Fuzzy dynamic programming approach to reactive power/voltagecontrol in a distribution substation

A fuzzy dynamic programming (FDP) approach is proposed for solving the reactive power/voltage control problem in a distribution substation. The main purpose is to improve the voltage profile on the secondary bus and restrain the reactive power flow into a main transformer at the same time. To reach our objectives, the load tap changer (LTC) usually installed in a main transformer is employed to adjust the secondary voltage and the capacitor connected to the secondary bus is employed to compensate the reactive power flow for the load demands. We first forecast the real and reactive power demands of a main transformer and its primary voltages for the next day. With these forecasting data at hand, a fast LTC tap position estimation formula that takes the load models into account is derived to effectively reduce the computational burden for the proposed approach. Practical constraints on bus voltage limits, maximum allowable number switching operations in a day for the LTC and capacitor and the tolerable worst power factor for a main transformer are also considered. To demonstrate the usefulness of the proposed approach, reactive power/voltage control at a distribution substation within the service area of Taipei City District Office of Taiwan Power Company is investigated. It is found that a proper dispatching schedule for the LTC and capacitor can be reached by the proposed approach     

动态规划法在配电网电压无功控制中的应用

提出利用动态规划法解决配电网电压无功控制问题。基于对主变每时段的负荷、馈线每部分的负荷和主变高压侧电压的预测值，利用动态规划法（DP法）确定主变分接头、并联电容器和馈线电容器的优化动作方案，从而使配电网的网络损耗最小，主变低压倒电压与其理想值的偏差最小，主变的功率因数尽可能的高，约束条件包括主变分接头、电容器一天内最大操作次数，馈线电压允许范围，主变功率因数的允许值。为了说明这种方法的有效性，我们将其应用到沧州电力公司某变电站的部分系统中进行无功电压控制。     

Volt/Var control in a distribution system by a fuzzy optimization approach

This paper presents a fuzzy optimization approach for solving the Volt/Var control problem in a distribution system with uncertainties. Wind turbines are being considered in the study distribution system. The main purpose is to find an optimum combination of tap position for the main transformer under load tap changer (ULTC) and on/off status for switched capacitors in a day to minimize the voltage deviation on the secondary bus of the main transformer, reactive power flow through the main transformer and real power loss on feeders. When performing the Volt/Var control problem in conventional methods, the hourly load and wind speed must be forecasted to prevent errors. However, actually there are always errors in these forecasted values. A characteristic feature of the proposed fuzzy optimization approach is that the forecast hourly load and wind speed errors can be taken into account using fuzzy sets. Fuzzy set notations in the load demand, wind speed, voltage deviation on the secondary bus, reactive power flow through the main transformer and total real power loss on feeders are developed to obtain the optimal dispatching schedule under an uncertain environment. To demonstrate the effectiveness of the proposed method, the Volt/Var control problem is performed in a distribution system within the service area of Yunlin District Office of Taiwan Power Company (TPC). The results show that a proper dispatching schedule for ULTC position and capacitor switching operation can be reached using the proposed method.     

配电网时变无功电压优化方法

为降低电能损耗、提高功率因数和保证终端用户的电压质量,针对考虑负荷变化时配电网补偿调压设备的优化控制问题,提出了完整的模型及求解算法。根据系统负荷曲线变化趋势,提出按单调性初步分段进而采用融合的思想使分段数满足补偿调压装置的动作次数约束。应用粒子群优化算法从整体上获得系统一天内的电容器组及有载调压变压器分接头的最优运行方式。算例分析结果表明,这种分段处理方法不仅考虑了负荷的周期变化,而且使控制方案更为简洁、有效。     

智能型变电站电压、无功综合自动控制装置

提出了一种智能型变电站电压和无功综合自动控制装置。它是基于人工神经网络（ANN）的电压、有功和无功负荷预测,模糊边界策略,遗传算法三者相结合的基本原理,用以实现变电站电压和无功综合自动控制装置的全局优化的控制策略,在保证无功基本平衡和电压合格率的前提下,可以使变压器分接头的调节以及并联电容的投切次数减至最低,从而大大提高变压器分接头及开关的寿命,降低现场维护量。     

A Stochastic Programming to Volt/VAR/Total Harmonic Distortion Control in Distribution Networks Including Wind Turbines

