An evaluation method for power transfer capability enhanced by lightning countermeasures

Various countermeasures are taken against lightning faults in power transmission lines to decrease their occurrence and improve transmission reliability. However, how much they enhance the power transfer capability has not yet been quantitatively evaluated. The conventional deterministic approach, which is widely used in power system planning methodology, is inadequate to deal with this issue. This paper proposes a new method for numerically defining the power transfer capability enhanced by countermeasures against lightning. The proposed method is based on a probabilistic approach in which several fault patterns are taken into consideration with their occurrence frequency and maximum transferable power. This paper also gives an example application of the proposed method to a model trunk transmission system. The effect of a third overhead ground wire on the increase of transfer capability of a 500 kV transmission line has been quantitatively evaluated.     

A two-point estimate method for uncertainty modeling in multi-objective optimal reactive power dispatch problem

Due to nonlinear and discrete variables and constraints, optimal reactive power dispatch (ORPD) is a complex optimization problem in power systems. In this paper, the purpose is to solve multi objective ORPD (MO-ORPD) problem considering bus voltage limits, the limits of branches power flow, generators voltages, transformers tap changers and the amount of compensation on weak buses. The objectives of this paper are real power losses and voltage deviations from their corresponding nominal values, which are conflicting objectives. Because of the stochastic behavior of loads, the MO-ORPD problem requires a probabilistic approach. Hence, in this paper, a two-point estimate method (TPEM) is proposed to model the load uncertainty in MO-ORPD problem. Moreover, the proposed method is compared with some other methods such as deterministic approaches and Monte Carlo simulations (MCS). The obtained results approve the efficiency of the proposed methodology. The proposed models are implemented and solved using GAMS optimization package and verified using IEEE 14-bus and IEEE 30-bus standard test systems.     

Determination of transfer capability region using boundary tracing method

In electricity markets, transfer capability is a parameter showing the potential of a considered source–sink pair to transfer power. This paper enhances transfer capability monitoring by proposing a method to determine this parameter with respect to a region referred to as the ‘transfer capability region’ (TCR). The boundary of a TCR is traced by using the modified predictor–corrector process on a plane of real and reactive powers. The TCR shows a set of feasible loading points at the sink area. Moreover, the shape of TCR always changes according to the system parameters. This paper also defines the outermost boundary of the TCR when the considered parameters are set to be free. We apply the proposed method to test systems, and then compare to the maximum loading points obtained by the conventional transfer capability calculation. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑电压和热稳定约束的可利用传输能力的快速算法

在现代电力市场环境,可利用传输能力(ATC)需要尽快提供给使用方。而在计算中要考虑的所有N-1故障因素导致了ATC计算任务非常繁重。基于此,提出了一种应用故障过滤与排序技术的ATC快速计算方法。首先,采用迭代线性潮流法(ILPF)对电网的N-1故障进行排序以筛选出热稳定极限和电压幅值约束条件下最严重的故障情况;然后,应用原始-对偶内点法对最严重故障情况进行ATC的计算,解决了ATC计算的耗时问题。算法的有效性通过IEEE30母线系统的仿真得到了验证。     

考虑电压和热稳定约束的可利用传输能力的快速算法

在现代电力市场环境,可利用传输能力(ATC)需要尽快提供给使用方.而在计算中要考虑的所有N-1故障因素导致了ATC计算任务非常繁重.基于此,提出了一种应用故障过滤与排序技术的ATC快速计算方法.首先,采用迭代线性潮流法(ILPF)对电网的N-1故障进行排序以筛选出热稳定极限和电压幅值约束条件下最严重的故障情况;然后,应用原始-对偶内点法对最严重故障情况进行ATC的计算,解决了ATC计算的耗时问题.算法的有效性通过IEEE30母线系统的仿真得到了验证.     

