基于Matlab/Simulink的小型风力发电机电能质量指标仿真计算与分析

以小型风力发电机组为研究对象,依据IEC标准和国家标准,采用Matlab/Sumilink仿真与电能数据采集实验相结合的方法评价电能质量指标,提出影响电能质量评价指标的因素及优化对策,为提升小型永磁风力发电机组电能质量给予指导依据。研究表明:永磁发电机齿槽数和极对数等结构参数发生改变时,转子转动惯量增大导致频率偏差比增幅达1.37倍,并对发电机内部三相对称性有一定不利,转子磁通量增大使气隙磁场谐波畸变恶化但电压偏差减小;另外,风电机组防止超负荷提高转速可降低电压波动,同时限制高转速运行可避免三相不平衡度超标;此外,长时间温升超标运行导致的发电机绝缘老化和退磁,易使电压偏差和频率偏差比增幅分别达2.03倍和1.36倍。     

风机并网对电能质量影响因子研究

为了给电网控制策略提供可靠的参考依据,对电网在接入风机后电能质量的变化进行了详尽的分析。风机作为电源同时也作为非线性负载接入配电网中使得电能质量的分析更加复杂。首先对国标中着重介绍的稳态电能质量：电压偏差,三相不平衡度,谐波以及电压波动进行理论介绍,然后在Matlab／Simulink上建立了配电系统与风机并网的模型,得到风机对电能质量不同方面的影响程度,最后采用先进电力电子设备为平稳电压电流输出提供一定的方法,并进行验证。研究结果表明,电力谐波和电压波动闪变是风机对电网的最主要的影响因素。     

上海市市级医院建筑能耗评价指标及影响因素研究

结合当前医院的发展,提出了对上海市《市级医疗机构建筑合理用能指南》DB31/T 553-2012的修订思路。基于对国内外用能指南的调研和对2018年全市市级医院用能数据的统计分析,得出单位建筑面积能耗仍是最合适的能耗评价指标,该评价指标与床位数和门急诊人次等业务规模密切相关。通过相关性分析,医院类型不同,单位面积能耗影响因素有所区别。综合医院和中医医院主要受床位数影响,专科医院主要受建筑面积和总医疗量(当量床日)影响。实地调研表明手术量在综合医院和中医医院具备修正条件。     

影响风电场电能质量的因素研究

风电场并网时产生的电压波动和闪变、电压偏差以及谐波,直接影响电网运行的稳定性。本文以某风电场为例,探讨以上影响风电场电能质量的因素。通过对相关因素的阐述、计算及分析,结合国家标准规范,明确电场电能质量的分析评估方法。结果表明,风电并网前需进行电能质量评估,对相关参数进行详细计算,其结果必须满足国标要求,才可实现电网稳定运行。     

小型风力发电机MCS认证要求的研究

英国推出小型风电上网补助政策,必须通过MCS认证才能申请支付上网电价,开拓英国市场的中国小型风电制造商有必要了解MCS认证要求。基于MCS认证的申请流程、参考标准,阐述了产品测试的关键要求,并明确了必须提交的设计资料和工厂审查的基本要求。     

小型风力机风轮主动侧偏机构试验研究

根据输出的功率信号,对尾翼侧偏角度进行调节,可以在保证主动侧偏型小型风力发电机稳定安全运行的基础上,实现风能最大利用.通过实验得出不同侧偏角下风轮功率的输出,然后根据模拟输出功率信号,测试在不同工况下,主动侧偏机构动作的正确性和可行性,为整机试验做好前期准备工作.     

