Active-Power-Decoupling Matrix-Type Back-to-Back Converter

Matrix converters (MCs) face application limitation due to numerous switching devices and input-output power coupling characteristics. This paper proposes an active-powerdecoupling matrix-type back-to-back converter (APD-MTBBC), which reduces the switching device count from 18 to 14 while achieving input-output fluctuating power decoupling to suppress input current distortions under unbalanced load conditions. First, the four-leg output MTBBC and its control strategy under unbalanced load conditions are analyzed, with specific focus on how the second-harmonic component in the load power causes input current harmonics. Secondly, the APD technology is introduced into the MTBBC by multiplexing the fourth output leg to construct an APD branch, which generates second-harmonic power to offset the second-harmonic component in the load power. Then, based on the spectrum analysis of the APD branch, an APD control strategy consisting of an input power outer loop, an APD branch current inner loop and an output power feedforward loop is developed to achieve fluctuating power decoupling between the input and output, thereby ensuring constant input power and sinusoidal input current. Finally, experimental results validate the efficacy of the proposed topology and control strategy. Though implemented in the MTBBC, the proposed APD technique is extendable to other indirect MC topologies.