Method and device for determining current of electric motor or generator
Provided, according to one embodiment, is a method for determining a current of an electric motor or a generator, the method comprising the steps of: acquiring characteristics of a filter for eliminating noise occurring in a process for determining a current of an electric motor or a generator; determining a time delay caused by the filter, on the basis of a change in a phase indicating the characteristics of the filter, the change resulting from a change in an operating frequency of the electric motor or the generator; and determining the current of the electric motor or the generator by compensating the time delay.
1 . A method of determining a current of an electric motor or generator, comprising:
obtaining characteristics of a filter for eliminating noise generated during determination of a current of the electric motor or the generator;
determining a time delay caused by the filter on the basis of a change in a phase indicating the characteristics of the filter versus a change in an operating frequency of the electric motor or generator, wherein a magnitude and a phase indicating the characteristics of the filter are determined by the operating frequency; and
determining a current of the electric motor or the generator based on the time delay.
2 . The method of claim 1 , wherein the filter comprises at least one of a low-pass filter, an anti-aliasing filter, or a finite impulse response (FIR) filter.
3 . The method of claim 1 , wherein the filter comprises a low-pass filter, an anti-aliasing filter, and a finite impulse response (FIR) filter, and
the time delay is determined by adding a first time delay caused by the low-pass filter, a second time delay caused by the anti-aliasing filter, and a third time delay caused by the FIR filter.
4 . The method of claim 1 , wherein the determining of the current of the electric motor or the generator comprises updating a phase of the current of the electric motor or the generator on the basis of a value obtained by multiplying the time delay by the operating frequency.
5 . The method of claim 1 , wherein the determining of the time delay comprises determining the time delay by differentiating a phase of a transfer function indicating the characteristics of the filter with respect to the operating frequency, wherein for the phase of the transfer function, the operating frequency is used as an input variable.
6 . The method of claim 5 , wherein, when the transfer function (G 2 (s)) satisfies the following Equation (1), the time delay (ρ 2 ) satisfies the following Equation (2):
G
2
(
s
)
=
ω
n
2
s
2
+
2
ζω
n
s
+
ω
n
2
;
and
(
1
)
ρ
2
=
-
2
ζω
n
(
ω
2
+
ω
n
2
)
ω
4
+
2
ω
n
2
(
2
ζ
-
1
)
ω
2
+
ω
n
4
.
(
2
)
7 . A computer-readable recording medium having recorded thereon a program for performing the method of claim 1 in a computer.
8 . A device for determining a current of an electric motor or generator, comprising:
a filter configured to eliminate noise generated during determination of a current of the electric motor or the generator; and
a processor configured to obtain characteristics of the filter, determine a time delay caused by the filter on the basis of a change in a phase indicating the characteristics of the filter versus a change in an operating frequency of the electric motor or generator, wherein a magnitude and a phase indicating the characteristics of the filter are determined by the operating frequency, and determine a current of the electric motor or the generator based on the time delay.
9 . The device of claim 8 , wherein the filter comprises at least one of a low-pass filter, an anti-aliasing filter, or a finite impulse response (FIR) filter.
10 . The device of claim 8 , wherein the filter comprises a low-pass filter, an anti-aliasing filter, and a finite impulse response (FIR) filter, and
the time delay is determined by adding a first time delay caused by the low-pass filter, a second time delay caused by the anti-aliasing filter, and a third time delay caused by the FIR filter.
11 . The device of claim 8 , wherein the processor updates a phase of the current of the electric motor or the generator on the basis of a value obtained by multiplying the time delay by the operating frequency.
12 . The device of claim 8 , wherein the processor determines the time delay by differentiating a phase of a transfer function indicating the characteristics of the filter with respect to the operating frequency,
wherein for the phase of the transfer function, the operating frequency is used as an input variable.
13 . The device of claim 12 , wherein, when the transfer function (G 2 (s)) satisfies the following Equation (1), the time delay (ρ 2 ) satisfies the following Equation (2):
G
2
(
s
)
=
ω
n
2
s
2
+
2
ζω
n
s
+
ω
n
2
;
and
(
1
)
ρ
2
=
-
2
ζω
n
(
ω
2
+
ω
n
2
)
ω
4
+
2
ω
n
2
(
2
ζ
-
1
)
ω
2
+
ω
n
4
.
(
2
)