Output power leveling of wind turbine generators using pitch angle control for all operating regions in wind farm

Effective utilization of renewable energies such as wind energy instead of fossil fuels is desirable. Wind energy is not constant and windmill output is proportional to the cube of the wind speed, which causes the generated power of wind turbine generators (WTGs) to fluctuate. In order to reduce the output power fluctuation of wind farms, this paper presents an output power leveling control strategy for a wind farm based on both the average wind farm output power and the standard deviation of the wind farm output power, a cooperative control strategy for WTGs, and pitch angle control using a generalized predictive controller (GPC) in all WTG operating regions. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 31– 41, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20448     

Generated output increase control with consideration of the influence of wake for wind farm

Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore, wind generation companies want to increase the electric power output from wind farms (WFs). In this article, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reducing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurrence rate of the direction of the wind as a variable.     

Output power control of wind turbine generator by pitch angle control using minimum variance control

Effective utilization of renewable energies such as wind energy as a replacement for fossil fuels is highly desirable. Wind energy is not constant and wind generator output is proportional to the cube of the wind speed, which causes the power output of wind turbine generators (WTGs) to fluctuate. In order to reduce output power fluctuations of wind farms, this paper presents an output power leveling control strategy for wind farms based on both the mean and the standard deviation of wind farm output power, a cooperative control strategy for WTGs, and a pitch angle control method using a generalized predictive controller (GPC) intended for all operating regions of WTGs. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 10–18, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20247     

基于数据驱动方法的风电机组功率优化

风电机组功率与风电产能息息相关,为提高风电产能及其收益,有必要对风电机组功率进行优化。应用前馈神经网络,从历史运行数据中挖掘风电机组功率与风速和控制量间的函数关系,进而提出逐点优化策略和聚类优化策略,用于实现风电机组功率优化,即在已知测量风速时,优化确定风电机组控制量,实现风电机组功率最大化。后者优化策略在前者优化策略基础上,应用K均值聚类方法聚类风速,从而降低优化计算复杂度,利于风电机组功率的实时优化。定义平均功率增益、功率增益百分比和功率增益概率三种指标用于测度功率优化效果。将两种优化策略应用至H56-850型风电机组,将优化后的风电机组功率与历史运行记录进行对比,结果表明,两种优化策略均可有效提高风电机组功率输出。此外,聚类中心数为5的聚类优化策略,能以较低的优化计算复杂度,达到与逐点优化策略相近的优化效果。     

利用转子动能的风机辅助频率控制最优策略

风机增加辅助频率控制模块是解决新能源取代同步机导致的电力系统频率安全问题的一种方案,其中利用转子动能的调频模式可以使风机运行在最大功率点,经济性比功率备用模式更好。已有研究主要让风机通过虚拟惯量和频率下垂控制模拟同步机,却未充分利用风机控制灵活、可塑性强的优点,且未考虑风机转子动能限制及系统频率二次跌落。论文跳出虚拟惯量加频率下垂控制的传统框架,提出利用转子动能的风机辅助频率控制最优策略。首先将风机输出功率曲线作为决策变量,通过优化得到最优功率曲线,然后设计对应的辅助频率控制策略,实现最优输出功率曲线。仿真结果验证所提策略的效果,并说明风机辅助频率控制不应局限于模拟同步机,而是有更优的策略。     

A study of the flywheel capacity of the power compensator for the wind turbine generator

Nowadays, the Wind Turbine Generator (WTG) system is remarkably increasing as a renewable energy resource in Japan. But in the WTG, the power fluctuations caused by the wind speed fluctuation are the most crucial issue in providing their energy to the utility. It was found that a power compensation system (PCS) of suitable capacity is not yet available. In this paper, the time range and standardized wind speed including fluctuations are discussed. We estimated the storage capacity of PCS at different wind profiles by standardization of wind speed and verified the validity of their capacities using a computer simulation. In this way we determined the suitable capacity of the power compensation system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(4): 64–71, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10122     

