Development of Linearized Direct Power Control for Three-Phase Rectifiers under Unbalanced Power Grid

This paper proposes a custom Clarke transformation applied to linearized voltage modulated direct power sliding mode control of three-phase rectifiers in unbalanced power grids to improve the three-phase current distortion caused by unbalanced power grids. Linearized voltage modulated direct power control uses algebraic transformation to convert the power inner loop of the original stationary frame from a linear time-varying system to a linear time-invariant system, which simplifies the controller design. The existing literature on linearized voltage modulated direct power control does not utilize in the unbalanced power grid. In this paper, a new type of custom Clarke transformation is developed in the unbalanced power grid. The user can define the Clarke matrix coefficients to fit for unbalanced power grid condition. The stationary frame α and β components can be derived through the custom Clarke transformation under unbalanced power gird and the input current distortion can be reduced. In addition, a sliding mode controller is added into the output voltage control loop to enhance dc-bus dynamic performance.