This paper presents a review of large-scale testing for wind turbine nacelles, i.e. sophisticated systems designed for operation under extreme loads and harsh environmental conditions. Given the critical need for high reliability, comprehensive developmental testing is paramount. As onshore and offshore wind power scales up, testing methodologies are continually evolving. This article first delineates the purposes and fundamental content of nacelle testing. It then surveys the current status of international ground-based public test facilities for large-power wind turbine drivetrains, providing a comparative analysis of their characteristics, including rotor torque loading, non-torque loading, and electrical grid simulation capabilities. A detailed introduction to a 25 MW wind turbine nacelle test bench at China Electric Power Research Institute is provided. The 25 MW test bench, integrating a dual-motor drive, Yoke loading, 90 MVA grid emulation, and a digital twin, has successfully certified a 26 MW turbine, demonstrating world-leading performance. The paper concludes with a forward-looking perspective on the future of public ground testing systems for large-scale wind turbine nacelles.

In the wind power concentrated grid-connection areas such as Northwest and North China, the grid strength is relatively weak, with small local loads and lack of reactive power support. Voltage unbalance happen in some wind farms under certain operating conditions, leading to disconnection of large scale wind turbines, which affects the normal and safe operation of the wind farms. This paper analyzes the voltage unbalance mechanism in large-scale wind power grid integration area, compares the specific requirements concerning voltage unbalance in domestic and international standards, and conducts field measurements in wind farm based on the IEC 61400-21-1:2019 standard. This paper provides reference for solve voltage unbalance problems caused by wind power integration.

The planetary bearing looseness fault can cause the planetary gear train to fail. Conventional modeling methods do not consider complex component-coupling relationships for fault feature analysis. As a result, a joint model is developed to examine the dominant relationship between planetary bearings and the planetary gear train. Firstly, the planetary bearing is modeled in the normal and fault states. Then, a refined joint planetary gear train dynamic model is constructed, which is composed of the planetary gears, the ring gear, the carrier, the sun gear, and the planetary bearings. Finally, the simulation results show that, when the planetary bearing is in the looseness fault state, its fault characteristic presents as the rotation frequency of the carrier and its harmonics. The on-site signal of a 2.0 MW wind turbine is used to verify the effectiveness of the model. The proposed model can provide the basis for the fault mechanism analysis and fault diagnosis of rolling bearing outer ring looseness.

The impedance measurement is becoming widely accepted for characteristic depiction and stability analysis of renewable energy generation. Usually, it is conducted using software or controller hardware-in-the-loop simulations, but rarely in field tests. This work presents the impedance measurements of a voltage source converter and various wind turbines in field tests. The tests were conducted by full-power grid simulators, which have been used in grid adaptability tests in China for years. In this paper, the test setup is introduced. The test procedures are given according to the related standards and documents. The test results are illustrated and compared. These field tests give clear frequency-domain characteristics of the devices under test and validate the theoretical analysis.

Wind turbine generators (WTGs) can provide fast frequency support to power systems through inertial control via the release of kinetic energy stored in rotating masses. However, because the kinetic energy is limited, the frequency support from WTGs based on inertial control cannot last until the system frequency recovers to the nominal value. Thus, it must be terminated during system frequency control, which results in adverse effects on the system frequency response. To guarantee sufficient energy and fast response for the frequency support of a permanent magnet synchronous generator based WTG, this study proposed the integration of a DC/DC converter-interfaced supercapacitor (SC) at the DC link of the WTG and consequently formed an integrated system of WTG and SC (WTG-SC system). First, the configuration of the SC was proposed based on the evaluation of the energy consumption of the WTG-SC system for frequency support and the available kinetic energy of the WTG. Second, a control structure that coordinates the machine-side converter (MSC), grid-side converter (GSC), and DC/DC converter of the SC was proposed. Finally, a "dual-droop"frequency support control scheme for the WTG was proposed to enhance the WTG-SC system's frequency support capability and the efficiency of energy utilisation during frequency support. The efficacy of the proposed approach was validated using a modified IEEE 39 bus system with a wind farm comprising 100 WTG-SC systems under different operating conditions.

