基于PSCAD/EMTDC的统一潮流控制器动态仿真模型

设计了组成统一潮流控制器(UPFC)的动态仿真模型的各个模块,包括正弦脉宽调制(SPWM)信号产生模块、电压源变换器(VSC)控制模块和UPFC控制器的比例积分(PI)控制电路.首先采用三相桥式全控电路组成VSC,VSC的开关器件采用绝缘栅双极性晶体管(IGBT),门极信号按SPWM的方式产生.然后通过分析线路传输功率方程设计了一个简单的PI控制器,并构成完整的UPFC仿真模型.还基于该动态模型对UPFC在功率调节、电压控制和抑制振荡等方面的功能进行了仿真分析.仿真结果表明该UPFC仿真模型在线路功率发生较大变动时能使线路快速恢复;在系统发生三相短路时能有效减少系统的功率损失和减小母线电压的暂降幅度;在系统发生功率波动时还能大幅度减小振幅.     

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.     

Investigation of SSR characteristics of unified power flow controller

The unified power flow controller (UPFC) is the most versatile flexible ac transmission system (FACTS) controller which can be used to control active and reactive power flows in a transmission line in addition to the bus voltage. The active series compensation is provided by injecting series reactive voltage. The voltage at the two ports of UPFC are regulated by control of shunt current and series real voltage. It also has several operating control modes such as voltage and power regulation, line impedance compensation, etc. This paper presents the analysis and study of sub-synchronous resonance (SSR) characteristics of UPFC. The various combination of operating modes of shunt and series converters are considered for investigating their effect on SSR characteristics.The analysis of SSR with UPFC is carried out based on frequency domain method, eigenvalue analysis and transient simulation. The frequency domain method considers D-Q model of UPFC for the computation of damping torque for quick check in determining torsional mode stability. The study is performed on IEEE First Benchmark Model (FBM).     

Unified power flow controller models for three-phase power flow analysis

In this paper, three models of the unified power flow controller (UPFC) suitable for three-phase power flow analysis in polar coordinates are presented. The symmetrical components control model can be used to control the positive-sequence voltage of the shunt bus and the total three-phase active and reactive power flows of the transmission line while the injected shunt voltages and the series voltages are balanced, respectively; the general three-phase control model can be used to control the three shunt phase voltages and the six independent active and reactive power flows of the transmission line; the hybrid control model can be used to control the positive-sequence voltage of the shunt bus and the six independent active and reactive power flows of the transmission line. The proposed UPFC models were successfully implemented in a three-phase Newton power flow algorithm in polar coordinates. In the implementation of these UPFC models, transformers of some common connection types, which connect the UPFC with the network, are explicitly represented. Numerical results based on a five-bus system and the modified IEEE 118-bus system are given to illustrate the UPFC control models and demonstrate the computational performance of the three-phase Newton power flow algorithm.     

Real and reactive power coordination for a unified power flow controller

This paper proposes a new real and reactive power coordination controller for a unified power flow controller (UPFC). The basic control for the UPFC is such that the series converter of the UPFC controls the transmission line real/reactive power flow and the shunt converter of the UPFC controls the UPFC bus voltage/shunt reactive power and the DC link capacitor voltage. In steady state, the real power demand of the series converter is supplied by the shunt converter of the UPFC. To avoid instability/loss of DC link capacitor voltage during transient conditions, a new real power coordination controller has been designed. The need for reactive power coordination controller for UPFC arises from the fact that excessive bus voltage (the bus to which the shunt converter is connected) excursions occur during reactive power transfers. A new reactive power coordination controller has been designed to limit excessive voltage excursions during reactive power transfers. PSCAD-EMTDC simulation results have been presented to show the improvement in the performance of the UPFC control with the proposed real power and reactive power coordination controller.     

