Switched Reluctance Generator System Research Articles

A Voltage-controllable Switched Reluctance Generator System with a ring winding structure

A Voltage-controllable Switched Reluctance Generator System with a ring winding structure

Bipolar power converter and control of switched reluctance generator system for renewable energy storage

PurposeBecause of the shortage of energy, the development of green and reliable energy is particularly important. As a green and clean energy, wind power is widely used. As the core component of wind power generation, it is particularly important to choose generators with high reliability. Switched reluctance machine is widely used as generators because of its strong fault tolerance and high reliability. Therefore, this paper aims to propose a power converter and its control strategy to improve the efficiency of switched reluctance generators.Design/methodology/approachIn this paper, a full-bridge power converter (FBPC) instead of the asymmetric half-bridge power converter (AHBPC) is adopted to drive the switched reluctance generator (SRG) system. Compare the FBPC with the AHBPC, the FBPC has several advantages including low cost and modularization, and operation process of SRG winding current direction is variable.FindingsThe results show that the SRG system can keep smooth operation by the FBPC with relatively high efficiency.Originality/valueThe FBPC is suitable to drive the SRG system. Meanwhile, this paper introduces two excitation modes of the FBPC as three-phase three-beat mode and six-phase six-beat mode. When the six-phase six-beat control strategy is adopted, the dead band time of the converter can be avoided. At the same time, the SRG has higher efficiency.

Reliability evaluation on SRG with full-bridge power converter considering thermal stress

PurposeQuantitative reliability analysis can effectively identify the time the driving system needs to be maintained. Then, the potential safety problems can be found, and some catastrophic failures can be effectively prevented. Therefore, this paper aims to evaluate the reliability of the switched reluctance generator (SRG) driving system.Design/methodology/approachIn this paper, a method considering different thermal stresses and fault tolerance capacity is proposed to analyze the reliability of an SRG. A full-bridge power converter (FBPC) instead of the asymmetric half-bridge power converter (AHBPC) is adopted to drive the SRG system. First, the primary fault modes of the SRG system are introduced, and a fault criterion is proposed to determine whether the system fails. Second, the thermal circuit model of the converter is established to quickly and accurately obtain the junction temperature of the devices. At last, the Markov models of different levels are established to evaluate the reliability of the system.FindingsThe results show that the two-level Markov model is the most suitable when compared to the static model and the one-level Markov model.Originality/valueThe driving system of SRG will be more reliable after the reliability of the system is evaluated by the Markov model. At the same time, an FBPC is adopted to drive the SRG. The FBPCs have the advantages of fewer switching devices, higher integration and lower cost. The proposed driving strategy of the FBPC avoids the current reversal and the generation of dead zone time, which has the advantage of reliable operation. In addition, a precise thermal circuit model of the FBPC is proposed, and the junction temperature of each device can be obtained, respectively.

Circulating-Current-Excited Switched Reluctance Generator System With Diode Rectifier

In this article, a circulating-current-excited switched reluctance generator system using a standard diode rectifier is proposed and examined. It features a dc power source connected in series with the ring-connected windings, which provides the dc-bias current as the excitation current in the windings. Using a series-connected dc power source, a dc-bias current is easily realized in the ac winding. Compared with the existing machine having dc-bias in the ac winding, the proposed generator can provide dc power with a standard diode rectifier. Less active legs and no rotor position sensor are needed for the control of the circulating current of the proposed generator, which increases the reliability of the generation system. The system configuration and the operation principle are introduced in detail. Then, the electromagnetic performance of the proposed generation system is analyzed at both open-circuit and load conditions. The asymmetric current distributions are deduced and verified by the simulations. At last, the prototype is tested under varied operation conditions and the experiments agree well with the analysis.

Comparative Study of Switched Reluctance Generators With Separate Field Current and Circulating Current Excitations

In this paper, a circulating-current-excited switched reluctance generator system with the diode rectifier is comparatively studied with a field-current-separated switched reluctance generator. By using a DC power source connected in series with the winding to provide the circulating current, a controllable excitation field is established in the proposed generator. To highlight the influence of this DC voltage source, the injected field current of the field-current-separated generator is kept the same as the circulating current of the circulating-current-excited generator. Then, both advantages and disadvantages of the generators are summarized. The circulating-current-excited switched reluctance generator system inherits both the advantages of good reliability of the separated-winding generator by using the diode rectifier and low copper loss of the integrated-winding machine by combining the AC and DC current in one set of windings. Furthermore, two more practically conventional field-current-separated generators are also compared with the proposed generator in terms of the external characteristics. These two conventional generators have different winding configurations. At last, the analysis is verified by experiments.

