Interior Permanent Magnet Generator Research Articles

Flying‐start and continuous operation of a permanent‐magnet wind generator based on discontinuous currents, discrete second‐order sliding‐mode observer and phase‐locked loop

In wind energy conversion systems of type 4, the critical operating point in permanent-magnet generators (PMGs) is the moment of switching on the generator-side converter (GSC). The induced back-electromotive force (EMF) acting on PMG terminals can cause inrush currents if the synchronisation between PMG and GSC is not done well. The main condition for achieving a satisfying synchronisation is to know the rotor angle, rotating speed and induced back EMF before the GSC is switched on. This synchronisation together with the switching on of the GSC is called the flying start of a PMG. In this study, a novel sensorless PMG flying-start method is proposed to ensure good synchronisation. The flying-start method is based on an extended flux PMG model in a rotating reference frame with a discrete second-order sliding-mode observer and a phase-locked loop controller during the discontinuous operating mode. This is based on discontinuous currents, which are induced because of the PMG rotation caused by wind energy. The proposed method ensures the operation of PMGs in the continuous operating mode as well. The effectiveness of the proposed method is verified on saturable models of low- and high-power surface and interior PMGs through simulations in Simulink and Piecewise Linear Electrical Circuit Simulation (PLECS).

Analysis of Current Signals in a Partially Demagnetized Vector Controlled Interior Permanent Magnet Generator

Abstract This manuscript analyzes the operation of an interior permanent magnet (IPM) machine working as a permanent magnet synchronous generator (PMSG). The partial demagnetization operation is analyzed. To obtain more accurate voltages and currents of the machine, finite element analysis (FEA) is used in co-simulation with the full converter and the converter’s control algorithm. Direct field oriented control (DFOC) shows robustness by maintaining the speed even with a 25% demagnetized PMSG. Also, an analysis of the rotating reference frame DQ signals is done to asses demagnetization.

Optimization Design of a New Type of Interior Permanent Magnet Generator for Electric Vehicle Range Extender

Aiming at the disadvantages of large leakage flux and low magnetic flux density of radial magnetic circuit and tangential magnetic circuit, a new type of permanent magnet (PM) rotor with parallel tangential and radial magnetic circuits is proposed. Based on Ohm’s law and Kirchhoff’s law of magnetic circuits, equivalent magnetic circuits for rotor poles are developed. The structure parameters of the generator are preliminarily determined. At the same time, by means of the Taguchi method and employing finite element analysis, the rotor poles of generator are optimized to improve air gap magnetic density, the cogging torque, and the distortion of back-EMF waveform. Finally, the validity of proposed design methods is validated by the analytical and experimental results.

Sizing of IPM Generator for a Single Point Absorber Type Wave Energy Converter

In this paper, a wave energy converter (WEC) is designed for a wave climate condition and its interior permanent magnet (IPM) generator is dimensioned for minimum life cycle cost (LCC). The single point absorber movement is simulated and the harnessed annual energy is determined to be 325 MWh. Possible IPM generator sizes are investigated using finite element calculations. Tradeoffs between the generator cost and the annual energy efficiency is performed in order to find the best economical solution. For the economical evaluation, the net present value method is utilized in order to obtain the LCC of the electric generation system of the WEC. Increasing the axial length of the machine 1.6 times results in the lowest LCC, with a $2.5\%$ efficiency increase, which means an increment of approximately 1000 € in the investment cost. Despite the higher investment cost, the LCC of the WEC generator decreases from 8070 € to 6450 €, due to the lower losses.

Flying Start of a Permanent Magnet Wind Power Generator Based on a Discontinuous Converter Operation Mode and a Phase-Locked Loop

Flying start of a wind generator is a common requirement in wind turbine applications. This paper proposes a novel method for allowing the flying start of a permanent magnet generator (PMG). The proposed method is based on the discontinuous mode of operation of the converter and the phase-locked loop (PLL). During the discontinuous mode of operation, a series of zero-voltage pulses is applied to the generator, causing the occurrence of the short-circuit current, and thereby employing the PLL structure to estimate the rotor speed and angle. Also, a short-circuit current control structure with automatic adjustment of the reference value is proposed. The input signal to a PLL structure is adequately selected in order to enable a continuous mode of operation of the PMG. Simulation results demonstrate the applicability of the proposed method on the surface and interior PMGs, as well as on low- and high-power PMGs. The estimation accuracy does not depend on changes in the PMG parameters. The proposed method was implemented in a digital control system and experimentally verified on a 375 kW interior PMG. Experimental responses referring to the flying start of the PMG demonstrate the effectiveness of the proposed method.