A new method for evaluation of the load transfer capability of trunk power networks

Today, a more effective power network is a key solution to the right‐of‐way problem in terms of transmission cost reduction. Various advanced techniques and planning methods are currently adopted in power utilities for this purpose. So far, the authors have presented two approaches for the rational coordination of transfer capability with transmission reliability. One is a method for numerical evaluation of the increase in critical transferable power resulting from lightning countermeasures on a long transmission route. The other is an index of the system margin to be uniformly allocated in a power system from the adequacy point of view. This paper proposes a new concept of system margin from the dynamic stability point of view and a new definition of probabilistic load transfer capability, both aiming for quantitative evaluation of power system alternative plans. Several different fault patterns have been taken into account, with their associated occurrence frequency and critical transferable power. These proposals are applicable to the practices of power utilities in conjunction with the conventional planning methods. This paper also illustrates numerical examples of the proposed methods as applied to a 500‐kV trunk model power system. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 17–25, 1999     

Total transfer capability computation for multi-area power systems

This paper presents a method for multi-area power system total transfer capability (TTC) computation. This computation takes into account the limits on the line flows, bus voltage magnitude, generator reactive power, voltage stability, as well as the loss of line contingencies. The multi-area TTC problem is solved by using a network decomposition approach based on REI-type network equivalents. Each area uses REI equivalents of external areas to compute its TTC via the continuation power flow (CPF). The choice and updating procedure for the continuation parameter employed by the CPF is implemented in a distributed but coordinated manner. The proposed method leads to potential gains in the computational efficiency with limited data exchanges between areas. The developed procedure is successfully applied to the three-area IEEE 118-bus test system. Numerical comparisons between the integrated and the proposed multi-area solutions are presented for validation.     

输电系统可用传输能力的研究

针对电力工业市场化改革的需求，综述了在电力市场环境下，输电网可用输电能力ATC（Available Transfer Capability)计算问题的研究现状及发展方向，介绍了ATC的定义，分析限影响ATC准确计算的各种不确定因素，针对ATC在线计算和离线计算的特点，提出了ATC计算的确定性模型和概率性模型，分析比较了目前ATC计算的几种算法的优,缺点，最后，展望了输电网可用输电能力计算中有价值的研究方向。     

A stochastic embedding approach for quantifying uncertainty in the estimation of restricted complexity models

This paper presents a new approach to the understanding and treatment of the effects of undermodelling in the estimation of models for dynamical systems. There already exists a substantial body of knowledge dealing with the implications of undermodelling on robust control system design. However, the corresponding problem for model estimation has received only scant attention. This paper presents a general conceptual and philosophical framework which adds the important dimension of undermodelling to the estimation problem. The philosophy of the approach is to embed the nominal model structure into a larger class of models which includes a generic characterization of undermodelling. This broader perspective allows the effects of limited model complexity on estimation to be quantified. The implications of these results are believed to be wide-ranging and include new insights into the role of user choices and experimental conditions in estimation, integration of robust and adaptive control, new strategies for fault detection and diagnosis, and so on.     

Error-space estimate method for generalized synergic target tracking

To improve the tracking accuracy and stability of an optic-electronic target tracking system, the concept of generalized synergic target and an algorithm named error-space estimate method is presented. In this algorithm, the motion of target is described by guide data and guide errors, and then the maneuver of the target is separated into guide data and guide errors to reduce the maneuver level. Then state estimate is implemented in target state-space and error-space respectively, and the prediction data of target position are acquired by synthesizing the filtering data from target state-space according to kinematic model and the prediction data from errorspace according to guide error model. Differing from typical multi-model method, the kinematic and guide error models work concurrently rather than switch between models. Experiment results show that the performance of the algorithm is better than Kalman filter and strong tracking filter at the same maneuver level. __________ Translated from Journal of University of Electronic Science and Technology of China, 2007, 36(2): 217–219 [译自: 电子科技大学学报]     

Available transfer capability and first order sensitivity

A method of calculating available transfer capability and the exploration of the first order effects of certain power system network variables are described. The Federal Energy Regulatory Commission has ordered that bulk electrical control areas must provide to market participants a “commercially viable” network transfer capability for the import, export and throughput of energy. A practical method for deriving this transfer capability utilizing both linear and nonlinear power flow analysis methods is developed that acknowledges both thermal and voltage system limitations. The available transfer capability is the incremental transfer capability derived by the method reduced by margins. A procedure for quantifying the first order effect of network uncertainties such as load forecast error and simultaneous transfers on the calculated transfer capability of a power system snapshot are explored. The quantification of these network uncertainties can provide information necessary for system operation, planning and energy market participation     

Probabilistic approach to available transfer capability calculation

This paper suggests a probabilistic approach to calculate available transfer capability in the interconnected network. Calculation of available transfer capability is complicated because it involves determination of total transfer capability, transmission reliability margin and capacity benefit margin.In the suggested available transfer capability quantification method, total transfer capability is determined by the continuation power flow process. Transmission reliability margin and capacity benefit margin are evaluated by probabilistic load flow and Monte Carlo simulation, respectively.Proposed method is applied to a modified IEEE 72-bus 3-area system to calculate available transfer capability on two different time spans. Results of the case study show that suggested probabilistic approach can offer operational flexibility for system operators to consider system and market uncertainties.     

