Research On Self-synchronous Grid Connected Inverter Based On Non Current Sensor VSG Strategy

With the rise of renewable energy such as photovoltaic and wind power,distributed generation technology and microgrid technology have been developed rapidly.As an important interface for grid connected to renewable energy,inverter's control strategy is of great significance to the stable operation of the microgrid.The Virtual Synchronous Generator(VSG)control strategy simulates the characteristics of the traditional synchronous generator,which has attracted wide attention from scholars in recent years for it's better control effect.In this paper,the VSG control strategy of the inverter and the technology of self-synchronous grid connected in the microgrid are studied.A self-synchronization control strategy based on the non current sensor VSG strategy is proposed.The phase-locked loop is not needed to reduce the complexity of the control structure and improve the performance of the inverter.At the same time,the design of a non grid connected switch is proposed,which can reduce the cost and improve the reliability of the inverter.The main contents of this article are as follows:1)Starting from the synchronous generator,the mathematical model of the three order model of the synchronous generator,the excitation system and the speed control system are analyzed.The non current sensor VSG control strategy is introduced in this paper,and the voltage control,the motion equation of the virtual rotor and the power calculation part are introduced in detail.A detailed explanation of the power calculation section is made,and the characteristics of the non current sensor are pointed out.2)From the traditional way of inverters using phase-locked loop grid connection,the self synchronous grid connection mode without phase locked loop is introduced.The principle of self synchronous grid connection is introduced in detail.In the idea based on this principle and based on the VSG control strategy of non current sensor,a control strategy of self synchronization and grid connection is designed.And a detailed grid connected process is designed for the self synchronization network strategy.3)The design of a non grid connected switch is proposed.In addition to the grid switch,the cost of the inverter is reduced and the reliability is improved.This design takes the way of blocking and opening the output of the PWM module,replacing the function of the original grid switch.4)Several simulations and experiments are designed for the proposed VSG strategy and the self synchronous grid strategy.Under the non current sensor VSG strategy,the simulation of no disturbance under the pure resistive load,the simulation of the load switching and the physical experiment of the load switching are designed respectively.The experimental results verify the droop characteristics and stability of the control strategy.The simulation and physical experiments of self synchronous parallel grid are designed under the strategy of self synchronization and grid connection.The experimental results show that the current impact of the grid connected process is less,and the smooth grid can be realized basically,and the system can keep stable after the grid.The feasibility of the proposed self synchronization control strategy is verified.