Design Optimization of Interior Double-Radial Synthetic Magnetic Field Permanent Magnet Generator for Electric Vehicle

The Interior double-radial permanent magnent generator (IDRPMG) which composed by two groups of rectangular permanent magnets to provide parallel magnetic circuits of the rator and the sator core with less eddy current loss, low hormonic content and low cogging torque of the stator with fractional slot winding is developed. It has the advantages of remarkable magnetism gathering effect, strong magnetic field intensity and high space utilization. Combining Taguchi method and finite element method, the relevant parameters of the permanent magnet size and the angle between the first and second rectangle permanent magnets in rotor are optimized to get better the distortion rate of output voltage waveform, lower cogging torque and higer peak value of airgap flux density. Then finite element simulation is taken for the best optimization scheme through comparative analysis of the machine by before and after optimization. It showed that each performance index is improved after optimization. Finally, the prototype is manufactured, according to the optimization parameters and some experiments are conducted, which results verify the analys is preview well.

Flying start and sensorless control of permanent magnet wind power generator using induced voltage measurement and phase-locked loop

This paper proposes a new method for the estimation of the rotor angle of interior permanent magnet generators used in wind power applications. The proposed method provides the flying restart and the continuous operation of permanent magnet generators. The paper addresses the problem of switching on the converter (start of the pulse-width modulation) when the generator rotates and the occurrence of inrush current if the converter is not synchronized with the generator. The proposed method is based on the induced voltage measured at generator terminals before switching on the generator converter and on a phase-locked loop with a proportional-integral position controller, which ensures the decoupled sensorless control of the permanent magnet generator. The simulation results show a comparison between the performances of the proposed method and the method based on the back-EMF. The proposed method is implemented in a digital control system and verified on a laboratory model. The experimental tests carried out on a 375kW interior permanent magnet generator show the effectiveness of the proposed method.

Single-Phase Loading Behavior of the Isolated 3ph Spoke Interior Permanent-Magnet Generator

This paper examines the performance of a three-phase interior permanent-magnet generator used in a portable ac generator when directly driving isolated single-phase (1-ph) ac loads. The performance of the generator was compared under three alternative connections: 1) 1-ph star; 2) 1-ph delta; and 3) a proposed “open delta” connection. The voltage regulation, total harmonic distortion, and efficiency as three main performance criteria of the portable generators were examined using analytical calculation, finite element simulation, and experimental measurements.

A Study on a Linear Magnetic-Geared Interior Permanent Magnet Generator for Direct-Drive Wave Energy Conversion

The conventional linear permanent magnet generator (CLPMG) for direct-drive wave energy conversion (WEC) has experienced many drawbacks that are difficult to overcome such as low power density and bulky system volume. To improve power density, this paper proposes a linear magnetic-geared interior permanent magnet generator (LMGIPMG) with tubular topology, which artfully incorporates a linear magnetic gear into a linear permanent magnet generator. The operating principle of the LMGIPMG is introduced, and a detailed analysis of air gap flux density, thrust force characteristics, and no-load and load performances are presented and discussed by using finite element method. The CLPMG, which produces the same power as the LMGIPMG, has about four times the volume of the latter. A prototype CLPMG is manufactured to verify simulation results against experimental tests. The design method and the operation conditions of LMGIPMG and CLPMG are both consistent; thus, the performance of LMGIPMG meets the operation requirements of the direct-drive WEC.

Energy Efficiency of SR and IPM Generators for Hybrid Electric Vehicle

A new switched reluctance (SR) generator was designed for possible application in hybrid electric vehicles. The proposed generator was designed to be mostly competitive with the target interior permanent-magnet (IPM) generator currently used in mass-produced hybrid vehicles. The energy efficiencies of the SR and IPM generators were compared in typical driving cycles, such as US06, HWFET, and UDDS modes. We found that the energy efficiency of the SR generator was close to the IPM generator in high-speed driving cycles because the SR generator has no iron loss during the generator idling period due to the fact that it has no PM.

Effect of Multilayer Windings on Rotor Losses of Interior Permanent Magnet Generator With Fractional-Slot Concentrated-Windings

Recently, the interior permanent magnet (IPM) machines have become a promising candidate for more and more applications, for their nice performances-wide speed range, considerable power density, and several other advantages. However, there are still some obstacles to overcome to improve the performances of the IPM machines with fractional-slot concentrated-winding (FSCW). Among which, the rotor losses, due to the large amounts of the magnetomotive force harmonics produced by FSCW, is a big threat to safe operation. In this paper, the effect of multilayer windings on rotor losses, especially the eddy-current losses in the permanent magnets of IPM machines with FSCW, is mainly investigated using the 2-D finite element analysis. Side effects on torque performances is also studied and compared with the double-layer windings.

