Dynamic ATC enhancement through optimal placement of FACTS controllers

Flexible AC Transmission System (FACTS) controllers offer an effective means to enhance the power transfer capability of the network. However, the extent to which a FACTS controller can enhance Available Transfer Capability (ATC) depends on its optimal location in the system. This paper has proposed sensitivity analysis of structure preserving energy margin with respect to the control parameters of FACTS controllers for their optimal placement in the network. Two types of FACTS controllers, viz. Static Synchronous Compensator (STATCOM) and Unified Power Flow Controllers (UPFC) have been considered. The hybrid approach, combining a structure preserving and a time domain simulation method, has been utilized to compute the dynamic ATC in presence of these controllers and their impact on dynamic ATC has been analyzed. The potential energy, contributed by the STATCOM and the UPFC, has also been included in the structure preserving energy function to include their influence on transient stability. The proposed method has been tested on 39-bus New England system and a practical 246-bus Indian system.     

统一潮流控制器在南京西环网的应用

首先介绍了统一潮流控制器（unified power flow controller,UPFC）在国内外理论研究和工程应用的发展和现状。接着具体阐述了南京西环网在发展中存在的输电通道能力不足、潮流分布不均等问题。通过与常规解决措施的对比,阐明了在南京西环网中应用UPFC提高电网输电能力及稳定性的可行性、必要性和必然性。经分析计算发现,通过应用UPFC,不仅能够有效控制电网潮流,提高现有电网的输电能力,从而避免投资巨大、实施难度极大的城市电缆输电通道建设,而且还能够很好地适应未来电网网架的变化。因此,在南京西环网甚至将来的江苏电网中,应用UPFC可以显著提高电网的输电能力、利用效率及运行安全性,能够取得良好的经济效益和社会效益。     

潮流和最优潮流分析中FACTS控制器的建模

综述了最近FACTS控制器的数学模型在电力系统潮流和最优潮流分析中的新进展.不仅讨论了单换流器FACTS控制器,如静止同步并联补偿器(STATCOM)和静止同步串联补偿器(SSSC);而且也讨论了多换流器FACTS控制器,如统一潮流控制器(UPFC)、相间功率控制器(IPFC)、通用统一潮流控制器(GUPFC)和电压源型直流输电(VSC HVDC).此外还讨论了基于电压源换流器技术的HVDC的数学模型.不仅涵盖FACTS控制器的单相数学模型,而且也涉及FACTS控制器的三相数学模型.此外,还探讨了多换流器FACTS控制器的电流、电压以及功率等不等约束在潮流计算中的数学模型及计算机实现.     

基于遗传算法的UPFC模糊阻尼控制器参数优化及与梯度下降法的比较

设计了一种统一潮流控制器（UPFC）模糊辅助控制器,能够阻尼互联系统之间功率低频振荡．分别使用遗传算法和梯度下降法实现了模糊阻尼控制器（FDC）的参数优化。建立了UPFC的频域模型,给出了主控制和辅助控制的框图。推导了模糊阻尼控制器参数优化的公式。互联多机系统算例显示了2种优化方法都具有很好的收敛性。且结果吻合,同时由这2种方法优化的阻尼控制器能够很好地阻尼系统的功率振荡。且比传统的基于线性系统设计的辅助控制器在不同的系统运行方式和振荡模式下具有更好的鲁棒性。     

用于三相电力系统潮流计算的UPFC稳态模型

基于对称分量坐标、用附加节点注入功率法,建立了统一潮流控制器(UPFC)在给定控制方式下计算三相潮流的三序解耦模型;三序解耦潮流采用正序约束条件,UPFC正序模型按附加节点注入功率计算,负序、零序模型按附加节点注入电流计算;结合牛顿—拉夫逊法编制了该潮流计算程序。因潮流可按正序、负序、零序分别求解,在保证求解精度的前提下提高了求解效率。     

UPFC控制器的设计

采用功率模型描述含UPFC的网络方程,在该网络方程基础上并联侧采用电压控制/无功电流控制,串联侧采用自动潮流控制/电压注入的控制策略。提出了UPFC控制器物理实验装置的实现方案。仿真结果证明采用该方法,UPFC能快速有效地改善系统的电压和潮流。     

UPFC稳定控制器的研究及应用

在统一潮流控制器(UPFC)上加装稳定控制器,可以提高弱阻尼系统的阻尼水平,但是稳定控制器安装位置及反馈信号的选择对控制效果影响较大.建立了包含稳定控制器的UPFC的9阶数学模型,该模型考虑了直流电容的动态响应,并且包括了并联侧的电压控制及串联侧的功率控制,可比较详细地反映稳定控制器对UPFC性能的影响,稳定控制器可根据需要安装在UPFC的并联侧或串联侧.基于该UPFC数学模型,在装设了UPFC的弱阻尼连接多机系统中,推导全系统的状态方程,利用全系统状态方程的信息计算UPFC稳定控制器的最佳安装位置及有效的反馈信号,然后使用计算结果设计相应的UPFC稳定控制器.使用EMTDC对一个装设有UPFC两区域弱阻尼连接系统进行了仿真计算,仿真结果表明,利用所提方法设计的UPFC稳定控制器可以明显提高该系统的阻尼水平.     

Quadratic models of AC–DC power flow and optimal reactive power flow with HVDC and UPFC controls

Quadratic models of power flow (PF) and optimal reactive power flow (ORPF) for AC–DC power systems are proposed in the paper. Voltage magnitudes at the two sides of ideal converter transformers are used as additional state variables to build the quadratic models. Effects of converter controls on equality constraints are considered. The quadratic expression of unified power flow controller (UPFC) is also developed and incorporated into the proposed models. The proposed PF model retaining nonlinearity has a better convergence feature and requires less CPU time compared to traditional PF models. The Hessian matrices in the quadratic AC–DC ORPF model are constant and need to be calculated only once in the entire optimization process, which speeds up the calculation greatly. Results obtained from the four IEEE test systems and an actual utility system indicate that the proposed quadratic models achieve a superior performance than conventional models.     

Phase-domain power flows in the rectangular co-ordinates frame of reference including VSC-based FACTS controllers

This paper presents a method for systematic modelling of VSC-based FACTS controllers within three-phase power flows in rectangular co-ordinates. Among the FACTS controllers modelled are the STATCOM, SSSC, UPFC and HVDC-VSC. The approach taken is to represent the fundamental frequency operation of each power converter as a three-phase voltage source behind a leakage reactance, where one or two of them may be connected in either series or parallel depending on the FACTS controller being modelled. Active and reactive power flow equations are developed for each voltage source circuit together with constraint equations to account for co-ordinated operation of two converters, such as in modelling of UPFC and HVDC-VSC. The power flow equations representing the VSC-based FACTS controllers are combined with the nodal power equations of the power network for a combined iterative solution using a Newton–Raphson three-phase power flow algorithm in rectangular co-ordinates enabling robust and efficient solutions of three-phase power networks with any number and kind of VSC-based controllers.     

FACTS技术分析

对柔性交流输电系统及其控制器的分类,工作原理作了完整的介绍。介绍了国内外对ＦＡＣＴＳ控制器的研制和应用情况。对ＦＡＣＴＳ控制器中最具代表性的统一潮流控制器（ＵＰＦＣ）的原理和基本运行状态进行了分析。