Parameters Identification Of Induction Motor And Its Use In Variable-frequency Speed Regulation System

AC variable frequency speed regulation system has the characteristics of superior speed adjustment performance, extensive applicability and significant energy saving effect, is more and more valued by various application fields, it has become the mainstream of research and development in electrical drive area. While pursing higher control performance, motor parameters change problem has become an increasingly important issue. Conventional motor parameters measurement method is trivial and complicated, and improved method based on frequency converter implement off-line parameters identification at non-work state, can not reflect the parameters’dynamical change with the work state of motor, and incapable of meet the requirements of precise real-time track of parameters. Therefore, on-line induction motor parameters identification become an intrinsic need and study focus of high performance motor control, it has an important meaning to increase motor control effect furthermore.Aimed at off-line and on-line induction motor parameters identification methods and its application in variable-frequency speed regulation system are studied in this paper with main contents as follows:1. Development and current Status of study of AC variable frequency speed regulation and induction motor parameters identification methods are reviewed and summarized. From the point of real need of high performance drive strategies, necessity of parameters identification is clarified. Characteristics and adaptability of various off-line and on-line induction motor parameters identification methods are presented and analyzed.2. Basic formulas of vector control are deduced, traditional and its improved off-line parameters identification methods are analyzed. From the mathematical model of induction motor, parameters that affect high control performance are determined and analyzed. In consideration of accuracy improvement, parameters identification method based on frequency converter is discussed detailed; some modification is done to decrease the impact of various factors, and make it more easily to realize.3. A rotor flux observe method based on nonlinear quadrature double compensation is presented. Focused on vector control strategy, flux observation which is significant in control system but easily be affected by parameters change is studied, the source of error is analyzed. The new method presented is based on the modification of conventional voltage flux observer model, in which compensation is done according to the quantity of flux observation error, track speed when signal frequency changes dramatically is also improved.4. An on-line induction motor parameters identification method based on Elman neural network is presented. Elman recurrent neural network is capable of nonlinear function approximation and possesses the ability of time-variable characteristic adaptation, is fit for motor parameters identification. The influencing factors of specified parameter are analyzed respectively, and various work states are considered to ensure the completeness of the training samples. Process method of samples and training data is introduced, single and multi parameters identification with one network is compared, and a network structure suit for this problem is obtained.5. The build of the whole induction motor variable-frequency dive system is presented, from the hardware circuit perspective-schematic diagram design and the selection of devices, and from the DSP software program compilation perspective. Some simulation and experimental results and illustrations are also presented.