Permanent Magnet Wind Power Generator Research Articles

Simulation analysis of overvoltage caused by grounded short circuit in the collection system of far-offshore wind farms

Abstract As the distance from the shore of offshore wind farms increases, MMC-HVDC technology is gradually gaining attention in its grid connection schemes. A broadband electromagnetic transient model of offshore wind farms with a total capacity of 800 MW connected to the grid via a flexible direct current transmission system is developed. After three types of grounded short circuit faults occur at different fault positions within the power collection system, the characteristics of overvoltage are obtained and they are analyzed on the basis of considering the low voltage ride-through capability of the direct-drive permanent magnet wind power generator. Combining the two factors of range and amplitude, the results show that the overvoltage phenomenon is the most serious when a two-phase grounded short circuit occurs at the converging busbar, which can be the focus of the study when setting up overvoltage protection.

Improved Maximum Power Point Tracking Control for D-PMSG Systems: Fuzzy Gradient Step Approach

Improved Maximum Power Point Tracking Control for D-PMSG Systems: Fuzzy Gradient Step Approach

Analytical modeling for rotor eccentricity solution in wind power generator with bread loaf PMs

This paper presents a novel analytical solution for the magnetic fields of large permanent magnet (PM) wind generator with bread loaf PMs under normal and eccentricity conditions. To simplify the calculation, the generator is first approximately modeled in the Cartesian coordinate, and then the bread loaf PMs are equivalently considered by pairs of coils so that their effects can be expressed by mathematic equations. By applying the Fourier separation method, with the boundary and interface conditions, the magnetic fields in the calculation regions can be obtained by solving system equations. Afterward, the rotor eccentricity is investigated by transforming the corresponding model to a new orthogonal coordinate system by using a conformal mapping technique. Numerical examples validate the proposed method and the calculated results have a satisfactory agreement with the finite element analysis. The established model in this paper has a significant value for modeling large PM wind power generators, and the calculation time is deduced remarkably.

An Enhanced Half-Quasi-Z-Source Inverter for Wind Energy Conversion System with D-PMSG

To solve the problem of the traditional quasi-Z-source inverters with low voltage gain, an enhanced half-quasi-Z-source inverter (E-HQZSI) is proposed and applied to direct-drive permanent-magnet wind power generation systems in this paper. The expression of the boosting factor is deduced, which shows that E-HQZSI has higher voltage gain compared with the QZSI and HQZSI. However, the higher voltage gain of the E-HQZSI will lead to the large distortion of the generator stator current necessarily. In this paper, a periodic shoot-through duty ratio control scheme is proposed to reduce the stator current harmonics for E-HQZSI. According to the change rule of the single-phase stator current, the shoot-through duty ratio is compromised to make that the three-phase stator currents are as close as possible to the sine wave. Finally, the correctness of the theoretical analysis is verified by simulation and experiment.

RETRACTED ARTICLE: Research on subsynchronous oscillation characteristics and suppression strategy of AC network with wind power base

When the wind farm is connected to the power system, certain issues, such as SSO, will be caused, rendering the protection of the power grid unstable. Researchers have found that this situation can be effectively avoided by direct-drive permanent magnet wind power generation. Generates synchronous frequency oscillation is with the help of a grid connection without series compensation. This mode of power generation is part of a new method of subsynchronous oscillation of the wind farm, and the concepts and steps are not explicit. From the point of view of theory, this paper analyzes the causes of its effect, as well as the methods and measures used, and lists the study reports and findings on the synchronous oscillation of grid-connected direct-driven wind farms at home and abroad. At the end of the article, the author also put forward the hypothesis and the imagination of this process. The theory of the wind fire bundling DC transmission system is that the equipment and AC current will communicate, and synchronous electrical oscillation will also occur, and the torsional vibration of the thermal power unit will occur. Our study starts from the investigation of the and explaining the theory behind the wind power and AC network. In combination with the power grid parameter data, the oscillation times of subsynchronous current harmonics in the wind farm are obtained in a specific environment and the conditions of the subsynchronous harmonic generation are analyzed. At the same time, the effect of line harmonic impedance and current oscillation frequency is also simulated.

Comparative Analysis of Permanent Magnet Synchronous Generators with Mechanical Energy Storage according to Machine Types

This paper deals with the comparative investigation on the performance of various permanent magnet wind power generators according to magnetization patterns and stator coil winding typ ...

