The study of optimizing power system performation by using optimal FACTS devices :Doctor of philosophy - Major: Electrical engineering

学校代号 10532 学 号 LB2011001

分 类 号 密 级 公 开

博士学位论文

采用柔性交流输电设备（FACTS）最优

配置优化电力系统性能的研究

(英文版)

学位申请人姓名 DUONG THANH LONG

导师姓名及职称 姚建刚 教授

培 养 单 位 电气与信息工程学院

学 科 专 业 电气工程

研 究 方 向 电力系统和电力市场

论 文 提 交 日 期 2014 年 4 月

学校代号：10532

学 号：LB2011001

密 级：

湖南大学博士学位论文

采用柔性交流输电设备（FACTS）最

优配置优化电力系统性能的研究

学位申请人姓名： DUONG THANH LONG

导师姓名及职称： 姚建刚 教授

培养单 位： 电气与信息工程学院

专业名 称： 电气工程

论 文 提 交 日 期： 2014 年 4 月

论 文 答 辩 日 期： 2014 年 4 月 9 日

答辩委员会主席： 曹一家 教授

The Study of Optimizing Power System Performance by Using Optimal

FACTS Devices

By

DUONG THANH LONG

B.E. (University of Technical Education Hochiminh City, Vietnam) 2003

M.E. (University of Technical Education Hochiminh City, Vietnam) 2005

A dissertation submitted in partial satisfaction of the

Requirements for the degree of

Doctor of Engineering

In

Electrical Engineering

In the

Graduate School

Of

Hunan University

Supervisor

Professor YAO JIAN GANG

April 2014

I

位论文原创性声明和学位论文版权使用授权书

湖 南 大 学

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Doctoral Dissertation

II

摘要

本文研究基于这样一个事实，就是由于输电系统的扩展无法与日益增长的

输电服务相协调而造成了目前电力系统的过载严重问题日益凸显。之所以造成

这样的问题是由于环境和经济的因素导致建造新的传输线路是困难的。因此，

通过研究提高当前电力系统的输电能力来满足日益增长的电力需求以确保电力

系统的安全运行是一个亟待解决的问题。

潮流控制设备比如柔性交流输电设备(FACTS)对时下电网新的运行方式挑

战提供了解决方案。特别的，晶闸管控制的串联补偿设备（TCSC）是一种被选

来研究的很有效的FACTS。TCSC通过改变输电线路参数来控制网络潮流。TCSC对

网络的影响可以看成是在相关的输电线中嵌入一个可控的电抗。串联电容补偿

通过抵消感抗部分减少传输线的等效串联阻抗。因而提高了功率传输能力。这

样在不用重新安排发电计划和改变网络拓扑结构的情况下，通过控制潮流可极

大提高系统的性能。而且这样也不会超越导线的热容量的限制同时提高了电力

系统的稳定边界。为了通过采用这些设备而获得最大的效益，需要一个有效的

控制方式。在研究调查柔性交流输电设备 (FACTS) 的大量应用情况后，可知针

对不同目的的有效控制依赖于控制装置的安装位置。因此，运行人员面临这样

一个问题就是在什么位置安装FACTS设备能达到期望的目标。目前已有大量研究

在于通过FACTS设备的最优配置来改善现有电力系统性能，但对如何缩减最优安

装位置的搜索范围显得无能为力。基于此，本文重点研究了如何使用和选择柔

性交流输电(TCSC)设备的最优安装位置来优化电力系统性能。提出了一种用于

确定晶闸管控制的串联补偿设备（TCSC）最优位置的最小切割算法（Min-cut

algorithm）。一旦TCSC设备的安装位置确定了，为其寻求最佳参数的最优化问

题就可以得到相应的解决。该方法可以寻找出系统中最需要安装设备的配置

点，从而帮助调度人员以一种更加安全和高效的方式进行调度。采用本文方法

大大减少了待选位置，从而大大减少了为提高电力系统性能而需要运行人员实

际调查才能确定TCSC配置点的工作量。

The Study of Optimizing Power System Performance by Using Optimal Location of FACTS Devices

III

本文的研究重点是通过TCSC设备的最优配置点的选择及其最优参数的确定

来优化电力系统性能。本文尤其能够通过解决电力系统阻塞来提高电力系统的

传输能力和考虑了电力系统静态稳定与暂态稳定约束下的电力系统性能。本文

所提到的电力系统性能通过对解决安全约束最优潮流问题，全面提高电力系统

传输能力，阻塞管理和最大负荷承载能力等四个问题来进行衡量评价。仿真结

果表明在TCSC设备优化配置后，大大提高了电力系统性能

关键词：柔性交流输电（FACTS），可控串联补偿器（TCSC），最小切割算法（Min￾cut algorithm），最优化，电力系统，电力市场

Doctoral Dissertation

IV

Abstract

This research stems from the fact that today’s power systems are heavy stressed due to

expansion in the transmission network have not kept pace with the increasing demand for

transmission services because building of new lines is difficult for environmental as well as

political reasons. Hence, enhancement the transfer capability of existing power networks to

satisfy the increased power demand and ensure its secure operation has become an important

issue for the Independent System Operator in the new electricity markets.

