A 1 MHz half-bridge resonant DC/DC converter based on GaN FETs and planar magnetics is proposed in this paper which improves the system efficiency and power density. The resonant network can achieve satisfactory soft-switching characteristics based on a small impedance angle, which greatly reduces the losses of switches and diodes. The losses characteristics during the turn-on and turn-off transitions are detailed analyzed. The calculation results show that the GaN FETs with low output capacitance and on-resistance can achieve fast switching speed and low losses in high frequency conditions. To reduce the profile and increase the power density of the system, planar magnetics are used in this paper. The Response Surface Methodology (RSM) and Modular Layer Model (MLM) are adopted to help design the planar inductor and transformer respectively. Both of the methods offer clearer and more effective ways to design the planar magnetics. A 25W prototype is built to verify the feasibility of the proposed high frequency converter.
Power quality is the most important problems in power system automation. Aim to analysis and improve the power quality, many types of power quality events, such as voltage unbalanced, harmonic, frequency offset and multiple short time power quality disturbances, should be recorded accurately. This paper proposed a new design proposal of a novel digital fault recorder which could record the power quality waveform signals in 24 hours a day. The original power quality signals are transformed by fast Fourier transforms (FFT) and the waveform distortion is determined by the amplitude spectrum. In order to compression the data of power quality signals, the waveform without distortion is described by the first circle’s waveform. Hence, every power quality events signals and stationary signals will be recorded by one circle signal of each time. Then, the first circle signals of each event are compressed by wavelet transform so as to get higher compression ratio. The signal compressed by DFR will be stored in the Flash or RAM chips and transferred to principal computer. The data will be used for power quality analysis.
DC/DC Switching Converters have been used in many applications in recent years. The Sliding Mode Control based on VSS (Variable Structure System) theory has been examined for all switch mode converter types, whilst Current Mode (CM) control scheme is particularly applied to DC/DC converters. However, these control strategies can't compensate for large load current and input voltage variations. In this paper, a new control strategy by compromising both schemes advantages and avoiding their drawbacks is proposed, analyzed and simulated; and derivation of a dynamic current reference is also carried out. Moreover, considerations for realization with DSP controllers are addressed.Index Terms--Sliding Mode, Current Mode, Buck Converter, Boost Converter. I.
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