含VSC-HVDC的交直流系统可用输电能力计算

利用等值电压源方法对电压源换流器进行等效,从而导出了适合于优化计算的电压源换流器型直流输电(VSC-HVDC)系统模型。该模型能够考虑换流器的各种控制方式及运行限制,且可用于多端直流系统。建立了含有VSC-HVDC的交直流系统可用输电能力计算模型,在模型中考虑了对换流器控制变量的多种优化方式,并应用序列二次规划法对模型进行求解。通过对修改后的EPRI-36节点交直流系统进行仿真计算,验证了所提出模型的实用性及算法的有效性。     

交直流系统可利用传输能力的评估

提出了一种基于内点法的适用于交直流系统求解可利用传输能力的新方法。由交直流网络间的耦合关系和换流器转换方程, 推导出直角坐标系交直流系统的Jacobi、Hessian 矩阵, 进而用原始-对偶内点法求解计及电压幅值和热稳定约束的交直流系统ATC。针对静态电压稳定约束下交直流系统直流控制方式会发生调整的情况, 提出分段求解交直流系统ATC的方法, 该方法能方便考虑直流变量约束及运行方式的调整。经算例验证该算法在交直流系统ATC计算中对初始值选择要求不高, 收敛迅速。     

交直流系统可利用传输能力的评估

提出了一种基于内点法的适用于交直流系统求解可利用传输能力的新方法.由交直流网络间的耦合关系和换流器转换方程,推导出直角坐标系交直流系统的Jacobi、Hessian矩阵,进而用原始-对偶内点法求解计及电压幅值和热稳定约束的交直流系统ATC.针对静态电压稳定约束下交直流系统直流控制方式会发生调整的情况,提出分段求解交直流系统ATC的方法,该方法能方便考虑直流变量约束及运行方式的调整.经算例验证该算法在交直流系统ATC计算中对初始值选择要求不高,收敛迅速.     

含VSC-HVDC的交直流系统可用输电能力计算

利用等值电压源方法对电压源换流器进行等效,从而导出了适合于优化计算的电压源换流器型直流输电(VSC-HVDC)系统模型.该模型能够考虑换流器的各种控制方式及运行限制,且可用于多端直流系统.建立了含有VSC-HVDC的交直流系统可用输电能力计算模型,在模型中考虑了对换流器控制变量的多种优化方式,并应用序列二次规划法对模型进行求解.通过对修改后的EPRI-36节点交直流系统进行仿真计算,验证了所提出模型的实用性及算法的有效性.     

电力系统仿真仪不确定度评定方法

从继电保护的角度出发,以电力系统仿真仪为例,提出几种确定误差分量不确定度的方法,根据合成的标准差按正态分布计算总的不确定度.     

电力系统仿真仪不确定度评定方法

从继电保护的角度出发 ,以电力系统仿真仪为例 ,提出几种确定误差分量不确定度的方法 ,根据合成的标准差按正态分布计算总的不确定度。     

Assessment of available transfer capability of transmission systems

The available transfer capability (ATC) of a transmission system is a measure of unutilized capability of the system at a given time and depends on a number of factors such as the system generation dispatch, system load level, load distribution in the network, power transfers between areas, network topology, and the limits imposed on the transmission network due to thermal, voltage and stability considerations. This paper describes a method for determining the ATC between any two locations in a transmission system (single-area or multiarea) under a given set of system operating conditions. The method also provides ATCs for selected transmission paths between the two locations in the system and identifies the most limiting facilities in determining the network's ATC. In addition, the method can be used to compute multiple ATCs between more than one pair of locations. The proposed method is illustrated using the IEEE reliability test system (RTS)     

用随机规划法计算可用传输容量

该文提出了一种新颖的方法,来计算互联系统中通过预定界面的ATC(Availab1e Transfer Capability)值.它把电力系统中的不确定因素:发电机开断、线路开断和负荷预测误差,处理为随机变量,用基于随机规划法的混合方法,二阶段求索随机规划法和机会约束规划法求解.经过算例检验,此方法是有效的.