Doubly Salient Electromagnetic Generator Research Articles

Fault-Tolerant Control of Doubly Salient Electromagnetic Generator Based on Capacitor Split-Phase Bridge Converter Under Loss of Excitation

Doubly salient electromagnetic machine (DSEM) has the advantages of simple construction, easy power generation control and convenient fault de-excitation, making it a promising application in the aviation field. Aviation power generation system puts forward higher requirements for the reliability of generators. Despite the various studies on the fault-tolerant control of DSEM, there are few studies on fault-tolerant control of excitation fault in aviation power generation system. Therefore, the main purpose of this paper is to achieve fault-tolerant power generation (FTPG) system for doubly salient electromagnetic generator (DSEG) on the event of excitation fault and improve the fault tolerance ability of the system, while can improve output power and reduce copper loss of DSEG under loss of excitation. This paper analyses the basic principle of normal power generation about DSEG, establishes its equivalent circuit after excitation loss, and dissects the control strategy for the FTPG with loss of excitation based on a bridge converter. Besides, this paper also proposes a fault-tolerant control system and its control strategy based on a capacitor split-phase bridge (CSPB) converter for DSEG, with higher generated power as well as lower copper loss. Based on the above hypothesis, experiments are performed on a power generation system for 12/8 pole DSEG to verify the feasibility of the proposed method.

Output Power Capacity Improvement Based on Three-Phase Current Balance Control for the Doubly Salient Electromagnetic Generator System

The doubly salient electromagnetic generator (DSEG) has the advantages of flexible control, high robustness, and low cost. Since multiple stator poles share a common set of field windings, the magnetic circuit of each phase is asymmetrical, which limits the output performance of the DSEG. The three-phase current balance control for the DSEG system was proposed. By investigating the current waveform under the angular position control (APC), a three-phase current prediction method was proposed. The conduction angle of the power switches in the active rectifier was predicted to make the three-phase current balanced. Based on the analysis and experiment, the current waveform was further analyzed, and the effectiveness of the three-phase current balance control was verified. Compared with the APC method, the output power capacity was improved using the three-phase current balance control under a limited winding current density. The maximum potential of the DSEG was explored, and the electromagnetic load capacity of the DSEG was fully released.

Minimum Field Current Increment Control for Doubly Salient Electro-Magnetic Generator With Improved Dynamic Performance

The dynamic response of conventional doubly salient electro-magnetic generator (DSEG) system with uncontrolled rectification is slow, owing to its large time constant resulting from the large energy storage capacitance and field winding inductance. In this article, the minimum field current increment control strategy is proposed for the DSEG system with angular position control (APC) rectification to solve this problem. Based on the ampere-second balance of the energy storage capacitor on the load side, the output voltage estimation model of APC is established to analyze the working characteristics of APC under different conditions in detail. Then, the method to minimize the field current increment by controlling the conduction angle is put forward to improve the dynamic response, because the smaller variation corresponds to the better dynamic performance. Finally, the experiments on a 12/8 pole DSEG system with controlled rectification are implemented to validate the effectiveness of the proposed control strategy, and the improved dynamic performance is observed in the results.

A Current Self-Injection Based Position Sensorless Control for DSEG With Controlled Rectification

The controlled rectification method with positon sensor can effectively improve the output power of the doubly salient electromagnetic generator (DSEG), but weakens the advantage of no position sensor for the traditional DSEG with uncontrolled rectification. To solve this problem, a current self-injection based position sensorless control method is proposed for DSEG with H-bridge semi-controlled rectifier (HBSCR) in this article. Based on the operation principle of DSEG and HBSCR, the position estimation method is developed from the positive zero-crossing point of inductive electromotive force (EMF), which is indirectly observed through the test current self-injected by the inductive EMF. According to the relationship between generation current and test current, a test current self-injection method without presetting injection width is put forward, and the corresponding sensorless control strategy is established with the combination of angular position semi-control. Then, the compensation strategy is further presented to improve the accuracy of the proposed position estimation method. Finally, the simulations and experiments are implemented on a three-phase DSEG to validate the feasibility and correctness of the proposed sensorless control strategy.