Power Flow Control devices such as Flexible AC Transmission Systems (FACTS)

provide the technical solutions to address the new operating challenges being presented today.

Especially, Thyristor-Controlled Series Compensator (TCSC), which is one of the most

effective FACTS devices, can control the power flows in the network by changing

transmission lines parameters. The effect of TCSC on the network can be seen as a

controllable reactance inserted in the related transmission line. Series capacitive compensation

works by reducing the effective series impedance of the transmission line by canceling part of

the inductive reactance. Hence the power transferred is increased. In this way, the system

performance can be considerably improved by controlling the power flows without generation

rescheduling or topological changes. Furthermore, the thermal limits are not violated and the

stability margin is increased. In order to obtain benefits from these devices, an appropriate

control is necessary. Studies that investigate the deployment of FACTS are indicated that the

effectiveness of the controls for different purposes mainly depends on the location of control

device. Therefore, Operators are facing the problem of where FACTS should be installed in

order to achieve require goal?. Many studies have been proposed for improving existing

power networks via optimal location of FACTS devices, these however studies are not able to

limit search space. From the viewpoint, this thesis focuses on look at the problem of how to

place and use the TCSC devices optimally to enhance of power system performance. A Min￾Cut algorithm is proposed in this thesis to determine proper location of TCSC. Once the

locations are determined, an optimization problem of finding the best settings for the installed

TCSC is formulated and solved. The proposed method can identify the weakest location of the

system and therefore helps the System Operators to operate the system in a more secure and

sufficient way. With this method search space and the number of branches which need to be

investigated to determine the position of TCSC for optimizing of power system performance

will be significantly decreased.

The focus of this work is to optimize power system performance by the optimal

The Study of Optimizing Power System Performance by Using Optimal Location of FACTS Devices

V

placement of TCSC devices and their settings. Particularly, it is intended to improve the

power system transfer capability by resolving congestions, and the performance of the power

system considering steady state operating condition as well as the system subjected to small

disturbances. The power system performance in this thesis is evaluated via solution problem

concern in Security Constrained Optimal Power Flow, Enhancing Total Transfer Capability of

Power System, Transmission Congestion Management and Maximum Loadability. Simulation

results throughout this research show a significant improvement of the power system

performance after the TCSC devices is optimized.

Keywords: FACTS, TCSC, Min Cut Algorithm, Optimization, Power System, Electricity

Market.

Doctoral Dissertation

VI

Table of Contents

位论文原创性声明和学位论文版权使用授权书.....................................................................I

摘要............................................................................................................................................II

Abstract .....................................................................................................................................IV

Table of Contents......................................................................................................................VI

List of figures.............................................................................................................................X

List of tables............................................................................................................................ XII

List of symbols and acronyms.................................................................................................XV

CHAPTER 1 INTRODUCTION .......................................................................................1

1.1 Problem statement ..........................................................................................................1

1.2 Aims of the research .......................................................................................................2

1.3 Contributions..................................................................................................................2

1.4 Literature review............................................................................................................3

1.4.1 Current methods for solving the FACTS allocation problem.................................3

1.4.1.1 Classical optimization methods ....................................................................3

1.4.1.2 Methods based on technical criteria..............................................................4

- Sensitivity analysis ......................................................................................4

- Modal analysis..............................................................................................5

1.4.1.3 Evolutionary computation techniques.......................................................... 6

1.5 Contents of the thesis ...................................................................................................7

CHAPTER 2 TRANSMISSION CONGESTION, FACTS DEVICES AND MIN

CUT ALGORITHM..................................................................................................................9

2.1 Introduction ....................................................................................................................9

2.2 Transmission Congestion ............................................................................................10

2.3 An Overview of FACTS...............................................................................................11

2.4 Thyristor-Controlled Series Compensator (TCSC)......................................................13

2.4.1 Definition..............................................................................................................13

2.4.2 Structure and operation.........................................................................................13

2.4.3 Static modeling of TCSC......................................................................................15

2.5 Optimal Power Flow in Electricity Market ..................................................................16

2.6 Min – Cut Algorithm....................................................................................................17

2.6.1 Max-Flow/Min-Cut-Theorem...............................................................................17

2.6.2 Modeling power network using Min cut algorithm..............................................18

The Study of Optimizing Power System Performance by Using Optimal Location of FACTS Devices

VII

CHAPTER 3 SECURED OPTIMAL POWER FLOW UNDER NORMAL AND

NETWORK CONTIGENCIES VIA OPTIMAL LOCATION OF TCSC........................23

3.1 Introduction ..................................................................................................................23

3.2 Problem formulation.....................................................................................................25

3.2.1 Objective function ................................................................................................26

3.3 Case study and discussions...........................................................................................26

3.3.1 Six bus system ......................................................................................................27

3.3.1.1 OPF under normal operation .....................................................................27

3.3.1.2 OPF under network contingencies ............................................................30

3.3.2 IEEE 14-bus test system.......................................................................................32

3.3.2.1 OPF under normal operation .....................................................................32

3.3.2.2 OPF under network contingencies ...........................................................33

3.3.3 IEEE 30-bus test system.......................................................................................35

3.3.4 IEEE 118-bus test system.....................................................................................40

3.4 Conclusion....................................................................................................................41

