Control algorithms for control of real and reactive power flows and power oscillation damping using UPFC

This paper investigates the application of multivariable control technique to multi-input multi-output (MIMO) non-linear problem of a power transmission system with UPFC. The main objective is to achieve effective independent control of real and reactive power flows with zero dynamic interactions. Towards achieving the objective, feed-back linearization control (FBLC) scheme is implemented in the laboratory for the control of UPFC. A two-bus power system with UPFC has been built in laboratory and the control implementation has been carried out using DSP TMS320LF2407A. Both power flow control and power oscillation damping issues are addressed. The excellent correlation between simulation and experimental results using a laboratory test system establish the validity of the proposed scheme. Although the power stage of the developed laboratory system is a scaled down model and has limited ratings, the FBLC controller can be used equally effectively in a more realistic system set up by appropriate scaling factors for the fed-back signals of currents and voltages and for initiating the inverter voltages. The proposed controller enables UPFC to independently control the real and reactive power with absolute decoupling. Also it is found that the overall performance of the system with the proposed controller is far superior to that using conventional cascade PI control structure.