Frequent Deviation-free Control For Micro Grid Operation Modes Switching Based On VSG

The micro grid uses distributed generation(DG)as the main power supply.It not only can operate with the grid,but also can provide independent power to the users.The smooth switching control between the grid connected mode and the island mode is a key to ensuring stable operation of the micro grid.The conventional grid connected inverter has fast response and no rotation inertia,so it can not provide voltage and frequency support for the power grid containing DG.Virtual Synchronous Generator(VSG)is one kind of control technology that can make the distributed inverter power supply has similar characteristics with the synchronous generator,and it has important support for improving the stability of the power system.A control strategy is proposed,which is frequent deviation-free control for micro grid operation modes switching based on VSG.The main work and research of this paper are summarized as follows:1)Frequent deviation-free control for micro grid operation modes switching based on VSG reactive delay.The VSG uses the traditional droop control to solve the problem of frequency deviation.It is prone to transient oscillations during switching operations.A frequent deviation-free control strategy based on VSG is proposed.When the reactive power changes too quickly,it will affect the active power and cause severe fluctuations.In view of this problem,the delay characteristic of synchronous generator is introduced into VSG to achieve a smooth transition of reactive power steady-state value,which reduces the impact on the system.Combined with the above frequent deviation-free algorithm,it is beneficial to achieve the system with frequent deviation-free smooth switching control.2)Frequent deviation-free control for micro grid operation modes switching based on VSG adaptive inertia.Under normal circumstances,the moment of inertia in the VSG is a fixed value,and dynamic adjustment of power and frequency cannot be taken into consideration.To solve this problem,the fixed moment of inertia value is modified to an adaptively adjustable moment of inertia value to improve the frequency response capability of the micro grid.Combined with the aforementioned frequent deviation-free algorithm and reactive delay characteristics,an integrated control strategy is proposed.It is conducive to the micro grid to achieve smooth switching control without frequency difference.In this article,the simulation experiment model is built by MATLAB/Simulink software,and the experimental results are studied and analyzed to verify the effectiveness of the proposed control strategy.