Stability Analysis of Back-To-Back Converter with Bidirectional Power Flow

doi:10.12204/j.issn.1000-7229.2021.07.009

Abstract

Abstract:

As the key component of regional power grid interconnection, the stability of back-to-back converters is an important prerequisite to ensure the stable operation of regional power grids. In this paper, the stability of back-to-back converter with bidirectional power flow is studied mainly from the perspective of the DC terminal impedance of the converter. The results show that the stability of the back-to-back converter is better when power reverses. To alleviate the stability problem of the back-to-back converter caused by bidirectional power flow, the DC current inner loop is introduced into the inverter to reshape the AC/DC impedance of the inverter, which makes the DC terminal input impedance change from the original negative impedance in the low frequency band to the inductive impedance characteristics, so as to improve the stability margin of the back-to-back converter. Finally, the model of back-to-back converter is established in the Matlab/Simulink simulation platform for simulation verification, and the results verify the feasibility of the theoretical analysis and the proposed control scheme.

Key words: back-to-back converter, power flowing direction, impedance reshaping, DC current, stability.

CLC Number:

TM712

JIANG Yuxia, TIAN Yanjun, LI Yonggang. Stability Analysis of Back-To-Back Converter with Bidirectional Power Flow[J]. ELECTRIC POWER CONSTRUCTION, 2021, 42(7): 73-82.

Figures/Tables 20

Fig.1 Structure of a back-to-back converter

Fig.2 Equivalent schematic diagram of back-to-back converter

Fig.3 Block diagram of rectifier control

Fig.4 Bode plot of equivalent impedance on the DC-side of the rectifier

Fig.5 Block diagram of inverter control

Fig.6 Bode plot of equivalent impedance on the DC-side of the inverter

Fig.7 Bode plot of equivalent impedance on the AC-side of the inverter

Fig.8 Control block diagram of inverter under dc-current control scheme

Fig.9 Comparison of bode plot of DC-side impedance of inverter before and after optimization

Fig.10 Comparison of bode plot of AC-side impedance of inverter before and after optimization

Fig.11 Comparison of DC-side impedance of back-to-back converter under forward direction before and after optimization

Fig.12 Comparison of DC-side impedance of back-to-back converter under reverse direction before and after optimization

Fig.13 Comparison of bode plot of AC-side impedance of inverter under forward direction before and after optimization

Fig.14 Comparison of bode plot of AC-side impedance of inverter under reverse direction before and after optimization

Fig.15 Nyquist curves of the DC-link impedance ratio of back-to-back converter under the different directions

Fig.16 Bode plots of AC-side impedance of inverter

Table 1 AC-side phase margin of inverter

Table 2 Main topology parameters of back-to-back converter

Fig.17 Comparison of DC-side waveforms of back-to-back converter before and after optimization

