Showing papers by "Seung-Ki Sul published in 1992"

Speed sensorless vector control of an induction motor using an extended Kalman filter

Abstract: The vector control of an induction motor by speed estimation using an extended Kalman filter (EKF) is described. The rotor speed is regarded as a parameter, and the composite state is composed of the original state and the rotor speed. The EKF is employed to identify the speed of an induction motor and rotor magnetic flux based on the measured quantities such as stator currents and DC link voltage. The estimated speed is used for vector control and overall speed control. The current control is performed in the synchronous rotating reference frame, and the estimated speed information is used for reference frame transformation of the current controller. Computer simulation of the speed control has been carried out to confirm the usefulness of the speed estimation algorithm. The error between the real speed and the estimated speed is within a few RPM even in the low speed range of about 20 RPM. >

High performance current regulator for a field-oriented controlled induction motor drive

Abstract: In this paper, a novel strategy of current regulation of a field-orientation induction motor drive using the GTO inverter is proposed, which is based on a multivariable state feedback control with an integrator. The controller is designed by pole placement technique of multivariable system regulation theory. In addition, feedforward control is included in the control laws to improve transient responses. For the linear state feedback control, the rotor flux is separated as a disturbance and is estimated with a reduced-order state observer. A good steady-state performance is obtained by means of an integral compensation and symmetrical space voltage vector PWM, and fast transient response is also feasible since the required voltage is directly calculated from the feedforward control. Also, it is demonstrated that an instantaneous current control without the calculation time delay can be implemented. The excellence of the proposed current regulation scheme is verified by experiments for the GTO inverter-fed induction motor drive system controlled by a DSP-TMS320C30. >

Novel Current Regulation for a field-Oriented Controlled Induction Motor Drive

Abstract: In this paper, a novel strategy of current regulation is proposed that utilizes a voltage model of induction motor and compensates for the current deviation due to the non-ideal behaviors of inverter and the difference between the voltage model and real system with PI controller. A good steady-state performance is obtained by means of an integral compensation and fast transient response is also possible since the required voltage is calculated from the voltage model directly. The other aspect of current regulation, i.e. modulation part, is how the control voltage will be generated from PWM inverter. It is known that space voltage vector method yields more exact inverter output voltage than ramp-comparison PWM in high modulation index. So, this method is adopted as a switching strategy. In addition, the variable modulation scheme is presented which is changed from three phase to two phase modulation at high modulation index.

A load commutated inverter-fed induction motor drive with a novel DC-side commutation circuit

Abstract: A load commutated current source inverter (LCCSI) induction motor drive system employing a novel DC-side forced commutation circuit for machine startup is proposed. To avoid the adverse effects of the induction motor, a solution is proposed, i.e., using a special kind of one-notch current pulse width modulation (PWM) fully utilizing the proposed commutation circuit. Along with compensating the capacitive current, the direct vector control referred to the rotor flux fixed reference frame without speed sensor is used to decouple torque and flux generation currents and to overcome the problem of instability caused by the output capacitor. The availability of the proposed circuit for a high-power drive system is verified by computer simulation for a 600 hp induction motor. >

Sensorless Vector Control of a Load-Commutated Current Source Inverter-Fed Induction Motor Using V/f Control for Starting

Abstract: A new load-commutated current source inverter(LCCSI)-fed induction machine drive is presented,using three phase capacitors connected to the motor,To drive a large induction motor, which is usually high voltage machine,the step-up transformer is used because of the limitation of switching element's voltage rating. In this system, the performance of machine control is effected by the ouput transformer and output capacitors. A speed sensorless direct-vector control scheme, with either torque and flux loops or capacitive currnet compensation has been tested In simulation. V/f control for starting is also done to prevent flux's saturation of output transformer and overcome the effect of low signal level at low frequency.