Research Of The Small Household Photovoltaic Pumping System

Today, energy and environment problems have become one of the important problems of which governments pay attention to. As a kind of renewable energy, the utilization of solar energy has been developing rapidly. With the increasingly shortage of fresh water resources, there are still lots of areas that power grid can not covered in developing countries to have the difficulty in electricity and water. Therefore, it is significant to investigate the photovoltaic pumping(PV pumping) systems with the practical value and social value.On basis of the analysis of the characteristics of photovoltaic panels and the principle of the pumps,a new kind of PV pumping system has developed,in which the PV arrays are used for power supply, a sensorless brushless DC motor(BLDCM) is ultilized as the drive motor, and the microcontroller PIC16F877A is employed as the main control chip. In order to improve the power and efficiency of the PV puming system. In order to improve the power and efficiency of the PV pumping system,the emphsis of the research is put on the MPPT algorithm based on the variable step-size conductance increment method and the variation of the output power of photovoltaic array with the flow rate of pump. In order for the PV pumping system to run stably and reliably, the techniques of the back EMF zero-crossing detection and phase commutation of motor, and3-step starting method are also studied, and a kind of "virtual neutral point" method is used for the detection of back EMF zero-crossing. The way of the combination of the software with hardware is adopted to implement the control of the system.In order to verify the performance of the system, the therotical simulation and pratical test are conducted. The results show that the PV pumping system can always operate in the status of the maximum power,and can start smartly and run efficiently,reliably and stably both in the sunny day and cloudy day.