Research On Photovoltaic Inverter Control Based On Virtual Synchronous Generator

In recent years,new energy power generation has flourished,and the grid-connected capacity of photovoltaic power generation has been increasing.At present,power grid inverters are usually used for grid connection,but the commonly used droop control method cannot make the inverter power source have the characteristics of synchronous generator frequency modulation and voltage regulation.Therefore,this paper introduces a virtual synchronous generator(VSG),which can make the inverter power supply and the synchronous generator have similar frequency modulation and voltage regulation performance.Firstly,the photovoltaic cells are modeled by the mathematical model of photovoltaic cells,and the circuit model is further improved,and the control mode.Secondly,PV inverter adopts the PQ control strategy in the grid-connected operation mode,and the droop control strategy is adopted in the island operation mode.After analyzing the main circuit structure of the microgrid,the selection problem of the inverter is proposed.The voltage-type inverter is selected,and the PQ control strategy adopted in the grid-connected operation mode can better ensure energy utilization.The island operation mode is also the off-grid operation state.When the microgrid enters the island operation mode,there is a selection problem of the control strategy.Under this mode state,the inverter cannot obtain the voltage and frequency indicators provided by the grid.Since the droop control is applicable in both single and multi-machine situations,the droop control strategy is selected.The traditional droop control may have a circulation problem when powering the load.In order to better solve the circulation and not affect the control effect and power distribution problem,the virtual impedance is added to the control circuit to eliminate the circulation,and the energy utilization problem is Greatly improved.Thirdly,this paper focuses The basic principle of VSG is elaborated.According to the stator electrical mathematical model of the synchronous generator and the mechanical mathematical model of the rotor and the technical requirements of the microgrid operation for the photovoltaic inverter power supply,the power frequency controller and the excitation controller are designed.The simulation model was built by MATLAB/Simulink,and the correctness of the virtual synchronous generator was verified by simulation.The effect of the moment of inertia was verified by comparison with the droop control strategy.Then the grid-connected characteristics of the virtual synchronous generator were verified,including the load.In the case of fluctuations,the virtual synchronous machine reflects the frequency modulation and voltage regulation of the synchronous generator characteristics and maintains the stability of the system.It can meet the technical requirements of the microgrid for photovoltaic inverter power supply during grid-connected operation and island operation.Figure [116] table [7] reference [52]...