Quasi PR Control of NPC Three level PV Grid connected Generation System with Reactive Compensation

In order to avoid the complex coordinate transformations and decoupling control in traditional strategies, a novel control strategy based on quasi proportion resonant (quasi PR) control is proposed for neutral point clamped (NPC) three level photovoltaic (PV) grid connected generation system to improve the efficiency of the system. The system can not only output active power and compensate reactive power to the grid during the day, but also realize reactive power compensation for load at night. Quasi PR controller is introduced to achieve zero steady state error tracing of AC signal under stationary frame, which simplifies the control algorithm and enhances the robustness of the system. At the same time, the respective harmonic compensation controller is designed based on quasi PR principle, which greatly reduces the harmonics of grid current. In addition, the neutral point balance is realized through the feedback of the voltage difference between the upper and lower capacitors. Simulation results verify the feasibility and superiority of the proposed strategy.