Unified Power Flow Controller Technology and Application

By Jijun Yin

Unified Power Flow Controller Technology and Application provides comprehensive coverage on UPFC technology, providing a range of topics, including design principle, control and protection, and insulation coordination. It summarizes all the most up-to-date research and practical achievements that are related to UPFC and MMC technology, including test techniques for main components, closed-loop test techniques for control and protection systems, and onsite techniques for implementing UPFC projects. The book is an essential reference book for both academics and engineers working in power system protection control, power system planning engineers, and HVDC FACTS related areas.

Readers will not only obtain the detailed information regarding theoretical analysis and practical application of UPFC, but also the control mechanism of advanced MMC technology, both of which are not common topics in previously published books.

• Shows how to use modular multilevel converters (MMC) to implement UPFC that lead to cost-effective and reliable systems
• Draws from the most up-to-date research and practical applications
• Teaches electromechanical/electromagnetic transient simulation techniques and real-time closed-loop simulation test techniques of the MMC based UPFC

• Language: English
• Publisher: Academic Press
• Release date: Jun 16, 2017
• ISBN: 9780128134863

Jijun Yin

Yin Jijun is currently General Manager of Jiangsu Electric Power Company. He used to serve as Director of production technology department and General Manager Assistant of Shandong Electric Power Company, Vice General Manager of Henan Electric Power Company, Deputy Director of public relations department and Director of outreach department of State Grid, and General Manager of State Grid Jibei Electric Power Company. He is well known as a technical leader and a researcher who has witnessed China’s rapid development in power systems interconnection during recent years. As a leader, he was in full charge of the Nanjing west power grid UPFC project, which was a national technology demonstration project that implemented the first MMC based UPFC in the world.

Book preview

Unified Power Flow Controller Technology and Application

YIN Jijun

State Grid Jiangsu Electric Power Company, Nanjing, China

CHEN Gang

State Grid Jiangsu Electric Power Company, Nanjing, China

XU Haiqing

State Grid Jiangsu Electric Power Research Institute, Nanjing, China

LI Qun

State Grid Jiangsu Electric Power Research Institute, Nanjing, China

LIU Jiankun

State Grid Jiangsu Electric Power Research Institute, Nanjing, China

LI Peng

State Grid Jiangsu Electric Power Research Institute, Nanjing, China

Table of Contents

Cover image

Title page

Copyright

Writing Group

Chapter 1. Summary

Abstract

1.1 The Development Process of FACTS Technology

1.2 Present Research Situation of the UPFC

References

Chapter 2. Principles and functions of UPFC

Abstract

2.1 Technical Principle of the UPFC

2.2 UPFC Control Function Analysis

2.3 UPFC Optimization Function in Power Network

References

Chapter 3. The key devices of unified power flow controller

Abstract

3.1 Converter

3.2 Bridge Arm Reactor

3.3 Starting Resistance at Parallel Side

3.4 Series Transformer

3.5 Shunt Transformer

3.6 DC Field Equipment

3.7 Thyristor Bypass Switch

3.8 Converter Valve Cooling System

References

Further Reading

Chapter 4. UPFC control and protection system

Abstract

4.1 Control Strategy of the UPFC

4.2 UPFC Protection Strategy

4.3 Control Protection System

4.4 Control Strategy of UPFC to Improve System Stability

References

Further Reading

Chapter 5. Modeling and simulation techniques of UPFC

Abstract

5.1 Steady-State Modeling Method of UPFC

5.2 Electromechanical Transient Modeling Method of UPFC

5.3 Modeling and Simulation Techniques of the UPFC

5.4 UPFC Hybrid Simulation Technology

References

Further Reading

Chapter 6. Overvoltage and insulation coordination of UPFC

Abstract

6.1 Overvoltage of UPFC

6.2 Arrester Configuration and Insulation Coordination of the UPFC

References

Chapter 7. Test technology for UPFC

Abstract

7.1 Test Techniques for the Main Equipment

7.2 Closed-Loop Test Techniques for Control and Protection Systems of Unified Power Flow Controller

7.3 Onsite Debugging Test Techniques in the UPFC Project

Chapter 8. Foreign UPFC projects

Abstract

8.1 The AEP UPFC Project

8.2 NYPA CSC Project

8.3 Kangjin UPFC Project

References

Chapter 9. The domestic application of UPFC

Abstract

9.1 Overview of Domestic Applications

9.2 The 220 kV UPFC Project in the Western Nanjing Power Grid

9.3 500 kV UPFC Demonstration Project in Suzhou Southern Power Grid

9.4 Summary of the Domestic UPFC Project

Appendix 1. RTDS-based small time step simulation model

Index

Copyright

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Writing Group

YIN Jijun, State Grid Jiangsu Electric Power Company

YIN Jijun is currently the General Manager of Jiangsu Electric Power Company. He served as Director of the production technology department, Deputy Director of the public relations department, Director of the outreach department of State Grid, and General Manager of State Grid Jibei Electric Power Company. He is a well-known technical leader and researcher, who was in charge of the Nanjing western power grid UPFC project, a national technology demonstration project that implemented the first MMC based UPFC in the world.

