不对称电网电压下MMC-HVDC换流站环流抑制策略

doi:10.16180/j.cnki.issn1007-7820.2023.11.010

摘要/Abstract

摘要：

应用模块化多电平换流器技术的柔性直流输电系统在运行时存在桥臂环流问题。文中通过分析不对称电网电压下桥臂相单元的瞬时能量,得出桥臂环流存在2倍频正、负和零序交流分量与直流分量,且直流分量分布不相等。针对交流分量的精确控制问题,文中提出了基于期望瞬态幅值响应的交流控制器,并通过系统的开环与闭环特性分析,在理论上证明了其具有控制精度高、稳定性好等优点。进一步提出了基于此控制器的新型环流抑制策略,此策略可直接在abc三相静止坐标下对每相桥臂独立控制,无需坐标变换和锁相环,控制结构简单且可以同时消除2倍频正、负和零序环流。在MATLAB/Simulink仿真平台中搭建51电平背靠背输电系统模型,验证了该环流抑制策略的正确性与有效性。

关键词: 模块化多电平换流器, 柔性直流输电系统, 不对称电网电压, 桥臂环流, 期望瞬态幅值响应, 开环与闭环特性, 环流抑制, MATLAB/Simulink

Abstract:

The flexible DC transmission system using modular multilevel converter technology has the problem of bridge arm circulation when the system is running. By analyzing the instantaneous energy of the bridge arm under the asymmetric grid voltage, it is concluded that there are double-frequency positive, negative and zero sequence AC components and DC components in the bridge arm circulating current, and the distribution of the DC components is not equal. To solve the problem of the precise control of AC components, an AC controller based on expected transient amplitude response is proposed. By analyzing the open and closed loop characteristics of the system, it is theoretically proved that the AC controller has the advantages of high control accuracy and good stability. Furtherly, a new circulating current suppression strategy based on the controller is proposed. This strategy can directly control the bridge arm of each phase independently in abc three-phase stationary coordinate without coordinate transformation and phase lock loop. The control structure is simple and can eliminate double-frequency positive, negative and zero sequence circulations at the same time. A 51-level back-to-back transmission system model is built in the MATLAB/Simulink simulation platform, and the correctness and effectiveness of the circulation suppression strategy are verified.

Key words: modular multilevel converter, flexible DC transmission system, asymmetric grid voltage, bridge arm circulation, expected transient amplitude response, open and closed loop characteristics, circulating current suppression, MATLAB/Simulink

中图分类号:

TP202+.1

王忠洋,姚磊,李天皓,高尚. 不对称电网电压下MMC-HVDC换流站环流抑制策略[J]. 电子科技, 2023, 36(11): 66-75.

WANG Zhongyang,YAO Lei,LI Tianhao,GAO Shang. Circulating Current Suppression Strategy for MMC-HVDC Converter Station under Asymmetric Grid Voltage[J]. Electronic Science and Technology, 2023, 36(11): 66-75.

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参数	数值
额定容量S_N/MVA	220(1 pu)
额定功率P_N/MW	220
负载有功功率P_L/MW	110
负载无功功率Q_L/Mvar	0
换流变压器1变比/kV	400/66
换流变压器2变比/kV	66/18
额定直流电压/kV	135
桥臂等效电阻R₀/Ω	0.03
桥臂电感L₀/mH	16.4
子模块电容C₀/μF	10 480
子模块数量N	50
时间常数τ/s	0.001