An Embedded Solar Photovoltaic Inverter Based On New MPPT Algorithm

With the rapid development of world economy, traditional energy consumption increases, solar energy which is green energy gets the world's more and more attention. Photovoltaic power generation which is the main utilization form of solar energy has broad development prospects. To further improve Photovoltaic power generation system performance, The structure and working principle and control strategy of a small power independent photovoltaic generation system mainly used in the field areas without electricity are studied.Firstly, the work mechanisms and the output characteristics of photovoltaic cells are analysed in detail, The Matlab simulation model of the Photovoltaic cells is built based on the mathematical model of silicon solar cells, the impact is analysed about the light intensity and temperature on the solar array output performance. To the problems of maximum power point tracking (MPPT) methods currently, this paper presents a new dual-mode MPPT control method:The fixed voltage method which has a good dynamic properties is used when the MPPT starting or sudden changes in the external environment, so that the Photovoltaic array voltage will be regulated to the maximum power point vicinity directly, and then using variable step perturbation and observation method to track fine-tuning. The method combines the advantages of the fixed voltage method and variable step disturbance observation, such as fast tracking changes in the external environment and the maximum power point without oscillation and maximum power point tracking under adverse conditions in the external environment.Secondly, a battery charg and discharge control method based on bi-directional DC/DC converter is proposed in this system. the bi-directional converter is connected with high voltage DC bus terminal in parallel as the charge and discharge circuit of batteries, the battery charge and discharge control is completed by detecting the state of the solar arrays and batteries and load port, the energe scheduling between the Photovoltaic inverter output power and the battery charg and discharg power is also investigated.Finally, the system's software and hardware design of the solar PV inverter based on the embedded technology is completed in this paper. The hardware took ColdFire series of 32 micro-controller MCF52235 as the control core, carried out a detailed design and analysis of the controller minimum system, signal sampling module, power board circuit, the signal drive and the system's auxiliary power. The software selected the modular structure which is based on embedded real-time operating system. The system software was divided into several task modules, the main control board algorithmthe, signal conversion, PWM output tasks, software implementation process of human-machine interface are analysed detailedly and the system software is debugged preliminary.