【作者】 熊虎岗；

【导师】 程浩忠；

【作者基本信息】 上海交通大学 ， 电力系统及其自动化， 2008， 博士

【摘要】 如何保证电力系统安全、经济和可靠地运行,一直是电力工作者们致力研究的课题。然而在电力市场环境下,由于竞争机制的存在和对环境保护的考虑,现有的发、输电设施被最大程度地利用着,以满足日益增长的负荷需求,使得系统运行点比以往更接近稳定极限边界,当系统发生较严重的故障时,极易诱发以电压崩溃为特征的电网瓦解事故。无功潮流优化是协调电力系统安全和经济运行的重要手段之一,但在通过调整相关无功设备来实现降低网络有功损耗和提高系统电压水平的过程中,不可避免地会改变系统的电压稳定裕度,如果在无功潮流优化中考虑系统的电压稳定性,必然会减少电压崩溃事故的发生。为此本文对计及静态电压稳定性的多目标无功潮流优化进行了相关的研究,建立了对应的数学模型,并运用免疫优化算法求解,主要内容包括:(1)在综合考虑系统运行的网络有功损耗、电压水平和静态电压稳定的前提下,建立了集安全性和经济性于一体的多目标无功潮流优化模型,分析了电压稳定的特征值指标在无功潮流优化中应用的有效性;由于无功潮流优化具有多目标、多控制变量、多约束条件和连续、整型变量混杂等特点,对自适应免疫算法在电力系统无功潮流优化中的应用进行了研究,定义和运用了局部亲和力与整体亲和力来评价多目标函数的解,避免了对多目标函数量纲处理和权重系数选取的缺点;算例验证了所提模型的正确性和算法的可行性。(2)关键节点的发电机无功备用容量多寡是衡量系统电压稳定裕度的一个重要指标,为此建立了以提高系统无功备用容量和电压水平以及减少网络有功损耗为多目标的无功潮流优化模型。为求取系统的无功备用容量,需要考虑发电机所处的系统位置和对电压稳定的支撑力度,定义了系统的无功备用分布系数,并分两步求取:首先,在定义空间电气距离概念基础上,提出了基于免疫-中心点聚类的无功/电压控制分区算法,按照此算法对系统进行分区,计算每个区域内发电机到所在区域其它节点距离之和,以此距离和作为发电机对该区域的电压稳定支撑系数;然后,依据每个区域的电压稳定裕度计算各个区域的无功备用需求系数,从而在发电机支撑电压稳定系数和区域无功备用需求系数的基础上确定系统无功备用的分布系数,依此系数计算系统的无功备用容量。算例验证了分区算法的正确性和在无功潮流优化中提高系统无功备用容量的可行性。(3)系统的可用输电容量(Available Transfer Capability,ATC)既是衡量电网安全稳定运行的重要指标,也是引导资源优化配置的关键市场信号之一,因此对提高系统ATC和电压水平以及减少网络有功损耗为多目标的无功潮流优化进行了研究。在线路P-Q电压稳定域的基础上,定义了线路潮流分布因子,并依此分布因子,提出了一种系统在正常情况下,考虑静态电压稳定和线路热稳定的ATC计算方法,该方法只需知道电力交易情况,且只要进行一次潮流计算便可求出系统的ATC,计算量非常小,避免当前考虑电压稳定约束ATC计算量大的缺点;分析了在无功潮流优化中对系统ATC的影响。算例验证了所推导计算ATC方法的正确性以及将提高ATC作为无功潮流优化目标函数的可行性。(4)在电力市场环境下,实行厂网分离,为激励发电公司积极参与提供无功辅助服务,需向其支付一定的费用。电网公司优化系统运行时,在保证系统稳定的前提下,应该从技术上考虑减少支付这样的费用,于是对电力市场环境下考虑静态电压稳定约束的日无功潮流优化进行研究。相对于静态无功潮流优化,日无功潮流优化要考虑一天内无功调节设备动作次数约束和系统负荷的变化。为既能顾及到设备动作次数约束,又能充分考虑各节点负荷变化,定义了系统的负荷综合变化来描述系统负荷曲线,并对其分段,然后运用聚类的方法选择优化断面,从而利用负荷分时段控制来解决设备动作次数约束,把日无功潮流优化问题转化为几个大时段断面的无功潮流优化;另外考虑到当前计算发电机机会成本方法存在的某些不足,提出了一种简单实用的发电机机会成本计算方法。建立了以系统故障情况下的静态电压稳定为约束条件,降低系统网络有功损耗和减少无功辅助服务费用为目标函数的日无功潮流优化数学模型,通过求解,进而形成优化的无功设备投切方案。算例验证了所提模型的正确性,得出了在市场环境下,无功潮流优化中考虑减少无功辅助服务费用的必要性。更多还原

