The Research of Reactive Power Control Strategy for Grid-connected Photovoltaic Plants

Grid-connected photovoltaic (PV) plants should have independent control of reactive power to provide reactive power support to the grid. The study analyzes the impact the varying output of the active and reactive power of photovoltaic plants have on network voltage, and derives the relationship between active and reactive power change and voltage change amount. A reactive power control strategy of for grid-connected PV plants is proposed. It shows that voltage fluctuation at point of common coupling (PCC) caused by PV plants will be suppressed. The overall control strategy scheme diagram of active power and reactive power of PV plants is structured in stationary frame, avoiding the complex aspects of the phase-locked loop (PLL) and decoupling. The control method is analyzed under the adverse grid conditions, the adverse impact on the grid current caused by the outlets voltage distortion and imbalance is suppressed. The constraint condition of the reactive power of the inverter is analyzed and deduced. Simulation results prove the validity of the theoretical analysis, demonstrating its excellent performance.