A Method for Calculating P-V Droop Coefficients Based on Virtual Resistance

doi:10.12204/j.issn.1000-7229.2021.04.012

Abstract

Abstract:

Many studies about multi-terminal VSC systems are concentrated on calculating droop control coefficients. However, few methods have been used to obtain the coefficients applying the virtual resistance. According to the I-V droop control, a new P-V droop control method based on virtual resistance is proposed. Firstly, the relationship between the voltage on the DC side of VSC stations and the voltage of the common bus is analyzed in a radial DC system. Then, the relationship between VSC arm voltage and the DC voltage is obtained by imposing a virtual resistance. Considering the P-V droop equation, the method for calculating coefficients is given. Thereafter, the calculation limitations of the proposed method in extreme operating conditions are analyzed, and the resolvent is proposed which improves the control strategy. Finally, three types of control strategies, i.e., the ratio droop control, the adaptive droop control and the droop control based on virtual resistance, are simulated on a six-terminal radial VSC system. Simulation results show that, the proposed method has the advantages of smaller deviation of dc-side voltage and reasonable power distribution.

Key words: DC grid, virtual resistance, droop control, radial system

CLC Number:

TM734

CAO Xin, HAN Minxiao, ZHANG Mingyang, WEI Wei. A Method for Calculating P-V Droop Coefficients Based on Virtual Resistance[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(4): 105-112.

Figures/Tables 8

Fig.1 Radial topology of DC system

Fig.2 Equivalent model of DC system under present status and target status

Fig.3 P-V droop control based on virtual resistance

Fig.4 6-termianl radial VSC system

Table 1 Control strategy of the convertersm when simulation begins

Fig.5 Active power of the inverters based on three kinds of droop control coefficients

Fig.6 DC-side voltage of VSC4 and VSC6 based on three kinds of droop control coefficients