Fig.18 AC-side power waveforms of inverter before and after optimization

References 20

[1]	SUN J, LI M J, ZHANG Z G, et al. Renewable energy transmission by HVDC across the continent: System challenges and opportunities[J]. CSEE Journal of Power and Energy Systems, 2017, 3(4):353-364. doi: 10.17775/CSEEJPES URL
[2]	陈国平, 李明节, 许涛, 等. 关于新能源发展的技术瓶颈研究[J]. 中国电机工程学报, 2017, 37(1):20-27.
	CHEN Guoping, LI Mingjie, XU Tao, et al. Study on technical bottleneck of new energy development[J]. Proceedings of the CSEE, 2017, 37(1):20-27.
[3]	DU E S, ZHANG N, HODGE B M, et al. The role of concentrating solar power toward high renewable energy penetrated power systems[J]. IEEE Transactions on Power Systems, 2018, 33(6):6630-6641. doi: 10.1109/TPWRS.2018.2834461 URL
[4]	DE PRADA M, IGUALADA L, CORCHERO C, et al. Hybrid AC-DC offshore wind power plant topology: Optimal design[J]. IEEE Transactions on Power Systems, 2015, 30(4):1868-1876. doi: 10.1109/TPWRS.2014.2354457 URL
[5]	ZENI L, ERIKSSON R, GOUMALATSOS S, et al. Power oscillation damping from VSC-HVDC connected offshore wind power plants[J]. IEEE Transactions on Power Delivery, 2016, 31(2):829-838. doi: 10.1109/TPWRD.2015.2427878 URL
[6]	姜玉霞, 田艳军, 李永刚. 背靠背变流器调节器参数及传输功率变化对阻抗稳定特性的影响及其改进控制策略[J]. 高电压技术, 2019, 45(9):2866-2875.
	JIANG Yuxia, TIAN Yanjun, LI Yonggang. Influence of back-to-back converter regulator parameters and transmission power variation on impedance stability and improved control strategy[J]. High Voltage Engineering, 2019, 45(9):2866-2875.
[7]	TIAN Y J, CHEN Z, DENG F J, et al. Active power and DC voltage coordinative control for cascaded DC-AC converter with bidirectional power application[J]. IEEE Transactions on Power Electronics, 2015, 30(10):5911-5925. doi: 10.1109/TPEL.2014.2375573 URL
[8]	田艳军, 彭飞, 王慧, 等. 输电系统中并网变流器优化双向功率稳定性差异的阻抗控制策略[J]. 高电压技术, 2020, 46(11):3734-3742.
	TIAN Yanjun, PENG Fei, WANG Hui, et al. Impedance control strategy for optimizing bidirectional power stability difference of grid-connected converters in transmission system[J]. High Voltage Engineering, 2020, 46(11):3734-3742.
[9]	TIAN Y J, LOH P C, DENG F J, et al. Impedance coordinative control for cascaded converter in bidirectional application[J]. IEEE Transactions on Industry Applications, 2016, 52(5):4084-4095. doi: 10.1109/TIA.2016.2564359 URL
[10]	张犁, 吴田进, 冯兰兰, 等. 模块化双向AC/DC变换器并联系统无缝切换控制[J]. 中国电机工程学报, 2012, 32(6):90-96.
	ZHANG Li, WU Tianjin, FENG Lanlan, et al. Seamless switching control for modular bi-directional AC/DC converter parallel systems[J]. Proceedings of the CSEE, 2012, 32(6):90-96.
[11]	刘子文, 苗世洪, 范志华, 等. 孤立交直流混合微电网双向AC/DC换流器功率控制与电压波动抑制策略[J]. 中国电机工程学报, 2019, 39(21):6225-6238.
	LIU Ziwen, MIAO Shihong, FAN Zhihua, et al. Power control and voltage fluctuation suppression strategy of the bidirectional AC/DC converter in the islanding hybrid microgrid[J]. Proceedings of the CSEE, 2019, 39(21):6225-6238.
[12]	ZHANG J P, LIU J Q, YANG J X, et al. An LLC-LC type bidirectional control strategy for an LLC resonant converter in power electronic traction transformer[J]. IEEE Transactions on Industrial Electronics, 2018, 65(11):8595-8604. doi: 10.1109/TIE.2018.2808917 URL
[13]	陈新, 张旸, 王赟程. 基于阻抗分析法研究光伏并网逆变器与电网的动态交互影响[J]. 中国电机工程学报, 2014, 34(27):4559-4567.
	CHEN Xin, ZHANG Yang, WANG Yuncheng. A study of dynamic interaction between PV grid-connected inverters and grid based on the impedance analysis method[J]. Proceedings of the CSEE, 2014, 34(27):4559-4567.
[14]	TIAN Y J, LOH P C, CHEN Z, et al. Impedance interactions in bidirectional cascaded converter[J]. IET Power Electronics, 2016, 9(13):2482-2491. doi: 10.1049/pel2.v9.13 URL
[15]	RYGG A, MOLINAS M. Apparent impedance analysis: A small-signal method for stability analysis of power electronic-based systems[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2017, 5(4):1474-1486. doi: 10.1109/JESTPE.2017.2729596 URL
[16]	AMIN M, MOLINAS M, LYU J, et al. Impact of power flow direction on the stability of VSC-HVDC seen from the impedance nyquist plot[J]. IEEE Transactions on Power Electronics, 2017, 32(10):8204-8217. doi: 10.1109/TPEL.2016.2608278 URL
[17]	MORTAZAVI H, MEHRJERDI H, SAAD M, et al. A monitoring technique for reversed power flow detection with high PV penetration level[J]. IEEE Transactions on Smart Grid, 2015, 6(5):2221-2232. doi: 10.1109/TSG.2015.2397887 URL
[18]	季宇, 王东旭, 吴红斌, 等. 提高直流微电网稳定性的有源阻尼方法[J]. 电工技术学报, 2018, 33(2):370-379.
	JI Yu, WANG Dongxu, WU Hongbin, et al. The active damping method for improving the stability of DC microgrid[J]. Transactions of China Electrotechnical Society, 2018, 33(2):370-379.
[19]	HEYDT G T. Thévenin’s theorem applied to the analysis of polyphase transmission circuits[J]. IEEE Transactions on Power Delivery, 2017, 32(1):72-77. doi: 10.1109/TPWRD.2016.2537264 URL
[20]	GARUFO A, CARLUCCIO G, FREEMAN J R, et al. Norton equivalent circuit for pulsed photoconductive antennas, part II: Experimental validation[J]. IEEE Transactions on Antennas and Propagation, 2018, 66(4):1646-1659. doi: 10.1109/TAP.2018.2800704 URL