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.     

Effects of STATCOM,TCSC, SSSC and UPFC on static voltage stability

The purpose of this paper is to study the effects of four FACTS controllers: STATCOM, TCSC, SSSC and UPFC on static voltage stability in power systems. Continuation power flow is used to evaluate the effects of these devices on system loadability. Applying saddle node bifurcation theory with the use of PSAT, effects of these devices controllers on maximum loading point are determined. Static voltage stability margin enhancement using STATCOM, TCSC, SSSC and UPFC is compared in the modified IEEE 14-bus test system.     

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.     

Novel reactive power controllers for the STATCOM and SSSC

The paper investigates the dynamic operation of both static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC) based on a new model comprising full 48-pulse GTO voltage source converter for combined reactive power compensation and voltage stabilization of the electric grid network. These key FACTS devices are power electronic GTO converters connected in parallel or series with the power system grid and are controlled by novel decoupled controllers. The complete digital simulation of the STATCOM and SSSC within the power system is performed in the MATLAB/Simulink environment using the power system blockset (PSB). The STATCOM scheme and the electric grid network are modeled by specific electric blocks from the power system blockset while the control system is modeled using Simulink. Two novel controllers for the STATCOM and SSSC are presented in this paper based on a decoupled current control strategy to ensure stable operation of the STATCOM under various load excursions. A novel control scheme for the static synchronous series compensator (SSSC) is also implemented to provide a full controllable series compensating (buck/boost) injected voltage over a specified capacitive and inductive range, independently of the magnitude of the transmission line current. The series reactive compensation scheme with an external dc power supply can also compensate for any voltage drops across resistive component of the transmission line impedance. The novel decoupled controller uses a phase locked loop (PLL) with a novel reduced inherent time delay to improve the transient performance of the SSSC. The performance of both STATCOM and SSSC schemes connected to the 230 kV grid are evaluated. The proposed novel control schemes for the STATCOM and SSSC are fully validated by digital simulation.     

Dynamic model for power systems with multiple FACTS controllers

Computer simulation and analysis of power systems are necessary for both planning and operation. This requires an appropriate mathematical model of the system that includes many inter-related linear/nonlinear differential and algebraic equations. Such mathematical model is also needed for the design of globally coordinated controllers to improve power system dynamic performance and stability. This paper presents a procedure for finding comprehensive dynamic models of power systems fitted with shunt and/or series connected FACTS controllers such as STATCOM, SSSC, and UPFC. In this procedure, individual components of a power system are modeled using appropriate frame of references. Then all related equations are transformed to a common network frame of reference and tied to each other through the Y-matrix of the transmission network. The procedure is tested on the Western System Coordinating Council (WSCC) test system including FACTS controllers by performing computer simulations of the system for three-phase short circuit faults. MATLAB/Simulink software package is used for the simulations.     

STATCOM versus SSSC for power system stabilization

Flexible alternating current transmission systems (FACTS ) are gaining more attention in power utilities because of their advantages of controllability, reliability, and operation over a wide range. Static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC ) are prominent FACTS topologies; they have the ability to instantaneously regulate active/reactive powers and stabilize the power system following severe disturbances. In this paper, STATCOM and SSSC are compared with regard to their damping action on power system oscillations. The comparison is extended to the controller design strategies. Two distinct meta‐heuristic optimization approaches, namely chaos (CO) and simulated annealing (SA), are recommended for the optimal design of the SSSC and STATCOM damping controller. To assess the promising FACTS topology, a single‐machine infinite bus system is subjected to several disturbances while operating at different loading levels. MATLAB/Simulink is used as a platform to investigate the dynamic performance of the system under consideration with STATCOM and SSSC . Simulation results reveal the superiority of SSSC in damping power system oscillations in terms of response speed and stability margin. Moreover, the CO optimization scheme seems to outperform the SA algorithm in terms of computation requirements and global optimal convergence. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Advanced modeling of the multicontrol functional static synchronous series compensator (SSSC) in Newton power flow

