Control Strategy Of Hybrid Microgrid Virtual Synchronous Machine Based On Dual Adaptive Parameters

In the AC/DC hybrid microgrid,the interface converter(Interfacing Converter,IFC)usually uses droop control to realize the power exchange between the AC and DC subnets.However,because the conventional droop control does not have inertia and damping,when the load or power supply fluctuates It cannot provide inertial support for the dynamic response process of AC frequency and DC voltage.Although the traditional virtual synchronous machine control(Virtual Synchronous Generation,VSG)can provide inertia and damping for the system,it has no obvious effect on the suppression of power oscillation during the power exchange process of the AC and DC microgrid.According to the internal AC and DC subnets of the hybrid microgrid With instantaneous power balance characteristics,this paper proposes a dual-adaptive virtual synchronous machine control strategy based on the principles of AC and DC microgrid power transmission.The AC and DC bus-tie converters in the hybrid microgrid not only have the steady-state power distribution characteristics of droop control,but also can simulate the dynamic frequency response characteristics of the synchronous motor,thereby effectively improving the dynamic response of the DC voltage and increasing the AC frequency in the hybrid microgrid.,Anti-disturbance performance of DC voltage.First,the electrical equation,mechanical equation and excitation equation of the synchronous generator are analyzed,and its mathematical model is established,and the stator voltage equation and rotor motion equation are simulated as virtual governor and virtual excitation controller.Secondly,according to the instantaneous power balance characteristics of the hybrid microgrid,the hybrid microgrid VSG control control is proposed,a small signal model is established,and the influence of the moment of inertia and damping coefficient on the stability of the control system is analyzed,and a dual adaptive based on the principle of power transmission is proposed.VSG control,and determine the value range of the rated virtual parameters through the small signal model analysis method.After that,through Matlab/Simulink simulation to verify that the AC/DC interface converter is operating in the inverter and rectifier mode,compare the interface converter using traditional VSG control and the simulation of the dual-adaptive parameter hybrid microgrid virtual synchronous machine control strategy proposed in this paper.As a result,the superiority of virtual synchronous motor control compared with traditional VSG control was verified.Finally,in the event of a short circuit on the AC side of the microgrid grid-connected converter,a sudden voltage change causes the device to disconnect from the grid,and the voltage surge after the fault removal increases the risk of overvoltage and overcurrent on the DC side of the inverter,etc.,a virtual impedance is introduced to change the voltage.The reference signal of the control link plays the role of voltage support during the fault.Aiming at the transient impact caused by the voltage surge after the fault is removed,the changes of active and reactive power are analyzed,and a reactive current control strategy is proposed to stabilize the bus voltage at the grid-connected point.Through MATLAB/Simulink simulation,it is verified that this control strategy can make the microgrid grid-connected system smoothly traverse the grid-side fault,and there is no voltage oscillation after the fault is removed.