Fig.7 Droop control coefficients of VSC4 and VSC6

References 28

[1]	胡兆庆, 董云龙, 王佳成, 等. 高压柔性直流电网多端控制系统架构和控制策略[J]. 全球能源互联网, 2018,1(4):461-470.
	HU Zhaoqing, DONG Yunlong, WANG Jiacheng, et al. Flexible DC grid multi-terminal control and protection system framework and control strategy[J]. Journal of Global Energy Interconnection, 2018,1(4):461-470.
[2]	刘欣和, 张浩, 李道洋, 等. 柔性直流电网协调控制策略[J]. 南方电网技术, 2017,11(9):1-7.
	LIU Xinhe, ZHANG Hao, LI Daoyang, et al. Coordinated control strategy for VSC-HVDC power grid[J]. Southern Power System Technology, 2017,11(9):1-7.
[3]	汤广福, 罗湘, 魏晓光. 多端直流输电与直流电网技术[J]. 中国电机工程学报, 2013,33(10):8-17,24.
	TANG Guangfu, LUO Xiang, WEI Xiaoguang. Multi-terminal HDC and DC-grid technology[J]. Proceedings of the CSEE, 2013,33(10):8-17,24.
[4]	韩民晓, 文俊, 徐永海. 高压直流输电原理与运行[M]. 3版. 北京: 机械工业出版社, 2019: 267-274.
[5]	邓旗, 张英敏, 曾琦, 等. 一种VSC-MTDC系统的综合协调控制策略[J]. 电力建设, 2017,38(8):59-66.
	DENG Qi, ZHANG Yingmin, ZENG Qi, et al. Comprehensive coordination control strategy for VSC-MTDC system[J]. Electric Power Construction, 2017,38(8):59-66.
[6]	翟冬玲, 韩民晓, 马骏鹏, 等. 连接低惯量系统的VSC-MTDC的自适应下垂控制[J]. 电力自动化设备, 2019,39(2):128-134.
	ZHAI Dongling, HAN Minxiao, MA Junpeng, et al. Adaptive droop control of VSC-MTDC connected to low inertia system[J]. Electric Power Automation Equipment, 2019,39(2):128-134.
[7]	翟冬玲. 柔性直流送端系统的频率与阻尼特性研究[D]. 北京: 华北电力大学, 2019.
	ZHAI Dongling. Research on frequency and damping of AC system sending through VSC-HVDC[D]. Beijing: North China Electric Power University, 2019.
[8]	刘瑜超, 武健, 刘怀远, 等. 基于自适应下垂调节的VSC-MTDC功率协调控制[J]. 中国电机工程学报, 2016,36(1):40-48.
	LIU Yuchao, WU Jian, LIU Huaiyuan, et al. Effective power sharing based on adaptive droop control method in VSC multi-terminal DC grids[J]. Proceedings of the CSEE, 2016,36(1):40-48.
[9]	刘英培, 解赛, 梁海平, 等. 计及换流站间电压误差的VSC-MTDC系统自适应下垂控制[J]. 电工技术学报, 2020,35(15):3270-3280.
	LIU Yingpei, XIE Sai, LIANG Haiping, et al. Adaptive droop control strategy for VSC-MTDC system considering DC voltage errors among converter stations[J]. Transactions of China Electrotechnical Society, 2020,35(15):3270-3280.
[10]	罗永捷, 李耀华, 王平, 等. 多端柔性直流输电系统直流电压自适应下垂控制策略研究[J]. 中国电机工程学报, 2016,36(10):2588-2599.
	LUO Yongjie, LI Yaohua, WANG Ping, et al. DC voltage adaptive droop control of multi-terminal HVDC systems[J]. Proceedings of the CSEE, 2016,36(10):2588-2599.
[11]	陶艳, 刘天琪, 李保宏, 等. 高压柔性直流电网分层协同自适应下垂控制[J]. 电力系统自动化, 2018,42(18):70-76.
	TAO Yan, LIU Tianqi, LI Baohong, et al. Hierarchical coordinated adaptive droop control in flexible HVDC grid[J]. Automation of Electric Power Systems, 2018,42(18):70-76.
[12]	任敬国, 李可军, 张春辉, 等. 基于直流电压-有功功率特性的VSC-MTDC协调控制策略[J]. 电力系统自动化, 2015,39(11):8-15.
	REN Jingguo, LI Kejun, ZHANG Chunhui, et al. A coordinated control strategy for VSC-MTDC system based on DC voltage-active power characteristic[J]. Automation of Electric Power Systems, 2015,39(11):8-15.
[13]	熊凌飞, 韩民晓. 基于组合方式的多端柔性直流输电系统控制策略[J]. 电网技术, 2015,39(6):1586-1592.
	XIONG Lingfei, HAN Minxiao. A novel combined control strategy for VSC-MTDC[J]. Power System Technology, 2015,39(6):1586-1592.
[14]	熊凌飞. 多端直流输电系统自律分散控制策略研究[D]. 北京: 华北电力大学, 2016.
	XIONG Lingfei. Research on decentralized control of VSC-MTDC system[D]. Beijing: North China Electric Power University, 2016.
[15]	曾琦, 李兴源, 张立奎. 考虑运行损耗和功率裕度的VSC-MTDC系统改进优化下垂控制策略[J]. 高电压技术, 2016,42(10):3117-3125.
	ZENG Qi, LI Xingyuan, ZHANG Likui. Improved optimization droop control strategy taking into account the network loss and available headroom for VSC-MTDC system[J]. High Voltage Engineering, 2016,42(10):3117-3125.
