Semi-supervised surface defect detection of wind turbine blades with YOLOv4

Timely inspection of defects on the surfaces of wind turbine blades can effectively prevent unpredictable accidents.To this end,this study proposes a semi-supervised object-detection network based on You Only Looking Once version 4(YOLOv4).A semi-supervised structure comprising a generative adversarial network(GAN)was designed to overcome the difficulty in obtaining sufficient samples and sample labeling.In a GAN,the generator is realized by an encoder-decoder network,where the backbone of the encoder is YOLOv4 and the decoder comprises inverse convolutional layers.Partial features from the generator are passed to the defect detection network.Deploying several unlabeled images can significantly improve the generalization and recognition capabilities of defect-detection models.The small-scale object detection capacity of the network can be improved by enhancing essential features in the feature map by adding the concurrent spatial and channel squeeze and excitation(scSE)attention module to the three parts of the YOLOv4 network.A balancing improvement was made to the loss function of YOLOv4 to overcome the imbalance problem of the defective species.The results for both the single-and multi-category defect datasets show that the improved model can make good use of the features of the unlabeled images.The accuracy of wind turbine blade defect detection also has a significant advantage over classical object detection algorithms,including faster R-CNN and DETR.

Wind Turbine Noise Reduction through Blade Retrofitting

This paper outlines a plan for the effective reduction of the audible sound level produced by aerodynamic noise from the power-generating turbine blades. The contribution of aerodynamic noise can be divided into two categories: inflow turbulence and airfoil self-noise. The base model and retrofit blade designs were modeled in SolidWorks. Subsequently, noise prediction simulations were conducted and compared to the base blade model to determine which modification provided the greatest benefit using SolidWorks Flow Simulation. The result of this project is a series of blade retrofit recommendations that produce a more acoustically efficient design and reduce noise complaints while enabling turbines to be placed in locations that require quieter operations.

Dynamic Protective Control Strategy for Distributed Generation System with Fixed-speed Wind Turbines

The characteristics of induction generator based fixed-speed wind turbines(FSWT)are investigated.The impacts of different execution time in protective operations are studied under different fault duration and various wind velocity situations,e.g.,FSWT stabilities of load shedding in distribution systems.Based on this research,a dynamic protective control strategy for a distributed generation system(DGS)with FSWT is proposed.Finally,simulation results demonstrate the effectiveness of the strategy.

Maximum Power Point Tracking in Variable Speed Wind Turbine Based on Permanent Magnet Synchronous Generator Using Maximum Torque Sliding Mode Control Strategy

The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, the rotor speed is set at an optimal point for different wind speeds. As a result of which, the tip speed ratio reaches an optimal point, mechanical power coefficient is maximized, and wind turbine produces its maximum power and mechanical torque. Then, the maximum mechanical torque is tracked using electromechanical torque. In this technique, tracking error integral of maximum mechanical torque, the error, and the derivative of error are used as state variables. During changes in wind speed, sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking(MPPT). In this method, the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal. The result of the second order integral in this model includes control signal integrity, full chattering attenuation, and prevention from large fluctuations in the power generator output. The simulation results, calculated by using MATLAB/m-file software, have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator(PMSG).

Performance analysis of 20 Pole 1.5 KW Three Phase Permanent Magnet Synchronous Generator for low Speed Vertical Axis Wind Turbine

This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in consideration and the entire simulation is carried in Matlab/Simulink environment. The rated power for the generator is fixed at 1.5 KW and number of pole at 20. It is observed under low wind speed of6 m/s, a turbine having approximately1 mof radius and2.6 mof height develops 150 Nm mechanical torque that can generate power up to 1.5 KW. The generator is designed using modeling tool and is fabricated. The fabricated generator is tested in the laboratory with the simulation result for the error analysis. The range of error is about 5%-27% for the same output power value. The limitations and possible causes for error are presented and discussed.

