A Closed-Loop Selective Harmonic Compensation with Capacitor Voltage Balancing Control of Cascaded Multilevel Inverter for High-power Active Power Filters

This paper proposes a closed-loop selective harmonic compensation with capacitor voltage balancing control of cascaded multilevel inverter for high-power active power filters (APF). Firstly, the sum of each phase capacitor voltage is built through absorbing the fundamental active power current from the power system. Further, the capacitor voltage regulation method is presented to balance the voltages of flying capacitor of each cascaded cell in the same phase. Secondly, the selective compensation currents are injected into the power system to provide high power quality at the point of common coupling of a power system. Finally, a prototype APF, rated at 40kVA based on cascaded multilevel inverter is described and the proposed method is implemented with a digital signal processors (DSP) control system. The steady state and dynamic experimental waveforms show that good filtering characteristics and fast responses of the APF are achieved and the each capacitor voltage is also controlled and balanced by using the proposed control methods, which can also be used in high-power applications of more than five-level cascaded inverter for active power filters.