Disturbance Suppression for Testing System of Submodules in MMC by Dynamic Correction Control and Parameter Design

In order to perform advanced tests for the submodules (SMs) of modular multilevel converter (MMC) in a cost-effective and accurate way, mission profile emulation (MPE) technique is becoming a promising solution. MPE technique aims to test small number of SMs by emulating the mission profiles of MMC as testing conditions. However, a common problem for MPE is that when the SM works under nearest level modulation, the outputs of the SMs are voltage pulses or staircase-like voltages, which will severely disturb the testing current and further degrade the emulation accuracy for mission profiles. To suppress this disturbance, the existing methods mainly chose to utilize larger filter inductor or auxiliary circuit, which will inevitably increase the economic cost and complexity for testing system. As a result, this article proposes a suppression method to suppress the disturbances, and a parameter design method coping with suppression method to minimize the current distortion. With the proposed method, the mission profiles can be accurately and flexibly recreated without auxiliary circuits. Simulation and experimental verifications are provided to validate the proposed control and design method.