Research On Improved H Bridge Buck-Boost Converter In PV System

Increasingly severe energy crisis makes the rapid development of photovoltaic power technology. Photovoltaic power have the characteristics of high cost and low photoelectric conversion efficiency which restricts it instead of the traditional ways of power generation, including thermal power and hydroelectric power, and hinders the commercialization process. DC/DC converters in the photovoltaic power system have the goal of maximum power tracking. In view of the wide range of photovoltaic cells output voltage, this paper uses the Buck-Boost converter in the photovoltaic power system, and adopts the hybrid control strategy. An improved H bridge Buck-Boost converter is adopted to decrease the power loss in direct mode of hybrid control strategy.The working principle of the improved H bridge Buck-Boost converters and synchronous control strategy and hybrid control strategy is analyzed in this paper. Finally, the multi-mode control method is adopted. The output characteristics of photovoltaic cells and the maximum power tracking algorithm are analyzed theoretically. The model of photovoltaic generation system is established in Simulink, and the Perturbation and Observation method is adopted to realize the PV maximum power tracking.The software and experiment platform of the improved H bridge Buck-Boost is designed and built based on TMS320F2812. In the buck mode and boost mode, respectively according to the changes of the external environment, load changes, the paper discussed the typical case of maximum power tracking. The loss of direct model is compared between the ordinary converter and the improved H bridge Buck-Boost converter.Experimental results show that the converter has good stability, which can quickly track the maximum power. In the impact of external disturbing, it can also fast track o the maximum power. The loss analysis shows that the converter can reduce the loss in direct mode, and improve the efficiency.