Abstract—This article presents a stochastic methodology for volt/VAR/total harmonic distortion control to reduce power losses while satisfying the main recommended power quality standards and optimizing dispatch schedules for the switchable shunt capacitor and on-load tap-changer in distribution networks. The main aim is to find proper dispatch schedules for on-load tap-changer tap positions, substation capacitors, and along feeder capacitors. For this purpose, distribution network uncertainties, including load demand and wind power generation, are considered to provide a robust control scheme. A new scenario reduction method based on the highest potential cluster center is used to decrease the huge number of probable states. A new scenario-based probabilistic time-interval division framework, over a 24-hr period on both load curve and wind power output, is introduced to reduce effects of forecast plan uncertainty and switching operations in the on-load tap-changer. A genetic algorithm solution method is applied to find the best solution corresponding to various scenarios. To improve search ability, a method guaranteeing the suppression of maximum allowable daily substation capacitors switching and effectively correcting the convergence process is utilized. The proposed stochastic approach is tested on an IEEE 123-bus distribution network containing a number of non-linear loads and wind energy generation systems.     

配电网无功优化的分时段控制策略

为改善电压、降低损耗、简化控制，根据负荷水平及其变化趋势，对已装有补偿电容和在变电站装有有载调压变压器的配电网，提出了分时段优化控制的策略，开发了次日运行中电容器投切和调压变压器变比调节的模型和算法。应用改进的退火选择遗传算法，该算法对于每一负荷时段可得出该段的最优运行方式；计算一天所有负荷段即得出次日电容器投切和调压变压器变化调节的运行表。该模型易于满足电容器投切和变压器调节次数的限制。文中还分析了有载调压变压器调节电网电压水平的作用和变压器铁耗的影响。算例结果表明该算法不但能有效地降低电能损耗，而且控制简单。     

A heuristic and algorithmic combined approach for reactive power optimization with time-varying load demand in distribution systems

Reactive power optimization with time-varying load demand in distribution systems is investigated in this paper. The objective of this paper is to determine the proper setting values of capacitor banks and transformer taps for the 24 h in the next day. A heuristic and algorithmic combined approach is proposed in this paper. The approach simplifies the mathematical model of the daily setting values of reactive power/voltage control devices, solves the temporal optimization of each control device by heuristic rules, and then converts the optimization model with time-varying load into the same one as conventional optimization model with constant load. Therefore, the algorithms applied to the conventional optimization model can be easily used to solve the optimization model with time-varying load demand. Results from numerical examples show that a proper dispatch schedule for capacitor banks and transformer taps can be reached by this approach efficiently.     

Coordination control of ULTC transformer and STATCOM based on an artificial neural network

This paper presents an artificial neural network (ANN)-based coordination control scheme for under load tap changing (ULTC) transformer and STATCOM. The objective of the coordination controller is to minimize both the amount of tap changes of the transformer and STATCOM output while maintaining an acceptable voltage magnitude at the substation bus. The coordination controller is designed to substitute for a classical ULTC mechanism by utilizing active and reactive powers, tap position, and STATCOM output. A competitive ANN is used as a classifier for tap positions and trained by a proposed iterative condensed nearest neighbor (ICNN) rule.     

新型变电站电压无功自动控制装置的研制

根据变电站的运行特点，采用最先进的无功调节判据，研制了变电站电压无功自动控制装置，以实现变电站电压无功的优化控制。该装置能在电压合格、无功基本平衡时，使有载调压变压器的分接开关次数和并联补偿电容的投切次数降至最少，从而大大提高变压器有载分接开关的使用寿命并使变电站电压合格经达到100％，线损降低20％左右。     

变压器抽头和无功补偿对系统无功电压的影响

通过对两卷变压器的数学模型进行分析,讨论了两卷变压器抽头调整后,变电站各侧电压及无功功率的变化;无功补偿对变电站各侧电压及无功功率的影响;实际电网生产运行中,无功补偿与变压器抽头的配合调整。并以湖北电网为例给出了算例进行验证,以供电网调度与变电站运行人员参考。     

含风电系统的无功优化调度

针对恒速恒频和变速恒频两类控制模式对风电机组分别进行建模,以系统有功网损最小为目标,以常规发电机和恒电压控制模型风机的无功出力、变压器抽头位置和投入的电容电抗组数为控制变量,建立了含风电系统的无功优化模型。采用原对偶内点算法进行求解,对于模型中的离散变量,提出了优化归整轮流迭代的方法来进行处理。对海南电网汛小方式的算例分析表明,该无功优化模型和方法可以明显地降低系统网损和系统运行成本。     

