The need to build resilient distribution systems provides the incentive to decentralize voltage stability responsibilities across the entire network instead of the main grid. This requires the system to operate in various modes depending on the availability and location of the voltage sources. To facilitate seamless transitions between different operation modes, this paper presents a unified control scheme designed for the interlink converter connecting multi-voltage buses in distribution systems. Under normal conditions, the proposed scheme efficiently manages power flow. In the event of loss of a voltage control unit at one bus, the scheme autonomously provides voltage support to this bus to ensure the stable operation of the whole network. This is achieved without the need for mode detection and communication, thereby preventing instability risk due to the inaccurate or delayed mode transition. Moreover, the proposed scheme inherently supports input-series output-parallel converter configurations, achieving input voltage sharing and output current sharing without additional control loops. Simulation results validate the effectiveness and robustness of the proposed scheme.

Modular multi-active-bridge (MMAB) converters have emerged as promising solutions for efficient power conversion in integrating various distributed energy resources, energy storage systems, and loads. However, existing studies predominantly rely on centralized controllers, which limit modular scalability due to the lack of software modularity. This also poses significant computational burdens for the centralized controllers. To address these challenges, this paper proposes a decentralized control method based on a decoupled MMAB converter. The decoupling is achieved by eliminating the inductance from one port, thereby simplifying the control complexity. Based on the decoupled MMAB converter, a decentralized control scheme is proposed, which is composed of a PI controller for frequency synchronization and a proportional controller for direct phase-shift regulation. This combination ensures accurate module synchronization and rapid transient responses. A detailed parameter design is obtained using small-signal analysis. Additionally, a thorough inductance design methodology is provided to maintain the phase shift within a stable operating range. Simulation results validate the effectiveness and superior dynamic performance of the proposed decentralized control strategy.

In order to estimate the short-circuit capability of SiC MOSFET-based power converter, this paper proposes a behavioral model of SiC MOSFET that can be used for short-circuit simulation in PSpice, and the leakage current generated during short circuit is considered, which is an early warning of device failure. The short-circuit characteristic of SiC MOSFET is discussed and analyzed, and a thermal model of case-to-junction is built to describe the junction temperature of SiC MOSFET during short-circuit condition. Based on the junction temperature information, the channel current model and leakage current model are established respectively. The simulation results show that the short-circuit model can correctly reflect the static characteristic and short-circuit characteristic of SiC MOSFET. This circuit model can provide guidance for the design of short circuit protection circuit.

The papers in this special section offer a collection of new and original papers that cover different aspects from architecture, scheme design, control strategy, optimization, application and deployment of energy Internet systems.

To solve the simulation convergence problem of Silicon Carbide metal-oxide semiconductor field effect transistor (SiC MOSFET) models, this paper proposes a non-segmented model for SiC MOSFETs, which uses non-segmented, smooth continuous equations to describe the static and dynamic characteristics of SiC MOSFET. Further, the static characteristic of SiC MOSFET obtained by the non-segmented model is verified by comparing the simulation curves with the static curves provided in datasheet, and the dynamic characteristic is verified by comparing the simulation rise time and fall time of voltage with the datasheet based on the double pulse simulation circuit. The accuracy and good convergence of non-segmented model provide a good way to research the power converters with SiC MOSFETs by simulation way.

Microgrids rely on energy management levels to optimally schedule their components. Conventionally, the research in this field has been focused on the optimal formulation of the generation or the demand side management separately without considering real case scenarios and validated only by simulation. This paper presents the power scheduling of a real site microgrid under a price-based demand response program defined in Shanghai, China managing generation and demand simultaneously. The proposed optimization problem aims to minimize operating cost by managing renewable energy sources as well as shiftable loads considering the preferred time of use. The proposal has been tested experimentally in a laboratory prototype.

In a microgrid system, distributed energy storage units are commonly employed as the energy buffers. In this paper, a dynamic power sharing method based on the state-of-charge (SoC) of each energy storage unit is proposed. Droop control is employed as the basic control strategy for the distributed energy storage units. By using the proposed method, the coefficients in the conventional droop method are adjusted according to the SoC of each energy storage module. The modules with higher SoC delivers more active power, while those with lower SoC delivers less. Meanwhile, the reactive power is equally shared in the energy storage system. The relationship between the droop coefficient and SoC are studied deeply and the small signal model is developed to verify the stability of the control system. It is found that the active power sharing speed becomes faster with higher exponent of SoC. At the same time, in order to restore the AC-bus voltage, secondary control is employed to eliminate the deviations of the voltage frequency and amplitude caused by the droop control, with the droop coefficients adjusting according to the SoCs. The model of the secondary control scheme for SoC-based droop method is developed and its stability is discussed. The theoretical analysis is demonstrated by both simulation and experimental results.

In order to estimate the speed fluctuation band of interior permanent magnet synchronous motor (IPMSM) under speed sensorless control with cyclic fluctuating load accurately, an improved rotor speed estimation method is proposed. A rotor flux oriented vector control with conventional model reference adaptive system (MRAS) based rotor position/speed estimation is employed as the basic control strategy for IPMSM drive. The finite element method (FEM)-based model of IPMSM is built by magnetic field analysis in JMAG software to obtain motor parameter variations caused by different phase currents and rotor position. These motor parameter variations are used in MRAS for precise speed fluctuation band estimation. Furthermore several motor output torque patterns matching the cyclic fluctuating load with feed-forward compensation strategy are developed to lower the speed ripple. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposed control methods, which shows that the error between actual speed fluctuation band and estimated speed fluctuation band is limited within a very low level.

A novel interleaved-series/parallel forward converter (ISP-FC) is proposed. The ISP-FC is composed of two low-voltage switching-legs and a high-voltage switching leg. The three switching-legs construct two forward cells. The voltage stress on the low-voltage switching-legs is only half of the input voltage while that on the high-voltage switching-leg is the input voltage. The maximum duty cycle of the ISP-FC can achieve 0.67, 1.33 times of that of the two-switch forward converter, which leads to wide input voltage range. The high-voltage leg switches can be soft-switched when duty cycle less than 0.5 while the low-voltage leg switches can be soft-switched when duty cycle larger than 0.5. As a result, high efficiency is achieved over a wide voltage range. The operation principles and characteristics of the ISP-FC proposed is analyzed in detail and verified with experimental results.