Unit commitment taking into account reactive power

In this paper, the Voltage Magnitude Constrained OPF (VMC‐OPF) algorithm to determine the reactive power injection from compensating equipment to load bus is developed. By introducing the proposed VMC‐OPF to the real power related Unit Commitment (UC) [1], a novel daily UC method taking into account the reactive power to secure bus voltage magnitude is presented. The Transmission Access Charge (TAC) and Ancillary Services Charge (ASC) are included in the objective function for considering costs of using transmission network and supplying reactive power to maintain the voltage. Using the proposed UC, the difference between two schedules based on benefit maximization and cost minimization is also discussed. To ascertain the effectiveness of the proposed UC method, we demonstrate various simulation results for a model power system of IEEE‐118 bus system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(3): 17–26, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20590     

An efficient faults calculation method taking into account mutually coupled lines of power systems

It is necessary to take into account the effects of mutual couplings when unbalanced faults are to be calculated in transient stability study. When the method based on symmetrical coordinates is applied to faults calculation, it has been necessary in the conventional method to construct the zero sequence network, the configuration of which is more complex than other networks so far. Then, the application of faults calculation including mutual couplings to the analysis on the bulk power system model has been considerably difficult for a long time. This report presents a newly developed method to calculate the effects of mutual coupling in multifaults calculation under the same configuration and with no change for all sequence networks. The validity of the proposed method was verified through the application of transient stability analysis for power system models.     

Optimal network configuration of FRIENDS taking power supply reliability into account

FRIENDS (Flexible, Reliable and Intelligent ENergy Delivery System) is a new concept for a future power delivery system in which so‐called QCC (Quality Control Center) plays an important role to realize the customized power quality services and to connect a large number of distributed generators to distribution systems. In FRIENDS, QCCs are connected as a network through distribution cables to realize a reliable power supply. In this paper, a method to find the optimal network configuration of FRIENDS is proposed. The method can minimize the sum of facility installation cost and operational cost (distribution loss) under the constraint that the expected power interruption cost is less than a predetermined endurable value. The solution algorithm is based on tabu search, and employs a sensitivity analysis to select efficient facilities to be installed or to eliminate constraint violations. In the algorithm, single and double faults of power distribution system are taken into account to calculate the power supply reliability or expected power interruption cost. Several numerical real‐world examples are shown to demonstrate the validity of the algorithm. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(3): 32–40, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20264     

Algorithm for power system dynamic stability studies taking account of the variation of load power

This paper presents a probabilistic algorithm for determining the effect of initial state variation on the dynamic stability of power systems. Variation of operating conditions due to the uncertainties in load and generation is represented by the statistical attributes of nodal voltages. Expectation and covariance are employed to describe the distribution nature of random variables. The expected coefficient matrix in the state space equation is corrected by the second-order covariances. The solution gives the probabilistic distributions and conditional probabilities of eigenvalues. The proposed algorithm is examined on a two test systems.     

A new analytical method for analysis and design of Class E power amplifiers taking into account the switching device on resistance

The new analytical method presented in this paper extends the principle of the equivalent small parameter method (ESP, an improved perturbation technique) to analyse and design Class E power amplifiers. Using this method the analytical expression for the output voltage (or current), containing the fundamental frequency component, the second, third and other higher harmonics, can be obtained. Based on this analytical expression, the other analytical expressions which represent the performance of Class E power amplifiers, such as collector–emitter voltage and collector current of the switching transistor, the efficiency, the output power as well as the power‐output capability can also be obtained. This method is applicable to analyse Class E power amplifiers with any circuit configuration and parameters at any switching‐on duty cycle, and does also take into account the switching transistor ON resistance. It is valuable to the design of Class E amplifiers by offering designers insight into circuit behavior. Copyright © 1999 John Wiley & Sons, Ltd.     

计及风速扰动的含风电场电力系统相关性分析研究

针对风机接入电网对电力系统稳定性的影响,提出了一种利用相关分析的快速估计风电接入对系统关联程度影响的新方法,即通过创建风电机组模型研究风机转速与风速关系.仿真案例表明,采用该方法可以快速、有效地分析不同类型风速、不同接入地点风机对电力系统相关性的影响.     

计及需求侧储能事故备用风险与火电机组深度调峰的 经济优化研究

针对电网调峰过程中需求侧储能(Energy Storage, ES)事故备用闲置时间过长,以及传统火电机组深度调峰(Depth Peak Regulation, DPR)成本较高的问题,提出了一种考虑需求侧储能事故备用风险与火电机组深度调峰的经济优化方法。首先,通过分析天气状态、负载率水平以及故障风险类型等影响因素,构建了考虑需求侧的ES风险量化模型、ES事故备用调峰经济模型。其次,结合火电机组进行深度调峰时对机组损伤及燃料需求分析,构建了考虑火电机组投油成本的深度调峰经济模型。最后,提出了一种基于需求侧风险量化的ES事故备用辅助火电机组DPR的经济优化模型,采用粒子群优化算法在修正后的IEEE30节点系统中进行算例验证。结果表明ES事故备用参与DPR能有效提高电网调峰能力和ES事故备用利用率。     

Unit commitment scheduling by Lagrange relaxation method taking into account transmission losses