An analytic electromagnetic calculation method for performance evolution of doubly fed induction generators for wind turbines

An analytic electromagnetic calculation method for doubly fed induction generator(DFIG) in wind turbine system was presented. Based on the operation principles, steady state equivalent circuit and basic equations of DFIG, the modeling for electromagnetic calculation of DFIG was proposed. The electromagnetic calculation of DFIG was divided into three steps: the magnetic flux calculation, parameters derivation and performance checks. For each step, the detailed numeric calculation formulas were all derived. Combining the calculation formulas, the whole electromagnetic calculation procedure was established, which consisted of three iterative calculation loops, including magnetic saturation coefficient, electromotive force and total output power. All of the electromagnetic and performance data of DIFG can be calculated conveniently by the established calculation procedure, which can be used to evaluate the new designed machine. A 1.5 MW DFIG designed by the proposed procedure was built, for which the whole type tests including no-load test, load test and temperature rising test were carried out. The test results have shown that the DFIG satisfies technical requirements and the test data fit well with the calculation results which prove the correctness of the presented calculation method.

Isolated MicroGrid’s Voltage and Frequency Characteristic with Induction Generator Based Wind Turbine

To save on the island area's power supply cost and protect the clean environment, the Isolated MicroGrid is being duly considered. Consisting of the Wind Turbine Generator (WT), photovoltaic generator, battery system, back-up diesel generator, etc., Isolated MicroGrid, which usually uses the inverter to maintain voltage and frequency of the system, is very weak in terms of voltage and frequency stability compared to the large-scale electrical power system. If wind turbine generator is applied to this weak power system, it could experience many problems in terms of maintaining its voltage and frequency. In this paper, the measurement result of voltage and frequency is presented for MicroGrid, which consists of the Wind Turbine Generator adopting the induction generator and the battery system. MicroGrid’s voltage waveform distortion and Wind Turbine Generator’s output oscillation problems are analyzed using PSCAD/EMTDC. Based on the analyzed result, the importance of type and capacity choice has been suggested in case the Wind Turbine Generator is applied to the Isolated MicroGrid.

The Multi-Objective Optimization of AFPM Generators with Double-Sided Internal Stator Structures for Vertical Axis Wind Turbines

The axial flux permanent magnet(AFPM)generator with double-sided internal stator structure is highly suitable for vertical axis wind turbines due to its high power density.The performance of the AFPM generator with double-sided internal stator structure can be improved by the reasonable design of electromagnetic parameters.To further improve the overall performance of the AFPM generator with double-sided internal stator structure,multivariable(coil widthω_(c),permanent magnet thickness h,pole arc coefficient α_(p) and working air gap l_(g))and multi-objective(generator efficiencyη,total harmonic distortion of the voltage THD and induced electromotive force amplitude EMF)functional relationships are innovatively established.Orthogonal analysis,mean analysis and variance analysis are performed on the influence parameters by combining the Taguchi method and response surface methodology to study the influence degrees of each influence parameter on the optimization objectives to determine the most appropriate electromagnetic parameters.The optimization results are verified by 3D finite element analysis.The optimized APFM generator with double-sided internal stator structure exhibits superior economy,stronger magnetic density,higher efficiency and improved power quality.

Connecting Wind Turbine Generator to Distribution Power Grid--A Preload Flow Calculation Stage

A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.

Application of SABO-VMD-KELM in Fault Diagnosis of Wind Turbines

In order to improve the accuracy of wind turbine fault diagnosis,a wind turbine fault diagnosis method based on Subtraction-Average-Based Optimizer(SABO)optimized Variational Mode Decomposition(VMD)and Kernel Extreme Learning Machine(KELM)is proposed.Firstly,the SABO algorithm was used to optimize the VMD parameters and decompose the original signal to obtain the best modal components,and then the nine features were calculated to obtain the feature vectors.Secondly,the SABO algorithm was used to optimize the KELM parameters,and the training set and the test set were divided according to different proportions.The results were compared with the optimized model without SABO algorithm.The experimental results show that the fault diagnosis method of wind turbine based on SABO-VMD-KELM model can achieve fault diagnosis quickly and effectively,and has higher accuracy.

