Enhanced Finite Control Set Predictive Current Control for Modular Multilevel Converters

The forward Euler integration method has been widely adopted in the development of discrete-time models of modular multilevel converter (MMC) for the implementation of finite control-set predictive current control (FCS-PCC) methods. The use of forward Euler method-based models in FCS-PCC leads to high switching frequency operation, while minimizing the reference current tracking error. However, the high switching frequency operation leads to significant switching losses, which undesirable in high-power MMC applications. Furthermore, these models affect the controllability of submodule (SM) capacitor voltages, leading to a higher voltage ripple. To address these problems, this paper proposes Heun's integration method-based FCS-PCC for an MMC, which aims to reduce the switching frequency and SM capacitor voltage ripple, while maintaining high-quality output waveforms. The proposed approach consists of predictor and corrector stages, which help to reduce computational errors caused by mathematical models inaccuracy at large sampling rates while predicting control variables. The discrete-time models of an MMC are developed by using Heun's integration method and employed in the proposed FCS-PCC implementation to control the MMC. The performance of an MMC with the proposed FCS-PCC has been validated through MATLAB simulations and is further compared with the forward Euler method-based FCS-PCC method.