[16]	陈蒙蒙, 高亮, 李盈含. 兼顾柔性直流配电系统经济成本的优化下垂控制策略[J]. 电力建设, 2020,41(3):119-126.
	CHEN Mengmeng, GAO Liang, LI Yinghan. Dual-objective optimal droop control strategy for flexible DC distribution systems[J]. Electric Power Construction, 2020,41(3):119-126.
[17]	成龙, 金国彬, 王利猛, 等. 考虑功率裕度和电压偏差的多端直流配电网自组织下垂控制[J]. 电力系统自动化, 2019,43(23):81-89.
	CHENG Long, JIN Guobin, WANG Limeng, et al. Self-organizing droop control of multi-terminal DC distribution network considering power margin and voltage deviation[J]. Automation of Electric Power Systems, 2019,43(23):81-89.
[18]	陈继开, 董飞飞, 王振浩, 等. 适用于功率波动的多端柔性直流系统改进下垂控制方法[J]. 电网技术, 2018,42(11):3708-3717.
	CHEN Jikai, DONG Feifei, WANG Zhenhao, et al. Research on improved droop control method of multi-terminal MMC-HVDC system suitable for power fluctuation[J]. Power System Technology, 2018,42(11):3708-3717.
[19]	吴杰, 王志新. 多端柔性直流输电系统的改进下垂控制策略[J]. 电工技术学报, 2017,32(20):241-250.
	WU Jie, WANG Zhixin. Improved droop control strategy for multi-terminal voltage source converter-HVDC[J]. Transactions of China Electrotechnical Society, 2017,32(20):241-250.
[20]	阎发友, 汤广福, 贺之渊, 等. 基于MMC的多端柔性直流输电系统改进下垂控制策略[J]. 中国电机工程学报, 2014,34(3):397-404.
	YAN Fayou, TANG Guangfu, HE Zhiyuan, et al. An improved droop control strategy for MMC-based VSC-MTDC systems[J]. Proceedings of the CSEE, 2014,34(3):397-404.
[21]	孙黎霞, 陈宇, 宋洪刚, 等. 适用于VSC-MTDC的改进直流电压下垂控制策略[J]. 电网技术, 2016,40(4):1037-1043.
	SUN Lixia, CHEN Yu, SONG Honggang, et al. Improved voltage droop control strategy for VSC-MTDC[J]. Power System Technology, 2016,40(4):1037-1043.
[22]	李海峰, 刘崇茹, 李庚银, 等. 适用于柔性高压直流输电网的直流电压下垂控制策略[J]. 电力系统自动化, 2016,40(21):40-46.
	LI Haifeng, LIU Chongru, LI Gengyin, et al. DC voltage droop-control strategy for VSC-based HVDC grid[J]. Automation of Electric Power Systems, 2016,40(21):40-46.
[23]	朱珊珊, 汪飞, 郭慧, 等. 直流微电网下垂控制技术研究综述[J]. 中国电机工程学报, 2018,38(1):72-84,344.
	ZHU Shanshan, WANG Fei, GUO Hui, et al. Overview of droop control in DC microgrid[J]. Proceedings of the CSEE, 2018,38(1):72-84,344.
[24]	杨捷, 金新民, 吴学智, 等. 一种适用于直流微电网的改进型电流负荷分配控制策略[J]. 中国电机工程学报, 2016,36(1):59-67.
	YANG Jie, JIN Xinmin, WU Xuezhi, et al. An improved load current sharing control method in DC microgrids[J]. Proceedings of the CSEE, 2016,36(1):59-67.
[25]	曹文远, 韩民晓, 谢文强, 等. 交直流配电网逆变器并联控制技术研究现状分析[J]. 电工技术学报, 2019,34(20):4226-4241.
	CAO Wenyuan, HAN Minxiao, XIE Wenqiang, et al. Analysis on research status of parallel inverters control technologies for AC/DC distribution network[J]. Transactions of China Electrotechnical Society, 2019,34(20):4226-4241.
[26]	张波, 李冬雪, 颜湘武, 等. 基于坐标变换的微源逆变器虚拟复阻抗功率分配方法[J]. 电工技术学报, 2019,34(S1):212-223.
	ZHANG Bo, LI Dongxue, YAN Xiangwu, et al. Virtual complex impedance power distribution method for micro-source inverter based on coordinate transformation[J]. Transactions of China Electrotechnical Society, 2019,34(S1):212-223.
[27]	CAO X, HAN M X, KHAN Z W, et al. Design and analysation of DC voltage synchronisation control for a VSC-MTDC based on virtual synchronous generator[J]. IET Generation, Transmission & Distribution, 2020,14(3):449-459. doi: 10.1049/gtd2.v14.3 URL
[28]	曹昕, 韩民晓, 周光阳, 等. 基于自律分散控制的网孔型直流电网下垂系数计算方法[J]. 电工技术学报, 2020,35(24):5164-5174.
	CAO Xin, HAN Minxiao, ZHOU Guangyang, et al. A new method to obtain the droop control coefficient in a meshed DC system based on automatically decentralized control[J]. Transactions of China Electrotechnical Society, 2020,35(24):5164-5174.