A modified two-channel LLC resonant converter with optimal efficiency for wide input voltage applications. The converter has the same voltage gain and power handing ability as conventional full-bridge (FB) resonant converter, but the hardware cost is lower than conventional FB resonant converter, and the operational frequency range is narrower than conventional resonant converter for the same working condition. It has the characteristics of low input impedance at low input voltage, which is used to provide high voltage gain, and high input impedance at high input voltage, which is used to provide low voltage gain, the above characteristics are analyzed and optimized to improve the efficiency for photovoltaic applications where wide voltage gain is require. A 1 kW prototype is developed, the input voltage ranges from 80 V to 200 V, the output voltage and output power are 400 V and 1 kW, the experimental result shows that the full-load efficiency can reach 96.5% over the entire input voltage range, and the peak efficiency can reach 96.9% at full-load state.INDEX TERMS resonant converter; photovoltaic; wide input voltage; high efficiency; DC/DC conversion.
Under partial shading conditions (PSC), conventional maximum power point tracking (MPPT) methods of photovoltaic array (PV) cannot be used to extract the global maximum power point (GMPP). Under uniform conditions (UIC), intelligent MPPT methods are time-consuming for tracking the MPP. This paper describes a potential zones firefly algorithm (PZFA) that can rapidly and accurately extract the GMPP under partial shading conditions and uniform conditions. The algorithm introduces the conceptions of potential and non potential zones;and devises zones maximum power estimation mechanism. Based on the zones maximum power estimation mechanism, the iterative mechanism of PZFA is designed, which can avoid the algorithm searching in non potential zones, quickly narrow the search zones of the algorithm, and ensure that the algorithm converges to GMPP quickly. Finally, simulation results indicate that the promoted PZFA can immediately and accurately track the GMPP under under partial shading conditions and uniform conditions, and the array output efficiency can be improved.
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