基于NPC的光伏并网逆变系统的研究  

Research on Photovoltaic Grid-Connected Inverter System Based on NPC

作　　者：赵修瑞 李锴 李又丰 ZHAO Xiu-rui;LI Kai;LI You-feng(School of Electrical and Control Engineering,Heilongjiang University of Science and Technology,Harbin 150027,China)

机构地区：[1]黑龙江科技大学电气与控制工程学院,黑龙江哈尔滨150027

出　　处：《电工电气》2021年第8期11-15,共5页Electrotechnics Electric

摘　　要：基于三电平中点钳位(NPC)变换器,设计了三电平光伏并网逆变系统,在NPC总功率允许的范围内,将尽可能多的光伏组串连接到两条汇流直流母线上,且NPC的输出电压波形能够以较低的开关频率运行,提高系统的效率和电能质量,降低损耗。在DC-DC的变换电路中,选择了LLC半桥谐振变换器,在升压的同时实现最大功率点跟踪,引入平衡因子对中点电压进行控制,对于对称电网采用dq锁相环检测电网侧电压,当网侧电压不平衡的时候,采用二阶广义积分器通过正负序分离检测电网侧电压跌落程度,并完成锁相,实现系统在检测不平衡电网电压上升以及跌落的时候可以有良好的并网效果。Based on three-level neutral point clamped(NPC)converter,a photovoltaic grid-connected inverter system is designed in this paper.This system allows as many PV strings as possible to be connected to two DC busbars within the power limit of the NPC,and the output voltage shape can operate at a lower switching frequency which could improve efficiency and power quality but with low loss.Firstly,the LLC half-bridge resonant converter is selected to track the maximum power point in DC-DC conversion circuit.Secondly,a balance factor is introduced to control the neutral point voltage,and the dq phase-locked loop is utilized to test the voltage of symmetrical power grid.Thirdly,second-order generalized integrator(SOGI)is to test the voltage dip when the voltage on line side is unbalanced by the method of positive and negative sequence separation control and finally lock the phase.In conclusion,the proposed system could provide an effective networking when the voltage on line-side is tested both rising and dropping.

关 键 词：光伏并网 中点钳位 LLC半桥谐振变换器 中点电压平衡法 

分 类 号：TM464[电气工程—电器] TM615