Method for identifying the discrete instantaneous angular speed of an electromechanical system

Patent metadata

Field	Value
Publication number	US-10658961-B2
Application number	US-201815958317-A
Country	US
Kind code	B2
Filing date	Apr 20, 2018
Priority date	Oct 20, 2015
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A method for identifying the discrete instantaneous angular speed of electromechanical systems in which electrical rotating machinery is used and in which at least one electrical signal is measured during an operation of the electromechanical system. The method includes measuring analog stator current signals and analog stator voltage signals for at least one phase A, B, C, converting the measurements into a digital discrete form, transmitting the digital discrete signals to a computer device wherein data analysis is performed in a processor unit on the basis of a simplified mathematical model of the dynamics of the motor or generator. During the data analysis an average rotor time constant is calculated, an average supply frequency value is identified, an average angular speed is obtained, and an instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals is determined. The discrete instantaneous angular speed is identified by combining the average supply frequency value, the instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals, the average rotor time constant, and a number of pole pairs of the electric motor, given by the user. The result of combining the data is stored in a memory of the processor unit.

First claim

The invention claimed is:

1. A method for identifying a discrete instantaneous angular speed {dot over (θ)} d of a motor or generator of an electromechanical system, by measuring analog stator current signals I sA , I sB , I sC for at least one phase A, B, C, and analog stator voltage signals U sA , U sB , U sc signals for at least one phase A, B, C and by converting said measurements into a digital discrete form to obtain discrete stator current signals and discrete stator voltage signals, the method comprising:
transmitting said digital discrete signals to a computer device wherein data analysis is performed in a processor unit, on the basis of a simplified mathematical model of the dynamics of the motor or generator, said simplified mathematical model being based upon manipulations of a stator voltage equation for a smooth-air-gap machine and a rotor voltage equation for a smooth-air-gap machine, said manipulations involving simplifying assumptions that a complex rotor flux-linkage space phasor in the stationary reference frame changes slowly in comparison to a complex stator flux-linkage space phasor, that ohmic losses in the motor or generator are negligible and that leakage inductances of the motor or generators are low,
identifying an average supply frequency value, ω L , from one or more of the discrete stator current signals or discrete stator voltage signals,
identifying an average angular speed, {dot over (θ)} from one or more of the discrete stator current signals or discrete stator voltage signals,
identifying an instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals, Ø UI,d from one or more of the discrete stator current signals and one or more of the discrete stator voltage signals,
determining an average rotor time constant, τ r on the basis of the simplified mathematical model of the dynamics of the motor or generator using one or more of the discrete stator current signals and one or more of the discrete stator voltage signals,
identifying a discrete instantaneous angular speed {dot over (θ)} d according to the formula:

θ
.

d

=

1

p
⁢

τ
r

_

⁢

(

ω
L

⁢

τ
r

_

+

tan
⁢

(

ϕ

UI
,
d

-

π
2

)

)

where:
p is a number of pole pairs of the electric motor
w L is an average supply frequency value,
t r is an average rotor time constant
f UI,d is an instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals,
storing the result of combining said data in a memory of the processor unit.

2. The method according to claim 1 wherein the step of determining an average rotor time constant, τ r is calculated from the formula:

τ
r

_

=

tan
⁡

(

π
2

-

ϕ
UI

_

)

(

ω
_

L

-

p
⁢

⁢

θ
.

_

)

where: τ r is an average rotor time constant
p is a number of pole pairs of the electric motor
w L is an average supply frequency value,
{dot over (θ)} an average angular speed,
f UI is an arithmetic mean of the instantaneous phase difference between the discrete stator current signals and the discrete stator voltage signals.

3. The method according to claim 1 , wherein the step of determining an average rotor time constant, τ r is calculated from the formula:

τ
r

_

=

tan
⁡

(

π
2

-

cos

-
1

⁡

(

ϕ
PF

)

)

(

ω
L

_

-

p
⁢

Assignees

• Abb Schweiz Ag

Inventors

• Ottewill James

Classifications

• H02P23/14

  Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage · CPC title

• H02P21/16 Primary

  Estimation of constants, e.g. the rotor time constant · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P2207/01

  Asynchronous machines · CPC title