CHAPTER 4 ENHANCING TOTAL TRANSFER CAPABILITY VIA OPTIMAL

LOCATION OF TCSC...........................................................................................................42

4.1 Introduction ..................................................................................................................42

4.2 Problem formulations using RPF with and without TCSC ..........................................43

4.3 Case study and discussions...........................................................................................45

4.3.1 IEEE 14-bus test system.......................................................................................45

4.3.2 IEEE 30-bus test system.......................................................................................46

4.4 Conclusion....................................................................................................................48

CHAPTER 5 OPTIMAL LOCATION OF TCSC FOR TRANSMISSION

CONGESTION MANAGEMENT.........................................................................................49

5.1 Introduction ..................................................................................................................49

5.2 Problem formulation.....................................................................................................51

5.2.1 Objective function ................................................................................................51

5.2.2 TCSC cost function ..............................................................................................51

5.2.3 Benefit index.........................................................................................................52

5.3 Case study and discussions...........................................................................................53

5.3.1 The 5-bus system....................................................................................................53

5.3.2 IEEE 14-bus test system........................................................................................55

5.3.3 IEEE 30-bus test system........................................................................................57

5.4 Conclusion....................................................................................................................58

Doctoral Dissertation

VIII

CHAPTER 6 APPLICATION OF MIN CUT ALGORITHM FOR OPTIMAL

LOCATION OF TCSC DEVICES CONSIDERING SYSTEM LOADABILITY AND

COST OF INSTALLATION..................................................................................................60

6.1 Introduction ..................................................................................................................60

6.2 Problem formulation.....................................................................................................62

6.3 Optimal setting of TCSC..............................................................................................63

6.4 Cost function.................................................................................................................65

6.5 Case study and discussions...........................................................................................65

6.5.1 IEEE-6 bus system................................................................................................66

6.5.2 IEEE-30 bus system..............................................................................................68

6.5.3 IEEE-118 bus system............................................................................................70

6.6 Conclusion....................................................................................................................71

CHAPTER 7 IMPROVING THE TRANSIENT STABILITY - CONSTRAINED

OPTIMAL POWER FLOW WITH TCSC ..........................................................................72

7.1 Introduction ..................................................................................................................72

7.2 TSCOPF Problem formulation .....................................................................................73

7.2.1 Objective function ................................................................................................74

7.2.2 Formulation of TSCOPF ......................................................................................76

7.3 Case study and discussions...........................................................................................76

7.3.1 WECC Nine-Bus, Three-Machine System.......................................................... 76

7.3.2 IEEE 30-bus system..............................................................................................79

7.4 Conclusion....................................................................................................................82

CHAPTER 8 SUMMARY, CONCLUSION AND FUTURE WORK ..........................83

8.1 Thesis Summary ...........................................................................................................83

8.2 Conclusion....................................................................................................................84

8.3 Future Work ..................................................................................................................85

References.................................................................................................................................86

Appendix A: Chapter 3 ......................................................................................................97

Appendix B: Chapter 5.....................................................................................................102

Appendix C: List of publications ....................................................................................103

Appendix D: 中文摘要....................................................................................................104

Acknowledgment ....................................................................................................................113

The Study of Optimizing Power System Performance by Using Optimal Location of FACTS Devices

IX

List of figures

Figure 2.1: Basic structure of the TCSC..................................................................................13

Figure 2.2: Operating range of the TCSC................................................................................14

Figure 2.3: Operation modes of the TCSC...............................................................................14

Figure 2.4: Practical structure of a TCSC................................................................................15

Figure 2.5: Model of transmission line with TCSC.................................................................15

Figure 2.6: Modeling of a network with some cuts. ................................................................18

Figure 2.7: Example power system with generators of 8 at 1, 24 at 2 and 12 at 3 and loads of

20 and 24 ...................................................................................................................................19

Figure 2.8: Power network shown as a directed flow graph with virtual nodes s and t. Edges

are labeled with (flow/capacity)................................................................................................20

Figure 2.9: The units of flow along s-2-5-t..............................................................................20

Figure 2.10: The units of flow along s-3-5-t............................................................................20

Figure 2.11: The units of flow along s-2-4-t............................................................................20

Figure 2.12: The units of flow along s-1-4-t............................................................................21

Figure 2.13: Some possible cuts...............................................................................................21

Figure 2.14: Flow chart of min cut algorithm..........................................................................21

Figure 3.1: Flow chart for secured optimal power flow under normal and network

contingencies.............................................................................................................................28

Figure 4.1: IEEE 14-bus system...............................................................................................45

Figure 4.2: Flow chart for power transfer capability with TCSC and without TCSC .............47

Figure 5.1: Flow chart for determination optimal location of TCSC in congestion

management ..............................................................................................................................52

Figure 6.1: Model of transmission line with TCSC.................................................................62

Figure 6.2: The 4-bus system...................................................................................................63

Figure 6.3: Flow chart for achieving MSL and optimal installation cost of TCSC.................66