Double Closed-Loop Robust Control Strategy of DC Microgrid System Based on Variable Gain Fast Super-Twisting Algorithm

Aiming at the problems of intermittent distributed generation and load disturbance in DC microgrid system, a double closed-loop high-order sliding mode robust control strategy based on variable gain fast super-twisting (VGFST) algorithm is designed in this paper. First, The VGFST control strategy introduces the fast terminal sliding mode approach law into the ordinary super twist control approach law, which speeds up the convergence speed of bus voltage tracking error. Then the double-layer adaptive law of equivalent control is used to adjust the gain to ensure that the gain of the controller is as small as possible. In addition, by linearizing the inner loop control, the problem of complex parameter design of outer loop nonlinear algorithm caused by the nonlinear characteristics of inner loop and converter in the application of bidirectional DC/DC converter is solved, so that the outer loop of the system can also easily use VGFST nonlinear algorithm, which further improves the robustness of the system. Finally, the effectiveness of the proposed control strategy is verified in a typical islanded DC microgrid simulation environment and the hardware in the loop experimental environment.

I. Introduction

To mitigate global warming and tackle climate change, China proposed "carbon neutrality and emission peak". Obviously, the microgrid is the appropriate solution to achieve dual carbon policy, which has good compatibility and wide acceptance for clean energy [1]. Compared with other forms of microgrid, DC microgrid has more superior performances in transmission capacity, power supply quality and system controllability. In addition, DC microgrid has many advantages, such as no consideration of reactive power balance, voltage frequency and phase tracking [2].