Simulation and performance evaluation of shunt hybrid power compensator using a control method based on Lyapunov function for power quality improvement

Abstract

In this work, a control scheme based an energy function using Lyapunov method has been formulated for a shunt hybrid power filter so as to reduce current harmonics in a power distribution system. The hybrid scheme contains a parallel connected selective harmonic elimination passive filter tuned at 5^th and 7^th harmonic frequencies is in series with a low power active filter. The developed control law is based on synchronous rotating reference frame theory, which generates a state variable model of the nonlinear system which is linked to development of a switching function based scheme for controlling the active component of the hybrid filter. The stability of the state model following disturbances at the operating point is examined by introducing an energy function for applying Lyapunov’s direct method. Here the derivative of the Lyapunov energy function is made to be negative definite by suitable choice of parameters for ensuring stability and quick response. The performance of the shunt hybrid compensation topology along with the proposed control strategy for balanced, unbalanced and various other loading conditions have been evaluated by simulation of the entire system in Matlab/Simulink platform. It is found that the designed hybrid compensator results in enhanced power quality in the distribution system, satisfying IEEE 519-1992 standards.