Research On Control Strategy Of Photovoltaic Grid Connected Inverter

With the rapid decline of petrochemical energy storage,photovoltaic power generation is considered as one of the most potential new energy generation methods in the 21 st century,which has been widely developed and applied in practice.Photovoltaic grid connected inverter is the port device needed by photovoltaic power generation system to connect the large power grid.Its control performance plays a decisive role in the stable operation and grid connected power quality of photovoltaic grid connected system.Therefore,on the basis of reliable grid connected control,it has certain theoretical and practical value to study the inverter control strategy to improve the grid connected power quality.Aiming at the problem of control strategy of photovoltaic grid connected inverter,this paper analyzes and explores deeply.Firstly,the structure and principle of grid connected inverter are analyzed.At the same time,order to collect the phase and frequency of grid voltage,the output current of the inverter has the same frequency and the same phase with the grid voltage,sine pulse width modulation(SPWM)and phase-locked loop technology are used to realize grid connected.Secondly,in order to solve the problem that the photovoltaic grid connected system is greatly affected by grid frequency fluctuation and grid harmonics in the process of grid connection,the dual loop control strategy is adopted in the grid connection control of inverter.According to the research of common current controller,the current inner loop adopts the compound control strategy of quasi proportional resonance control and deadbeat control combined with parallel structure,and the main role of quasi proportional resonance control is to In order to avoid the influence of the frequency offset of the power grid,the system realizes the tracking of the fundamental current to the power grid voltage without static difference,and improves the dynamic response speed of the system;the deadbeat control can greatly suppress the harmonic of the power grid,enhance the anti-interference ability of the system,improve the stability of the system,and combine the two control methods to improve the power quality of the grid connected system.Thirdly,the hardware and software of photovoltaic grid connected inverter system are designed comprehensively,which is ready for the control simulation research of photovoltaic grid connected inverter.The hardware part mainly includes the selection of power switch,absorption circuit design,output filter design,control circuit design,zero crossing detection circuit and overcurrent protection circuit design;the software part mainly includes the main program design,interrupt program design and digital phase-locked loop design.Finally,the simulation model of grid connected inverter is built with MATLAB,and the simulation waveforms of quasi proportional resonance control,deadbeat control and composite control are obtained according to the parameter settings.The in-depth analysis is made from the three aspects of the system’s steady-state,dynamic and harmonic suppression,which proves that the control strategy can effectively solve the problem that the photovoltaic grid connected system is affected by the grid frequency wave in the operation process Dynamic and grid harmonics have a great impact.