UPFC Based System Design For Power Injection At Line Bus

Table Of Contents

Abstract Objective Introduction UPFC Operation Block Diagram & Explanation Circuit Diagram & Explanation Simulation Model & Results Advantages Conclusion

Abstract

A power quality issue, especially, voltage problem is the vital concern in most distribution system today. A UPFC unit is connected to inject real & reactive power to meet the voltage betterment in transmission line.

In our work, we proposed the series-shunt combination, the UPFC is modified as one shunt and series transformer, a transformer is used in shunt from which a DC is extracted. In this paper, a UPFC control system that includes both the shunt converter and the series converter has been simulated. The model is analyzed using MATLAB 7.9 and the results are obtained.

Objective

The project explains the control and performance of UPFC intended for installation on the transmission line to control power flow.

This gives information about the UPFC based control scheme to mitigate the power quality utility in transmission line bus with linear load.

It is to transmit power with least power losses to distribution sector and to maintain the voltage stability.

Introduction

FACTS in the power systems not only enhances the dynamic performance, but also increases the stability of the power systems, enhances the controllability & increases its power transfer capability.

The controlling of the power flow and increasing the transmission capacity of the existing transmission lines are the two main objectives of FACTS technology.

Unified Power Flow Controller (UPFC), being one the member of the FACTS device thus emerged as one of the effective controllers for controlling and optimization of the power flow in the electrical power transmission systems. . The UPFC can provide simultaneous control of all basic power system parameters.

UNIFIED POWER FLOW CONTROLLER

A Unified Power Flow Controller (or UPFC) is an electrical device for providing fast-acting reactive power compensation on high-voltage electricity transmission networks. The UPFC is a versatile controller which can be used to control active and reactive power flows in a transmission line.

The series inverter is controlled to inject a symmetrical three phase voltage system of controllable magnitude and phase angle in series with the line to control active and reactive power flows on the transmission line. So, this inverter will exchange active and reactive power with the line.

The reactive power is electronically provided by the series inverter, and the active power is transmitted to the dc terminals. The shunt inverter is operated in such a way as to demand this dc terminal power (positive or negative) from the line keeping the voltage across the storage capacitor Vdc constant.

So, the net real power absorbed from the line by the UPFC is equal only to the losses of the two inverters and their transformers. The remaining capacity of the shunt inverter can be used to exchange reactive power with the line so to provide a voltage regulation at the connection point.

The UPFC consists of two voltage source converters; series and shunt converter, which are connected to each other with a common dc link. Series converter or Static Synchronous Series Compensator (SSSC) is used to add controlled voltage magnitude and phase angle in series with the line, while shunt converter or Static Synchronous Compensator (STATCOM) is used to provide reactive power to the ac system, beside that, it will provide the dc power required for both inverter. Each of the branches consists of a transformer and power electronic converter. These two voltage source converters shared a common dc capacitor.

The energy storing capacity of this dc capacitor is generally small. Therefore, active power drawn by the shunt converter should be equal to the active power generated by the series converter. The reactive power in the shunt or series converter can be chosen independently, giving greater flexibility to the power flow control

The UPFC can be used to control the flow of active and reactive power through the line and to control the amount of reactive power supplied to the line at the point of installation.

Block Diagram

5VPOWERSUPPLY

UPFC

(SERIES & SHUNT)

89C51

LOAD

Input 230 V/ AC

supply

Step down TFR

Step down TFR

TRANSFORMER

COUPLING

Input 230 V/ AC

supply

Working

The Input 230v,AC supply is stepped down using a step down TFR to 50v as our requirement.

This is passed on to the Transformer coupling and direct to the distribution load.

TFR coupling is used to couple the UPFC into the main Transmission line.

Microcontroller 89c51 is used for triggering pulse for UPFC to turn On.

The Input of the UPFC is only DC supply which is passed by the Rectifier.

The application of UPFC gives the better stability

Circuit Diagram

CIRCUIT DESCRIPTION

The power for the micro controller is derived from a step down transformer, Rectifier and Capacitor filter. Then regulated by 7805 regulator IC.

