Hybrid power filter

This paper deals with a harmonic filter to eliminate source current harmonics in power system. It is a combination of shunt passive filter and series active filter. The main section of the active power filter, a voltage source inverter, is connected between AC source and nonlinear load through a series transformer. Current harmonic compensation is achieved by injecting equal fundamental current instead of harmonic current at the point of connection, thereby blocking the harmonics and improving the power quality of the connected power system. In this a hysteresis based current control scheme is employed to derive the gating signal of the AF. Reference current of the controller is the fundamental component of the source current. The principle of operation of the proposed filter along with current control scheme and fundamental detection methods are discussed in detail. The performance of the filter is verified by the simulation results of current and voltage type harmonic producing loads.