US 6,396,229 B1 · Method of estimating a rotor position of synchronous motor, method of controlling synchronous motor with no position sensor and a controller of synchronous motor

Abstract

In a method of accurately estimating the rotor position of a synchronous motor having saliency from observable quantities, a control system for adjusting an output frequency of an inverter on the basis of a value of axis shift of the synchronous motor to operate the motor synchronously with the output frequency is provided with an induced voltage estimating/axis shift operating unit. Currents resulting from conversion of detection currents on a control axis, voltage commands to be inputted to an inverse converter and a speed command are inputted to the operating unit to estimate an induced voltage of the motor 2 and determine the axis shift from a phase of the estimated induced voltage. By using an electrical constant Lq of inductance, a voltage drop across the inductance is determined by the product of a motor speed command and magnitude of motor current. The voltage drop is a virtual quantity that does not depend on the motor rotor position. A vector of the virtual quantity is so introduced as not to change a phase of the original induced voltage.

Claims24

Dependent claims

A method of estimating a rotor position of a synchronous motor comprising the steps of:

when estimating an induced voltage of the synchronous motor having saliency from a vector difference between a motor applied voltage and voltage drops due to resistance and inductance of a motor winding, using a predetermined value as said inductance to determine said voltage drop due to inductance as a quantity dephased by a predetermined amount from a motor current;
and
calculating the phase of the induced voltage from the estimated induced voltage to estimate the rotor position.

A method of estimating a rotor position of a synchronous motor having saliency and controlling the synchronous motor without resort to position sensor, comprising the steps of:

when estimating an induced voltage of said synchronous motor from a vector difference between a motor applied voltage and voltage drops due to resistance and inductance of a motor winding, using a predetermined value as said inductance and determining said voltage drop due to inductance as a quantity leading a motor current by a predetermined phase;
and
determining a phase of an estimated induced voltage and on the basis of the fact that this phase indicates an axis shift angle between a virtual rotor position from the control viewpoint and an unobservable actual rotor position, decreasing a frequency of the motor applied voltage to decrease the rotation speed of the virtual rotor position when an axis shift angle estimated from the phase of said induced voltage indicates that the virtual rotor position leads the actual rotor position in the rotation direction of the rotor and increasing the frequency of the motor applied voltage to increase the rotation speed of the virtual rotor position when the estimated axis shift angle indicates lagging.

A method of estimating a rotor position of a synchronous motor having saliency and controlling the synchronous motor without resort to position sensor, comprising the step of:

when estimating an induced voltage of said synchronous motor from a vector difference between a motor applied voltage and voltage drops due to resistance and inductance of a motor winding, using a predetermined value as said inductance and determining said voltage drop due to inductance as a quantity leading a motor current by a predetermined phase;
and
determining a phase of an estimated induced voltage and on the basis of the fact that the phase indicates an axis shift angle between a virtual rotor position from the control viewpoint and an unobservable actual rotor position, increasing a torque command value for the motor to increase the rotation speed of the actual rotor position when the axis shift angle estimated from the phase of said induced voltage indicates that the virtual rotor position leads the actual rotor position in the rotation direction of the rotor and decreasing the torque command value for the motor to decrease the rotation speed of the actual rotor position when the estimated axis shift angle indicates lagging.

A system of controlling a synchronous motor without resort to position sensor, comprising:

an inverter for converting a DC voltage into a three-phase AC voltage of variable voltage and variable frequency and applying the three-phase AC voltage to the synchronous motor having saliency;
a current detector for detecting a motor current;
a voltage command operating unit for preparing voltage command values by using a virtual rotor position (θdc) in order that the magnitude and phase of detected three-phase motor current follow command values of the magnitude and phase of the motor current, respectively;
a current command generating unit applied with a motor speed command value to prepare said command values of the magnitude and phase of motor current on the basis of the motor speed command value and a motor speed estimation value;
an induced voltage estimating unit for estimating an induced voltage of said motor by using the detected motor current, said voltage command value and said motor speed command value as well as resistance and inductance of motor parameters, estimating an axis shift angle (Δθ) indicative of a shift between the virtual rotor position from the control viewpoint and a real position and delivering the axis shift angle;
and
a speed phase estimating unit for determining the motor speed estimation value and the virtual rotor position (θdc) from the axis shift angle (Δθ) and delivering the motor speed estimation value and the virtual rotor position (θdc).

4 more elements

A system of controlling a synchronous motor without resort to position sensor, comprising:

an inverter for converting a DC voltage into a three-phase AC voltage of variable voltage and variable frequency and applying the three-phase AC voltage to the synchronous motor;
a current detector for detecting a motor current;
a voltage command operating unit for preparing voltage commands by using a virtual rotor position (θdc) in order that the magnitude and phase of detected three-phase motor current follow command values of the magnitude and phase of the motor current, respectively;
a current command generating unit applied with a motor speed command value to prepare said command values of the magnitude and phase of motor current on the basis of the motor speed command value and a motor speed estimation value;
an induced voltage estimating unit for estimating an induced voltage of said motor by using the detected motor current, said voltage command values and a frequency of motor applied voltage as well as resistance and inductance of motor parameters, estimating an axis shift angle (Δθ) indicative of a shift between the virtual rotor position from the control viewpoint and a real position and delivering the axis shift angle;
and
a speed phase estimating unit for computing the frequency of motor applied voltage from the axis shift angle (Δθ) to deliver the computed frequency of motor applied voltage, and determining the motor speed estimation value and the virtual rotor position (θdc) from the computed frequency of motor applied voltage to deliver the motor speed estimation value and the virtual rotor position (θdc).

4 more elements

Dependencies are inferred from the claim text.

Method of estimating a rotor position of synchronous motor, method of controlling synchronous motor with no position sensor and a controller of synchronous motor

Life of this patent

Method of estimating a rotor position of synchronous motor, method of controlling synchronous motor with no position sensor and a controller of synchronous motor

Life of this patent

Abstract

Claims24