Design of an ANN tuned adaptive UPFC supplementary damping controller for power system dynamic performance enhancement

A supplementary damping controller for a unified power flow controller (UPFC) is designed for power system dynamic performance enhancement. To maintain a good damping characteristic over a wide range of operating conditions, the gains of the UPFC supplementary damping controller are adapted in real time, based on online measured transmission line loadings (active and reactive power flows). To speed up the online gain adaptation process, an artificial neural network is designed. A major feature for the proposed adaptive UPFC supplementary damping controller is that only physically measurable variables (active and reactive power flows over the transmission line) are employed as inputs to the adaptive controller. To demonstrate the effectiveness of the proposed adaptive UPFC supplementary damping controller, computer simulations are performed on a power system subject to a three-phase fault. It is concluded from the simulation results that the proposed adaptive UPFC supplementary damping controller can yield satisfactory dynamic responses over a wide range conditions. The electromechanical mode with an oscillation frequency around 0.78 Hz has been effectively damped by the proposed damping compensators.     

Robust SVC controller design for improving power system damping

The design of a robust controller for a static VAr compensator (SVC) to improve the damping of a power system is presented. The main contributions of the paper are to formulate and to solve the power system damping control problem using robust optimization techniques, and to synthesize the controller with explicit consideration of the system operating condition variations. Nonlinear simulations using the PSCAD/EMTDC software packages have been conducted to evaluate the performance of the closed-loop system. The results have indicated that the designed controller can provide positive damping to the system under a wide range of operating conditions     

A QFT-based robust SVC controller for improving the dynamic stability of power systems

A new design technique for an SVC-based power system damping controller has been proposed. The controller attempts to place all plant poles within a specified region on the s-plane to guarantee the desired closed loop performance. The use of Horowitz's quantitative feedback theory (QFT) permits the design of a `fixed gain controller' that maintains its performance in spite of large variations in the plant parameters during its normal course of operation. The required controller parameters are arrived at by solving an optimization problem that incorporates the control specifications. The performance of this robust controller has been evaluated on a single machine infinite bus system equipped with a mid point SVC, and the results are shown to be consistent with the expected performance of the stabilizer.     

A self-tuning fuzzy PI controller for TCSC to improve power system stability

In this paper, a self-tuning fuzzy PI controller (STFPIC) is proposed for thyristor-controlled series capacitor (TCSC) to improve power system dynamic performance. In a STFPIC controller, the output-scaling factor is adjusted on-line by an updating factor (α). The value of α is determined from a fuzzy rule-base defined on error (e) and change of error (Δe) of the controlled variable. The proposed self-tuning controller is designed using a very simple control rule-base and the most natural and unbiased membership functions (MFs) (symmetric triangles with equal base and 50% overlap with neighboring MFs). The comparative performances of the proposed STFPIC and the standard fuzzy PI controller (FPIC) have been investigated on two multi-machine power systems (namely, 4 machine, 2 area system and 10 machine 39 bus system) through detailed non-linear simulation studies using MATLAB/SIMULINK. From the simulation studies it has been found out that for damping oscillations, the performance of the proposed STFPIC is better than that obtained by the standard FPIC. Moreover, the proposed STFPIC as well as the FPIC have been found to be quite effective in damping oscillations over a wide range of operating conditions and are quite effective in enhancing the power carrying capability of the power system significantly.     

An adaptive controller for power system load-frequency control

An adaptive controller is presented for load-frequency control of power systems. It uses a PI (proportional-integral) adaptation to satisfy the hyperstability condition for taking care of the parameter changes of the system. Only the available information on the states and output are required for the control. No explicit parameter identification is needed. The controller can be designed by using a reduced plant model to simplify the design without degrading the performance much, so it is very easy to implement practically. The simulation results indicate that good control performance can be obtained and that the performance is sensitive to the plant parameter changes. The control remains effective in the presence of generation rate constraints     

Improved fuzzy logic controller for SVC in power system damping using global signals

Static Var Compensator (SVC) is a shunt-type FACTS device, which is used in power systems primarily for the purpose of voltage and reactive power control. In this paper, an improved fuzzy logic-based supplementary controller for SVC is developed for damping the rotor angle oscillations and to improve the stability of the power system. The generator speed and the electrical power are chosen as global input signals for the proposed fuzzy logic controller (FLC). The effectiveness and feasibility of the proposed control is demonstrated with single-machine infinite bus (SMIB) system, three-machine nine-bus WSCC system and New England 10-machine system, which shows the improvement over the use of a fixed parameter controller and existing FLC.     