浅论电能质量的问题与改善措施

现代电网与负荷构成出现新的变化趋势,由此带来的电能质量问题一直是电力用户的生产需求驱动的,提出了电能质量的问题,阐明了电能质量的内涵和指标,分析了电能质量的检测内容与方法,提出了改善电能质量的方法和措施。     

基于改进雷达图法的海洋能发电装置电能质量综合评价

为了科学准确评价海洋能发电装置电能质量特性,在传统单项指标评价方法的基础上,提出雷达图法的综合评价方法,并从指标的表现形式、赋权方法和等级划分3个方面做出改进,以更加全面、合理、直观地反映海洋能发电装置电能质量的整体情况。以波浪能发电装置现场测试数据为依据,计算分析该装置的电能质量整体情况,所得结果具有唯一性,并与传统雷达图法的评价结果相比较,验证了该方法的实用性和科学性。     

提高变电站电能质量措施研究

就调整机组无功出力、调节升压变分接头以及投运电抗器措施后对变电站电压和网损影响情况进行计算分析,从而提出量化电压调整措施,确保220kV电压合格率处于国网公司同业对标A段行列。     

基于有序加权平均算子的电能质量评价方法

针对电能质量评价过程中主观因素影响过高的问题,提出了一种基于有序加权平均算子的电能质量综合评价算法。基于耦合主观赋权与客观赋权算法,从时间域和评价指标这两个维度出发,建立了电能质量立体评价方法。通过所建立的指标域电能质量评价模型,对各时间点电能质量较差的部分减分,对较好的部分加分,得到马太效应收益亏损因子,并利用积分法得到评价指标的阶段性评价值;再引入时间域权重,使用线性目标规划模型得出考察周期内各项指标的评价值;最终利用有序加权平均算子对所有初级评价值进行有序加权求和,得到电能质量综合评价值。应用实例分析表明,该评价方法通过有序加权平均能有效区分不同评价对象的质量。     

Applying power quality characteristics of wind turbines for assessing impact on voltage quality

Injection of wind power into an electric grid affects the voltage quality. As the voltage quality must be within certain limits to comply with utility requirements, the effect should be assessed prior to installation. To assess the effect, knowledge about the electrical characteristics of the wind turbines is needed or else the result could easily be an inappropriate design of the grid connection. The electrical characteristics of wind turbines are manufacturer‐specific but not site‐specific. This means that, having the actual parameter values for a specific wind turbine, the expected impact of the wind turbine type on voltage quality when deployed at a specific site, possibly as a group of wind turbines, can be calculated. The methodology for this is explained and illustrated by case studies considering a 5 × 750 kW wind farm on a 22 kV distribution feeder. The detailed analysis suggests that the wind farm capacity can be operated at the grid without causing unacceptable voltage quality. For comparison, a simplified design criterion is considered assuming that the wind farm is only allowed to cause a voltage increment of 1%. According to this criterion, only a very limited wind power capacity would be allowed. Measurements confirm, however, the suggestion of the detailed analysis, and it is concluded that a simplified design criterion such as the ‘1% rule’ should not be used for dimensioning the grid connection of wind farms. Rather, this article suggests a systematic approach including assessment of slow voltage variations, flicker, voltage dips and harmonics, possibly supported by more detailed analyses, e.g. system stability if the wind farm is large or the grid is very weak, and impact on grid frequency in systems where wind power covers a high fraction of the load, i.e. most relevant for isolated systems. Copyright © 2002 John Wiley & Sons, Ltd.     

Grid power quality with variable speed wind turbines

Grid connection of renewable energy sources is essential if they are to be effectively exploited, but grid connection brings problems of voltage fluctuation and harmonic distortion. In the paper, appropriate modeling and simulation techniques are discussed for studying the voltage fluctuation and harmonic distortion in a network to which variable speed wind turbines are connected. Case studies on a distribution network show that the voltage fluctuation and harmonic problems can he minimized with the proposed power electronics interface and control system while the wind energy conversion system captures the maximum power from the wind as wind speed varies. The studies have also demonstrated the ability of the advanced converter to assist the system voltage regulation     

Electrical transients of wind turbines in a small power grid

This paper presents field measurements and calculations on the disconnection and braking of wind turbines (WT) with rated power 60 kW and 100 kW in the grid of two Greek Islands. By means of a digital acquisition system with sampling frequency of 130 kHz, voltages and currents of the WT installations have been measured and analyzed just before and during the transient period. A simulation program has been used for this purpose. Results of simulation and measurements show in a wide range a good agreement. The simulation program was further used to investigate the disconnection process of WT under various circumstances. It is shown that during the WT disconnection, a sudden increase in stator currents may appear. So voltage dips may distort the power quality of the grid. Self-excitation of WT, with large induced voltage, occurs when they operate at low-load even with relatively small capacitive compensation. The amount of energy, that the brake of a WT absorbs during the disconnection, has been studied under various disconnection procedures. Suggestions are made for the proper moment of brake application, so that the energy absorbed is minimum     

