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 Xiurui;LI Kai;LI Youfeng(School of Electrical and Control Engineering, Heilongjiang University of Science and Technology, Harbin,Heilongjiang 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：《东北电力技术》2021年第8期16-19,24,共5页Northeast Electric Power Technology

摘　　要：大功率多电平变换器正成为大型光伏能源转换系统的研究趋势。针对三电平中点箝位(NPC)变换器,对两电平电压源变换器进行了扩展和研究。该系统允许在NPC总功率允许的范围内,将尽可能多的光伏组串连接到2条汇流直流母线上,并且NPC固有的优越的输出电压波形能够以较低的开关频率运行,提高系统效率,提高电能质量,降低损耗。在DC-DC的变换电路中,选择了LLC半桥谐振变换器,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,采用中点电压平衡法,针对电网不平衡,采用锁相环技术,保持能够跟踪相位和频率,最终实现稳定合格电压波形输出。High-power multilevel converters are becoming a research trend in large-scale photovoltaic energy conversion systems.It expands and explores the two-level voltage source converter for the three-level midpoint clamp(NPC)converter.This system allows as many PV strings as possible to be connected to the two DC busbars within the allowable range of the total power of the NPC.In addition,NPC's inherently superior output voltage waveform can operate at a lower switching frequency,improving system efficiency and power quality.In the DC-DC conversion circuit,the LLC half-bridge resonant converter is selected to realize the boost while realizing the maximum power point tracking.The balance factor is introduced to control the midpoint voltage,and the midpoint voltage balance method is adopted to target the unbalanced power grid,to discuss the phase-locked loop,to keep track of phase and frequency,and finally to realize stable and qualified voltage waveform output.

关 键 词：光伏并网 NPC LLC半桥谐振变换器 中点电压平衡法 

分 类 号：TM615[电气工程—电力系统及自动化]