Optimized control for synchronous motors
Representative implementations of devices and techniques provide optimized control of a three-phase AC motor. A field oriented control (FOC) arrangement uses optimization components and techniques to improve power efficiency of the motor, with fast control response over a full range of motor speeds.
1. A field oriented control (FOC) structure arranged to provide variable speed control for an electric motor, comprising:
a modulator arranged to receive a vector quantity representing a desired rotational position and/or desired speed of a rotor of the motor, and to output a plurality of control signals to adjust a rotational position and/or speed of the motor, based on the vector quantity, the vector quantity comprising a magnitude and an angle of a complex voltage space vector, the angle arranged to change at a constant user-defined speed;
a switch arranged to switch the FOC structure between open loop operation and closed loop operation; and
one or more feedback loops arranged to adjust the magnitude of the complex voltage space vector based on processing one or more motor winding current values.
2. The FOC structure of claim 1 , further comprising a pulse-width modulation (PWM) unit arranged to receive the plurality of control signals and to output a PWM signal to adjust the rotational position and/or speed of the motor, based on the vector quantity.
3. The FOC structure of claim 1 , further comprising a voltage source inverter component arranged to receive a PWM signal and to output three-phase sinusoidal waveforms to windings of the motor, to adjust the rotational position and/or speed of the motor, based on the vector quantity.
4. The FOC structure of claim 1 , further comprising a Clarke Transform module arranged to transform two-phase or three-phase motor winding current value coordinates into a stationary two-phase reference frame.
5. The FOC structure of claim 1 , further comprising a Cartesian to polar transform module arranged to transform a set of two-phase stationary coordinates into the angle and a magnitude of the polar coordinate current space vector.
6. The FOC structure of claim 1 , further comprising a hysteresis controller arranged to determine a voltage per frequency value for startup of the motor while the FOC structure is in an open-loop operation and to determine the magnitude of the complex voltage space vector while the FOC structure is in the closed-loop operation for steady state.
7. The FOC structure of claim 1 , further comprising a hysteresis controller arranged to force a stator flux of the motor to be perpendicular to a rotor flux of the motor.
8. The FOC structure of claim 1 , wherein the magnitude of the complex voltage space vector changes when the FOC structure is switched between open loop operation and closed loop operation.
9. The FOC structure of claim 1 , wherein the angle of the complex voltage space vector comprises an integral of an input rotational speed of the FOC structure.
10. The FOC structure of claim 1 , wherein the FOC structure determines the angle of the complex voltage space vector based on the user-defined speed and without a rotor position sensor or a rotor position estimator.
11. A variable speed control arrangement for an electric motor, comprising;
a modulator component arranged to receive a vector quantity representing a desired rotational position and/or desired speed of a rotor of the motor, and to output a plurality of control signals to adjust a rotational position and/or speed of the motor, based on the vector quantity, the vector quantity comprising a magnitude and an angle of a complex voltage space vector, the angle arranged to change at a constant user-defined speed;
a pulse-width modulation (PWM) unit arranged to receive the plurality of control signals and to output a PWM signal based on the plurality of control signals;
a voltage source inverter component arranged to receive the PWM signal and to output sinusoidal waveforms to windings of the motor, to adjust the rotational position and/or speed of the motor, based on the PWM signal;
a switch arranged to switch the variable speed control arrangement between open loop operation and closed loop operation; and
a feedback loop including a hysteresis controller and a proportional-integral (PI) controller, arranged to adjust the magnitude of the complex voltage space vector based on processing one or more motor winding current values and based on whether the variable speed control arrangement is in open-loop operation or closed loop operation.
12. The variable speed control arrangement of claim 11 , further comprising a computing device arranged to calculate one or more transformations, including a transformation of Cartesian stationary coordinates based on one or more motor winding current values to a current space vector quantity.
13. The variable speed control arrangement of claim 11 , wherein the variable speed control arrangement operates at open loop operation during startup and switches to closed loop operation when the motor reaches a user-defined motor speed.
14. A method, comprising:
receiving, at a modulator, a vector quantity representing a desired rotational position and/or desired speed of a rotor of an electric motor, the vector quantity comprising a magnitude and an angle, the angle arranged to change at a constant user-defined speed;
outputting, at the modulator, a plurality of control signals to adjust a rotational position and/or speed of the motor based on the vector quantity;
switching from an open-loop operating mode to a closed-loop operating mode when the motor reaches a user-defined rotational speed;
adjusting, via a feedback loop, the magnitude of the vector quantity based on processing one or more motor winding current values; and
providing variable speed control to the motor based on the receiving and the adjusting.
15. The method of claim 14 , further comprising determining the angle of the complex voltage space vector by integrating an input rotational speed, without the use of a position estimator or a position sensor.
16. The method of claim 14 , further comprising determining a voltage per frequency value for startup of the motor while operating in the open-loop operating mode and determining the magnitude of the complex voltage space vector while operating in the closed-loop operating mode for steady state.
17. The method of claim 14 , further comprising forcing a stator flux of the motor to be perpendicular to a rotor flux of the motor via a hysteresis controller, while operating in the closed-loop operating mode.
18. The method of claim 14 , further comprising changing the magnitude of the complex voltage space vector when switching between open loop operation and closed loop operation.
19. The method of claim 14 , further comprising receiving the plurality of control signals at a pulse-width modulation (PWM) unit, and outputting a PWM signal at the PWM unit to adjust the rotational position and/or speed of the motor.
20. The method of claim 14 , further comprising receiving a PWM signal at a voltage source inverter component, and outputting three-phase sinusoidal waveforms to windings of the motor to adjust the rotational position and/or speed of the motor.
21. The method of claim 14 , further comprising transforming motor winding current value coordinates to a stationary two-phase reference frame at a Clarke Transform module.
22. The method of claim 14 , further comprising starting the motor in the open-loop operating mode using a voltage per frequency control, ramping up the motor speed to a user-defined speed, and switching to the closed-loop operating mode for steady-state operation of the motor.
23. The method of claim 22 , further comprising tracking the maximum energy efficiency of the motor after reaching the user-defined speed, including changing the angle of the vector quantity at a constant speed and concurrently controlling the magnitude of the vector quantity to force a stator flux of the motor to be perpendicular to a rotor flux of the motor, and transitioning to the closed-loop operating mode for steady-state operation of the motor.