Research On Adaptive Inertia Control Strategy Of Distributed Generation Based On VSG

Distributed generation is an effective measure of new energy utilization.However,when more and more distributed generation are connected to the large power grid,the stability of power system will be affected.Most of the distributed power supply takes the power electronic device as the interface,lacks the moment of inertia of the traditional synchronous machine,and lacks the support of voltage and frequency when the external environment is disturbed.Therefore,it is very important to consider how to make the distributed power supply reflect the characteristics of synchronous machine when it is connected to the power grid.The control technology of virtual synchronous generator(VSG)is to introduce the mathematical model and control strategy of the synchronous machine into the control of the inverter,so that the output external characteristics of the distributed power supply based on power electronics are similar to the synchronous machine,which can provide effective support for the stability of the system voltage and frequency.However,the VSG control parameters have a great influence on the dynamic response and stability of the system.In order to solve the problem that the dynamic response performance of the system can not take into account the requirements of stability and rapidity under a single moment of inertia,this paper proposes a moment of inertia adaptive control strategy.Firstly,the mathematical model of the control strategy of the virtual synchronous generator is analyzed in detail.By comparing with the droop control strategy,it is shown that the inverter based on VSG control strategy has not only droop characteristics,but also inertial characteristics,which is advanced and effective.Then,a small disturbance model of VSG based inverter is established to analyze the influence of control parameters on the dynamic response process of the inverter output when the input of VSG control strategy changes.Based on the conclusion,an adaptive virtual moment of inertia control strategy is proposed to adaptively adjust the value of moment of inertia according to the output angular frequency offset of the inverter,so as to achieve the goal of simultaneously adjusting the value of moment of inertia For the purpose of fast response and stability,the response process of the system is optimized when the disturbance occurs.Finally,VSG control technology is applied in the optical storage system.Through the simulation analysis of off grid operation and on grid operation,it shows that the external characteristics of VSG based optical storage system are the same as that of synchronous generator,which shows the effectiveness of the control strategy.Comparing the frequency waveforms of the optical storage system when the external disturbance occurs under the fixed and adaptive moment of inertia,it shows that the adaptive control strategy can take into account the stability and rapidity of the response process at the same time.