Stand-Alone Pico-Hydro Generation System using a High-Efficiency IPM Synchronous Generator

Abstract – This paper presents a successful stand-alone pico-hydro generation system using a high-efficiency interior permanent-magnet (IPM) synchronous generator. A 1-kW 4-pole V-type IPM generator with low voltage regulation is used for laboratory test in stand-alone hydro energy conversion system. It has been found from experimental results that the constant output voltage is supplied stably by the proposed system under wide speed range. Keywords : Hydro g eneration system, IPM generator, Automatic voltage regulation 1. Introduction Recently, global warming has become an important problem. In Japan, there has been a power-shortage problem because of the shutdown of the nuclear power reaction by the Great East Japan Earthquake on March 11, 2011. In such situation, the territorially distributed energy generation using wind or water power attracts attention. The development of permanent-magnet (PM) synchronous generators has progressed rapidly due in part to emergence of the high energy rare-earth magnets like neodymium-iron-boron (Nd-Fe-B) and many designs of PM rotors have been presented in recent years [1]-[6]. However, rare-earth materials such as neodymium and dysprosium are expensive and depend on China for 90% or more of the world share [7]. Therefore, the research for the substitution of Nd-Fe-B to Ferrite magnets has been reported [8]. However, it is considered that the downsizing of the generator needs the high energy rare-earth magnets in stand-alone small power generation system still now. Small wind or water power generation systems have been presented in recent years, for example, [9]-[12]. This paper presents a successful automatic voltage regulation of high-efficiency IPM synchronous generators for stand-alone pico-hydro power generation system. A 1-kW 4-pole V-type IPM generator with low voltage regulation [13] is used for laboratory test in hydro energy conversion system.

Finite Element Analysis on Magnetic Flux Leakage of Interior Permanent Magnet Generator for Vehicle

In order to solve the problem that no-load magnetic flux leakage coefficient is not accurate when it is calculated by the method of magnetic circuit, a model of interior permanent magnet(IPM) generator with 36 slots for vehicle was built through the finite element method of the ANSYS, and then a means of calculating the IPM generator’s magnetic flux was put forward after analyzing the magnetic flux leakage conditions of different rotor structures under the circumstance of not changing stator structure. The ralationships among the pairs of poles, the magnet width, the thickness of non-magnetic sleeve, the length of air-gap and the magnetic flux leakage coefficient were obtained, and they provided forceful guidance for the structural design of IPM generator.

Steady-state performance analysis and modelling of directly driven interior permanent magnet wind generators

This study presents a systematic approach for modelling, analysing and evaluating steady-state performances of directly driven interior permanent magnet generators (IPMG) for wind energy conversion systems. The proposed approach for modelling and analysing the performance of PMGs is based on relating the harmonic components present in the stator currents to the harmonic components present in the terminal voltages. Three laboratory IPMG of 1, 5 and 50 kW are tested at different shaft speeds for supplying a resistive load, a rectifier and a resistive load and rectifier inverter with a resistive load. Experimental performances of the tested IPMGs demonstrate direct relationships between terminal voltage harmonic components and harmonic components present in stator currents. Also, investigated experimental performances show significant impacts of stator currents harmonic components on the IPMG efficiency.

Design and comparison of a novel stator interior permanent magnet generator for direct-drive wind turbines

A novel stator interior permanent magnet generator (SIPMG) is presented. A modular stator design is used for convenience in manufacture and maintenance. The generator has the advantages of rugged rotor and concentrated winding design whereas the torque ripple is smaller than that produced by a doubly salient machine. Several low-speed multi-pole SIPMGs are designed for direct-drive wind turbines with ratings from 3 to 10 MW. Comparisons between the SIPMG and rotor-surface-mounted permanent magnet synchronous generator (PMSG) show that the SIPMGs have about 120% torque density and 78% cost per kilowatt compared with the PMSG.

埋込型永久磁石発電機の電圧変動特性

Permanent-magnet generators can be very efficient, do not require excition. However, the voltage regulation of Permanent-magnet generators became large in their over load conditions, because the magnet field cannot be controlled. It is preferable that the voltage regulation factor of generators has a small numerical value. In this paper, I discuss the voltage regulation of IPM (Interior Permanent-Magnet) generator.The IPM generator has two-layers of the permanent-magnet embedded in the rotor. The voltage regulation performances of the IPM generator are calculated using extended to cover the effect of various parameters on the voltage regulation performances. Experimental results of the IPM generators which confirm the analyses are also given. In this experimental result, the voltage regulation factor is 1.5% at the resistive load.