CHEN Gang, State Grid Jiangsu Electric Power Company

CHEN gang is currently Chief Engineer of Jiangsu Electric Power Company. He is well known as a technical leader and a researcher who has witnessed China’s rapid development of power systems during recent years. He participated in grid-integrating projects of large power plants and leaded several ultra-high voltage AC/DC inter-area connecting projects.

XU Haiqing, State Grid Jiangsu Electric Power Research Institute

XU Haiqing is currently the Dean of State Grid Jiangsu Electric Power Research Institute. He is a senior engineer who is specialized in power system information and communication technology, and power information management. As a member of the technical and management personnel, he has provided strong support for the production and operation of Jiangsu Power Grid.

LI Qun, State Grid Jiangsu Electric Power Research Institute

LI Qun received his Ph.D. from Southeast University, Nanjing, China, in 1998. He is currently the Chief Engineer of State Grid Jiangsu Electric Power Research Institute. He is the State-Council Allowance Obtained Expert and the Leading Talent of State Grid in the field of power system operation. His research interests include power system analysis, FACTS technology, and new-energy generation technology.

LIU Jiankun, State Grid Jiangsu Electric Power Research Institute

LIU Jiankun is currently the deputy director of Grid Technology Center in State Grid Jiangsu Electric Power Research Institute. For years, he was to committed power system analysis, flexible AC transmission, and extra-high voltage transmission areas.

LI Peng, State Grid Jiangsu Electric Power Research Institute

LI Peng is currently a senior electrical engineer of Jiangsu Electric Power Research Institute in China. He received his Ph.D. in electrical engineering from Xi’an Jiaotong University. He is a well-known technical researcher and implementer who has been involved as a key member of the technology research on UPFC and implementation of the Nanjing western power grid UPFC project, a national technology demonstration project that featured the world’s first MMC-based UPFC.

PAN Lei, NARI-Relays Electric Co. Ltd

PAN Lei received his B.Sc. in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 2007, and his M.Sc. in electrical engineering from State Grid Electric Power Research Institute in 2010, China. He is currently a R&D engineer with NR Electric in China. His expertise includes HVDC transmission and UPFC control.

QI Wanchun, State Grid Jiangsu Economic Research Institute

QI Wanchun is currently the director of planning and evaluation department in State Grid Jiangsu Economic Research Institute. He is a senior engineer and his research interests include power system planning and reliability analysis, power economic evaluation and project management.

CHEN Jing, State Grid Jiangsu Electric Power Research Institute

CHEN Jing was born in 1988. She received her Master’s degree in electrical engineering from Wuhan University, Wuhan, China, in 2013. She is currently an engineer in State Grid Jiangsu Electric Power Research Institute. Her research interests include power system analysis and FACTS technology.

JI Tuo, State Grid Jiangsu Electric Power Research Institute

JI Tuo received his Ph.D. from Washington State University in US in 2014. He is a Senior Engineer of Jiangsu Electric Power Research Institute and is currently serving as Assistant Director of Strategy, Innovation and Process Department of CPFL Energia, a leading distribution company in the power sector of Brazil. He is experienced in power system analyzing and planning, especially the power system stability and operational control of hybrid transmission systems.

XIE Tianxi, State Grid Jiangsu Electric Power Research Institute

XIE Tianxi was born in 1983. He received his Ph.D. in electrical engineering from Xi’an Jiaotong University, Xi’an, China, in 2012. He is presently working with the State Grid Jiangsu Electric Power Research Institute. His current research interests include structural optimization of power equipment, electric field simulation, electromagnetic transient simulation, and power system overvoltage analysis.

ZHANG Ningyu, State Grid Jiangsu Electric Power Research Institute

ZHANG Ningyu was born in 1985. He received his B.Sc. from China University of Mining and Technology in 2006 and his Ph.D. from Southeast University, Nanjing, China, in 2013, all in electrical engineering. He is currently a senior engineer in State Grid Jiangsu Electric Power Research Institute. His research interests include power system optimization and economics, and FACTS.

