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The Current Vector Control Strategy For Induction Motors With Stator Flux Orientation

Posted on:2001-11-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:H M XieFull Text:PDF
GTID:1102360122996239Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
It is well known that the rotor parameters in induction motor are subjected to variability and hard to be measured, which more or less deteriorate the performance of such control systems based on the mathematical model depending upon rotor parameters.One method to improve the robustness of control system is to employ stator flux control. The main reason is that the only parameter in stator flux model is the stator resistance, which can be measured on line. Thus better robustness in flux observation can be ensured in theory. Up to now, several motor control systems with stator flux control based on dynamic models are developed, such as direct torque control (DTC), indirect self-regulation (ISR) and direct stator flux orientation control (DSFO). Because of various control means, their control performances are dissimilar. As for bang-bang control, DTC has poor performance in low speed range. ISR and DSFO can not completely avoid the dependence upon rotor parameters.This paper present a novel control scheme: the current vector control strategy for induction motors with stator flux orientation (CCSFO), which not only can avoid the dependence upon rotor resistance and rotor time constant, but also remain high dynamic performances. It becomes a new control strategy, which combines the advantages of VC(vector control) and DTC, at the same time overcomes their defects. The main contents and conclusions are as follows:The dynamic model of induction motor is investigated. Various equivalent circuits and state equations are proposed by using differentmethods of conversion for parameters from rotor side to stator side.According to the flux acceleration principle, the influence of rotor parameters on the performance of vector control system with rotor flux orientation is analyzed. Then a voltage vector control scheme for induction motors based on constant stator flux is presented and it's nonlinear limitations are analyzed.Based on the analysis of the relationship between current and flux variables in induction motors, a stator flux-oriented current control scheme is presented instead of voltage vector control. This novel scheme achieves circular stator flux track and continuous torque regulation, which produce less torque ripples than that in DTC. It also reduces dependence on rotor parameters, and is especially insensitive to rotor resistance variation, thus robustness of the system is improved.The stator flux observation models are studied to indicate their advantages and disadvantages. Some new observation methods are introduced.The effects of inverter dead-time, - and high orderedharmonics on performance of control system, on the motor and on other outside equipment are analyzed. Some strategies of restraining these negative influences are given.Implementation of stator flux-oriented current control system on TMS320F240 EVM is made. Lots of experiments in lab show its good dynamic and static performances. The excellent ability to resist the disturbance of load is also shown.
Keywords/Search Tags:vector control, direct torque control, indirect self-regulation, direct stator flux orientation control, flux acceleration principle, robustness, inverter, dead-time effect, harmonics
PDF Full Text Request
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