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.

Multiwinding-transfomer-based (MTB) dc-dc converter did emerge in the last 25 years as an interesting possibility to connect several energy systems and/or to offer higher power density because of the reduction of transformer core material and reduction of power converter stages. MTB dc-dc converters can be considered as an interesting compromise between nonmodular and a modular dc-dc converter since they are themselves modular in the construction. This eventually leads to some fault-tolerant possibilities since the multiwinding transformer (MWT) connects multiples ports and if one of them is not working anymore and it can be isolated, the others might still continue operating. Unfortunately, it is exactly the MWT that creates most of the technical challenges of this class of dc-dc converters because of the cross-coupling effects among the cells, which make especially the resonant-topology very challenging to be designed. This article reviews the history of the MTB dc-dc and then provides a classification of them, comparing them with figure of merits and focusing on which is the maximum possible number of windings and which are the most suited magnetic core types. The problems coming from cross coupling and the possible fault-tolerant operation are analyzed with the help of simulation and experimental results.

Cascaded H-bridge (CHB) multilevel converters are promising candidates for large-scale grid-connected photovoltaic systems (megawatt to gigawatt). However, the conventional CHB multilevel converter cannot ensure the inter-module and inter-phase power balance, resulting in imbalanced grid currents. Therefore, in this paper, a new topology consisting of CHB multilevel converters and interleaved-boost full-bridge LLC (IB-FBLLC)-based three-port dc-dc isolation converters is proposed. In this proposed topology, a common dc bus made up of the low-voltage-side ports of IB-FBLLC-based three-port dc-dc converters can completely solve the inherent power imbalance issues. Moreover, the design parameters of dc-dc converters considering the minimization of the input current ripple and optimization of switching frequency range are discussed in detail. Simulation results of the three-phase system and experimental results of the single-phase system clearly verify the effectiveness and feasibility of the proposed topology and control strategies.

Power Line Communication (PLC) and Simultaneous Wireless Information and Power Transfer (SWIPT) are popular examples of applications, where power and information are transmitted simultaneously. In most cases, different devices have been used to generate the power and communication signals independently. Usually, the information is superimposed onto the power signal using an external modulator. Recently, power converters have been used to generate pulses not just for power conversion but also for information transfer simultaneously. This approach represents a fundamental difference because it exploits the signal processing potential of Pulse Width Modulation (PWM), where for power conversion only the average pulse width is used, while the information is represented by the harmonics instead of being filtered out, as typically done in power electronics. The concept of embedding information into the switching ripple generated by a switched-mode power converter has recently been dubbed Talkative Power (TP), in this paper referred as Talkative Power Conversion (TPC). TPC technologies are reviewed in non-isolated and isolated converters in this paper. Potential applications include visible light communications, battery management systems, switching reluctance generators/motors, microgrids, and wireless electric vehicle charging stations. Finally, trending topics are identified.

The modular multilevel converter (MMC) is an attractive option for high-voltage and high-power applications. Fault localization is one of the most important challenges for the MMC consisting of a large number of power electronic switches. Existing literature has not provided a complete fault localization strategy for the MMC under submodule (SM) lower switch open-circuit fault, which only considers the MMC in inverter mode and neglects the MMC in rectifier mode. This paper proposes a fault localization strategy for the MMC under SM lower switch open-circuit fault, which is suitable for the MMC not only in inverter mode, but also in rectifier mode. This paper analyzes the MMC fault characteristics under SM lower switch open-circuit fault, which considers the MMC in inverter and rectifier mode, respectively. Based on two modes' common fault characteristic that the capacitor is charged all the time during the period when the arm current is positive, the faulty SM can be effectively located by the proposed fault localization strategy. The proposed strategy is not only implemented in simulation with professional tool PSCAD/EMTDC, but also verified with a down-scale MMC prototype in the laboratory. The results confirm the effectiveness of the proposed strategy.

A smart transformer (ST), which is a power-electronic-based transformer with control and communication functionalities, can be the optimal solution for integrating a battery energy storage system (BESS) in an electric distribution system. In fact, a comparison of energy efficiency for the conventional BESS and the ST-based BESS is carried out, which demonstrates that the ST-based BESS operation is more efficient during charging and discharging, as compared to the conventional BESS. It has been shown that by sizing the BESS appropriately for the peak load demand, the power rating of ST converters can be reduced. The ST-based BESS provides an enhanced fault ride-through capability, as compared to the conventional BESS. However, the state of charge (SOC) of the BESS shall be correctly managed to support the peak load demand when the ST converter reaches its maximum active power rating. Both simulation and experimental results clearly verify the developed SOC management.