Permanent Magnet Linear Synchronous Generator Research Articles

Modeling dynamic power generation from ocean waves in the Kingdom of Tonga: A comprehensive analysis using integrated mechanical and electrical framework

Globally, ocean wave energy can significantly reduce carbon dioxide emissions from the electricity generation sector. Wave energy converters (WECs) could be installed in the Kingdom of Tonga, which is surrounded by ocean, where the average wave energy flux is greater than 7 kW/m. There is a lack of feasibility studies in this area due to the unavailability of measured data on wave parameters and properties; hence, the potential of WEC is yet to be discovered or exploited. This study proposes an integrated mechanical and electrical modeling framework to analyze the impact of wave characteristics on dynamic power generation in three main islands of Tonga, including ‘Eua, Tongatapu, and Niuafo’ou. The mechanical simulation involves using a 2D Fourier wave model to identify the important factors that affect the power potential of ocean waves, such as wave height and period. The wave model is linked to a comprehensive electrical simulation model developed in Matlab Simulink, which includes a permanent magnet linear synchronous generator (PMLSG), rectifier, buck converter, inverter, and load to estimate the electrical power potential per 1 m2 of ocean area. According to the findings, in ‘Eua, the maximum annual generation intensity output is 90.45 kWh/m2, whereas in Niuafo'ou, the minimum is 48.5 kWh/m2. Applying this to a region (12.57 m2) where a WEC has been deployed in Australia, the highest yearly electricity generation in ‘Eua ranges between 926.41 and 1136.96 kWh/y, but in Tongatapu and Niuafo'ou, it ranges between around 610 and 899 kWh/y.

Nonlinear Optimal Control for a PMLSG-VSC Wave Energy Conversion Unit

This article aims to treat the nonlinear control problem for the complex dynamics of a wave energy unit (WEC) that consists of a Permanent Magnet Linear Synchronous Generator (PMLSG) and a Voltage Source Converter (VSC). The article has developed a globally stable nonlinear optimal control method for this wave power generation unit. The new method avoids complicated state-space model transformations and minimizes the energy dispersion by the control loop. A novel nonlinear optimal control method is proposed for the dynamic model of a wave energy conversion system, which includes a Permanent Magnet Linear Synchronous Generator (PMLSG) serially connected with an AC/DC three-phase voltage source converter (VSC). The dynamic model of this renewable energy system is formulated and differential flatness properties are proven about it. To apply the proposed nonlinear optimal control, the state-space model of the PMLSG-VSC wave energy conversion unit undergoes an approximate linearization process at each sampling instance. The linearization procedure relies on a first-order Taylor-series expansion and involves the computation of the system’s Jacobian matrices. It takes place at each sampling interval around a temporary operating point, which is defined by the present value of the wave energy conversion unit’s state vector and by the last sampled value of the control inputs vector. An H-infinity feedback controller is designed for the linearized model of the wave energy conversion unit. To compute the feedback gains of this controller, an algebraic Riccati equation is repetitively solved at each time step of the control algorithm. The global stability properties of the control scheme are proven through Lyapunov analysis.

Modeling and optimal operation of hybrid wave energy and PV system feeding supercharging stations based on golden jackal optimal control strategy

This paper provides a novel application for the Archimedes wave swing (AWS) device that converts the sea waves into electrical energy using a linear permanent magnet synchronous generator (LPMSG), which is connected to a rectifier that extracts the most significant energy from sea waves and reduces the stator losses. The generator's power combined with a photovoltaic (PV) system provides a total of 250 kW, sufficient for feeding a V3 Tesla Supercharging system, which is currently the latest and most advanced electric vehicle (EV) charging technology. The hybrid system is connected to a DC link, its voltage is stabilized using a supercapacitor energy storage system, and the output is provided to a buck converter that reduces the voltage for the Tesla Supercharger. The control system comprises seven proportional-integral (PI) controllers with four anti-wind back-calculation coefficients to improve transient stability. The PI gains are optimized using the Golden Jackal Optimization Algorithm (GJOA), and the system stability is evaluated by applying different disturbances like a sudden variation in the DC load, temporary DC short circuit, and connection of the EV in various modes such as a grid to vehicle and vehicle to grid modes. The results obtained by the GJOA are compared with the Particle Swarm Optimization and the hybrid Augmented Grey Wolf Optimizer and Cuckoo Search algorithms. Finally, hybrid renewable energy systems can efficiently be employed in EV supercharging stations as validated with the strategy proposed in this work.

