T. Irisa

A novel approach on a parameter self-tuning method in an ac servo system

Abstract This paper describes a newly developed parameter identification method for three-phase induction machines. The identification is performed in two steps corresponding to the two states of the machine, namely the initial standstill state and the normal operating state. In each step, on-line identification of parameters indispensable to description of the machine dynamics can be realized by observing the behaviour of the stator current and voltage. These parameters are stator winding self-inductance, transient inductance, rotor circuit time constant and stator winding resistance. At standstill state, they are identified from the stator voltage waveform, when a ramp current is supplied to the stator by a dc power amplifier. At the operating state these parameters are identified by solving a set of equations obtained from the phasor relationship between stator current and voltage. This identification technique is applied to a PWM drive system and can lead to parameter self-tuning in an ac servo control system.

Reliability of Induction Machines for High Performance Based on Parameter Characteristics

Nowadays induction machines of enclosed slot rotor structure are widely utilised and are also being applied to ac servo drive for high performance. However, since in this types of machines local magnetic saturation is found at relatively small flux levels due to its rotor structure, the parameters have large discrepancies in their values depending on the identification methods. Moreover, stator current is much more distorted immediately after a stepwise change in the stator voltage. This means that distortion of the flux is enhanced even if stator current is controlled sinusoidally.

Effects of Structural Error on Dynamic Stability in Both Slip Frequency Control and Field Orientation Control of Induction Motor Drive

Abstract This paper investigates the effects of structural error on dynamic stability in both slip frequency control and field orientation control of induction machine drive system. Their systems are sustained with error effects of two types: one is identification error on motor parameters and the other detection error on rotor speed in slip frequency control and position of rotor flux on field orientation control. If their effects can be overcome and current control can also be achieved, stability problem does not exist necessarily. However, they are unavoidable due to unique control strategy of having feed forward loop of state variables although the problem of current control is almost solvable by adopting PWM inverter control. The stability problem is essentially caused by interactions between rotor motion and electrical dynamics in rotor circuit. So focusing the attention on dynamics of elctrical torque and rotor motion, their problems are investigated in this paper. As a result, differences on characteristics existing between these two control strategies are revealed remarkably. For their analysis, linearization technique at operating point is applied.

A Novel Approach on Parameter Self-Tuning Method in AC Servo System

Abstract This paper describes a newly developed parameter identification method of induction machine. Identification procedure consists of two steps: one is at initial state of standstill and the other is at operating state. In each step, on-line identification of parameters indispensable to description of machine dynamics can be realized by observing behaviors of stator current and voltage. They are stator winding self-inductance, transient inductance, rotor circuit time constant and stator winding resistance. At standstill state, they are identified from stator voltage wave to ramp current. At operating state these parameters are also identified by solving a set of equations obtained from vectorial relation between stator current and voltage. This identification technique is applied to PWM drive system and can lead to parameter self-tuning in ac servo control system.

CURRENT ZERO POINT DETECTION IN NONCIRCULATING CYCLOCONVERTER BASED ON DYNAMIC CHARACTERISTICS OF THYRISTOR-DIODE SERIES CIRCUIT

We have presented a new detection principle of output current zero point in noncirculating cycloconverter(NCC) on the assumption of induction or synchronous machine drives. It is based on difference of reverse recovery characteristics between thyristor and diode in series connection, and zero point is detected by means of reverse voltage impressed at diode terminals. This paper investigates the detection characteristics in more detail. Combinations of thyristor and diode affect the voltage in fairly large degree. When the voltage is impressed, thyristor connected to the diode in series has already been in off state. Snubber circuit removes the restriction imposed on the combinations.

EFFECTS OF STRUCTURAL ERROR ON DYNAMIC STABILITY IN BOTH SLIP FREQUENCY CONTROL AND FIELD ORIENTATION CONTROL OF INDUCTION MOTOR DRIVE

This paper investigates the effects of structural error on dynamic stability in both slip frequency control and field orientation control of induction machine drive system. Their systems are sustained with error effects of two types: one is identification error on motor parameters and the other detection error on rotor speed in slip frequency control and position of rotor flux on field orientation control. If their effects can be overcome and current control can also be achieved, stability problem does not exist necessarily. However, they are unavoidable due to unique control strategy of having feed forward loop of state variables although the problem of current control is almost solvable by adopting PWM inverter control. The stability problem is essentially caused by interactions between rotor motion and electrical dynamics in rotor circuit. So focusing the attention on dynamics of elctrical torque and rotor motion, their problems are investigated in this paper. As a result, differences on characteristics existing between these two control strategies are revealed remarkably. For their analysis, linearization technique at operating point is applied.