Parallel Control of Three-Phase Three-Wire Shunt Active Power Filters

A three-phase three-wire shunt active power filter (APF) suitable for parallel operation is proposed in this paper to overcome difficulties in the field of high power applications. This APF can operate independently and compensate the load harmonic current according to its own capacity-limitation. Furthermore, the output current of each APF is optimized so that the APF with large capacity compensates more current and the one with small capacity compensates less current. In this way, the feasibility and security of modular APF can be guaranteed. Based on this, the parallel control strategy for modular APF is also given, which can ensure that each APF switches on/off according to actual load harmonic current and has little impact on the whole system. In the end, simulation and experiment results are shown to testify the validity of proportion compensation strategy based on capacity-limitation and the feasibility of coordination control strategy for parallel running of modular APF