Performance improvement of active filter for power distribution line using current source PWM inverter

An active filter (AF) is a device to eliminate switches. There are two types of AF, the voltage source type and the current source type. The voltage source type is common in practical use today. But we have studied and already reported that the AF of the current-source type has the characteristics of rapid and precise controllability of the output current and little interference between the AF and the distribution line. In this paper, we propose two schemes to improve its performance and to reduce its capacitance. To improve the performance of AF, we changed the PWM carrier from the triangular wave used in a previous paper to the sawtooth wave. However, the switching rates remain the same. By using the 5 [kHz] sawtooth carrier (corresponding to 2.5 [kHz] triangular wave) and the multiplexed connection of AF, harmonic currents of less than 19-th order can be eliminated in the distribution line. To reduce the capacitance of the AF, we proposed an AF which eliminates only harmonic currents. By using other apparatus for fundamental reactive power compensation, a more economical system can be achieved. The experimental results on the tested apparatus show that these methods are useful for realization of a current-source type AF.