Abstract
Electrically excited synchronous motor (EESM) has the characteristics of high order, nonlinear and strong coupling, so it is difficult to be controlled. However, it has the advantages of adjustable power factor, high efficiency, and high precision torque control, so it is widely used in high-power applications. The accuracy of a flux observer influences the speed control system of EESM. Based on state observer in modern control theory and electrical excitation synchronous machine state equation, a reduced-order flux observer is designed. Using the first-order difference method and forward bilinear transformation method, the reduced-order flux observer is discrete, and the stability of the motor system is analyzed. The analysis shows that the stability of the system using the bilinear transformation method is better than that using the first order forward difference method. In motor operation, motor parameters will be affected by the factors of temperature, magnetic saturation, and motor frequency. In this paper, the influence of parameter variation on the motor system is studied by using the variation of the pole distribution. Finally, the speed regulation system using the reduced-order observer is simulated, which verifies the accuracy of the reduced-order flux observer observation.
Highlights
With the continuous development of the world economy, the problem of energy consumption has attracted extensive attention from scholars [1,2,3]
Since the state observer is based on the state equation of the motor, it depends very much on the parameters of the motor, so this paper analyzes the stability of the speed regulation system of the electric excitation synchronous motor under the change of the parameters of the motor
Since the reduced-order flux observer is based on the state equation of the motor, the state equation of the excited synchronous motor (EESM) is firstly obtained, and the state equation requires the flux as the state variable
Summary
With the continuous development of the world economy, the problem of energy consumption has attracted extensive attention from scholars [1,2,3]. The advantages of the traditional method include simple control structure, fast torque dynamic response, low parameter sensitivity and no need for rotation coordinate transformation, etc., and disadvantages include low-speed torque observation error, large flux observation error, large current pulsation, etc. In the electrical excitation synchronous motor (EESM) speed control system, regardless of vector control and direct torque control, it is needed to obtain accurate information about the magnetic chain. The flux observer design of electric excitation synchronous motor speed control system has a great influence [38,39,40]. The first-order forward difference method and bilinear transformation method are used to discretize the reduced-order flux observer, and the influence of the change of motor parameters on the stability of the motor system is analyzed.
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