State Feedback Control of Brushless Doubly-Fed Wind Power Generator under Symmetrical Grid Voltage Drop
Nie Pengcheng1, Wu Wenhui2
1. Department of Electrical Machinery Huazhong University of Science and Technology Wuhan 430074 China; 2. EAST Group Limited by Share Ltd Dongguan 523808 China
Abstract:For the grid-connected wind power system with brushless doubly-fed generators (BDFG), the transient symmetrical drop of grid voltage is equivalent to a sudden impose of a reverse voltage source at the grid-connected point. As a matter of fact, there are some deficiencies in the current research on low voltage ride through of BDFG. To be specific, some literatures merely give theoretical research without optimization strategies, and in some other studies, the hardware equipment are installed to improve system performance, but it increased the system cost. What's more, there are no comparative experiments carried out in the other works. On this basis, the dynamic operation characteristics of the BDFG under transient symmetrical voltage drop are deeply studied in this paper. Moreover, an optimal control strategy, i.e., state feedback control, is proposed to improve the transient operation characteristics of the control system. Firstly, the simplified dynamic mathematical model of the BDFG after converting the rotor circuit is listed. Then, the steady-state current before the voltage drop as well as the transient current after the transient voltage drop are obtained. Afterwards, the current of the power winding (PW) and control winding (CW) after the transient voltage drop is solved by applying the superposition principle. It is observed from the results that the overshoots and oscillation time of the transient current are related to the generator parameters, the degree and phase of the voltage drop, as well as the rotor speed. However, the degree and the phase of grid voltage drop cannot be controlled for the operating wind power system with BDFG. Moreover, the generator speed could not change suddenly. In addition, the parameters of the generator is fixed after been manufactured. To improve the operation characteristics of the control system, the state model is further constructed regarding PW and CW current as state variables. Then, the state variables are added to the input through the feedback matrix. Therefore, the parameters of the generator system matrix, i.e., the equivalent parameters of the generator are changed. As a result, the pole distribution diagram shows that the poles under the state feedback strategy are significantly shifted to the left compared with the traditional control model. Finally, a simulation case is conducted with the grid voltage drops to 20% under the rated working condition. The experimental waveform shows that the overshoot of the generator physical quantity with the proposed state feedback control is significantly smaller than which with the traditional control strategy. What's more, the oscillation duration is shortened while the requirements of power devices are met. In summary, the anti-disturbance ability of the whole control system is enhanced with state feedback control method. According to the experimental results, it is concluded that the parameters of the original system matrix of the BDFG is revised by introducing the state feedback control. Essentially, the negative real part of the eigenvalue and the transient coefficient of the output are changed. In the view of physical sense, it is equivalent to changing the equivalent resistance and inductance of the generator, which further changes the attenuation time constant and transient reactance of the PW and CW. Therefore, when the grid voltage drops suddenly, this strategy can effectively reduce the peak value of the oscillating current of the stator PW and CW. On this basis, the convergence time is shorten, and the oscillation as well as overshoot of the system are optimized. In conclusion, the effectiveness and practicability of the introduction of state feedback strategy have been verified.
聂鹏程, 吴文辉. 电网电压对称跌落时无刷双馈风力发电机的状态反馈控制[J]. 电工技术学报, 2023, 38(17): 4610-4620.
Nie Pengcheng, Wu Wenhui. State Feedback Control of Brushless Doubly-Fed Wind Power Generator under Symmetrical Grid Voltage Drop. Transactions of China Electrotechnical Society, 2023, 38(17): 4610-4620.
