Qian Zhang

Based on the quasi-two-dimensional (2D) field model of long primary double-sided linear induction motor (LPDLIM), an improved equivalent circuit model is proposed. First, the traditional equivalent circuit of LPDLIM is reviewed. Second, the skin effect correction coefficients for the secondary equivalent resistance and excitation reactance, and the secondary leakage inductance are derived. Moreover, an improved equivalent circuit model for LPDLIMs is presented, in which the leakage reactance of the secondary is considered, and the excitation reactance and secondary resistance are modified by the correction coefficients independently. Then, the slip frequency characteristics of various effect forces and variations of forces under different operations and mechanical air gap width are presented. Finally, the calculated forces by the proposed equivalent circuit are validated by the finite element method results and also compared with that of the traditional equivalent circuit model.

The improved equivalent circuit models considering the end effects are put forward to predict the performance of annular linear induction electromagnetic pump (ALIP) based on the one-dimensional analytical model built in this paper. First, the one-dimensional physical model of ALIP is established, and the analytical expressions of electromagnetic fields are deduced and the impact of the end effects on it is analyzed. Then, two equivalent circuit models including the model only considering the end effects and the model fully taking the end effects and the difference of synchronous velocity among the end effect traveling waves and the fundamental wave into account are developed. Meanwhile, the key impedance parameters in the equivalent circuit models are obtained and the correction coefficients of the impedance generated by the end effects are abstracted. Furtherly, the performances of a small designed ALIP are calculated by the conventional and two improved equivalent circuit models respectively, the results obtained from them are compared with measured data to validate the rationality and feasibility of the models proposed.

A novel, improved equivalent circuit model of double-sided linear induction motors (DLIMs) is proposed, which takes the skin effect and the nonzero leakage reactance of the secondary, longitudinal, and transverse end effects into consideration. Firstly, the traditional equivalent circuit with longitudinal and transverse end effects are briefly reviewed. Additionally, the correction coefficients for longitudinal and transverse end effects derived by one-dimensional analysis models are given. Secondly, correction factors for skin effect, which reflects the inhomogeneous air gap magnetic field vertically, and the secondary leakage reactance are derived by the quasi-two-dimensional analysis model. Then, the proposed equivalent circuit is presented, and the excitation reactance and secondary resistance are modified by the correction coefficients derived from the three analytical models. Finally, a three-dimensional (3D) finite element model is used to verify the proposed equivalent circuit model under varying air gap width and frequency, and the results are also compared with that of the traditional equivalent circuit models. The calculated thrust characteristics by the proposed equivalent circuit and 3D finite element model are experimentally validated under a constant voltage–frequency drive.

In order to study the static voltage stability(SVS) of distribution network with DFIG and SVC, the static model of DFIG and SVC is analyzed. The voltage stability index(VSI) which can reflect the degree of voltage stability of all load buses is derived in this paper, and DFIG is connected according to the best wind resources. A voltage stability analysis scheme is presented to rapidly rank the voltage stability margin of load buses, and the vulnerable bus is determined as the best locations to install SVCs. The detail of voltage collapse is studied based on the improved continuous power flow(CPFLOW) method. Simulation results show that the strategy releases the reasonable location of SVC, which can optimize the power flow distribution. Moreover, it can further improve the power supporting ability and SVS of distribution network with DFIG, which enables the system to bear severer load increasing.