Excited Machine Research Articles

A New Linear Vernier Permanent-Magnet Machine Using High-Temperature Superconducting DC Field Excitation

In this paper, a new linear Vernier permanent-magnet machine is proposed. By using high-temperature superconducting (HTS) winding to provide an additional field excitation, a hybrid excitation machine is achieved. The HTS field winding is accommodated in the stator and PMs are mounted on the mover surface. By regulating the dc current flowing in the HTS field winding, the air-gap flux can be flexibly controlled. First, the proposed machine and the cooling system for the HTS field winding are presented. Second, the operating principle of the proposed machine is discussed. Third, by using the 3-D finite element method, the performance of the proposed machine is evaluated. Finally, a conclusion is drawn.

A Controllable Power Distribution Strategy for Open Winding Hybrid Excitation Generator System

The open winding permanent magnet generator system is suitable for applications such as renewable energy power generation systems with multiple power sources, due to its high power density, relatively few power switches, and high degree of integration. However, for this system, it is difficult to quantitatively control the power distribution between different energy sources. In this paper, an open winding hybrid excitation generator system is presented, and for this system, a controllable power distribution strategy is investigated. In the proposed strategy, the excitation current is regulated according to the error in the current loop of the auxiliary energy source, which can achieve the regulation of the output power of the generator and finally realize the power quantitative control of the auxiliary energy source. Then, the topologies of the hybrid excitation machine are analyzed and chosen with emphasize on the influence of the flux regulation capability on the control capability of system power distribution. The experiments are carried out on a parallel hybrid excitation flux-switching (PHEFS) generator system, and the results verify the correctness and effectiveness of the proposed controllable power distribution strategy and the power distribution capability of the PHEFS generator.

Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter

The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this contribution, a six-phase double-star outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A high speed response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high-power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents was possible, improving the transient behavior of the synchronous generator. In this paper, we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage, and reduce the steady-state torque ripple. Experimental results are given for validating the models implemented for the analysis.

Novel method for research on exposure to nonlinear vibration transferred by suspension of vehicle

The paper presents novel method for research on exposure to nonlinear vibration of passenger car suspension as nonlinear dynamical system. Also paper provides a discussion on the results of studies addressing the impact exerted by damping properties of shock absorber on the vibrations being generated. The research was conducted on the car forced to vibration by the exciter machine with changeable frequency. The paper addresses results of analysis of application of one of the time-frequency representation techniques to the identification of structure of vibration. The obtained representation of the vibration allows determining time function of separate frequency bands, which represents the isolated vibration dynamics phenomena. Considering the variability of the time and frequency distribution of the vibration even in selected analysed bands, the time function was developed as exposure to vibration estimator. The recommended method makes use of function of exposure to vibration. The advantage of these method is possibilities of precise analysis of chosen frequency bands. The investigations conducted confirm considerable susceptibility to changes in the technical condition of shock absorber with regard to the assessment of human exposure to vibrations.

Loading noise effects on the system identification of composite structures by dynamic tests with vibrodyne

Abstract The design of new composite structures, and the system identification of existing structures strengthened through the application of composite materials, often require dynamic tests executed with the assistance of accurate forcing devices. The present paper presents a characterization of the force time-histories that can be applied through a vibrodyne, an electro-mechanical excitation machine that is able to generate vibrations, with known frequency and amplitude. Such a device is frequently employed when dealing the experimental modal analysis of composite structures at different scales. We conduct an experimental study on the forcing functions generated by a vibrodyne, and the mismatches between such loading histories and the theoretical sinusoidal profiles. Next, we study the effects of such mismatches on the simulated dynamic response of a simple structural model. Based on the results of such a study, we outline a procedure for building up a database of the real forcing functions applied by a vibrodyne, over a wide range of operating conditions. Such a tool can play a key role when conducting dynamical tests on next-generation composite structures through vibrodyne.

