Researches In DTC System Of PMSM

The permanent magnet synchronous motor (PMSM) has been widely used in the national defense, the industrial control, daily life and so on, because of its inherent advantages of high efficiency, simple structure and reliable performance. Recent years, the reduction of the permanent magnetic material and machine manufacturing cost, the improvement of the control theory and hardware design and the development of the microprocessor have provided PMSM and its drive system in further application with favorable conditions.In China, most of the oil fields are low-energy and low yield. The general method is injecting water to pressure oil into the well, and then take up the oil from the bottom by the oil pumping unit. Traditional pumping equipment is the beam pumping unit, usually use asynchronous motor as its power machine, its defects are "pulling small car with big horse" and low power factor. Therefore, the production cost is very high. With the PMSM instead of asynchronous motor as the power is an ideal choice for the energy saving. This paper do some researches on the theory, scheme and the concrete technology of PMSM direct torque control(DTC) system, do the corresponding simulation, and proved the preliminary feasibility of the scheme. The paper do the following work:Firstly, the paper introduces the present application of pumping unit and the application of PMSM to pumping unit, then discusses the configuration of PMSM and its mathematical model in different coordinate, and describes the principle of coordinate transformation.Secondly, the postulate of DTC is analyzed, and the simulation model is built based on the parameter of PMSM. And the paper using MATLAB do simulation to the PMSM DTC system by imitate the system of pumping unit, the simulation are divided into two situations: with the zero voltage vector participate in the control and without it participate in, and then comparatively analyze the simulation waveform.Finally, for the problem of torque ripple, a new DTC system based on fuzzy logic is proposed and simulation results show that the torque ripple is decreased drastically.The simulation results demonstrate its rationality.