电压源型构网控制赋予风电机组建立和支撑电压的能力,有望助力碳中和目标和新型电力系统目标的实现.该文综述电压源型构网风电机组的研究现状:首先,介绍当前应用于风电机组的几种典型电压源型构网控制策略;进而,分别针对当前主流的风电机组类型,从变流器系统的协调控制角度,阐述电压源型构网控制的实现方案;在此基础上,从频率稳定、小干扰并网稳定和暂态稳定3个方面,对电压源型构网风电机组的稳定性相关研究进行讨论;最后,总结电压源型构网风电机组的应用现状,并对其研究前景与挑战进行展望.

In order to build a new power system with new energy generation as the main body, promoting clean energy such as wind power has entered a stage of rapid development. The grid connection of a high proportion of new energy through flexible High voltage DC transmission (HVDC) has become a typical scenario of the power system. Since both ends of the new energy transmission line connected by flexible HVDC grids are power electronic devices, the current fault characteristics are completely different from those of synchronous power source, so it is of certain research significance and extensive application value to study the fault characteristics of the flexible HVDC transmission system in the new energy access scenario. In this paper, based on offshore wind power grid-connected flexible DC transmission project, the corresponding simulation model is built in the PSCAD/EMTDC software platform, and the characteristics of short circuit current provided by the flexible direct system are analyzed when different fault scenarios occur on the system outgoing line. Through the waveform analysis and comparison of the simulation experiment, it is found that the fault characteristics of the flexible and direct system change essentially under the scenario of a new energy grid connection, and the short-circuit current characteristics provided by the flexible and direct system are significantly different from those of the conventional power supply. The simulation experiment clarified the fault characteristics of the energy-flexible HVDC outgoing system and provided a strong basis for the protection of the new energy outgoing transmission line.

准确的模型和参数是仿真分析风电机组动态特性的基础,变流器控制参数的"黑箱化"使得对其进行参数辨识成为必然.文章主要研究了双馈风电机组变流器控制系统的参数辨识问题.首先建立了变流器控制系统双输入单输出传递函数模型,并离散化得到其辨识等效数学模型.基于该辨识模型,提出了从二次侧量测信号叠加三相M序列的激励方法和基于正余弦优化算法的辨识方法.最后,利用仿真算例验证了该参数辨识方法的正确性和可行性,对比了故障工况下原系统与辨识模型有功输出,结果表明辨识误差满足精度要求;同时仿真分析了锁相环相位误差、电网电压和风速波动对辨识结果的影响.

To enhance generating capacity and reliability of multi-machine parallel power generation, implement the efficiency optimization, a current distribution control method based on differential evolution (DE) algorithm is proposed for the switched reluctance generator (SRG) in parallel. The load current is stabilized by the maximum value current sharing control (CSC) firstly. Then, the current distribution control method is adopted, which can adjust the reference current of each parallel generator in the current distribution part, so as to change the working point of each generator and implement the optimization of parallel system efficiency. The performances of the proposed control method are evaluated in detail by the simulation, and comparison with traditional current sharing control is carried out as well.

To improve the endurance and charging flexibility of electric vehicle battery packs, this paper proposes a multi-battery block module (MBM) topology for four-phase switched reluctance motors (SRMs), which not only allows flexible electric vehicle operation, but also achieves fast demagnetization and excitation. By integrating the multi-battery block module and photovoltaic (PV) panel into an asymmetrical half-bridge (AHB) converter, the MBM topology is designed to supply a multilevel bus voltage for the SRM drive. To improve the endurance of battery packs, a PV panel is also added to the topology to charge battery packs when the system is stationary. According to the different operation requirements, multiple power supply modes and charging modes can be realized by controlling the power devices in the proposed MBM topology. The simulation results based on the MATLAB/Simulink platform and the experimental results on a four-phase 8 / 6 switched reluctance motor verify the effectiveness of the proposed design.