Since the application of the Lagrange relaxation method to the unit commitment scheduling by Muckstadt in 1979, many papers using this method have been published. The greatest advantage of applying the Lagrange relaxation method for the unit commitment problem is that it can relax (ignore) each generator's output dependency caused by the demand–supply balance constraint so that a unit commitment of each generator is determined independently by dynamic programming. However, when we introduce the transmission loss into the demand–supply balance constraint, we cannot decompose the problem into the partial problems in which each generator's unit commitment is determined independently and have to take some measures to obtain an optimal schedule by the Lagrange relaxation method directly. In this paper, we present an algorithm for the unit commitment schedule using the Lagrange relaxation method for the case of taking into account transmission losses. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 27–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20119     

Robust scheme of an indirect MRACS system taking into account the presence of deterministic disturbances

This paper presents a method for the design of an indirect model reference adaptive control (MRAC) system for a plant with deterministic disturbances, robust to modeling errors due to unmodeled dynamics and observation noise. In the proposed method, the structure of the controller is determined on the basis of the internal model principle to reject the deterministic disturbance, and its parameters are adjusted by using the estimated plant parameters. Robustness to the modeling errors is ensured by the use of the adaptive law with a dead zone and a fixed compensator of integral type. The adaptive law prevents the adjustable parameters from drifting and the fixed compensator improves the control performance degraded by the use of the dead zone. Stability of the MRAC system is analyzed using the concept of the ??_2δ norm and the Bellman–Gronwall lemma, based on the properties guaranteed by the adaptive law. Effectiveness of the proposed method is demonstrated by the simulation carried out for a plant with second‐order nominal part and a step disturbance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 65–75, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10190     

考虑输电网络影响的火电机组优化组合的一种实用算法

提出一种考虑输电网络损耗及线路过负荷的火电机组优化组合的实用算法。用动态规划法建立一个初始解,运用启发式手法对初始解进行修正,使之逐个满足各约束条件,得到运行可能解,并通过更新发电机起动优先顺序使此过程反复进行直至得到(准)最佳解。在求解过程中引入最优潮流计算,使考虑输电网络损耗及线路过负荷等网络因素对发电机组优化组合的影响成为可能,并提出一种调节发电机出力和改变发电机组合相结合的消除线路过负荷的方法。在IEEE-118母线(36机)系统上对所提出的算法进行了各种条件下的仿真计算,考察了网络损耗及线路过负荷对发电机组优化组合的影响,验证了所提算法对解决考虑输电网络因素影响的发电机组优化组合问题的有效性。     

A method for experimental determination of defectiveness in the insulation system of induction motor windings taking into account different mechanisms of the production of defects

The existing methods for determining the defectiveness in the winding insulation during the run-in period are analyzed. The methods based on testing the breakdown of the insulation extracted from slots of unimpregnated stators are considered. A method for experimental determination of defectiveness in the insulation systems of impregnated windings of induction motors is proposed. This method takes into account different mechanisms of the production of flaws. A design of the winding models for conducting accelerated tests is developed.     

Design of a minimum sensitivity controller for a power system under different operating conditions taking into account the effect of local load characteristics

The effect of local load characteristics on synchronous machine stability has been studied using the analytical expressions developed for damping and synchronizing torques. The inclusion of system loads may lead to instability conditions due to negative damping. Improvement of power system stability can be achieved by sending an additional signal from an optimal pole placer controller to the input of the excitation and mechanical systems of the synchronous machines. The proposed pole placer can allocate the sytem poles to desired prescribed locations while ensuring minimum sensitivity of such poles to operating condition variations over a wide range. Controller parameters are determined by minimization of an objective function using the Powell—Botm optimization routine. Time response simulations are used to illustrate the dynamic behavior of the controlled system with wide variations of operating conditions, different local load characteristics and various exciter gains.     

Estimation of remaining service life taking microdamage into account

Results from a strength calculation are correlated with the structural changes occurring in metal during operation at high temperatures. This general correlation makes it possible to determine by calculation locations in which damage dangerous for operation is most likely to accumulate, thus improving the quality with which the reliability of the components of heat-transfer and mechanical equipment at thermal power stations are predicted.     

The transient electric resistance of contacts taking the surface roughness into account

The transient electric resistance of a contact system has been considered. The dependence of the transient electric resistance of contacts on the roughness of surfaces that are in contact with each other has been determined, which is especially important at low contact pressures. The transient resistance is substantially affected by, in addition to the parameters of roughness, the physical and mechanical characteristics of surfaces that are in contact with each other. A technique for determining the transient electric resistance of contacts taking into account the material, roughness, and shape of surfaces that are in contact with each other, as well as forces of contact pressure, has been suggested. The value of a transient resistance obtained using the suggested technique is in good agreement with the experiment in the range of actual contact pressures in electric contacts.     

计及多能耦合的区域综合能源系统最优能流计算

摘要：为了提高能源利用效率与实现能源清洁供应,区域综合能源系统已成为支撑能源转型的重要技术。研究掌握区域综合能源多能耦合机理,对未来实现系统的有序规划、运行具有重要研究意义。文中提出了一种区域综合能源系统中具有分布式能源的最优能流模型和方法。提出了基于能源集线器模型并充分考虑能耗（太阳能,燃料油,生物质能）的电力系统、天然气系统、热力系统的优化策略。采用基于内点法对区域综合能源系统模型进行求解。通过利用辅助燃烧设备（Supplemental firing equipment,SFE）调节热电联产（Combined heat and power,CHP）单元的热电比,建立了带有SFE的生物质能CHP模型,从而增加了CHP供能比例,最终实现了系统的经济运行。