Aircraft engine starter/generator and controller
An aircraft starting and generating system includes a starter/generator that includes a main machine, an exciter, and a permanent magnet generator. The system also includes an inverter/converter/controller that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode for starting a prime mover of the aircraft, and that converts AC power, obtained from the starter/generator after the prime mover have been started, to DC power in a generate mode of the starter/generator. The exciter includes a stator and a rotor, and wherein the exciter rotor includes a three-phase AC winding.
1. An aircraft starting and generating system, comprising:
a starter/generator that includes a main machine having a rotor and a stator, an exciter having a rotor and a stator, and a permanent magnet generator having a rotor and a stator; and
an inverter/converter/controller that is connected to the starter/generator and that generates AC power to drive the starter/generator in a start mode and that converts AC power obtained from the starter/generator to DC power in a generate mode,
wherein the inverter/converter/controller includes rotor position measuring means for measuring an angular position of the respective rotors of the starter/generator based on current and voltage signals obtained from the starter/generator, the rotor position measuring means not including a mechanical position sensor, the rotor position measuring means includes high frequency injection estimation means for performing rotor position estimation when the respective rotors are rotating below a predetermined rotational speed, and voltage mode estimation means for performing rotor position estimation when the respective rotors are rotating equal to or above the predetermined rotational speed.
2. An aircraft starting and generating system, comprising:
a starter/generator that includes a main machine, an exciter, and a permanent magnet generator; and
a controller for controlling the starter/generator,
wherein the starter/generator is configured to operate as a starter in a start mode to start a prime mover of the aircraft, and to operate as a generator in a generate mode to generate power from the prime mover in order to provide power to other components of the aircraft after the prime mover has been started,
wherein, in the start mode, the controller performs sensorless estimation of a rotor position of the starter in which the controller includes: a) a high frequency injection estimation unit for performing sensorless estimation of the rotor position of the starter when the starter is rotating below a predetermined speed, and b) a voltage mode sensorless estimation unit for performing sensorless estimation of the rotor position of the starter/generator when the starter is rotating above or equal to the predetermined speed.
3. The aircraft starting and generating system according to claim 2 , wherein the controller comprises means for determining a phase a current and a phase b current of the starter, the determining means including a Space Vector Pulse Width Modulation (SVPWM) unit,
wherein the high frequency injection estimation unit comprises:
means for superimposing a pair of sinusoidal waveforms on inputs to the Space Vector Pulse Width Modulation (SVPWM) unit; and
means for determining a response of the phase a current and the phase b current to the pair of sinusoidal waveforms superimposed on the inputs of the SVPWM unit,
wherein rotor position information of the starter is obtained as a result thereof.
4. The aircraft starting and generating system according to claim 3 , wherein the pair of sinusoidal waveforms are orthogonal to each other and are at a same carrier frequency.
5. The aircraft starting and generating system according to claim 2 , wherein the voltage mode sensorless estimation unit comprises:
means for deriving α and β artificial flux linkages which are defined such that an α axis corresponds to a Phase a winding of a main stator of the starter/generator and a β axis corresponds to an axis that is 90 degrees ahead of the α axis; and
means for determining a rotating angle of the starter from the α and β artificial flux linkages.
6. The aircraft starting and generating system according to claim 5 , wherein the α and β artificial flux linkages are defined as λα′ and λβ′, and wherein the rotating angle θ of the starter is determined by the following equation: θ=tan −1 (λβ′/λα′).
7. The aircraft starting and generating system according to claim 2 , wherein the main machine includes an inverter, the system further comprising:
an auto-field weakening unit that includes an auto-field weakening loop, the auto-field weakening unit being configured to measure line-to-line voltages obtained from the inverter, to apply a transformation to the line-to-line voltages, to perform a vector summation of outputs of the transformation, and to feed back the vector summation as a feedback signal to the auto-field weakening loop,
wherein the auto-field weakening loop is provided to the inverter in order to keep the inverter from saturating during the start mode.
8. The aircraft starting and generating system according to claim 7 , further comprising:
a near unity power factor control unit configured to apply a predetermined current profile for the main machine so as to cause the main machine to operate in a near unity power factor region.
9. The aircraft starting and generating system according to claim 8 , wherein the predetermined current profile is a d-axis current profile that controls a magnetic field in an air gap between a rotor of the machine and a stator of the main machine.