A half-bridge photovoltaic (PV) system is proposed, which can not only deal with bidirectional power flowing but also improve power quality. According to varying insolation, the system conditions real power for dc and ac loads to accommodate different amounts of PV power. Furthermore, the system eliminates current harmonics and improves power factor simultaneously. As compared with conventional PV inverter, the total number of active switches and current sensors can be reduced so that its cost is lower significantly. For current command determination, a linear-approximation method (LAM) is applied to avoid the complicated calculation and achieve the maximum power point tracking (MPPT) feature. For current controlling, a directsource-current-shaping (DSCS) algorithm is presented to shape the waveform of line current. Simulation results and practical measurements also demonstrate the feasibility of the proposed half-bridge PV system.
Abstract:In this paper, a power supply system for hybrid renewable energy conversion is proposed, which can process PV (photovoltaic) power and wind-turbine energy simultaneously for step-down voltage and high current applications. It is a dual-input converter and mainly contains a PV energy source, a wind turbine energy source, a zero-voltage-switching (ZVS) forward converter, and a current-doubler rectifier. The proposed power supply system has the following advantages: (1) PV-arrays and wind-energy sources can alternatively deliver power to the load during climate or season alteration; (2) maximum power point tracking (MPPT) can be accomplished for both different kinds of renewable-energy sources; (3) ZVS and synchronous rectification techniques for the active switches of the forward converter are embedded so as to reduce switching and conducting losses; and (4) electricity isolation is naturally obtained. To achieve an optimally dynamic response and to increase control flexibility, a digital signal processor (DSP) is investigated and presented to implement MPPT algorithm and power regulating scheme. Finally, a 240 W prototype power supply system with ZVS and current-doubler features to deal with PV power and wind energy is built and implemented. Experimental results are presented to verify the performance and the feasibility of the proposed power supply system.
OPEN ACCESSEnergies 2013, 6 4860
In this paper, a boost converter with a transformer capacitor cell for implementing features of double-output sources and zero-voltage switching (ZVS)/zero-current switching (ZCS) is proposed. The proposed boost converter has the following advantages: (1) By incoporating a transformer capacitor cell, the main switch can achieve ZVS and the auxiliary switch can achieve ZCS under turn-on transitions, reducing switching losses and electromagnetic interference (EMI). Therefore, the conversion efficiency and power quality of the proposed boost converter can be increased. (2) By applying the turn ratio of the transformer, the proposed boost converter can obtain double-output sources with step-up and step-down voltage functions. (3) The leakage energy of the transformer can be recovered using a capacitor, and then the energy of the capacitor can limit the reverse recovery current of power diodes, reducing reverse recovery losses. Finally, a boost converter prototype with a transformer capacitor cell for implementing the features of ZVS/ZCS and double-output sources is built. The performance and feasibility of the proposed boost converter have been verified from the simulated and experimental results.
In this paper, a high step-up DC/DC converter is proposed, which can boost low PV panel voltage or battery voltage to a high level so as to power the dc side of gridconnected PV inverter. The proposed converter is composed of an inductor, a power switch, and a coupled inductor and is derived from the integration of buck-boost and flyback for high voltage-gain achievement. Even though it possesses buck-boost and flyback features, there is no the problem of reverse voltage polarity and the energy stored in the leakage inductance can be recycled without additional active clamp circuit. Furthermore, since the input source, active switch, and output port are in common ground, the proposed converter has the advantages of easy control-circuit design and simple control-circuit configuration. In particular, the proposed converter can be expanded to multi-layer topology to stack up output voltage such that a much higher voltage gain can be obtained. A prototype, of which input voltage is 48V, output voltage is 400V and power rating is 200W, is built to validate the proposed converter. Experimental results have verified the feasibility and functionality of the proposed converter.
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