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Due to the slow dynamic power-regulation characteristics of the electrolyser (EL), a novel integrated three-port DC/DC converter topology based on a phase-shifted full-bridge converter and dual active-bridge converter is proposed in this paper. Especially, the proposed converter can achieve a fast auxiliary response to the EL. This topology has the features of single-stage conversion, high system integration and compatibility with multiple operation modes. The operational principles and a hybrid modulation scheme of the proposed converter are analysed in detail. In addition, the power-transmission characteristics of each port and the soft-switching range are researched. On these bases, six operation modes suitable for a hydrogen energy-storage system are designed. The simulation and a 2-kW scaled-down experimental prototype are established to verify the feasibility and effectiveness of the proposed topology in different operation modes. [ABSTRACT FROM AUTHOR]

This article proposes a novel single-stage bidirectional isolated dc–ac converter based on an inversely coupled inductor, which is feasible to be used in cascaded dc–ac solid-state transformer topologies. The topology description is presented, followed by a simple modulation scheme, then direct single-stage power transmission can be realized. The operating principles of the converter are given in detail. The steady-state and transient performance of the converter can be improved owing to the employment of an inversely coupled inductor. By combining magnetic integration technology with an inversely coupled inductor, the volume and number of magnetic components can be reduced. The detailed analysis of the duty cycle loss is carried out in this article as well. Finally, an experimental prototype is established to further verify the correctness of the proposed topology. The maximum efficiency achieved in the experimental 1-kW prototype is 94.37%. [ABSTRACT FROM AUTHOR]

A novel single-phase pulsewidth modulation (PWM) direct ac–ac converter based on two-level nondifferential dual-buck ac chopper legs with inverting and noninverting operations is first proposed in this article. It has the ability to resolve both voltage sag and swell problems at the same time when used as distributed flexible voltage conditioner. Compared to the traditional ac–ac converter, it has much enhanced system reliability thanks to no shoot-through problems even when all switches of each ac chopper legs are turned on, and therefore, the PWM dead time is not needed leading to improve the utilization of the duty cycles. Only half of the switches in the proposed converter is switched at high frequency during a switching period at most, which significantly reduces the total switching loss. In particularly, the converter has two greatest advantages that it retains the common sharing ground of the input and output and has the same buck/boost operation process for noninverting and inverting modes. In order to fully testify the performance of the proposed converter, a 500-W experimental prototype is built and tested at different conditions. [ABSTRACT FROM AUTHOR]

This paper introduces the high-frequency link concept into the modular multilevel converter (MMC) topology, which can totally reduce the individual dc-link capacitors at the high-voltage side. The proposed converter, called isolated MMC, has basic triple ports of medium-voltage ac, medium-voltage dc, and low-voltage dc. Thus, it is especially suitable for hybrid dc and ac applications in power generation and transmission, such as solid-state transformer. The fundamental principle and applied control scheme of phase-shift pulsewidth modulation are presented in detail. The design of the voltage clamping circuit and analysis of duty loss are carried out. The experimental results are given to illustrate the efficient operation characteristics. [ABSTRACT FROM AUTHOR]

This paper introduces a novel H-bridge structured ac–ac pulsewidth modulation (PWM) converter topology based on two-level non-differential ac chopper legs, which can work at the non-inverting and inverting modes for the utility voltage compensation. Compared to the traditional bipolar-type H-bridge ac–ac converter, no bidirectional switches are switched in a complementary manner to overcome the commutation problem due to the delayed response of electronic circuits and semiconductor switching devices. The detailed PWM control signals and operational principles are presented to regulate the output voltage in a bipolar manner. Especially the main advantage is that the proposed ac–ac converter has the same buck/boost operation process for non-inverting and inverting modes, which ensures the continuously average current supply to the low-voltage output side without a high-value capacitor to support power. Additionally, due to the common sharing ground of the input and output, the feature that output can reverse or maintain phase angle with input is supported well. Then, the detailed analysis, design conditions, and experimental verification based on a 1 kW experimental prototype are presented. [ABSTRACT FROM AUTHOR]

A novel bidirectional transformerless photovoltaic (PV) inverter based on the high-frequency leg (HFL) technique is proposed which can work on discontinuous current mode/continuous current mode having greatly enhanced reliability. With the high-frequency leg, the smooth ac current is achieved as the higher equivalent switching frequency can reduce the inductor current ripple decreasing the passive components' volume. There is no dead time issue which can push the duty cycle to the theoretical limit and fully transfer the energy to grid through total pulse width modulation. And the capacity of the PV inverter can be expanded easily by increasing the number of high-frequency legs. Additionally, the proposed topology can work under the rectifier mode having the bidirectional power capability, which is attractive for the PV application. In the end, the experimental results of 8-kW laboratory prototype have verified the feasibility and effectiveness of the proposed transformerless PV inverter under standalone mode. [ABSTRACT FROM AUTHOR]