In recent years, modular multilevel converters (MMCs) are very popular in medium/high-voltage motor drive systems and high-voltage direct-current (HVDC) applications. The conventional model predictive control (MPC) strategies for the MMC are not practical due to their substantial calculation requirements, especially under high number of voltage levels. To solve this problem, a fast MPC strategy combined with a submodule (SM)-voltage sorting balancing method is proposed based on the discrete mathematical model derived for the MMC in this paper. By optimizing the implementation of the control objectives and simplifying the rolling optimization, the proposed strategy is simpler to expand to a system with larger number of SMs, with the amount of calculation reduced and the advantages of the conventional MPC algorithm reserved. In addition, the proposed control can minimize the dv/dt of the output voltages. Both steady-state and transient performances are evaluated by a down-scaled three-phase MMC prototype under various experimental conditions, which validates the proposed fast MPC strategy.

Modular multilevel converters (MMCs) have been widely used in recent years due to their superior advantages in medium/high-voltage applications. The finite control set model predictive control (FCS-MPC) has shown high dynamic responses for the control of the MMC. However, with the existing FCS-MPC algorithms, the steady-state performances are degraded due to the irregular pulse patterns, especially under unbalanced grid conditions. In this paper, based on the discrete state-space model of the MMC, a modulated MPC (M2PC) algorithm is proposed to overcome the aforementioned drawback of the FCS-MPC. Compared to FCS-MPC algorithms, the M2PC accurately calculates and tracks the reference circulating current and adopts an effective modulation method, and, in turn, the proposed M2PC can obtain enhanced steady-state ac-side/circulating currents control performances under unbalanced grid conditions, with the high dynamic-state performances of the conventional FCS-MPC algorithms reserved. Experimental results regarding one typical FCS-MPC algorithm and the proposed M2PC algorithm are comparatively evaluated in detail for the steady/dynamic-state performances and pulse patterns by a downscaled prototype. The effectiveness and feasibility of the proposed M2PC are clearly validated by the experimental results.

Three-phase voltage source inverters (VSIs) with output $ LC$ filter are preferred topologies to provide voltage and frequency support for islanded ac microgrids. This article proposes a finite-set quasi-sliding model predictive control (FS-QSMPC) scheme for $LC$ -filtered VSIs to improve the output-voltage quality. By explicitly including a predictive sliding-mode function into the cost function, reduced steady-state ripple and enhanced robustness are achieved compared to typical FS-MPC. Besides, theoretical analysis of stability and robustness for FS-QSMPC is given. Analytical tuning of the weighting factor is also derived to decrease the tuning effort. Comparative simulations and experiments verify the presented approach.

In this paper, the input-parallel output-parallel (IPOP) three-level (TL) dc/dc converters associated with the interleaving control strategy are proposed for minimizing and balancing the capacitor ripple currents. The proposed converters consist of two four-switch half-bridge TL dc/dc converters featuring with simple and compact circuit structures, which can reduce the current stresses of the components and increase the power rating of the converter. The combination of the proposed IPOP TL circuit structure and the interleaving control strategy can greatly reduce the ripple currents on the two input capacitors not only by doubling the frequencies of these ripple currents as the universal benefit of utilizing the interleaving control strategy but also by counteracting part of these ripple currents due to the operation principle of the proposed IPOP TL circuit structure. More importantly, the ripple current imbalance between the two input capacitors can be eliminated by combining the proposed IPOP TL converters and the interleaving control strategy, which can improve the converter's reliability in balancing the thermal stresses and lifetimes of the two input capacitors. The theoretical analysis of the ripple currents on the two input capacitors is presented in detail. Finally, the simulation and experimental results are presented to verify the proposed converters with the interleaving control strategy.

LC-filtered permanent magnet synchronous motor (LC-PMSM) system is suitable for long-cable drives but it has inherent resonant stability issues. This paper presents a modulated model predictive current controller with active damping (AD-M2PCC) for stabilizing the LC-PMSM drive system. First, to avoid the complex exponentiation operations in typical MPCC, a simplified reduced-order predictive model is constructed and a baseline MPCC is derived based on inverter-side current reference tracking, reducing the computational burden and enhancing the robustness to the model mismatches. Then, a capacitor-current-feedback AD is integrated into MPCC for resonance suppression. It has an intuitive damping concept and only one design parameter, significantly lessening the tuning effort. Further, a low-complexity AD-M2PCC scheme is established, which features simple implementation, improved steady-state performance and effective resonance damping. Comparative experimental results are provided to verify the feasibility of the proposed control scheme.

A virtual vector based modulated model predictive control (VV-M2PC) strategy is proposed for the indirect matrix converters (IMCs) in this article. Compared with the conventional M2PC, the VV-M2PC constructs and utilizes new virtual vectors to reduce the current control errors. Besides, the implementation and feasibility for the proposed strategy is discussed in detail. The comparative simulation and experimental results based on an experimental IMC prototype verify that the steady-state control performance can be improved under the VV-M2PC without affecting the dynamic-state control performance and increasing the computational burden.