Stabilization control for multimachine system using decentralized H∞ excitation controller realizing terminal voltage control and damping control

In this paper, to achieve both damping of power system oscillation and terminal voltage control simultaneously on a multimachine power system, we propose a decentralized H_∞ excitation controller. In the proposed method, H_∞ control via the Normalized Coprime Factorization approach is used to achieve the proposed design idea. By the Normalized Coprime Factorization approach, the weighting function in H_∞ control design is simplified, and output feedback controllers that take into account the realities and constraints of the power systems are designed. The proposed controller is subjected to model reduction of H_∞ controllers, and is transformed to a discrete system to perform digital control by computer systems in consideration of application to a real system. We verify that the proposed excitation controller can achieve both damping of power system oscillation and terminal voltage control by computer simulations of a multimachine power system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 33–41, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10254     

A Robust H∞ Controller Based Gain-scheduled Approach for the Power Smoothing of Wind Turbine Generator with a Battery Energy Storage System

Output power fluctuation of the wind turbine generator is a serious issue for power systems. The battery energy storage system is installed to the power system to solve this problem. However, the large battery energy storage system can increase the capital cost of the wind turbine generator system. Hence, the capacity of the battery should be reduced as much as possible. This article presents an H_∞ based control method for the output power smoothing method of the wind turbine generator by using a battery energy storage system. The output power fluctuation of the wind turbine generator is considered in the frequency domain. Low-frequency fluctuations are smoothed by pitch angle control of the wind turbine generator, while high-frequency variations are smoothed by charge or discharge of the battery energy storage system, respectively. The battery energy storage system’s capacity and mechanical stress of wind turbine blades can be reduced by the proposed method. In addition, the gain-scheduled control theory is applied to the pitch angle control system of the wind turbine generator. Therefore, the robust control performance for high non-linearities of the wind turbine generator model can be achieved. The effectiveness of the proposed method is validated by numerical simulations.     

基于模糊控制的混合储能平抑风电功率波动

风电功率波动对电网造成不容忽视的影响。风电并网处加入混合储能系统可以有效地降低风电对电网的影响。首先按照风电并网波动量要求,估算出某时刻的预估风电波动量。然后根据风电预估波动功率以及电池当前的能量状态建立模糊控制器,输出平抑系数K1,并计算出混合储能系统的实际输出功率以及风储并网功率。最后利用需混合储能SOE变化量以及超级电容器当前能量状态,建立模糊控制器,输出分配系数K2,计算当前超级电容器和电池的实际输出功率,并实时更新混合储能的能量状态。通过算例证明,在混合储能容量充足和不足的情况下协调控制算法均可靠、有效,并且能够充分解决混合储能使用寿命和风电功率波动平抑度之间的矛盾。     

考虑风力发电影响的配电网可靠性评估

风力发电机(wind power generation,WTG)凭借其发电灵活、环境友好等优势被越来越多地接入到配电网中,这给传统配电网的可靠性评估带来了一定影响。充分考虑风力间歇性、随机性的特点,提出了一种利用1a内的统计风速信息,根据WTG的功率特性曲线获得其输出功率,从而得到WTG的多状态模型的方法。在此基础上,采用改进最小割集算法对含WTG的配电网进行可靠性评估。以IEEE-RBTS 6母线系统为例,计算了WTG接入前后可靠性评估的各项指标,验证了WTG在改善电网可靠性方面的作用。     

Optimal allocation of wind turbine generator in active distribution network

Nowadays, more and more wind turbine generators (WTGs ) are being integrated into power systems. In this paper, an optimal WTG allocation model with the objective of minimizing the annual cost is proposed. The model can take into account the time‐sequential correlation between the wind speed and load demand, as well as four kinds of active management measures, i.e. regulating the on‐load tap changer of the transformer, curtailing the output power of WTG , regulating the power factor of WTG , and managing the demand side. The time‐sequential correlation is handled by the joint probability distribution method. A hybrid solving strategy combining the fuzzy adaptive particle swarm optimization algorithm and primal‐dual interior point method is developed to get the optimal solutions. Case studies carried out on the IEEE 33‐bus active distribution network verify the feasibility of the developed model and the high efficiency of the proposed solving strategy. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

