Research On Control Strategy Of Photovoltaic Hybrid Energy Storage System Based On Virtual Synchronous Generator Technology

With the increasingly tense global energy environment,the use of clean,efficient and renewable energy such as solar energy has attracted more and more attention.However,a large number of distributed photovoltaic systems are incorporated into the power system,resulting in a significant reduction in the inertia and damping of the power system,which makes it difficult to maintain a short-term power balance to suppress the frequency fluctuation.Therefore,the virtual synchronous generator control strategy can be applied in the power electronic grid-connected inverter.The method simulates the inertia,damping and frequency modulation characteristics of the synchronous generator.The control is flexible,the response speed is fast,and the system voltage and frequency can be supported.In this paper,the control strategy of the DC/AC inverter side and DC side of the virtual synchronous generator control system is studied by taking the photovoltaic grid-connected system containing hybrid energy storage as the research object.Firstly,the development status of photovoltaic grid-connected system is introduced,the main control methods of distributed energy grid-connected system are analyzed,and the topological structure of virtual synchronous generator system is established.Secondly,aiming at the existence of traditional VSG controls power deviation is big,the system damping is small,slow speed of adjustment problems,on the basis of traditional VSG control,PV-VSG systems are constructed and run in parallel with system small signal model is set up,and put forward a kind of virtual synchronous generator with power differential compensation link control strategy,can realize the rapid and reliable parameter setting,the virtual inertia and differential coefficient of two kinds of control parameters adaptive optimization adjustment,increase the damping of the system,and reduce the deviation of steady state power.The simulation results show that the overshoot is small and the stable speed is fast.For PV-VSG dc side of the system,and set up photovoltaic power,energy storage device of the photovoltaic inverter topology,for distributed energy output is not stable,system interconnection of the poor dynamic characteristics of the dc side to join the battery and super capacitor,form a hybrid energy storage system,to achieve a power allocation strategy is proposed in the power allocation of dc bus voltage regulation and energy storage unit.The battery can provide steady-state load power,and the supercapacitor can quickly provide high frequency power required by load changes,so as to limit the influence of load mutation on the voltage fluctuation of DC bus and improve the stability of photovoltaic grid-connected system.Finally,the proposed control strategy is simulated and analyzed under various working conditions,and the effectiveness of the proposed strategy is verified.