The Research On Direct Torque Control System Of Brushless Doubly-fed Machine Based On Dsp

Brushless doubly-fed machine (BDFM) is a new kind of special machine which can operate on asynchronous and synchronous state. The different operating mode of BDFM can be modified by adjusting the frequency, amplitude value of the voltage in the stator control winding. BDFM can operate on brushless doubly-fed operation state, which improve the reliability of system. It can be used in AC adjustable-speed drive systems as a motor or be used in adjustable speed constant frequency system as a generator. The BDFM system has the characteristics of less capacity inverter, separately adjustable active power and reactive power, as well as power factor, so it will widely used in high-capacity variable frequency adjustable speed drives systems and adjustable speed constant frequency generator systems. In this paper, flux observer, torque observer, power factor, steady-state characteristics, transient characteristics were studied. Main research work is as follows:1.Flux observer is the key of direct torque control system of BDFM. It directly affect the success or failure of control strategy.,Based on studying the feedback and compensation of high-pass filter the u-i model, This paper proposed a feedback compensator is different from the high-pass cutoff frequency part of the flux observer method.The method solved the problem that the u-i model flux observer was inaccurate at low frequencies more effective, experimental results showed that the method achieved good control effect.2.Torque observer is also the key to the direct torque control system, as opposed to the current literature, the observation approach was built in the dqo rotor speed coordinate system. This paper propose a torque observer approach in theα,βstationary coordinate system. the method avoided the rotating coordinate transformation, effectively reduced the computational procedures, improved the control precision. Experimental results showed that the super-synchronous and sub-synchronous operating state have achieved good control effect.3.In the inheritance of this group on the basis of realized based on direct torque control of brushless doubly-fed motor speed control. Experimental results show that speed range expansion, increased power of resistance and maintained the advantage that quick dynamic response of direct torque control,compared to the open-loop control system.4.Based on the realization of BDFM direct torque control of brushless doubly-fed motor. Study the power factor under different running characteristics of the simulation and experiment. On the control winding flux given in different and load such changes, a large number of experiments for the power factor showed that the value of flux given could regulate the size of power factor also regulate the nature of reactive power. 5.An exploratory study was launched on the BDFM of start characteristics. For asynchronous start and then pull into doubly-fed operation and the method of doubly-fed variable frequency starting. Focusing on the impact that different control winding flux controlled the motor pulling into double-fed process and the starting process of double-fed variable frequency. Simulation and experiments showed that different control winding flux given had the different impact on the two starting methods, but at the same experimental conditions, the transient process was different that pulled in the double-fed from asynchronous at different times.