电力系统动态过程在线监测装置的研制与应用

阐述了一种在线监测电力系统动态过程装置的研制与应用。该装置硬件系统设计采用多通道的数据采集卡,充分提高了装置抗干扰能力和数据采集能力。软件系统设计中,采用Linux操作系统,增强了装置的可靠性和强大的功能性;并采用Web/Brower方式,使装置充分具有计算机网络的功能。实践证明,该装置运行稳定可靠,通过分析采集数据,为分析电力系统动态过程中各种现象提供了大量有用的波形和数据。     

交直流混联系统非线性自适应广域附加控制器的设计

为了提高交直流混联系统的暂态稳定性,设计了基于高压直流输电(High Voltage Direct Current, HVDC)大信号调制方式的非线性自适应广域附加控制器(Nonlinear Adaptive Wide-area Supplementary Controller, NAWSC)。该控制器利用扰动观测器估计和补偿实际系统中的非线性动态,无需精确模型,解决了模型不确定时稳定控制措施不易设计的难题。同时,该控制器通过整合广域功角信息得到的系统等值功角进行输出反馈,直接实现暂态稳定控制。在四机两区域交直流混联系统和10机39节点交直流混联系统中进行仿真。结果表明：在不同运行工况下,NAWSC相对于比例积分型广域附加控制器具有更好适应性;在参数不确定下,NAWSC相对于基于精确模型的反馈线性化广域附加控制器具有更好的控制鲁棒性。所设计NAWSC可以提高HVDC暂态调节能力。     

一种实用的电力系统在线动态经济调度模型

电力系统中的动态经济调度问题是时间上和空间上相关联的一个复杂的最优决策问题。对于一个实际运行的电力系统,如果研究周期内没有整体资源的限制,在某时刻的决策状态是否整体最优仅仅取决于未来有限的时期,此决策问题在空间上和时间上的关联强弱与这个时期长短(称为前瞻时间)关系密切。研究某时刻决策状态是否整体最优与前瞻时间的关系是核心。基于这一思想,研究前瞻时间变化对动态优化调度结果的影响,确定从可行解到最优解的前瞻时间变化范围,达到在线动态经济调度。     

Effects of various power system stabilizers on improving power system dynamic performance

To ensure the small-signal stability of a power system, power system stabilizers (PSSs) are extensively applied for damping low frequency power oscillations through modulating the excitation supplied to synchronous machines, and increasing interest has been focused on developing different PSS schemes to tackle the threat of damping oscillations to power system stability. This paper examines four different PSS models and investigates their performances on damping power system dynamics using both small-signal eigenvalue analysis and large-signal dynamic simulations. The four kinds of PSSs examined include the Conventional PSS (CPSS), Single Neuron based PSS (SNPSS), Adaptive PSS (APSS) and Multi-band PSS (MBPSS). A steep descent parameter optimization algorithm is employed to seek the optimal PSS design parameters. To evaluate the effects of these PSSs on improving power system dynamic behaviors, case studies are carried out on an 8-unit 24-bus power system through both small-signal eigenvalue analysis and large-signal time-domain simulations.     

Development of self-commutated SVC for power system

A 50-MVA self-commutated Static Var Compernsator (SVC) using the worlds's largest GTO thyristors rated 6 kV-2500 A has been developed for voltage control of electric power systems. The rated dc voltage is 16.8 kV which is four times higher than the highest one manufactured so far. To achieve the high dc voltage, eight GTO thyristors are connected in series. Voltage unbalance between GTOs during switching transient was investigated. A new overcurrent limiting method is proposed, since conventional fuse protection cannot be applied due to such high voltage. Newly developed technologies for this large and high-voltage self-commutated SVC are described. Although simple star-delta connection transformers are used, harmonics generated from SVC are almost equivalent to the 24-pulse converter by shifting the pulse timing appropriately. The PWM control based on 150 Hz is applied and the SVC is designed to continue operation during system faults. The performance of the controller is tested successfully by a simulator, and typical rest results are introduced.     

Hybrid simulation of power systems with SVC dynamic phasor model

A novel hybrid method for simulation of power systems equipped with static var compensators (SVC) is suggested in this paper, where dynamic phasor theory is applied for SVC, and traditional electromechanical transient models are used for ac subsystem. A detailed single-phase dynamic phasor-based SVC model is derived first, and an interface algorithm between the SVC dynamic phasor model and the ac subsystem is proposed next. Test results on the 9-bus and the New England 39-bus test power systems show clearly that the single-phase SVC dynamic phasor model has very good accuracy as compared with its electromagnetic transient model. The proposed hybrid-model simulation method provides a new approach for dynamic simulation of large-scale power systems including SVCs.     

