Research On The Photovoltaic Dc-module Based On Current-fed Half-bridge Converter

Solar energy has been recognized as the most ideal renewable energy because it is rich and basically no pollution. And the photovoltaic power has been one of the most popular ways to use solar energy. According to the different form, the photovoltaic power system can be divided into centralized type, single-branch type, multi-branch type, PV module type(AC module and DC module) and so on. Among them, the PV Module type attracts much attention because it can solve the problem of partial shadow and improve the utilization rate of photovoltaic panels. Compared with DC module, AC module has problems of high cost, low efficiency, poor quality of the power energy, complex control and so on, so DC module is the development trend of the main PV module type. Because the single photovoltaic panel has the characteristic of low output voltage, so in the photovoltaic DC module we need a high step-up DC/DC converter to transfer the low voltage to the voltage required for the inverter. In this paper, a kind of DC Module based on current-fed half-bridge converter is studied under this background.First the working principle of current-fed half-bridge converter is analyzed. The input parameters are determined according to the output characteristics of PV panel. The design method of main parameters and analysis model of the converter's main losses are given. Based on this, the parameters of the converter are optimized from two aspects: efficiency optimization and high power density. A specific design example of 250 W photovoltaic DC Module prototype based on current-fed half-bridge is given.According to the control demand of photovoltaic DC Module, the overall control scheme of the converter is put forward. And the detailed design method of each part of the control circuit is given. According to the requirement of the switches' drive signal, the PWM control chip UC3637 is selected as the main control chip. The control method of light load is given(frequency-hopping method), and the detailed realization ways are given from two aspects of hardware and software.Finally, simulation and 250 W photovoltaic DC Module prototype based on current-fed half-bridge converter are set up to prove the theory analysis through simulation and experiment. The efficiency curve of the prototype is given and the highest efficiency is 94.3%...