Abstract
This paper proposes a galvanically isolated dc-dc converter that can regulate the input voltage in a wide range. It is based on the series resonance dc-dc converter (SRC) topology and a novel boost rectifier. The proposed topology has a smaller number of semiconductors than its SRC-based existing topologies employing an ac-switch in the boost rectifier. The proposed dc-dc converter comprises only two diodes and one switch at the output side, while the existing solutions use two switches and two diodes to step up the voltage. The proposed converter boosts the input voltage within a single boosting interval in the positive half-cycle of the switching period. In addition, the resonant current in the negative half-cycle is sinusoidal, which could enhance the converter efficiency. The resonant capacitor voltage is clamped at the level of the output voltage. Therefore, the voltage stress of the capacitor could significantly reduce at various input voltage and power levels. This makes it perfect for distributed generation applications such as photovoltaics with wide variations of input voltage and power. The converter operates at the fixed switching frequency close to the resonance frequency to obtain the maximum efficiency at the nominal input voltage. The zero-voltage switching (ZVS) feature is achieved in the primary semiconductors, while the diodes in the output-side rectifier turn off at nearly zero current switching. The mathematical model and design guidelines of the proposed converter are discussed in the paper. The experimental results confirmed the theoretical analysis based on a 300 W prototype. The maximum efficiency of the converter was 96.8% at the nominal input voltage, and the converter has achieved a wider input voltage regulation range than that with the boosting cell comprising an ac-switch.
Highlights
With the rapid growth in the installation of photovoltaic (PV) modules in residential settings worldwide, the demand for new power converters with high efficiency and low cost is increasing [1]
The converter with a wide input voltage regulation range could be capable of tracking the maximum available power of the PV module in various environmental and shading conditions
The converter operates at a fixed switching frequency, FSW, which has to be selected at 5–10% lower than the resonance frequency to obtain the possible high conversion efficiency under the nominal input voltage [13]
Summary
With the rapid growth in the installation of photovoltaic (PV) modules in residential settings worldwide, the demand for new power converters with high efficiency and low cost is increasing [1]. The buck regulation requires the use of a special modulation at the input side, while the boost regulation requires a boosting rectifier cell, regulating the transformer leakage inductance current at the output side [10]. It can regulate the voltage while operating at a fixed switching frequency by adjusting the duty cycle of the semiconductors. The bridgeless rectifier cell with two diodes and two metal oxide semiconductor field-effect transistors (MOSFETs) has been used widely in power factor correction applications It has been used in [13], to step up the input voltage. Where POUT is the load power, and TSW is the switching period of the converter
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