As a rich clean and environmentally friendly renewable resources, wind energy has emerged as a strategic choice for countries around the world. Because the wind turbines often operate in severe working conditions such as variable load and large temperature difference they are prone to failures and possible shutdowns. The shutdowns however seriously affect the economic benefits of the wind turbines. Initiative maintenance has become a worldwide recognized scientific method for planning and determining preventive maintenance work, the implementation of this strategy relies on real-time condition monitoring and fault signal identification methods. The condition monitoring of wind turbine can help master the health state and power generation performance of wind turbine, so as to timely formulate maintenance strategies and adopt technical modification measures to improve power generation performance, reduce the down time of wind turbine, avoid the occurrence of major faults, save maintenance cost and improve power generation capacity. Therefore, a condition monitoring system is built on a wind turbine of Zhangjiakou, and a systematic signal analysis method is proposed, time-domain synchronous averaging technology, based on variable period, impulse signal feature extraction technology based on Teager and signal decomposition technology based on CEEMD. The proposed method realizes the signal analysis and feature extraction of non-stationary nonlinear, weak signal and frequency aliasing signals, and successfully diagnose the gearbox secondary meshing failure during the long-term monitoring. This confirms that the monitoring system methods and signal analysis technology proposed in this paper can effectively realize the condition monitoring and fault diagnosis of wind turbines.

The grid forming wind turbine technology provides a solution to the future power grid in China dominated by new energy sources. With China's first grid forming DFIG wind turbine successfully operated in Zhangbei Wind Power Test Base, the test and assessment methods should be investigated to validate and understand its behaviors. In this work, the grid forming control technique adopted in the prototype wind turbine is first introduced. Then, a high fidelity controller hardware-in-the-loop platform is constructed as an approach for testing and assessment. Two capabilities of the grid forming wind turbine are mainly validated, including weak grid operation and primary frequency response. Finally, the tests are conducted in the modeled system, where the strengths and potential problems of the grid forming wind turbine are identified. This work presents a viable option for the test and assessment of the grid forming wind turbine, and is expected to help the industry to reach a consensus on its operation and characteristics.

考虑特定场址环境条件对于风电机组载荷与结构安全特性的影响,基于某3 MW双馈型风电机组载荷模型,运用GHBladed软件对不同场址环境条件下的风电机组载荷进行仿真计算,形成特征环境条件下载荷特性数据库.分析各环境条件参数对风电机组关键部件极限与疲劳载荷的影响特性.基于特征载荷数据库,运用BP神经网络预测方法,建立特定场址条件下风电机组关键部件极限与疲劳载荷预测模型,并将模型预测结果与仿真结果进行比对.结果表明,基于BP神经网络的风电机组极限与疲劳载荷预测结果误差在6％以内,该方法对于不同场址条件下风电机组载荷与结构安全性评估具有普遍适用性.

针对风电机组惯量响应结束后可能出现的功率跌落和较大的机械载荷冲击问题,分析了双馈风电机组虚拟惯量控制原理,提出了基于指数函数渐进趋近的风电机组转速恢复方法.通过动态调整调节系数,改变参考功率与目标恢复功率渐近速率,降低机械载荷冲击.分析了调节系数与转速、目标恢复功率的关系,从功率跌落优化角度研究了两种目标恢复功率的控制方法,同时给出了惯量响应期间主控与变流器协调配合方法.相比常规控制方式,所提方法能有效降低转速恢复期间机械载荷并减小功率跌落深度.在Matlab与Bladed中建立了包含气动、电气与机械特性的风电机组联合仿真模型,仿真验证了所提控制策略的正确性和有效性.

In a riser-drill string coupling system, the drill string extends from platform to downhole, and its exterior tube is divided by mud line into two parts: riser for upside and borehole for downside. Due to such a pipe-in-pipe structure, an improved dynamic model is proposed to take the multipoint interactions between the inner and outer pipes into consideration. The dynamic responses of this system are analyzed by Computer Aided Engineering (CAE) techniques; specifically, it is numerically simulated in Abaqus; then, both the parametric sensitivity analysis and the main effect analysis are carried out in Isight to determine the optimization parameters and the optimization strategy. Moreover, six-sigma algorithm in Isight is applied to simultaneously drive the neighborhood cultivation genetic algorithm (NCGA) to conduct multiobjective optimization and drive the Monte Carlo method to analyze the stability of the obtained optimal solution. Based on the above investigations, a software package is developed via the secondary developments of both Abaqus and Isight. By this way, the optimization design of the riser-drill string coupling system based on dynamic analysis can be conducted effectively and efficiently.