Dynamic Simulation of Novel Small Wind Turbine Generation System with SynRG

This paper describes a small wind turbine generation system with SynRG （synchronous reluctance generator）. SynRGs are robust and inexpensive. In addition, SynRG has no cogging torque. Hence, wind turbine generation system with SynRG can achieve smooth start at low wind velocity. The rotor design of proposed SynRG is multi flux barrier type. With FEA （finite element analysis） software, the characteristics of SynRG are brought out, and the performance of wind turbine generation system with SynRG including copper loss and iron loss is simulated by FEA coupled with the motion equation of the wind turbine generation system under the maximum power point tracking control. In this paper, the constant wind test and the quasi-natural wind test are conducted. In conclusion, the results of these simulations indicate that the wind turbine generation system with SynRG has good performance, especially in starting phenomena.

基于E-Wind Turbine实验平台的风力发电控制系统

风力发电系统具有规模大、实际现场培训成本高、危险系数高等特点,因此基于风力发电仿真设备的风力发电控制研究是十分必要的。以E-Wind Turbine实验平台为例,详细介绍了变速、变桨距双馈风力发电系统实验平台的构成与控制策略的实现方法。基于S7-1200系列的PLC控制器,利用PORTAL STEP 7集成开发环境,实现了风机的偏航、转速控制以及功率控制。仿真实验结果表明,设计的风力发电控制系统可以有效地模拟实际风力发电机的各种控制要求,为风力发电控制策略的研究提供了一种有效手段。

Prediction of Short-Term Distributions of Load Extremes of Offshore Wind Turbines

This paper proposes a new methodology to select an optimal threshold level to be used in the peak over threshold （POT） method for the prediction of short-term distributions of load extremes of offshore wind turbines. Such an optimal threshold level is found based on the estimation of the variance-to-mean ratio for the occurrence of peak values, which characterizes the Poisson assumption. A generalized Pareto distribution is then fitted to the extracted peaks over the optimal threshold level and the distribution parameters are estimated by the method of the maximum spacing estimation. This methodology is applied to estimate the short-term distributions of load extremes of the blade bending moment and the tower base bending moment at the mudline of a monopile-supported 5MW offshore wind turbine as an example. The accuracy of the POT method using the optimal threshold level is shown to be better, in terms of the distribution fitting, than that of the POT methods using empirical threshold levels. The comparisons among the short-term extreme response values predicted by using the POT method with the optimal threshold levels and with the empirical threshold levels and by using direct simulation results further substantiate the validity of the proposed new methodology.

Fractional-Order Control of a Wind Turbine Using Manta Ray Foraging Optimization

In this research paper,an improved strategy to enhance the performance of the DC-link voltage loop regulation in a Doubly Fed Induction Generator(DFIG)based wind energy system has been proposed.The proposed strategy used the robust Fractional-Order(FO)Proportional-Integral(PI)control technique.The FOPI control contains a non-integer order which is preferred over the integer-order control owing to its benefits.It offers extra flexibility in design and demonstrates superior outcomes such as high robustness and effectiveness.The optimal gains of the FOPI controller have been determined using a recent Manta Ray Foraging Optimization(MRFO)algorithm.During the optimization process,the FOPI controller’s parameters are assigned to be the decision variables whereas the objective function is the error racking that to be minimized.To prove the superiority of the MRFO algorithm,an empirical comparison study with the homologous particle swarm optimization and genetic algorithm is achieved.The obtained results proved the superiority of the introduced strategy in tracking and control performances against various conditions such as voltage dips and wind speed variation.

Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions

This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions.

