SIMULATION OF UPFC SIMULATION OF UPFC USING MATLABUSING MATLAB

BYBYD.V.S.N.RAJU(05-272)D.V.S.N.RAJU(05-272)

M.SURESH KUMAR(06-208)M.SURESH KUMAR(06-208)D.J.SAI KRISHNA(05-275)D.J.SAI KRISHNA(05-275)

J.P.NAIK(06-206)J.P.NAIK(06-206)

UNDER THE GUIDANCE OFUNDER THE GUIDANCE OFB.DASU B.DASU

ContentsContents

Objective of the projectObjective of the project

FACTS devicesFACTS devices

Introduction to upfcIntroduction to upfc

Circuit DescriptionCircuit Description

Control schemesControl schemes

Present statusPresent status

OBJECTIVE:OBJECTIVE:

The aim of the project is to model UPFC and its control The aim of the project is to model UPFC and its control circuit using SIMULINK and to analyse the control circuit circuit using SIMULINK and to analyse the control circuit for effective power flow control using three different for effective power flow control using three different control schemes –control schemes –

1. phase angle control1. phase angle control 2. cross coupling control 2. cross coupling control 3. generalized control. 3. generalized control.

After modeling UPFC, a single machine connected to a After modeling UPFC, a single machine connected to a transmission line along with UPFC has been considered transmission line along with UPFC has been considered to study its performance.to study its performance.It is the study of Unified Power Flow Controller and its It is the study of Unified Power Flow Controller and its role in damping power oscillations to improve system role in damping power oscillations to improve system performance.performance.

BENEFITS OF FACTS:BENEFITS OF FACTS:

In general FACTS devices possess the In general FACTS devices possess the following technological attributes:following technological attributes:Regulation of power flows in prescribed Regulation of power flows in prescribed transmission routes.transmission routes.Reduces the need for construction of new Reduces the need for construction of new transmission lines, capacitors and reactors.transmission lines, capacitors and reactors.Provides greater ability to transfer power Provides greater ability to transfer power between controlled areas, so that the generation between controlled areas, so that the generation reserve margin, typically 18 percent, may be reserve margin, typically 18 percent, may be reduced to 15 percent or less. These devices reduced to 15 percent or less. These devices help to damp the power oscillations that could help to damp the power oscillations that could damage the equipment. damage the equipment.

Improves the transient stability of the Improves the transient stability of the system.system.

Controls real and reactive power flow in Controls real and reactive power flow in the line independently.the line independently.

Damping of oscillations which can threaten Damping of oscillations which can threaten security or limit the usable line capacity.security or limit the usable line capacity.

FACTS Devices:FACTS Devices:

Name Type Main function ControllerName Type Main function ControllerSVC shunt voltage control ThyristorSVC shunt voltage control Thyristor

TCSC series power flow control ThyristorTCSC series power flow control Thyristor

TCPAR series & power flow control ThyristorTCPAR series & power flow control Thyristor

shunt shunt

STATCOM shunt Voltage control GTOSTATCOM shunt Voltage control GTO

SSSC series power flow control GTOSSSC series power flow control GTO

UPFC shunt & voltage and power GTOUPFC shunt & voltage and power GTO

series flow controlseries flow control

INTRODUCTION TO UPFC:INTRODUCTION TO UPFC:

The UPFC is a device which can control simultaneously The UPFC is a device which can control simultaneously all three parameters of line power flow all three parameters of line power flow

Such "new" FACTS device combines together the Such "new" FACTS device combines together the features of two "old" FACTS devices:features of two "old" FACTS devices:

1. STATCOM1. STATCOM 2. SSSC.2. SSSC.

These two devices are two Voltage Source Inverters These two devices are two Voltage Source Inverters (VSI’s) connected respectively in shunt with the (VSI’s) connected respectively in shunt with the transmission line through a shunt transformer and in transmission line through a shunt transformer and in series with the transmission line through a series series with the transmission line through a series transformer, connected to each other by a common dc transformer, connected to each other by a common dc link including a storage capacitor.link including a storage capacitor.

The shunt inverter is used for voltage regulation The shunt inverter is used for voltage regulation at the point of connection injecting an opportune at the point of connection injecting an opportune reactive power flow into the line and to balance reactive power flow into the line and to balance the real power flow exchanged between the the real power flow exchanged between the series inverter and the transmission line. series inverter and the transmission line.

The series inverter can be used to control the The series inverter can be used to control the real and reactive line power flow inserting an real and reactive line power flow inserting an opportune voltage with controllable magnitude opportune voltage with controllable magnitude and phase in series with the transmission line. and phase in series with the transmission line.

CIRCUIT DESCRIPTION:CIRCUIT DESCRIPTION:

The basic configuration of a UPFC, which is installed between the The basic configuration of a UPFC, which is installed between the sending-end Vs and the receiving-end VR. The UPFC consists of a sending-end Vs and the receiving-end VR. The UPFC consists of a combination of a series device and a shunt device, the dc terminals combination of a series device and a shunt device, the dc terminals of which are connected to a common dc link capacitor .of which are connected to a common dc link capacitor .