Influence of Coil Location and Current Angle in Permanent Magnet Wind Power Generators With High-Temperature Superconducting Armature Windings

In this article, the operating current and torque of surface-mounted permanent magnet (SPM) wind power generators with high-temperature superconducting (HTS) armature windings are analyzed. The influence of coil location and current angle on the electromagnetic performance is investigated systematically. The results show that the location of the HTS coils significantly affects the operating current and torque. Furthermore, the maximum torque current angle of SPM wind power generators with HTS armature windings can be different from 180° due to the interaction between the armature and magnet fields. A design optimization method for wind power generators with HTS armature windings is developed in this article. The optimal design is then identified with consideration of the coupling influence of coil location and current angle.

DC Side Bus Voltage Control of Wind Power Grid-Connected Inverter Based on Second-Order Linear Active Disturbance Rejection Control

In order to improve the dynamic response speed and the steady-state performance of the DC side bus voltage of the wind power grid-connected inverter, a mathematical model of a typical three-phase voltage type PWM (Pulse Width Modulation, PWM) grid-connected inverter was established, and its traditional voltage-current double closed loop with proportional-integral control method was analyzed. Then a second-order linear active disturbance rejection controller that does not depend on system model information was designed to replace the traditional voltage outer loop proportional-integral controller, thus a new double closed-loop control structure was formed to control it. The frequency domain theory was used to analyze the convergence of the third-order linear extended state observer and the influence of the total disturbance on the performance of the third-order linear extended state observer. The parameter tuning scheme of the designed controller was given. Finally, the 1.5 MW direct-driven permanent magnet wind power generation system was built in the Matlab/Simulink software and the control effects of the two control modes under different working conditions are compared. The simulation results show that the control scheme designed in this paper is superior to the traditional proportional-integral controller which has good anti-interference characteristics and robustness. Especially it has a good stability effect on DC side bus voltage fluctuations.

Effect of Frequency on Arc Motion in Multiple Parallel Contacts’ System

The air circuit breaker (ACB) is required to switch off the short current at various frequencies in the permanent magnet wind power generation system. The movable contact of ACB consists of multiple parallel contacts, and the arc will be ignited when the short-circuit current appears. This paper focuses on the effect of frequency on arc motion in multiple parallel contacts' system. A 3-D magnetohydrodynamic (MHD) model of a multiple parallel contacts' structure is built. In this model, the anode consists of five parallel contacts. The difference in voltage between the near-anode layer and the near-cathode layer is considered. The nonlinear B-H curve of the splitter plate is taken into account. The time-varying electromagnetic field induced by the current loop including electrodes and arc column is calculated. The arc evolution process and effect of frequency on arc motion in multiple parallel contacts' system are analyzed by the arc voltage and the current density distribution. This paper is expected to provide the theoretical references for the optimal design of arc quenching chamber of ACBs.

Numerical Study of Influence of Frequency and Eddy Currents on Arc Motion in Low-Voltage Circuit Breaker

The air circuit breaker used for permanent magnet wind power generation systems should switch OFF the short-circuit current of variable frequencies. This paper focuses on the influence of frequency on the behavior of air arc. A 3-D magnetohydrodynamic (MHD) model of air arc plasma was developed to investigate the arc motion process at variable frequencies. In this model, the eddy currents in the whole calculation domains including the electrodes, the splitter plate, and the arc column were considered, and the magnetic vector potential approach was adopted to calculate the electromagnetic field produced by the current loop. A thin layer of elements with a nonlinear voltage–current density characteristic surrounding the splitter plate was employed to represent the formation of new arc roots and electrodes voltage drop. Based on this model, the evolutions of arc voltage, temperature, normalized time, and current density were obtained and compared among variable frequencies. The simulation results reveal that the normalized time, the eddy current density peak in splitter plate, and the arc voltage peak increase at a higher frequency.

Radially-Magnetized Transverse Flux Permanent Magnet Generator

The transverse flux permanent magnet motor attracts wide attention in the field of low-speed direct-drive wind power due to its high torque density, good low-speed performance and other advantages. Aiming at the problem of high leakage coefficient of permanent magnet in the attached transverse flux permanent magnet wind power generator, a radially-magnetized transverse flux permanent magnet generator (RM-TFPMG) is proposed in this paper. Details of the structure and principle of the proposed machine are introduced firstly, and then the main parameters of the RM-TFPMG are calculated by the magnetic circuit method. Finally, the three-dimensional finite element analysis of the radial load flux transverse flux permanent magnet generator is carried out by ANSYS Maxwell software, and the parameters of machine and Back Electromotive Force (EMF) are obtained under the condition of no-load, and the rationality of the designed motor is verified.

