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  

Low-Voltage Ride-Through Control Strategy for Two-Stage Grid-Connected PV Systems Based on Dynamic Current Reference Value

作　　者：刘文飞 赖辉 杨勇 牛浩明 苗虹[2] LIU Wenfei;LAI Hui;YANG Yong;NIU Haoming;MIAO Hong(State Grid Gansu Electric Power Research Inst.,Lanzhou 730070,China;College of Electrical Eng.,Sichuan Univ.,Chengdu 610065,China)

机构地区：[1]国网甘肃省电力公司电力科学研究院,甘肃兰州730070 [2]四川大学电气工程学院,四川成都610065

出　　处：《工程科学与技术》2024年第2期55-67,共13页Advanced Engineering Sciences

基　　金：国家电网有限公司科技项目(52272222001J)。

摘　　要：随着光伏接入容量的不断提升,电网电压跌落时光伏脱网会影响系统稳定运行,因此光伏系统应具备低电压穿越(LVRT)能力。然而,目前常用的两级式光伏并网系统LVRT控制策略存在光伏动态响应慢及控制效果受限于光伏P–U特性曲线的数学模型精度等问题,且未考虑局部阴影条件下的适用性。基于此,提出一种基于光伏动态电流参考值的LVRT控制策略。首先,在建立两级式光伏并网系统及光伏电池P–U特性数学模型的基础上,分别对目前常用的基于定直流母线电压和基于光伏P–U特性曲线的LVRT控制的原理及不足进行了分析。其次,针对前级boost电路的控制构造了具有自适应收敛特性的光伏输出电流动态参考值以对光伏工作点进行直接调整。该策略无需对光伏P–U特性曲线数学模型进行求解,避免求解误差的同时加快了光伏动态响应速度。此外,在最大功率跟踪(MPPT)算法中引入故障解耦模块,在电网低电压故障期间对MPPT输出电压参考值进行锁定,避免MPPT无效运算带来的电压参考值偏移,使系统在故障结束时能以最快速度恢复至最大功率点。最后,通过仿真将所提策略与目前常用的基于定直流母线电压和基于光伏P–U特性曲线的LVRT控制策略在多种环境条件下进行对比。仿真结果表明:与定直流母线电压控制策略相比,所提策略下光伏动态响应快;与现有基于光伏P–U特性曲线的控制策略相比,所提策略不受P–U特性误差的影响,在辐照度变化尤其局部阴影条件下均能很好地实现低电压穿越。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 facilita

关 键 词：两级式光伏并网系统 低电压穿越 局部阴影 动态电流参考值 

分 类 号：TM464[电气工程—电器] TM615