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Modular multiactive-bridge (MMAB) converter is increasingly recognized as a potential solution for efficient power conversion in the integration of distributed energy resources, storage systems, and loads. However, optimizing MMAB converters for high-efficiency operation remains a challenge due to the inherent coupling across ports. To address this problem, this article proposes an inductance-current-minimization optimization scheme based on a hardware decoupling method. The decoupling across ports is achieved by eliminating the inductance at one of the ports, which simplifies the complexity of the system significantly. Based on the decoupled MMAB converter, an optimization scheme is proposed to minimize the root mean square value of the inductor current. Compared with the conventional modulation scheme, this scheme can reduce the inductor current and expand the soft-switching region across various power ranges and voltage ratios, thereby enhancing the operation efficiency. Furthermore, the proposed scheme is based on analytical solutions, enabling online implementation without the need for look-up tables and scalable to accommodate any number of ports. The effectiveness of the proposed scheme has been verified by a series of simulations and experiments based on a four-port MMAB converter prototype.

Stochastic Computing (SC) offers a promising computing paradigm for low-power and cost-effective applications, with the added advantage of high error tolerance. In parallel, Coarse-Grained Reconfigurable Arrays (CGRA) prove to be a highly promising platform for domain-specific applications due to their combination of energy efficiency and flexibility. Intuitively, introducing SC to CGRA would significantly reinforce the strengths of both paradigms. However, existing SC-based architectures often encounter inherent computation errors, while the stochastic number generators employed in SC result in exponentially growing latency, which is deemed unacceptable in CGRA. In this work, we propose an SC-based CGRA by replacing the exact multiplication in traditional CGRA with an SC-based multiplication. To improve the accuracy of SC and shorten the latency of Stochastic Number Generators (SNG), we introduce the leading zero shifting and comparator truncation, while keeping the length of bitstream fixed. In addition, due to the flexible interconnections among PEs, we propose a quality scaling strategy that combines neighbor PEs to achieve high-accuracy operations without switching costs like power-gating. Compared to the state-of-the-art approximate computing design of CGRA, our proposed CGRA can averagely achieve a 65.3% reduction in output error while having a 21.2% reduction in energy consumption and a noteworthy 28.37% area savings.

Modular multi-active bridge (MMAB) converter with inherent advantages of galvanic isolation, modularity and power density, can provide multiple dc ports for multifarious power conversion through high-frequency links (HFLs). However, the traditional single phase-shift control, which is widely applied in the converter due to the complex coupling among ports, leads to unfavorable efficiency performance. To independently handle each port with optimal capabilities, a dual-loop optimal control is proposed for MMAB converters to achieve the decoupling of active and reactive powers. Conditioning circuits are designed to extract power-related information that can be used to eliminate the fundamental reactive power, thus optimizing conducting and switching characteristics. The proposed control method regards each port as a subsystem regardless of the coupling through the HFL, which can be easily extended to multiport systems, which have HFL. Finally, the effectiveness of the proposed reactive-power optimal control strategy is validated on a hardware-in-the-loop-based four-port MMAB converter.

Phase-shift modulation has been widely adopted in dual active bridge (DAB) converters due to its simple implementation and great system performance. However, modular multiactive bridge (MMAB) converter, a multiport version of DAB, has poor efficiency performance under traditional single phase-shift control and lacks a comprehensive analysis of multiphase-shift modulation. In order to improve the efficiency under unfavorable working conditions, this article proposes a universal phase-shift (UPS) modulation scheme for MMAB as well as multiactive bridge converters where the port numbers can be flexibly scaled. A time-domain mathematical model under the UPS scheme is obtained by a decomposition-and-superposition modeling method. Based on the model, an optimization strategy, aiming at full zero-voltage-switching turn-on actions and minimized root-mean-square inductance currents, is proposed to reduce the overall power loss. The proposed optimization strategy takes simplicity, scalability, and optimization performance into consideration, and its optimization effects can be regarded as a global optimum. Finally, a four-port laboratory prototype of MMAB converters has been constructed. The effectiveness and superiority of the proposed UPS control strategy within the full working range have been verified by experimental results.

