Energy Storage Science and Technology ›› 2022, Vol. 11 ›› Issue (5): 1512-1522.doi: 10.19799/j.cnki.2095-4239.2021.0461

• Energy Storage System and Engineering • Previous Articles     Next Articles

Parameter adaptive backstepping control of bidirectional DC-DC converter for DC microgrid energy storage device

Jingchao SHEN1(), Jian HU1(), Jingliang HU2, Ticao JIAO1, Xiaomei QI1, Yunpeng WANG1, Di YU1, Shangqi LIU1   

  1. 1.School of Electrical and Electronics Engineering, Shandong University of Technology, Zibo 255000, Shandong, China
    2.Qingdao Branch of China Classification Society, Qingdao 266034, Shandong, China
  • Received:2021-09-02 Revised:2021-11-08 Online:2022-05-05 Published:2022-05-07
  • Contact: Jian HU E-mail:shenjingchaosdut@163.com;hujian@sdut.edu.cn

Abstract:

The energy storage device is the key to supporting the flexibility of the microgrid. Because it contains a large number of electronic devices, the DC microgrid with energy storage devices shows nonlinear characteristics. Furthermore, the parameters are time-varying. To suppress the fluctuation of bus voltage caused by the power fluctuation of distributed power sources in an isolated DC microgrid, a battery is used as the power balance device of the system, and the charge-discharge controller of the battery is designed based on the parameter adaptive backstepping method. First, a mathematical model of the energy storage system composed of a battery and a buck/boost converter is established using Thevenin's equivalent model. Thereafter, the time-varying parameters during the operation of the model are regarded as unknown, and the unknown parameters are estimated online and in real-time by using the principle of parameter adaptation. The backstepping controller, which is based on parameter estimation and Lyapunov control theory, is designed recursively to regulate the charging and discharging processes of energy storage devices and balance the power between sources and loads of DC microgrids. The simulation result shows that in the case of insufficient illumination, the energy storage device keeps discharging and stabilizing the voltage. When compared with the traditional linear PI controller and exact feedback linearization controller, an adaptive backstepping controller reduces bus voltage regulation time by 0.120 s and 0.045 s respectively, and the fluctuation of the bus voltage is reduced by 3.1% and 2.9%. respectively. In the case of sufficient illumination, the energy storage device can be charged smoothly. Compared with the backstepping controller based on fixed parameters, the response is 0.04 s faster and the voltage deviation is 0.8% smaller. The result also reveals that the backstepping controller based on the optimal parameter estimates can adjust the energy storage device to switch between charging and discharging states flexibly, and maintain the bus voltage well when the power of the distributed PV fluctuates or even completely cuts off. Furthermore, when the parameters of the system are perturbed, the robustness improves.

Key words: energy storage device, DC microgrid, bidirectional DC-DC converter, parameter adaptive, backstepping control

CLC Number: