An adaptive droop strategy for microgrid based on virtual impedance
XUE Jiaxiang, ZHANG Xiangying, ZHOU Gang
1. School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;
2. Dongguan Juda Electronics Co., Ltd., Dongguan 523070, China
Abstract: In order to reduce the influence of reactive power circulation on system stability in traditional microgrid droop control, an adaptive droop strategy based on virtual impedance was proposed. The characteristic roots of the closed-loop transfer function are analyzed and the appropriate virtual impedance parameters are selected. To solve the problem of high order harmonic interference in the differential part of virtual impedance, the SOGI module is proposed, and the experiment proves that it has good filtering ability and the characteristics of generating orthogonal signals. A voltage adaptive compensation link is proposed to solve the problem of voltage drop increase caused by virtual impedance, and the simulation shows that the voltage drop can be compensated for different loads. Aiming at the problem of frequency fluctuation caused by power disturbance, a frequency adaptive adjustment link is proposed. The frequency change value and frequency change rate were divided into five cases, and the amplitude adjustment parameters were adjusted adaptively to reduce the frequency disturbance peak value of 1.4 Hz and the recovery time of 0.045 s. Through the multi-machine parallel experiment, the output reactive power difference of each machine is 39.096 var and 150.258 var, and the equalization effect is good. This paper not only studies the power distribution of microgrid, but also provides a new solution for the application of virtual impedance.
Keywords: microgrid droop;virtual impedance;SOGI;voltage compensation;frequency regulation
2023, 49(9):97-103,110  收稿日期: 2022-3-25;收到修改稿日期: 2022-6-4
基金项目: 国家自然科学基金资助（51875213）；2015 东莞市引进第三批创新科研团队项目（2017360004004）；东莞市科技装备动员项目（KZ2019-6，KZ2020-01）
作者简介: 薛家祥（1963-），男，江苏徐州市人，教授，博导，主要从事光伏离网，并网逆变器及其分布式发电系统，数字化开关 电源及智能控制的研究。
参考文献
[1] 齐山成, 姚景昆, 刘毅. 大规模风电并网柔性调度模型与策略[J]. 中国测试, 2021, 47(8): 103-108
[2] LI X, ZHAO S, WANG J S, et al. Reactive power distribution strategy and droop control method based on virtual impedance in microgrid[J]. IAENG International Journal of Applied Mathematics, 2020, 50(3): 678-689
[3] MASOUD D, MAJID D. Improving the sharing of reactive power in an islanded microgrid based on adaptive droop control with virtual impedance[J]. Automatic Control and Computer Sciences, 2021, 55(2): 155-166
[4] LI Y, LIU S, ZHU J, et al. Novel MTDC droop scheme with decoupled power control for enhancing frequency stabilities of weak AC systems[J]. IET Renewable Power Generation, 2020, 14(11): 2007-2016
[5] 李晓晓, 王晓兰, 魏腾飞. 一致性控制的交直流微源混联直流微电网阻抗模型及小信号稳定性分析[J]. 高电压技术, 2019, 45(9): 2876-2883
[6] DENG W, DAI N, LAO K W, et al. A virtual-impedance droop control for accurate active power control and reactive power sharing using capacitive-coupling inverters[J]. IEEE Transactions on Industry Applications, 2020, 56(6): 6722-6733
[7] SUMAN M, SRIJA M, DIPANKAR D, et al. Study of dual active bridge with modified modulation techniques for reduced link current peak stress and harmonics losses in magnetics[J]. IEEJ Journal of Industry Applications, 2020, 56(5): 5035-5045
[8] LI X, CHEN G. Stability enhancement strategy of virtual synchronous generator for cascaded multilevel converter based energy storage system under weak grid conditions[J]. IET Renewable Power Generation, 2020, 14(5): 695-704
[9] ZHANG X, GAO Q, GUO Z, ZHANG H, et al. Coordinated control strategy for a PV-storage grid-connected system based on a virtual synchronous generator[J]. Global Energy Interconnection, 2020, 3(1): 51-59
[10] 陶海东, 胡海涛, 朱晓娟, 等. 车网耦合下的牵引供电系统谐振不稳定机理分析[J]. 中国电机工程学报, 2019, 39(8): 2315-2324
[11] 单锁兰, 谷志锋, 李宏城, 等. 混合储能系统分散自适应强扭曲虚拟阻抗控制[J]. 中国测试, 2021, 47(1): 127-132
[12] 陈少龙, 张兴, 郭梓暄, 等. 基于自适应虚拟阻抗的并网电流谐波抑制[J]. 电力电子技术, 2022, 56(2): 76-79
[13] 刘多禄, 马林, 王炳文. 风电并网引起潮流分布对电力系统小干扰功角稳定性的影响研究[J]. 中国测试, 2020, 46(10): 144-150
[14] 康慨, 张超, 张云龙, 等. 交直流混合微电网二次频率电压协调控制策略[J]. 武汉大学学报(工学版), 2021, 54(3): 239-246
[15] 陈晓祺, 贾宏杰, 陈硕翼, 等. 基于线路阻抗辨识的微电网无功均分改进下垂控制策略[J]. 高电压技术, 2017, 43(4): 1271-1279