[1] 阚超豪, 鲍习昌, 金科, 等. 绕线转子无刷双馈电机多谐波联合起动过程中磁动势及性能分析[J]. 电工技术学报, 2020, 35(3): 481-493. Kan Chaohao, Bao Xichang, Jin Ke, et al.Analysis of magnetomotive force and performance during starting process of wound-rotor brushless doubly-fed machine with combined multi-harmonic fields[J]. Transactions of China Electrotechnical Society, 2020, 35(3): 481-493. [2] 李珍平, 王雪帆, 陈曦, 等. 无刷双馈电机的双馈与异步起动控制策略[J]. 电工技术学报, 2022, 37(14): 3576-3586. Li Zhenping, Wang Xuefan, Chen Xi, et al.Doubly fed and asynchronous starting control strategies of brushless doubly fed machine[J]. Transactions of China Electrotechnical Society, 2022, 37(14): 3576-3586. [3] 许利通, 程明, 魏新迟, 等. 考虑损耗的无刷双馈风力发电系统功率反馈法最大功率点跟踪控制[J]. 电工技术学报, 2020, 35(3): 472-480. Xu Litong, Cheng Ming, Wei Xinchi, et al.Power signal feedback control of maximum power point tracking control for brushless doubly-fed wind power generation system considering loss[J]. Transactions of China Electrotechnical Society, 2020, 35(3): 472-480. [4] 夏超英, 张耀华, 郭海宇. 无刷双馈电机反馈线性化控制方法[J]. 电工技术学报, 2020, 35(7): 1387-1397. Xia Chaoying, Zhang Yaohua, Guo Haiyu.Feedback linearization control approach of brushless doubly fed machine[J]. Transactions of China Electrotechnical Society, 2020, 35(7): 1387-1397. [5] Sadeghi R, Madani S M, Lipo T A, et al.Voltage-dip analysis of brushless doubly fed induction generator using reduced T-model[J]. IEEE Transactions on Industrial Electronics, 2019, 66(10): 7510-7519. [6] Tohidi S, Oraee H, Zolghadri M R, et al.Analysis and enhancement of low-voltage ride-through capability of brushless doubly fed induction generator[J]. IEEE Transactions on Industrial Electronics, 2013, 60(3): 1146-1155. [7] Long Teng, Shao Shiyi, Malliband P, et al.Crowbarless fault ride-through of the brushless doubly fed induction generator in a wind turbine under symmetrical voltage dips[J]. IEEE Transactions on Industrial Electronics, 2013, 60(7): 2833-2841. [8] Shao Shiyi, Long Teng, Abdi E, et al.Symmetrical low voltage ride-through of the brushless doubly-fed induction generator[C]//IECON 2011-37th Annual Conference of the IEEE Industrial Electronics Society, Melbourne, VIC, Australia, 2011: 3209-3214. [9] Huang Jiejie, Li Shenghu.Analytical expression for LVRT of BDFIG with enhanced current control to CW and reactive power support from GSC[J]. International Journal of Electrical Power & Energy Systems, 2018, 98: 243-255. [10] Lu Min, Chen Yu, Zhang Debin, et al.Virtual synchronous control based on control winding orientation for brushless doubly fed induction generator (BDFIG) wind turbines under symmetrical grid faults[J]. Energies, 2019, 12(2): 319. [11] Zhang Ailing, Chen Zhengfang, Gao Ruozhong, et al.Crowbarless symmetrical low-voltage ride through based on flux linkage tracking for brushless doubly fed induction generators[J]. IEEE Transactions on Industrial Electronics, 2020, 67(9): 7606-7616. [12] 于淼, 李京霖. 基于状态反馈解耦控制的含DFIG电力系统低频振荡抑制研究[J]. 可再生能源, 2022, 40(2): 214-221. Yu Miao, Li Jinglin.Research on low frequency oscillation suppression of power system with DFIG based on state feedback decoupling control[J]. Renewable Energy Resources, 2022, 40(2): 214-221. [13] Debouza M, Errouissi R, Al-Durra A, et al.Design and implementation of a robust state-feedback control law for a grid-connected doubly fed induction generator wind turbine[C]//5th IET International Conference on Renewable Power Generation (RPG), London, UK, 2016: 1-6. [14] Bhattarai R, Gurung N, Thakallapelli A, et al.Reduced-order state observer-based feedback control methodologies for doubly fed induction machine[J]. IEEE Transactions on Industry Applications, 2018, 54(3): 2845-2856. [15] Apte A, Joshi V A, Mehta H, et al.Disturbance-observer-based sensorless control of PMSM using integral state feedback controller[J]. IEEE Transactions on Power Electronics, 2020, 35(6): 6082-6090. [16] Yao Yu, Huang Yunkai, Peng Fei, et al.Position sensorless drive and online parameter estimation for surface-mounted PMSMs based on adaptive full-state feedback control[J]. IEEE Transactions on Power Electronics, 2020, 35(7): 7341-7355. [17] Ouyang Jinxin, Tang Ting, Diao Yanbo, et al.Control method of doubly fed wind turbine for wind speed variation based on dynamic constraints of reactive power[J]. IET Renewable Power Generation, 2018, 12(9): 973-980. [18] 徐伟, 陈俊杰, 刘毅, 等. 无刷双馈独立发电系统的改进无参数预测电流控制[J]. 电工技术学报, 2021, 36(19): 4002-4015. Xu Wei, Chen Junjie, Liu Yi, et al.Improved nonparametric predictive current control for standalone brushless doubly-fed induction generators[J]. Transactions of China Electrotechnical Society, 2021, 36(19): 4002-4015. [19] Sadeghi R, Madani S M, Ataei M.A new smooth synchronization of brushless doubly-fed induction generator by applying a proposed machine model[J]. IEEE Transactions on Sustainable Energy, 2018, 9(1): 371-380. [20] Zhang Fengge, Zhu Liancheng, Jin Shi, et al.Controller strategy for open-winding brushless doubly fed wind power generator with common mode voltage elimination[J]. IEEE Transactions on Industrial Electronics, 2019, 66(2): 1098-1107. [21] Hemanth Kumar M B, Saravanan B, Sanjeevikumar P, et al. Review on control techniques and methodologies for maximum power extraction from wind energy systems[J]. IET Renewable Power Generation, 2018, 12(14): 1609-1622. [22] 王增平, 李菁, 郑涛, 等. 不同撬棒保护投入时刻下双馈风电机组短路电流计算分析[J]. 电力系统保护与控制, 2017, 45(5): 109-117. Wang Zengping, Li Jing, Zheng Tao, et al.Calculation and analysis of three-phase short-circuit current of doubly fed wind turbine considering different crowbar protection insertion time[J]. Power System Protection and Control, 2017, 45(5): 109-117.