Research On Coordinated Control Strategy Of Photovoltaic/battery Islanded Microgrid Based On VSG

In recent years,the application of distributed power generation technology based on renewable energy has received extensive attention and development.As an effective form of dissipating distributed power,microgrid provides a broad space for improving the integration of distributed generation systems and traditional power systems.At present,the microgrid is still in the stage of theoretical research and small-scale application.To realize the large-scale application of the microgrid,many key technical problems need to be solved.In this paper,the AC/DC hybrid islanded microgrid formed by photovoltaic and battery is adopted,and the control strategy based on virtual synchronous generator is adopted to realize coordinated and stable control.In-depth study of the complementary system formed by photovoltaic power generation and battery to achieve the key stability technology of the DC to DC voltage.Photovoltaic power generation is susceptible to environmental factors,and it is necessary to adopt the maximum power point tracking control strategy and control it in one direction to connect it to the DC side of the microgrid.In order to realize the energy complementary system with photovoltaic,it is necessary to use a controller with bidirectional DC/DC charge and discharge control to control the charge and discharge of the energy storage,realize the power balance on the DC side of the microgrid system and suppress the power fluctuation.For photovoltaic/battery AC-DC hybrid islanded microgrid,the traditional virtual synchronous generator control can improve the inertia and frequency characteristics of the system to some extent.To further optimize the frequency and power transient response characteristics of the system,this paper proposes a virtual synchronous generator control strategy based on frequency deviation integral compensation.The control strategy integrates the frequency variation into the forward channel of the first-order virtual inertia link to reduce the power impact caused by the load disturbance on the system,thereby suppressing the power and frequency oscillation,and ensuring the output power steady state.In the case of control accuracy,the dynamic power and frequency response speed is increased and the amplitude variation is prevented from being too fast.At the same time,the frequency modulation coefficient is retained in the active frequency control link,so that the steady-state frequency modulation characteristics of the microgrid system are preserved.The influence of different virtual inertia J and damping coefficient D on the transient response of the system is further discussed by establishing the small-signal model of the networked inverter.The setting scheme and tuning method of parameters J and D are provided.In the coordinated control of photovoltaic/battery AC-DC islanded microgrid,the microgrid power management layer is usually needed to achieve power balance.This paper proposes a comprehensive control strategy without complicated programming.Considering the condition that the state of charge of battery and the DC bus reference voltage deviation exceed the limit,a multi-loop power control strategy is constructed in the pre-stage structure,and the multi-loop power control strategy can effectively prevent the state of charge of energy storage from exceeding the limit.The DC bus voltage suddenly changes and the front stage power balance is achieved.In addition,the main inverter of the post-microgrid adopts the virtual synchronous generator control strategy to realize the control of the system voltage frequency and the following of the load.The constant power control strategy is adopted from the inverter to provide a constant power demand to the microgrid.