基于最优控制原理的暂态稳定预防控制模型

基于时域仿真得到系统受扰轨迹,给出了暂态稳定预防控制的非线性规划模型。该模型把功角在末端时刻不大于预先设定的门槛值作为暂态稳定约束条件。通过引入最优控制原理,把微分-代数方程所描述的电力系统预防控制转化为以各发电机有功输出为控制量的最优控制问题:重新调整控制量控制各发电机的转子相对角度,使其在末端时刻都不大于设定的门槛值,从而实现了非线性系统的状态转移。所提出的暂态稳定预防控制模型与时域仿真具有同等的模型适应性。经IEEE 39节点测试系统的数值分析结果表明该算法的有效性,估计的精度能够满足实际工程的需要。     

A generation rescheduling method to increase the dynamic securityof power systems

In this paper, a new method is proposed for dynamic security dispatch. The idea of coherent behavior of generators is used to find a new generation configuration with better transient stability behavior. Rescheduling the generation in the power system improves system security by increasing the critical clearing time or the transient energy margin without changing total generation. The calculation in the proposed method is simple and direct; the generation rescheduling depends only on the original generation and inertia constants of the machines, and their rotor speeds at the fault clearing time. In this work, the transient energy function (TEF) method is used to check the dynamic security of the system by analyzing all credible three phase faults with single line outages. If the worst energy margin is not acceptable, the proposed rescheduling is done, and the security is checked again. The method has been tested on the Ontario Hydro 55-bus 11-generator system, the IEEE 145-bus 50-generator system and the IEEE 162-bus 17-generator system. Results on several loading levels of the 162-bus 17-generator system are also shown     

基于PEBS法的暂态能量裕度灵敏度快速计算

提出了一种基于PEBS法暂态稳定分析的能量裕度灵敏度计算方法。该方法以系统故障前稳定平衡点作为暂态势能参考点,沿持续故障轨迹采用数值方法计算暂态势能。在系统持续故障仿真和灵敏度动态方程计算过程中,引入高阶Taylor级数展开技术,可以在保持计算精度的前提下提高计算步长,显著提高计算速度。将到达临界势能点的判据展开以时间为自变量的多项式形式,通过解方程求得到达临界势能点的时间,从而快速确定临界势能点的位置。提出的能量裕度灵敏度分析方法包括两方面:计算故障前机组机械注入功率变化对能量裕度的灵敏度,用于指导预防控制;计算故障切除后的控制措施对稳定裕度的影响,用于指导紧急控制。New England 10机系统算例验证了该方法的有效性。     

A METHODOLOGY OF SECURE AND OPTIMAL OPERATION OF A POWER SYSTEM FOR DYNAMIC CONTINGENCIES

ABSTRACT

Just as in static security constrained optimization of power systems, there is need to do preventive scheduling if the system state is found to be insecure through dynamic contingency analysis. Current work in this area based on energy functions and sensitivity considerations only computes another feasible and normal operating point either through the controlling u.e.p or the potential energy boundary surface method. In this paper we use the hybrid method which involves integration of the system equations only once till the controlling u.e.p is reached to compute the energy margin. Based on the sensitivity of the energy margin to generation powers, rescheduling is done through an OPF algorithm resulting in a secure but optimal solution. Results on a 3 machine, 9 bus system are very encouraging. This methodology could form a basis for integrating current OPF packages into the DSA package.     

Damping inter-area oscillation by generation rescheduling based on wide-area measurement information

Inter-area oscillations are inherent to power systems which can be caused due to oscillation of two coherent groups of generators against each other with low or negative damping. Poorly damped oscillations can pose various problems such as limiting transfer capabilities and in more severe cases can lead to uncontrolled islanding causing system blackout. In this paper, for damping inter-area oscillation a new method based on the wide area measurement system (WAMS) and using generation rescheduling (GR) is proposed. The proposed algorithm consists of three tasks; identification of inter-area mode, determination the most effective generators for rescheduling and enhancing damping of inter-area mode by GR. In this approach, first by means of Independent Component Analysis (ICA) and modified Random Decrement (RD) techniques and using on-line power and rotor angle oscillation data provided by WAMS, the frequency and damping of the inter-area mode is identified. In the case of low damping of oscillation, by using mode shape of the inter area mode, generation rescheduling is applied for improvement of damping. In this paper, a non-model based method is adopted for estimating mode shape from the measured data like generator rotor speeds. The proposed approach is applied on a two area small system and IEEE 39-bus test system and the results demonstrate effectiveness of the method for enhancing oscillation damping.     

Derivation and application of sensitivities to assess transient voltage sags caused by rotor swings

The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator–load pairs and locations for applying preventive control measures.     

Stability-constrained generation rescheduling using energy margin sensitivities

In this paper, a structure preserving energy margin (EM) sensitivity-based analysis is presented to determine the amount of preventive generation rescheduling to stabilize a transiently unstable power system. An expression using a simplified model is derived to relate the change in the EM to change in generation. Utilising this expression, two approaches for generation rescheduling are developed which are applicable to detailed model of power systems. The proposed methods are applied to the 10-machine New England power system and 16-machine power system with detailed power system models.     

