Salient Permanent Magnet Generator Research Articles

Operational Analysis of an Axial and Solid Double-Pole Configuration in a Permanent Magnet Flux-Switching Generator

There are two main beneficial characteristics that doubly salient permanent magnet (PM) electrical machines present for aircraft applications: armature windings and PMs excitation sources placed on the stator side (maintenance and thermal management), and having a clear-cut rotor without PMs or excitation windings (vulnerable at high speeds due to associated centripetal mechanical stresses). Within this framework, a doubly salient permanent magnet (DSPM) generator was conceived by optimizing the stator size and rotor structure to minimize the torque ripple and maximize the root-mean-square (RMS) voltage value per turn of each generator phase. Firstly, a comparison between the 2D and 3D finite element method (FEM) models is made considering the results of 3D finite element analysis (FEA) as our benchmark in order to understand the accuracy of the 2D results against our benchmark model, the 3D one. A multi-objective design strategy based on a 2D FEA is made, it is set to have characteristics closest to optimal for a Boeing 767 turbine, that is, the necessary electromotive force for a required power of 90 kW at 3000 rpm, feeding a simplified Boeing 767 electrical power distribution system. The results show that the machine could not deliver the required power at 3000 rpm since the 2D FEA demonstrates that the 2D model gives optimistic results when compared with the 3D FEM model. However, with a 3D FEA of the machine feeding the aircraft load, it was seen that the machine’s efficiency is 92%, suggesting that this machine can be a plausible solution.

Model-Free Control for Doubly Salient Permanent Magnet-Generator-Based Tidal Stream Turbine Considering Flux-Weakening Operation

Renewable energy generation is increasingly important due to serious energy issues. A Doubly Salient Permanent Magnet Generator (DSPMG) can be an interesting candidate for tidal stream renewable energy systems. However, the special structure makes the system nonlinear and strongly coupled even after Park transformation and involves a larger torque ripple. Previous research mainly focused on model-based control for this machine, which is very sensitive to the parameters. Thus, to control the complex systems stably and accurately, two model-free control algorithms, Active Disturbance Rejection-Based Iterative Learning Control (ADRILC) and Active Disturbance Rejection Control–Iterative Learning Control (ADRC–ILC), are proposed for the current and speed control loops of a DSPMG-based Tidal Stream Turbine (TST), respectively. ADRC–ILC uses ADRC to deal with the external non-periodic speed ripple and adopts ILC to reduce the internal periodic speed ripple. ADRILC employs an iterative method to improve the ESO for the enhancement of the convergence rate of ILC. Considering the variable tidal speed, when the speed is above the rated value, Maximum Power Point Tracking (MPPT) must be changed to a power limitation strategy for limiting the generator power to the rated value and extending the system operating range. Thus, Optimal Tip Speed Ratio (OTSR)-based MPPT (for a low tidal current speed) and Leading Angle Flux-Weakening Control (LAFWC) (for a high tidal current speed) strategies are also proposed. According to the simulation results, the proposed ADRC–ILC + ADRILC has the lowest torque ripple, the highest control accuracy, as well as a good current tracking capability and strong robustness. At the rated speed, the proposed method reduces the torque ripple by more than 20% and the speed error by about 80% compared with PI control: the current difference is limited in 2A. The LAFWC proposed for an excessive tidal current speed is effective in conserving the electromagnetic power and increasing the generator speed.

Design of Doubly Salient Permanent Magnet Generator for Output Power Enhancement using Structural Modification

The doubly salient permanent magnet generator (DSPMG) is widely known as an efficient machine for electrical production from renewable energy. In this paper, we aim to improve the output power of the DSPMG using a structural modification, which is targeted for low-speed electrical generations. Structural parameters including the stator pole depth, thickness of permanent magnet, stator pole arc, and number of winding turns were adjusted, then an optimal value of those parameters was selected based on the characteristics of the generator tested during no-load and on-load conditions. Simulations were based on the finite element method. The generator was targeted to be used for the rated power of 200 W. It was found that the optimally designed generator had a higher electromotive force of 36.1%, a lower cogging torque of 20%, and a higher output power of 12.2% than the conventional structure. The leakage flux of the proposed structure was also improved from the conventional one. Thus, the generator designed in this work could be another capable choice for electrical generation from renewable energy. The proposedly modified technique can also be adapted for output profile improvement of the doubly salient permanent magnet machines which are extensively used for renewable energy production nowadays.

