含广义统一潮流控制器(GUPFC)的最优潮流模型和算法研究

广义统一潮流控制器(GUPFC)作为比统一潮流控制器(UPFC)控制能力更强大的FACTS装置，其对最优潮流(Optimal Power Flow)的影响需要深入地研究。根据GUPFC的控制原理，基于功率注入法建立了含GUPFC的OPF数学模型，并采用基于信赖域内点法的最优潮流算法予以求解。该算法采用多步中心校正原一对偶内点法连续求解线性规划子问题，通过信赖域决定线性化步长的选取。对IEEE30和118节点系统作了数值计算，结果表明，GUPFC不仅可控制节点电压而且可控制多条线路潮流，显示出强大的控制能力，同时也说明了含GUPFC的OPF数学模型和算法的可行性和有效性。     

Optimal power flow by BAT search algorithm for generation reallocation with unified power flow controller

Optimal power flow with generation reallocation is a suitable method for better utilization of the existing system. In recent years, Flexible AC Transmission System (FACTS) devices, have led to the development of controllers that provide controllability and flexibility for power transmission. Out of the FACTS devices unified power flow controller (UPFC) is a versatile device, capable of controlling the power system parameters like voltage magnitude, phase angle and line impedance individually or simultaneously. The main aim of this paper is to minimize real power losses in a power system using BAT search algorithm without and with the presence of UPFC. Minimization of real power losses is done by considering the power generated by generator buses, voltage magnitudes at generator buses and reactive power injection from reactive power compensators. The proposed BAT algorithm based Optimal Power Flow (OPF) has been tested on a 5 bus test system and modified IEEE 30 bus system without and with UPFC. The results of the system with and without UPFC are compared in terms of active power losses in the transmission line using BAT algorithm. The obtained results are also compared with Genetic algorithm (GA).     

计及FACTS装置的可用输电能力计算

利用功率注入法,建立广义统一潮流控制器(generalized unified power flow controller,GUPFC)和线间潮流控制器(interline power flow controller,IPFC)的数学模型。将GUPFC和IPFC的目标控制约束及运行约束即内部功率平衡约束和考虑等效功率注入模型的潮流约束嵌入到最优潮流计算模型中,得到计及GUPFC和IPFC的可用输电能力(available transfer capability,ATC)计算模型,并利用跟踪中心轨迹内点法对模型进行求解。IEEE-30节点系统的仿真计算显示GUPFC对节点电压和多条线路甚至某一子网络潮流的灵活控制能力及IPFC对线间潮流的合理分配能力;同时验证模型和算法的有效性和可行性。     

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。     

ATC with ZIP load model – A comprehensive evaluation with third generation FACTS in restructured electricity markets

In this paper, an optimal power flow based approach has been applied for multi-transactions in deregulated environment for ATC determination with third generation FACTS devices. The main contribution of the paper is (i) OPF based approach for evaluation of ATC with multi-transactions, (ii) ATC enhancement with third generation FACTS devices viz. Static Compensator (STATCOM), Static Synchronous Series Compensator (SSSC), and Unified Power Flow Controller (UPFC) for intact and line contingency cases (iii) Impact of ZIP load on ATC determination and comparison of ATC obtained with ZIP load model and constant P,Q load model, (iv) Comparison of ATC obtained with DC/AC-PTDFs based method along with FACTS devices for comparison. The results have been determined for intact and line contingency cases taking simultaneous as well as single transaction cases for IEEE 24 bus RTS.     

Constraints Violation Handling of GUPFC in Newton-Raphson Power Flow

Generalized Unified Power Flow Controller (GUPFC) is one of the newest Flexible AC transmission system (FACTS) devices based on voltage source converters. This paper presents a developed model of GUPFC based on power injection approach. The series converters of GUPFC is represented by injected complex loads as function of the specified powers flow, while the shunt converter is represented as a synchronous condenser that provides the reactive power compensation to control the bus voltage magnitude. The main advantage of the developed model is that the original structure and symmetry of the admittance and Jacobian matrices can still be kept avoiding the changes of the original Jacobian matrix. Consequently, the complexities of the load flow are reduced. This model includes simple strategies for handling the operating constraints of GUPFC, including the injected series and shunt voltages magnitude, currents of the series and shunt converters, and the real powers exchanged in the converters. The strategies are based on decreasing one or more values of specified values or by modifying the specified values as a function of the required constraint limits. The developed model and proposed strategies for handling violation of GUPFC operating constraints are tested on IEEE test systems such as 57-bus and 118-bus systems.     

Optimal power flow with FACTS devices by hybrid TS/SA approach

In this paper, a hybrid tabu search and simulated annealing (TS/SA) approach is proposed to minimize the generator fuel cost in optimal power flow (OPF) control with flexible AC transmission systems (FACTS) devices. The problem is decomposed into the optimal setting of FACTS parameters subproblem that is searched by the hybrid TS/SA approach and the OPF with fixed FACTS parameters subproblem that is solved by the quadratic programming (QP). Two types of FACTS devices are used: thyristor-controlled series capacitor (TCSC) and thyristor-controlled phase shifting (TCPS). Test results on the modified IEEE 30 bus system indicates that the proposed hybrid TS/SA approach can obtain better solutions and require less CPU times than genetic algorithm (GA), SA, or TS alone.     

