Research On Integrated Control Strategy Of Photovoltaic VSG Under Power Grid Voltage Drop

With the increase in the penetration rate of new energy power generation,how to solve the subsequent stability problem has become an important issue,so the virtual synchronous generator VSG(Virtual Synchronous Generator)technology has been proposed.In photovoltaic grid-connected operation,the power grid is susceptible to short-circuit faults caused by certain reasons,causing the voltage of the power grid to drop,affecting its operation,and even off-grid.And when the grid voltage drops,the photovoltaic inverter has problems such as inrush current.Traditional virtual synchronous generators will still have surge current or voltage overcharge,which exceeds the capacity of power electronic components,resulting in component damage and destruction;for the above problems,here are the following aspects to replace the photovoltaic grid-connected power generation system based on VSG technology the study:First,the development of VSG control technology is described,and the research status of the photovoltaic grid-connected power generation system based on the traditional control strategy and the VSG strategy under low voltage conditions is analyzed.The additional current loop in the traditional traditional control strategy is improved.The basic principle,through the analysis of the principle and structure of the photovoltaic power generation system,establish a detailed mathematical model of traditional photovoltaic including photovoltaic cell arrays,DC/DC converters,and inverters to achieve maximum power tracking MPPT(maximum power point tracking)strategy and tradition Inverter control strategy.The previously established photovoltaic power generation model is simulated and verified.Then,in order to establish a photovoltaic grid-connected power generation system based on VSG technology,based on the synchronous generator principle model,the equivalent mechanism of the photovoltaic inverter based on VSG was analyzed and studied,and the inverter control method based on VSG was established.And established its mathematical model for simulation verification.Finally,the traditional control strategy of the virtual synchronous inverter under low voltage conditions is decomposed and its effect is analyzed,the control strategy is improved,and the comprehensive control strategy of the AC and DC sides is proposed:the DC side uses super capacitors and switching MPPT derating strategy.The PSO algorithm optimizes the setting of quasi-PR control parameters,and performs simulation verification under different grid voltage drop depths.The results show that the proposed AC-DC integrated control strategy can effectively suppress the surge current and voltage overcharge.