Capacitor-Energy-Based Control of Doubly Salient Brushless DC Generator for Dynamic Performance Optimization

A DC-link voltage regulation method is proposed based on capacitor energy control (CEC) for the doubly salient electro-magnetic generator (DSEG) system. Instead of tracking the DC-link voltage, the stored energy in the DC-link capacitor is set as the control target in the outer loop. A proportional component that converts the command output current into the command field current is developed between the capacitor energy loop and field current loop. The coefficient in the proportional component is investigated based on the mathematical model of the 12-8 pole DSEG, considering the load and speed variation. The dynamic response of the DSEG system is accelerated and the DC-link voltage variation is reduced with the proposed method. Furthermore, the adaptability to speed variation of the controlled is optimized. Since the DC-link capacitance is an additional parameter, the influences of capacitor degradation are investigated. The conventional voltage control and the CEC are implemented and compared on a DSEG platform. The optimized performance of the proposed method is verified by both finite element analysis (FEA) and experiments. The proposed method provides optimized dynamic performance over the entire speed range, enabling the DSEG system as a competitive option in the aircraft application.

Non-uniform air gap modeling and electromagnetic characteristics of a new six-phase doubly salient electro-magnetic generator

The voltage harmonics of the six-phase doubly salient electro-magnetic generator (DSEG) are large, and the electromagnetic isolation is poor due to the mutual inductance of the armature winding. An optimization scheme for the stator non-uniform air gap structure is proposed. By establishing a non-uniform air gap angle function model, the analytical expression of the induced electromotive force in the non-uniform air gap structure is derived. Using finite element and mathematical model to verify that the stator tip is changed from circular arc to linear structure can increase power and reduce voltage high harmonics, improve the power quality of the generator. Based on the equivalent magnetic circuit, the influence of the winding method of the excitation winding on the mutual inductance of the armature winding is studied. When the field winding is wound interval every two stator poles, the mutual inductance is small. The electromagnetic properties of the new six-phase electric excitation double salient pole are analyzed by two-dimensional finite element analysis. The rationality of the proposed motor structure is verified by experiments.

Dynamic Performance Improvement of Doubly Salient Brushless DC Generator System With Controlled Rectifier

The doubly salient electromagnetic generator (DSEG) is gaining increasing attention in aircraft high voltage dc generator application due to its simplicity and de-excitation ability. However, the field winding inductance and the dc-link capacitor result in a larger electrical time constant. The dynamic response is decelerated, leading to difficulties in meeting aircraft electrical power standards. Minimum transient point tracking (MTPT) strategy based on the trajectory with minimum field current variation is proposed for the DSEG system with an angular position control (APC) controlled rectifier. Since the dc load current depends on both field current and the turn- off angle, the change in the field current is minimized and the dc load current is varied by controlling the turn- off angle. The trajectory of the optimized turn- off angle is studied to partly or fully fill the gap between the field currents at different loads. By tracking the MTPT trajectory, the change of the field current is decreased during the sudden load changes. The transient process is accelerated and the voltage variation is suppressed. In most operations, the voltage variation can be even neglected under both loaded and unloaded conditions. A 9-kW DSEG system based on controlled rectifier is implemented. The MTPT strategy is verified by experiments. The performances of the diode rectifier, controlled rectifier with fixed turn- off angle, and controlled rectifier with MTPT are compared. The dynamic performance is improved by the proposed method, making the DSEG more competitive in aircraft applications.

