Stability and Robustness Control Strategy of DC Microgrid Considering Constant Power Load
Zhang Zehua1,2, Song Guiying1,2, Zhang Xiaolu3, Zhou Jiyao1,2, Wang Ruimin1,2
1. State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin 300130 China; 2. Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province Hebei University of Technology Tianjin 300130 China; 3. North China Electric Power Research Institute Co. Ltd Beijing 100045 China
Abstract：The DC microgrid has many loads: constant impedance load (CIL) and constant power load (CPL). The negative impedance characteristic of CPL will reduce the system damping and cause the system to collapse. However, the traditional linear control only guarantees stability in the small neighborhood of the equilibrium point and needs to make a trade-off between the stability margin and the dynamic performance. In recent years, many nonlinear control methods have been proposed, but most require parameter design and general dynamic performance. In order to solve these problems, this paper proposes an adaptive backstepping control, which guarantees the global large signal stability and fast dynamic response of the system. Firstly, the model is transformed into Brunovsky's canonical form using the exact feedback linearization technique to solve the non-minimum phase problem and avoid the influence of parasitic resistance on the primary controller. Secondly, to improve the robustness of the system, an extended nonlinear disturbance observer and an input voltage observer based on the dynamic model of the converter are used to estimate and compensate for external disturbances, parasitic resistance, and lumped uncertainty disturbances online. The optimized adaptive backstepping control can operate with limited and imprecise initial parameters of the system. The large-signal stability of the controller is verified based on Lyapunov and mixed potential function theory. The design principle of controller parameters and the stability boundary diagram of the system are given to ensure global trajectory tracking and fast dynamic response of the output voltage. The simulation and hardware in the loop experiment of DC microgrid under various working conditions, compared with the literature in Ref.[22], show that when the input voltage step changes, the overshoot and recovery time are reduced by 81.25% and 88%, respectively, and the inductance current does not reverse overshoot. When the CPL step changes, its overshoot and recovery time are reduced by 41.89% and 75%, respectively. When the CIL step changes, the overshoot and recovery time are reduced by 41.56% and 75%, respectively. At the same time, the proposed control is robust to model parameter uncertainties and parasitic parameters, which can be better applied to industrial applications under various harsh conditions. In addition, the proposed control is tested for controller switching and large signal stability. Compared with the classical PI control, the overshoot and recovery time of the proposed control are reduced by 57.14% and 92.5%, respectively. Finally, the effectiveness and superiority of the proposed control are further verified through the DC microgrid experimental platform. The following conclusions are drawn from the simulation and experimental results: (1) Compared with BSC+NDO, it reduces the parameters required for controller design and the dependence on sensors, considers the system parasitic parameter interference, and has good stability and robustness. (2) Compared with classical PI control, the proposed control can stabilize the limit cycle oscillation system and has a better dynamic response. (3) A mixed potential function large signal stability criterion for nonlinear control is proposed, and the controller parameter design criteria and large signal stability boundary diagram are provided.
张泽华, 宋桂英, 张晓璐, 周继尧, 王瑞民. 考虑恒功率负载的直流微电网稳定性与鲁棒性控制策略[J]. 电工技术学报, 2023, 38(16): 4391-4405.
Zhang Zehua, Song Guiying, Zhang Xiaolu, Zhou Jiyao, Wang Ruimin. Stability and Robustness Control Strategy of DC Microgrid Considering Constant Power Load. Transactions of China Electrotechnical Society, 2023, 38(16): 4391-4405.
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