A direct control strategy for UPQC in three-phase four-wire system

Based on the p-q-r theory, this paper presents a direct control strategy of unified power quality conditioner (UPQC) used in the nonlinear and unbalance three- phase four-wire system. A algorithm of calculating the series compensation current and shunt compensation voltage in the proposed system is introduced. An analysis of the proposed control strategy and its schematic diagram is described in particular .Simulation results using MATLAB/SIMULINK show that the harmonic current, reactive power of load as well as neutral current are compensated well when unbalance and nonlinear occur in load current or unbalance and sag in source voltage, load voltage get balanced and rated and power factor of power source is about unity.