Research On Key Issues Of Low-cost Vector Control Syetem Of Permanent Magnet Motor

The vector control system of sinusoidal permanent magnet motor receives much concern of international and domestic academics with its superior performance. In many applications with cost demand, such as electric bicycles, the cost of position sensor, current sensor, driving circuit becomes the main restriction of its application.To obtain exact rotor position information, resolver or encoder is required, but it raises system cost. By contrast, switched hall position sensor has the advantages of low cost. But its continuity is poor, which affects motor running performance. Therefore, this paper obtains high resolution position information by zero order estimation algorithm. On this basis, some optimization algorithm is introduced in thesis to improve the precision of rotor position information.Three-phase current should be obtained in vector control system. Because of cost concern, sampling resistor is used to substitute for hall current sensor. To obtain maximum modulation ratio and raise efficient use of DC supply voltage, the algorithm of current sampling via three shunt resistors or on resistor of MOSFET is studied. The algorithm mainly analyzes the distribution of current sampling point. To further reduce cost, the reconstruction method based on the single resistor bus current sampling is studied. Combined with characteristics of single resistor current sampling, a control method of inserting effective vector was proposed to make the current reconstruction realized in whole region.For motor drive system by the battery power supply, the speed of the motor output restricted by DC voltage. To broaden the speed range, this paper designs closed-loop control based on DC bus voltage feedback; This paper researches sensorless permanent magnet motor drives based on Back-EMF method; Considering of the problem of motor starting, the method of short-term voltage vector injection is proposed; Then, the influence of after-flow diode to the detection of zero-crossing of Back-EMF is presented. To enhance braking performance, this paper designs flexible electrical regenerative braking. A system experimental test has been done for proposed optimization algorithm. And experimental results reveal the effectiveness of the proposed schemes.