统一潮流控制器附加阻尼抑制次同步谐振的理论与仿真

随着串联电容补偿输电的推广应用,中国电力系统面临着严峻的次同步谐振(SSR)问题。针对SSR问题,文中基于采用电流控制模式的统一潮流控制器(UPFC),提出了一种UPFC附加阻尼控制抑制SSR的方法;首先选择了附加阻尼控制信号接入UPFC控制器的位置,然后设计了UPFC附加次同步阻尼控制器(SSDC),并推导了其抑制系统SSR的机理,且所设计的SSDC采用了模态分离控制以达到抑制多模态SSR的目的。最后,综合利用复转矩系数和时域仿真的方法,对所设计的UPFC装置SSDC抑制SSR的有效性进行了分析和仿真。结果表明,所设计的SSDC在有效抑制SSR的同时,不会影响系统和UPFC装置的正常运行。     

Superconducting magnetic energy storage controller design and stability analysis for a power system with various load characteristics

A simultaneous active power and reactive power (P–Q) control scheme of superconducting magnetic energy storage (SMES) unit is proposed to enhance the damping of a power system. In order to control the P–Q modulation to the power system, a proportional-integral (PI) controller is used to provide a supplementary damping signal. The parameters of the PI controller are determined by a systematic pole assignment method based on modal control theory. Both static load and dynamic load are included to improve the system model fidelity. Eigenvalue analysis and time-domain nonlinear simulation, using a power system incorporating a composite load, are illustrated to validate the effectiveness of the proposed PI SMES controller for the damping of the studied system over a wide range of operating conditions. The control scheme also shows that the stability margin of the power system is expanded.     

统一潮流控制器的建模与控制研究综述

灵活交流输电系统（ＦＡＣＴＳ）技术是近几年来出现的一项新技术,统一潮流控制器（ＵＰＦＣ）是ＦＡＣＴＳ控制器中乞今最全面的控制器,可提供对传输线路参数（即电压、线路阻抗和相角）的全面动态控制,能够快速控制传输线路的有功和无功功率及母线电压。首先由考虑ＵＰＦＣ的电力系统潮流调节问题讨论了ＵＰＦＣ的建模,然后从控制角度综述了目前国内外研究ＵＰＦＣ的最新成果,概述了ＵＰＦＣ的各种控制策略,并分析了ＵＰＦＣ     

基于振荡能量下降原理的UPFC模糊控制器设计

研究了自适应统一潮流控制器(U PFC)模糊逻辑辅助阻尼控制器的设计方法。从振荡能量函数角度分析了U PFC安装线路的功率振荡特性,提出了以降低振荡能量为控制目标的阻尼控制策略。控制器以U PFC线路的功率为输入信号,通过对系统运行状态和控制效果进行评判,应用模糊规则自适应地调节控制参数,实现对系统功率振荡的有效抑制。控制器设计不需要系统的精确模型和参数。在10机新英格兰测试系统上的仿真研究表明,该控制器控制效果明显优于线性控制器,能有效抑制系统低频振荡,提高电力系统的动态稳定性水平,且具有较强的鲁棒性。     

统一潮流控制器的自适应校正稳定控制器设计

在装设了统一潮流控制器(unified power flow controller,UPFC)的弱阻尼连接多机系统中,综合利用全系统的线性化状态方程和传递函数的信息,设计了线性化的UPFC稳定控制器。为使该稳定控制器能在系统大范围内的运行点提供有效阻尼,文中在UPFC稳定控制器中加入一可调的超前(滞后)环节,利用Prony分析在线辨析系统低频振荡特性。利用在线辨析的结果对稳定控制器的可调环节进行微调,使之针对系统具体运行工况进行自适应校正,从而持续工作在最佳状态。最后利用电磁暂态仿真程序对一个装设有UPFC的两区域弱阻尼连接系统进行了仿真计算。仿真结果表明,文中设计的自适应校正UPFC稳定控制器能够明显提高该系统的阻尼水平。     

