A Virtual Impedance-Based Control Bandwidth Enhancement Method for Three-Level Flying Capacitor Boost Converter

Abstract:
The control performance of photovoltaic generation system is highly dependent on the operating point position on the current-voltage curve. When the system operates in the near-constant dc-link voltage region, the control bandwidth of the system is small. This may bring about two problems: first, the MPPT period will be restricted, thus slow down the tracking process of the system; second, low bandwidth limits the speed of active power adjustment process.In this paper, the average state-space equation of the three-level flying capacitor boost converter used in PV inverters is first studied and derived, and then a strategy based on virtual impedance is proposed to improve the control bandwidth of the three-level flying capacitor boost converter. Finally, some simulation results show that the proposed virtual impedance strategy can achieve the expected effect of increasing the control bandwidth of the system.