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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 use of single-stage power-factor-corrected (SSPFC) three-level resonant ac/dc converters solves many problems that present SSPFC converters face today, namely, high component stresses, high circulating currents, and low efficiency. This makes single-stage three-level resonant ac/dc converters a good candidate for high-power applications. These converters provide the flexibility of simultaneously using two control variables. They can operate with a combined variable-frequency and asymmetrical pulsewidth modulation or with a combined variable-frequency phase-shift modulation. This provides good regulation of the output voltage, dc-bus voltage, and input current. The drawback of these methods is that the efficiency of the converter drops as the load is reduced because the converter starts to drift away from its resonance frequency, thus leading to more circulating currents and conduction losses. Therefore, a load-adaptive energy storage technique is proposed in this paper to guarantee the converter operation near its maximum efficiency point for a wide range of loading. This leads to almost constant converter efficiency from full load to 40% load. The use of interleaved converters is also proposed to extend the constant efficiency range of operation to lighter loads (15%–20% of full load). Analytical simulation and experimental results are presented to verify the proposed methods. [ABSTRACT FROM AUTHOR]

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]