Design Optimization of Outer Rotor Toothed Doubly Salient Permanent Magnet Generator Using Symbiotic Organisms Search Algorithm

Wind turbine (WT) technology becomes more and more important due to the serious environmental and energy issues. The toothed poles outer rotor doubly salient permanent magnet (DSPM) generator with simple and durable design, high torque and high-power density has a great prospect in wind turbines application. The large diameter makes the construction of such a machine more convenient due to the installation of the turbine blades directly to the outer rotor generator surface. Nevertheless, the size of the generator must be increased to provide larger output power. This increases the generator’s mass. Thus, larger massive DSPM generators are undesirable in wind turbine design. In this paper, an optimization design procedure of the outer rotor doubly salient permanent magnet generator ORDSPMG is proposed for 10 kW WT application. The reduction of the generator weight is demonstrated and proofed. The considered machine version is characterized by having the same effective axial length and output torque imposed by the specifications relative to the 10 kW direct drive WT. An optimization procedure using a fast and effective method, namely the symbiotic organism search (SOS) algorithm coupled to a parametric two dimensional finite elements analysis (2D-FEA), is employed to optimize the machine parameters. The main parameters affecting the generator design are also analyzed. The results obtained reveal that the proposed generator topology presents low weight and thus high torque density among other satisfactory characteristics.

Adaptive super-twisting control of doubly salient permanent magnet generator for tidal stream turbine

Tidal Stream Turbine (TST) becomes more and more important due to the serious environmental and energy issues. Doubly Salient Permanent Magnet Generator (DSPMG), a fascinating machine with durable design, large torque, and high-power density, has a great prospect in TST. Nevertheless, the flux linkage and inductance of this machine have the same periodical variation due to the stator-Permanent Magnet (PM) structure. It not only causes the inherent torque ripple with the conventional sinusoidal current waveform but also makes the system nonlinear and strongly coupled even after the coordinate transformation. Thus, in order to control the complex systems stably and accurately, High-Order Sliding Mode Control (HOSMC) strategy based on Adaptive Super-Twisting Algorithm (ASTA) is proposed for DSPMG-based TST in this paper. Firstly, First-Order Sliding Mode Control (FOSMC) and Super-Twisting Algorithm (STA)-based HOSMC are designed respectively for the current loop in d-q coordinate system. Then, considering the difficulties of the parameters tuning timely in variable conditions, adaptive control is applied to STA-based HOSMC. The stability of this system in a finite time is proved subsequently. Eventually, according to the simulation results, ASTA-based HOSMC has the least torque ripple, highest control accuracy, and strongest robustness compared with the other controllers.

An Improvement of Output Power in Doubly Salient Permanent Magnet Generator Using Pole Configuration Adjustment

The doubly salient permanent magnet (DSPM) machines are very attractive for low-speed power generation. In this work, we propose a design technique to improve the output power of the DSPM generator by an adjustment of pole configuration. The number of stator and rotor poles, split ratio, as well as the stator pole arc of the generator, were proposedly adjusted and optimized. The output characteristics of the generator including the magnetic flux linkage, electromotive force, harmonic, cogging torque, electromagnetic torque, output voltage and output power were analyzed through finite element analysis. The symmetrical magnetic field distribution of all generators was firstly verified. Then, the results indicated that this particular generator was optimized at 18 stator poles and 12 rotor poles, while the split ratio and the stator pole arc should be set as 0.78 and 6.15 degrees, respectively. The proposed optimal generator could provide a significant improvement in the output voltage and the output power compared to the conventional structure. The output power of 1.28 kW can be reached by the optimal structure, which was two times higher than that of the conventional structure. The physical explanation regarding to the structural modification was also given. The proposed design technique can be applied for improving the output power of the DSPM machines.

Optimal Stator Design to Improve the Output Voltage of the Novel Three-Phase Doubly Salient Permanent Magnet Generator

Since in many studies it has been widely indicated that the doubly salient permanent magnet (DSPM) generator could provide a high electromotive force (EMF), this paper proposes an optimal structural design of the DSPM generator for improving the output profile of the generator. The finite element method has been performed in the simulations and analysis. The effects of stator structural parameters, including the thickness of permanent magnet (PM) and the inner stator depth, on the output characteristics of the generator have been investigated. The generator outputs including the magnetic flux-linkage, the magnetic field distribution, the EMF, and the voltage regulation have been analyzed and discussed. The results have showed that the magnetic flux-linkage and the EMF of the proposed optimal structure could be significantly improved by an optimum modification of the PM thickness and the stator depth. Then, the optimal thickness of PM and inner stator depth of this particular generator has been proposedly selected. The flux-linkage and the EMF produced by the optimal structure have been 15.88 % and 6 % improved than the one of the conventional structure. The magnetic field distribution analysis has been also carried out in order to confirm the symmetrical property of simulation results. Furthermore, the optimal structure has also provided a greater voltage regulation profile than the conventional structure. This design technique can be also utilized to improve the generator output profile of other DSPM machines.

