分相级联大容量高压直流变压器拓扑及控制策略  

Topology and Control Strategy of Split-phase Cascaded High-voltage Large-capacity DC Transformer

作　　者：吴小丹[1,2] 殷子寒 朱海勇 WU Xiaodan;YIN Zihan;ZHU Haiyong(NR Electric Co.,Ltd.,Nanjing 211102,China;NARI Group Corporation(State Grid Electric Power Research Institute),Nanjing 211106,China)

机构地区：[1]南京南瑞继保电气有限公司,江苏省南京市211102 [2]南瑞集团有限公司(国网电力科学研究院有限公司),江苏省南京市211106

出　　处：《电力系统自动化》2023年第17期137-148,共12页Automation of Electric Power Systems

基　　金：国家重点研发计划资助项目(2021YFB2401100)。

摘　　要：文中提出一种分相级联大容量高压直流变压器拓扑,可有效满足包括光伏等新能源系统的接入及送出。该拓扑采用高压侧3个单相模块化多电平换流器(MMC)级联及中压侧三相MMC结构,通过400 Hz中频变压器进行电气隔离,可有效降低功率模组直流侧电容容值。为解决高压侧桥臂电容电压均衡的难题以提高拓扑运行的可靠性,提出了高、中压两侧解耦的控制策略。高压侧采用包括桥臂直流环流及中频环流控制在内的5层桥臂电容电压逐层控制方案,并通过3个单相V/f闭环控制建立中频交流电压。中压侧采用电流双序控制附加静止坐标系统下的电流直接控制以抑制桥臂内部环流。最后,搭建电磁暂态仿真模型,并通过稳态、动态及暂态实验全面验证所提拓扑及控制策略的有效性。This paper proposes a split-phase cascaded high-voltage large-capacity DC transformer topology,which can effectively meet the requirements for the connection and transmission of renewable energy such as photovoltaic system.This topology adopts three single-phase cascaded modular multilevel converter(MMC)on the high-voltage side and a three-phase MMC on the mediumvoltage side.The DC capacitance of the power module can be effectively reduced through the 400 Hz intermediate-frequency transformer for electrical isolation.In order to improve the reliability of the topology operation by solving the capacitor voltage balance difficulties between the bridge arms on the high-voltage side,a decoupling control strategy for the high-voltage and medium-voltage sides is proposed.A 5-layer bridge arm capacitor voltage control scheme including bridge arm DC and intermediate-frequency circulating current control is adopted on the high-voltage side,and the intermediate-frequency AC voltage is established through three single-phase V/f closed-loop control.The medium-voltage side adopts double-sequence current control with additional instantaneous current control under the static coordinate system to suppress the circulation current between the bridge arms.Finally,an electromagnetic transient simulation model is established,and the effectiveness of the proposed topology and control strategy is comprehensively verified through steady-state,dynamic,and transient experiments.

关 键 词：新能源 高压直流输电 直流变压器 模块化多电平换流器 中频变压器 

分 类 号：TM721.1[电气工程—电力系统及自动化] TM41