A SVD based controller of UPFC for power flow control

Unified Power Flow Controller (UPFC) is a versatile Flexible AC Transmission System (FACTS) device that has the capability of controlling voltage, power flow, and stability of a power system. It has been reported that the control of power flow by a UPFC introduces very strong dynamic interactions between the active and reactive power flow through a line. In this paper, a singular value decomposition (SVD) based controller of UPFC is proposed to reduce or eliminate the dynamic interaction between the active and reactive power flow. The performance of the proposed SVD controller is evaluated in both ideal and practical systems. The results obtained are then compared with those found for the static decoupled (SD) and PI controllers. It is observed that the proposed SVD controller can significantly reduce the dynamic interaction between the active and reactive power flow through the line and it is achieved by decoupling the interaction between the direct and quadrature axes control variables.     

Control algorithms for control of real and reactive power flows and power oscillation damping using UPFC

This paper investigates the application of multivariable control technique to multi-input multi-output (MIMO) non-linear problem of a power transmission system with UPFC. The main objective is to achieve effective independent control of real and reactive power flows with zero dynamic interactions. Towards achieving the objective, feed-back linearization control (FBLC) scheme is implemented in the laboratory for the control of UPFC. A two-bus power system with UPFC has been built in laboratory and the control implementation has been carried out using DSP TMS320LF2407A. Both power flow control and power oscillation damping issues are addressed. The excellent correlation between simulation and experimental results using a laboratory test system establish the validity of the proposed scheme. Although the power stage of the developed laboratory system is a scaled down model and has limited ratings, the FBLC controller can be used equally effectively in a more realistic system set up by appropriate scaling factors for the fed-back signals of currents and voltages and for initiating the inverter voltages. The proposed controller enables UPFC to independently control the real and reactive power with absolute decoupling. Also it is found that the overall performance of the system with the proposed controller is far superior to that using conventional cascade PI control structure.     

UPFC控制及动态特性实验研究

基于传统的比例—积分控制,提出了统一潮流控制器(unified power flow controller,UPFC)并、串联侧解耦的系统级控制策略,其控制目的是在并联侧维持UPFC并入点的交流电压和直流侧电容电压,在串联侧控制线路有功、无功潮流。文章首先介绍了所研制的UPFC实验系统平台,并在此基础上详细地给出了UPFC系统级控制器的硬件实现,实验平台的通用性决定了不同控制策略可以较容易地实现。为验证所提出的控制策略的控制效果,文中将UPFC实验装置嵌入至自行搭制的等效双机实验系统中,实验结果与 PSCAD/EMT DC仿真环境下的时域动态仿真结果十分相似,从而得到了良好的UPFC动态特性。     

统一潮流控制器的控制系统分析及控制策略设计

详细分析了统一潮流控制器（ＵＰＦＣ）的控制系统,并将其分为主控制和辅助控制两部分。对于主控制中的串联侧控制,提出了４种基本控制方式,并以加权的方式实现ＵＰＦＣ的多种功能综合控制,使得ＵＰＦＣ的多功能优化问题转化为各杖值的动态优化问题。ＵＰＦＣ的辅助控制则通过联络线的功率反馈或电压相位差反馈对主控制中的控制参考值进行调制以增加系统阻尼。最后,综合主控制与辅助控制,提出了ＵＰＦＣ的动态控制策略,使得系     

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。     

Comparison of different robust control methods in design of decentralized UPFC controllers

