四种FACTS装置对改善风光互补系统稳定性的研究

新能源的接入对电力系统稳定性的影响越来越大。FACTS装置在工频下快速调节系统基波潮流来提高系统输送能力和稳定性。对4种典型FACTS装置接入风光互补系统的原理和动态特性进行比较研究, 同时考虑互联系统联络线传送功率、风光互补系统出力等工况影响,设计了附加功率振荡阻尼控制器,通过反馈控制来调节装置可控的系统电气参量,起到阻尼低频振荡的作用。最后,针对算例系统进行了仿真计算,结果表明:UPFC和STATCOM在提高系统机电振荡模式阻尼比、抑制系统低频振荡方面性能优于SVC和TCSC,特别在其并联侧附加阻尼控制器后,能明显降低系统振荡幅度,提高系统稳定性。     

Power oscillation damping control strategies for FACTS devicesusing locally measurable quantities

This paper presents a way to derive power oscillation damping control strategies for flexible AC transmission system (FACTS) devices, and derives these laws for the four major types of FACTS devices using an energy function (Lyapunov) method. All controls rely only on locally measurable information, and are independent of system topology, implying structural uncertainty need not affect power oscillation damping control strategies     

Interaction between phase shifting transformers installed in the tie-lines of interconnected power systems and automatic frequency controllers

FACTS devices like TCPAR can be used to regulate the power flow in tie-lines of interconnected power system. The transient state power flow occurring after power disturbances can be influenced by using TCPAR equipped with power regulator and frequency-based stabilizer. The analysis of a simple interconnected power system consisting of two power systems has shown that the control of TCPAR can force a good damping of both power swings and oscillations of local frequency. In the case of a larger interconnected power system consisting of more than two power systems, the influence of the control of TCPAR on damping can be more complicated. Strong damping of local frequency oscillations and power swings in one tie-line may cause larger oscillations in remote tie-lines and other systems. Hence the use of devices like TCPAR as tools for damping power swings and frequency oscillations in a large interconnected power system must be justified by detailed analysis of power system dynamics. In this paper, some results of time-domain simulations of a three-system area are presented. These results have proven that it is possible to obtain a good damping of tie-line power and frequency swings by optimizing the main parameters of TCPAR installed in tie-lines. The results have been confirmed by an eigenvalue analysis of linearized model of interconnected system consisting of three subsystems.     

Power flow control and power flow studies for systems with FACTSdevices

In this paper, the modeling of flexible AC transmission system (FACTS) devices for power flow studies and the role of that modeling in the study of FACTS devices for power flow control are discussed. FACTS devices are solid-state power converters that have the capability of control of various electrical parameters in transmission circuits. A number of power flow study programs were developed in order to model various types of FACTS devices. Three main generic types of FACTS devices are suggested and the integration of those devices into power flow studies, studies relating to wheeling and interchange power flow control are illustrated     

Power flow control approach to power systems with embedded FACTS devices

This paper focuses on developing an approach to steady-state power flow control of flexible AC transmission systems (FACTS) device-equipped power systems. Based on a power-injection model of FACTS devices and an optimal power flow model, a novel versatile power flow control approach is formulated, which is capable of implementing power flow control incorporating any FACTS device flexibly. Different from existing FACTS device control approaches, the active and (or) reactive power injections are taken as independent control variables. Therefore, using this method, Jacobian matrix need not be changed, although various FACTS devices possess different physical models and different control parameters. Furthermore, it enables the integration of FACTS devices into the existing power system analysis and control programs efficiently. Physical limits of the FACTS devices are also considered in the model. Numerical results on a reduced practical system and a 1500-bus practical system with various FACTS devices are presented to illustrate the vigorousness of the proposed approach.     

