In a photovoltaic DC microgrid, the intermittent power supply of the distributed generation and the fluctuation of the load power will cause the instability of the bus voltage. An improved super-twisting sliding mode control method based on the super-twisting algorithm is proposed to solve this problem. In this paper, a bidirectional half-bridge buck–boost converter was selected as the research topic. The proposed control method replaces the sign function with the saturation function to further mitigate the chattering effect. The stability of the proposed control method was proven to be finite-time convergent using the Lyapunov theory control. Compared with PI control, linear sliding mode control, and terminal sliding mode control, the proposed control method reduces the system overshoot by up to 33% and greatly improves the response speed; compared with the traditional super-twisting sliding mode control method, the system overshoot is reduced by 6.8%, and the response speed is increased by 38%. The experimental results show that the proposed control method can reduce the fluctuation range of the bus voltage, shorten the time of bus voltage stability, effectively stabilize the bus voltage of the photovoltaic DC microgrid, and maintain strong robustness.

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Background: Superbuck converter as a strong nonlinear system, with the change of parameters Superbuck converter performance may be reduced due to nonlinear phenomena, such as bifurcation, chaos. Objective: Analyzing and controlling nonlinear phenomena in current-mode controlled Superbuck converters. Method: Bifurcation diagram, time-domain waveform diagram, phase portrait and poincare section. are used as analytical methods for the nonlinear dynamic characteristics of Superbuck converters. The chaotic control method of Superbuck converter is Resonant Parameter Perturbation (RPP). Results: After applying RPP control to the Superbuck converter in the chaotic state, it is converted into a single-cycle stable state in about 0.4ms. After the converter is controlled, the output current ripple is reduced from 0.71479A to 0.31A, and the output voltage ripple is reduced from 3.905V to 0.679V. Conclusion: With the increase of the reference current or the decrease of the input voltage or the increase of the load, the system enters the chaotic state through the period-doubling bifurcation path. In this paper, the chaos control of Superbuck converter is carried out for the first time, and the control method is the resonant parametric perturbation method. After RPP control, the converter is changed from unstable chaotic state to stable period 1 state in about 0.4ms.