在线生成策略表与实时预测切机

按照策略表切机是电力系统中提高暂态稳定的有效方法之一。利用能量裕度灵敏度法在中央处理单元在线修改策略表、在故障监测单元实施实时匹配和就地预测发电机暂态稳定以决定是否切机。在厂站采用“当前”统计模型、常加速模型及常速模型构成的交互式多模型(IMM)自适应滤波算法。跟踪预测发电机转子角度。当预测到机组失稳时，按照策略表及实时匹配情况，方始发出切机命令。这种紧急切机控制的并行双重算法能有效地防止误切机组。通过经典模型下新英格兰10机39节点系统的应用说明算法的有效性。     

基于XGBOOST-PSO提高受端电网电压暂态稳定的发电机无功优化方法

考虑发电机稳态输出无功对其支撑暂态电压恢复稳定能力的影响,基于机器学习研究优化发电机稳态输出无功提高电压对故障扰动保持暂态稳定能力的预防控制方法。该方法采用加权多二元表暂态稳定裕度指标量化母线暂态电压对不同预想故障扰动的综合稳定裕度,并基于指标排序确定稳定裕度薄弱母线。同时基于发电机无功调节对预想故障下各薄弱母线电压暂态稳定裕度综合作用灵敏度排序,选择作用灵敏发电机。在利用XGBoost建立根据系统稳态特征向量预测薄弱母线暂态电压稳定的分类模型基础上,以系统对预想故障扰动保持暂态电压稳定为约束、以减小发电机稳态无功调节对网损产生影响为目标,基于潮流计算寻优灵敏发电机稳态输出无功,以提高薄弱母线的暂态电压稳定性。最后采用雅湖直流接入江西电网的PSASP计算模型验证了所提方法的有效性。     

基于轨迹灵敏度的能量裕度灵敏度解析算法

电力系统参数的变化对系统稳定性有很大的影响,如何确定这些参数的变化在给定故障情况下对系统稳定性的影响、改变哪些参数对系统稳定性影响更大具有重要意义。提出了一种系统能量裕度灵敏度的解析算法,从能量裕度的数学表达式出发,利用能量裕度的全微分公式进行灵敏度计算。该方法计算比较灵活,考虑了发电机动态过程对轨迹灵敏度的影响,计算能量裕度对系统参数的灵敏度。该算法在IEEE50机系统中进行了测试。     

基于广域测量系统的快速暂态稳定预测方法

在运用相量测量单元实测系统故障时轨线的基础上,采用一种在机器人领域广泛应用的抓球算法,对电力系统故障后预判失稳的发电机转子角进行预测.该方法分为跟踪和预测2个阶段:首先应用粒子群优化算法对跟踪阶段进行多参数优化,加快了跟踪的过程;然后利用泰勒级数展开法预测发电机的转子角.该方法无需知道系统结构的先验知识,可以提前0.5 s判断各发电机的同步性,得到足够的"可用反应时间"用于在线失稳预警或就地控制.在10机39节点的新英格兰测试系统和50机145节点测试系统上的仿真结果表明了该方法的有效性.     

基于广域量测信息的负荷裕度灵敏度计算新方法

提出一种基于广域量测信息的电力系统负荷裕度灵敏度(LMS)分析方法。根据电力系统的广域量测信息,在线计算电力系统中各负荷节点的负荷裕度;依据所得的负荷裕度,提出一种基于广域量测信息的节点负荷裕度对有功、无功及机端电压的灵敏度分析方法;针对所提的LMS方法,进一步提出了改善系统电压稳定性的相关控制策略;最后将所提方法应用到New England 39节点系统和IEEE 118节点系统中,仿真结果验证了所提方法的正确性和有效性。     

Overload Alleviation With Preventive-Corrective Static Security Using Fuzzy Logic

This paper presents a concept overview of an automatic operator of electrical networks (AOEN) for real-time alleviation of component overloads and increase of system static loadability, based on state-estimator data only. The control used for this purpose is real-power generation rescheduling, although any other control input could fit the new framework. The key performance metrics are the vulnerability index of a generation unit (VIGS) and its sensitivity (SVIGS), accurately computed using a realistic ac power flow incorporating the AGC model (AGC-PF). Transmission overloads, vulnerability indices and their sensitivities with respect to generation control are translated into fuzzy-set notations to formulate, transparently, the relationships between incremental line flows and the active power output of each controllable generator. A fuzzy-rule-based system is formed to select the best controllers, their movement and step-size, so as to minimize the overall vulnerability of the generating system while eliminating overflows. The controller performance is illustrated on the IEEE 39-bus (New England) network and the three-area IEEE-RTS96 network subjected to severe line outage contingencies. A key result is that minimizing the proposed vulnerability metric in real-time results in increased substantial loadability (prevention) in addition to overload elimination (correction).      

