| Renewable energy exploitation has become the key research area in all fields to mitigate energy crisis and environmental pollution.Photovoltaic(PV)power generation has already been an indispensable candidate of energy development in many countries since the solar energy is the most abundant and the most widely-spread energy resource in the world.DC-DC converter working as an important conversion interface of the PV power system affects its efficiency and operation security directly.Traditional DC-DC converter is almost composed of energy storage elements,like low frequency isolation transformers and inductors or capacitors with big value.It is featured by a low voltage gain,a large volume,low efficiency and high cost.Therefore,the research on DC-DC converter with high voltage gain,high efficiency,small volume and high reliability is significant for improving the performance of the PV power system and promoting the development of PV industry.This paper proposes a novel high step-up low-ripple DC-DC converter.The research focuses on the soft switching realization and the closed-loop control system of the DC-DC converter.First,this paper proposes the DC-DC converter which is appropriate for large current and low voltage applications,like PV power system and fuel cell system.The circuit topology and pulse-width modulation plus phase angle shift(PPAS)control of the proposed DC-DC converter is introduced.In addition,the equivalent circuit of each operation stage is presented to analyze the working principle and the soft switching realization of the proposed DC-DC converter.The simulation and experiment results have demonstrated that the proposed DC-DC converter works with a high voltage gain,a low-ripple input current and a low-ripple output voltage.The soft switching realization is validated with PPAS control,which greatly reduces the efficiency loss of the proposed DC-DC converter.Then,this paper realizes the circuit topology optimization of the proposed DC-DC converter by removing the parallel inductor.The parameters design and components selection are executed for the optimized DC-DC converter.The simulation and experiment are carried out and the results prove that the optimized DC-DC converter has the characteristics of high voltage gain,low ripple and soft switching.In addition,its efficiency is improved compared to the proposed DC-DC converter.In the end,this paper designs and analyzes a closed-loop PID control system of the optimized DC-DC converter.The PID control system based on TMS320F2812 is introduced.Moreover,the PWM pulse generation and the software implementation are presented.The PID control system is proved to have several advantages,such as minimal stable error,short equilibrium time,constant frequency and high-speed dynamic response,which makes contribution to the safety operation of the PV power system. |
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