级联三相光伏逆变器的虚拟磁链直接功率控制策略  

Direct power control strategy based on virtual flux linkage of cascaded three-phase photovoltaic inverter

作　　者：罗瑜珣 李志勇[1] 危韧勇[1] 张威威[1] 

机构地区：[1]中南大学信息科学与工程学院,湖南长沙410083

出　　处：《中南大学学报（自然科学版）》2016年第4期1188-1195,共8页Journal of Central South University:Science and Technology

基　　金：中央高校前沿研究计划前瞻重大专项项目(201021200066)~~

摘　　要：针对三相线电压级联的拓扑应用于光伏并网问题,提出一种改进型虚拟磁链直接功率控制策略(VF-DPC)。通过模块化级联系统的等效模型,分析系统整体的等效开关状态,在网侧采用改进型虚拟磁链观测器抑制直流偏移,得到光伏并网系统功率,在直流侧通过光伏最大功率跟踪(MPPT)得到功率参考值。然后根据系统稳态矢量图进行建模,设计解耦功率控制器,并且为了输出多电平的同时固定开关频率,结合载波移相和空间矢量实现移相空间矢量调制(PSSVM)。以3个模块级联为例,通过Simulink仿真验证本文所提策略的有效性。研究结果表明:本文所提策略是有效的;省略网侧电压传感器,也能保证光伏无需升压装置灵活应用于三相线电压级联并网场合;级联三相光伏逆变器在输出五电平电压的同时,以单位功率因数并网,达到额定输出最大功率4 667 W,并网电流谐波总畸变率仅为2.01%,而且模块化级联系统更具有工程实现价值。To solve the problem that the three-phase line voltage cascaded inverter is applied in photovoltaic（PV） grid-connection, a direct power control strategy based on modified virtual flux linkage（VF-DPC） was proposed. According to an equivalent model of modularized cascaded system, the equivalent switching state of the system was analyzed. In grid side, the power of PV grid-connected system was obtained by using the modified virtual flux observer that removed the DC offset. In DC side, the reference value of power was obtained by maximum power point track（MPPT） algorithm of PV, then the model was built through the steady state vector graph, and the decoupling power controller was designed. In order to achieve the multilevel output and fix the switching frequency, the phase shifting space vector modulation（PSSVM） which combined shifting phase with space vector was realized. Taking three modules cascaded system as examples, the proposed strategy was verified by Simulink. The results show that the proposed strategy is effective. While the grid voltage sensor is omitted, PV connects the three-phase line voltage cascaded inverter without boost devices. The cascaded inverter outputs five-level voltage and connects the grid with unity power factor. PV reaches the maximum power with 4 667 W. The harmonic content of grid current is only 2.01%. In addition, the modularized cascade system has high engineering value.

关 键 词：三相线电压级联 光伏并网 改进虚拟磁链观测器 直接功率控制 移相空间矢量调制 

分 类 号：TM762[电气工程—电力系统及自动化]