In this article, a time-division multiplexing (TDM) modulation technology is proposed to enhance the efficiency of modular multiactive bridge (MMAB) converters in multiport power electronic transformers over a wide operating range. The TDM modulation retains the simplicity of single phase-shift (SPS) modulation while achieving efficiency improvement by adopting different structures (i.e., half-bridge and full-bridge) under different operating conditions with dc bias capacitors. However, determining the optimal structure under the same operating condition poses a significant challenge due to the strong coupling among MMAB ports. To address this issue, this article analyzes a dual-active bridge converter to investigate the steady-state characteristics of different structures, including the root-mean-square current and zero-voltage switching. By decomposing the MMAB converter into different transmission branches, the optimal combination structure of half-bridge and full-bridge are selected based on the branch powers, forming a simple and efficient TDM modulation technology. Finally, an experimental prototype of a four-port MMAB converter is established and tested. The results demonstrate that the proposed TDM can increase efficiency up to 19.09% compared to SPS, validating the correctness and effectiveness of the theoretical analysis.

With the rapid development of renewable energy, high-frequency bus electric energy router that provides multiple ports for different sources and loads is gaining attention, and the application of redundant modules for electric energy router is necessary to improve the reliability of the system. However, the strong coupling characteristics of the common high-frequency bus structure can cause transient current dc bias and current fluctuation for redundant modules during the entry stage, which may result in overcurrent, device damage, and failed entry of redundant modules. This article proposes a partial module high-frequency current model to analyze the causes of transient current dc bias of redundant modules when entering into normal operation and designs a seamless entry control strategy for redundant modules to eliminate the current dc bias and achieve rapid entry into steady-state operation, which can remove the high-frequency current sampling process to simplify the control system. The feasibility of the proposed control strategy is verified by offline simulation and hardware-in-loop real-time simulation platform.

With the increasing popularity of renewable energy and electric terminal equipment, the large-scale application of isolated bidirectional dc–dc converters (IBDCs) is growing. Among these converters, the dual active bridge (DAB) converter, as the core topology of IBDCs, has garnered significant attention due to its bidirectional power transmission capability, simple modularity, and wide soft-switching range. To enhance the efficiency of DAB, various multi-degree-of-freedom (M-DOF) modulation techniques and related solutions have been proposed. However, there is currently a lack of in-depth understanding and thorough comparison of different M-DOF modulation techniques, making it difficult to obtain the optimal solution for different application scenarios. Therefore, based on the latest research and contributions, this article provides an overview of M-DOF, including models, objectives, and algorithms. Furthermore, the existing typical M-DOF modulation techniques are compared through experiments, exploring the differences and advantages among these technologies. Through these analyses, this article offers robust support for the advancement and application of M-DOF modulation techniques in DAB converters.

Nano-grid (NG) clusters (NGCs) have the potential to serve as an essential configuration for future low-voltage distribution networks. To address the comprehensive energy efficiency (CEE) problem over a longer time horizon, this paper proposes an energy optimization management strategy. First of all, three typical models are developed, namely equivalent circuit model, cluster loss model and energy sharing model. In the modelling, influences of port characteristics and power transmission losses of interconnecting converters are considered to more accurately describe the cluster power flow. Then, an optimal energy scheduling mechanism with high CEE is proposed based on the three established models. The strategy decomposes the complex CEE problem into three interdependent sub-problems, corresponding to the three established models. First, ensuring the bus power quality and battery requirements are satisfied based on the proposed equivalent circuit model. Second, improving cluster self-sufficiency based on cluster energy sharing model. Third, achieving high energy transfer efficiency based on cluster loss model. Extensive simulation results demonstrate that the CEE under the proposed strategy achieves significant performance improvements, with increases of 8% and 32% in energy transfer efficiency and energy self-sufficiency respectively.

In modular multiactive bridge (MMAB) converters, which are inherently coupled among dc ports, single phase shift (SPS) control has been widely adopted due to its simplicity in implementation and neglect of coupling characteristics in control algorithms. However, under SPS control, the converter may have unfavorable system efficiency performance, especially when voltage conversion ratios of ports mismatch. To improve the efficiency, this article proposes a common phase shift (CPS) control method for a generalized MMAB or multiactive bridge (MAB) converter. A comprehensive operation analysis of MMAB converters under CPS control with switching characterization of power semiconductors has been carried out. Besides, an overall power loss model is derived, with main electrical components and their power-loss behaviors taken into consideration. Moreover, an optimal strategy aimed at power loss optimization is proposed to improve the efficiency of the converter. Finally, a four-port experimental MMAB converter prototype has been constructed. The experimental results and tested efficiency curves have verified the feasibility and effectiveness of the proposed CPS control.

