The Research Of BLDC Motor Control Used To Drive Photovoltaic Pumps

The emphasis of this paper is the commutation control of sensorless BLDC motor, which is used to drive Photovoltaic Pumps.This paper uses "virtual neutral point method" to measure the "zero crossing", then the soft deal "zero crossing" to get the six key position to commutate. It elaborates on the 3-step start technique .I adopt the method which permits the BLDC motor to automatically search the best time to change its operation stage from a separately controlled synchronous one to a self controlled one using the back EMF as the commutation signal. This method prevents the stepping out and stopping problems in the changing procedure of the motor.The sensing for rotor flux position of BLDC motor is the key of commutation, so this paper expatiates on three different methods to sense rotor flux position and compares their advantage and disadvantage.The system uses the microchip PIC16F877 made by Microchip Co.Ltd as a control chip. It fulfills the capture of "zero crossing" point and the multifarious protective functions. It realize the approximately exact commutation of the motor and unmanned supervision of the system.At the end of this paper, I put forward a new back EMF sensing method which doesn't require a virtual neutral point to realize The sensing for rotor flux position. It improves the performance of BLDC motor at low speed and at high speed and broaden its range of timing.