A Sliding Mode Approach to Enhance the Power Quality of Wind Turbines Under Unbalanced Voltage Conditions

An integral terminal sliding mode-based control design is proposed in this paper to enhance the power quality of wind turbines under unbalanced voltage conditions. The design combines the robustness, fast response, and high quality transient characteristics of the integral terminal sliding mode control with the estimation properties of disturbance observers. The controller gains were auto-tuned using a fuzzy logic approach.The effectiveness of the proposed design was assessed under deep voltage sag conditions and parameter variations. Its dynamic response was also compared to that of a standard SMC approach.The performance analysis and simulation results confirmed the ability of the proposed approach to maintain the active power,currents, DC-link voltage and electromagnetic torque within their acceptable ranges even under the most severe unbalanced voltage conditions. It was also shown to be robust to uncertainties and parameter variations, while effectively mitigating chattering in comparison with the standard SMC.

Measurement system for wind turbine acoustic noise assessment based on IEC standard and Qin＇s model

A novel measurement system specially used in noise emission assessment and verification of wind turbine generator systems is presented that complies with specifications given in IEC 61400-11 to ensure the process consistency and accuracy. Theory elements of the calculation formula used for the sound power level of wind turbine have been discussed for the first time, and detailed calculation procedure of tonality and audibility integrating narrowband analysis and psychoacoustics is described. With a microphone and two PXI cards inserted into a PC, this system is designed in Qin′s model using VMIDS development system. Benefiting from the virtual instrument architecture, it′s the first time that all assessment process have been integrated into an organic whole, which gives full advantages of its efficiency, price, and facility. Mass experiments show that its assessment results accord with the ones given by MEASNET member.

PI-MPC Frequency Control of Power System in the Presence of DFIG Wind Turbines

For the recent expansion of renewable energy applications, Wind Energy System (WES) is receiving much interest all over the world. However, area load change and abnormal conditions lead to mismatches in frequency and scheduled power interchanges between areas. These mismatches have to be corrected by the LFC system. This paper, therefore, proposes a new robust frequency control technique involving the combination of conventional Proportional-Integral (PI) and Model Predictive Control (MPC) controllers in the presence of wind turbines (WT). The PI-MPC technique has been designed such that the effect of the uncertainty due to governor and turbine parameters variation and load disturbance is reduced. A frequency response dynamic model of a single-area power system with an aggregated generator unit is introduced, and physical constraints of the governors and turbines are considered. The proposed technique is tested on the single-area power system, for enhancement of the network frequency quality. The validity of the proposed method is evaluated by computer simulation analyses using Matlab Simulink. The results show that, with the proposed PI-MPC combination technique, the overall closed loop system performance demonstrated robustness regardless of the presence of uncertainties due to variations of the parameters of governors and turbines, and loads disturbances. A performance comparison between the proposed control scheme, the classical PI control scheme and the MPC is carried out confirming the superiority of the proposed technique in presence of doubly fed induction generator (DFIG) WT.

Impact of Shaft Stiffness on Inertial Response of Fixed Speed Wind Turbines

Future power system faces several challenges,one of them is the high penetration level of intermittent wind power generation,providing small or even no inertial response and being not contributing to the frequency stability.The effect of shaft stiffness on inertial response of fixed speed wind turbines is presented.Four different drive-train models based on the multi-body system are developed.The small-signal analysis demonstrates no significant differences between models in terms of electro-mechanical eigen-values for increasing shaft stiffness.The natural resonance frequency of drive-train torsion modes shows slightly different values between damped and undamped models,but no significant differences are found in the number-mass models.Time-domain simulations show the changes in the active power contribution of a wind farm based on a fixed speed wind turbine during the system frequency disturbance.The changes in the kinetic energy during the dynamic process are calculated and their contribution to the inertia constant is small and effective.The largest contribution of the kinetic energy is provided at the beginning of the system frequency disturbance to reduce the rate of the frequency change,it is positive for the frequency stability.