Direct-drive Permanent Magnet Research Articles

Parameter Identification of PMSG-Based Wind Turbine Based on Sensitivity Analysis and Improved Gray Wolf Optimization

With the large-scale integration of wind power, it is essential to establish an electromagnetic transient (EMT) model of a wind turbine system. Focusing on the problem of the difficulty in obtaining the parameters of the direct-driven permanent magnet synchronous generator (PMSG) model, this manuscript proposes a method based on trajectory sensitivity analysis and improved gray wolf optimization (IGWO) for identifying the parameters of the PMSG EMT model. First, a model of a PMSG wind turbine is established on an EMT simulation platform. Then, the key parameters of the model are determined based on the sensitivity analysis. Five control parameters are selected as the key parameters for their higher sensitivity indexes. Finally, the key parameters are accurately identified, using the proposed IGWO algorithm. The final case study demonstrates that the proposed IGWO algorithm has better optimization performance compared with the GWO algorithm and particle swarm optimization (PSO) algorithm. In addition, the simulation waveforms show that the identified parameters are accurate and applicable to other operating conditions.

Optimized design and research of direct-drive permanent magnet synchronous motor for hydra pulper

This paper presents the design of a direct-drive permanent magnet synchronous motor specifi-cally tailored for the transmission of a hydra pulper, boasting a rated power of 350 kW and a rated speed of 230r/min. A finite element model of the direct-drive permanent magnet synchronous motor is established to comprehensively analyze various performance parameters, encompassing magnetic characteristics, magnetic circuitry, reverse electromotive force, and more. Employing the coercive force method in conjunction with the magnetic density method, the demagnetization propensity of the permanent magnet under extreme operating conditions is evaluated and analyzed, facilitating the rapid identification of boundary size conditions for the permanent magnet and thereby mitigating overall motor costs. Furthermore, a genetic algorithm is employed to optimize the structural parameters of the direct-drive permanent magnet synchronous motor, enhancing comprehensive performance parameters such as power, efficiency, power factor, torque ripple, among others, while ensuring the motor remains demagnetization-free.

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.

Design of direct-drive permanent magnet synchronous motor for cryogenic valve

This paper presents a novel design of a low-speed and high-torque cryogenic direct-drive PMSM. A new simplified model is proposed to address the inaccuracy of the electro-thermal coupling model of the common cryogenic PMSM design. The coupling model focuses on the influence of the winding copper loss on the resistance, which improves the accuracy of calculating the temperature distribution and resistance value. Compared with FEM, the error of the calculation results is 4.8%. A new design method is proposed to address the problem that the common low-temperature PMSM designs lead to a rise in the copper loss. Measuring the improvement of the magnet performance in low temperature, the method reduces the turns of the coil, which significantly reduces the amount of copper loss. Compared with common methods, the amount of copper loss reduces 29.5%. Furthermore, a prototype is fabricated and tested, the results of which verifies the rationality of the design.

Enhancing wind power with permanent magnet synchronous generator control strategies

AbstractDue to the substantial rise in wind power generation, the direct-drive permanent magnet synchronous generator has emerged as a leading technology for efficient variable speed operation, meeting grid demands effectively. This paper presents a comparative analysis of control strategies for permanent magnet synchronous generator based wind turbine using real variable wind speed data from a 2 MW of Tetouan wind farm in Morocco. The proposed approach is based on evaluating two primary control strategies: the adaptive fuzzy-proportional-integral controller and the conventional proportional-integral controller aimed at enhancing the wind turbine's output power. The simulation performed on MATLAB-Simulink indicates that pitch control mechanisms play a crucial role in optimizing power generation, also demonstrating its ability to achieve satisfactory performance.

Aggregation Equivalence Method for Direct-Drive Wind Farms Based on the Excitation–Response Relationship

The grid interconnections for direct-drive wind farms have triggered multiple new sub-synchronous oscillation events, which can prevent the power system from operating safely and stably. However, the excessively high order of the detailed model for large-scale wind farms with multiple direct-drive permanent magnet synchronous generators (PMSGs) connected to power systems poses a challenge when investigating small disturbance stability and instability mechanisms. This study establishes a model of the grid-connected PMSG system based on the voltage/power excitation–response relationship to describe the dynamic characteristics of the port of the PMSG, and the analysis of active and reactive response characteristics of PMSG lays the foundation for model simplification. Based on the unit model, a direct-drive wind farm aggregation equivalence method based on the excitation–response relationship is proposed. The equivalent model obtained by this method is suitable for the small disturbance stability analysis of direct-drive wind farms grid connected system, with good accuracy. The simulation verified the effectiveness of the aggregation model.