The unified power flow controller (UPFC) integrates properties of both shunt and series compensations, and can effectively alter power system parameters in such a way that increases power transfer capability and enhances system stability. In practice, simple proportional–integral (PI) controllers are used to control the UPFC. However, the PI control parameters are usually tuned based on classical or trial-and-error approaches and as such, they are incapable of obtaining good dynamic performance for a wide range of operating conditions and various loads in power systems. Hence, in this article robust control approaches are proposed based on the quantitative feedback theory (QFT), H_∞ loop-shaping and μ-synthesis, to design UPFC controllers (power-flow and DC-voltage regulator). The three mentioned methods are compared with each other and a supplementary damping controller is developed to improve damping power system oscillations. Here, a single-machine infinite-bus (SMIB) power system, installed with a UPFC (with system parametric uncertainties) is considered as a case study. The system parametric uncertainties are obtained following 40% simultaneous alterations in parameters and load from their typical values. The simulation results indicate satisfactory verifications of the robust control methods in dealing with the uncertainties considered. When the above three methods and the PI controller are compared in performance in several time-domain simulation tests, the results show clear superiority of the three methods over the PI controller, with the QFT presenting the best performance amongst the three robust control.     

统一潮流控制器的分析与控制策略

文中分析了统一潮流控制器（UPFC）系统的电压、无功功率和有功功率的平衡,得到了与UPFC控制相关的2个重要结论。首先,分析表明在UPFC输入端电压保持不变的情况下,线路无功潮流的变化实际上是由并联变换器提供的;其次,UPFC端电压既可以从发送端控制也可以从接收端控制。基于以上分析,提出了一种新颖的UPFC控制策略。在该策略中并联变换器控制UPFC直流母线电压和输电线无功潮流,而串联变换器控制UPFC输入端母线电压幅值和输电线有功潮流。同时,在控制系统中加入有功／无功功率协调控制,可在潮流调节中获得良好的静态、动态性能。最后,通过实验验证了所提出的控制策略的有效性。     

统一潮流控制器(UPFC)对次同步振荡的影响及抑制策略

FACTS等快速控制装置在一定条件下可能激发电力系统的次同步振荡问题,导致发电机轴系失稳,造成重大事故,危害电力系统的安全稳定运行。UPFC作为一种新型FACTS元件,虽然能实现母线电压控制和线路有功、无功功率的调节,但对次同步振荡影响的研究较少。同时,目前的UPFC阻尼控制器多针对低频振荡模态。故在搭建UPFC模型的基础上,运用测试信号法,研究了系统运行参数和UPFC电压有功控制等对次同步振荡的影响,并设计了相应的UPFC附加阻尼控制器。在IEEE第二标准测试系统上的计算机仿真说明,该控制器能有效提高多个扭振模态的电气阻尼,抑制系统的次同步振荡。     

一种新型统一潮流控制器

传统统一潮流控制器（UPFC）价格昂贵,损耗高,谐波含量高,在电力系统中不能很好地推广使用。文中提出一种混合型UPFC,它由“Sen” Transformer（ST）和传统UPFC串联组成,ST通过控制普通的有载调压开关,实现360°离散可调串联电压,UPFC利用电力电子开关原理实现360°连续可调的串联电压,两者共同工作起到控制系统潮流的作用。与传统大容量UPFC相比,混合型UPFC使用小容量UPFC,能够达到大容量UPFC的潮流控制范围,具有成本低、效率高、电磁兼容性好、谐波含量低、易于实现的优点,解决了导致现阶段UPFC不能推广使用最为重要的成本问题。混合型UPFC是具有极高性价比和效率的潮流控制器件,具有广阔的应用前景。     

利用多端统一潮流控制器阻尼多模态振荡

研究了多机系统中使用统一潮流控制器(UPFC)抑制电力系统多模态振荡的可行性.首先推导了作为UPFC概念延伸的多端统一潮流控制器(MUPFC)的非线性动态模型和线性化的Phillips-Heffron模型.利用UPFC和MUPFC具有多个控制回路的特点,提出在其多个控制回路上附加多个阻尼控制器来阻尼多模态振荡.通过模态分析,采用可控性指标对系统中的各个弱阻尼模态选取有效的控制回路,并设计了附加阻尼控制器.仿真结果表明,通过该方法确定的在一个UPFC或MUPFC上设置的多个附加阻尼控制器能够成功实现对电力系统多模态振荡的抑制.