Novel Parallel Hybrid Excited Machines With Separate Stators

Hybrid excited (HE) machines combine the advantages of both high torque density and excellent flux regulation capability, while also having extensive applications. A novel partitioned stator HE machine employing two stators to allocate armature windings and excitations separately, is proposed in this paper. The permanent magnet (PM) pole-pair and wound field pole-pair are alternately placed on one stator to exhibit parallel magnetic paths, while the armature windings are located on the other stator. The iron-piece-rotor is sandwiched between the two stators. This machine inherits the advantages of stator-PM machine and further benefits from attractive flux regulation capability due to parallel topology. The operating principle and the slot/pole combination rule that are different from the conventional PM machine are illustrated. The two-dimensional finite element technique is used to evaluate the electromagnetic performance, confirming the mentioned advantages. A prototype is manufactured and tested to validate the predictions.

Analytical Investigation and Scaled Prototype Tests of a Novel Permanent Magnet Compulsator

Compensated pulsed alternator (compulsator) is one of the most popular choices of pulsed power supplies for fusion reactors, high-power pulsed lasers, and hypervelocity electromagnetic launchers because of its high energy density and power density. In general, external excitation in the form of self-excitation or pulse-excitation is adopted in compulsators together with iron core or air core. This results in heavy, bulky components and a system that is more complicated and less reliable. In this paper, a novel compulsator that is excited using a permanent magnet (PM) and is equipped with an iron-core or air-core stator is proposed. An excitation converter or brush-slip ring system is not needed in the novel system, which consequently makes it more reliable, less massive, and less voluminous than the external excitation machines. In addition, the novel PM compulsator acts not only as a pulsed alternator capable of delivering high-power pulses but also as a brushless PM dc motor that can be employed to charge the energy storage rotor. Thus, no external driving motor or gearbox is needed in the pulsed power system, which makes the system integrated and compact. In this paper, analytical models for the air-gap magnetic distribution, the back electromotive force, and the pulsed current waveform of the machine are deduced. A PM compulsator is designed and analyzed, and a scaled prototype of the PM compensated pulsed alternator is fabricated and tested. The actual output voltage waveforms and pulsed-current waveforms are sampled and compared with the predicted ones, which clearly demonstrate that the design of the PM compulsator is feasible.

Voltage Controller for a Synchronous Generator with Exciter

In this paper, the excitation controller for a synchronous generator (SG) with an exciter is presented, based on novel stabilization feedback actions comprising the SG rotor current and rotor voltage measurements. The novel stabilizing feedback actions are used to compensate the dynamic lag introduced by the exciter machine, and to improve the overall excitation system's dynamic performance without employing differential control actions. Namely, by avoiding differential control actions, an improved level of performance can be achieved without compromising the control system's sensitivity in relation to the measurement noise. Also, compared with the existing solutions based on a different set of stabilizing feedback signals, the controlling structure proposed in this paper enables a more stable and faster dynamic response, which is illustrated in the paper by means of the system frequency response analysis. The performance of the proposed solution is verified through the set of simulation and experimental runs presented in the paper. While the controller design is based on a simplified generator model, the simulations are carried out using the full order generator and exciter models. The experimental tests were carried out on a 300 MW thermal power plant aggregate with an AC exciter.

A New Parallel Hybrid Excitation Machine: Permanent-Magnet/Variable-Reluctance Machine With Bidirectional Field-Regulating Capability

This paper presents a new topology of parallel hybrid excitation machine (PHEM), which integrates permanent-magnet synchronous motor (PMSM) and variable-reluctance machine, namely, doubly salient electromagnetic machine (DSEM), and provides a solution to better field-regulating capability. The configuration and the operation principle of the proposed PHEM are introduced. The combination criterion and design consideration are discussed. The performances of the two axial sections (PMSM and DSEM) are studied by 2-D finite-element analysis (FEA), respectively, to achieve reasonable integration. The field and voltage regulation capability of the PHEM is further investigated by 3-D FEA. A prototype PHEM is designed, manufactured, and tested. The measured results verify structural validity and finite-element predictions. The loss is predicted, and the measurement of short-circuit current illustrates the capacity of deexcitation at fault. The results confirm that the PHEM achieves effective power superposition of two different brushless machines. Bidirectional field-regulating capability facilitates a wide field regulating range of 6.5:1 under no load.

