A simulation model for reliability evaluation of space stationpower systems

The dependence of reliability and storage characteristics during Sun and eclipse periods is considered. The charging and discharging of energy storage modules is included on a continuous basis. Sample system studies are also presented. The Monte Carlo analysis program for reliability analysis of a hybrid configuration can model the charging and discharging of energy storage devices in a more realistic manner than the approach of C. Singh et al. (1987). The results shown do not indicate any significant effect on computed reliability indices by this more refined modelling of charge/discharge of energy storage     

一种新的广义电力负荷模型及其工程应用

当区域负荷中含有较高比例的电源时,传统的经典负荷模型不适合描述负荷母线的动态行为.提出一种新的广义电力负荷模型,并给出模型参数的确定方法.该方法综合利用常规量测数据和PMU量测数据,其中等值发电机支路参数采用理论等值方法获得,而纯负荷参数采用辨识方法获取.实际工程应用表明,该广义电力负荷模型及其参数确定方法有效可行.     

考虑供电公司风险的激励性可中断负荷合同模型

考虑到供电公司的风险偏好及用户的可中断电量,应用委托代理及机制设计理论建立了一种用户类型离散的可中断负荷合同模型。分析和算例结果表明,无论供电公司的风险偏好如何,该合同模型均能引导用户披露真实信息,实现电力资源的有效配置,且供电公司能从中节约供电成本。因此,激励性可中断负荷合同不仅能提高用户需求弹性．还有助于供电公司回避市场风险。     

投影梯度法模糊层次综合评价模型在饱和负荷分析中的应用

提出了基于投影梯度法的模糊层次综合评价模型,对城市饱和负荷水平进行客观评价。根据评价指标体系,创建了判断矩阵和一致性指标函数。利用投影梯度法计算一致性指标函数最小值,检验、修正判断矩阵的一致性。通过调整判断矩阵的各评价因素标度改进了一致性指标值,优化了各评价因素的权重。计算结果表明:此算法是一类"主动"方法,计算权值误差小,计算稳定性强,克服了权重计算时主观性较强的缺陷,提高了评价结果的合理性。同时,以某市电网为研究对象,从社会因素、自然因素、经济因素3个方面,评价了该市负荷饱和水平,评价结果合理有效,具有良好的参考作用。     

A stochastic load model for an electricity market

This paper presents a stochastic load model that uses a regression equation coupled with a time series model. The model is simple but without compromising accuracy. A 24-h set of regression equations incorporates the hourly temperature variations. Weekly seasonality is handled by providing weekday and weekend non-linear regression equations. The Levenberg–Marquard method is used because of its superiority over the widely used Gauss–Newton and steepest descent methods in estimating model parameters and to avoid “slow down” in the search process, respectively. A residual discrete time series is determined by using the autoregressive integrated moving average (ARIMA) model. Test results using PJM-market load data indicate the effectiveness of the proposed model to predict the daily electricity load.     

变压器有载合闸的非线性数学模型及仿真

已提出的变压器有载合闸模型,都是将时变的励磁电感进行线性化或分段线性化处理,这种处理方式不能光滑地反映铁芯的非线性特征,造成仿真误差。建立了一个比较合理且精确的变压器有载合闸的非线性数学模型,铁芯的励磁特性采用了多值磁滞特性。根据该模型建立各支路电流的状态方程,并通过数字实时仿真证明了目前各种采用涌流特征进行闭锁的变压器差动保护经历带负载合闸时,尤其是在外部故障切除后电压恢复过程中受超饱和现象的影响,存在误动的可能性,指出应规定不推荐进行变压器有载合闸。进一步验证了变压器差动保护原理的局限性。     

灰色模型在电力负荷预测中的应用与改进

灰色GM(1,1)模型是一种较有效的负荷预测模型,然而由于电力负荷具有多样性,当负荷增长曲线不是G型时,其预测误差较大,精度不能满足要求,在实际应用中具有一定的局限性。对灰色GM(1,1)模型进行必要的改进,通过实例分析,利用等维新息递推模型、组合灰色模型进行负荷预测,可大大提高预测精度。     