SVC对电力系统频率稳定性影响的仿真分析

用Matlab软件建立电力系统仿真模型,负荷模型包括异步电动机模型和恒阻抗静态模型,静止无功补偿器(SVC)采用一阶线性化实用模型,对系统遭受双回线永久断一回线和系统负荷突然剧增这2种典型大干扰后SVC动作对系统频率造成的影响进行仿真和分析,包括SVC出力大小、动作时间及控制策略的影响。针对断一回线故障,当负荷端电动机比重较小时,SVC可使频率稳定在额定值。对系统在不同调频能力下负荷剧增时所做的频率变化仿真表明,SVC对系统的频率稳定性产生负面影响,SVC无功出力越大,则频率质量越差,当系统调频能力较弱而SVC无功出力很大时,会加速系统的频率崩溃。因此,在SVC的控制系统中应引入频率反馈,当监测频率低于某一定值时,应减少SVC出力至合理值。     

静止无功补偿器对电力系统性能改善的综述

随着电力电子技术、微处理技术和控制技术的发展,柔性交流输电系统FACTS(Flexible AC Transmission System)的出现,为电力系统急待解决问题提供了新的手段或策略。静止无功补偿器(SVC)作为FACTS家族的成员之一,对电力系统性能的改善也已取得了可喜的成绩。因此,从静止无功补偿器提高稳态输送容量、提高暂态稳定性、增强系统阻尼抑制低频振荡、缓解次同步谐振、预防电压不稳定或控制电压的波动、改善直流输电系统的性能等六个方面进行综述。     

Advanced SVC control for damping power system oscillations

A new SVC (static VAR compensation) control for damping of power system oscillations has been developed. To increase system damping an SVC uses a phase angle signal estimated from the measurement of voltage and power at the SVC location. By means of an optimization and identification procedure, optimized design of the damping control with various control concepts can be determined, taking into account nonlinear power systems. As a result of this method it is possible to increase power system damping considerably, in particular in critical situations close to the stability limit, using only locally measured state variables at the SVC, thus leading to an increase in the transmission capability of the power system     

静止无功补偿器对电力系统性能改善的综述

随着电力电子技术、微处理技术和控制技术的发展,柔性交流输电系统FACTS(Flexible AC Transmission System)的出现,为电力系统急待解决问题提供了新的手段或策略.静止无功补偿器(SVC)作为FACTS家族的成员之一,对电力系统性能的改善也已取得了可喜的成绩.因此,从静止无功补偿器提高稳态输送容量、提高暂态稳定性、增强系统阻尼抑制低频振荡、缓解次同步谐振、预防电压不稳定或控制电压的波动、改善直流输电系统的性能等六个方面进行综述.     

考虑SVC影响的电力系统多目标交易计划

提出一种基于最优潮流、计及SVC影响,同时考虑经济效益和环境效益的电力系统多目标交易计划模型.首先对各单目标确定性模型求解,得到目标函数值,其次对目标值进行一定程度的伸缩,并定义目标隶属度函数,将确定性问题模糊化.接着采用最大满意度法将多目标问题转化为单目标问题,然后采用非线性规划方法求解,得到新的潮流结果.仿真结果验证了算法的有效性.     

Design of a robust variable structure controller for improving power system dynamic stability

This paper proposes a nonlinear robust controller for improving power system dynamic stability. The design procedure of the controller which uses a nonlinear transformation technique and the variable structure control (VSC) theory is discussed. A method of eliminating the chattering encountered in variable structure controllers is also presented. Performance of the proposed controller in a simple power system, a single machine connected to infinite bus, is investigated using computer simulations. Robust performance of the controller is verified using a number of studies.     

一种新型电力系统稳定控制装置

提出了一种新型FACTS装置--多功能柔性功率调节器(FPC),它将飞轮储能技术和传统的同步调相技术有机地结合在一起,同时采用交流励磁和矢量控制等先进技术进行控制.这种装置具有储能、发电、调相等多种功能,将其用于电力系统的稳定性控制,可实现动态有功功率和无功功率同时双向大范围的快速调节,具有增强电力系统稳定性的能力.详细论述了柔性功率调节器的工作原理,建立了装置的稳态等值电路模型,分析了装置在不同运行方式下的功率传递关系.同时,还介绍了FPC的一个主要组成部分--基于SPWM的双VSC变频控制器以及三相SVC的矢量控制原理.用数字仿真的方法研究了FPC与电网进行四象限功率交换的特性.最后,用一个单机无穷大系统,通过仿真分析,验证了FPC所具有的巨大的稳定电力系统的能力.