Three Phase active filter with Four Switching Inverter and variable index modulation

In this paper is proposed new Shunt Active Power Filter (SAPF). Reduction of current harmonic and cost of filter are two important goals in these devices. To prevent adverse effects these goals to each other, it is better two goals is separated then aside are achieved. To reduce costs Four Switching Three Phase Inverter (FSTPI) is used instead of Six Switch Three Phase Inverter (SSTPI). This replacement has many advantages such as reduction of cost, switching loss, circuit for pulse generation and microprocessor real-time calculations but lead to happen unbalance in the system. This problem has been solved with new method. In order to reduction harmonic new PWM modulation technique with a variable index has been suggested that in comparison with a fixed index type has more capability. Some of SAPFs have been considered sinusoidal source without harmonics. In this paper, none sinusoidal sources are considered. In fact one of the most important advantages proposed SAPF is independence on harmonic of voltage source.