风电高渗透率下中长期时间尺度系统频率波动仿真研究

随着风电渗透率地不断提高,风电并网对电力系统频率稳定的影响越来越大。鉴于已有的电力系统仿真软件对仿真互联电网短期和中长期频率控制不能很好地满足要求,且各种类型发电机组的数学模型也是根据需要建立,因此提出了建立基于准稳态法利用MATLAB编程实现的中长期时间尺度频率波动仿真系统。该系统能够提供风电场、水电机组和火电机组参与系统频率控制数学模型,区域电网联合频率控制数学模型,并且能够进行系统备用调整容量分析和AGC性能监视。     

交直流混合微电网多时间尺度协同控制

为了更好地将可再生交直流电源并入电网,提出了一种适用于交直流混合微电网的多时间尺度协同控制方法,该交直流混合微电网由一个交流子网和一个直流子网组成,它们之间通过双向功率转换器(bidirection-al power converter,BPC)连接.该控制方法在三个时间尺度上依次稳定功率波动,在第一时间尺度中,当某子...     

变风速下双馈异步风机在微电网中的电压频率协调控制

微电网线路阻抗比值较大,当微电网孤岛运行时,负荷频繁投切导致微电网电压、频率波动较大。文章对双馈感应风电机组与柴油机协调控制共同为微电网提供电压、频率支撑,提出了DFIG在微电网中的电压、频率协调控制策略。DFIG有功功率控制采用虚拟惯量控制与超速减载控制,并采用f-P下垂控制与柴油机配合对微电网频率进行调节。通过控制DFIG转子侧换流器的无功功率,并采用V-Q下垂控制与柴油机配合对微电网电压进行控制。最后在DIgSILENT中搭建了风光柴中压微电网模型,仿真结果验证了文章所提控制策略的有效性。     

基于控切配合的高比例风电电力系统紧急频率控制方法

高比例风电送端电网易因通道异常和中断导致高频问题。现有研究忽略了风电机组的减载控制与切机的相互影响,不仅影响频率控制效果,还可能限制系统的后续频率响应能力。为此,分析了风电电力系统的暂态频率响应特性,提出了双馈风电机组“控切配合”的思想,构建了考虑双馈风电机组转速恢复约束的风电电力系统紧急频率控制的优化模型;进而提出了一种基于控切配合的高比例风电电力系统紧急频率控制方法,最后通过算例验证表明该方法能够有效提高电力系统的紧急频率控制能力,保障高比例风电电力系统的频率稳定。     

计及调频效益的微电网源-荷动态频率调整研究

频率稳定是维持微电网孤岛运行的关键因素。需求响应技术的应用为孤岛微电网的频率控制提供了新方法。针对孤岛微电网频率稳定问题,文章提出一种考虑调频效益的源-荷协同频率控制策略,使可控负荷与新能源共同参与微电网频率调整。最后,在Matlab软件中搭建了微电网模型,仿真结果验证了文章计及调频效益下的源-荷协同频率控制策略的有效性,使微网调频时的功率分配更合理。     

基于改进下垂控制的双馈风电机组频率控制策略

为高效利用风机旋转动能,提高风电机组的频率支撑能力,文章在传统下垂控制策略的基础上,提出一种基于改进下垂控制的双馈风电机组频率控制策略。该策略通过结合扰动后电网频率动态特性,提出了可随系统频率变化率（RoCoF）变化的自适应下垂控制系数,在不同扰动下,有效提高风电机组频率支撑能力,改善系统最大频率偏差和最大频率变化率。基于EMTP-RV仿真软件搭建了四机两区域系统模型进行仿真,结果表明,改进后的下垂控制可有效应对不同扰动工况,提高了风电机组频率响应能力,进一步地改善了系统频率稳定性。     

双馈风电场有功频率分层控制

风电场有功频率控制是风电场接入电网运行的关键技术。在分析双馈风力发电机组减载运行控制策略及超速法下双馈风力发电机组的减载运行调节能力的基础上,提出了提高双馈风电场的有功调节能力及接入电网后系统频率稳定性的有功频率分层控制策略。该策略根据不同风速区风电机组的减载运行调节能力差异,设计了风电场层分配策略及风电机组层控制策略,在满足有功控制要求的前提下,尽可能提高风电场对电力系统暂态频率稳定的支持。仿真结果表明,该控制策略在系统稳定运行时尽可能存储转子动能,当出现功率扰动后,能够通过快速释放转子存储的动能响应系统频率变化,从而提高了双馈风电场接入电网后的系统频率稳定性。     

