A Modulated MPC Algorithm for Modular Multilevel Converter with Low Calculation Burden

Because of many attractive merits, such as easy realization, excellent dynamic performance and multi-objective regulation capability, model predictive control (MPC) is widely utilized in voltage source converters (VSCs). However, when comes to modular multilevel converters (MMCs), it has several implementation challenges, such as heavy computation burden, non-fixed switching frequency, poor steady-state performance and complex weighting factor determination. Considering these challenges, this paper developed a novel modulated MPC method. With this method, the optimal modulation references can be directly obtained at each sampling period according to the duty cycles of two fixed voltage levels, and then be fed into the modulator to get gate signals. Hence, the developed method is very easy to be implemented with a very low calculation complexity, independent of the submodules (SMs) number. The switching state evaluation, cost function calculation and weighting factor selection are eliminated as well. In addition, this method has a satisfactory steady-state performance and equally distributed switching losses. The effectiveness the proposed method is verified by experiments.