A high-order sliding mode controller for a robust bi-directional DC-DC converter

With the development of renewable energy technologies, bidirectional DC-DC converters (BDC) are increasingly used in aerospace, navigation, and electric vehicles, due to their bidirectional power flow characteristics. However, the DC bus voltage of a renewable power system is seriously disturbed by the intermittent input of energy, random disturbance of the load, and power flow switching. Therefore, the robustness requirement of the system is high. In the paper, a robust control system was designed for a Buck-Boost BDC driven by complementary PWM, based on the double closed-loop Super-Twisting (ST) control, one kind of high order sliding mode control (HOSMC). In the paper, it is clarified the fundamental reason why Super-Twisting has the advantage of robustness and rapidity over traditional PI control. In addition, based on a quadratic-like Lyapunov function, the conditions for the system to converge in finite time are given. Particularly, the estimated value of the algorithm convergence time is also given. In addition, in the application of converter, the design of parameters of outer loop non-linear algorithm is complicated because of the non-linearity of the inner loop and converter. By linearizing the inner loop control with equivalent control, the problem is solved and the robustness of the system is further improved. Moreover, the controller is realized based on the dSPACE semi-physical platform. Combining with the hardware circuits, the physical experiment platform is built. Finally, compared with traditional PI dual-loop control, the step load disturbance and switching power flow were tested separately, and the effectiveness of the proposed controller in the paper is verified by simulation and experiments.