Research On 12-Phase Cycloconverter-fed Synchronous Motor System

Variable speed system of cycloconverter-fed multiphase synchronous motor is a major area in the development of high-power AC drive system because of its small dimension, large capacity, high torque, high-rate power, wide-range variable speed, low harmonic pollution, and reliable safety. In the low-speed and large-capacity industrial drives, such as rolling mills, winding motors, marine propeller, cement mixer, etc. it will find a wide application in the future. This paper makes a thorough study on the control system performance, rotor position detection and rotation speed, taking the cycloconverter-fed 12-phase synchronous motor as an example, which provides the theoretical and experimental basis for the design and operation of the system. Firstly this paper introduces the vector control strategy of 12-phase synchronous motor. The mathematic model of 12-phase synchronous motor dq frame, switching function model of 12-phase cycloconverter and vector control model of the system are established based on this gas-flux-oriented principle. On the base of the vector control strategy and mathematic model of 12-phase cycloconverter-fed synchronous motor system, the simulation model is established and the parameters of current controllers, speed regulator, gas-flux regulator and excitation current regulator are designed respectively. The simulation results of the vector control strategy and dynamic character prove that the control strategy is correct and the parameters of the regulators are feasible. The theory and method of the rotor position detection and rotation speed based on absolute photoelectric encoder are introduced. The circuit and program of the rotor position detection and the rotation speed measurement using M/T method are also designed, and the experiment result shows the accuracy of the system of the rotor position detection. The vector control software of 12-phase cycloconverter-fed synchronous motor system is designed according to the fully digital variable speed system, based on two-level DSP. The arithmetic of the digital PI regulator and digital control of exciting current are also provided. The experiment results of the steady and dynamic character show that the system has perfect control and operation performance.