06-09-2012, 11:20 AM
SIMULATION OF UPFC USING MATLAB
SIMULATION OF UPFC.pptx (Size: 525.16 KB / Downloads: 110)
OBJECTIVE:
The aim of the project is to model UPFC and its control circuit using SIMULINK and to analyse the control circuit for effective power flow control using three different control schemes –
1. phase angle control
2. cross coupling control
3. generalized control.
After modeling UPFC, a single machine connected to a transmission line along with UPFC has been considered to study its performance.
It is the study of Unified Power Flow Controller and its role in damping power oscillations to improve system performance.
BENEFITS OF FACTS:
In general FACTS devices possess the following technological attributes:
Regulation of power flows in prescribed transmission routes.
Reduces the need for construction of new transmission lines, capacitors and reactors.
Provides greater ability to transfer power between controlled areas, so that the generation reserve margin, typically 18 percent, may be reduced to 15 percent or less. These devices help to damp the power oscillations that could damage the equipment.
INTRODUCTION TO UPFC:
The UPFC is a device which can control simultaneously all three parameters of line power flow
Such "new" FACTS device combines together the features of two "old" FACTS devices:
1. STATCOM
2. SSSC.
These two devices are two Voltage Source Inverters (VSI’s) connected respectively in shunt with the transmission line through a shunt transformer and in series with the transmission line through a series transformer, connected to each other by a common dc link including a storage capacitor.
The shunt inverter is used for voltage regulation at the point of connection injecting an opportune reactive power flow into the line and to balance the real power flow exchanged between the series inverter and the transmission line.
The series inverter can be used to control the real and reactive line power flow inserting an opportune voltage with controllable magnitude and phase in series with the transmission line.
FUNCTIONAL CONTROL OF SHUNT INVERTER
The shunt inverter is operating in such a way to inject a controllable current Ic into the transmission line.
This current consist of two components with respect to the line voltage:
1. the real or direct component id
2. reactive or quadrature component iq
The direct component is automatically determined by the requirement to balance the real power of the series inverter. The quadrature component, instead, can be independently set to any desired reference level (inductive or capacitive) within the capability of the inverter, to absorb or generate respectively reactive power from the line. So, two control modes are possible:
VAR control mode: the reference input is an inductive or capacitive var request;
Automatic Voltage Control mode: the goal is to maintain the transmission line voltage at the connection point to a reference value.
CONCLUSION
Conventional power feedback control schemes make the UPFC induce power swings in transient states.
The time constant of damping is independent of the active and reactive power feedback gains Kp and Kq. Therefore, the conventional control schemes based on only the power feedback loops are not capable of damping of power swings.
The feedback gain Kr with a physical meaning of resistor is effective in damping of power swings.
The proposed control scheme achieves quick response of active and reactive power without causing power swings and producing steady state errors.