Improved direct model predictive control for variable magnitude variable frequency wave energy converter connected to constant power load

Archimedes wave swing (AWS) is the first direct-drive wave energy converter (WEC). The AWS is coupled to a linear permanent magnet synchronous generator (LPMSG) and generates a variable magnitude, variable frequency voltage. This paper presents an improved version of direct model predictive control (DMPC) which called improved DMPC (I-DMPC) for a hybrid system containing WEC, supercapacitor (SC) energy storage system (ESS), and constant power load (CPL). This method is implemented based on discrete incremental model of generator and modified objective function, therefor steady-state error is reduced. Simulation results in the MATLAB/SIMULINK environment show the proposed control can maintain stability of the system under different CPL demand and systems faults and improve robustness and fault-tolerant capability of the system in regular and irregular waves. The Comparing results with the conventional DMPC indicate, that by using I-DMPC, d-axis and q-axis errors under regular wave can be reduced 37.5% and 50%, respectively. Also, under irregular wave, I-DMPC reduce the peak of q-axis errors from 73A to 1.5 A when loss of one leg occurred.

파력발전시스템의 간이 설계를 통한 파력발전용 리니어 발전기 설계에 관한 연구

In this paper, the design of linear generator for wave energy conversion is studied through wave energy system design. The wave energy system is designed through the mass and spring system. In the designed wave energy system, the specification of permanent magnet linear synchronous generator (PMLSG) is obtained using the principle of energy conversion. The basic design of PMLSG is performed considering the constraint of wave energy system considering the resistance load using the external circuit. Furthermore, the detent force of PMLSG is optimized using the parametric analysis. As a result, the PMLSG is designed considering the design of the wave energy system and optimization of the detent force.

Multi-Physical Coupling Field of a Permanent Magnet Linear Synchronous Generator for Wave Energy Conversion

Permanent Magnet Linear Synchronous Generators (PMLSG) has high power density and high efficiency, which is always employed in industrial application field. However, as temperature increases, it is easy to cause demagnetization of the permanent magnet, and the applications of PMLSG is limited. In this paper, a PMLSG is optimized which is used in a low speed power generation system. Firstly, a multi-physical coupling field system is described, and introduced the main factors which affecting the design of the PMLSM. Secondly, a multi-physics optimization method based on Genetic Algorithm (GA) is to improve the power density and efficiency. At the same time reduce the material cost of the generator. The thermal model is established and analysis the losses of PMLSG. The conductive heat transfer coefficient is calculated. Then, a Finite Element Analysis (FEA) model is established, and the electromagnetic properties of PMLSG were analyzed. The results of the electromagnetic field calculation are imported into the transient thermal analysis model by FEA, and the temperature of each part for PMLSG are calculated. Finally, an experimental test platform is built for verifying the correctness of the analysis.

Experimentally Verifying the Generation Characteristics of a Double-Sided Linear Permanent Magnet Synchronous Generator for Ocean Wave Energy Conversion

This paper presents an evaluation system to experimentally verify the performance of a double-sided linear permanent magnet synchronous generator (PMSG) prototype. In general, research on wave power generation systems has concentrated on the optimum design technology of PMSGs, power generation performance analysis technology, loss analysis, and performance evaluation technology. Despite active research in this field, the performance of a system wherein a wave generator and buoy are linked has never been evaluated. Therefore, in this study, a linear PMSG was used in a performance evaluation system to predict a buoy's motion and derive the parameters for optimal power generation under regular and irregular wave conditions.