The static synchronous series compensator (SSSC) is one of the recently developed flexible AC transmission system (FACTS) controllers. The SSSC coupled with a transformer is connected in series with a transmission line. This paper describes a multicontrol functional model of the SSSC for power flow analysis, which can be used for steady state control of one of the following parameters: (1) the active power flow on the transmission line; (2) the reactive power flow on the transmission line; (3) the voltage at the bus; and (4) the impedance (precisely reactance) of the transmission line. Furthermore, the model can also take into account the voltage and current constraints of the SSSC. The detailed implementation of such a multicontrol functional model in Newton power flow algorithm is presented. A special consideration of the initialization of the variables of the SSSC in power flow analysis is also proposed. Numerical examples on the IEEE 30-bus system, IEEE 118-bus system, and IEEE 300-bus system are used to illustrate the feasibility of the SSSC model and performance of the Newton power flow algorithm.     

统一潮流控制器控制策略的研究与实现

对统一潮流控制器(UPFC)的数学模型、控制策略进行了具体的分析和设计,在两相同步旋转dq坐标系下建立了控制系统动态模型。考虑到有功和无功在dq坐标系下的相互影响,UPFC的串联逆变器采用了三环解耦控制,外环是功率环,中间环为电压环,内环为电流环,由于电流内环的快速响应,使得电流跟踪输入电压,提高系统的稳定性和动态响应性能。文中对UPFC实现的STATCOM和SSSC功能进行了系统的分析,并对其动态特性进行了深入的研究。最后利用实验验证了在UPFC中采用这种控制方式的有效性。     

A reconfigurable FACTS system for university laboratories

To fully understand the dynamic performance of the multiple flexible ac transmission systems (FACTS) devices, a hardware setup is needed to complement software simulation for university research laboratories. This paper presents the schematic and basic controls of a reconfigurable FACTS system that can be used to realize the major voltage-sourced-converter FACTS topologies: the StatCom, the static synchronous series compensator (SSSC), and the unified power-flow controller (UPFC). Furthermore, the state models and control algorithms for the FACTS devices are proposed. The digital signal processor (DSP)-based control system enables new control methods to be rapidly implemented. The comparison of the experimental and simulation results is also provided to verify the proposed controls. The paper culminates in a list of suggested experiments appropriate for an elective/graduate course in electric power systems.     

Wavelet entropy based algorithm for fault detection and classification in FACTS compensated transmission line

Distance protection of transmission lines including advanced flexible AC transmission system (FACTS) devices has been a very challenging task. FACTS devices of interest in this paper are static synchronous series compensators (SSSC) and unified power flow controller (UPFC). In this paper, a new algorithm is proposed to detect and classify the fault and identify the fault position in a transmission line with respect to a FACTS device placed in the midpoint of the transmission line. Discrete wavelet transformation and wavelet entropy calculations are used to analyze during fault current and voltage signals of the compensated transmission line. The proposed algorithm is very simple and accurate in fault detection and classification. A variety of fault cases and simulation results are introduced to show the effectiveness of such algorithm.     

一种可配置的FACTS实验系统的研究

为了能够全面地了解FACTS系统的特性，本文建立了一台可配置的FACTS实验系统。根据不同的要求可以实现STATCOM、SSSC、DVR以及UPFC的功能。通过建立FACTS系统的状态空间模型，结合对不同FACTS系统工作的矢量图分析，设计了相应的控制系统。最后分别对上述四种FACTS系统进行了相应的实验，实验结果表明这种可配置的FACTS实验系统能够较好的实现上述四种FACTS系统的功能，它为研究设计、改进和验证FACTS控制系统提供了一个实验平台。     

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.     