风力发电为主导的孤立发电系统可靠性评估

针对内蒙古的特定情况,采用以风力发电为主导的小型孤立发电系统提供电能,可保证供电可靠性、节省柴油燃料和保护当地的生态环境。本文所述的小型孤立发电系统以风/柴/储能联合发电的形式提供电能。文章采用序贯Monte-Carlo模拟法实现风/柴/储能发电系统的可靠性评估。根据风电场的风速历史数据,建立风电场的风速时间序列模型。由风速时间序列计算风力发电机的输出功率。在考虑机组随机故障的情况下,由发电机和负荷模型得到蓄电池的时间序列模型。针对样例系统,量化评估了仿真样本容量、蓄电池容量、蓄电池充放电率和风力发电机额定功率等,一些因素对风/柴/储能发电系统可靠性的影响。仿真结果可为风/柴/储能发电系统可靠运行提供依据,为政府及电力部门推广风/柴/储能联合发电向偏远地区供电提供依据。     

A method for load frequency control using battery in power system with highly penetrated photovoltaic generation

It is generally believed that large battery systems will be needed to store surplus electric energy due to the high penetration of renewable energy (RE) such as photovoltaic generation (PV). Since the main objective of high penetration of RE is to reduce CO₂ emissions, reducing kWh output of thermal generation that emits large amounts of CO₂ in power systems should be sufficiently considered. However, thermal generation plays an important role in load frequency control (LFC) of power systems. Therefore, if LFC could be performed with batteries and hydropower generation, the kWh output of thermal generation could be reduced significantly. This paper presents a method of LFC using batteries in a power system with highly penetrated PVs. An assessment of the effect of the proposed method considering mutual smoothing effect of highly penetrated PVs is made. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(4): 22–31, 2013; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22425     

清洁度在风力机生命周期环境评价中的作用

风能是可再生清洁能源,但对于风力发电,在发电设备制造和风力发电场的建设过程中,会对环境产生污染和破坏为评价风力机生命周期内的环境效益,提出了能源利用技术中的一个新概念——清洁度介绍了清洁度系数的定义和计算方法,分析了该参数的物理意义,并得出结论：提高风力机清洁度的主要手段包括合理选择风场、提高发电效率、延长风力机使用寿命和有效运行时间,以及减少其它能量消耗等。     

基于双目标时变交集的电池储能改善风电场出力控制

为了抑制风电随机波动和提高风电超短期预测精度,提出了一种基于此双目标时变交集的电池储能控制方法。首先,分别制定了抑制风电波动、提高风电预测精度的单一控制域及此双目标的交集联合控制域,并在考虑两种单一控制目标的时间尺度不同后,制定了随时间变化的双目标交集联合控制域。在此基础之上,结合储能运行约束条件确定了最终的电池储能改善风电场出力控制策略。其次,首次建立了基于越限比和越限相对均值的波动与预测精度评估指标并形成了双目标综合评估体系。最后,应用某风电场实际出力数据,分别在采用神经网络时间序列和差分自回归滑动平均(ARIMA)两种预测模型的前提下,考虑电网对风电波动忍受度和超短期预测误差忍受度的三种大小关系,通过计算波动量总和与均方根误差验证了所建立评估指标的有效性,同时证实了应用该控制策略的电池储能系统能够同时达到抑制风电随机波动和提高风电超短期预测精度两个目标。     

Optimal siting and sizing of intermittent distributed generators in distribution system

