Research On Virtual Synchronous Generator And Its Application In Islanding Microgrid

With the continuous advancement of energy transition and the proposal of carbon neutral goal,distributed power generation has entered a period of rapid development.Microgrid is an effective way to absorb distributed power supply,which can improve the low reliability of distributed power supply.The distributed power supply is usually connected to the microgrid through power electronic converter and does not have the inertia and damping characteristics of the traditional synchronous generator.When the microgrid is in island operation mode,the low inertia of distributed power will bring severe challenges to the stable operation of the microgrid due to the lack of support from the main grid.Virtual Synchronous Generator(VSG)control is to simulate the operation characteristics of the Synchronous Generator,so that the grid-connected inverter of the distributed power supply has inertia and damping characteristics,which can improve the stability of the microgrid.Taking VSG as the object,this thesis mainly studies VSG DC bus voltage stability method and its coordinated control strategy in islanding microgrid,which has certain theoretical value and practical significance for improving the operation stability of islanding microgrid.Firstly,the corresponding relationship between VSG and traditional synchronous generator and the mathematical model of VSG are studied.The active power frequency and reactive power voltage control modules of VSG are designed,and the influence of inertia J and damping coefficient D on the output active power and frequency of VSG is analyzed.Matlab /Simulink simulation results verify the influence characteristics of parameters J and D on VSG output.Then,aiming at the problem of VSG bus voltage instability caused by the instability of distributed power supply,a VSG bus voltage stabilization method based on bidirectional DC converter is proposed.The VSG system combined with energy storage unit,the topology of bidirectional DC converter and the PWM phase-shifting modulation method are studied,and the wide range control strategy of bus voltage is given.The simulation results of EMTDC/PSCAD show that the bidirectional DC converter and the energy storage unit provide a good support for the DC bus voltage of VSG,which verifies the correctness of the proposed method.Finally,in order to solve the voltage and frequency stability problems of isolated microgrid with high proportion distributed power supply,a coordinated control strategy of optical storage distributed power supply and other distributed power sources based on VSG control is proposed.In the islanding microgrid,the optical storage distributed power supply adopts VSG control,the battery storage distributed power supply adopts VF control,and the wind power and photovoltaic distributed power supply adopts PQ control to track the maximum power point(MPPT),so as to achieve the maximum economic benefits.In Matlab /Simulink,the simulation model of the whole island microgrid is built.The simulation results show that the island microgrid can maintain the stability of voltage and frequency,and ensure the stable operation of the system under any working conditions.