Magnetic field‐modulated linear permanent‐magnet generator for direct‐drive wave energy conversion

The linear permanent-magnet synchronous generator (LPMSG) for direct-drive wave energy conversion (WEC) suffers from many drawbacks that have not yet been overcome, such as a low power density and a bulky system volume. Therefore, a magnetic field-modulated linear permanent-magnet generator (FMLPMG) with a simple structure has been designed and manufactured. First, the operating principle of the FMLPMG is demonstrated by the equivalent magnetic circuit method, which explains the high power density of the FMLPMG. Second, at a constant speed and a sinusoidal speed, the electromagnetic characteristics of the FMLPMG under the no-load and load conditions are analysed by the finite-element method. Finally, a direct-drive WEC test platform is built to simulate the process of wave action on the FMLPMG. No-load and load experiments of the FMLPMG are conducted on the test platform, and the results are compared with those of an LPMSG with the same volume and operating conditions. The results show that the FMLPMG with a high power density converts wave energy effectively and solves the problem of low power density faced by the LPMSG in direct-drive WEC.

High‐performance control for a permanent‐magnet linear synchronous generator using state feedback control scheme plus grey wolf optimisation

This study proposes an optimal control scheme for a permanent-magnet linear synchronous generator (PMLSG) using the state feedback control (SFC) method plus the grey wolf optimisation (GWO) algorithm. First, A novel state-space model of linear PMLSG is established in order to obtain desired dynamics and enough power when used for the smooth wave energy. Second, the GWO algorithm is adopted to acquire weighting matrices Q and R in the process of optimising linear quadratic regulator (LQR). What is more, a penalty term is brought into the fitness index to reduce the overstrike of output voltage and keep the rate of work more stable. Finally, optimal LQR-based SFC with and without penalty term and proportional-integral (PI) controllers are compared both in simulations and in experiments. Results clearly prove that the proposed optimal control strategy performs a better response when compared to other strategies.

Transient Stability Augmentation of a Wave Energy Conversion System Using a Water Cycle Algorithm-Based Multiobjective Optimal Control Strategy

This paper introduces a novel optimum design of the proportional–integral (PI) controller in the power converter circuits using the water cycle algorithm (WCA) to augment the transient stability of a grid-connected wave energy conversion (WEC) system. The proposed system relies on the Archimedes wave swing device, which is coupled with a linear permanent magnet synchronous generator (LPMSG). The WEC system is interfaced with the power grid via a generator-side converter (GSC) and a grid-side inverter (GSI). The GSC is used to control both of the d -axis and q -axis current of the LPMSG to minimize its power losses and extract its maximum real power, respectively. The GSI is implemented to control the terminal voltage at the point of common coupling and the dc-link voltage through a complete vector control scheme. The proposed optimal WCA-based PI control strategy is applied to both converters. The optimization process depends on the simulation-based optimization approach. In the proposed approach, the criterion of integral squared error is chosen as a multiobjective function. To validate the proposed WEC system model, the simulation results are compared with the practical results, and their error reaches less than 1%. The effectiveness of the proposed WCA-based PI control strategy is tested and compared with that obtained using the genetic-algorithm-based PI control scheme under symmetrical and unsymmetrical grid fault conditions taking into account a successful and unsuccessful reclosure of circuit breakers. The validity of the proposed control strategy is extensively checked based on simulation studies in the PSCAD/EMTDC environment.

Characteristic Analysis and Experimental Verification for a Double-Sided Permanent Magnet Linear Synchronous Generator According to Magnetization Array

This paper compares the characteristics of a double-sided small-scale permanent magnet linear synchronous generator (PMLSG) using three different magnetization arrays. Though PMLSGs generally prefer a parallel array, we propose the Halbach array and an axial array, which are widely used in permanent magnet devices. For an accurate comparison, the output power, mechanical air-gap thickness, and overall size are all equal. On the basis of analytical two-dimensional field solutions, this study predicts magnetic fields, losses, masses, and output powers of the three arrays. The experimental results are validated extensively by comparing them with finite element analysis results. This result shows the best arrangement of a double-sided small-scale PMLSG compared to the experimental results.

