Balance control of DC-link voltage between phases for cascade active power filter with star configuration

Cascade active power filter (CS-APF) is an efficient approach for harmonic suppression in medium voltage networks. With star configuration the cascade stage number is less than with delta configuration. Actually the loss of different phase clusters is different during operation. So the active power needed by each phase cluster is different, especially when the load is unbalanced. However, there is no path for Zero-sequence current, and the i_a, i_b and i_c are not independent, which will increase the difficulty of DC-link voltage control. This paper presents a phase current decoupling control strategy for DC-link voltage control of CS-APF with star configuration. Completely independent control of DC-link voltage between three phases is accomplished. Both the system stability and dynamic performance are improved. Simulation results show that the proposed novel decoupling control method is effective and practical.