Vector Control Methods for Brushless Doubly Fed Reluctance Machines

This paper is concerned with flux and voltage vector-oriented control of a promising brushless doubly fed reluctance machine (BDFRM) for generator and drive systems with limited adjustable speed ranges (e.g., wind turbines and/or pump drives). The BDFRM has been receiving increasing attention because of the low capital and operation and maintenance costs afforded by using partially rated power electronics and the high reliability of brushless design. Furthermore, it has the potential to offer competitive performance to its well-known slip-ring counterpart, i.e., doubly fed induction generator. The experimental studies have evaluated the control algorithms on a custom-built BDFRM in both motoring and generating modes under the maximum torque per inverter ampere conditions. The test results achieved should make a step forward toward the development of robust generic controllers for doubly excited machines.

Motor Control System Based on DSP Four-Bridge Arm Topology

This paper proposes a space vector motor control system based on DSP four-legged bridge topology A three-dimensional space vector control principle based on four-bridge arm three-phase inverter is introduced with a MATLAB model using space vector Motor Control Algorithm instead of traditional Motor Control method. A DSP experimental setup is also carried out to verify the control theory and simulation result. The experiment and simulation results show that the speed control system helps the asynchronous motor to achieve the consistent response characteristics with separately excited DC machine. When the motor doesn't work or the load is unstable, asynchronous motor can still achieve excellent electrical characteristics with the proposed speed control system, such as quick start, small overshoot and static torque ripple.

New Controllable Field Current Induced Excitation Synchronous Generator

The electrical machine using induced excitation system is a kind of brushless self-excited machine with low cost and high reliability, the induced excited machine would provide high power density at high-speed. But the low efficiency of the excitation system limits the development of this kind machine. Based on traditional excitation system, an improved construction induced excitation system is proposed in this paper. Adaptive control method is used to control the current direction in the stator auxiliary winding to replace constant DC excitation, the input current can change its direction according to the position of the rotor, the result is that all of induced currents at work in excitation system. Position sensors are fixed on the rotor and the stator field winding currents can synchronize with the rotor position according to the signal of the sensors. Experiments with the proposed structure are performed and compared with those of the traditional induced excitation system one. The results show that the new structure can improve the excitation system efficiency and reduce the cost.

Analytical Design of Flux-Switching Hybrid Excitation Machine by a Nonlinear Magnetic Circuit Method

The flux-switching hybrid excitation machine is an interesting brushless machine with magnets and excitation windings in the stator. Due to the unique structure and hybrid excitation, the assignment for electric excitation and permanent magnet excitation becomes a difficult issue. To explore a rapid design method, the nonlinear magnetic circuit analytical model of the element machine has been developed, which introduces the technologies of critical regions subdivision and iterative solutions for magnetic permeability into the magnetic circuit model. Then, the ampere turns of electric excitation, the recommended value of initial magnetic bridge flux density, the influence of stator yoke thickness on magnet dimensions and field regulating coefficient are also included. Finally, the finite element analysis and the experimental results are presented. The proposed method is not only reasonable and effective but also efficient, which provides a reference for the flux-switching hybrid excitation machine (FSHM) design and performance analysis.

Delay-dependent H∞ robust control for large power systems based on two-level hierarchical decentralised coordinated control structure

This article focuses on a novel two-level hierarchical decentralised coordinated control which consists of several local fuzzy power system stabilisers (LFPSSs) for each generator at the first level tuned by supervisory power system stabiliser (SPSS) at the secondary level for the transient stabilisation improvement of large power systems. First, in order to compensate the inherent nonlinear interconnections between subsystems in system dynamic model, a direct feedback linearisation compensator is proposed to act through the local excitation machine. Afterwards, the T–S fuzzy model-based decentralised LFPSS for each generator is designed. Then, for the purpose of improving dynamic performance, the SPSS is designed by using the remote signals from the wide area measurements system. However, there are unavoidable delays involved before the remote signals are received at the SPSS site or the control signals of SPSS are sent to the local systems. Taking consideration of the multiple delays, by using less conservative delay-dependent Lyapunov approach, the authors develop a delay-dependent H∞ robust control technique based on the decentralised coordinated control structure. Some sufficient conditions for the system stabilisation are presented in terms of linear matrix inequalities dependent only on the upper bounds of the time delays. Finally, the effectiveness of the proposed control scheme is demonstrated through simulation examples.

