电网电压不平衡跌落下两级式光伏并网系统直压控制策略  

DC voltage control strategy of two-stage photovoltaic grid-connected system under unbalanced voltage drop of grid

作　　者：王茂春 陈春萌 杨凯璇 李兵 刘舟扬 刘飞[2] WANG Maochun;CHEN Chunmeng;YANG Kaixuan;LI Bing;LIU Zhouyang;LIU Fei(State Grid Qinghai Electric Power Company,Xining 810000,China;School of Electrical Engineering and Automation,Wuhan University,Wuhan 430072,China)

机构地区：[1]国网青海省电力公司,青海西宁810000 [2]武汉大学电气与自动化学院,湖北武汉430072

出　　处：《武汉大学学报（工学版）》2022年第3期283-291,共9页Engineering Journal of Wuhan University

基　　金：国家电网公司科技项目(编号:5442NY190024)。

摘　　要：两级式光伏并网系统将光伏电能汇集至低压直流母线,通过并网逆变器送入交流电网,低压直流母线能满足本地负载需求,实现光伏就地消纳,而且相比传统分散逆变、就地并网的方案具有更高的发电能效。两级式光伏并网系统在交流电网电压发生不平衡跌落时,存在低压直流母线电压上升以及母线电压二倍频波动问题。电压上升可能导致光伏脱网,不满足光伏并网的低电压穿越要求;电压上升及二倍频波动也不利于直流负载的稳定工作。为了稳定电网电压不平衡跌落下直流母线电压,针对前级DC/DC(direct current to direct current)变换器采用了最大功率点跟踪与定低压直流母线电压控制模式切换策略,并在此基础上增加了比例谐振控制,解决了低压直流母线电压上升及二倍频波动问题,保证了电压的稳定,提高了电能质量。以电网电压发生单相跌落为例,进行了仿真和试验验证,结果证明了该控制策略的有效性。The two-stage photovoltaic grid-connected system collects photovoltaic power to the low-voltage DC bus,and sends it to the AC grid through the grid-connected inverter.The low-voltage DC(LVDC)bus can meet the local load demand and realize the on-site photovoltaic consumption.Compared with the traditional decentralized inverter and on-site grid connection scheme,the two-stage photovoltaic grid-connected system has higher power generation efficiency.However,when the two-stage photovoltaic grid-connected system experiences an unbalanced voltage drop of AC grid,there are problems with DC bus voltage rise and doublefrequency fluctuations of the bus voltage.The voltage rise may cause the photovoltaic to be disconnected from the grid,which does not meet the low voltage ride-through requirements of photovoltaic grid-connected.In addition,the voltage rise and double-frequency fluctuation are also not conducive to the stable operation of the DC load.In order to stabilize the DC bus voltage under unbalanced voltage drop of grid,this paper adopts the maximum power point tracking and constant low-voltage DC bus voltage control mode switching strategy for the pre-stage DC/DC(direct current to direct current)converter,and adds proportional resonance control on this basis.It solves the problems of low-voltage DC bus voltage rise and double-frequency fluctuations,ensuring voltage stability and improving power quality.By taking the single-phase sag of the grid voltage as an example,simulation and experimental verification are carried out.The results prove the effectiveness of the control strategy.

关 键 词：两级式光伏并网系统 DC/DC变换器 低电压穿越 定电压控制 二倍频波动 

分 类 号：TM615[电气工程—电力系统及自动化]