Analysis and Control of DC Side Voltage Fluctuation Characteristics under Unbalanced Fault of AC Side in AC/DC Distribution Network

doi:10.12204/j.issn.1000-7229.2021.11.010

Abstract

Abstract:

DC distribution network, with its advantage of efficient absorption of direct current energy, will become an important way of connecting the future distributed generators. However, the unbalanced faults of the AC distribution networks will cause the voltage fluctuation of the DC distribution networks, which will harm the normal operation of the DC distribution system. To tackle the problem aforementioned, this paper firstly analyzes the characteristics of active power and DC voltage fluctuations in the case of single-phase-to-ground fault in AC distribution network, especially deduces the expression of instantaneous active power of filter inductance, and points out that the instantaneous active power of filter inductance is the important cause of DC voltage fluctuation. Secondly, an improved phase lock loop (PLL) is proposed to track the phase of positive-sequence voltage. The proposed method only redesigns the compensator of the traditional PLL, which is clear in principle and easy to implement. Finally, a simulation model of typical two-terminal AC-DC distribution system is built in PSCAD/EMTDC to verify the correctness of the theoretical analysis and the effectiveness of the proposed control method.

Key words: AC/DC distribution network, unbalanced fault, fault propagation mechanism, DC voltage fluctuation, improved phase lock loop

CLC Number:

TM713

WANG Wei, GONG Cheng, CAO Wenyuan, DONG Nan, LIU Huizhen, HAN Minxiao. Analysis and Control of DC Side Voltage Fluctuation Characteristics under Unbalanced Fault of AC Side in AC/DC Distribution Network[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(11): 90-99.