The Output Voltage Control Strategy for DSEG With Controlled Rectification Based on Conduction Angle Estimation

Owing to the merits of smaller voltage ripples, lower armature current and cost compared to full-control (FC), the angular position semicontrol (APSC) scheme is proposed in this paper for low-speed range of the doubly salient electromagnetic generator (DSEG) operating over wide speed range, which improve the output voltage without increasing the field current. In APSC, the energy is stored with positive current in the inductance rising area and negative current in the inductance falling area, by which the output power and voltage increase, and the excitation current reduces. Moreover, in order to improve the poor dynamic performance resulting from the large-storage capacitor required for APSC, first, an ideal output voltage model is established according to the ampere–second balance of the energy storage capacitor on the load side. Second, several correction methods are investigated to enhance the accuracy of the ideal model. Finally, based on the conduction angle estimation model, a novel output voltage control strategy is put forward. The feasibility and superior dynamic performance of the proposed strategy are validated by the experiment results.

Behavior and functional modeling methods of doubly salient electromagnetic generators for aircraft electrical power system applications

The Doubly Salient Electromagnetic Generator (DSEG) is a promising candidate in aircraft generator application due to the simplicity, robustness and reliability. However, the field windings and the armature windings are strongly coupled, which makes the inductance characteristics non-linear and too complex to model. The complex model with low precision also leads to difficulties in modeling and analysis of the entire aircraft Electrical Power System (EPS). A behavior level modeling method based on modified inductance Support Vector Machine (SVM) is proposed. The Finite Element Analysis (FEA) inductance data are modified based on the experiment results to improve the precision. A functional level modeling method based on input–output characteristics SVM is also proposed. The two modeling methods are applied to a 9 kW DSEG prototype. The steady state and transient process precision of the proposed methods are proved by comparing with the experiment results. Meanwhile, the modeling time consumption, the application time consumption and the calculation resource demand are compared. The DSEG behavior and functional modeling methods provide precious results with high efficiency, which accelerates theoretical analysis and expands the application foreground of the DSEG in the aircraft EPS.

Open-Circuit Fault-Tolerant Characteristics of a New Four-Phase Doubly Salient Electro-Magnetic Generator

In order to improve the reliability of a more sustainable mobility generator, a four-phase Doubly Salient Electro-Magnetic Generator (DSEG) and its phase-isolated rectifier are proposed in this paper. The mathematical model of the machine and fault-tolerant rectifiers is proposed, which indicates that the four-phase fault-tolerant DSEG should have symmetric phases. With the asymmetry analysis of the traditional 8/6-pole DSEG, a new 12/9-pole DSEG with symmetric phases is proposed. The four-phase full bridge rectifier, positive half-wave rectifier and four-phase H bridge rectifier are presented. The voltage waveforms, no-load characteristics and loading characteristics with different rectifiers will be given based on the simulation and the experiment on a prototype of DSEG, and the results show that the four-phase H bridge rectifier has the best fault tolerant no-load characteristic and external characteristic, except that it needs more diodes.

Voltage Regulation System of Doubly Salient Electromagnetic Generator Based on Indirect Adaptive Fuzzy Control

In this paper, a voltage regulation system based on indirect adaptive fuzzy (IAF) control for doubly salient electromagnetic generator (DSEG) is proposed to improve the robustness of the system and reduce output voltage ripple. The operating principle of IAF controller is described in detail subsequently and the stability condition of the system is deduced by Lyapunov function based on the mathematical model and working principle of the generator. Moreover, the selection method of parameters and control strategy are determined with the adaptive fuzzy control law. Finally, a field-circuit coupling simulation model of voltage regulation system for DSEG using IAF controller is constructed by finite element analysis technique and transient solver of control circuit. The simulation results show that DSEG using IAF controller has good static characteristics, high robustness, and low output voltage ripple.

