Method and device for ascertaining the rotor temperature of a permanent-magnet synchronous machine
A method for ascertaining the rotor temperature of a permanent-magnet synchronous machine ( 10 ), in which a first estimate (T R1 ) for the rotor temperature is ascertained as a function of a remanent flux density of permanent magnets contained in a rotor of the synchronous machine ( 10 ). A second estimate (T R2 ) for the rotor temperature is ascertained via a Kalman filter containing a thermal model of the synchronous machine ( 10 ), the first estimate (T R1 ) for the rotor temperature being supplied at least intermittently to the Kalman filter.
1. A method for ascertaining the rotor temperature of a permanent-magnet synchronous machine comprising: determining a first estimate (T R1 ) for the rotor temperature as a function of a remanent flux density of permanent magnets contained in a rotor of the synchronous machine, and determining a second estimate (T R2 ) of the rotor temperature by using a Kalman filter containing a thermal model of the synchronous machine, the first estimate (T R1 ) for the rotor temperature being supplied to the Kalman filter at least intermittently;
wherein the first estimate (T R1 ) for the rotor temperature and a measured value (T S ) for stator temperature are both supplied to the Kalman filter for a correction step; and
wherein a steady-state model of the synchronous machine is used for determining the first estimate (T R1 ), for the rotor temperature according to:
U d =R·I d −L q ·I q ·ω
U q =R·I q +L d −I d ·ω+K m ·ω
where U d , U q denote the voltage of synchronous machine in the d direction and q direction, respectively, I d , I q denote the current of the synchronous machine in the d direction and q direction, respectively, and L d , L q denote the corresponding inductances, where R is a strand resistance, ω is the electrical angular velocity and K m is a temperature-dependent fundamental-wave amplitude of the field-linked direct-axis flux.
2. A method for ascertaining the rotor temperature of a permanent-magnet synchronous machine comprising: determining a first estimate (T R1 ) for the rotor temperature as a function of a remanent flux density of permanent magnets contained in a rotor of the synchronous machine, and determining a second estimate (T R2 ) of the rotor temperature by using a Kalman filter containing a thermal model of the synchronous machine, the first estimate (T R1 ) for the rotor temperature being supplied to the Kalman filter at least intermittently;
wherein either only the first estimate (T R1 ) for the rotor temperature or a measured value (T S ) for stator temperature is supplied to the Kalman filter for a correction step; and
wherein a steady-state model of the synchronous machine is used for determining the first estimate (T R1 ), for the rotor temperature according to:
U d =R·I d −L q ·I q ·ω
U q =R·I q +L d −I d ·ω+K m ·ω
where U d , U q denote the voltage of the synchronous machine in the d direction and q direction, respectively, I d , I q denote the current of the synchronous machine in the d direction and q direction, respectively, and L d , L q denote the corresponding inductances, where R is a strand resistance, ω is the electrical angular velocity and K m is a temperature-dependent fundamental-wave amplitude of the field-linked direct-axis flux.
3. The method as recited in claim 1 , wherein the thermal model of the synchronous machine includes at least stator, rotor and cooling water components, and heat transfers among all components is taken into account.
4. The method as recited in claim 1 , wherein the thermal model of the synchronous machine includes at least stator, rotor and cooling water components, and heat transfers among all components is taken into account.
5. The method as recited in claim 2 , wherein the thermal model of the synchronous machine includes at least stator, rotor and cooling water components, and heat transfers among all components is taken into account.
6. The method as recited in claim 1 , wherein the thermal model uses thermal conductance values between its or the components as a function of a rotational speed of the synchronous machine.
7. The method as recited in claim 1 , wherein the thermal model takes into account heat losses of a stator and a rotor of the synchronous machine, and a dependence of the heat losses on the rotor temperature are disregarded.
8. The method as recited in claim 1 , wherein the thermal model takes into account heat losses of a stator and a rotor of the synchronous machine, and a dependence of the heat losses on the rotor temperature are disregarded.
9. The method as recited in claim 2 , wherein the thermal model takes into account heat losses of a stator and a rotor of the synchronous machine, and a dependence of the heat losses on the rotor temperature are disregarded.
