An optimized hybrid power filter and VAR compensator

During the last three decades different passive, active and hybrid filters have been investigated to deal with disadvantageous effects caused by harmonic currents and voltages, such as overheating of equipment and overcurrents in neutral wires. However, few topologies are able to eliminate the hazardous resonances which may arise in power systems equipped with power factor correctors. In an earlier publication a so-called shunt hybrid power filter (SHPF) was proposed by the authors to shift the resonant frequency created by source inductance and power factor correction capacitors to a non-critical value. The new filter topology integrates a VAR compensator, a transformer with low magnetizing inductance and an inverter into one unit. In this paper, modifications and optimizations of this SHPF are proposed. The hysteresis current controller for the three-phase IGBT voltage source inverter is replaced with a current regulated pulse width modulated space vector controller which takes into account the transformer dynamics. The dc-link voltage control is also enhanced. Furthermore, the stability under distorted load voltages has been investigated. All simulations and experimental results show the excellent harmonic filtering performance of the SHPF while keeping the apparent power of the inverter minimal.