Active Power Filter with a Reduced Number of Current Sensors

In this paper, a modification of a parallel active power filter (APF) control is presented. Its purpose is to decrease the cost of the hardware by minimizing the number of current sensors, normally present in conventional topologies. The approach employs the direct current control (DCC), a method for predictive control of currents in polyphase systems, developed by the authors. Since in traditional filter topologies, currents for compensation of distorted load currents are produced by an inverter-like circuit, DCC, as in similar approaches, is used for filter current generation. In this particular case, a variant of DCC with a modulated voltage during a sampling interval is used. However, following a relatively simple algorithm, only a grid current can be used in DCC, without any need for filter and load current measurement, thus eliminating the necessity of installing corresponding current sensors. In addition, robustness of the approach was proved by examining the effect of alteration of the filter model parameters. Simulation results show validity of the proposed method.