中频隔离型光伏±35kV/500kW直流变流器研究与工程应用

RESEARCH AND ENGINEERING APPLICATION OF INTERMEDIATE FREQUENCY ISOLATED PV ±35kV/500kW DC CONVERTER

首先提出一种中频隔离型光伏±35 kV/500 kW直流变流器,该直流变流器由三相T型三电平并联中频逆变器模组、中频400 Hz/24脉波移相升压变压器、三相二极管整流桥以及高压滤波电路组成,该变流器具有升压比高、结构简单、成本低的优势;其次,为了实现逆变器并联模组有功、无功功率的实时均分,采用一种瞬时功率均分的功率主从控制方案;接着,提出一种基于中频变压器无功补偿的改进型LCL滤波器参数设计方法以提高变流器的效率。最后,通过Matlab/Simulink仿真以及张北国家大型风电并网系统研发(实验)中心建设的光伏发电中压直流汇集现场示范工程,对所提直流变流器的设计理念和控制方法进行验证,现场并网实测最大效率为96.33%,升压比高达88,输出电压±35 kV,仿真和实验结果证明了所提直流变流器的可行性。

This paper firstly proposes an intermediate frequency isolated photovoltaic ±35 kV/500 kW DC converter. The DC converter consists of a three-phase T-type three-level intermediate frequency parallel inverter module,an intermediate frequency 400 Hz 24-pulse phase-shift boosting transformer,a three-phase diode rectifier bridge and a high-voltage filter circuit. The converter has the advantages of high boost ratio,simple structure and low costs. Secondly,in order to realize the real-time equalization of the active and reactive power of the parallel module of the inverter,a master-slave power control scheme of instantaneous power equalization is adopted in this paper. Then,an improved LCL filter parameter design method based on reactive power compensation of intermediate frequency transformer is proposed to improve the efficiency of the system. Finally,through Matlab/Simulink simulation and the photovoltaic power generation medium-voltage DC collection field demonstration project built by Zhang Bei National Research and Development(Experiment)Center of Large Wind Power Grid Connected System,the control method and design concept of the proposed DC converter are verified. The maximum efficiency is 96.33% and the boost ratio is as high as 88. The output voltage is ±35 kV. Simulation and experimental results prove the feasibility of the proposed DC converter.