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The classic cascaded boost–buck converter has inductors at the input and output ports of the converters, which makes it an ideal interface for bidirectional battery charging applications, where accurate current control and low ripple currents are required. This article proposes a split duty cycle coupled multiphase variant applied to the cascaded boost–buck converter and utilizes coupled inductor features to achieve very lower current ripples at the output, lower power losses, and reduction in magnetic component volume. Moreover, current sharing between each phase is inherently implemented, making it suitable for a high-conversion-ratio bidirectional operation in systematic energy storage applications, where the low-voltage port has very high current. This article covers a split duty cycle converter operation principle using coupled inductors between the input and the multiphase output. Magnetic component design and selection guidelines are presented. The proposed control method and the coupled inductor structure are validated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The high peak current withstand capability of thyristors makes them extremely suitable for pulsed power applications. Silicon carbide (SiC) thyristors provide significant efficiency advantages compared with their silicon counterparts due to their very fast switching transitions. This article presents the development and characteristics of 3 kV SiC thyristors. A novel current-source gate driver is proposed to enhance their switching speed and, hence, maximize their benefits in pulsed power applications. The proposed driver provides a very high gate current slew rate while limiting the peak of the current pulse. The higher gate current slew rate achieves faster and, thus, more efficient device switching transition. Gate driver circuit description, variant topologies, and experimental results for a 3 kV SiC thyristor for a pulsed power application are presented to verify the proposed concepts. [ABSTRACT FROM AUTHOR]

Microinverter-based photovoltaic (PV) systems now represent about 8% of the U.S. residential market, and offer many advantages including safety, performance, and simplified installation. The next-generation of PV microinverter will include more ancillary functions to support grid stability and reliability in more distributed generation smart-grid systems. A commercial ready PV microinverter not only focuses on efficiency and cost, but also on reliability, manufacturability, compliance of various grid-code, and electromagnetic interference regulations. This paper presents a detailed design and development process of a microinverter system from concept all the way to final commercial-ready prototype. Various design tradeoffs such as topology, control, filter solutions and power supplies, and mechanical packaging are provided. The required prototype testing and final system field tests are also presented. The presented design and test process intends to accelerate the future microinverter system design and development toward a commercial ready product. [ABSTRACT FROM PUBLISHER]

This article presents novel transformerless single-stage buck-boost inverters with reactive power flow capability. The common-mode voltage of the proposed inverters is constant, which results in negligible leakage current. The output current of the proposed inverters is continuous that lowers the output harmonics and size of the output filtering capacitor. In the proposed inverters, only two switches receive high-frequency switching signals at a time, which reduces the power loss. The proposed topologies can achieve efficient power conversion with a wide input voltage range. A 120-Vrms/60-Hz output voltage, 74–200-V input voltage, and 500-W output power hardware prototype of the proposed inverter is built and tested with resistive, partially inductive, and partially capacitive loads. A peak efficiency of 97.3% is obtained. [ABSTRACT FROM AUTHOR]

This paper presents novel single-phase single-stage buck–boost inverters. The proposed inverters provide buck–boost operation for a wide variation of the input dc voltage. In addition, the proposed inverters are bidirectional and provide reactive power. Further, they require only one inductor. The proposed inverters also eliminate the common-mode leakage current by connecting the output neutral to the midpoint of input capacitors or directly to input voltage sources. Therefore, they are well suitable for photovoltaic applications. Although six switches are required, two switches are working at line frequency, resulting in negligible switching loss. Of the four remaining switches, only two are switching at high frequency at a time. The circuit operations are demonstrated through the analysis of the proposed inverters. A 120 Vrms/60 Hz/400 W hardware prototype was constructed and tested. The experimental results verified the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a novel control strategy to significantly reduce the high-frequency transformer loss in a modular solid-state transformer (SST) based converter system. The modular SST design is based on an ac–dc power-electronic building block comprised of an H-bridge at the ac input and a bidirectional soft-switching isolated dc–dc converter with a medium-voltage insulated high-frequency transformer. The ac terminals of input H-bridges are connected in series and directly coupled to the medium-voltage ac line, while the output dc terminals are all connected in parallel at a low voltage. The key innovation described in this paper, without sacrificing the output performance, is the control scheme that reduces core and winding losses associated with the dc–dc resonant stage by turning off the selected dc–dc converters in synchronism with the line voltage. The prototype for the test described in this paper is based on a modular SST where each module is rated at 50 kVA, with a 200 kHz transformer using 1.7 kV silicon carbide discrete mosfets, but the described control concepts are more broadly applicable to similar topologies. [ABSTRACT FROM AUTHOR]