Robust Predictive Current Control for Grid Synchronization and Power Generation of Cascaded Brushless Doubly-Fed Generators Based on Extended State Observer
Yang Changshan, Zhang Yongchang, Jiang Tao
School of Electrical and Electronic Engineering North China Electric Power University Beijing 102206 China
Abstract：The cascaded brushless doubly-fed generator (CBDFG) comprises two coaxial wound rotor induction motors, and its rotor windings are directly connected to eliminate the need for brushes and slip rings. Therefore, it has the advantages of long service life, high reliability, and low maintenance cost. CBDFG can be used for independent generation and grid-connected generation, which has broad prospects in wind power and hydroelectric power generation. At present, vector control and deadbeat control are commonly used to control the CBDFG. Because the above two methods use a large number of motor parameters, when the machine parameters in controllers are different from the actual values due to temperature, saturation, and other reasons, the control effects have varying degrees of deterioration. Therefore, this paper proposes an extended state observer (ESO) based robust predictive current control (RPCC) method for CBDFG. Firstly, the proposed RPCC can be applied to grid synchronization and power generation processes. The only difference between the two processes is the reference value calculation of the control winding current. In the process of grid synchronization, because the power side does not emit power, the virtual flux is needed to calculate the reference value of the control winding current. During the power generation process, the reference value of the control winding current is calculated directly according to the power reference value. Secondly, the proposed RPCC is based on an ultra-local model and uses an ESO to rapidly estimate the total disturbance caused by model uncertainty. The ESO can extend the total disturbance to a new disturbance and feed this total disturbance back to the controlled system. Based on the state space equation of ESO, the closed-loop transfer function of the ESO for CBDFG is obtained, and the two parameters of ESO are simplified to one. Then, the control block diagram of the proposed RPCC in the z domain is given, and the parameters of ESO are designed according to the characteristic equation of the proposed RPCC. In addition, the parameter stability of the proposed ESO is analyzed. Finally, according to the designed ESO parameters and the obtained disturbance values, one-step delay compensation is carried out for the current value of the control winding, and deadbeat control is further incorporated to achieve fast and accurate control of the control winding current. Compared with the traditional field-oriented control and deadbeat control, the experimental results show that this method has good steady-state and dynamic waveforms when the motor parameters are accurate and maintains a good control effect when the CBDFG parameters change. This method has good parameter robustness. The switching frequency is usually set at several kHz to reduce the switching loss in an actual wind power system. The simulation results of the proposed RPCC at low switching frequencies show that although the decrease in switching frequency increases the current THD, it is still far less than 5%, which meets the grid-connection requirements.
杨长山, 张永昌, 蒋涛. 基于扩张状态观测器的级联无刷双馈电机并网同步和发电鲁棒预测电流控制[J]. 电工技术学报, 2023, 38(22): 6094-6103.
Yang Changshan, Zhang Yongchang, Jiang Tao. Robust Predictive Current Control for Grid Synchronization and Power Generation of Cascaded Brushless Doubly-Fed Generators Based on Extended State Observer. Transactions of China Electrotechnical Society, 2023, 38(22): 6094-6103.