【Abstract】 In the electricity market, for the environment and economy limit, the system current transfer capability is used furthest and possible close to its limit in the load peak time, the system voltage stability margin is very lower than ever and easy to collapse when the system meets the serious contingencies. Optimal Reactive Power Flow (ORPF) is an effective measure to hold the security and economy balance of the power system operating. To reduce the active power loss and improve the voltage quality are the general ORPF main objectives, and the system voltage stability is considered rarely. But the system voltage stability margin may be changed in the ORPF process. If the system voltage stability is considered in ORPF, the voltage margin can be improved and the collapse probability will be small. So the multi-objective ORPF incorporating static voltage stability is studied in this dissertation, the main research work is summarized as follows:(1) The ORPF security and economy hybrid model is put out based on considering the active power loss, voltage quality and voltage stability margin, the validity of minimal eigenvalue of the voltage margin index used in ORPF is analysed. For ORPF is a typical non-linear programming problem with the characteristics of multi-objective, uncertainty, multi-restriction and discreteness, a multi-objective self-adaptive immune algorithm (MOAIA) is proposed to resolve the model in this dissertation, the main idea of the proposed algorithm includes two parts, firstly, the partial affinity and global affinity are defined to evaluate the antibodies affinity to the multi-objective functions, this part can avoid the weight factor selection; secondly, self-adaptive crossover, mutation and clone rates of the antibodies are used to keep the antibodies diversity, hence the proposed algorithm can achieve the dynamic balance between individual diversity and population convergence. The test systems results show the model is right and the algorithm is feasible.(2) The system reactive power reserve capacity is an important index for the voltage stability margin, so a new ORPF model is put out, whose objectives are to improve the system reactive reserve capacity and voltage level and decrease the active power losse. The system reactive power reserve capacity is not the sum of the generators reactive power reserve capacity. In order to calculate the system reactive power reserve capacity, the generators locations in power system and their value to support voltage stability must be considered. The system reactive power reserve distributor factor is defined and can be calculated based on two steps, firstly, the spatial electrical distance is defined and the immune-medoid clustering algorithm is proposed for reactive power/voltage control network partitioning, the total distance of the generator to the other buses is looked as the index to support the region voltage stability; secondly, the region reactive power reserve demand index is calculated based on the region stability margin. IA is used to resolve the model optimal solution and tested in the 84-bus system, the results indicate the system reactive power reserve capacity model is right, and the network partitioning algorithm is feasible.(3) Available Transfer Capability (ATC) is not only an important factor to evaluate the system stability, but also a key signal to distribute the power system resource, so ORPF with improving the system ATC is studied. A novel calculation method of ATC considering voltage stability is proposed, in the line P-Q voltage stability plane, the limit point of line stable operating can be gotten according to the line power flow distributor factor, while the position of the line thermal limit and the voltage stability of P-Q curve is considered. The system ATC can be calculated by one time power flow, so this method calculating burden is very small. At the time, the ORPF affection to the system ATC is analysed. The test systems results show the ATC calculating method is right and improving the system ATC is feasible in ORPF.(4) In the electricity market, the generator companies and the grid companies have the different economic benefit, in order to encourage the generator companies to support the reactive power auxiliary service, the grid companies will pay for the service, the grid companies should decrease the payment by the technology way, so the daily ORPF is studied. Relative to the static ORPF, the daily ORPF should consider the reactive power equipments action times and the load change. The system load integrative change is defined to reveal the buses load change and its curve is divided to satisfy the equipments action times constrain, the clustering method is used to select the system section for ORPF, in this way, the daily ORPF is looked as several system section static ORPF. A new simply way to calculate the generator opportunity cost is proposed and can avoid the general method shortcoming. The mathematic model of daily ORPF is put out whose objective function is to decrease the system active power loss and reactive power ancillary service, while the voltage stability is looked as constrain conditions when the system meets the line contingences. In two test systems, the load curve dividing method and the model of daily ORPF are tested, the results show the load curve dividing method is feasible and the model is right.更多还原