Figures/Tables 10

Fig.1 Topology of AC/DC distribution network

Fig.2 Equivalent topology diagram of MMC

Fig.3 Control block diagram of PLL

Fig.4 Open-loop bode plot of PLL

Fig.5 Scheme of positive and negative-sequence current decomposition

Fig.6 Control block diagram of positive-sequence current loop

Fig.7 Control block diagram of negative-sequence current loop

Table 1 Circuit and control parameters

Fig.8 Voltage waveforms of fault point and the PLL

Fig.9 Fault characteristics of AC/DC distribution network

References 25

[1]	廖鸿图, 黄益宏, 施亦治, 等. 含光储联合体的交直流配电网双层两阶段鲁棒优化运行策略[J]. 电力建设, 2020, 41(3): 110-118.
	LIAO Hongtu, HUANG Yihong, SHI Yizhi, et al. A bi-level two-stage robust optimal operation strategy for AC and DC distribution network with photovoltaic and energy storage[J]. Electric Power Construction, 2020, 41(3): 110-118.
[2]	韩民晓, 谢文强, 曹文远, 等. 中压直流配电网应用场景与系统设计[J]. 电力系统自动化, 2019, 43(23): 2-11, 89.
	HAN Minxiao, XIE Wenqiang, CAO Wenyuan, et al. Application scenarios and system design of medium-voltage DC distribution network[J]. Automation of Electric Power Systems, 2019, 43(23): 2-11, 89.
[3]	曹文远, 韩民晓, 谢文强, 等. 城市配网改造下中压直流配电网的供电能力分析[J]. 现代电力, 2018, 35(2): 56-63.
	CAO Wenyuan, HAN Minxiao, XIE Wenqiang, et al. Research on the power supply capacity of medium voltage DC distribution network in urban distribution network transformation[J]. Modern Electric Power, 2018, 35(2): 56-63.
[4]	马钊, 焦在滨, 李蕊. 直流配电网络架构与关键技术[J]. 电网技术, 2017, 41(10): 3348-3357.
	MA Zhao, JIAO Zaibin, LI Rui. Network structures and key technologies of DC distribution systems[J]. Power System Technology, 2017, 41(10): 3348-3357.
[5]	王肖肖, 韩民晓, 曹文远, 等. 多电压等级交直流配电系统潮流分析[J]. 电力建设, 2020, 41(10): 38-46.
	WANG Xiaoxiao, HAN Minxiao, CAO Wenyuan, et al. Power flow analysis of AC/DC distribution system with multiple voltage levels[J]. Electric Power Construction, 2020, 41(10): 38-46.
[6]	王强钢, 周念成, 颜伟, 等. 电网电压不平衡下光伏发电系统的改进功率控制[J]. 中国电机工程学报, 2013, 33(S1): 30-37.
	WANG Qianggang, ZHOU Niancheng, YAN Wei, et al. Improved power control of photovoltaic generation system under unbalanced grid voltage conditions[J]. Proceedings of the CSEE, 2013, 33(S1): 30-37.
[7]	吴凤江, 孙醒涛. 直流微电网中光伏发电系统的比例-积分-谐振控制[J]. 电网技术, 2014, 38(2): 275-280.
	WU Fengjiang, SUN Xingtao. Proportional-integral-resonant control of photovoltaic generation system in DC microgrid[J]. Power System Technology, 2014, 38(2): 275-280.
[8]	潘霄, 梁毅, 张娜, 等. 电压跌落下MMC-HCVD负序电流抑制策略研究[J]. 电网与清洁能源, 2020, 36(7): 38-43, 56.
	PAN Xiao, LIANG Yi, ZHANG Na, et al. Research on control strategy of negative sequence current suppression of MMC-HCVD under voltage drop[J]. Power System and Clean Energy, 2020, 36(7): 38-43, 56.
[9]	SAEEDIFARD M, IRAVANI R. Dynamic performance of a modular multilevel back-to-back HVDC system[J]. IEEE Transactions on Power Delivery, 2010, 25(4): 2903-2912. doi: 10.1109/TPWRD.2010.2050787 URL
[10]	许阔, 王婉君, 贾利虎, 等. 混合微电网交流不对称故障对直流系统的影响[J]. 中国电机工程学报, 2018, 38(15): 4429-4437, 4643.
	XU Kuo, WANG Wanjun, JIA Lihu, et al. Influence of AC unbalanced faults on DC system of hybrid AC/DC microgrid[J]. Proceedings of the CSEE, 2018, 38(15): 4429-4437, 4643.
[11]	朱永强, 刘康, 张泉, 等. 混合微电网交流侧故障传播机理及抑制方法[J]. 电机与控制学报, 2020, 24(4): 1-11.
	ZHU Yongqiang, LIU Kang, ZHANG Quan, et al. Fault propagation mechanism and suppression method on AC side of hybrid microgrid[J]. Electric Machines and Control, 2020, 24(4): 1-11.
[12]	SONG H S, NAM K. Dual current control scheme for PWM converter under unbalanced input voltage conditions[J]. IEEE Transactions on Industrial Electronics, 1999, 46(5): 953-959. doi: 10.1109/41.793344 URL
[13]	贾利虎, 杜少飞, 朱永强. 混合微电网交流侧不对称电压引起的直流侧功率波动分析及解决措施[J]. 现代电力, 2017, 34(1): 50-54.
	JIA Lihu, DU Shaofei, ZHU Yongqiang. Analysis of power fluctuation at DC side caused by unbalanced AC voltage of hybrid microgrid and relative solving measures[J]. Modern Electric Power, 2017, 34(1): 50-54.
[14]	高一波, 徐习东, 金阳忻, 等. 交流侧接地故障对直流配电网电压平衡影响[J]. 电网技术, 2014, 38(10): 2665-2670.
	GAO Yibo, XU Xidong, JIN Yangxin, et al. Impact on the voltage balancing of DC distribution network under AC side grounding fault[J]. Power System Technology, 2014, 38(10): 2665-2670.
[15]	周永荣, 秦文康, 葛佳盛, 等. 柔性直流配电系统换流器交流侧接地故障的分析[J]. 电力系统保护与控制, 2020, 48(19): 160-167.
	ZHOU Yongrong, QIN Wenkang, GE Jiasheng, et al. Analysis of grounding fault on the AC side of converter station in a flexible DC distribution system[J]. Power System Protection and Control, 2020, 48(19): 160-167.
[16]	AJI H, NDREKO M, POPOV M, et al. Investigation on different negative sequence current control options for MMC-HVDC during single line to ground AC faults[C]// 2016 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe). Ljubljana, Slovenia: IEEE, 2016.
[17]	YAZDANI A, IRAVANI R. A unified dynamic model and control for the voltage-sourced converter under unbalanced grid conditions[J]. IEEE Transactions on Power Delivery, 2006, 21(3): 1620-1629. doi: 10.1109/TPWRD.2006.874641 URL
[18]	唐轶, 谢永强, 王扬, 等. 基于解耦双同步坐标变换的三相锁相环研究[J]. 电测与仪表, 2017, 54(8): 14-20.
	TANG Yi, XIE Yongqiang, WANG Yang, et al. Study on PLL based on decoupled double synchronous reference frame[J]. Electrical Measurement & Instrumentation, 2017, 54(8): 14-20.
[19]	朱晓荣, 刘世鹏, 张海宁, 等. 不平衡电网电压下光伏并网逆变器滑模直接电压/功率控制策略[J]. 电力系统保护与控制, 2016, 44(23): 133-140.
	ZHU Xiaorong, LIU Shipeng, ZHANG Haining, et al. Sliding mode control based direct voltage/power control strategy for PV grid connected inverter under unbalanced grid voltage[J]. Power System Protection and Control, 2016, 44(23): 133-140.
[20]	熊雄, 季宇, 李蕊, 等. 直流配用电系统关键技术及应用示范综述[J]. 中国电机工程学报, 2018, 38(23): 6802-6813, 7115.
	XIONG Xiong, JI Yu, LI Rui, et al. An overview of key technology and demonstration application of DC distribution and consumption system[J]. Proceedings of the CSEE, 2018, 38(23): 6802-6813, 7115.
[21]	刘国伟, 赵宇明, 袁志昌, 等. 深圳柔性直流配电示范工程技术方案研究[J]. 南方电网技术, 2016, 10(4): 1-7.
	LIU Guowei, ZHAO Yuming, YUAN Zhichang, et al. Study on demonstration project technical scheme of VSC-DC distribution system in Shenzhen[J]. Southern Power System Technology, 2016, 10(4): 1-7.
[22]	杨杰, 郑健超, 汤广福, 等. 电压源换相高压直流输电系统接地方式设计[J]. 中国电机工程学报, 2010, 30(19): 14-19.
	YANG Jie, ZHENG Jianchao, TANG Guangfu, et al. Grounding design analysis of VSC-HVDC system[J]. Proceedings of the CSEE, 2010, 30(19): 14-19.
[23]	YAZDANI A, IRAVANI R. Back-to-back HVDC conversion system[M]. John Wiley & Sons, Inc., 2010: 334-384.
[24]	曹文远, 韩民晓, 谢文强, 等. 基于扰动观测器的电压源型逆变器负载电流前馈控制及参数设计方法[J]. 电工技术学报, 2020, 35(4): 862-873.
	CAO Wenyuan, HAN Minxiao, XIE Wenqiang, et al. A disturbance-observer-based load current feedforward control and parameter design method for voltage-sourced inverter[J]. Transactions of China Electrotechnical Society, 2020, 35(4): 862-873.
[25]	许潇. 直流微网的电能质量调控及治理研究[D]. 北京: 北京交通大学, 2015.
	XU Xiao. Research on power quality control and correction of DC micro-grid[D]. Beijing: Beijing Jiaotong University, 2015.