Optimal Stator Design of Doubly Salient Permanent Magnet Generator for Enhancing the Electromagnetic Performance

An optimal stator design technique of a three-phase doubly salient permanent magnet generator (DSPMG) for improving the output power is proposed. The stator configuration was optimally designed by adjusting the stator pole depth and stator pole arc. The trapezoid outer stator tip was also designed. Then, the output characteristics of the designed DSPMG including the flux linkage, electromotive force (EMF), harmonic, cogging torque, efficiency, magnetic flux distribution and voltage regulation were characterized by using the finite element method. Results were compared to the original structure in the literature. It was found that the flux linkage, EMF, cogging torque, and efficiency of the proposed DSPMG were significantly improved after the stator pole depth and stator pole arc were suitably modified. Further details of optimal stator pole depth and stator pole arc are presented. The EMF produced by the optimal proposed structure was 47% higher than that of the conventional structure, while 56% cogging torque improvement and 20% increased efficiency were achieved. The EMF generated by the proposed structure was classified in the high-range scale compared to the other existing models. The symmetrical magnetic flux distribution of all structures was indicated. The voltage regulation of the modified structure was also significantly improved from the conventional model. The proposed design technique can be utilized to maximize the electromagnetic performance of this particular generator type.

Performance improvement of asymmetrical-pole partitioned stator permanent magnet generator by optimizing stator teeth number

The partitioned stator doubly salient permanent magnet generator (PS-DSPG) with asymmetrical-pole configuration has been widely applied for producing electrical power due to their high reliability, high flux linkage and high electromagnetic force (EMF). Therefore, we aim to improve the performance of this generator an asymmetrical-pole structure technique applied to outer stator pole. The phase flux linkage and phase EMF were characterized by finite element method. It was verified that the flux linkage and EMF were increased when increasing the number of outer stator. Especially, the 30/8/14-pole (outer stator/rotor/PM-pole) of PS-DSPG structure with asymmetrical-pole technique produced high symmetric EMF waveform. the arc variation of rotor iron piece of all proposed structures was investigated. It was found that the 30/8/14-pole of the proposed asymmetrical-pole PS-DSPG structure provides EMF about 61.29% higher than the conventional structure at expanded rotor arc of 140%. Hence, the 30/8/14-pole asymmetrical-pole PS-DSPG structure can be utilized for electrical generation in low-speed applications.

Kynurenic acid analogue SZR-72, but not SZR-73, SZR-81 and SZR-104 treatment moderates the severity of acute necrotizing pancreatitis in rats

This paper presents the impact results of the variation of the rotor and the stator tooth pitches (Vernier effect), on the waveform of the back-electromotive force (EMF) generated by the low speed Doubly Salient Permanent Magnet machine (DSPM). The rotating electrical machines with and without Vernier effect are designed and optimized using genetic algorithms combined with finite element method. The optimization of machines parameters is focused on the maximization of the mass to torque ratio. The results show that the machine with Vernier effect has better performances. The obtained Vernier slotted doubly salient permanent magnet generator is then integrated into an autonomous wind energy conversion system. Simulations tests are carried out through Matlab/Simulink. The results show that the proposed machine is a valid and inexpensive alternative for directly coupled wind turbines.

Structural Design of Partitioned Stator Doubly Salient Permanent Magnet Generator for Power Output Improvement

Partitioned stator doubly salient permanent magnet generators (PS-DSPGs) have been extensively used for electrical generation mainly due to their high reliability, high electromotive force (EMF), and high-power output. Therefore, we aim to improve the output power of a PS-DSPG by designing the optimal configuration of generator pole structure. Electrical characteristics including the magnetic flux linkage distribution, phase EMF, cogging torque, voltage regulation, and power output profile were characterized by using the finite element method. After optimizing the generator pole structure including the angle of air gap arc width, it was found that the proposed PS-DSPG with 18/15 (stator/rotor) pole structure with optimized air gap arc width could produce higher EMF of about 23.24% than a conventional structure because this structure has the suitable number of pole structures. Also, an analysis of voltage regulation and power output profiles under the loaded condition were carried out, and it was indicated that the PS-DSPG based on the suitable 18/15-pole structure could provide the best machine performance where the output power is 11.63% higher than the conventional structure. Hence, the proposed PS-DSPG with 18/15-pole structure can appropriately be utilized for electrical generation, especially in low-speed operated generator applications.

