With the rapid development of more-electric aircrafts, integrated starter–generator (ISG) with less volume and weight has become the development trend in aircraft power system applications. Advantages of high reliability and excellent power generation quality make the brushless wound-rotor synchronous starter–generator (BLWRSSG) most attractive candidate for the ISG system in aircraft application. In this article, four key technologies to achieve a high-performance BLWRSSG are comprehensively reviewed, including 1) high-efficient brushless excitation technology, 2) high-performance starting control technology, 3) rotor position estimation technology, and 4) rotating rectifier fault diagnosis technology. In each key technology, the basic operation principle, merit and demerit, and application of different topologies or methods in the literature are discussed and compared in depth. This article contributes to a thorough understanding of operation principle and key technologies of the BLWRSSG system, and provides a reference to researchers and engineers involved in research of aircraft ISG system.

This article presents a low-measurement effort and less storage space but an effective method to reduce the torque ripple. First, a torque-balanced measurement method is presented to obtain the flux-linkage characteristics at four torque-balanced positions. Then, a four-order Fourier series model is proposed to describe the entire flux-linkage and torque characteristics. To reduce the storage space, a polynomial-Fourier series model is proposed to describe the torque and current model from the rotor position and flux linkage. Based on the proposed polynomial-Fourier series model, a novel model predictive torque control (MPTC) is implemented to minimize the torque ripple with flux-linkage-based torque estimation. Experimental results show that the proposed method can effectively reduce torque ripple with lower measurement effort and less storage space compared with the traditional MPTC method. The proposed method provides a low effort and convenient way to implement the advanced control of SRMs in the industry application.

Accurate information about the field current of the wound-rotor synchronous starter generator (WRSSG) is prerequisite for optimal start control research for WRSSG in the starting mode. However, as the field winding of WRSSG is in the rotating parts and there is no slip ring and brush mounted in the shaft, the measurement of the field current is not possible. A field current estimation method for the WRSSG from the brushless exciter side was proposed in this paper. In this estimation method, the rotor currents and voltages of the asynchronous brushless exciter were first estimated and then used to calculate the field current of WRSSG through the parametric average-value model of the rotating rectifier. Experimental results verified that the proposed estimation method showed sufficiently accurate estimation performance both in steady and transient states.

This paper proposes a hybrid sensorless control strategy for rail transit application employing Interior Permanent Magnet Synchronous Machine (IPMSM), which works under low switching frequency. Due to a long system time-delay, the convergence rate of estimated position in the sensorless dynamic region is reduced. As the speed increases, the dq-axis currents coupling is more severe, and deteriorates the control performance. In order to solve these problems, the analysis of time-delay effect on the IPMSM sensorless drives is firstly derived. Then, using q-axis current error, a global time-delay compensation method is designed to eliminate the lag-angle of estimated position. Furthermore,the effect of this compensation on audible noise reduction is also analyzed. Through a phaselocked loop (PLL), the hybrid estimated position is obtained from a normalized position error. Finally, a 3.7-kW IPMSM is tested to verify the feasibility of the proposed sensorless method.

The rotating rectifier in the brushless synchronous starter/generator is more vulnerable than others. Therefore, fault detection of the rotating rectifier is necessary. This study focuses on the identification of the diode failures in the rotating rectifier of the brushless synchronous starter/generator. Traditional approaches based on the analysis from the main exciter field current or main machine out-put voltage may lose the fault location information. To solve this problem, the fault features based on the rotor current are analyzed. With a simple rotor current restructuring approach, the magnitude ratio of second harmonic to fundamental obtained by bandpass filters on the restructured rotor current is employed to confirm the one diode open-circuit or one diode short-circuit fault. The experimental results verify the feasibility and effectiveness of the proposed method

In this paper, the cross-coupling phenomenon in the wound-rotor synchronous starter/generator system is studied. Due to the armature reaction, the excitation field is dragged away from the d-axis by the armature magnetic field and the cross-coupling inductance L _dq exists. What is more, the cross-coupling phenomenon also occurs in the excitation field, it means not only the mutual inductance M _df between the d-axis and excitation field exists, but also mutual inductance M _qf between the q-axis and excitation field exists. If this M _qf component is ignored, this will result in a torque calculated error, especially facing an intense armature reaction, the error can be more than 20%. The mathematical expressions of cross-coupling inductance L _dq , M _qf are derived. Based on these expressions, a more accurate torque equation is proposed. The validity of the proposed analysis is proved by showing the agreement with experimental results and maximum torque per ampere (MTPA) loci.