直流微电网中风电机组的双向扩展惯性控制方法

新能源直流微电网惯性响应能力弱、系统稳定性较差,传统惯性控制策略无法针对不同工况灵活调整惯性强弱,为此该文提出了双向扩展惯性控制方法。首先建立含风电的直流微电网结构模型,分析了系统惯性和风电机组惯性的关系。在此基础上,提出了直流微电网中风电机组的双向扩展惯性控制方法,该方法利用指数函数的极速增长性,快速调节机组的功率跟踪曲线比例系数,大幅扩展风电机组的惯性,同时在直流电压突变初期,通过正向扩展惯性控制,增加系统惯性阻止其变化,在直流电压恢复初期,通过负向扩展惯性控制,减小系统惯性促进其稳定,实现了惯性双向灵活调节,有效提高系统稳定能力。最后,在Matlab/Simulink仿真软件中搭建了直流微网模型,验证所提控制方法的有效性。     

含大规模风电接入电网的双时间尺度无功协调控制

大规模风电集中并网已经成为中国风电送出的主要模式,通过配置无功补偿装置,使电网无功电压波动问题得到了大幅改善,但电压波动问题在局部地区仍然存在。文章将无功补偿装置分为离散控制和连续控制两类,针对汇集站电压的长周期大幅度波动分量和短周期小幅度波动分量,提出分别应用离散和连续无功补偿装置在小时级和分钟级时间尺度上进行抑制;在此基础上,提出了两类无功补偿装置滚动协调控制策略。通过对我国某大规模风电集中接入电网进行仿真计算,验证了所提控制策略可有效解决电压波动问题,显著提高了含大规模风电接入电网的电压运行水平。     

分频风电系统频率控制策略研究

综合考虑最大化的利用风能和设备成本,以及风电场的尾流效应,提出了一种如何确定分频风电系统低频侧频率的最优给定值,并通过实际算例验证了频率选定方法的合理性。     

含风力发电的微电网发电可靠性评估

微电网具有接入各种可再生能源发电装置的能力,但接入风力发电机时,其出力具有随机性和间歇性,对描述微电网发电能力的发电可靠性评估造成困难。文章根据微电网地域范围小、气候特征趋同的特点,提出了分段连续的发电出力概率分布模型,对微电网发电可靠性进行评估,并与蒙特卡罗模拟法进行比较,结果表明该模型和算法具有直观的数学和物理意义,理论上具有精确的计算结果。     

A new control methodology of wind turbine generators for frequency control of power system in isolated island

A wind turbine generator (WTG) system's output is not constant and fluctuates depending on wind conditions. Fluctuating power causes frequency deviations and adverse effects to an isolated power system when large output power from WTG systems is penetrated in the power system. This paper presents an output power control methodology of a WTG for frequency control using a load power estimator. The load power is estimated by a disturbance observer, and the output power command of the WTG is determined according to the estimated load. Besides, the WTG can also be controlled during wind turbulence since the output power command is determined by considering wind conditions. The reduction of the power system frequency deviation by using the WTG can be achieved by the proposed method. The effectiveness of the proposed method is validated by numerical simulations. Copyright © 2010 John Wiley & Sons, Ltd.     

Variability in large‐scale wind power generation

The paper demonstrates the characteristics of wind power variability and net load variability in multiple power systems based on real data from multiple years. Demonstrated characteristics include probability distribution for different ramp durations, seasonal and diurnal variability and low net load events. The comparison shows regions with low variability (Sweden, Spain and Germany), medium variability (Portugal, Ireland, Finland and Denmark) and regions with higher variability (Quebec, Bonneville Power Administration and Electric Reliability Council of Texas in North America; Gansu, Jilin and Liaoning in China; and Norway and offshore wind power in Denmark). For regions with low variability, the maximum 1 h wind ramps are below 10% of nominal capacity, and for regions with high variability, they may be close to 30%. Wind power variability is mainly explained by the extent of geographical spread, but also higher capacity factor causes higher variability. It was also shown how wind power ramps are autocorrelated and dependent on the operating output level. When wind power was concentrated in smaller area, there were outliers with high changes in wind output, which were not present in large areas with well‐dispersed wind power. Copyright © 2015 John Wiley & Sons, Ltd.     

Output power dispatch control for a wind farm in a small power system

Nowadays, a wind turbine generator (WTG) is required to provide control capabilities as the output power of WTG fluctuates. Under this scenario, this paper proposes an output power control method of a wind farm (WF) connected to a small power system using pitch angle control. In this control approach, the WF output power control is achieved by two control levels: central and local. In the central control, the WF output power command is determined by considering the frequency deviations and wind speeds using a fuzzy function. Then, the local output power commands for each of the WTGs are based on the proposed dispatch control. In the proposed dispatch control, the output commands of each WTG are determined by considering wind conditions for each of the WTGs. The simulation results by using an actual detailed model for the wind power system show the effectiveness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd.     