Reduction of Torque and Voltage Ripple in a Doubly Salient Permanent Magnet Generator

Large torque and voltage ripple are inherent drawbacks of doubly salient generators. This paper first introduces torque sharing function (TSF) into the application of a dual-channel three-phase 12/8 poles doubly salient permanent magnet generator (DSPMG) to reduce torque and voltage ripple. Based on the principle of copper losses minimization, a new TSF is proposed through theoretical analysis and numerical computation. The proposed TSF is compared to conventional TSFs according to three evaluation criteria. In order to achieve satisfying and consistent steady state and dynamic performances over the whole operation range, gain scheduling PI controller is adopted to overcome the highly nonlinear characteristic of the DSPMG. Besides, with compensators of back-EMF, cogging torque and losses adopted as feed-forward, a dual closed-loop generation control system is detailed designed. Both simulation and experimental results verify the effectiveness of the proposed control system and the copper losses minimization TSF in reducing torque and voltage ripple.

Improvement of power generation performance in a doubly salient permanent magnet generator with a capacitive energy recovery converter

In order to improve the power generation performance of a doubly salient permanent magnet generator (DSPMG), this study proposes a new converter called capacitive energy recovery converter (CERC), together with the corresponding control strategy. The CERC is composed of controllable devices, uncontrollable devices, and an energy storage circuit. The control strategy has been designed based on analysis of the electromagnetic characteristics of the DSPMG. With the proposed control strategy, the winding current of each phase can be controlled and increased separately, thus yielding large negative electromagnetic torque against the prime mover in a complete electric cycle. At the same time, the excitation sources are independent of the load part. As a result, power generation performance of the DSPMG with CERC is improved compared to that with a traditional three-phase full-bridge converter. A multi-objective optimisation problem is formulated to find the optimal turn-on and turn-off angles of two systems, which are used as control parameters in this comparison. Besides the lower voltage and torque ripples, the dynamic and fault-tolerant performance of the DSPMG with CERC is also superior. Both simulations and experiments have been conducted to verify the validity of the proposed converter and the control strategy.

Optimized design of doubly salient permanent magnet generator taking into account the efficiency of energy conversion

Optimized design of doubly salient permanent magnet generator taking into account the efficiency of energy conversion

Performance analysis of Vernier slotted doubly salient permanent magnet generator for wind power

This paper presents the impact results of the variation of the rotor and the stator tooth pitches (Vernier effect), on the waveform of the back-electromotive force (EMF) generated by the low speed Doubly Salient Permanent Magnet machine (DSPM). The rotating electrical machines with and without Vernier effect are designed and optimized using genetic algorithms combined with finite element method. The optimization of machines parameters is focused on the maximization of the mass to torque ratio. The results show that the machine with Vernier effect has better performances. The obtained Vernier slotted doubly salient permanent magnet generator is then integrated into an autonomous wind energy conversion system. Simulations tests are carried out through Matlab/Simulink. The results show that the proposed machine is a valid and inexpensive alternative for directly coupled wind turbines.

Modeling and Vector Control of Marine Current Energy Conversion System Based on Doubly Salient Permanent Magnet Generator

This paper provides a model and a control of a marine current energy conversion system. The modeled marine current energy conversion system is a 10-kW generating system with a low-speed doubly salient permanent magnet generator of 50rpm. First, the resource, the turbine, and a dynamic analytical model of the generator are developed. Second, due to variations of marine current speed, which may lead to strong fluctuations in the power extracted by the marine current turbine, control strategies for the marine current energy conversion system at both low and high marine current speeds are analyzed, assessed, and compared. Finally, simulations of the proposed system are carried out, modeled, and simulated on MATLAB/Simulink software.

Study on Torque Characteristic of Novel External Rotor DSPM Generator

The external rotor doubly salient permanent magnet (DSPM) generator with PM rotor tooth is designed. The two-dimensional model of the generator is analyzed by finite element method. Without changing the structure of generator, the magnet circuit is kept in the saturated state as soon as possible by paralleling capacitor besides the windings. By comparing the two kinds of rectifier topology structure, the results show that the average electromagnetic torque and the output voltage is significantly enhanced in series multiple rectifier circuit. The torque ripple of generator can be effectively suppressed in the case of load, which has a certain guiding significance for improving the output performance of the generator.