Core Loss Analysis of Permanent Magnet Synchronous Generator With Slotless Stator

This paper proposes an analysis method of the core loss for a slotless type permanent magnet linear synchronous generator. Core loss is usually calculated using the Steinmetz equation, but this cannot be interpreted correctly. Consequently, several researchers have proposed modified versions of this equation. In this study, we calculate core loss coefficients from the Epstein test data using a curve fitting method for accurate core loss analysis. Moreover, owing to the time harmonics observed with changes in the magnetic flux density, we separate the rotating magnetic field and alternating magnetic field in our calculations. In addition, we consider the magnetic flux leakage as a parameter. Finally, core loss of the slotless type linear generator is calculated using a modified Steinmetz equation that considers the flux leakage.

Core Loss Analysis of Permanent Magnet Linear Synchronous Generator Considering the 3-D Flux Path

This paper presents an analysis of the core loss observed in the stator of a permanent magnet linear synchronous generator. Core loss is usually calculated using the classical Steinmetz equation, but it leads to erroneous results. Consequently, several researchers have proposed modified versions of this equation, taking into account the hysteresis loss, eddy current loss, and excess loss. In this paper, we calculated all loss coefficients from the Epstein test data using a curve fitting method. Moreover, we separated the rotating and alternating fields based on the time harmonics observed with changes in the magnetic flux density. In addition, we considered the 2-D and 3-D plane flux paths that cause magnetic flux leakage. Finally, the core loss of the linear machine was calculated using a modified Steinmetz equation that considers the flux path.

Analysis of Eddy Current Loss in Permanent Magnet Linear Synchronous Generator Considering Tapped Holes in Movers Using Semi-3-D Analytical Method

This paper describes the analysis of the eddy current loss of a double-sided cored slotless-type permanent magnet linear synchronous generator considering tapped holes in mover magnets using the space harmonic method. To calculate the eddy current, an analytical solution was derived by applying the Maxwell’s equation, magnetic vector potential, and Faraday’s law in a 2-D Cartesian coordinate system. Based on the armature reaction field distribution produced by the armature winding current, we obtained an analytical solution for the eddy current density distribution. Then, an analytical solution for eddy current loss induced in a permanent magnet (PM) was derived using the equivalent electrical resistance calculated from the PM’s volume and eddy current density distribution solution. Finally, the resulting current was determined based on the analysis of eddy current loss. The analytical results produced by using this application of the space harmonic method were validated extensively through comparisons with finite-element method results.

Comparative study and experiment of a double-sided permanent magnet linear synchronous generator according to magnetization pattern

This paper presents a comparison of efficiency and mover mass on a double-sided permanent magnet linear synchronous generator (PMLSG) according to its magnetization pattern. When a PMLSG has a lighter mover, it has advantages such as lower cost and other aspects regarding mechanical losses. In general, PMLSGs are used with a vertical PM pattern, but we propose a horizontal PM pattern in this paper because the horizontal PM mover does not need a back-iron for the magnetic path. Electromagnetic field analysis is especially essential when analyzing the characteristics of PMLSGs. For this type of analysis, commercial finite element analysis tools are widely used because they offer convenient user interfaces that provide very accurate analytical results. Based on two-dimensional finite element analysis, we got results for two different patterns and compared them with our experimental results. Finally, the results of this analysis and the test results obtained confirm the validity of the model and the superiority of the horizontal pattern proposed in this paper.

Eddy current loss in double-sided cored slotless type permanent magnet linear synchronous generator using analytical method

This paper describes the eddy current loss analysis of a double-sided cored slotless-type permanent magnet linear synchronous generator using the space harmonic method. To calculate the eddy current, an analytical solution was derived by applying the Maxwell equation, magnetic vector potential, and Faraday’s law in a two-dimensional (2-D) Cartesian coordinate system. Based on the armature reaction field distribution produced by the armature winding current, we obtained an analytical solution for the eddy current density distribution. Then, an analytical solution for eddy current loss induced in a permanent magnet (PM) was derived using the equivalent electrical resistance calculated from the PM’s volume and eddy current density distribution solution. Finally, the resulting current was determined based on analysis of the eddy current loss. The analytical results produced using this application of the space harmonic method were validated extensively through comparison with finite element method results.

