Zhiquan Deng

Position Signal Faults Diagnosis and Control for Switched Reluctance Motor

An accurate rotor position signal is quite necessary for high-performance control of switched reluctance motor (SRM). In general, the position signal faults may lead to abnormal operation, which deteriorates the reliability of the switched reluctance drive system. Thus, it is quite vital but still a challenge to develop a control strategy that can diagnose and control the position signal faults in an autonomous way. In this paper, a square-wave position signal edge prediction-based control strategy is proposed for position signal faults diagnosis and position faults recovery. Integrated with the rotor position fault-tolerant control method, the SRM drive system can maintain reliable operation under different position signal fault conditions. In addition, a phase inductance slope-based sensorless control method is proposed for position fault-tolerant control under the extreme case with failure of all position signals. To verify the validation of the proposed methods, the experiments have been implemented in a 12/8 structure SRM prototype. The results show that the proposed control methods can further improve the fault-tolerant capability of the SRM system.

Compensation Strategy of Levitation Forces for Single-Winding Bearingless Switched Reluctance Motor With One Winding Total Short Circuited

In order to take advantage of conventional switched reluctance motors (SRMs), the SRM is integrated with the bearingless motor technology and then a reluctance type of bearingless motor is created, named as bearingless SRM (BSRMs). Not only electromagnetic torque but also the levitation forces should be controlled in BSRMs, which is different from SRMs. The levitation forces should always exist even when winding fault occurs. Therefore, the absent levitation forces that ought to be produced by the fault winding should then be compensated by other winding. This paper proposes the compensation strategy of levitation forces for BSRMs when one stator winding is short circuited. The short-circuit fault is investigated and the short-circuit current is expressed for the derivation of radial forces. Then, the winding compensation rule and the mathematical model of levitation forces are developed to facilitate the compensation control for the motor levitation. After that, the proposed compensation strategy is verified by simulation results in MATLAB/Simulink. Experimental results are also presented to demonstrate the performance.

The Design of the Simple Structure-Specified Controller of Magnetic Bearings for the High-Speed SRM

Magnetic bearing system controllers using H∞ algorithms provide excellent interference rejection capability and robustness. However, in the conventional H∞ control design, the order of the controller is much higher than that of the plant, making implementation in practical engineering applications difficult. To solve the problem, based on the requirements of the theory of mixed sensitivity design method, this paper designs a simple structure-specified controller of magnetic bearings for the highspeed magnetic levitated switched reluctance motor (SRM) using backpropagation neural network function approximation characteristics. The proposed controller is of lower order than the traditional H∞ controller, and meets performance of H∞ controller, which is more suitable for practical implementation. By contrast with the traditional mixed sensitivity controller, results of simulations verify that the controller is reasonable. The controller is applied on the high-speed magnetic levitated SRM platform, and experimental results verify that the controller can achieve control of magnetic bearing systems with good disturbance rejection and robustness.

Optimal design of a bearingless switched reluctance motor

This paper presents a method of optimizing number of turns of the main and radial force winding for a bearingless switched reluctance motor (BSRM) with 12/8 teeth configuration based on its mathematical model. The radial force and torque of BSRM are analyzed on condition of different combinations of the magnetomotive force of two kinds of windings. The winding configuration has a strongly influence on the performance of BSRM. Effects of two kind of winding arrangements on mutual inductances for BSRM are analyzed, and its optimal winding structures are proposed.

Compensation strategy of short-circuit fault for a single-winding bearingless switched reluctance motor

Due to all winding currents are controlled independently, the fault-tolerant control of single-winding bearingless switched reluctance motor (SWBSRM) is more flexible. In this paper, a compensation strategy for short-circuit fault in SWBSRM is investigated to improve the reliability of BSRM. Firstly, the mathematical model with compensation for short-circuit fault is established with consideration of two-phase coupling. Secondly, the validity of the proposed model is verified by the finite element method (FEM). Then a compensation strategy based on this model is proposed to realize rotor levitation in short-circuit fault mode. Finally, the proposed strategy is verified by simulation.

