Study on control method of cascade H-bridges active power filter for distribution system

A novel control strategy for 11-level cascade H-bridge APF based on TCPS-PWM is proposed in this paper. When the cascade inverter is applied to active power filter for distribution system, it is expected that the switching frequency and the EMI will be dramatically reduced. By the strategy, each power unit is modulated in low frequency. At the same time, the equivalent switching frequency is still high so as to meet the high tracing ability for better compensation performance. This paper also focuses on the transposing modulation method to balance the DC voltage. As each H-bridge´s DC voltage is balanced under TCPS-PWM modulation, only one DC voltage is needed in practice. Then the amount of voltage transformer dramatically decreases, and the AD sampling circuit is simplified. At last, analyse and simulation show the feasibility and superiority of the proposed strategy.