Low voltage ride through enhancement of a permanent magnet synchronous generator based wind energy conversion system in an islanded microgrid: A dynamic matrix controlled virtual DC machine

In an isolated microgrid, the wind energy conversion system based on direct-drive permanent magnet synchronous generator may experience fluctuations in the DC bus voltage due to wind variations and grid voltage drop, thereby compromising system reliability. To address this issue, the scheme of the supercapacitor energy storage system is proposed. The existing double closed-loop PID control, which cannot provide inertia support, has shortcomings such as difficult parameter setting and slow dynamic response. To solve this problem, the dynamic-matrix-control based predictive control for a virtual DC machine method is proposed. Firstly, the concept of virtual DC machine control is firstly introduced in supercapacitor energy storage system. Secondly, according to the unit step response of virtual DC machine, the prediction model of virtual DC machine is established. Finally, the desired torque increment reference of virtual DC machine is calculated by the dynamic-matrix-control controller to change the input torque reference. Hardware-in-the-loop experiment verifies the effectiveness of the proposed method: Compared with traditional double closed-loop PID control, the maximum voltage fluctuation is reduced by 67.9 % under random wind fluctuation and the inhibition effect on DC voltage surge and plunge when fault occurs in the power grid is increased by 61.4 % and 57.9 %.© 2017 Elsevier Inc. All rights reserved.

A control-oriented LPV model of large-scale offshore wind turbines for deloading operation

ABSTRACT This article develops a new control-oriented linear parameter varying (LPV) model, which is a linear state-space model with varying parameters aimed at efficiently representing large-scale offshore wind turbines (LOWTs). Firstly, the LPV model is constructed by the mechanism analysis of a 15-MW direct-drive permanent magnet wind turbine. Subseuently, based on the operational data from FAST, the parameters with unknown values in the LPV model are determined by gain scheduling and parameter estimation. Furthermore, a deloading operation for the active output power regulation of LOWTs is proposed based on coordinating the rotor over-speed control (ROC) and the pitch angle control (PAC).

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 Solution for Electromagnetic Performance Analysis of Permanent Magnet Synchronous Motor with a Parallel Magnetized Cylindrical Permanent Magnet

High-speed direct-drive permanent magnet synchronous motors (PMSMs), supported by elastic foil gas bearings, have broad applications, such as in microcompressors. However, some problems remain to be solved for the electrical performance analysis of PMSMs. For example, there is presently no related analytical model that can be used in rotor dynamics expression for this type of PMSM. This study aimed to establish theoretical models for electromagnetic force density and torque. The process involved both theoretical and experimental research. The analytic models of air gap magnetic density, electromagnetic force density, and electromagnetic performance were established for a PMSM with a parallel magnetized cylindrical permanent magnet. The analytic calculation was conducted, and the results of the analytic model were obtained. The analytical model of the electromagnetic torque and force can be applied in theoretical research on rotor dynamics. The model provides a theoretical basis and method for studying the influence of the electromagnetic load on rotor dynamics. A finite element simulation analysis of the electrical performance of the PMSM was carried out. An electrical performance experiment was conducted. The deviation between the experimental result and the theoretical value was less than 4%. This result indicated that the analytic models could be used in a dynamics analysis of compressors that are directly driven by a PMSM for application in engineering and industrial contexts.

Direct-Driven PMSG Wind Turbines: Adaptive Super Twisting Algorithm Control Approach

This paper deals with the development of a robust nonlinear control strategy for direct-driven Permanent Magnet Synchronous Generator (PMSG) wind turbines. First-Order Sliding Mode Controllers (FOSMC) are commonly used in such systems to regulate generator rotational speed and optimize power extraction; however, they encounter significant drawbacks, notably the undesirable chattering effect and the necessity for measuring additional system states, leading to increased complexity and implementation costs. In addressing these issues, an effective control technique based on an Adaptive Super-Twisting Algorithm (ASTA) has been proposed. This algorithm not only mitigates the chattering effect but also offers a more cost-effective implementation by incorporating online gains adaptation to accommodate the unpredictable nature of wind speeds. The proposed control technique has been evaluated in MATLAB/Simulink through model-in-the-loop simulations; demonstrating superior performance compared to classical FOSMC and STA controllers under various scenarios.

