Model Predictive Arm Current Control for Modular Multilevel Converter

Abstract

Arm current control is a promising candidate for modular multilevel converter (MMC) due to it can effectively regulate ac-side current and control the ac component of circulating currents simultaneously. The conventional arm current controller designed in frequency domain based on classical control theory have to design the separate controller for each frequency reference signal. As a result, the controller structure is complicated. And limited by the bandwidth of the arm current compound controller, the control performance will be affected by the grid-side voltage harmonics. Model predictive control (MPC) is an optimal control method in time domain. It not only has fast dynamic response, but also can track multi-band composite signals with high accuracy. To address the above issues of traditional arm current control, this paper proposes a model predictive arm current control strategy. Combined with phase-shifted carrier pulse width modulation (PSC-PWM), the computation burden of the presented method can be independent of the number of cascaded sub-modules (SMs). Simulation and experimental results reveal the proposed MMC integrated control strategy has fast dynamic response with small tracking errors even under non-ideal grid conditions.