Modulation and control of a high performance hybrid cascade H-bridge seven-level active power filter with star configuration

This paper presents a three-phase four-wire shunt active power filter (APF) based on hybrid cascade H-bridge seven-level converter as its main circuit with star configuration. A new modulation method based on carrier disposition PWM (CD-PWM) is proposed for the converter which solves the power reverse problem effectively. In system control, DC-link total voltage control based on active current vector superposition is analyzed, in which an active current component is superimposing to the compensation current to change the absorbed power from the grid. Meanwhile, combining with the proposed modulation method, voltage distribution control based on splitting modulation signal is proposed, realizing the power exchanging between two H-bridge cells. Finally, experiment is implemented to verify the correctness of the theory and the results demonstrate an excellent performance of the proposed APF.