Comparative Study of Discrete PI and PR Controller Implemented in SRG for Wind Energy Application: Theory and Experimentation

The Switched Reluctance Generator (SRG) has been widely studied for Wind Energy Conversion Systems (WECS). However, a major drawback of the SRG system adopting the conventional control is the slow response of the DC link voltage controller. In this paper, a Proportional Resonant (PR) control strategy is proposed to control the output voltage of the SRG system to improve the fast response. The SRG model has a high non-linearity, which makes the design of controllers a difficult task. For this reason, the important practical engineering aspect of this work is the role played by the SRG model linearization in testing the sensitivity of the PR controller performance to specific parameter changes. The characteristics of steady-state behaviors of the SRG-based WECS under different control approaches are simulated and compared. The controller is implemented on a digital signal processor (TMS320F28379D). The experimental results are carried out using a 250 W 8/6 SRG prototype to assess the performance of the proposed control compared with the traditional Proportional Integral (PI) control strategy. The experimental results show that the PR control enhances the steady-state performance of the SR power generation system in WECS. Compared to PI control, the rise and settling times are reduced by 45% and 43%, respectively, without an overshoot.

A Novel Power and Signal Composite Modulation Strategy for CCC-Based SRG in Distributed Microgrid

Switched Reluctance Generator (SRG) possesses the advantages of simple structure, low cost, high reliability and high fault tolerance. For promoting the intelligence of SRG based distributed power network, reliable communication is the key to achieve system monitoring, remote control, fault protection, etc. Power and Signal Composite Modulation (PSCM) methods are newly proposed to realize power-line communication (PLC) for SRG-based distributed microgrid. Two signal modulation methods are implemented on the basis of Current Chopping Control (CCC) by modulating either chopping references or chopping threshold of phase currents, so as to obtain voltage ripples with different frequencies to carry signals. Fast Fourier Transform (FFT) method is adopted for demodulating the transmitted data on receiving side. The proposed PSCM strategies are experimentally tested for SRG system with phase failure in distributed microgrid.

Efficiency Optimization Strategy for Switched Reluctance Generator System With Position Sensorless Control

A novel efficiency optimization strategy combined with a position estimation method is proposed for switched reluctance generators (SRGs) in this article. This practical performance improvement strategy can expand the application of SRGs small-scale wind energy generation system, which is a good solution for mitigating the fossil energy crisis. First, the position estimation method based on current injection of the idle phase is presented. The angle error caused by sampling in this method aggravates with speed. Accordingly, an error compensation strategy in the linear range of inductance is suggested. Second, a method for improving the efficiency of SRG system current is proposed. It determines the range of turn- off angle with the minimum root-mean-square value of phase current, and further obtains the optimal turn- on angle by the fitting expression to improve the efficiency. This efficiency optimization strategy combined with the new position estimation method can greatly enhance the efficiency and reliability of SRG system and eliminate the position sensor. There are many simulation and experiment results that validate the effectiveness of the proposed schemes.

Reliability Assessment of Double-Sided Linear Switched Reluctance Generator System Based on Hierarchical Markov Model

This paper presents a hierarchical Markov model to assess the reliability of a double-sided linear switched reluctance generator (DLSRG) system. The proposed reliability model can be applied to find the balance point of reliability assessment accuracy and model complexity. First, the dominant fault modes of the DLSRG system are highlighted to quantitatively obtain the operation states, survival or failure, with a novel failure criterion. Second, a hierarchical Markov model is adopted to build a systematic reliability model of the DLSRG system, wherein a state transition diagram can be built in the detailed description to constitute the graphical Markov reliability model. And then the solving process to get state probability matrix P ( t ) is intensively investigated. Notably, a reliability block diagram model is also built to compare with the hierarchical Markov model, whose results verify that the Markov model can capture the effect of fault-tolerance capability on system reliability. Moreover, it is expected that the one-level Markov model is the most suitable model for the DLSRG system for its ability of decreasing the model complexity and improving the assessment accuracy. Analytic investigation in conjunction with simulation and experimental measurements demonstrates the feasibility and validity of the proposed model.

Improvement of the Response Speed for Switched Reluctance Generation System Based on Modified PT Control

The Switched Reluctance Generator (SRG) is suitable for wind power generation due to its good reliability and robustness. However, The SRG system adopting the conventional control algorithm with Pulse Width Modulation (PWM) method has a drawback, low response speed. The pulse train (PT) control has been widely used in dc/dc power converters operating in the discontinuous conduction mode due to its advantages of simple implementation and fast response. In this paper, for the first time, the PT control method is modified and adopted for controlling the output voltage of SRG system in order to achieve fast response. The capacitor current on the output side is sampled and combined with the output voltage to select the pulse trains and the low frequency oscillation cased by PT can be suppressed by tuning the feedback coefficient of the capacitor current. Also, good performance can be guaranteed with a wide range of voltage regulations, fast response, and no overshoot. The experimental platform of an 8/6 SRG system is built, and the experimental results show that the PT control can be used for SRG system with good practicability.

