margin of the system. Using the converter as

STATCOMs & UPFC line provides the maximum benefit in improving the voltage

stability margins for the considered power transfer directions & contingencies. When

operated as SSSC, UPFC or IPFC, the series converter control mode of inserting

maximum capacitive voltage provides the highest benefit. Similarly maximum current

injected by the shunt converter provides the largest voltage stability margins.


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