基于光伏动态电流参考值的两级式光伏并网系统低电压穿越控制策略OACSTPCD

With the continuous increase in photovoltaic(PV)access capacity,voltage sag in the grid when the PV is off-grid can adversely impact the stable operation of the system.Therefore,it is imperative for the PV system to possess low-voltage ride-through(LVRT)capability.However,the existing PV LVRT strategy,which is based on a fixed DC bus voltage,indirectly adjusts PV output power according to changes in the DC bus voltage,resulting in a slow dynamic response.A two-stage PV LVRT control strategy based on the PV power-voltage(P-U)characteristic curve directly controls PV output power based on the inverter's output active power during a fault.However,a drawback is that the PV voltage and cur-rent reference values must be obtained through model solving,and the model accuracy is susceptible to the completeness of the PV nameplate and irradiance.Moreover,the LVRT effect under partial shadow shading scenarios has not been considered.To address these challenges,a dynamic current reference value-based LVRT control strategy for two-stage grid-connected PV systems is introduced,specifically designed for partial shading scenarios.Initially,a mathematical model is established based on the characteristics of the two-stage grid-connected PV system and PV cells.The strengths and weaknesses of existing LVRT control strategies are analyzed.Subsequently,a dynamic current reference value with ad-aptive convergence characteristics is constructed,and its convergence under scenarios of uniform illumination and local shadow shading is ex-amined.The pre-stage boost circuit is employed to control PV output current using the set dynamic current reference value.This adjustment of the PV operating point accelerates the dynamic response of the PV system and mitigates errors caused by model solutions.Additionally,a fault de-coupling module is incorporated into the maximum power tracking algorithm,enabling the system to lock the maximum power point tracking out-put voltage reference value by switching input quantities during a fault.This facilitates a quick system recovery to the maximum power point after the fault concludes.Finally,the proposed strategy is compared with fixed DC bus voltage control and PV P-U curve-based LVRT control strategies under various environmental conditions through simulation.The results indicate that the proposed strategy exhibits a faster dynamic re-sponse compared to the fixed DC bus voltage control strategy.Moreover,in comparison to the control strategy based on the P-U characteristic curve of PV,the proposed strategy effectively achieves LVRT under different irradiance levels,particularly in partial shadow shading conditions,making it more adaptable to varying environmental conditions.