Adaptive algorithm for transmission line protection in the presence of UPFC

The presence of flexible ac transmission system (FACTS) controllers in transmission lines causes mal-operation of distance relays. The series-shunt FACTS devices have larger influence on the performance of the relays compare to the other FACTS controllers. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this paper, a method is provided based on synchrophasors to eliminate the effects of unified power-flow controller (UPFC) and fault resistance on the distance relay. In the presented method, the data of voltage and current signals of buses will be sent to system protection center (SPC). In SPC, an algorithm is provided based on active power calculation in buses which is able to eliminate the effects of both mentioned factors. The main advantage of the proposed method, in addition to the simplicity of the algorithm, is the ability to operate in all types of faults and in high-resistance faults. Furthermore, a technique is presented in this paper to calculate UPFC data. A comparison has been performed between this technique and another method where UPFC data is directly transmitted to SPC by communication channel. In modeling of UPFC, detail model is used based on 48-pulses voltage source converters.     

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STATCOM的电力系统电压稳定特征结构分析

静止同步补偿器STATCOM是柔性交流输电系统FACTS家族中的重要成员,可有效改善系统电压调节特性,提高系统电压稳定裕度.文章基于特征结构分析法,将STATCOM的稳态模型加入潮流方程中,建立计及STATCOM的电压稳定计算模型.该方法以最小模特征值作为系统接近电压不稳定的量度,以电压灵敏度和参与因子为指标,判断全电网中最有可能发生电压不稳定的节点和区域,从而为STATCOM的配置提供依据.对WSCC-3机9节点系统仿真,验证了STATCOM对电压稳定的积极作用.     

Improvement of synchronizing power and damping power by means of SSSC and STATCOM: A comparative study

This paper examines the influence of Static Synchronous Series Compensator (SSSC) and STATic synchronous COMpensator (STATCOM) on the synchronizing power and damping power of a single-machine infinite bus system. The main function of SSSC is to compensate for the voltage drop across the impedance transmission line while the STATCOM provides voltage support at the point of connection at the transmission line. Beside their main function, SSSC and STATCOM can also be used to improve the synchronizing power and damping power, which in turns improve the small signal stability of power systems and thus more power can be transmitted. The SSSC has two modes of operation: (1) constant reactance mode and (2) constant quadrature voltage mode. It was shown that SSSC provides higher synchronizing and damping powers when operated in constant reactance mode than constant quadrature voltage mode. Comparing SSSC with STATCOM, the SSSC, in constant reactance mode, has been found to provide higher synchronizing and damping powers than the STATCOM. However, the STATCOM provides higher synchronizing and damping power than the SSSC when it operates on constant quadrature voltage mode.     

Pole placement by coordinated tuning of Power System Stabilizers and FACTS-POD stabilizers

This work presents the application of the Decentralized Modal Control method for pole placement in multimachine power systems utilizing FACTS (Flexible AC Transmission Systems), STATCOM (Static Synchronous Compensator) and UPFC (Unified Power Flow Controller) devices. For this, these devices are equipped with supplementary damping controllers, denominated POD (Power Oscillation Damping), achieving a coordinated project with local controllers (Power System Stabilizers - PSS). Comparative analysis on the function of damping of the FACTS, STATCOM and UPFC is performed using the New England System that has 10 generators, 39 buses and 46 transmission lines.     

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.     

Investigation of performance of UPFC without DC link capacitor

This paper presents an analysis of the dynamic operation of unified power flow controller without DC link capacitor. In this scheme of UPFC the shunt converter present in the static synchronous compensator is operated as a current source rectifier, which maintains a fixed DC voltage and DC current on the DC link without capacitor. The capacitor in the DC link is replaced by an AC filter on the line side with a very small value to reduce higher order harmonics. The voltage source inverter present in the series compensator is operated with space vector modulation technique. The proposed scheme is fully validated through digital simulation. The simulated results show that the DC link voltage is maintained constant without DC link capacitor; STATCOM provides good voltage regulation and static synchronous series compensator influences power flow over the transmission line. Transient responses of single machine infinite bus power system have also been presented.     

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.