基于发电机功率分配因子的静态电压稳定预防控制

针对静态电压稳定预防控制实用性的问题,提出一种在线静态电压稳定预防控制算法。该算法引入未来时刻发电机功率分配因子作为电压稳定裕度的控制变量,利用电压稳定裕度对各类控制参数的灵敏度信息,通过集中调度和预选参与调度集等策略,形成预防控制所需要的线性规划模型,给出预防电压失稳的调度方案。算法的优点是可将严重故障和失稳故障放在统一的模型中求解;引入未来时刻发电机功率分配因子作为电压稳定裕度的控制变量,可有效地减少其他控制参数的调整量。对湖南实际电网750节点系统的试验,证明了所提方法的有效性和实用性。     

在线静态电压稳定预警与预防控制系统

介绍了在线静态电压稳定预警与预防控制系统的功能框架、算法特点和应用效果。应用最小奇异值和改进连续潮流算法在线计算电网的稳定指标,实时监视分区及全网的负荷裕度和重要联络断面的功率传输极限,并给出预警级别提示;应用分布式计算架构实现了一个高性能的故障筛选子系统,对于较严重故障能够给出预防控制策略。该系统可与自动电压控制系统集成,保证了控制后电网的电压稳定。在华北网调和江西省网的应用效果证明了系统的有效性。     

暂态稳定安全经济代价计算

根据暂态稳定裕度对节点有功、无功功率及变压器运行方式变化的灵敏度分析结果,以有功、无功电费最小为目标函数,构造了适用于合同交易与非合同交易共存的电力市场安全预防再调度和安全校正再调度数学模型,此模型可用线性规划求解。此方法能用于计算为提高电力系统暂态安全性而须付出的经济代价,经济代价可用于最佳可靠性指标研究。根据稳定裕度对节点功率的灵敏度来考虑系统安全约束比采用联络线潮流约束更为可靠;考虑有功、无功管理再调度比只考虑有功调度可能更为经济。中给出了24节点系统实例分析结果。     

断面安全约束下发电可行域实用分析方法

针对市场环境下调度计划月度安全校核存在时间跨度大、负荷以及新能源出力预测精度差、交易电量的不确定程度高等问题，提出构建发电可行域的工程实用方法。首先，基于各发电机出力相对于关键断面的有功灵敏度，结合机组的地理位置，对全网机组进行分群；然后，提出构建发电可行域的基态潮流确定方法；在此基础上，以主导发电机群的总出力为横坐标，以系统总负荷为纵坐标，构建系统在不同负荷水平下的主导发电机群发电可行域；最后，根据系统运行方式对发电可行域进行在线修正。以某省级电网为例，验证所提方法的可行性。     

考虑动态电压安全的发电机有功出力最优调整

在灵敏度方法的基础上,以系统当前运行点与最近的电压崩溃点的负荷几何距离作为电压稳定指标,提出了有效提高系统稳定裕度的发电机有功出力调整方案。在开放输电环境下,系统发生N-1故障后,首先进行电压稳定裕度分析,对于不满足系统安全运行要求的状态,计算发电机有功出力对稳定裕度的灵敏度,并以此为基准调整发电机有功出力,从而增大系统稳定裕度。IEEE 57节点系统仿真算例验证了所提出方法的有效性。     

断面安全约束下发电可行域实用分析方法

针对市场环境下调度计划月度安全校核存在时间跨度大、负荷以及新能源出力预测精度差、交易电量的不确定程度高等问题,提出构建发电可行域的工程实用方法。首先,基于各发电机出力相对于关键断面的有功灵敏度,结合机组的地理位置,对全网机组进行分群;然后,提出构建发电可行域的基态潮流确定方法;在此基础上,以主导发电机群的总出力为横坐标,以系统总负荷为纵坐标,构建系统在不同负荷水平下的主导发电机群发电可行域;最后,根据系统运行方式对发电可行域进行在线修正。以某省级电网为例,验证所提方法的可行性。     

Rescheduling of power systems constrained with transient stability limits in restructured power systems

This paper investigates various approaches to relieve the transient stability constraint in restructured power systems. The approaches adopted fall into two broad categories: those based on eliminating the constraint in the least-cost way and those based on eliminating with the least possible rescheduling. The latter group can, on the other hand, emerge in the form of a pool-protected policy in which the bilateral contracts are rescheduled to maintain the stability or in the form of a contract-protected policy in which the realizable bilateral contracts are maximized while minimizing the rescheduling in pool market. Transient energy function (TEF) method is used as a tool to calculate the sensitivity of energy margin to the variations in the magnitude of generation and load. The effectiveness of the method is illustrated by case studies on Western System Coordinating Council (WSCC) 3-machine 9-bus power system and on the 10-machine 39-bus New England test system and the results are compared. The results are also verified by time domain simulations.