Basic configuration of UPFC

FUNCTIONAL CONTROL OF SHUNT INVERTERFUNCTIONAL CONTROL OF SHUNT INVERTER

The shunt inverter is operating in such a way to inject a controllable The shunt inverter is operating in such a way to inject a controllable current Ic into the transmission line. current Ic into the transmission line.

This current consist of two components with respect to the line voltage:This current consist of two components with respect to the line voltage: 1. the real or direct component id1. the real or direct component id 2. reactive or quadrature component iq 2. reactive or quadrature component iq

The direct component is automatically determined by the requirement to The direct component is automatically determined by the requirement to balance the real power of the series inverter. The quadrature component, balance the real power of the series inverter. The quadrature component, instead, can be independently set to any desired reference level (inductive instead, can be independently set to any desired reference level (inductive or capacitive) within the capability of the inverter, to absorb or generate or capacitive) within the capability of the inverter, to absorb or generate respectively reactive power from the line. So, two control modes are respectively reactive power from the line. So, two control modes are possible:possible:

VAR control mode: the reference input is an inductive or capacitive var VAR control mode: the reference input is an inductive or capacitive var request;request;

Automatic Voltage Control mode: the goal is to maintain the transmission Automatic Voltage Control mode: the goal is to maintain the transmission line voltage at the connection point to a reference value.line voltage at the connection point to a reference value.

FUNCTIONAL CONTROL OF SERIES INVERTERFUNCTIONAL CONTROL OF SERIES INVERTER

The series inverter injects a voltage, Vse which is controllable in The series inverter injects a voltage, Vse which is controllable in amplitude and phase angle in series with the transmission line. amplitude and phase angle in series with the transmission line.

This series voltage can be determined in different ways:This series voltage can be determined in different ways:

Direct Voltage Injection mode:Direct Voltage Injection mode: The reference inputs are directly the magnitude and phase The reference inputs are directly the magnitude and phase

angle of the series voltage;angle of the series voltage;Phase Angle Shifter Emulation mode: Phase Angle Shifter Emulation mode:

The reference input is phase displacement between the sending The reference input is phase displacement between the sending end voltage and the receiving end voltage;end voltage and the receiving end voltage;Line impedance emulation mode: Line impedance emulation mode:

The reference input is an impedance value to insert in series The reference input is an impedance value to insert in series with the line impedance;with the line impedance;Automatic Power flow Control mode:Automatic Power flow Control mode:

The reference inputs are values of P and Q to maintain on the The reference inputs are values of P and Q to maintain on the transmission line despite system changes.transmission line despite system changes.

OPERATING PRINCIPLE OF UPFCOPERATING PRINCIPLE OF UPFC

Single phase equivalent circuit

(a) Active power control (b) Reactive power control

Phasor diagrams in case of active and reactive power

Control schemes:Control schemes:

PHASE-ANGLE CONTROLPHASE-ANGLE CONTROL : :

Adjusting the amplitude of the 90" leading or Adjusting the amplitude of the 90" leading or lagging output voltage makes it possible to lagging output voltage makes it possible to control active power .control active power .

The d-q frame coordinates based on space The d-q frame coordinates based on space vectors, the d-axis current id corresponds to vectors, the d-axis current id corresponds to active power, and so it can be controlled by the active power, and so it can be controlled by the q-axis voltage q-axis voltage VcqVcq. Therefore, the reference . Therefore, the reference voltage vector for the series device is given by voltage vector for the series device is given by

……… ……….. ..

CROSS-COUPLING CONTROLCROSS-COUPLING CONTROL : :

The "cross-coupling control" has not only The "cross-coupling control" has not only an active power feedback loop but also a an active power feedback loop but also a reactive power feedback loop. reactive power feedback loop.

This control scheme is characterized by This control scheme is characterized by controlling both the magnitude and the controlling both the magnitude and the phase angle phase angle

GENERALIZED CONTROL SCHEMEGENERALIZED CONTROL SCHEME This "generalized control scheme." The reference This "generalized control scheme." The reference

voltage vector for the series device, is voltage vector for the series device, is generalized, as follows generalized, as follows

A voltage vector produced by the two terms is in A voltage vector produced by the two terms is in phase with the current error vector i*-i. This means phase with the current error vector i*-i. This means that the UPFC acts as a damping resistor against that the UPFC acts as a damping resistor against power swings.power swings.

STATUSSTATUS

CONCLUSIONCONCLUSION

Conventional power feedback control schemes make the Conventional power feedback control schemes make the UPFC induce power swings in transient states. UPFC induce power swings in transient states. The time constant of damping is independent of the The time constant of damping is independent of the active and reactive power feedback gains Kp and Kq. active and reactive power feedback gains Kp and Kq. Therefore, the conventional control schemes based on Therefore, the conventional control schemes based on only the power feedback loops are not capable of only the power feedback loops are not capable of damping of power swings. damping of power swings. The feedback gain Kr with a physical meaning of resistor The feedback gain Kr with a physical meaning of resistor is effective in damping of power swings. is effective in damping of power swings. The proposed control scheme achieves quick response The proposed control scheme achieves quick response of active and reactive power without causing power of active and reactive power without causing power swings and producing steady state errors. swings and producing steady state errors.