Methods and apparatus for generating current commands for an interior permanent magnet (IPM) motor
View Patent ↗In one aspect, an apparatus includes a motor and inverter configured to provide input power to the motor and a data store comprising at least one entry including a first torque command, a first motor speed, and a first DC voltage value. The first torque command and the first motor speed and the first DC voltage value are associated with a first current output. The apparatus includes a processor configured to receive a torque input, a DC voltage input, and a motor speed input and determine an output current associated with the torque input, the DC voltage input, and the motor speed input, correct the output current to be within a voltage constraint of the motor when the DC voltage input is than a reference voltage at the motor and output the corrected output current to cause the inverter to provide the input power to the motor.
1. An apparatus comprising:
a motor;
an inverter configured to provide input power to the motor;
a DC power bus configured to provide input power to the inverter;
a data store comprising information defining inverter currents for producing different motor torque outputs at different motor speeds and different DC power bus voltages; and
a processor configured to:
receive a torque command, a DC power bus voltage measurement, and a motor speed measurement;
determine, using the data store, an inverter current command based at least in part on the torque command, the DC power bus voltage measurement, and the motor speed measurement;
modify the inverter current command, wherein modifying the inverter current command comprises:
identifying a torque curve defined by the torque command;
identifying a slope of a line running through a first point on the torque curve corresponding to the inverter current command and a second point on the torque curve corresponding to a second inverter current command; and
modifying the inverter current command to be different from the inverter current command and the second inverter current command based on the identified slope within voltage constraints of the motor; and
control the inverter based at least in part on the modified inverter current command.
2. The apparatus of claim 1 , wherein modifying the inverter current command comprises increasing a first component of the inverter current command and decreasing a second component of the inverter current command.
3. The apparatus of claim I, wherein modifying the inverter current command comprises increasing both a first and a second component of the inverter current command.
4. The apparatus of claim 1 , wherein the processor is further configured to determine a total current delta for which the inverter current command is to be modified to be within the voltage constraint of the motor.
5. The apparatus of claim 1 , wherein the processor is further configured to determine, using the data store, a second inverter current command based at least in part on the torque command, a DC power bus value greater than the DC power bus voltage measurement, and the motor speed measurement.
6. The apparatus of claim 5 , wherein the modifying is based at least in part on the inverter current command to be modified and the second inverter current command.
7. The apparatus of claim 1 , wherein modifying the inverter current command comprises adjusting a first component of the inverter current command according to
I
d
=
1
1
+
k
I
s
and a second component of the inverter current command according to
I
q
=
k
1
+
k
I
s
,
wherein ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, and k is the slope.
8. The apparatus of claim 1 , wherein modifying the inverter current command comprises adjusting a first component of the inverter current command according to
I
d
=
k
sin
β
+
k
cos
β
I
s
and a second component of the inverter current command according to
I
q
=
k
sin
β
+
k
cos
β
I
s
,
wherein ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, k is the slope, and β is an angle based on the inverter current command.
9. A method comprising:
receiving a torque command, a DC power bus voltage measurement, and a motor speed measurement;
determining, using a data store, an inverter current command based at least in part on the torque command, the DC power bus voltage measurement, and the motor speed measurement, wherein the data store comprises information defining inverter currents for producing different motor torque outputs at different motor speeds and different DC power bus voltages;
modifying the inverter current command in accordance with a voltage constraint of the motor, wherein modifying the inverter current command comprises:
identifying a torque curve defined by the torque command;
identifying a slope of a line running through a first point on the torque curve corresponding to the inverter current command and a second point on the torque curve corresponding to a second inverter current command, and
modifying the inverter current command to be different from the inverter current command and the second inverter current command based on the identified slope; and
controlling an inverter based at least in part on the determined inverter current command.
10. The method of claim 9 , wherein modifying the inverter current command comprises increasing a first component of the inverter current command and decreasing a second component of the inverter current command.
11. The method of claim 9 , wherein modifying the inverter current command comprises increasing both a first and a second component of the inverter current command.
12. The method of claim 9 , further comprising determining a total current delta for which the inverter current command is to be modified to be within the voltage constraint of the motor.
13. The method of claim 9 , further comprising determining, using the data store, a second inverter current command based at least in part on the torque command, a DC power bus value greater than the DC power bus voltage measurement, and the motor speed measurement.
14. The method of claim 13 , wherein modifying the inverter current command is based at least in part on the inverter current command to be modified and the second inverter current command.
15. The method of claim 9 , wherein modifying the inverter current command comprises adjusting a first component of the inverter current command according to
I
d
=
1
1
+
k
I
s
and a second component of the inverter current command according to
I
q
=
k
1
+
k
I
s
,
wherein ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, and k is the slope.
16. The method of claim 9 , wherein modifying the inverter current command comprises adjusting a first component of the inverter current command according to
I
d
=
k
sin
β
+
k
cos
β
I
s
and a second component of the inverter current command according to
I
q
=
k
sin
β
+
k
cos
β
I
s
,
wherein, ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, k is the slope, and β is an angle based on the inverter current command.
17. An apparatus, comprising:
means for driving;
means for providing input power to the driving means;
means for receiving a torque command, a DC power bus voltage measurement, and a motor speed measurement;
means for determining an inverter current command, based at least in part on the torque command, the DC power bus voltage measurement, and the motor speed measurement, from information defining inverter currents for producing different motor torque outputs at different motor speeds and different DC power bus voltages;
means for modifying the inverter current command in accordance with a voltage constraint of the motor, wherein the means for modifying the inverter current command comprises:
means for identifying a torque curve defined by the torque command;
means for identifying a slope of a line running through a first point on the torque curve corresponding to the inverter current command and a second point on the torque curve corresponding to a second inverter current command, and
means for modifying the inverter current command to be different from the inverter current command and the second inverter current command based on the identified slope; and
means for controlling an inverter based at least in part on the determined inverter current command.
18. The apparatus of claim 17 , wherein the modifying means is configured to increase a first component of the inverter current command and decrease a second component of the inverter current command.
19. The apparatus of claim 17 , wherein the modifying means is configured to increase both a first and a second component of the inverter current command.
20. The apparatus of claim 17 , further comprising means for determining a total current delta for which the inverter current command is to be modified to be within the voltage constraint of the driving means.
21. The apparatus of claim 17 , further comprising means for determining a second inverter current command, based at least in part on the torque command, a DC power bus value greater than the DC power bus voltage measurement, and the motor speed measurement, from the information defining inverter currents.
22. The apparatus of claim 21 , wherein the modifying means modifies the inverter current command based at least in part on the inverter current command to be modified and the second inverter current command.
23. The apparatus of claim 17 , wherein the modifying means comprises means for adjusting a first component of the inverter current command according to
I
d
=
1
1
+
k
I
s
and a second component of the inverter current command according to
I
q
=
k
1
+
k
I
s
,
wherein ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, and k is the slope.
24. The apparatus of claim 17 , wherein the modifying means comprises means for adjusting a first component of the inverter current command according to
I
d
=
k
sin
β
+
k
cos
β
I
s
and a second component of the inverter current command according to
I
q
=
k
sin
β
+
k
cos
β
I
s
,
wherein ΔI s is a phase current delta, ΔI d is a change in a first stator current, ΔI q is a change in a second stator current, k is the slope, and β is an angle based on the inverter current command.