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。     

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。     

Coordinated application of FACTS controllers to damp out inter-area oscillations

This paper proposes a systematic analysis and design procedure for simultaneously determining the best locations and input signals of flexible AC transmission system (FACTS) devices in order to damp out inter-area oscillations. First, a modified modal power flow oscillation flow method is developed to determine the nature of the energy exchange over the transmission network in the presence of FACTS devices. With this method, the modal distribution along critical system paths is identified, and the contribution of each machine and network device is computed. Controllability and observability studies are then used to assess the effect of existing FACTS controllers on system damping as well as to identify optimal locations for new devices. The proposed procedure is demonstrated on a 46-machine, 190-bus reduced-order equivalent model of the Mexican interconnected system that includes several static VAR compensators.     

Coordinated control of two FACTS devices for damping interareaoscillations

This paper presents the design and application of a simple controller to damp interarea oscillations. The controller coordinates the control action of a thyristor controlled series capacitor (TCSC) and a thyristor controlled phase angle regulator (TCPAR) to allow for increased power transfers with improved system damping. The controller is based on the application of projective controls and coordinates readily available measurements with control signals applied to the FACTS devices     

Assessment of techno-economic contribution of FACTS devices to power system operation

In contemporary power system studies, the optimal allocation and utilization of Flexible AC Transmission System (FACTS) devices are important issues primarily due to their cost. In this study four types of FACTS devices (Static VAr compensator (SVC), Thyristor-Controlled Series Capacitor (TCSC), Thyristor-Controlled Voltage Regulator (TCVR), and Thyristor-Controlled Phase Shifting Transformer (TCPST)) are optimally placed in a multi-machine power system to reduce the overall costs of power generation. The placement methodology considers simultaneously the cost of generated active and reactive powers and cost of selected FACTS devices for a range of operating conditions. The optimal power flow (OPF) and genetic algorithm (GA) based optimization procedure are employed to solve the allocation task. The net present value (NPV) method is used to assess the economic value of the proposed methodology. In addition to net reduction in generation cost allocated FACTS devices increased power transfer across the network and improved damping of electromechanical oscillations.     

A new formulation for load flow solution of power systems with series FACTS devices

This paper addresses the solution of load flow equations for a power system with series flexible AC transmission systems (FACTS) devices. A novel formulation of equations using dual state variables (current magnitude and angle) and dual control variables (series injected real power and series voltage in quadrature with current) for series devices is proposed. These specifications can be related to transmission line loading and device limits. Specifications like power flow through a series device can also be handled using this formulation. The load flow equations are solved using Newton-Raphson technique. A decoupled formulation is also proposed. Case studies are carried out on IEEE test systems with several types of specifications to validate the method.     

Planning of multi-type FACTS devices in restructured power systems with wind generation

Many electrical power systems are changing from a vertically integrated entity to a deregulated, open-market environment. This paper proposes an approach to optimally allocate multi-type flexible AC transmission system (FACTS) devices in restructured power systems with wind generation. The objective of the approach is to maximize the present value of long-term profit. Many factors like load variation, wind generation variation, generator capacity limit, line flow limit, voltage regulation, dispatchable load limits, generation rescheduling cost, load shedding cost, and multilateral power contracts are considered in problem formulation. The proposed method accurately evaluates the annual costs and benefits obtainable by FACTS devices in formulating the large-scale optimization problem under both normal condition and possible contingencies. The overall problem is solved using both Particle Swarm Optimization (PSO) for attaining optimal FACTS devices allocation as main problem and optimal power flow as sub optimization problem. The efficacy of the proposed approach is demonstrated for modified IEEE 14-bus test system and IEEE 118-bus test system.     

Optimal controllers based on FACTS devices intended for decentralized control of integrated large electrical power systems

The decentralized synthesis of stabilizing controllers based on FACTS devices in an integrated electrical power system (IEPS), which secures minimum energy consumption for control, has been examined. This task can be solved with the help of decomposition and aggregation of the initial model of the IEPS to regional electric power systems (REPS) (subsystems). For aggregated models of the subsystems, a control is synthesized based on Riccati’s quadratic equations or, in the case of asymptotical stability of aggregated models of the sub-system, based on Lyapunov’s linear equations.     

