A novel isolated-port voltage equalizer for photovoltaic systems under mismatch conditions

摘要

A novel voltage equalizer called Multilevel Architecture is proposed for series-connected photovoltaic (PV) system to prevent negative influence of mismatch issues. This undesirable mismatch triggers multiple power maxima in PV string P-V characteristics, encumbering maximum power points tracking (MPPT) algorithms. This paper designed a control scheme for isolated-port flyback converter operating in discontinuous conduction mode (DCM). The synchronous strategy is also investigated and discussed for the equalizer to compensate the mismatched PV elements efficiently. Furthermore, Simulation and experimental results for four PV elements connected in series are included to demonstrate the benefits of this approach, with biasing currents of 5A, 4A, 3A, 2A, respectively. With the proposed voltage equalizer, local MPPs were successfully eliminated and the total generated power is significantly increased.