Ikuo Takeda

Vector control for induction machine on the application of optimal control theory

An approach for constructing a field-oriented control system using the state-space method is proposed. The field-oriented control system can be realized by coinciding the synchronously rotating reference frame with the axes of the secondary flux linkage reference frame and by simultaneously but independently adjusting the three control inputs. A control-system synthesis method that achieves speed control, field-oriented control, and constant flux control simultaneously is presented. The control system has a full-state feedback structure and is synthesized by applying a multi-input and multi-output optimal regulator theory. The excellent robustness of the constructed system results in zero steady-state errors for changes in parameters such as rotor resistance. The validity of the control scheme is verified by simulation studies. Results are presented for a field-oriented induction motor driven by a PWM (pulse-width modulation) inverter. >

A new model of saturated synchronous machines for power system transient stability simulations

This paper presents a new method to express the main flux saturation in synchronous machines. In the new method, the saturation is expressed by auxiliary currents and unsaturated magnetizing inductances instead of the saturated inductances. The new model using the currents contains only constant coefficients defined in terms of the unsaturated magnetizing inductances. >

New approach to the steady state stability analysis of synchronous machines

A novel method for steady state stability analysis of synchronous machines is presented. The method is based on a novel swing equation, which is a second-order, nonlinear differential equation. Two steady-state stability criteria can be derived by evaluating the eigenvalues of a linearized version of the new equation, one of which is for step-out instability and the other for hunting. Although these two instabilities have mostly been discussed independently so far, this approach makes it possible to handle the two instabilities on a common basis. >

A synchronous machine model for unbalanced analyses

This paper presents a new asymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power systems. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with asymmetrical impedance, it may not be easy to use the symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under asymmetrical conditions in detail by using the symmetrical component method, then derives a model of synchronous generators for the phase coordinate method.

A new method to approximate stator transients of synchronous machines in power system simulation

This paper presents a new method to approximate the effects of stator transients of synchronous machines in power system transient stability simulations during unsymmetrical faults. This method can approximate the DC offset currents which arise from the stator and network transients during faults. However, the method is based on the traditional model with stator and network transients neglected.

A new synthesis method for efficiency optimized speed control system of vector-controlled induction machine

An efficiency optimization is carried out for an induction machine, treating it as a three-input, two-output controlled object. The condition for maximum efficiency is analytically derived as the ratio of control input and the state variable of state equations in a synchronously rotating reference frame. A synthesis method that attains maximum efficiency and very fast response by simultaneous vector control and speed control is proposed. Simulation results for an equivalent DC model are reported that show the effectiveness of the method.<<ETX>>

A New Approach For Constructing A Vector-Oriented Control Theory By State Space Method

This paper presents a new attractive approach for a vector control system of AC machine by state space method. First state equations of an induction machine suitable for the current control are derived. It becomes clear that the induction machine can be described as three input-three output controlled object. New vector control theory is formed and developed based on an optimal regulator technique. The proposed control system have excellent characteristics for changes in the desired signal and disturbance signal, and in spite of parameter variations of the controlled object. Several simulation results are presented.

A new method in power system simulation to approximate transients of the synchronous machines stator

Abstract This paper presents a new method to approximate the effects of synchronous machines stator transients in power system transient stability simulations. The method can approximate the DC offset currents which arise from the stator and network transients during three phase short circuit faults. However, the method is based on the traditional model with stator and network transients neglected.