现代电力电力技术课件第9章.ppt

Chapter 9 Kouhei Ohnishi, Nobuyuki Matsui, Yoichi Hori AC drives became more and more economical and popular. Since the early years of the 20th century, electric motors for variable speed drives have been widely applied in large-capacity applications the steel industry the automobile industry In the early stage, DC motors were widely used for adjustable speed control Since the late 1960s, AC motors have been replacing DC motors in a wide area of industry applications Since AC drives required more complicated controllers in the beginning, they were not so economically feasible Allied to advances both in digital control technology and power semiconductor devices, AC drives became more and more economical and popular. In almost all areas, DC drives are now replaceable with AC drives To overcome torque problems….… However, there still exist some areas which are not suitable for AC drive applications. One of these is the area which requires precise torque control. For instance, injection machines. AC motors sometimes generate torque error or torque pulsation due to some parameter variations. To overcome such problems, more sophisticated techniques are necessary in the controller. These techniques are based on estimation or identification of motor parameters Employ the recent developments in digital control, including high-speed digital signal processors (DSPs) and parallel processing 9.2 PARAMETER ESTIMATION IN AC DRIVES 9.2.1. Parameter Identification In Brushless Motors 9.2.2. Parameter Identification In Induction Motors Parameters of Brushless Motors The control scheme of brushless motors with trapezoidal flux distributions (BLDM, brushless DC motor) is relatively simple. Usually it does not need parameter identification. For brushless motors with sinusoidal flux distribution (PMSM, permanent magnet synchronous motor), generally identification of the parameters is necessary for precise control . (3 electric parameters) Armature resistance, armature i