Implementation of Wind Powered Switched Reluctance Generator System

This paper reports implementation of Battery Energy Storage System (BESS) for Switched Reluctance Generator (SRG) based wind power generation system supplying stand alone load. MATLAB/Simulink model of the SRG machine is developed using the characteristics acquired by solving the Finite Element Analysis (FEA) model of the machine used for implementation. Wind turbine is incorporated with Maximum Power Point Tracking (MPPT) control technique and to mitigate the problem of wind power fluctuation a BESS for a wind powered SRG with Isolated Bi-directional DC-DC Converter (IBDC) is proposed. The response of BESS is evaluated using MATLAB/Simulink computing tool and the results are reported. For experimental purpose, the wind turbine is emulated by a 12V DC motor. The BESS for wind powered SRG is analyzed and implemented using microcontroller to validate the simulation results.

Switched Reluctance Wind Generation System Based on Z Source Inverter

This paper uses Z source inverter in switched reluctance wind power generation (SRWPG) to connect to power grid. According to operation of switched reluctance generator (SRG), requirements of grid-connection and the unique single stage buck boost feature of Z source inverter, Z source inverter with space vector pulse with modulation (SVPWM) is adopted to satisfy the voltage level of grid-connection. A control method of grid-connection inverter is developed to keep the capacitor voltage of Z source inverter stable and regulate the active and reactive power. Simulation of SRG and Z source inverter are constructed based on MATLAB/Simulink platform. Simulation results reveal that Z source inverter is feasible and valuable in wind power generation on SRG system.

A novel adaptive controller in switched reluctance generator system

Switched reluctance generator (SRG) system is hard to obtain excellent generation performance using the traditional linear control theory due to its serious non-linearity of motor configuration and power supply mode. So a lot of non-linear control methods has been used in the SRG more and more. In this paper, a novel adaptive controller of single neuron adaptive PID is proposed in the SRG system. The single neuron adaptive PID controller has many advantages such as simple structure, adaptive ability and strong robust performance for its special control structure. The simulation model has been established firstly based on MATLAB/Simulink software with the proposed control strategy and the simulation results have been given compared with the traditional PID control under the same condition. The experimental results also have been given by the SRG system experiment platform. From the simulation and the experiment results, it is known that the system has the advantages of rapid dynamic response, quick voltage establishing and small voltage vibration. The single neuron adaptive PID controller has good application prospect in the switched reluctance generator system.

Closed Loop Control of Excitation Parameters for High Speed Switched Reluctance Generator Using MATLAB/SIMULINK

This paper presented a novel Proportional Integrator Current Chopping Control (PI-CCC) based on Switched Reluctance Generator (SRG).The fundamental principle of the PI-CCC is based on the minimization of torque ripple of the SRG. The excitation parameters for the SRG system operates at sufficiently high speed that it operates in the single pulse mode. In this paper PI-CCC based SRG modeled are simulated by using MATLAB/SIMULINK. In this model to analyze both dynamic and steady state system output its respectively, the power converter, excitation source, and loads were simulated based on SIMULINK/Sim power systems (PSB). Index Terms: Proportional Integrator Current Chopping Control (PI-CCC), Switched Reluctance Generator (SRG)

Implementation of the Three-Phase Switched Reluctance Machine System for Motors and Generators

This paper presents two three-phase switched reluctance machine systems. One is the dual motors drive for the electric locomotive traction; the other is the variable-speed generator system for wind power applications. The principles of the switched reluctance machine system operated at four quadrants, the scheme of the symmetrical traction at quadrant I and quadrant III, and the scheme of the symmetrical regenerative braking control at quadrant II and quadrant IV, are given. The transient phase current analysis and the energy analysis of the switched reluctance machine system at the operational state of braking or generating are evaluated, and the rotor position and the peak value of the phase current at three different conditions are given. The closed-loop rotor speed control of the main motor, synchronization of the rotor speed, and balance distribution of loads between the main motor and the subordinate motor have been implemented by the fuzzy logic algorithm. The closed-loop output power control of the switched reluctance wind power generator system implemented by regulating the turn-on angle of the main switches with fuzzy logic algorithm and fixed turn-off angle of the main switches is also presented. The major components of the two prototypes are explained in detail. The experimental results of the dual 7.5-kW three-phase 6/4 structure switched reluctance motors (SRMs) parallel drive system prototype are included. It is shown that the maximum difference in the output torque of the two motors at the same given rotor speeds is within 10.00% and the maximum difference in the practical rotor speed of the two motors is within 5.00%. The tested results of three-phase 12/8 structure switched reluctance variable-speed wind power generator system show that the error of the closed-loop output power control is within 2.2%, while the rotor speed range is close to the ratio of 1:3 with the low rotor speed 405 r/min. The average dc line current of the power converter can be utilized as a feedback signal for the actual output torque of SRM drive or a feedback signal for the actual output power of switched reluctance generator system.