A model for predicting motor load for an armored face-conveyordrive

A formula for calculating the power requirements of an armored face conveyor (e.g. for coal mining applications) is presented. Techniques to determine the conveyor speed-torque curve and to estimate the acceleration time for a loaded conveyor are also given. Using this information, an algorithm to estimate the maximum length for a face conveyor is developed. An application of the algorithm to power system analysis is presented. By using the developed algorithm, the performance as well as the maximum length of a longwall face conveyor can be readily evaluated     

电力负荷预测的最优分段校正模型研究及应用

中长期电力负荷同时具有增长性和波动转折性的二重趋势，这使得电力负荷的变化呈现出复杂的非线性特征。传统的中长期负荷预测模型仅考虑一种变化趋势，从而预测效果较差，不能符合实际需要。为了提高预测精度，更精确地反映负荷变化规律，通过改变GM(1，1)模型中微分方程的初始条件，且对历史负荷进行最优分段，在此基础上建立了电力负荷预测的最优分段校正模型，使模型具有二重趋势性特点。通过实例验证，较大提高了预测精度。     

A class of models for load management application and evaluationrevisited

The problem of load modeling for demand side management (DSM) purposes is addressed. The proposed load models rely on information about both the physical characteristics of elemental load devices at the distribution level and usage statistics of these devices. Although the class of models discussed has been previously proposed in the literature, its suitability for DSM purposes is definitely established by showing how the models can be a tool for real DSM actions evaluation. Some results are shown     

A dynamic load model for analysis of power system voltage

It has become important in recent years that power systems be protected from voltage instability caused, in part, by heavy loads and the concentration of air conditioning loads during certain hours. Many studies have explored the problems and possible countermeasures. However, the load representations used in these studies are based on power values, i.e., P and Q; therefore, these analytic models are insufficient to express load responses and, thus, investigation is somewhat limited. This paper introduces a load model expressing load admittance responses by a first-order delay differential equation and uses this model in tandem with power network solutions to analyze power system voltage stability. This load model is shown to work reliably and effectively. Using this model, it is possible to investigate more precisely and widely than before the power system voltage stability phenomenon of arbitrary characteristic loads in lower voltage ranges and on propagations of instability through the networks.     

A unified three-phase transformer model for distribution load flow calculations

This paper provides a unified method to model three-phase transformers for distribution system load flow calculations, especially when the matrix singularity caused by the transformer configuration arises. This paper shows that the singularity appears only in certain transformer admittance submatrices and only in certain transformer configurations. The unified method presented in this paper can solve the voltage/current equations in the forward/backward sweep algorithm for various types of transformer configurations, whether or not the corresponding admittance submatrices are singular. Comprehensive comparisons have been made between the proposed approach and other methods. Test results demonstrate the validity and effectiveness of the proposed method.     

Generation/transmission power system reliability evaluation byMonte-Carlo simulation assuming a fuzzy load description

This paper presents a Monte-Carlo algorithm considering loads defined by fuzzy numbers. In this methodology states are sampled according to the probabilistic models governing the life cycle of system components while fuzzy concepts are used to model uncertainty related to future load behavior. This model can be used to evaluate generation/transmission power system reliability for long term planning studies as one uses the more adequate uncertainty models for each type of data. For each sampled state a fuzzy optimal power flow is run so that one builds its power nor supplied membership function. The paper proposes new indices reflecting the integration of probabilistic models and fuzzy concepts and discusses the application of variance reduction techniques if loads are defined by fuzzy numbers. A case-study based on the IEEE 30 bus system illustrates this methodology     

A simplified inverter model for on-line control and simulation

A simplified fundamental component model for sine triangle comparison pulse width modulation (PWM) inverters operating in the transition region is presented. The model is evaluated through experimental verification and bv comparing it with detailed simulations of AC motor drives. Results from a real time control application show that the model compensates for the reduced inverter gain due to bus voltage variation and operation in the pulse dropping region. Finally. a technique for third harmonic injection in a current regulated PWM (CRPWM) inverter is demonstrated. providing the incentive to investigate a simplified inverter model that incorporates third-harmonic effects     

Construction of dynamic fluctuation load model and simulation with AFC control of BTB interconnection

