Research Of Stand-alone Photovoltaic System Based On Bidireectional DC/DC Converter

Accompanying with the rapid expansion of global economy, human are facedwith serious energy crisis and environment problem. Fossil energy is going to beexhausted and human must look for another clear energy. The solar energy hasmany incomparable superiority and will be the most reliable alternative.The paper mainly research the stand-alone photovoltaic lighting system,which is expected to be acting in underground garage. LED bulb is chosen aslighting source. The paper researches several key problems in the system,including the maximum power point tracking(MPPT) of photovoltaic plate, thecharging method of lead-acid battery in photovoltaic system, the energymanagement strategy, and the smart dimming method of underground garage.MPPT is realized with fuzzy control, and simulation is done with Matlab. Theresult of simulation shows that fuzzy control has faster tracking speed and smallerfluctuation of power at steady state, compared with simple perturb andobserve(P&O) method. The MPPT method that use a voltage regulator is comparedwith the method which is realized by directly perturb the duty of MOSFET. Thesimulation shows that the former has better effect than the latter.A kind of charging method for lead-acid battery which suit stand-alonephotovoltaic system is proposed. With this charging method, people can find somebalance between MPPT and the correct charging for battery. The ac small-signmodel of Buck/Boost bidirectional DC/DC converter is built and corrected withMatlab. The work modes of system in different conditions is analyzed, and areasonable energy management strategy is proposed and simulated with Matlab.The result of simulation shows that system works well in different work modes. Inorder to save electricity, a energy-saving and humanizing smart dimming systemfor underground garage is designed. The smart dimming system takes MSP430MCU as controllers and all the controllers are connected through485bus. With thesmart dimming system, people can not only save a lot of electricity but also helpthe owners of cars to quickly find spare parking space.