Power flow control and solutions with multiple and multi-type FACTS devices

In this paper, a new generalized current injection model of the modified power system using Newton–Raphson power flow algorithm has been proposed for desired power transfer with Flexible AC Transmission Systems (FACTS) devices. So that the FACTS devices can be incorporated in the proposed algorithm and, therefore, whole system with these devices can be easily converted to power injection models without change of original admittance and the Jacobian matrices. Power flow algorithm has been modeled in such a way that it can easily be extended to multiple and multi-type FACTS devices by adding a new Jacobian corresponding to that new device only. Power flow algorithm with the presence of Thyristor Controlled Series Compensators (TCSC), Unified Power Flow Controller (UPFC), and Generalized Unified Power Flow Controller (GUPFC) has been formulated and solved. To demonstrate the performance of the proposed algorithm for multiple and multi-type FACTS devices, different case studies of IEEE 30-bus system has been considered and the results are tabulated. The proposed algorithm is independent of the size of the system and initial starting conditions of the FACTS devices.     

含UPFC的灵活交流输电系统最优潮流控制

潮流计算和无功优化计算是电力系统非常重要的计算,两者都包括在电力系统最优潮流（OPF）问题中,灵活交流输电系统（FACTS）的出现需要对传统的潮流计算进行修正,利用遗传算法探讨了含统一潮流控制器（UPFC）的灵活交流输电系统最优潮注控制问题,计算机仿真表明,该方法可有效解决含UPFC的灵活交流输电最优潮流控制。     

Application of particle swarm optimization technique for optimal location of FACTS devices considering cost of installation and system loadability

This paper presents the application of particle swarm optimization (PSO) technique to find the optimal location of flexible AC transmission system (FACTS) devices with minimum cost of installation of FACTS devices and to improve system loadability (SL). While finding the optimal location, thermal limit for the lines and voltage limit for the buses are taken as constraints. Three types of FACTS devices, thyristor controlled series compensator (TCSC), static VAR compensator (SVC) and unified power flow controller (UPFC) are considered. The optimizations are performed on the parameters namely the location of FACTS devices, their setting, their type, and installation cost of FACTS devices. Two cases namely, single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC and UPFC) are considered. Simulations are performed on IEEE 6, 30 and 118 bus systems and Tamil Nadu Electricity Board (TNEB) 69 bus system, a practical system in India for optimal location of FACTS devices. The results obtained are quite encouraging and will be useful in electrical restructuring.     

Analysis of subsynchronous resonance with generalized unified power flow controller

The Generalized Unified Power Flow Controller (GUPFC) is one of the most versatile flexible ac transmission system (FACTS) controllers which controls the active and reactive power flows in multiple transmission lines originating from a substation while controlling the sending end bus voltage. The sending end bus voltage is regulated by control of shunt reactive current while the active and reactive power flows in the transmission line are regulated by series injected voltages. This paper reports the analysis and study of Subsynchronous Resonance (SSR) characteristics of hybrid compensated system with GUPFC. The various operating mode combinations of series and shunt converters are considered to investigate their effect on SSR characteristics. The methods of analysis of SSR with GUPFC is based on the evaluation of damping torque, eigenvalues of the system and transient simulation. The computation of damping torque considers D–Q model of GUPFC to determine the torsional mode stability. The study is performed on a system adapted from IEEE Second Benchmark Model (SBM). The results demonstrate the effectiveness of series real injected voltage in mitigating the SSR.     

Analysis of FACTS devices on Security Constrained Unit Commitment problem

This paper focuses on solving Security Constrained Unit Commitment (SCUC) problem using ABC algorithm incorporating FACTS devices. The objective of the SCUC problem is to obtain the minimum operating cost simultaneously maintaining the security of the system. The SCUC problem is decomposed into Unit Commitment (UC), the master problem and Security-Constrained Economic Dispatch (SCED) as the sub-problem. The existing generation constraints, such as hourly power demand, system reserves, and minimum up/down time limits, ramp up/down limits are included in the SCUC problem formulation. The ability of FACTS devices to control the power flow through designated routes in transmission lines and thereby reducing the overloading of lines are studied. The solution of SCUC problem is also analyzed during a single line outage contingency. The SCUC is carried out incorporating FACTS devices such as SVC, TCSC, STATCOM, SSSC, UPFC and IPFC. The modeling of the FACTS devices within the power system network and finding a suitable location are discussed. The SCUC has been solved and validated on an IEEE 118-bus test system and a practical South Indian 86 bus utility.     

FACTS对电力系统静态安全性影响评价指标体系研究

针对目前评价灵活交流输电系统（FACTS）系统稳态性能影响指标的不足,结合FACTS设备自身控制潮流和电压的工作特性,提出了一套全面评估FACTS设备对系统静态安全性影响的指标体系。建立了基于运行状况的晶闸管控制串联电容器（TCSC）、静止无功补偿器（SVC）、统一潮流控制器（UPFC）可靠性模型,并基于该模型提出了FACTS设备的控制策略,该策略以状态量越限值最小为控制目标。建立了采用蒙特卡罗仿真的概率评估算法。通过IEEE-57节点的计算验证了所提指标体系和算法的有效性。     

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.     

