The Research On Power Control Of Single-Phase Photovoltaic Grid-Connected Inverter System

With the depletion of non-renewable energy and the improving of people's awareness of environmental protection, photovoltaic power generation has become an important green energy of the 21 st century. The quality of the output current of the photovoltaic inverter can have a direct impact on the power grid and users. This thesis mainly studies the power control strategy of single-phase PV inverter.Firstly, the topology of single-phase inverter is studied. A two-stage, transform-less inverter is designed as the object of study. Then, a variable step perturbation and observation method is proposed based on the mathematical model of solar cells, which can increase the maximum power point tracking speed and reduce the power oscillation. The active power control strategy based on dual-loop control strategy is analyzed. The PI control is used in outer voltage loop to ensure bus voltage stability. The quasi proportional resonant method is used in inner current loop. A single-phase photovoltaic inverter reactive power compensation strategy is proposed. By the presented sinusoidal signal integrator, a two-phase quadrature current signal is constructed and can overcome the delay problem in traditional method. Active power control and reactive power compensation is achieved based on the instantaneous reactive power theory. The Saber software verifies the theoretical analysis and algorithms.Finally physical experiments verify the efficiency of MPPT, European efficiency of the inverter can meet the application requirements. The effect of the active power control under different input power level is tested and reactive power compensation of the inverter is verified, which proves the effectiveness of the system power control.