파력에너지 변환용 양측식 슬롯티드 타입 선형 발전기의 디텐트력 저감을 위한 특성해석

This study considered the reduction of the detent force of a permanent magnet linear synchronous generator (PMLSG). The PMLSG has a relatively large magnetic air gap. Thus, a slotted type of stator structure is generally employed. Furthermore, the detent force, which is caused by energy imbalances owing to the interaction between tooth-slot structures and the permanent magnets (PMs), must be minimized for start-up operation. Therefore, in this paper, the methods of auxiliary teeth and a notch in the teeth are applied to reduce the detent force.

Magnetic Field Energy Harvesting from AC Lines for Powering Wireless Sensor Nodes in Smart Grids

This paper presents an electromagnetic energy harvesting device for capturing power from ac power lines using a miniaturized linear permanent magnet (PM) synchronous generator. The suggested device is useful to power wireless monitoring sensors in emerging smart grids. Conventional methods for energy harvesting from power lines use current transformers which structurally need to form closed magnetic paths around the lines. However, the suggested device can operate in the proximity of the lines due to using an independent PM generator. This feature facilitates installation of the device particularly in smart grids that require ample of easy-to-install and maintenance free monitoring sensors along the power lines. The proposed energy harvester uses a magnetically driven vibrating beam around the line that is attached to a linear PM synchronous generator (PMSG) including an array of small PMs with opposite polarities. This PM arrangement improves the induced voltage of the generator due to increasing the flux gradient within the linear PMSG. Experimental test results based on a cm-scale prototype show that an average power of 0.16 mW at 50 A (i.e., power density of 3.2 mW/kA) is achievable, equivalent to a 1038-mAh/2.7-V re-chargeable battery per year for a 100-A line.

Direct drive surge wave energy converter with grid integration functionality

Summary This paper addresses the design and simulation validation of a direct drive surge wave energy converter (DDSWEC) as an efficient device for harnessing marine wave energy in near-shore locations. The proposed DDSWEC is composed of a rigid rectangular plate producing linear motions in response to surge forces of ocean waves. A translator is devised to transfer the wave energy to a linear permanent magnet synchronous generator, which all together form the power take-off (PTO) system. In the proposed scheme, the mechanical simplicity of PTO system is a superior feature in reducing power losses in the wave-electric power conversion chain. Additionally, suitable mechanical degrees of freedom lead to an impressive increase in the power conversion efficiency. Besides, mathematical modeling of the mechanical and electrical systems governing DDSWEC is interrogated in depth. In addition, through a comprehensive frequency contents analysis, the capture width of DDSWEC and the device efficiency are scrutinized to validate its well performance. Because the stochastic behavior of waves induces voltages with variable frequency and magnitude, which are undesirable features for grid integration, a full-scale back-to-back converter with both generator and grid-side controls is accordingly implemented. To validate the overall performance of the proposed DDSWEC, a test system is designed in Matlab/Simulink platform by which several time-domain simulations for both the monochromatic and irregular waves are conducted. Copyright © 2015 John Wiley & Sons, Ltd.

MPPT strategy based on speed control for AWS-based wave energy conversion system

One of the attractive direct-drive wave energy conversion systems is the Archimedes Wave Swing (AWS) coupled to a Linear Permanent Magnet Synchronous Generator (LPMSG). This paper presents an integrated control strategy for the back-to-back converter interfacing the LPMSG not only to extract the maximum power from the wave, but also to ride-through the fault. The proposed maximum power tracking technique is based on speed sensorless control of the LPMSG. The unscented Kalman filter is adapted to estimate the translator velocity. The optimal velocity is obtained from the instantaneous active power at the generator terminals. Moreover, a low-voltage ride-through control is integrated to satisfy the grid-code requirements by injecting reactive current during grid disturbances. The generated active power at the fault instant is considered in determining the dynamic reactive power injection to not exceed the ratings of the grid-side converter. The superiority of the proposed strategy is the result of its ability to regulate the translator velocity that generates optimum power. Numerical simulations are conducted to evaluate the dynamic performance of the proposed integrated optimal strategy. Besides, it has been shown that the proposed methodology outdoes others by the decreased power fluctuations which leads to a reduction of the converter size.