AFC control of BTB active power flow, which is in phase with frequency deviations both in the Hokuriku AC power system and in the rest of the power system of central and western Japan, can effectively reduce frequency fluctuations. In the first section of this paper, test measurements of real large‐scale power system fluctuation loads are presented and a dynamic fluctuation load model is derived from a study of the test results. We then analyze the effectiveness of this AFC control in reducing frequency fluctuations in the two AC power systems by static and dynamic computational simulations, using our model in MATLAB. Our simulation analyses reveal that the effectiveness of frequency fluctuation reduction by AFC control on BTB active power depends on the capacity scale of the AC power system interconnected with the BTB system. We performed these computations for different states of the power systems, representing summer peak, winter peak, typical spring peak, and summer night conditions. We confirmed that frequency fluctuations can be significantly reduced in a smaller capacity power system by setting a larger AFC gain. © 2001 Scripta Technica, Electr Eng Jpn, 136(4): 15–25, 2001     

基于负载变化的PEMFC非线性动态模型建立

通过分析燃料电池的内部结构和工作原理,选取适当输入输出变量,建立质子交换膜燃料电池非线性状态空间模型。该模型的建立能反映燃料电池输出特性(输出电压、电流等)与操作条件(温度、湿度及压力等)之间的联系,把动态的非线性微分方程转化成等价的状态空间方程,为控制研究、数据处理和优化等方面提供便利,为性能诊断及输出特性优化提供了一定的理论依据。     

基于概率统计的电动汽车充电功率建模

电动汽车大规模应用以后,其充电功率将对电网产生一定影响。通过详细考虑电动汽车接入电网的因素,并在一定假设条件下,建立了电动汽车充电功率模型。采用蒙特卡洛仿真算法产生影响因素的随机数,仿真出电动汽车充电负荷曲线。以一居民小区夏季典型日负荷曲线为例,计算得出自由充电模式下电动汽车对原负荷曲线的影响。计算结果表明,电动汽车的自由充电特性将使电网最大负荷发生一定增长,在改变电动汽车起始充电时刻的情况下,电动汽车充电对于可再生能源具有一定的支撑作用。     

A linear programming model for reducing system peak throughcustomer load control programs

A linear programming (LP) model has been developed to optimize the amount of power system peak load reduction through scheduling of control periods in commercial/industrial and residential load control programs at Florida Power and Light Company, USA. The LP model can be used to determine both long and short term control scheduling strategies and for planning the number of customers which should be enrolled in each program. Results of applying the model to a forecasted late 1990s summer peak day load shape are presented. It is concluded that LP solutions provide a relatively inexpensive and powerful approach to planning and scheduling load control. Also, it is not necessary to model completely general scheduling of control periods in order to obtain near best solutions to peak load reduction     

改进光伏模型及其在微网可靠性评估中的应用

新能源发电系统的准确建模是分析新能源并网稳定性、安全性与可靠性等方面影响的关键因素。针对光伏发电系统可靠性影响分析,本文在详细分析现有光伏发电系统可靠性模型优缺点与适用范围的基础上,提出了一种综合考虑容量、温度及辐照度等运行条件约束的改进模型。为分析其对微电网可靠性评估的影响,设计了基于时序蒙特卡罗状态抽样法的可靠性评估流程,并对含光伏发电系统的微网进行了可靠性评估验证。理论分析与评估结果表明,改进模型使得评估结果更为严格,且实际输出功率方差较之现有模型有所减小,能在一定程度上加快蒙特卡罗法评估的收敛速度。     

Estimation of load model parameters for harmonic analysis

In order to devise countermeasures for harmonic disturbances and harmonic suppression in power systems effectively, it is necessary to develop a harmonic analysis approach with high accuracy. The major harmonic analysis approach is to re‐create harmonic distribution in a power system model by using a simulation method. However, in order to carry out high‐accuracy estimation of the harmonic distribution using the simulation method, after creating a load model which consists of several parameters associated with the measured harmonic impedance, the optimal load model parameters must be determined. So far, appropriate load model parameters have been determined by trial and error. Therefore, a systematic approach to determine the optimal load model parameters is needed to estimate the measured harmonic impedance with high accuracy. In this paper, a determination method for the optimal load model parameters to estimate the measured harmonic impedance is proposed. The proposed method is based on Particle Swarm Optimization (PSO), which is one of the optimization methods using the concept of swarm intelligence. In order to check the validity of the proposed method, the load model parameters estimated by the proposed method are evaluated using test data and field data of Hokuriku Electric Power Co. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 44–53, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20415