Research And Implementation Of Bi-directional DC/DC Converter In Stand-alone Solar Power Systems

Stand-alone photovoltaic system has great economically importance and widespread applications. It is mainly used in communications relay stations, weather stations, frontier sentry, the scattered rural communities away from the power grid and other special locations. It is also used in many photovoltaic products, such as solar street lamps, solar power vehicles and other products. This dissertation is dedicated to the design of the bi-directional DC/DC converter, which implements the power management of battery in the stand-alone photovoltaic system.Firstly, a total solution for the bi-directional DC/DC converter is proposed. The bi-direction Boost/Buck circuit topology is adopted as the topology of the main circuits. The digital-analog hybrid control strategy is determined as the main control strategy module. The analog circuit and the digital circuit based on a MSP430F2274 microcontroller consists the control circuit. The system solution is verified to be practicable through the theoretical analysis.Secondly, the detail excogitation of the hardware is carried out. The hardware project includes the devise of main circuits, sample circuits, signal conditioning circuits, driver circuits, and protecting circuits. A reliable, safe and efficient bi-directional DC/DC converter is planed through the theoretical analysis, high power devices selection and parameter calculation.Thirdly, a control strategy based on the closed-loop control strategy is excogitated. Base on the required module performance and hardware platform, a multi-functional digital-analog hybrid control strategy is designed. The correctness and feasibility of the control strategy is verified though the simulation of charge mode and discharge mode with saber software.Finally, the testing on bi-directional DC/DC module is conducted. The testing results indicate that the maximum charge current is up to 20A, the maximum output power of the discharge mode reaches 5kW. The result of both of the boost mode and the buck mode can meet the required module performance. The bi-directional DC/DC module has excellent steady-state characteristics and dynamic performance.