A coordinated active and reactive power control strategy for grid-connected cascaded photovoltaic (PV) system in high voltage high power applications

This paper presents a grid-connected high voltage high power PV system with cascaded multilevel inverters. A coordinated active and reactive power control strategy is proposed to achieve an effective active and reactive power distribution for each PV inverter module, as well as improve the system power quality and reliability. Vector diagrams are derived to illustrate the power distribution principle. Accordingly, a control system, including the active and reactive control extraction, voltage distribution and synthesization, and 3^rd harmonic voltage injection is developed. Finally, a 3MW/12kV PV system with the proposed control strategy is modeled and simulated in MATLAB+PSIM platform. A downscaled PV system including two cascaded 5kW inverters with proposed control strategy is also implemented in the laboratory. The simulation results are presented to verify the validity of the proposed technology.¹