State-variable control of shunt FACTS devices using phasor measurements

This paper addresses the problem of state-variable stabilizing control of power system using shunt FACTS devices. This stabilizing control is activated in the transient state of a power system and is supplementary with respect to the main steady-state control of a FACTS device. Stabilizing control laws have been derived for a non-linear multi-machine system model using direct Lyapunov method with the aim to maximize the rate of energy dissipation during power swings and therefore maximization of damping. The proposed control strategy is executed by a non-linear multi-loop controller with rotor angles and speed deviations of synchronous generators used as the input signals. The input signals, obtained from a phasor measurement system, are necessary only from a small area around the controlled shunt FACTS device. Validity of the proposed state-variable control has been confirmed by computer simulation for a small multi-machine test system.     

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。     

考虑柔性交流输电系统设备控制的校正型安全约束最优潮流

为提升安全约束最优潮流调度的经济性与安全性,提出一种基于直流潮流的考虑柔性交流输电系统(FACTS)设备控制的校正型安全约束最优潮流模型。在线路故障发生后,通过FACTS设备校正措施,将线路潮流控制在其容许范围内。由于所提模型为大规模的非凸、非线性优化问题,难以直接求解,因此先采用大M法,将原非线性优化模型转换为混合整数线性规化模型,并采用Benders分解算法将转换后的模型分解为基态最优潮流主问题与N-1故障校验子问题。通过固定整数变量的方法,将非凸的混合整数优化子问题转换为线性规划子问题,从而能向主问题返回对应的Benders割。6节点系统与IEEE RTS-79节点系统算例验证了所提模型与算法的有效性。结果表明,考虑FACTS设备校正控制的安全约束最优潮流能有效提升调度运行的经济性。     

基于主模比的FACTS阻尼控制器广域信号选取方法

FACTS阻尼控制器的广域信号选取是影响控制器效果的重要因素,提出了一种基于主模比指标的选取方法。对单输入输出系统建立辨识模型,提出主模比指标;利用Prony辨识手段,计算复杂多机系统各个反馈信号的主模比;通过一个标准3机系统验证主模比指标确定广域反馈信号的可行性;以川渝电网为实际案例,比较了广域阻尼与本地信号的静止无功补偿器控制效果的差异。仿真结果表明,该方法能有效改善系统动态稳定性。     

A new dynamic control strategy for power transmission congestion management using series compensation

The growth of electricity market due to increase in demand and infrastructure made the power system more complex. Managing the transmission congestion is one of the main challenges faced by the utilities. To relieve from the bottlenecks, Flexible AC Transmission Systems (FACTS) and Distributed FACTS (D-FACTS) devices can be used in controlling the transmission line power flows. The real power flow control is realized by varying the transmission line impedance. The power flow in transmission line should satisfy inequality constraints to maintain the system in normal state. To achieve this, an algorithm is developed to control the FACTS/D-FACTS devices connected to all the transmission lines of n-bus system. The significant changes required in line impedance which will be deployed by FACTS devices are decided by the algorithm. In this paper, a 5 bus system and a 14 bus system with FACTS devices in all the transmission lines is considered. The transmission lines of the 5 and 14 bus systems are made to be overloaded in different combinations by choosing appropriate loading conditions. The control algorithm is tested on all the overloaded conditions to overcome the congestion. The FACTS devices controlled by the algorithm removes the overloading effect and improve the reliability of the network.     

TCSC controller design for damping interarea oscillations

The thyristor controlled series compensator (TCSC), a prominent FACTS device, can rapidly modulate the impedance of a transmission line, resulting in improvement of power system performance. The purpose of the work reported in this paper is to design a controller to damp interarea oscillations. The authors have applied the residue method to linearized power system equations and obtained a generalized form which is suitable for different controller input/output channels and therefore suitable for different control devices. This method, together with modal sensitivities, is applied to TCSCs to determine the location, feedback signal and controller design. The damping result is illustrated by comparing changes in damping ratio and identifying the increase of transfer capacity     

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.