Abstract
This paper proposes an integrated method of three-phase ac excitation and high-frequency voltage signal injection (HFVSI) for sensorless controlled starting of brushless synchronous machines (BSM) used as starter/generator in variable frequency ac power systems of civil aircraft. Fixed 400 Hz of the three-phase ac power is adopted both for the ac excitation and HFVSI in the initial starting process to eliminate the bulky rotor position sensor for BSM. The resulting 6th sequence harmonic voltage determined by the rotating rectifier is utilized as the HFVSI into the field-winding of main generator without any extra high-frequency signal injection. The rotor position is estimated by the high-frequency response signals extracted from the armature windings of main generator. Due to the nonlinear rotating rectifier linked in the HFSI chain, a novel frequency-insensitive asynchronous demodulation strategy is proposed in this paper for rotor position estimation. Furthermore, the initial rotor position detection is calibrated by polarity decision of the induced currents of the armature windings within the establishment procedure of field current of the main generator at standstill. The effectiveness of the ac excitation and feasibility of rotor position estimation for sensorless starting control of BSM are validated by the simulation and experimental results.
Highlights
Due to the mature structure, high reliability and low maintenance, the brushless synchronous machine(BSM) is still the most attractive candidate generator topology for both fixed-frequency and variable-frequency AC power generation for civil aircraft
The 2kW wound induction machine with the three-phase excitation windings in the stator and rotor is utilized to act as the main exciter of brushless synchronous machines (BSM), while the electrically excited synchronous motor is used as the main generator and the encoder is installed for the comparison of the estimated rotor position
The three-phase input ports of rectifier are connected to the rotor windings of the main exciter, and output ports are linked to the field windings of the main generator
Summary
Due to the mature structure, high reliability and low maintenance, the brushless synchronous machine(BSM) is still the most attractive candidate generator topology for both fixed-frequency and variable-frequency AC power generation for civil aircraft. Literature [10] and [11] proposed an extended Kalman filter for the estimation of the rotor position of BSM in the high speed range where the back-EMF could be measured, and rotor position calculation method is directly determined according to the formulas of the flux linkage model and back-EMF These methods are not applicable for the zero and low speed range of BSM used as the starter for engine cranking, where the back-EMF can’t be detected, and the accuracy of the position estimation could be affected by the interference of load and speed changes during the starting procedure.
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