基于UPFC的灵活交流输电潮流控制计算

利用等效功率注入方法,提出一种含UPFC的灵活交流输电潮流计算方法。该方法将UPFC对潮流的控制作用转移到所有在线路的两个节点上,联立潮流控制目标,修正雅可比矩阵,再运用传统的潮流计算方法－牛顿－拉夫逊法进行求解。Ward*Hale6节点等多个仿真逄例显示了UPFC在稳态情况下,能够独立、快速控制线路中的有功、无功潮流,验证了该算法具有较好的可靠性和有效性。     

统一潮流控制器的非线性控制和对电力系统稳定性的改善

首先考虑UPFC装置与电力系统串联和并联的两部分之间耦合直流电容的动态,建立了具有UPFC的输电系统的动态数学模型。在此基础上,对UPFC的4个控制变量进行分析,提出了控制变量m1,m2和ψ1的线性控制规律,并运用基于微分几何理论的仿晨线性系统反馈精确线性化和动态反馈原理及方法,得到了控制变量ψ2的非线性最优控制律的解析表达式,从而提出了UPFC的线性与非线性最优混合控制策略。控制策略的测量量均可本地化,以利于工程应用。仿真结果表明在文中所给出的非线性控制器作用下,UPFC能有效地改善电力系统的动态品质和暂态稳定性。     

Adaptive distance relay setting for parallel transmission network connecting wind farms and UPFC

The paper presents an adaptive distance relay setting for parallel transmission network connecting wind farms. The ideal trip characteristics of distance relay is greatly affected in presence of mutual coupling of parallel transmission lines as the apparent impedance is significantly affected. Similarly, the reach setting of the relay for the lines connecting wind farms is significantly affected as the relay end voltage fluctuates continuously. Thus, the proposed study focuses on developing adaptive relay setting for parallel transmission network including wide variations in operating conditions of wind farms and effect of mutual coupling, together. Further, the performance of the proposed adaptive relay setting for parallel lines including Unified Power Flow Controller (UPFC) indicates the potential ability of the proposed analytical approach in handling distance relaying in transmission system.     

A generalized approach for determination of optimal location and performance analysis of FACTs devices

This paper presents a generalized approach for determination of optimal locations for placement of Flexible AC Transmission Systems (FACTs) devices in the power system with an objective of reducing real power loss and to reduce overloading of the lines. An objective function involving above objectives is formulated and a detailed mathematical model for each objective is presented in terms of system parameters. Three FACT devices, namely, Unified Power Flow Controller (UPFC), Interline Power Flow Controller (IPFC), and Optimal Unified Power Flow Controller (OUPFC) which are capable of controlling both active and reactive power are considered in simulation and analysis of the networks. The parameters to be optimized have been identified and incorporated in the objective function for each device. Sensitivity analysis is used to locate optimal buses to place the FACTs devices in the network. Effectiveness of the approach is demonstrated on a 5 Bus and an IEEE 14 Bus systems for each FACT device. Simulation results obtained for each device using proposed approach are compared with those obtained in the literature.     

低压多源并供点状网络潮流分布及其控制技术

针对低压多源并供点状网络中,某些电源可能出现逆功率运行而不能满足并供条件的问题,提出了一种低压母线潮流控制方法。分析了低压多源并供点状网络潮流分布规律,得出了并供电源出力与电源电压、系统等值阻抗以及低压侧负荷之间的定量关系,理论上分析出电源出现逆功率输出的条件;为满足多源实时并供运行条件,推导出基于均衡电源出力的低压母线侧稳态潮流控制模型,得到了电源出力调节量与串联补偿电压之间的关系。最后搭建了试验系统,并基于统一潮流控制器进行了稳态潮流控制试验,结果证明了该方法的有效性。     

Optimal location and signal selection of UPFC device for damping oscillation

Unified power flow controller (UPFC) is used for controlling the real and reactive power in transmission line and bus voltage simultaneously and independently. An additional task of UPFC is to increase transmission capacity as result of power oscillation damping. The effectiveness of this controller depends on its optimal location and proper signal selection in the power system network. A residue factor has been proposed to find the optimal location of the UPFC controllers and eigenvalue analyses are used to assess the most appropriate input signals (stabilizing signal) for supplementary damping control of UPFC to damp out the inter-area mode of oscillations. The proposed residue factor is based on the relative participation of the parameters of UPFC controller to the critical mode. A simple approach of computing the residue factor has been proposed, which combines the linearized differential algebraic equation model of the power system and the UPFC output equations. While for signal selection a right-half plane zeros (RHP zeros) and Hankel singular value (HSV) is used as tools to select the most receptive signal to a mode of the inter-area oscillation. The placements of UPFC controllers have been obtained for the base case and for the dynamic critical contingences. The effectiveness of the proposed method of placement and selection of signals are demonstrated on practical network of TNB 25 bus system of south Malaysian network and New England 39 bus system.     

Optimal location and parameter setting of UPFC for enhancing power system security based on Differential Evolution algorithm

This paper presents a new approach based on Differential Evolution (DE) technique to find out the optimal placement and parameter setting of Unified Power Flow Controller (UPFC) for enhancing power system security under single line contingencies. Firstly, we perform a contingency analysis and ranking process to determine the most severe line outage contingencies considering line overloads and bus voltage limit violations as a Performance Index. Secondly, we apply DE technique to find out the optimal location and parameter setting of UPFC under the determined contingency scenarios. To verify our proposed approach, we perform simulations on an IEEE 14-bus and an IEEE 30-bus power systems. The results we have obtained indicate that installing UPFC in the location optimized by DE can significantly enhance the security of power system by eliminating or minimizing the overloaded lines and the bus voltage limit violations.     

基于节点电流注入法的UPFC潮流控制新方法研究

提出了一种基于节点电流注入法的改进的统一潮流控制器潮流控制的新方法:串联侧基于电流预测法实现对线路有功、无功功率的控制,并联侧用无功注入电流控制母线电压。利用电力系统综合程序(PSASP)的用户程序接口(UPI)功能,用C++语言编写了UPFC潮流控制模型的用户程序,与潮流程序交替求解,实现UPFC的控制功能。通过算例验证了该方法的正确性及有效性。所建模型无需改变UPFC两侧接入点的节点类型,控制灵活;基于节点电流注入法的思想对柔性交流输电系统控制器与其他商业软件的接口有借鉴意义。     

统一潮流控制器( UPFC)在电压稳定性中的应用

采用雅可比矩阵的灵敏度指标探讨统一潮流控制器( UPFC)对电力系统电压稳定的影响,分析装设统一潮流控制器(UPFC)前后整个系统(包括UPFC安装点)的电压稳定性能,并通过系统仿真,表明UPFC能有效地提高系统的电压稳定性.     

An improved power flow for an ill‐conditioned power system with FACTS devices

This paper addresses the issue of the computation techniques for assessing the steady‐state power flows controlled by Flexible AC Transmission Systems (FACTS), which contain variable series compensators (VSC), phase shifters (PS), interphase power controllers (IPC), and unified power flow controllers (UPFC). An improved Newton–Raphson load flow program has been developed based on an analysis of the convergence characteristic of the conventional method. It is shown that the conventional method tends to suffer from ill‐conditioning problem, resulting in shrinkage of the convergence region. Based on examinations of the condition number of the Jacobian, a penalty function method is adopted in order to avoid the ill‐conditioning problem and to guarantee a successful convergence. Although the computational burden is increased about 2 to 3 times, the proposed method considerably extends the region of convergence. The effectiveness of the proposed method is demonstrated through numerical examinations using IEEE 57 and 118 bus systems. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(1): 30–37, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10027