计及风电不确定性和风速相关性的微网孤岛多目标潮流优化

风电在微网渗透率不断增高,影响着微网的优化运行。文章针对风电不确定性和风电场之间相关性对微网的影响,提出了基于概率模型的微网孤岛多目标优化模型。分析了风机出力的不确定性和风速相关性,建立了相应的概率模型。建立了多目标模型,优化微网运行成本、总排放和电压偏移量。对文章应用的2PEM+1点估计法和Nataf变换进行了说明,用于模拟风电的相关性,并利用多目标蚁狮算法对建立的模型进行求解。在改进IEEE 33节点系统中进行仿真分析,对比说明了考虑风速相关性与风电场相关性对微网孤岛运行的影响。     

The effect of timescales on wind farm power variability with nonlinear model predictive control

Model predictive control techniques enable operators to balance multiple objectives in large wind farms, but the controller design depends on modeling effects that propagate at different timescales. This paper uses nonlinear model predictive control to investigate how wind farm power variability can be reduced both by varying ratios of three timescales impacting the system control and by inclusion of a power variability minimization measure in the controller objective function. Tests were conducted to assess how different timescale ratios affect the average farm power and power variability. Power variability measures are shown to be sensitive to the ratio of the incident wind period and the turbine time delay, particularly for cases with dominant incident wind frequencies. The average farm power increases in a series of steps as the controller time horizon increases, which corresponds to time horizon values required for wakes disturbances to propagate to downstream turbines. A second set of tests was conducted in which various measures of power variability were incorporated into the controller objective function and shown to yield significant reductions in farm power variability without significant reductions in farm power output. The controller was found to utilize two different approaches for achieving power variability reduction depending on the formulation of the controller objective function. These results have important implications for the design and operation of wind power plants, including the importance of considering the frequency components of wind during turbine siting and the potential to reduce power variability through the use of farm‐level coordinated control. Copyright © 2017 John Wiley & Sons, Ltd.     

Fault-tolerant control of an open-winding brushless doubly-fed wind power generator system with dual three-level converter

To improve the fault redundancy capability for the high reliability requirement of a brushless doubly-fed generation system applied to large offshore wind farms, the control winding of a brushless doubly-fed reluctance generator is designed as an open-winding structure. Consequently, the two ends of the control winding are connected via dual three-phase converters for the emerging open-winding structure. Therefore, a novel fault-tolerant control strategy based on the direct power control scheme is brought to focus in this paper. Based on the direct power control (DPC) strategy, the post-fault voltage vector selection method is explained in detail according to the fault types of the dual converters. The fault-tolerant control strategy proposed enables the open-winding brushless doubly-fed reluctance generator (BDFRG) system to operate normally in one, two, or three switches fault of the converter, simultaneously achieving power tracking control. The presented results verify the feasibility and validity of the scheme proposed.     

基于双电池不平衡状态优化的风功率平滑控制

在双电池平滑风功率过程中,改善双电池充放电不平衡状态可以提高充放电深度,减少充放电状态切换次数.文章分析了双电池风功率平滑系统的充放电不平衡状态及其产生的原因,提出了一种改进控制策略,该策略可根据双电池荷电状态调整风功率平抑目标功率,以此改善双电池不平衡状态.基于Matlab/Simulink分析了风速湍流强度以及风功...     

Effects of power reserve control on wind turbine structural loading

As the penetration of wind energy in worldwide electrical utility grids increases, there is a growing interest in the provision of active power control (APC) services from wind turbines and power plants to aid in maintaining grid stability. Recent research has focused on the design of active power controllers for wind turbines that can provide a range of APC services including inertial, primary frequency and secondary frequency control. An important consideration for implementing these controllers in practice is assessing their impact on the lifetime of wind turbine components. In this paper, the impact on the structural loads of a wind turbine providing a power reserve is explored by performing a load suite analysis for several torque‐based control strategies. Power reserve is required for providing those APC services that require the ability of the wind turbine to supply an increase in power. To study this, we performed a load suite on a simulated model of a research turbine located at the National Wind Technology Center at the National Renewable Energy Laboratory. Analysis of the results explores the effect of the different reserve strategies on turbine loading. In addition, field‐test data from the turbine itself are presented to augment and support the findings from the simulation study results. Results indicate that all power‐reserve strategies tend to decrease extreme loads and increase pitch actuation. Fatigue loads tend to be reduced in faster winds and increased in slower winds, but are dependent on reserve‐controller design. Copyright © 2015 John Wiley & Sons, Ltd.     

Adjustment of wind farm power output through flexible turbine operation using wind farm control

When the installed capacity of wind power becomes high, the power generated by wind farms can no longer simply be that dictated by the wind speed. With sufficiently high penetration, it will be necessary for wind farms to provide assistance with supply‐demand matching. The work presented here introduces a wind farm controller that regulates the power generated by the wind farm to match the grid requirements by causing the power generated by each turbine to be adjusted. Further, benefits include fast response to reach the wind farm power demanded, flexibility, little fluctuation in the wind farm power output and provision of synthetic inertia. Copyright © 2015 John Wiley & Sons, Ltd.