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.

Fuzzy based Controller for rectifiers of a Direct-Drive Permanent-Magnet Wind Power Generator

Fuzzy based Controller for rectifiers of a Direct-Drive Permanent-Magnet Wind Power Generator

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.

Effect of pole number and slot number on performance of dual rotor permanent magnet wind power generator using ferrite magnets

Dual rotor permanent magnet (DRPM) wind power generator using ferrite magnets has the advantages of low cost, high efficiency, and high torque density. How to further improve the performance and reduce the cost of the machine by proper choice of pole number and slot number is an important problem to be solved when performing preliminarily design a DRPM wind generator. This paper presents a comprehensive performance comparison of a DRPM wind generator using ferrite magnets with different slot and pole number combinations. The main winding factors are calculated by means of the star of slots. Under the same machine volume and ferrite consumption, the flux linkage, back-electromotive force (EMF), cogging torque, output torque, torque pulsation, and losses are investigated and compared using finite element analysis (FEA). The results show that the slot and pole number combinations have an important impact on the generator properties.

Research on Short-Circuit Current of Wind Power System and its Impact on Relay Protection

Wind energy is clean and renewable energy with rich resources. As one of the most promising green energy, wind power has become an important part of the electricity supply. But there are still many technical problems to be solved related to wind power generation and integration, because it may have significant impact on safe and stable operation of the power grid. Therefore, the doubly-fed wind generator and direct-driven permanent-magnet wind power generator are studied. Their models are built in PSCAD/EMTDC for electromagnetic transient simulation, in order to study the characteristics of their short circuit fault current, as well as the impact on the relay protection of the wind power system. The research outcomes provide a reference and basis to wind power failure characteristics research.

A feasibility study on a new brushless and gearless contra-rotating permanent magnet wind power generator

In this paper, a novel fully integrated contra-rotating permanent magnet (PM) generator is proposed. In order to efficiently capture wind energy, two contra-rotating rotors are integrated, based on magnetic field modulating principle, into a single PM machine. A relatively high angular velocity is created and the torque density is improved. The steady-state and transient performance of the machine is simulated using time-stepping finite-element method. The computation results are used to showcase the validity of the proposed machine design.

Characteristic Analysis of Grid-Connected PM Wind Power Generators based on Transfer Relations and Performance Evaluation

For the comparative investigation on direct-drive permanent magnet (PM) wind power generators, this paper presents the analytical approach based on transfer relations. Considering various generator types, this paper provides analytical solutions for those generators' characteristic prediction, and the analyzed results are verified. In addition, since our analysis models are designed to be connected to a grid, the power loss characteristics according to grid output power variation are presented considering harmonics in generator current caused by the grid-connected power converter.

Direct Drive Permanent Magnet Synchronous Wind Generator Maximum Power Tracking Control

Direct drive permanent magnet synchronous generator have the advantages of direct drive, simple structure, high efficiency and so on, in which make it become one of mainstream models within MW wind turbine presently. Making the direct drive permanent magnet wind power generation system as the main research object, based on the principle of the operating characteristics of direct drive permanent magnet synchronous wind generator ( DDPMG ), establish mathematical model of the whole system including wind velocity, wind turbine, direct drive permanent magnet synchronous generator and machine side converter, Appling the method of stator flux orientation to make the study of vector control strategy, to build the simulation model of direct drive permanent magnet synchronous generator system with Matlab and simulate when wind speed changes by step, the results validate the reasonableness of the model and the correctness and feasibility of the control strategy.

Control of Parallel Multirectifiers for a Direct-Drive Permanent-Magnet Wind Power Generator

This paper presents control strategies for a multimegawatt direct-drive permanent-magnet wind power generator with parallel-operating rectifiers linked by common dc bus. A model of a number of n rectifiers in parallel with a common dc link and zero-sequence current dynamics are derived and analyzed. The parallel-operating control is designed to restrain currents that flow between the power modules caused by power-device discrepancy and asynchronous operation of the parallel units. The multiple sets of pulse width modulation driving signals are generated by individual current control and produced by carrier phase-shifting synchronously. Each converter module is independent of each other identifying the rotor position by using an observer. The currents of each module are balanced and synchronized with respect to each other producing the optimal total generator torque. The experimental results that were obtained on a 1.5-MW platform proved the effectiveness of the control strategies.