Research On VSG-based Control Technology Of Wind And Solar Storage Microgrid Inverter

At present,with the in-depth implementation of the national "double carbon" goal,microgrid based on renewable energy has received continuous attention.Due to the randomness and intermittency of renewable energy such as wind power and photovoltaic,which are easily affected by the changes of external environmental factors,direct integration into the power grid will affect the stability of the power system.Therefore,the establishment of hybrid power generation system combined with wind power and solar energy storage has attracted great attention.Therefore,this paper studies the control strategy of wind and solar energy storage microgrid and Microgrid inverter.The main research contents are as follows:(1)First of all,the shortcomings of traditional control strategy of microgrid inverter are analyzed,the principle of VSG control is described in detail,and the virtual governor and virtual exciter are designed based on the stator and rotor equations of synchronous generator,and the virtual synchronous generator control system is constructed.(2)when the Off-grid microgrid operated in parallel,there often existed the problem of line impedance difference,which will cause unreasonable power distribution and it is difficult to meet the needs of users.The traditional virtual synchronous machine control is difficult to achieve accurate power distribution.In order to solve the above problems,a virtual impedance adaptive control strategy is proposed in this paper.the inverter adjusts the virtual impedance according to the given reactive power,which enables the VSG(virtual synchronous generator)multi-machine parallel system to distribute the load power accurately without satisfying the impedance matching condition.(3)When the island microgrid operates in parallel,there is often a problem of line impedance difference,which leads to unreasonable power distribution and is difficult to meet the needs of users.Traditional virtual synchronous machine control is difficult to achieve accurate power distribution.An adaptive virtual impedance control strategy is proposed,which can make VSG multi-machine parallel system accurately distribute load power without impedance matching.(4)Considering that VSG will generate large impact current when it is connected to the grid,which will affect the system,this paper adopts VSG pre-synchronous connection to the grid.Through the assumed virtual impedance,the virtual angular frequency generated by VSG is compensated to the active loop of VSG,and the virtual voltage amplitude is compensated to the reactive loop.Then the direct grid connection method is compared,and the simulation results verify the stable operation characteristics of the pre-synchronization control.