Intermittent distributed generators (IDGs), such as distributed wind turbine generator (WTG) and photovoltaic generator (PVG), have been developing rapidly in recent years. The output power of WTG and PVG highly depends on the wind speed and illumination intensity, respectively. There always exist correlations among the wind speed, illumination intensity, and bus load, which could have significant influence on the determination of siting and sizing of IDGs in distribution system. Given this background, a chance‐constrained‐programming‐based IDGs planning model, which can take into account the correlations, is developed in this paper. Latin hypercube sampling technique and Cholesky decomposition are introduced to handle the correlations. A Monte Carlo simulation‐embedded multi‐population differential evolution algorithm is employed to solve the developed model. Case studies carried out on the Baran & Wu 33‐bus distribution system verify the feasibility of the developed model and effectiveness of the proposed solving methodology. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑风电降载的电力系统鲁棒备用调度模型

风电主动控制可抑制风电出力的波动,有效缓解系统备用压力。文中提出了一种考虑风电降载的电力系统鲁棒备用调度模型,考虑风电场和负荷功率预测误差的不确定性,引入风电降载比定量描述风电备用持有水平,建立风电场备用、旋转备用等鲁棒约束条件,同时根据对偶原理将鲁棒优化模型转化为确定性的数学规划问题,利用线性松弛技术和空间分支定界法寻找模型的全局最优解。最后,采用改进的IEEE 39节点算例验证模型的有效性。     

Sensorless vector controlled converter for variable speed wind generation system using an induction generator

This paper proposed two types of speed sensorless converters that can control rotational speed and electric power. One is based on a slip frequency control system. The other is based on a vector control system. The rotational speed of the wind turbine is estimated with the phase voltage and phase current of the induction generator by the adaptive rotor flux observer. The estimated wind turbine rotational speed ω_r^est is used as the feedback of the speed control loop in the converter control system. Also, the estimated rotor flux ?_2d^est is used for the vector control. The simulation results confirm that both of them perform satisfactorily under the speed sensorless operation. The method based on the vector control system generates more electrical energy than does the method based on the slip frequency control system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 62–75, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20323     

Matching between straight‐wing nonarticulated vertical axis wind turbine and a new wind turbine generator

In the current wind turbine generation system, there are substantial problems such as the fact that the maximum power of the wind turbine cannot be obtained in the presence of fluctuating wind speed, as well as high cost and low annual net electricity production (due to mismatch between generators and wind turbines). A new wind turbine generator optimized for the wind turbine output is presented in order to solve such problems. This wind turbine generator consists of a permanent magnet generator, a reactor, and a rectifier, and uses neither a control circuit which requires standby electricity nor a PWM converter having a switching element. By selecting the most appropriate combination of a permanent magnet generator with multiple windings and a reactor connected in series with each winding, the maximum output of the wind turbine can be obtained without using a control circuit. The new wind turbine generator was directly coupled with a straight‐wing nonarticulated vertical‐axis wind turbine (SW‐VAWT), and matching of the generator with the wind turbine was examined in field tests. The test results and review confirm that the new wind turbine generator is highly matched with the wind turbine in the presence of fluctuating wind speed. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(2): 26–35, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21036     

A study of a two‐stage maximum power point tracking control of a photovoltaic system under partially shaded insolation conditions

A photovoltaic (PV) array shows relatively low output power density, and has a greatly drooping current–voltage (I–V) characteristic. Therefore, Maximum Power Point Tracking (MPPT) control is used to maximize the output power of the PV array. Many papers have been reported in relation to MPPT. However, the current–power (I–P) curve sometimes shows multi‐local maximum power points mode under nonuniform insolation conditions. The operating point of the PV system tends to converge to a local maximum output power point which is not the real maximal output point on the I–P curve. Some papers have tried to avoid this difficulty. However, most of those control systems become rather complicated. The two‐stage MPPT control method is proposed in this paper to realize a relatively simple control system which can track the real maximum power point even under nonuniform insolation conditions. The feasibility of this control concept is confirmed for steady insolation as well as for rapidly changing insolation by simulation study using software PSIM and LabVIEW. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(4): 39–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20188