In this article, a full-domain harmonic potential balance (HPB) model, which is free of subdomain division and cumbersome geometric transformations, is presented for 2-D magnetic field analysis of electrical machines. The key contribution is the proposed HPB equation, by which the harmonic distribution of magnetic vector potential in electrical machine is solved. To achieve this result, the singularity functions are applied to realize a global modeling. Then the full-domain magnetic vector potential distribution equation, which implies the boundary conditions, is established. For radial-flux electrical machines with 2-D annular domain, the logarithm-translation mapping is applied to transform the shape of domain into strip. The image domain extension is proposed to construct symmetry and periodicity for harmonic modeling. The HPB equation is then derived by 2-D convolution theorem and regularized by symmetry analysis. A case study is performed by examining the magnetostatic field distribution of a 6-slot/4-pole permanent magnet machine, and comparing results from finite element analysis validate the HPB model. In light of its accuracy and simplicity, HPB model could be a promising analytical modeling method for electrical machines.

A high-power and high-repetition-rate widely tunable narrow-linewidth low-gain-band Ti: sapphire laser dual -end pumped by a 10 kHz 532 nm pulsed laser with an output wavelength of 690-760 nm was demonstrated. A seed-self-injection coupled cavity based on a Littman grating and dispersive prism was employed to narrow the output linewidth. When the pump power was 40.1 W, a maximum output power of 1.89 W at 730 nm was obtained with a linewidth of 1.5 pm and a pulse duration of 38.7 ns. The corresponding conversion efficiency was 4.71 %, and the beam quality in the x and y directions was 1.94 and 1.91, respectively. By successively rotating the front cavity mirror and broadband total reflector, a stable near-single-longitudinal-mode output of 690-760 nm could be achieved, with a maximum power of 2.35 W at 760 nm.

The dual-stator winding induction generator (DWIG) is an alternative main generator in a variable frequency ac power system. So far, the existing studies have not covered the issue of DWIGs excitation controllability, which is a matter of importance for airworthiness. In this article, we develop an impedance-based modeling and analysis technique to investigate DWIGs excitation controllability. Two related topics are presented: the spontaneous self-excitation analysis in uncontrolled system and the implicit internal self-excitation pattern analysis in actively controlled system. In the topic about spontaneous self-excitation, a virtual impulse source technique is developed to derive the impedance-based method properly in the analysis for uncontrolled DWIG. In the second topic, the analysis performed in the presence of a closed-loop controller figures out the same underlying mechanism in both the plant's open-loop stability and the spontaneous self-excitation. The experimental results verify the proposed analysis and techniques that benefit the comprehensive understanding and practical application of DWIG-based power system.

提出一种适用于电推进飞机的基于定子双绕组感应发电机的航空交流并联发电系统.目前电推进飞机电力系统架构设计中沿用了航空变频交流发电系统广泛使用的变速变频同步发电机.现有研究实践中,变速变频同步发电机组被认为在常规运行时只能工作于非并联状态.这种各发电通道独立的架构限制了系统的电力集成度.利用定子双绕组感应发电机的异步发电特性和其控制绕组AC-DC-AC机组互联拓扑,可以突破电推进飞机发电系统使用变速变频同步发电机而无法交流并联的限制.提出一种应用于定子双绕组感应发电机待并联机组的基于功率流调节的协调并联控制方案以实现不依赖原动机的频率相位同步调节.理论和实验表明该系统拥有灵活的并车控制性能和良好的并联输出功率自平衡性能,所提出的系统结构和控制方式使得定子双绕组感应发电机并联发电系统成为电推进飞机发电系统的一种可行方案.

In this article, we present a closed-loop dynamic control scheme for a dual-stator winding induction generator (DWIG) with selective harmonic elimination pulsewidth modulation (SHEPWM). This control scheme can be applied in a variable-frequency ac power system based on the DWIG, which is able to operate in low-carrier-ratio conditions, especially in high-power aeroapplications. Common closed-loop induction machine control schemes, such as vector control strategy, generally lead to control failure with SHEPWM implemented. This proposed closed-loop dynamic control scheme makes the dynamic operation of the DWIG power system feasible with SHEPWM. The scheme consists of three main parts: the complex-signal observer for DWIG, outer loop controller for DWIG, and stator flux-linkage trajectory tracking controller. The complex-signal observer provides the extra steady-state components of control signals by using the complex coefficient filter. The outer loop controller provides the dynamic commands for control signals. Finally, the flux-linkage trajectory tracking control (FTTC) synthesizes these signals and serves as the inner loop. The simulation and experimental results verify the validity and effectiveness of the proposed scheme.

