Study And Practice Of Photovoltaic Grid-Connected Inverter

PV grid-connected power generation is the trend at present in the world, and plays an important role in relieving conventional energy resources shortage and decreasing environmental pollution. Grid-connected inverter is core part of PV power generation system, 3kWp grid-connected inverter based on main control chip DSP TMS320LF2407 was designed, can advance the whole system efficiency.Single phase grid-connected inverter main circuit topology and operating principle were analyzed in detail, and researched operation of power devices in different switch mode. Voltage & current double close-loop control was presented based on grid-connected inverter output feedback and grid voltage feedforward control technology; injecting certain dead time and compensating deadband by combining current sampling and current predicting to prevent top and bottom IGBT of the arm from being straight in. Simulation of system model showed double close-loop control can improve output waveform.Grid-connected inverter main control circuit was designed based on DSP, including clock circuit, communication circuit, driving circuit, sampling circuit etc., and then main circuit key parameters and filter were designed. Main program, PWM interrupt program and CAP capture interrupt program realized system hardware circuit and control strategy.Solar PV array output characteristic is non-linear by outside environmental factors; common maximum power tracking methods were reviewed, tracking PV array maximum output power by variable-step optimization method. Islanding conditions and damages were analyzed when system was grid-connecting, active and passive methods of detection & prevention were presented.Finally experimental results of PV grid-connected inverter of voltage source current output control based on DSP were analyzed. The results show: output power factor is near to 1, grid-connected inverter can quickly and steadily track solar battery maximum output power and send sinusoidal current wave into grid, which is the same frequency and phase as grid voltage. The system is high inverter efficiency, can securely and reliably run.