Enhanced Performance in PMSG-Based Wind Turbine Systems: Experimental Validation of Adaptive Backstepping Control Design

Ensuring the quality and stability of the electrical grid is of utmost importance during the phase of electrical energy production. As wind energy plays an increasingly significant role in a country’s energy composition, maintaining stability and optimal quality has emerged as a prerequisite for the generated electricity. This article aims to devise a dynamic nonlinear algorithm that can be implemented in the wind energy conversion system (WECS) featuring a direct-drive permanent magnet synchronous generator (PMSG). Notably, the adaptive backstepping control relies on the nonlinear model of the controlled system. It harnesses the principles of the Lyapunov stability theory to regulate various parameters and uphold the overall system’s stability. Employing simulation analysis through the Matlab–Simulink environment, the proposed control strategy is evaluated using a 1.5 MW wind turbine. The results showcase the robust capability of the suggested control algorithm: it effectively maintains the DC bus voltage and produces high-quality electrical energy with a total harmonic distortion (THD) below 0.38%. Moreover, the algorithm demonstrates added resilience. The practical viability of the adaptive control algorithm is validated through an experimental study on the dSPACE DS1104 prototyping platform. This study underscores the algorithm’s proficiency in achieving all control objectives under diverse wind scenarios.

A Novel Magnetic-Geared Motor Combining Magnetic Gear and SR Motor

A direct-drive permanent magnet (PM) motor and a magnetic-geared PM motor have the advantage of high torque density. Therefore, these motors are expected to be applied as in-wheel motors for electric vehicles (EVs). However, they have a problem that it is difficult to achieve the wide speed-torque characteristics required for EVs. This paper presents a novel magnetic-geared motor that consists of a flux-modulated type magnetic gear and a switched reluctance (SR) motor. In this paper, the SR motor part and the magnetic gear part are designed, and both parts are combined into a magnetic-geared motor. The proposed magnetic-geared motor has the wide speed-torque characteristic, which direct-drive PM motors or SR motors cannot achieve.

High precision control of direct-drive permanent magnet linear motor with adaptive friction compensation

To improve the control precision and stability of Direct-Drive Permanent Magnet Linear Motor (DPMLM) with frictional nonlinearity and uncertain disturbances at a low speed, an adaptive robust integral sign error control algorithm based on friction compensation of dual nonlinear observer is proposed in this study. An improved LuGre friction model is established to describe the friction phenomena of the system. The dual nonlinear observer is designed to observe the internal frictional state of the model. A parameter adaptive law is designed to perform parameter estimation of structured uncertainty. Robust integral of the sign of the error (RISE) term is designed to overcome the frictional nonlinear disturbances. The friction nonlinearity and parameter uncertainty are compensated by feedforward compensation. The bounded stability of the proposed controller is proved by Lyapunov stability theory. As suggested by the experimental results, RMSE index decreased by 10.8% and the control precision was improved effectively by the proposed control algorithm at a low speed.

Research on the design of direct-drive permanent magnet generator for hybrid UAV

As the core of the power system, the performance of the generator is crucial to the flight and operation of the drone. This paper introduces the design and research of a direct-drive permanent magnet generator for gasoline-electric hybrid UAV. A computationally efficient optimization design method was proposed, and the generator used in the 25 kg UAV was designed

Modelling and Simulation of 100 kg Hoist Operated by Permanent Magnet Direct Drive

An overhead crane, also known as an industrial crane, crane, or overhead travelling crane, is a device that lifts, lowers, and transports items horizontally. It is used to carry extremely heavy or bulky loads through the overhead area of a facility, as opposed to through aisles or on the floor. Gear box is used with purpose of reduction in speed; as a result, torque output will be increased. In place of gear box for achieving lower rpm at high torque, use of a permanent magnet direct drive (PMDD) in conjunction with a variable frequency drive (VFD) is written in this paper. Prototype of the same is designed to lift 100kg load and checked for its performance. Modelling and simulation are done in Simcentre MotorSolve for PMDD. This alternate arrangement can be used for hoisting mechanism of EOT crane which is able to give the torque of 40-65 N.m at 25-50 RPM to lift 100 kg load.