Markovian power curves for wind turbines

This paper shows a novel method to characterize wind turbine power performance directly from high‐frequency fluctuating measurements. In particular, we show how to evaluate the dynamic response of the wind turbine system on fluctuating wind speed in the range of seconds. The method is based on the stochastic differential equations known as the Langevin equations of diffusive Markov processes. Thus, the fluctuating wind turbine power output is decomposed into two functions: (i) the relaxation, which describes the deterministic dynamic response of the wind turbine to its desired operation state, and (ii) the stochastic force (noise), which is an intrinsic feature of the system of wind power conversion. As a main result, we show that independently of the turbulence intensity of the wind, the characteristic of the wind turbine power performance is properly reconstructed. This characteristic is given by their fixed points (steady states) from the deterministic dynamic relaxation conditioned for given wind speed values. The method to estimate these coefficients directly from the data is presented and applied to numerical model data, as well as to real‐world measured power output data. The method is universal and is not only more accurate than the current standard procedure of ensemble averaging (IEC‐61400‐12) but it also allows a faster and robust estimation of wind turbines' power curves. Copyright © 2007 John Wiley & Sons, Ltd.     

A novel adaptative maximum power point tracking algorithm for small wind turbines

A novel maximum power point tracking algorithm for small wind turbines is proposed. The solution presented here is an adaptive intelligent algorithm that uses a new advanced perturb and observe method to search for the optimum relationship of the system for tracking the maximum power point even under variable wind conditions. The validity of the proposed algorithm is analysed and the design procedure is presented. Its main virtue resides in its capability to adapt to changes in the turbine and in the surrounding environment, even under variable wind conditions, improving the efficiency of the system. The experimental results confirm the validity of the proposed algorithm.     

Dynamic wind estimation based control for small wind turbines

We introduce a novel scheme for small wind turbines that gives dynamic estimation of wind speed from rotor angular velocity measurements. The estimation proceeds in two different dynamic observers, one giving a valid estimate for higher Tip Speed Ratios (TSRs) and which we call the Upper Wind Estimator (UWE) and the other called the Lower Wind Estimator (LWE) valid for lower TSRs. The meaning of “higher” and “lower”, and the precise regions of validity, are quantified. We further propose a coordinated control scheme using the UWE. Simulations are presented showing closed-loop performance of the turbine and the estimators both in the optimal TSR regulation condition, and the dynamic power-shedding condition caused by a wind gust. An analytic analysis of closed-loop stability and of the convergence and bias properties of the estimator is provided. Empirical data showing performance on a real turbine is also presented.     

Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking

The Permanent Magnet Synchronous Generator (PMSG) with diode bridge is frequently used in small Wind Energy Conversion Systems (WECS). This configuration is robust and cheap, and therefore suitable for small WECS. In order to achieve Maximum Power Point Tracking (MPPT) with no mechanical sensors, it is possible to impose the relationship between the DC voltage and the DC current on the optimum operating points. However, this relationship is difficult to calculate theoretically since the whole system is involved. In fact, as there is no model of the whole system in the literature, the optimum curve I_L¹(V_dc) is obtained with experimental tests or simulations. This paper develops an accurate model of the whole WECS, thereby making it possible to relate the electrical variables to the mechanical ones. With this model, it is possible to calculate the optimum curve I_L¹(V_dc) from commonly-known system parameters and to control the system from the DC side. Experimental results validate the theoretical analysis and show that maximum power is extracted for actual wind speed profiles.     

大型风力发电机组调向功率的探讨

针对风力发电机组调向对风机构工作性能直接关系到机组的整体性能，从研究风力发电机组调向阻力矩入手，提出了确定机组调向功率需考虑的一些因素和方法。