When a maintenance and operations ship is berthing, there is a chance the ship may collide into the wind turbine. When these ships collide into wind turbine structures, this can result in significant changes to the foundation and structure of the wind turbine. In this paper, the structural load of a 4 MW offshore wind turbine was analyzed during a collision with an operations and maintenance ship. The variations in the wind speeds on hub height, waves, and the sea currents were measured. The dynamic simulation of the wind turbine was carried out using the test data as the input parameters. As a result, the load condition of the turbine without a collision was obtained. Finally, the measured turbine load was compared with the simulation results. This study shows that the collision of the operation and the maintenance ship increases the bending moments at the tower’s bottom and the blade’s roots.

针对风电机组不主动参与系统一次调频的问题,分析风电机组转子动能控制与桨距角调频的控制原理与技术特点,利用2种调频方式在响应与支撑时间上的互补关系,提出一种转子动能与桨距角协调控制的组合调频方法,优化限功率状态下风电机组一次调频性能.设计风电机组一次调频曲线,并进行一次调频控制系统设计.搭建某2.0 MW双馈风电机组Bladed+Matlab联合仿真模型,进行一次调频全过程动态仿真,验证控制策略的正确性与有效性.在2.0 MW大容量机组上进行现场试验研究,试验结果支持理论分析和仿真结果.

大规模并网风电场参与一次调频是电网为保证自身安全做出的必然选择,有功响应的快速性和稳定性是风电场需要解决的关键问题.提出一种基于分层架构的风电场参与电网一次调频的控制策略.在风电机组控制层,提出了一种改进的带惯量补偿的有功控制策略,提高一次调频的响应速度.在风电场控制层通过改进的惯量响应协调控制和功率备用控制策略,避免电网频率出现波动,并满足不同风况下备用功率的要求.基于Matlab/Simulink建立了含风电场的电力系统仿真模型,仿真结果表明风电场具备全工况条件下参与电网一次频率调整的能力.最后在某49.5 MW风电场现场验证了所提控制策略的有效性.

针对高比例风电电力系统频率/电压稳定性问题,介绍了虚拟同步控制的理论基础,对比分析了双馈风电机组与传统同步机数学模型。基于模型相似性推导了风电机组虚拟同步发电机的内电势、功角及功率传输方程,并揭示了其变化规律。研究了一种含阻尼环节的电流源型风电机组虚拟同步控制策略,并进行了虚拟同步控制外环和电流控制内环设计。在Matlab/Simulink中建立了双馈风电机组虚拟同步发电机仿真模型,实现了虚拟同步发电机惯量、阻尼、一次调频和无功调压特性的全过程模拟。仿真结果证实了理论分析的正确性与控制策略的有效性。

Due to the rotor side converter of doubly-fed induction generator based on wind turbine (DFIG-WT) decouples its rotor kinetic energy to the grid frequency, the DFIG-WT has no ability to provide inertial support for the grid frequency disturbance. In this paper, the feasibility analysis for DFIG-WT providing frequency inertial support based on rotor speed control is discussed at first. Then, via analyzing the rotor speed control mechanism of DFIG-WT, a frequency support control based on variable proportional coefficient is proposed. At the same time, the synergetic control theory is adopted to design the control strategy of the variable proportion coefficient. Based on setting up the macro variable which is composed of grid frequency, the virtual inertia time constant and the increment of stator active power, the control law of the variable proportion coefficient can be derived through designing the dynamic characteristic of the macro variable to satisfy the first order inertia. The synergetic control will make the virtual inertia of DFIG vary with frequency, and it has better frequency regulation performance than traditional virtual inertia control. Finally, based on the simulation in WSCC 9-bus wind power system, the effectiveness of the proposed synergetic control strategy of virtual inertial is verified. The simulation results show that the proposed control strategy has the advantage on adaptively regulating the variable proportion coefficient for implementing the DFIG-WTs with different operation state to coordinately provide the frequency support.