On the Design of Power Circuit and Control Scheme for Switched Reluctance Generator

The establishment and control for a switched-reluctance generator (SRG) are presented in this paper. First, the switching behavior and the DC-link ripple characteristics of a SRG are studied. Accordingly, its circuit and control models are established. And the power circuit components are properly designed to minimize the DC-link voltage ripples caused by commutation and pulsewidth modulation switching. Second, the quantitative voltage feedback control of the SRG system considering the effects of voltage ripples is made. In this issue, a unified approach is developed to estimate the plant dynamic model parameters from measurements. Then conversely, the feedback controller is designed according to the prescribed regulation voltage control specifications. Third, a dynamic commutation shift controller (DSC) is devised to enhance the voltage control performance of a SRG. As the voltage feedback control is failed when winding current becomes single-pulse mode, the proposed DSC is actuated automatically. The turn-on and turn-off angles are dynamically and automatically shifted to assist voltage feedback regulation control. More stable and better regulation control performance can be obtained. Finally, the energy conversion efficiency improvement via static commutation shift under static operation is evaluated experimentally. Theoretical bases of the proposed control approaches are derived, and their effectiveness is demonstrated by some simulation and measured results.

固定子に永久磁石を埋め込んだ三相リラクタンスジェネレータに関する一考察

A switched reluctance generator (SRG) has desirable features including simple construction, high reliability, and low cost. Furthermore, it is suitable for use as an ultra-high-speed generator because its rotor is made of iron steel without any windings or permanent magnets. However, the SRG system is complicated, because it requires detection of the rotor position angle and excitation power for the excitation circuit of the stator winding. For this reason, it has not been used in practical applications. We previously proposed a new reluctance generator (RG) that has permanent magnets in the stator yoke. The experimental results obtained with a trial single-phase RG show that the proposed RG has very simple construction and high performance. However, the single-phase RG has the disadvantages of large leakage flux and cogging torque. In this paper, we evaluate a three-phase RG with permanent magnets buried in the stator core by simulation and experiments.

The transient self-excitation of a switched reluctance generator

Switched reluctance (SR) drive systems are a candidate technology for electric vehicle applications, particularly where a high degree of component integration is required within a thermally demanding environment—typical of engine-mounted power assist solutions. While various operation and fault scenarios have been presented for such drive systems, this paper discusses the self-excitation of a SR generator via the drive-train dc link capacitance and compounded by the stored inertial energy of the connected mechanics. Test observations are also discussed that suggest the potential for transient self-excitation of the SR generator via residual magnetization of the machine rotor, a fault scenario that has not previously been reported. The SR generator system steady-state control is discussed and results presented from a faulted system.

Closed Loop Control of Excitation Parameters for High Speed Switched-Reluctance Generators

This paper presents a new approach to the automatic control of excitation parameters for the switched-reluctance generator (SRG) where the SRG system operates at sufficiently high speed that it operates in the single pulse mode. The turn-on and turn-off angles are the two parameters through which we can control the electric power generation. The objective of the work is to develop an easily implementable control algorithm that automatically maintains the most efficient excitation angles in producing the required amount of electric power. The work is focused on finding the most efficient excitation angles and characterizing them for easy implemention under closed loop control. Through modeling of an experimental SRG and extensive simulation, it can be seen that the optimal-efficiency turn-off angles can be characterized as a function of power and speed level. Within the closed-loop power controller, the optimal-efficiency turn-off angle is determined from an analytic curve fit. The turn-on angle is then used as the degree of freedom necessary to regulate the power produced by the SRG. Given that the turn-off angle is associated with optimal-efficiency at each speed and power point, overall operation is achieved at optimal-efficiency. The SRG, inverter and control system are modeled in Simulink to demonstrate the operation of the system when implemented within a voltage regulation system. The control technique is then applied to an experimental SRG system. Experimental operation documents that the technique provides for efficient operation of the SRG system through tuning the controller at only four operating points.

Research of Reinforced Excitation Scheme for the Switched Reluctance Generator

This paper focuses on the reinforced excitation scheme for the switched reluctance generator (SRG) operating in a low-voltage and wide-speed range system. From the operational principle of SRG discussed, it can be seen that the key element to SRG generating is the reasonable and sufficient excitation. So the reinforced excitation scheme is addressed and proved by the tests of an SRG system.