Active Disturbances Rejection Control Of Field-Oriented Induction Motor Drive System

High performance control of induction motor drives is urgently required forsome applications in modern industry. In this dissertation, researches are focused onhigh performance induction motor drive systems. Aimed to solve the controlproblems of non-linearity and uncertainty existing in such systems, in-depth theoryanalysis, simulations and experiments are performed concerning the rotor fluxobserver, the close-loop controllers and identification of speed and rotor resistance inthe system. In order to obtain robust control performance with quick response, ActiveDisturbances Rejection Control (ADRC) for a field-oriented induction motor drivesystem is proposed in this dissertation, in which the rotor flux observer and theclose-loop controllers are two dominant parts. Rotor flux observation is a key step in implementation of a field-oriented control(FOC) system. To suppress the adverse influence of external disturbances such asmeasurement noises, a rotor flux observer model with a simplified Kalman filter isintroduced. With the structure of combined sub-observers, the complexity of Kalmanfiltering algorithm is reduced. In order to reject the influence of rotor resistanceperturbation, a new rotor flux observer based on an Extended State Observer (ESO)with model compensation is proposed. The perturbationof rotor resistance is taken asa system model disturbance, which can be observed and compensated by ESO. TheESO with model compensation algorithm can change the original open-loopestimation into close-loop observation, with which the flux observation is free of theeffect of rotor resistance variation and the pure integration problem is solved. As aresult, the performance of rotor flux observer based on ESO compensation isimproved to a great degree. The dynamic performance of a FOC system depends on its speed and currentloop controllers. ADRC technology is introduced into the controller design to dealwith the influences of the unknown external disturbances and the coupling items inspeed and current models. The principles of ESO design are proposed to improve - II -AbstractADRC′s performance, with which an ESO with quick convergence and preciseobservation can be realized. In this dissertation, a novel optimized model of thefirst-order ADRC is proposed, and the general rules that govern the selection of itsparameters are also presented. With some non-linear components in the typicalADRC model replaced by their corresponding linear models, the structure of themodel is simplified and its computation load is reduced, thus the practicability ofADRC is greatly enhanced while same dynamic performance is kept at the same time. For the implementation of sensorless FOC, a speed identification algorithm isintroduced on the basis of ESO. By means of the existing structure of ADRC system,speed information is picked up from the observation results of the unknown model inESO. Furthermore, a new rotor resistance identification method is proposed in thisdissertation. With a proper triangular wave injected into the rotor flux reference, rotorresistance can be estimated in a quick and smooth convergence process. As a result,precise identification of speed is achieved. A prototype of the ADRC system for FOC induction motor drives is designedand built, with which experimental investigations are accomplished. Experiment andsimulation results demonstrate the validity of all the methods proposed in thisdissertation.