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     

Modeling and real‐time simulation of UPFC

We have developed a digital real‐time simulator of Power Electronics Controllers, so‐called FACTS (Flexible AC Transmission Systems) Controllers and/or Custom Power by using MATLAB^TM/SIMULINK^TM and dSPACE^TM System. This paper describes the modeling and the calculation accuracy of a UPFC (Unified Power Flow Controller) model. Hence, the developed simulator operates at a large time step, in order to improve simulation accuracy, a correction processing of the switching delay is implemented into the UPFC model. Calculation accuracy of the real‐time UPFC model is at the same level as EMTDC^TM results. We confirm stable operation of the developed UPFC model by connecting a commercial real‐time digital simulator (RTDS^TM). © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 19–26, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20200     

基于母线关联出线暂态频谱信息的UPFC线路纵联保护

统一潮流控制器(UPFC)作为新一代柔性交流输电系统元件在输电线路中逐渐应用,需要对含UPFC线路的保护原理进行深入研究。通过分析UPFC对线路故障暂态影响,得出高频分量经其串联侧时发生严重衰减,使仅利用单端暂态量的保护可靠性下降。分析母线关联出线的故障暂态特征可知,同一母线的故障侧线路与非故障侧线路的电流频谱分布存在明显差异。通过采用小波能量熵提取母线各出线暂态信息,提出一种适用于含UPFC线路的方向纵联保护方案。仿真结果表明,该方案可准确识别区内、外故障及母线故障,在不同过渡电阻、故障初始角等故障情况下,均具有较好的灵敏性和可靠性。     

统一潮流控制器近端母线的短路电流计算方法

针对目前实际投运的统一潮流控制器(UPFC)及其采用的故障控制策略,基于电网络理论推导了UPFC近端母线短路电流的计算方法。使用UPFC串联线路对故障母线的转移导纳描述了UPFC的近端母线,由于UPFC串联侧在近端母线故障时立即被旁路保护,导致故障母线的戴维南等值电势发生突变,进而对短路电流的计算结果产生影响,计算结果的相对变化与UPFC故障前运行电压和电流分布系数有关。在IEEE 9节点系统中,研究了运行条件变化以及UPFC参数变化对短路电流的影响,并使用PSCAD对计算结果进行了仿真验证;在IEEE 118节点系统中,分析了UPFC对大规模电网短路电流的影响。结果表明,UPFC对其两侧母线短路电流的影响相反,且对近端母线短路电流的影响随着电气距离增大而减小。     

泛在电力物联网框架下的新型UPFC系统

基于提出的建设泛在电力物联网的号召,利用统一潮流控制器（unified power flow controller, UPFC）实现物理层面上多条线路的紧密联系。由多个换流器串联接入到多条输电线路上,另外多个并联换流器连接到其他多个网络中,形成一个由换流器作为媒介的大型电力系统输电框架。在连接众多换流器的直流线路上,由储能电池作为有功功率支撑并联接入,共同组成泛在电力物联网框架下的新型UPFC系统。对新型UPFC系统进行数学建模,以对可再生能源的最大消纳能力和有功功率传输的最小成本为目标函数,用遗传算法进行求解。通过算例仿真验证了新型UPFC系统在增强有功功率传输极限、减少有功功率传输成本等方面的优越性。