基于模糊专家推理的500kV变电站自动调压控制方法研究

变电站的电压无功控制是保证电能质量和电力系统安全可靠运行的重要措施。本文分析了当前电压无功控制方法存在的不足，把模糊推理和专家系统相结合，提出一种500kV变电站新型电压无功控制方法。本方法利用模糊推理处理模糊性和不确定性问题的优点，很好地解决了电压越限的模糊边界问题，克服了固定边界控制方法存在的不足。同时，依据专家系统很强的逻辑推理和问题综合的能力，综合调压控制的限制条件、优化原则和设备保护闭锁信息等，实现电容器、电抗器和变压器分接头在变电站各种运行状态下的最佳配合。实验表明，本方法能大大改善变电站系统的调压控制性能、提高电压质量，具有良好的应用价值。     

晋中电网电压和无功现状分析以及改进建议

详细介绍了晋中电网2009年的电压和无功补偿的现状,探讨了有载调压变、电容器等有关问题。最后根据对电压和无功的技术要求,以及无功补偿设备存在的问题,提出了相应的改进建议。     

基于模糊决策树的变电站电压无功控制方法研究

变电研制的电压无功控制是保证电能质量和电力系统安全可靠运行的重要措施。本文分析当前电压无功控制方法存在的不足，把模糊决策树应用到这一领域，提出基于模糊决策树的变电站电压无功控制方法。模糊决策树融合了模糊理论和决策树的优点，不仅能很好地解决电压越限的模糊边界问题，而且能依据调压控制的限制条件优化原则和设备保护闭锁等信息进行综合决策，以实现电容器和变压器分接头在变电站各种运行状态下的最佳配全。用于某110kV变电站的实验表明，本方法能提高电压质量，减少设备调节次数，具有良好的控制性能。     

基于功率和电压组合分段的变电站无功控制

为了防止变压器分接头频繁动作,提出根据有功、无功和系统电压组合分段的方法来进行变电站电压无功的优化控制。该方法采用人工神经网络预测负荷和系统电压,并用计算潮流的方法计算出变压器低压侧归算到高压侧的电压,然后依此电压按变压器分接头动作次数的限制进行初步组合分段。因电压质量比分接头次数的限制更为重要,如果初步组合分段后的电压合格率不满足要求,则将电压合格率最低的段分为两段重新优化,直到满足要求为止。对于电容器,为了减少有功和电压损耗,在不发生倒送无功的情况下应尽量多投入。但在负荷较轻、系统电压太高时则应全部退出。此外,电容器可轮换投切,故对动作次数无需再限制。工作时依据已发生的实际数据,重新预测后续值并修正分段以使控制更切合实际。该法克服了仅按照有功或无功分段的缺陷,提高了控制的准确性。仿真算例证明了该法的有效性。     

DSTATCOM在电网中的应用

根据传统电网所采用的并联电容器组无功补偿方式及自动投切方式的诸多弊端,提出一种对已有并联电容器补偿装置的变电站进行智能化改造的最优方案.通过电网220kV某变电站电网负荷对系统电压影响的研究,确定DSTATCOM（配电网静止同步补偿装置）无功补偿容量,并设计综合控制策略控制并联电容器组的自动投切,实现无功补偿容量的柔性...     

基于调度自动化主站的电压无功自动控制系统

在分析了电压无功二十域图的基础上,介绍了iES500电压无功自动控制系统,该系统是基于调度自动化主站基础上实现有栽变压器分头的自动调整和电容器的自动投切,拓展了SCADA系统的功能,相比常规的变电站的电压无功自动控制装置(VQC),投资小、效率高、便于监视、利于维护,并且可以实现全网电压的分等级自动控制。     

利用有载调压变压器与电容器进行无功电压控制的离散优化模型

本文在大型变电站的二次母线装设可投切的补偿电容器组和带负荷可调分接头的主变压器相配合进行联合控制的连续模型的基础上,提出了无功电压双参数离散模型,该模型考虑了电容器组和分接头的非连续调节,利用该模型对一实际变电站无功电压控制进行了计算,并与连续模型的计算结果进行了比较。     

Optimal reactive power dispatch based on harmony search algorithm

This paper presents a harmony search algorithm for optimal reactive power dispatch (ORPD) problem. Optimal reactive power dispatch is a mixed integer, nonlinear optimization problem which includes both continuous and discrete control variables. The proposed algorithm is used to find the settings of control variables such as generator voltages, tap positions of tap changing transformers and the amount of reactive compensation devices to optimize a certain object. The objects are power transmission loss, voltage stability and voltage profile which are optimized separately. In the presented method, the inequality constraints are handled by penalty coefficients. The study is implemented on IEEE 30 and 57-bus systems and the results are compared with other evolutionary programs such as simple genetic algorithm (SGA) and particle swarm optimization (PSO) which have been used in the last decade and also other algorithms that have been developed in the recent years.