Distributed Control for the Modular Multilevel Matrix Converter

The modular multilevel matrix converter (M3C) is a direct ac/ac topology and is promising in the medium-voltage high-power application. However, the current M3C prototypes mainly adopt the centralized control structure that may hinder its modularity and flexibility. Based on the new distributed control architecture, the corresponding design principles for the M3C are proposed to realize both the distribution of control tasks and improve the expandability. And in order to reduce the dependence of a real-time communication network, a time-dimension decoupling strategy based on a voltage decoupling and current coupling control algorithm is employed, in which the voltage loop is divided into the input side, output side, and inner circulating decoupling models that are executed in the system controller, while the real-time current loop is established on the coupling
abc
coordinate frame in each local controller. In order to reduce the influence of communication delay, a novel scheme to replace the direct ac current reference with dc power value and double synchronization phase information is adopted. The controller parameters of the current loop are also designed carefully after frequency decomposition. Finally, an experimental prototype is constructed to verify the feasibility of the proposed control scheme after a series of tests in steady-state and dynamic operations.