To address the stability issues aroused by the negative-resistance effect of constant power loads (CPLs), this paper proposes a composite robust discretized quasi-sliding mode control (DQSMC) scheme for stabilization of buck-converter fed dc microgrids with CPLs. In the outer control loop, a robust DQSMC voltage controller is proposed. First, a discrete integral sliding surface is designed to obtain a fast and robust dynamic response of dc-bus voltage. Then, to tackle the varying load disturbances and model uncertainties, a second-order sliding mode disturbance observer is embedded in the voltage controller for disturbance estimation and compensation. The resulting composite DQSMC scheme features enhanced disturbance rejection, inherent chattering suppression, and guaranteed dynamics. Meanwhile, a PI current controller is retained in the inner control loop to realize the current control and limitation. Robustness and stability analysis of the whole composite controller are proved to assure large-signal stability. Simulation and experimental results confirm the superiority of the presented approach.
|Journal||IEEE Journal of Emerging and Selected Topics in Power Electronics|
|Publication status||Published - 2021|
- Buck converter
- Constant power load (CPL)
- Chattering suppression
- Sliding mode control (SMC)