Analysis of a new five‐phase fault‐tolerant doubly salient brushless DC generator

The fault-tolerant ability of a multi-phase doubly salient electromagnetic generator (DSEG) makes it suitable for important applications. However, asymmetric phase windings are a drawback of the traditional five-phase DSEG. This study presents the design of a new five-phase brushless DSEG with symmetrical phases and a robust rotor. The proposed stator poles, rotor poles, and their pole arc criteria form a general design basis for the multiphase DSEG with minimum cogging torque. The proposed new winding configuration overcomes the phase asymmetry drawback of the traditional DSEG. An analysis of the characteristic of the no-load and the loading operation of the five-phase DSEG shows that the five-phase DSEG has fewer harmonics than the three-phase DSEG does. Additionally, the five-phase DSEG has high fault-tolerance ability because adjacent phases will take over the activity of the fault phase if there is an open-circuit fault. Simulated and experimental results of machine performance under the same working conditions offer verification of the design principles presented.

Efficiency Improvement and Thermal Analysis of a Totally Enclosed Self-Cooling Doubly Salient Generator With Optimized Stator Yoke

In this paper, first, the distribution of electromagnetic loss of the proposed doubly salient electromagnetic generator (DSEG) with the variation of defined stator yoke width coefficient is analyzed. The design of stator yoke for the proposed DSEG is of great significance to the power density and output efficiency improvement due to the introduction of field winding. By building a 3-D thermal finite element model based on the optimized dimensions and calculated electromagnetic loss, thermal performance of the proposed DSEG is predicted to ensure the maximum temperature rise in the safe range. The impact of current density on thermal performance is studied as well. Finally, a totally enclosed self-cooling prototype DSEG has been developed and tested. Experimental results confirm the validity of the proposed DSEG with optimized stator yoke for a stand-alone power system application.

Investigation of a Variable-Speed Operating Doubly Salient Brushless Generator for Automobile On-Board Generation Application

In this paper, a variable-speed operating doubly salient electromagnetic generator (DSEG) for an automobile power system is proposed and investigated. Analysis and comparison between the 12/8-pole and the 18/12-pole configurations are given. The 18/12-pole DSEG is more suitable for the wide-speed range operation in terms of the capability of output power and efficiency due to the smaller reactance. The characteristic of flux regulation for the constant power operation in a wide speed range is analyzed, and the corresponding loss variation and efficiency is obtained as well. Finally, a prototype 18/12-pole DSEG has been designed. Both the simulation and the experimental results indicate that the proposed DSEG can offer a more desirable and stable power performance over a wide speed range with simple control for the automobile on-board generation application.

Iron Loss Analysis of Doubly Salient Brushless DC Generators

The doubly salient electromagnetic machine (DSEM) is a kind of variable reluctance machine, which is different from the conventional ac electric machines. A new 24/16-pole DSEM is presented, and the configuration and operation principle are discussed. Based on the comprehensive study of the field distribution feature, the DSEM is separated into eight sections to investigate the iron loss distribution. In order to predict the iron loss of the doubly salient electromagnetic generator (DSEG), the flux density variations of each section are resolved into radial and circumferential waveforms, and Fourier transform is utilized in consideration of harmonic components. A calculation model of iron loss is established, and the coefficients are determined by the measured data at different speeds. The iron loss distribution of the DSEG is investigated. The proportion of iron loss to copper loss is further analyzed under different load conditions. Moreover, the influences of speed, air-gap length, and field current on iron loss are analyzed and summarized. Finally, the calculation and analysis of iron loss are verified by experimental results.

Design and simulation of nonsingular terminal sliding mode controller for doubly salient electromagnetic generator system

A strategy of nonsingular terminal sliding mode control is proposed for the voltage regulation system of DSEG(Doubly Salient Electromagnetic Generator). The structure of DSEG is described and its mathematical model is established,based on which,the operating principle of voltage regulator based on proposed control strategy is analyzed in detail and the corresponding sliding mode surface equation and sliding mode law are given. The control law parameters are calculated according to the constraint conditions of Lyapunov stability equation and the carrier wave intersection with fixed PWM control. A field-circuit cosimulation model is built based on the electromagnetic finite element analysis technique and the control circuit. The results of steady-state and dynamic simulations for DSEG show that,the voltage regulation system of DSEG based on the nonsingular terminal sliding mode control has excellent steady-state and dynamic performances,with small voltage ripple,short recovery time and little dynamic output voltage variation.

