# US 9,438,145 B2 · Magnet temperature estimating system for synchronous electric motor

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- Number: US 9,438,145 B2
- Document ID: US9438145B2
- Status: Granted
- Kind: B2
- Application number: 14/450,866
- Filed: 2014-08-04
- Published: 2015-07-16
- Granted: 2016-09-06
- Earliest claimed: 2014-01-13
- Assignees: Nissan Motor Co., Ltd.
- Applicants: Nissan Motor Co., Ltd.
- Inventors: David Díaz Reigosa; Fernando Briz Del Blanco; Hideo Yoshida; Takashi Kato
- Web page: https://patentgrep.com/patent/US9438145B2

## CPC

- H02P 6/34: Modelling or simulation for control purposes
- H02P 23/14: Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
- H02P 29/662: {the rotor having permanent magnets (H02P29/67 takes precedence)}
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A magnet temperature estimating system for a synchronous electric motor having a permanent magnet includes: a superimposing unit configured to superimpose a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor; a calculator configured to calculate an impedance of the synchronous electric motor from the superimposed voltage or current and a current or voltage obtained by the superimposing; and a magnet temperature estimating unit configured to estimate a temperature of the permanent magnet on the basis of the calculated impedance.

## Claims

### Claim 1

A magnet temperature estimating system for a synchronous electric motor having a permanent magnet comprising:
a superimposing unit configured to superimpose a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor;
a calculator configured to calculate an impedance of the synchronous electric motor from the superimposed voltage or current and a current or voltage obtained by the superimposing; and
a magnet temperature estimating unit configured to estimate a temperature of the permanent magnet on the basis of the calculated impedance.

### Claim 2 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, wherein
the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave only on the d-axis of the synchronous electric motor.

### Claim 3 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, wherein
the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave at predetermined intervals.

### Claim 4 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, wherein
the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the calculated impedance and a pre-obtained relationship between the impedance and the temperature of the permanent magnet.

### Claim 5 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, further comprising:
a temperature measuring unit configured to measure a temperature of a stator coil of the synchronous electric motor, wherein
when the superimposing unit superimposes the voltage or current of the frequency different from the frequency of the fundamental wave on the synchronous electric motor, the calculator corrects a resistance value of the stator coil included in the impedance depending on the temperature of the stator coil measured by the temperature measuring unit and the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the impedance including the corrected resistance value of the stator coil.

### Claim 6 (depends on 5)

The magnet temperature estimating system for the synchronous electric motor according to claim 5, wherein
the calculator corrects the resistance value of the stator coil included in the impedance on the basis of the temperature of the stator coil measured by the temperature measuring unit and a pre-obtained relationship between the temperature of the stator coil and the resistance value of the stator coil, and the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the impedance including the corrected resistance value of the stator coil.

### Claim 7 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, wherein
the synchronous electric motor is driven by a current inverter,
the superimposing unit superimposes a current expressed by a formula (1) shown below on the synchronous electric motor,
the calculator uses a voltage which is obtained by superimposing the current expressed by the formula (1) shown below on the synchronous electric motor and which is expressed by a formula (2) shown below, to calculate the impedance expressed by a formula (3) shown below and obtained from the following formulae (1) and (2), wherein
[
i
dsc
*
i
qsc
*
]
=
[
I
c
⁢
sin
⁢
⁢
ω
c
⁢
t
0
]
(
1
)
where
idsc* represents a d-axis harmonic current command value;
iqsc* represents a q-axis harmonic current command value;
Ic represents an amplitude of d-axis harmonic current command value;
ωc represents an angular frequency of d-axis harmonic current command value; and
t represents a time,
[
v
dsc
v
qsc
]
=
[
(
R
d
+
j
⁢
⁢
ω
c
⁢
L
d
)
⁢
i
dsc
*
0
]
(
2
)
where
vdsc represents a d-axis harmonic voltage value;
vqsc represents a q-axis harmonic voltage value;
Rd represents a circuit resistance value including coil resistance value and magnet resistance value;
Ld represents a d-axis inductance; and
ωc represents an angular frequency of d-axis harmonic current command value,
Z
ds
=
⁢
(
R
d
+
j
⁢
⁢
ω
c
⁢
L
d
)
=
⁢

v
dsc

2
⁢
ⅇ
j
⁡
(
ω
c
⁢
t
+
φ
2
⁢
⁢
d
)
I
c
2
⁢
ⅇ
j
⁡
(
ω
c
⁢
t
)
=
⁢

v
dsc

2
⁢
ⅇ
j
⁡
(
-
ω
c
⁢
t
+
φ
2
⁢
⁢
d
)
I
c
2
⁢
ⅇ
j
⁡
(
-
ω
c
⁢
t
)
(
3
)
where
Zds represents impedance;
Rd represents the circuit resistance value including coil resistance value and magnet resistance value;
Ld represents the d-axis inductance;
ωc represents the angular frequency of d-axis harmonic current command value;
vdsc represents the d-axis harmonic voltage value;
φzd represents a phase angle of impedance;
Ic represents the amplitude of d-axis harmonic current command value; and
t represents the time.