3F18 睡眠を誘導する加振装置の開発(GS20-3:生体計測(3))

3F18 睡眠を誘導する加振装置の開発(GS20-3:生体計測(3))

Dual control of synchronous generator for terminal voltage regulation-comparison with a single control

This paper deals with the application of a new excitation system for synchronous generator terminal voltage application. The proposed excitation system is based on the control of the main SG and the exciter machine (dual control). The comparison between the proposed structure and the system with single control shows the advantage of the dual control in reducing the energy loss in the exciter machine. Implementation in a real time domain is performed. Experimental results are presented and discussed.

Practical Implementation of Sensorless Torque and Reactive Power Control of Doubly Fed Machines

A recently proposed shaft position sensorless method for torque and reactive power control of the brushless doubly fed reluctance machine has proven successful in simulation studies. In this paper, its real-time performance has been evaluated on a custom-designed machine prototype. The preliminary experimental results have confirmed the viability of the scheme and represent a serious step toward the development of a generic virtually parameter independent controller for doubly excited machines. A wide range of applications is possible, including drive and generator systems with limited speed ranges (e.g., large pumps and wind turbines), where the cost savings of using a partially rated power electronic converter are significant.

Manufacturing Tolerances: Estimation and Prediction of Cogging Torque Influenced by Magnetization Faults

Permanent-magnet excited synchronous motor servo drives are increasingly employed in industrial applications. During mass production, deviations from the ideal machine occur. Thereby, parasitic effects such as cogging torque and torque ripple are influenced in particular. For permanent-magnet excited machines, the magnet's quality is important. There are many possible failure configurations requiring the study of their influence on the machine's behavior. In this paper, an approach for the estimation of cogging torque considering magnetization faults is presented. This approach is applied to determine crucial configurations of permanent-magnet faults. The intent is to evaluate the influence of the faulty magnetic materials with its asymmetries on the later produced machine. In the process, analytical and numerical methods are combined whereby finally a small computational effort with accurate results is achieved.

Parallel hybrid excitation machines and their control schemes for DC generation system

The parallel hybrid excitation machines (PHEM), which exhibit good flux regulation capability and wide constant power operating capability, can not only reduce the coupling of the PM flux and electrical excitation flux but also avoid demagnetisation that occurs in the series hybrid excitation machines. This study compares and analyses the electromagnetic performance of different PHEMs with emphasis on the excitation source location, structures, operation principles, reliability and axial utilisation. Then, their control schemes for voltage regulation of DC generation systems are analysed based on different critical control variables including the excitation current, the armature current, the electromagnetic torque and the applications are also discussed. Furthermore, an improved direct torque control (DTC) scheme is investigated to improve the system performance. A parallel hybrid excitation flux-switching generator employing the improved DTC, which shows excellent dynamic and steady-state performance has been achieved experimentally.

Employing Adaptive Particle Swarm Optimization Algorithm for Parameter Estimation of an Exciter Machine

Winding inductances of an exciter machine of brushless generator normally consist of nonsinusoidal terms versus rotor position angle, so evaluations of the inductances necessitate detailed modeling and complicated parameter identification procedures. In this paper, an adaptive particle swarm optimization (APSO), which is a novel heuristic computation technique, is proposed to identify parameters of an exciter machine. The proposed approach evaluates the model parameters just knowing the main field impedance, measured exciter field voltage and current. APSO is employed to solve the optimization problem of minimizing the difference between output quantities (exciter field current) of the model and real systems. Two modifications are incorporated into the conventional particle swarm optimization (PSO) scheme that prevents local convergence and provides excellent quality of final result. Performance of the proposed APSO is compared with those of the real-coded genetic algorithm (GA) and PSO with linearly decreasing inertia weight (LDW-PSO), in terms of the parameter accuracy and convergence speed. Simulation results illustrated in the paper show that the proposed APSO is more successful in comparison with LDW-PSO and GA.