Rotor temperature estimation and motor control torque limiting for vector-controlled AC induction motors
View Patent ↗A system and method including a runtime thermal model that estimates individual component temperatures, permitting the system to only limit power when necessary or desirable. A power-limiting system for a vector-controlled AC induction motor includes a torque command system for generating a torque command; a thermal protection system determining a runtime estimate for a temperature of a component of a rotational electro-magnetic component of the vector-controlled AC induction motor; and a controller configured to generate a motor control signal for the vector-controlled AC induction motor responsive to the torque command, wherein the thermal protection system determines the runtime estimate responsive to a multi-node thermal model of the vector-controlled AC induction motor, and wherein the controller limits a power of the vector-controlled AC induction motor to maintain a component temperature below its critical temperature.
1. An electric vehicle, comprising:
an AC induction motor for propelling the electric vehicle responsive to a motor control signal wherein said AC induction motor includes a stationary electro-magnetic component having an aperture including an axis and a rotational electro-magnetic component disposed within said aperture and co-axial with said axis to generate a propulsion torque; and
a controller having a control algorithm for controlling said AC induction motor in response to a torque command signal, wherein said controller is configured to selectively limit a power of said AC induction motor responsive to a runtime estimated temperature of a component of said rotational electro-magnetic component during operation of said AC induction motor;
wherein said control algorithm includes a thermal model that includes a pre-runtime characterization of one or more thermal properties of said rotational electro-magnetic component, a runtime direct measurement of a temperature of a component of said stationary electro-magnetic component, and a runtime direct measurement of a current in said stationary electro-magnetic component.
2. The electric vehicle of claim 1 wherein said runtime estimated temperature is responsive to said thermal model including an estimated power dissipation in said component of said rotational electro-magnetic component determined from a calculated current in said component of said rotational electro-magnetic component and a calculated electric resistance of said component of said rotational electro-magnetic component.
3. The electric vehicle of claim 2 wherein said calculated current is a function of said current in said stationary electro-magnetic component and wherein said calculated rotational electro-magnetic component electric resistance is responsive to one or more material properties of said component of said rotational electro-magnetic component and to said runtime estimated temperature.
4. A power-limiting system for a vector-controlled AC induction motor, comprising:
a torque command system for generating a torque command;
a thermal protection system determining a runtime estimate for a temperature of a component of a rotational electro-magnetic component of the vector-controlled AC induction motor; and
a controller configured to generate a motor control signal for the vector-controlled AC induction motor responsive to said torque command, wherein
said thermal protection system determines said runtime estimate responsive to a multi-node thermal model of the vector-controlled AC induction motor that includes a runtime direct measurement of a temperature of a component of a stationary electro-magnetic component of the vector-controlled AC induction motor, and a runtime direct measurement of a current used by said stationary electro-magnetic component, and wherein said controller limits a power of the vector-controlled AC induction motor to maintain said temperature below a critical temperature.
5. The system of claim 4 wherein said multi-node thermal model further includes a pre-runtime characterization of heat rejection from one or more components of said rotational electro-magnetic component.
6. The system of claim 4 wherein said runtime estimate is a function of said multi-node thermal model including an estimated power dissipation in said component of said rotational electro-magnetic component determined from a calculated current in said component of said rotational electro-magnetic component and a calculated electrical resistance of said component of said rotational electro-magnetic component.
7. The system of claim 6 wherein said calculated current is a function of said current in said stationary electro-magnetic component and wherein said calculated rotational electro-magnetic component electric resistance is responsive to one or more material properties of said component of said rotational electro-magnetic component and to said runtime estimate.
8. A method for operating an electric vehicle, the method comprising the steps of:
a) propelling the electric vehicle using a vector-controlled AC induction motor responsive to a motor control signal wherein said vector-controlled AC induction motor includes a stationary electro-magnetic component and a cooperating rotational electro-magnetic component rotating within said stationary electro-magnetic component to generate a propulsion torque; and
b) controlling said vector-controlled AC induction motor using a controller having a control algorithm responsive to a torque command signal, wherein said controller is configured to selectively limit a power of said vector-controlled AC induction motor responsive to a runtime estimated temperature of a component of said rotational electro-magnetic component during operation of said vector-controlled AC induction motor, the runtime estimated temperature based on a runtime direct measurement of a temperature of a component of said stationary electro-magnetic component, and a runtime direct measurement of a current in said stationary electro-magnetic component.
9. The method of claim 8 wherein said control algorithm includes a thermal model that includes a pre-runtime characterization of one or more thermal properties of said rotational electro-magnetic component.
10. The method of claim 9 wherein said runtime estimated temperature is a function of said thermal model including an estimated power dissipation in said component of said rotational electro-magnetic component determined from a calculated current in said component of said rotational electro-magnetic component and a calculated electric resistance of said component of said rotational electro-magnetic component.
11. The method of claim 10 wherein said calculated current is a function of said current in said stationary electro-magnetic component and wherein said calculated rotational electro-magnetic component electrical resistance is responsive to one or more material properties of said component of said rotational electro-magnetic component and to said runtime estimated temperature.