Induction motors are widely applied in the fields of industry with the merits of simple structure, stable performance and convenient manufacturing. However, in some servos with high reliability requirements, the installation of the speed sensor not only increases the volume and the weight, but also reduces the reliability of the driving system. To solve this problem, speed-sensorless technique has gained an increasing number of attention and research. This paper proposes the adaptive full-order (AFO) observer based on bilinear transformation, simulation has been done to prove the effectiveness.

In this paper, the performance of the dual stator-winding induction generator (DWIG) variable frequency ac (VFAC) generating system with unbalanced loads is analyzed, and an asymmetrical operation analysis method based on a three-port load network model is proposed. This method has four key steps: (1) deriving the three-port load network model for three-phase four-line unbalanced loads; (2) establishing the positive sequence, negative sequence, and zero sequence equivalent circuits for the DWIG; (3) combining the above model and circuits together to obtain the system whole equivalent model; and (4) writing the corresponding equations and solving them. The experimental results and the calculation results are almost consistent, which proves that the proposed method is correct and valid, and the DWIG VFAC generating system with unbalanced loads has a good performance.

In aircraft variable frequency AC power system,short circuit is a common fault worthy of in-depth study.In this paper,the transient performance of the dual stator-winding induction generator (DWlG) is analyzed under the condition when short circuit simultaneously occurs in both control winding and power winding.The analytical solution is used to derive the short circuit attenuation rules,the maximum current expression and the corresponding arrival time.The result shows that there are two DC decaying components and one AC decaying components when short circuit occurs,corresponding to the two set of stator-windings and rotor winding respectively.The transient reactance of the DWlG is similar to the d-axis sub-transi ent reactance of the synchronous machine,and is inversely proportional to the transient current peak value.Analysis shows that the DWlG transient current is smaller than the synchronous machine.The conclusion of the paper can help with estima ting DWiG's transient current,guiding electromagnetic design of the generator,and providing theoretical reference to the design of the protection unit and controller of the power generation system.

Two problems must be solved in the speed sensorless vector control of dual stator-winding induction generator (DWIG) working as the integrated starter/generator in the variable frequency ac (VFAC) aircraft power system: the speed estimation and the rotor flux observation. This paper proposes a novel reduced-order extended Kalman filter (EKF) to estimate the speed accurately even in the starting process with less computation by utilizing the characteristics of DWIG. The paper firstly introduces the principle of the novel EKF in allusion to DWIG. After that, the simulation of speed sensorless DWIG VFAC system is built in the MATLAB/SIMULINK, under the circumstances of the load mutation and with the inaccurate motor parameter. The result of simulation proves that the novel reduced-order extended Kalman filter proposed in this paper can real-time estimate rotor speed and rotor flux very accurately, and based on which the speed sensorless drive system has good static and dynamic performance.

研究了在车载低压大电流应用场合的笼型异步电机发电技术.在分析异步电机发电系统控制规律的基础上,使用转差频率控制策略建立了异步电机闭环发电系统.同时制作了一台输出为28.5 V/15 kW的样机,并给出了实验波形.实验结果表明,该发电系统能够稳定地输出28.5 V/15 kW直流电能,验证了异步电机发电系统在低压大电流应用场合的技术可行性.

In this paper, a novel vector control strategy for variable frequency AC (VFAC) power system based on the dual stator-winding induction generator (DWIG) is proposed. The mathematical model of DWIG is investigated, which shows the model of DWIG can be simplified as a single stator-winding induction generator when the two sets of stator windings are tight coupled. The simulation results verify the principle and performance of the proposed method.

在航空变频交流电(AC)源中,为保证机载用电设备的正常工作,发电系统应具备适应不对称负载的能力.为了分析基于定子双绕组异步电机(DWIG)的变频交流发电系统带不对称负载运行的性能,提出了一种负载多端口网络不对称分析方法.首先,推导出三相四线制不对称负载的多端口网络等效电路;其次,将其与DWIG的正序、负序和零序等效电路结合,建立完整的DWIG不对称运行的等效模型;最后,根据该模型列写相应的方程并进行求解,最终得到DWIG不对称运行时的输出电压.基于该分析方法,可实现对该发电系统带不对称负载运行性能的定量分析,并得到了电机参数对于输出电压不对称度的影响.样机计算结果与实验结果较一致,验证了DWIG具有较强的带不对称负载的能力.