Analysis and Verification of the Doubly Salient Brushless DC Generator for Automobile Auxiliary Power Unit Application

The doubly salient brushless dc generator (DS-BLDCG) is constituted by a doubly salient electromagnetic generator (DSEG) and the associated rectifier circuit. The DS-BLDCG is suitable for the automobile auxiliary power unit (APU) application due to its merits of simplicity, high robustness, low cost, and flexible control. Since no constraint is imposed to the number of phases of the onboard brushless dc generator, the polyphase DSEG can be employed. In this paper, a 3-phase 12/8-pole DSEG and a 4-phase 16/12-pole DSEG with a rectifier circuit for the APU application are proposed. The taper stator pole and broadened rotor pole structure utilized to increase maximum output power is introduced in the four-phase DSEG design. Based on the two-dimensional (2-D) finite-element method (FEM) and field-circuit coupling analysis, a comprehensive comparison is presented. The 16/12-pole DS-BLDCG with broadened rotor pole exhibits lower peak value of the phase inductance yet larger negative phase current commutation overlapping angle. The rectifier circuit of the 16/12-pole DS-BLDCG is more complex and the copper consumption of the 12/8-pole DS-BLDCG is slightly less. A prototype 12/8-pole DS-BLDCG for the APU application is designed and developed. Both the simulation and experimental results indicate that the developed DS-BLDCG is a promising option for automobile APU application.

A New Topology of Low Speed Doubly Salient Brushless DC Generator for Wind Power Generation

The unit machine of the traditional doubly salient electro-magnetic generator (DSEG) has a 6/4-pole structure, so it must have a large number of stator poles when used as a low speed wind turbine generator. The matching relationship between the stator pole number and the rotor pole number of a multi-poles-rotor DSEG is deduced, and a new 3N/4N-pole DSEG is proposed. The magnetostatic field distribution, excitation inductance characteristic, as well as output characteristic of the DSEG is investigated by 2-D and 3-D finite element analysis. Comparisons between the two different structures are presented in terms of power density, voltage ripple and efficiency. A low speed 24/32-pole prototype machine is developed, and the experimental results are given to verify the validity of the simulation analysis and the reasonable structure of 3N/4N-pole DSEG.

Study on the Power Control Method of a Stand-Alone Wind Energy System Based on DSEG

The Stand-Alone wind energy supply system equipped with a doubly Salient Electro-Magnetic Generator (DSEG) is presented in this paper. First, the analysis of the operating characteristics of wind turbine and DSEG is introduced. Based on the strategy of power signal feedback (PSF), the excitation current of DSEG is regulated, as a result, Electro-Magnetic torque of the DSEG is controlled and the maximum wind energy tracking is achieved. Battery is employed as an energy storage device and interfaced to the wind energy system through bidirectional DC/DC converter. The control strategies of the bidirectional DC/DC are proposed to balance the power differences between the generator and the power the load, so that voltage of the DC bus could be constant under varying wind speed and load. The simulation results show the effectiveness of the control methods.

A Novel Algorithm for Fast and Adaptive Maximum Power Point Tracking of Wind Energy Generation System

Keeping wind energy conversion system (WECS) running on maximum power point (MPP) can make full use of wind energy. In this paper, authors put forward a novel hybrid maximum power point tracking (MPPT) algorithm which combines three points comparing (TPC) method with power-signal feedback (PSF) method. WECS based on doubly-salient electro-magnetic generator (DSEG) is used to validate the effectiveness of proposed algorithm. The whole WECS is simulated in Matlab/SimuLink, simulation results obtained confirm that the proposed algorithm is more fast and efficient than TPC method.