To improve the efficiency of hybrid dual active bridge (HDAB) converter with a half-bridge structure on the primary side and a full-bridge structure on the secondary side over the entire operating range, this article proposes a novel four-degree-of-freedom (4-DOFs) modulation scheme by taking full advantage of the respective structural characteristics of the half bridge and full bridge. First, a universal steady-state model of the HDAB converter with the 4-DOF modulation scheme is established in the frequency domain, revealing the relationship between modulation DOFs and steady-state quantities. Then, the optimal four-DOF (O4-DOF) modulation scheme is obtained for minimizing the inductor root-mean-square (rms) current with the help of the particle swarm optimization (PSO) algorithm. Compared to the conventional phase shift modulation (PSM) scheme, the proposed O4-DOFs modulation scheme greatly improves the converter efficiency. Finally, the correctness of the theoretical analysis is verified by building an experimental platform with an input voltage of 400 V, an output voltage of 100–200 V, and an output power of 1 kW.

Multiport power electronic transformers (PET) are widely used in modern power systems to facilitate flexible interconnection between various ac or dc buses, power sources, and loads. However, due to the wide range of “source-load-storage” operating points, achieving efficient operation of the isolated dc–dc converter in the PET can be challenging. This letter focuses on the modular multiactive bridge (MMAB) converter in the PET, and proposes an optimization modulation scheme based on reactive power minimization (RPM) to improve efficiency. The RPM scheme utilizes a simple reactive power open-loop and active power closed-loop control structure that can be modulated online without the use of look-up tables. Importantly, this generalized method not only significantly improves efficiency, but can also be extended to any number of ports. Finally, experimental results are presented to validate the theoretical analysis and effectiveness of the RPM scheme.

Based on the phase-shift modulation, the dual-active-bridge (DAB) dc–dc converter always features the natural self-volt-second balance performance even during the transient process. Besides, different phase-shift ratios usually result in different initial series-inductance currents. Therefore, when the phase-shift ratio is suddenly changed for dealing with the change of required transferred power, a dc offset in the series-inductance current will emerge. Especially for the high-power condition, this dc offset lasts for a long time because of the high-current value but low damping conduction resistor. Then, the magnetic saturation phenomenon may emerge in the transformer, resulting in the potential failure of the converter system. To address this issue, a simple dc-offset eliminating method is proposed for the DAB dc–dc converter. Different from most of the existing methods, the proposed one is independent from the phase-shift modulation method. Therefore, the proposed dc-offset eliminating method can be easily embedded in different phase-shift modulation methods, such as single-phase-shift, double-phase-shift, and triple-phase-shift methods. Finally, the experimental results are provided to verify the effectiveness of the proposed dc-offset eliminating method for the DAB dc–dc converter.

For the problem of narrow soft-switching range and low efficiency of dual active bridge (DAB) converter in wide voltage range, this article proposes a single-sided asymmetric duty modulation (SSADM) strategy, which contains only two control degrees of freedom, and significantly improves the soft-switching performance and efficiency at light load. First, the potential advantages of asymmetric duty modulation (ADM) method are described through waveforms. The principle of determining which full bridge to adopt the ADM is given and the working principle of SSADM is described. Second, a linear pulse logic combination analysis of SSADM in time domain is performed to establish a complete steady-state mathematical model. To solve the analytical expression for the optimal solution of SSADM, the peak-to-peak value of the inductor current with simple expression is chosen as the optimization objective, and the global optimal solution of SSADM is solved based on the Karush–Kuhn–Tucker (KKT) condition, and the voltage closed-loop control strategy of SSADM is presented. In addition, the soft-switching range of SSADM is analyzed. Finally, the experimental platform of DAB converter based on SiC device is built. Compared with other modulation strategies, SSADM shows better soft-switching performance with significant efficiency improvement, which is verified by the experimental results.