Suppression Strategy of Subsynchronous Oscillation Based on Dynamic Voltage Compensation Control for Grid-Forming D-PMSG in Weak Grid

The virtual impedance can suppress the low-frequency oscillation effectively caused by the power coupling effect for the grid-forming direct-drive permanent magnet synchronous generator (D-PMSG). However, there are few studies on the influence of virtual impedance on the subsynchronous oscillation caused by the interaction between the grid-forming D-PMSG and the weak grid. In this paper, the mechanism of virtual impedance improving the stability of virtual synchronous generator (VSG) control for the converter is revealed from the perspective of power coupling, and the influence of virtual impedance on the system stability in subsynchronous frequency range was analysed based on the sequence impedance model. The analysis results show that the virtual inductance cannot effectively improve the oscillation suppression effect, but the virtual resistance can greatly improve the damping characteristics of the system which has a good oscillation suppression effect. However, excessive increase in virtual resistance will cause power coupling oscillation, even subsynchronous oscillation, which shows limitations in subsynchronous oscillation suppression. To solve the problem, a dynamic voltage compensation control method based on active disturbance rejection control (ADRC) was proposed, and the parameters are designed by bandwidth method. The method can suppress the subsynchronous oscillation effectively in a certain frequency range under different grid strength and disturbance conditions. And it shows strong adaptability and good system robustness in weak grid. Finally, the effectiveness of the proposed oscillation suppression strategy was verified by time domain simulation.

Cooperative Primary Frequency Regulation Strategy of Wind Storage System Based on Variable Inertia Coefficient

Direct-drive permanent magnet synchronous wind turbine-generator (PMSG) is connected to the grid through the rotor side and grid side converter. The rotor speed is decoupled from the grid frequency, so PMSG output power cannot respond to the change in system frequency. However, with the gradual increase of wind power penetration, the static stability of system frequency is weakened, so the new grid-connected wind farm should have the ability of active frequency support. This paper proposes a cooperative primary frequency regulation (PFR) strategy for wind storage systems based on variable inertia coefficient. PMSG provides inertia based on the distribution of rotational kinetic energy and modifies the polarity of the inertia coefficient at the frequency recovery stage to speed up the frequency recovery. Droop control is realized by energy storage and variable power tracking control (VPPT). Energy storage and VPPT respectively suppress the frequency decrease/increase and only participate in the down/up single-side PFR, which can reduce the energy storage configuration capacity. And a safety discharge coefficient considering the state of charge (SOC) is introduced to prevent over-discharge of energy storage devices when outputting energy. Finally, the PFR capability of PMSG under the proposed control strategy is verified by simulation results.

Inertia control method of direct drive permanent magnet wind turbine under high wind power permeability

Direct-drive permanent magnet wind turbine has high power generation efficiency, especially in low wind speed environment, and is widely used for wind power generation. Direct-driven permanent magnet wind turbines show no inertia response to the system through the grid connection of full-power converters, resulting in increased frequency fluctuation, poor response effect and reduced stability time of the system under sudden load and sudden wind speed conditions. Based on this, an inertia control method of direct-drive permanent magnet wind turbine under high wind power penetration is proposed, and the model of direct-drive permanent magnet wind turbine is built by designing functional modules to improve the synchronous control effect under high wind power penetration. The vector control calculation method is used to design the virtual inertia control parameters, and the decoupling quantity is introduced to decouple the parameters with filter inductance, so as to improve the supporting capacity of power grid frequency fluctuation. The simulation results show that the proposed method has a fast frequency response under sudden load change, and it drops to the lowest value of 49.16 Hz at 12.14 s. Under the condition of sudden change of wind speed, the system frequency rises to the highest value of 50.38 Hz at 12.94 s. It is proved that the proposed method has a certain suppression effect on the amplitude of frequency change, effectively shortens the time for the system frequency to return to steady state, and thus has more advantages.

The Impact of Phase-Locked Loop (PLL) Architecture on Sub-Synchronous Control Interactions (SSCI) for Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-Based Type 4 Wind Farms

Electric vehicles (EVs) are a promising solution to reduce carbon dioxide (CO2) emissions, but this reduction depends on the fraction of renewable sources used to generate electricity. Wind energy is thus a vital candidate and has experienced a remarkable surge recently, establishing itself as a leading renewable power source worldwide. The research on Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-based type 4 wind farms has indicated that the Phase-locked Loop (PLL) bandwidth significantly impacts Sub-Synchronous Resonance (SSR). However, the influence of PLL architecture on SSR remains unexplored and warrants investigation. Therefore, this paper investigates PLL architectural variations in PLL Loop Filter (LF) to understand their impact on SSR in type 4 wind farms. Specifically, an in-depth analysis of the Notch Filter (NF)-based enhanced PLL is conducted using eigenvalue analysis of the admittance model of a PMSG-based type 4 wind farm. The findings demonstrate that the NF-based enhanced PLL exhibits superior performance and improved passivity in the sub-synchronous frequency range, limiting the risk of SSR below 20 Hz. Additionally, Nyquist plots are employed to assess the impact on system stability resulting in increased stability margins. In the future, it is recommended to further investigate and optimize the PLL to mitigate SSR in wind farms.