The power generator is taken as 12-0 transformer and a series of resistors 10 ohms are connected in both the lines to imitate the line bus.

To construct one shunt regulator and series regulator, a transformer is used in shunt from which a DC is extracted. Now the DC BUS voltage is switched through a transistor so that the line voltage gets more power from the series controller.

The pulse from the micro controller 89c51 is given from p2.0.The micro controller senses the output voltage by means of an ADC 0809 through port p1.0 to p1.7.

Through the internal program written in assembly language, the ON time of the pulses are varied so as to control the power flow in the load connected at the end of the line.

DEVELOPMENT OF THE SIMULINK MODEL

In this section, we present the development of the Simulink model for the multi-machine power system with and without the controller. It shows the simulation model of 3-generator, 5-bus system installed with one UPFC controller, i.e., places between Bus 2 & 3.The entire system modeled in Simulink is a closed loop feedback control system. The Simulink model is developed from the basic functions available in the Simulink library & from the various tool-boxes available.

Shunt 500 kV, 100 MVASeries 100 MVA,10% injection

1000 MW<------

IIV

197 MW<------

1277 MW------>

500 MW------>

690 MW------>

687 MW -27 Mvar ------>

230 kV

500 kV

UPFC SIMULATION

796 MW 15 Mvar

95 MW500 MW 1000 MW

589 MW

587 MW -27 Mvar 1279 MW

899 MW 28 Mvar

Power flows with UPFC(Pref=687MW, Qref=-27 Mvar)are shown in blue notes.

Phasors

powergui

Vdqref

Vdqref

VPQ Lines

V P QMeasurements

UPFC

UPFCMeasurements

Trip

By pass

PQref

Vdqref

m

A1

B1

C1

A2

B2

C2

UPFC

UPFC

A B C

a b c

Tr2: 800 MVA 230 kV/500 kV

A B C

a b c

Tr1: 1000 MVA 230kV/500kV

-0.27

Qref (pu)

Pref (pu)

A

B

C

Power Plant #2Pnom= 1200 MW

A

B

C

Power Plant #1Pnom=1000 MW

L3_50km

L2_50km

L1_65kmdouble circuit

[PQref]

[Vdqref]

[Vdqref][PQref]

m

A

B

C

Equivalent 500 kV

15 000 MVA

Bypass

A

B

C

a

b

c

B_UPFC

A

B

C

a

b

c

B5

A B C

a b c B4

A

B

C

a

b

c

B3

A

B

C

a

b

c

B2

A

B

C

a

b

c

B1

159.1

652.4

650

834

1278

Active Powers (MW)B1 B2 B3 B4 B5

A B C

200 MW

Vpos. seq. B1 B2 B3 B4 B5

Q B1 B2 B3 B4 B5 (Mv ar)

P Pref (pu)

Q Qref (pu)

Vconv _mag (pu)

Vconv _phase (deg.)

P B1 B2 B3 B4 B5 (MW)

SIMULATION RESULTS( Assuming real power amplitude Pref=[5.87 6.87, Qref=[-0.27] constant)

SIMULATION RESULTS(Assuming real power amplitude Pref=[5.87 4.5], Qref=[-0.27] constant)

ADVANTAGES

FACTS devices enhance the stability of the power system with its fast control characteristics and continuous compensating capability. The UPFC can be employed to enhance power system damping by modulating the converter voltages.

The UPFC can fulfill functions of reactive shunt compensation, active and reactive series compensation and phase shifting.

The UPFC allows important function such as stability control to suppress power system oscillations improving the transient stability of power system.

Gives better performance as compared to STATCOM,SSSC and TCSC.

Conclusion:

The above project gives information about the UPFC based control scheme to mitigate the power quality utility in transmission line bus with linear load. The application of UPFC gives the better stability.

 In this study, the MATLAB environment is used to simulate the model of UPFC connected to a three phase-three wire transmission system. This paper presents control and performance of UPFC intended for installation on a transmission line. This paper presents an improvement in the real and reactive power flow through the transmission line with UPFC when compared to the system without UPFC.