### Claim 8 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, wherein
the synchronous electric motor is driven by a voltage inverter,
the superimposing unit superimposes a voltage expressed by a formula (4) shown below on the synchronous electric motor,
the calculator uses a current which is obtained by superimposing the voltage expressed by the formula (4) shown below on the synchronous electric motor and which is expressed by a formula (5) shown below, to calculate the impedance expressed by a formula (6) shown below and obtained from the following formulae (4) and (5), wherein
vdsc*=Vc cos ωct (4)
where
vdsc* represents a d-axis harmonic voltage command value;
Vc represents an amplitude of d-axis harmonic voltage command value;
ωc represents an angular frequency of d-axis harmonic voltage command value; and
t represents a time,
[
i
dsc
i
qsc
]
=
[
v
dsc
*
/
(
R
d
+
j
⁢
⁢
ω
c
⁢
L
d
)
0
]
(
5
)
where
idsc represents a d-axis harmonic current value;
iqsc represents a q-axis harmonic current value;
vdsc* represents the d-axis harmonic voltage command value;
Rd represents a circuit resistance value including coil resistance value and magnet resistance value;
Ld represents a d-axis inductance; and
ωc represents an angular frequency of d-axis harmonic voltage command value,
Z
ds
=
⁢
(
R
d
+
j
⁢
⁢
ω
c
⁢
L
d
)
=
⁢
V
c
2
⁢
ⅇ
j
⁡
(
-
ω
c
⁢
t
)

i
dsc

2
⁢
ⅇ
j
⁡
(
ω
c
⁢
t
-
φ
2
⁢
⁢
d
)
=
⁢
V
c
2
⁢
ⅇ
j
⁡
(
ω
c
⁢
t
)

i
dsc

2
⁢
ⅇ
j
⁡
(
-
ω
c
⁢
t
+
φ
2
⁢
⁢
d
)
(
6
)
where
Zds represents impedance;
Rd represents the circuit resistance value including coil resistance value and magnet resistance value;
Ld represents the d-axis inductance;
ωc represents the angular frequency of d-axis harmonic voltage command value;
Vc represents the amplitude of d-axis harmonic voltage command value;
φzd represents a phase angle of impedance;
idsc represents the d-axis harmonic current value; and
t represents the time.

### Claim 9 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, further comprising:
a band-pass filter and a band-stop filter which separate the fundamental wave and the voltage or current of the frequency different from the frequency of the fundamental wave from each other, wherein
the calculator calculates the impedance on the basis of the separated voltage or current.

### Claim 10 (depends on 9)

The magnet temperature estimating system for the synchronous electric motor according to claim 9, further comprising:
a second band-stop filter configured to extract a frequency component on a different side from a rotating direction of the synchronous electric motor, from the separated voltage or current, wherein
the calculator calculates the impedance on the basis of the extracted voltage or current.

### Claim 11 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, further comprising:
a compensation calculator configured to compensate the calculated impedance, wherein
the magnet temperature estimating unit estimates the temperature of the permanent magnet on the basis of the compensated impedance.

### Claim 12 (depends on 11)

The magnet temperature estimating system for the synchronous electric motor according to claim 11, wherein
the compensation calculator compensates the calculated impedance by using at least one of a pre-obtained relationship between a d-axis fundamental wave current and a compensation amount for compensating the calculated impedance and a pre-obtained relationship between a q-axis fundamental wave current and a compensation amount for compensating the calculated impedance.

### Claim 13 (depends on 1)

The magnet temperature estimating system for the synchronous electric motor according to claim 1, further comprising:
a magnetization amount estimating unit configured to estimate a magnetization amount of the permanent magnet on the basis of the calculated impedance and a pre-obtained relationship between the impedance and the magnetization amount of the permanent magnet.

### Claim 14

A magnet temperature estimating system for a synchronous electric motor having a permanent magnet comprising:
superimposing means for superimposing a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor;
calculating means for calculating an impedance of the synchronous electric motor from the superimposed voltage or current and a current or voltage obtained by the superimposing; and
magnet temperature estimating means for estimating a temperature of the permanent magnet on the basis of the calculated impedance.