Research On Three-phase Grid-connected Inverter With APF Function

In recent years, worldwide demand for energy is growing accordingly. As its unique advantages, solar photovoltaic technology is widespread concerned. At the same time, nonlinear and impact load are emerging constantly in the grid, reducing the quality of electric energy. Traditional passive filter has been unable to fulfil, active power filter (APF) emerges as the times required. Taking advantage of photovoltaic grid connected inverter and shunt active power filter’s similarity in topology, achieves the effective integration of photovoltaic grid connected and active power filtering at the same set of device. It not only achieves the effective integration of photovoltaic power generation system with APF, but also expands the function of grid connected inverter system and improves the utilization rate of equipment.In view of the reactive power and harmonic problems of the grid connected photovoltaic inverter during grid connected inverting process. The main research contents are as follows:Firstly, to achieve theoretical support that the two devices can be used in the same inverter equipment, this paper analyzes comparatively on the two devices in the main topology, operating principle, control methods and functions. Based on this, obtains the design scheme of the system, and designs the parameters of the components.Secondly, in the current detection field, improves on the ip-iq method of instantaneous reactive power theory, to realize the effective extraction and separation of reactive current and harmonic current of the measured current.Thirdly, in the current synthesis field, considering the grid power factor standards of inverter output current, and the situation that the output current of the inverter with APF function may be over the rated value, controls further reactive and harmonic current command value to ensure system security and stability operation.Fourthly, in the current tracking control field, by combining the advantages of hysteresis and voltage space vector technology, the hysteresis SVPWM current control strategy is used, through real-time switching voltage space vector, outputs the optimum voltage vector, so that the current error is limited in a given hysteresis. The technology achieves instruction current synthesis of output the reactive power and harmonic fast and accurately, at the same time, decreases the switching frequency, and improves the system efficiency.Finally, the system simulation model is implemented in MATLAB/Simulink environment, verified the feasibility and correctness.