A control method of active power filter in unsymmetrical and distorted voltage system

In this paper, the authors propose a calculation method for the compensating current reference of an active power filter, where a nonlinear load exists in the three-phase three-wire unsymmetrical voltage system. This new method has been named the extension pq method. The authors have experimented with the extension pq method and the pq method, using the same current controlled IPM inverter for both methods. The results of the experiments proved that, in an unsymmetrical voltage system, the source current was distorted in the case of the pq method, but undistorted in the case of the extension pq methods. Finally, the authors propose calculation methods for the compensating current reference in an unsymmetrical and distorted line voltage system. Experimental results show that the active power filter based on this method gives satisfactory operation.