FACTS元件的动态特性分析

ＦＡＣＴＳ（柔性交流输电系统）元件在系统中具有良好的动态特性,充分了解这些特性可以更好地发挥其调节系统潮流、提高系统暂态稳定性的作用。研究了ＵＰＦＣ（统一潮流控制器）的动态可行域,指出了ＵＰＦＣ的动态可行域为类似于椭圆的区域。研究了电力系统中多个ＦＡＣＴＳ元件动态之间的相互影响,仿真分析表明ＦＡＣＴＳ元件之间存在控制协调问题。由于目前电力系统通信技术的局限性,实现ＦＡＣＴＳ元件之间的协调控制有一定     

Robust modeling of the interline power flow controller and the generalized unified power flow controller with small impedances in power flow analysis

The interline power flow controller (IPFC) and the generalized unified power flow controller (GUPFC) are two innovative configurations of the convertible static compensator (CSC) of FACTS. In this paper, direct modeling of the practical series or/and shunt operating inequality constraints of the IPFC and the GUPFC in power flow calculations are presented. Special initialization of a solution with the IPFC and GUPFC is also derived. Furthermore, an impedance compensation technique is proposed to deal with the numerical instability or the numerical difficulty of the IPFC and GUPFC models when either their coupling transformer impedances are too small or they are transformer-less controllers. Condition number analysis of the Newton power flow equations is given to get insights of the numerical instability of the voltage sourced models of the IPFC and GUPFC with small impedances. Numerical examples are given based on the IEEE 118-bus system, IEEE 300-bus system and a large scale system with 1000-buses.     

Analysis of radial distribution systems with embedded series FACTS devices using a fast line flow-based algorithm

Analysis of radial distribution systems with embedded series Flexible AC Transmission System (FACTS) devices is facilitated by a formulation of power flow equations with bus voltage magnitudes and line flows as independent variables. Since control variables such as the line and bus reactive powers figure directly in the formulation, handling the control action of FACTS devices in distribution systems is direct and easily implemented. Using the Breadth-First-Search (BFS), the bus incidence matrix of a radial distribution system is first rendered strictly upper diagonal, leading to reduced computational effort. All the common FACTS device models under steady-state conditions are easily incorporated in the new framework by a simple process of "variable swapping." Using IEEE standard systems, the line flow-based (LFB) formulation is shown to provide easy implementation with multiple series and shunt FACTS devices in the system and enable direct evaluation of the FACTS device ratings.     

基于非线性内点方法的含有串联柔性输电系统装置的阻塞调度

提出了一种基于非线性内点方法的含有串联FACTS装置的阻塞调度方法。针对调节线路有功潮流问题选取了串联FACTS装置的控制参数和模型，并把FACTS对系统的调节作用表述成附加功率的形式。不引入FACTS的控制目标方程，而是在包含FACTS控制参数的变量空间内进行寻优，可以考虑FACTS的多种调节方式。该方法具有较好的鲁棒性和收敛性，易于利用原有的潮流优化算法和程序。     

A current-based model of the static synchronous series compensator (SSSC) for Newton–Raphson power flow

In this paper, a new approach to modeling a static synchronous series compensator (SSSC) for power-flow calculations by applying the Newton–Raphson method is presented. This new approach differs from known methods in terms of the interpretation of the device's branch. It is considered on the basis of its current and is therefore denoted as a current-based model of an SSSC. This approach might in principle be applicable also for other FACTS devices (i.e., UPFC, IPFC, GUPFC). In the paper, the current-based model of an SSSC is presented as the models of this device have difficulties with convergence in power-flow calculations and there are very few references covering these topics. First, the basic features of an SSSC are presented, as it is the basis for the current-based model that is incorporated into the Newton–Raphson load-flow model. The results of the tests at the IEEE 57-bus system are discussed in detail and compared with the existing injection SSSC load-flow model [X.P. Zhang, Advanced modeling of the multicontrol functional static synchronous series compensator (SSSC) in Newton power flow, IEEE Trans. Power Syst. 18 (November (4)) 2003].     

含统一潮流控制器装置的电力系统动态混合仿真接口算法研究

提出了一种新的含UPFC装置的电力系统动态混合仿真接口算法，算法中对UPFC采用动态相量建模，对电力系统网络则采用成熟的机电暂态仿真。仿真中UPFC并联侧采用定交流母线电压控制和定直流电容电压控制，串联侧采用定线路潮流控制。文中推导了UPFC的动态相量模型，讨论了与网络机电暂态模型的接口算法。研究分析和算例仿真表明：使用动态相量建模可精确地仿真UPFC的电磁暂态（EMT）过程，且仿真速度快；文中所提混合仿真方案能保证较快的仿真速度和优良的仿真精度，具有较好的收敛性，且可用于含UPFC等FACTS装置的系统发生不对称故障时的暂态稳定分析。