Design and Characteristic Analysis of a Novel Bearingless SRM considering Decoupling between Torque and Suspension Force

A Bearingless Switched Reluctance Motor (BSRM) has a complicated character of nonlinear coupling; therefore, it is a hard work to operate BSRM stably. In this paper, a new type of BSRMs with novel rotor structure is proposed by analyzing relationships between motor structure and theoretical formulae of levitation force and torque. The stator structure of this new motor is same as that of traditional BSRM and each stator pole can coil one winding or two windings, while the pole arc of rotor is wider. In order to analyze the characteristics of the proposed BSRM, finite-element (FE) models are used and a 12/4 one-set-winding BSRM and a 12/8 two-sets-windings BSRM are taken as examples. The analysis results indicate that the new scheme is effective for a stable levitation. It can realize decoupling control of torque and radial force, thus simplifying its control strategy and improving the use ratio of winding currents. A control system is designed for the 12/8 BSRM based on deducing its mathematical model. Compared with traditional BSRM, the proposed scheme is easier to be implemented.

Nonlinear modeling of switched reluctance motor using different methods

Accurate modeling of flux-linkage characteristics is the basis of design and control of switched reluctance motor(SRM). The flux-linkage characteristic of SRM is a function of both the excitation current and rotor position. But due to the highly nonlinear characteristics of SRM, modeling is cumbersome. In this paper, three effective algorithms for modeling of SRM are investigated, which are based on subregional mathematical model, neural network and adaptive neural fuzzy inference systems(ANFIS) respectively. The performance of each method is validated and compared via matlab tools. Simulation results show that all these models can accurately and successfully modeling of SRM, while RBF neural network is the best. Moreover, a new SRM dynamic simulation model based on RBF is developed for verification. Simulation and experimental results validated the accuracy of RBF modeling algorithm.

A novel arithmetic based on coordinate transformation for sensorless brushless DC motor drives

This paper presents a novel method for sensorless BLDC motor drives, which is based on coordinate transformation, in order to compensate the rotor position detection error caused by the first-order low-pass filter over wide speed ranges. Two coordinate systems are defined, which are named as ‘a’ and ‘b’. For compensating the error, the angle β, which is between ‘b’ coordinate system and ‘a’ coordinate system, is controlled in real time, and the zero-crossing timing of reconstructed position signal, which is the projection on ‘b’ coordinate system from ‘a’ coordinate system, is just the phase commutation timing. The rotor position detection error is analyzed and experimental results verify the analysis and demonstrate advantages of the new arithmetic.

Novel structure of bearingless flux-switching motor for improvement of levitation force characteristics

Due to the temperature sensitivity and the cost issue of permanent magnets, the application of electrical machines with permanent magnets on the rotor are limited in spaces with high-temperature as well as disposable fields. To deal with these problems, bearingless flux-switching motor, which is a kind of electrical motors with permanent magnets located in the stator, is studied in this paper. Firstly, the principle of levitation force generation and its characteristics are illustrated and analyzed respectively. Then the mathematical model and levitation control strategy are derived under the assumption of large air-gap length. However, even if with the assumption of large air-gap, it still has unsymmetrical DC components in levitation current, which brings about complicated control effort. In addition, large air-gap length must lead to the reduction of density of levitation force and torque. Aiming at improvement of the characteristics of levitation force and simplification of the control strategy without under larger air-gap length assumption, a novel topology of bearingless flux-switching motor with paralleled structure is proposed. Detailed performance analysis and evaluation are performed by FEM for verification the effectiveness of the proposed topology.

Control of a hybrid excitation machine with open-winding structure for hybrid electric vehicles

Vector-controlled permanent magnet machine with open-winding structure can realize voltage regulation over a wide speed range and improve the generator power factor as well as the system integration degree when used in Hybrid Electric Vehicles (HEV). However, it is difficult for the above system to control the energy distribution between the battery and the engine. Hence, in order to realize the energy distribution control in multi-energy powertrain of HEV, a hybrid excitation generator system with open-winding structure is investigated in this paper and a double closed-loop control of battery current and generator excitation current is employed. Simulation results demonstrate the feasibility and effectiveness of the energy distribution control scheme.