Improved Indirect Model Predictive Control for Enhancing Dynamic Performance of Modular Multilevel Converter

Abstract

Model predictive control has become a tremendously popular control method for power converters, notably a modular multilevel converter, owing to the ability to control various objectives at once with a particular cost function and prominent dynamic performance. However, the high number of submodules in cascaded control means that the model predictive control for the modular multilevel converter suffers from a computational burden. Several approaches focused on reducing the computational burden based on limiting the number of possible switching states (possible choices) to be evaluated at each sampling instant. The dynamic performance of the modular multilevel converter is degraded in a transient state, despite the reduced computational burden. This paper presents an improved indirect model predictive control method to reduce the computational burden and enhance the dynamic performance. The proposed approach considers the steady-state and transient state individually and applies a different range of choices for each specific case. The range of choices during the steady-state is limited in order to reduce the computational burden without deteriorating the output quality, whereas the number of choices will be increased during the transient state to guarantee dynamic performance. The results that were obtained by implementing an experiment on a laboratory setup of a single-phase modular multilevel converter are presented in order to verify the proposed approach’s effectiveness. From the experimental setup, the computational time in the proposed approach was reduced by about 75% when compared with the conventional indirect model predictive control, whereas keeping fast dynamic performance.

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Compensation of Unbalanced Low-Voltage Grids Using a Photovoltaic Generation System with a Dual Four-Leg, Two-Level Inverter

“…However, these solutions require the use of multiple transformers. Another approach is based on the use of several submodules, in which each one consists of a two-level half-bridge DC-AC converter, which was designated the modular multilevel converter (MMC) [48][49][50][51]. However, this configuration uses an extensive number of submodules.…”

Non-Linear Model Predictive Control for Modular Multilevel Converters

“…Recently, some other variants of indirect FCS-MPC methods have been presented to address the issue of slow dynamic performance, while keeping the computational complexity low [14]- [17]. In [14], the steady-state and transient state are handled individually.…”

“…Recently, some other variants of indirect FCS-MPC methods have been presented to address the issue of slow dynamic performance, while keeping the computational complexity low [14]- [17]. In [14], the steady-state and transient state are handled individually. In steady-state, the number of options to be evaluated are the same as in most indirect FCS-MPC strategies, however, they are increased in the transient state which allows for high dynamic performance.…”