[1] Liang Shuai, Jin Shi, Shi Long.Research on control strategy of grid-connected brushless doubly-fed wind power system based on virtual synchronous generator control[J]. CES Transactions on Electrical Machines and Systems, 2022, 6(4): 404-412. [2] 阚超豪, 鲍习昌, 王雪帆, 等. 无刷双馈电机的研究现状与最新进展[J]. 中国电机工程学报, 2018, 38(13): 3939-3959, 4036. Kan Chaohao, Bao Xichang, Wang Xuefan, et al.Overview and recent developments of brushless doubly-fed machines[J]. Proceedings of the CSEE, 2018, 38(13): 3939-3959, 4036. [3] 程明, 许利通, 曹政, 等. 级联式无刷双馈电机的矢量控制系统和功率流研究[J]. 电工技术学报, 2022, 37(20): 5164-5174. Cheng Ming, Xu Litong, Cao Zheng, et al.Study on vector control system and power flow of cascaded brushless doubly-fed induction generator[J]. Transa- ctions of China Electrotechnical Society, 2022, 37(20): 5164-5174. [4] 任泰安, 梁克靖, 王群京, 等. 差调制无刷双馈电机转子绕组设计及性能分析[J]. 电机与控制学报, 2022, 26(4): 57-65. Ren Taian, Liang Kejing, Wang Qunjing, et al.Rotor winding design and performance analysis of differ- ential modulation brushless doubly-fed machines[J]. Electric Machines and Control, 2022, 26(4): 57-65. [5] 程明, 韩鹏, 魏新迟. 无刷双馈风力发电机的设计、分析与控制[J]. 电工技术学报, 2016, 31(19): 37-53. Cheng Ming, Han Peng, Wei Xinchi.Design, analysis and control of brushless doubly-fed generators for wind power application[J]. Transactions of China Electrotechnical Society, 2016, 31(19): 37-53. [6] Cheng Ming, Luo Rensong, Wei Xinchi.Design and analysis of current control methods for brushless doubly fed induction machines[J]. IEEE Transactions on Industrial Electronics, 2019, 66(1): 717-727. [7] Esfandiari G, Ebrahimi M, Tabesh A.Instantaneous torque control method with rated torque-sharing ratio for cascaded DFIMs[J]. IEEE Transactions on Power Electronics, 2017, 32(11): 8671-8680. [8] Sadeghi R, Madani S M, Ataei M, et al.Super- twisting sliding mode direct power control of a brushless doubly fed induction generator[J]. IEEE Transactions on Industrial Electronics, 2018, 65(11): 9147-9156. [9] 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. [10] 魏新迟, 许利通, 骆仁松, 等. 考虑饱和效应的无刷双馈发电机功率模型预测控制[J]. 电工技术学报, 2021, 36(17): 3721-3729. Wei Xinchi, Xu Litong, Luo Rensong, et al.Model predictive power control of brushless doubly-fed induction generator considering saturation effect[J]. Transactions of China Electrotechnical Society, 2021, 36(17): 3721-3729. [11] 卜飞飞, 罗捷, 刘皓喆, 等. 双绕组感应发电机系统无差拍电流预测控制策略[J]. 电工技术学报, 2021, 36(24): 5213-5224. Bu Feifei, Luo Jie, Liu Haozhe, et al.Deadbeat predictive current control strategy of dual winding induction generator system[J]. Transactions of China Electrotechnical Society, 2021, 36(24): 5213-5224. [12] 章回炫, 范涛, 边元均, 等. 永磁同步电机高性能电流预测控制[J]. 电工技术学报, 2022, 37(17): 4335-4345. Zhang Huixuan, Fan Tao, Bian Yuanjun, et al.Predictive current control strategy of permanent magnet synchronous motors with high performance[J]. Transactions of China Electrotechnical Society, 2022, 37(17): 4335-4345. [13] Wei Xinchi, Cheng Ming, Zhu Jianguo, et al.Finite- set model predictive power control of brushless doubly fed twin stator induction generator[J]. IEEE Transactions on Power Electronics, 2019, 34(3): 2300-2311. [14] Li Xuan, Peng Tao, Dan Hanbing, et al.A modulated model predictive control scheme for the brushless doubly fed induction machine[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018, 6(4): 1681-1691. [15] Bhattarai R, Gurung N, Ghosh S, et al.Parametrically robust dynamic speed estimation based control for doubly fed induction generator[J]. IEEE Transactions on Industry Applications, 2018, 54(6): 6529-6542. [16] Errouissi R, Al-Durra A, Muyeen S M, et al.Offset- free direct power control of DFIG under continuous- time model predictive control[J]. IEEE Transactions on Power Electronics, 2017, 32(3): 2265-2277. [17] Zhang Yongchang, Jiang Tao, Jiao Jian.Model-free predictive current control of DFIG based on an extended state observer under unbalanced and dis- torted grid[J]. IEEE Transactions on Power Elec- tronics, 2020, 35(8): 8130-8139. [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 non- parametric predictive current control for standalone brushless doubly-fed induction generators[J]. Transa- ctions of China Electrotechnical Society, 2021, 36(19): 4002-4015. [19] Liu Feng, Liu Zhangwei, Mei Shengwei, et al.ESO- based inertia emulation and rotor speed recovery control for DFIGs[J]. IEEE Transactions on Energy Conversion, 2017, 32(3): 1209-1219. [20] Broekhof A, McMahon R, Tatlow M. Vector- controlled grid synchronization for the brushless doubly-fed induction generator[C]//7th IET Inter- national Conference on Power Electronics, Machines and Drives (PEMD 2014), Manchester, UK, 2014: 1-5. [21] Sadeghi R, Madani S M, Agha Kashkooli M R. Grid synchronization of brushless doubly fed induction generator using direct torque control[C]//2016 7th Power Electronics and Drive Systems Technologies Conference (PEDSTC), Tehran, Iran, 2016: 53-57.
2023, Vol. 38 