10. The method as recited in claim 3 , wherein the thermal model takes into account heat losses of a stator and a rotor of the synchronous machine, and a dependence of the heat losses on the rotor temperature are disregarded.
11. The method as recited in claim 1 , wherein for determining the first estimate (T R1 ) for the rotor temperature, the synchronous machine is operated temporarily at an operating point at which no saturation prevails.
12. The method as recited in claim 1 , wherein inductances L d , L q and the fundamental-wave amplitude of field-linked direct-axis flux K m are each ascertained as a function of currents I d , I q , using characteristics maps.
13. The method as recited in claim 11 , wherein inductances L d , L q and the fundamental-wave amplitude of field-linked direct-axis flux Km are each ascertained as a function of currents I d , I q , using characteristics maps.
14. The method as recited in claim 1 , wherein the first estimate (T R1 ) for the rotor temperature is obtained according to the equation:
T
R
1
=
T
R
0
+
K
m
(
T
R
1
)
-
K
m
α
·
K
m
0
where α is the temperature coefficient of the remanent flux density, K m0 is a reference value of the remanent flux density at reference temperature T R0 , and:
K
m
(
T
R
1
)
=
U
q
-
R
·
I
q
ω
-
L
d
(
I
d
)
·
I
d
.
15. The method as recited in claim 11 , wherein the first estimate (T R1 ) for the rotor temperature is obtained according to the equation:
T
R
1
=
T
R
0
+
K
m
(
T
R
1
)
-
K
m
0
α
·
K
m
0
where α is the temperature coefficient of the remanent flux density, K m0 is a reference value of the remanent flux density at reference temperature T R0 , and:
K
m
(
T
R
1
)
=
U
q
-
R
·
I
q
ω
-
L
d
(
I
d
)
·
I
d
.
16. A device for determining the rotor temperature of a permanent-magnet synchronous machine, the device being capable of determining a first estimate (T R1 ) for the rotor temperature as a function of a remanent flux density of permanent magnets contained in a rotor of the synchronous machine, and the device being capable of determining a second estimate (T R2 ) for the rotor temperature via a Kalman filter containing a thermal model of the synchronous machine, the first estimate (T R1 ) for the rotor temperature being supplied at least intermittently to the Kalman filter; and
wherein the first estimate (T R1 ) for the rotor temperature and a measured value (T S ) for stator temperature are both supplied to the Kalman filter for a correction step;
wherein a steady-state model of the synchronous machine is used for determining the first estimate (T R1 ), for the rotor temperature according to:
U d =R·I d −L q ·I q ·ω
U q =R·I q +L d −I d ·ω+K m ·ω
where U d , U q denote the voltage of the synchronous machine in the d direction and q direction, respectively, I d , I q denote the current of the synchronous machine in the d direction and q direction, respectively, and L d , L q denote the corresponding inductances, where R is a strand resistance, ω is the electrical angular velocity and K m is a temperature-dependent fundamental-wave amplitude of the field-linked direct-axis flux.
17. A device for determining the rotor temperature of a permanent-magnet synchronous machine, the device being capable of determining a first estimate (T R1 ) for the rotor temperature as a function of a remanent flux density of permanent magnets contained in a rotor of the synchronous machine, and the device being capable of determining a second estimate (T R2 ) for the rotor temperature via a Kalman filter containing a thermal model of the synchronous machine, the first estimate (T R1 ) for the rotor temperature being supplied at least intermittently to the Kalman filter, wherein either only the first estimate (T R1 ) for the rotor temperature or a measured value (T S ) for stator temperature is supplied to the Kalman filter for a correction step;
wherein a steady-state model of the synchronous machine is used for determining the first estimate (T R1 ), for the rotor temperature according to:
U d =R·I d −L q ·I q ·ω
U q =R·I q +L d −I d ·ω+K m ·ω
where U d , U q denote the voltage of the synchronous machine in the d direction and q direction, respectively, I d , I q denote the current of the synchronous machine in the d direction and q direction, respectively, and L d , L q denote the corresponding inductances, where R is a strand resistance, ω is the electrical angular velocity and K m is a temperature-dependent fundamental-wave amplitude of the field-linked direct-axis flux.