SHI Mingming, State Grid Jiangsu Electric Power Research Institute

SHI Mingming was born in 1986. He received his B.Sc. and Ph.D. degrees in electrical engineering from the Nanjing University of Aeronautics and Astronautics, Nanjing, China, in 2007 and 2012 respectively. He is currently working at the State Grid Jiangsu Electric Power Research Institute. His main research interests are in power quality analysis, and power electronics control.

YANG Yi, State Grid Jiangsu Electric Power Research Institute

YANG Yi received his M.Sc. in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 2007, and his Ph.D. from Queen’s University Belfast, Northern Ireland, U.K., in 2013. Currently, he is a Senior Engineer in State Grid Jiangsu Electric Power Research Institute. His research interests include FACTS, relay protection, IEC 61850-based smart substation, and smart grid cybersecurity.

ZHU Xinyao, State Grid Jiangsu Electric Power Research Institute

ZHU Xinyao received his Ph.D. in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 2014. He is currently an engineer at State Grid Jiangsu Electric Power Research Institute. His major research interests include power system analysis and digital simulation, power system subsynchronous oscillation, and HVDC&FACTS control.

KONG Xiangping, State Grid Jiangsu Electric Power Research Institute

KONG Xiangping received his Ph.D. at the School of Electrical and Electronic Engineering from Huazhong University of Science and Technology, Wuhan, China, in 2014. Currently, he is an engineer in State Grid Jiangsu Electric Power Research Institute. His research interest is protective relaying.

Chapter 1

Summary

Abstract

Flexible power transmission makes power systems safer and more stable, hence Flexible Alternative Current Transmission Systems (FACTS) has been popular for over 25 years. It also allows powering of flow control. Because FACTS devices can be incorporated gradually and tsilired to a specific area, the take-up has been rapid. High voltage transmission system—wafer revolution.

Keywords

FACTS; transmission system; flexible power transmission

1.1 The Development Process of FACTS Technology

Since Flexible Alternative Current Transmission Systems (FACTS) was brought up by Hingorani [1] as an overall concept of network control, it has been widely used to improve power system stability, power flow control, power factor correction, and loss reduction. Flexible power transmission means maintaining adequate steady state and transient stability margins during changes in power transmission or operating conditions. Based on a variety of high-speed power electronic devices, FACTS can improve power system operating performance by absorbing or emitting active and reactive power.

1.1.1 The Background of FACTS Technology

The good momentum of the development of FACTS technology’s comes from good background conditions, which may be summarized as two elements, an inevitable trend and the objective needs of the development of power electronics technology.

1.1.1.1 The objective needs of grid operation control

The modern power system has developed into a large-scale AC–DC (Alternating Current–Direct Current) interconnected power grid, while the imbalance of regional power generation and load distribution, as well as the uneven distribution of power transmission, have become more and more severe, making it difficult for power supply capability to be fully utilized. Besides, owing to the restriction of urban planning, the difficulty of line and grid renovation and expansion keeps increasing and with the constraints of complex system structure, heavy operational task, high requirements of power quality, as well as environmental protection, there has been a growing demand for economic and reliable operation of the transmission grid. However, the lack of traditional control measures and the low level of automation are the main factors restraining power transmission, and are the potential risk factors for system crashes [2].

As a new solution, FACTS brings out an unprecedented opportunity to power flow control as well as improving system stability and transmission capacity. And FACTS technology develops in parallel with the existing AC transmission systems, since the requisite devices are gradually added to the existing AC transmission system. These factors have ensured that FACTS devices are widely accepted and are developing rapidly as they are able to improve the power system gradually without major changes by utilizing high power electronic technology and dealing with the grid by case in specific areas.

1.1.1.2 The inevitable development trend of power electronics technology

Historically, each generation of new power electronic devices has brought a revolution in the area of power electronics, and the power electronics for a high-voltage transmission system is called the second wafer revolution after microelectronics, which played a significant role in its economic and technological development.

As the core of FACTS technology, power electronics technology developed in two directions in the late 1940s. One was the integrated circuit, which then developed into microelectronics, its main object being information processing; the other is high-power devices, which developed into power electronics, its major function being to deal with energy. After the 1970s, a new type of electronic device, with fully controlled power, was developed with the gradual integration of these two technologies.

FACTS is a concept summarized in the development and operational experience of the existing products. Long before the formation of the concept; there are also a variety of FACTS controllers in development or application, drawing on a wealth of accumulated technical experience, as among them the static var compensator (SVC), static synchronous compensator (STATCOM) and subsynchronous resonance damper (NGH-SSR damper), etc. The proposition of the FACTS concept not only summed up a common technology base and possible power supply control functions, but also promoted the associated technical ideas, anticipating further development and application of new FACTS controllers, and eventually pushing FACTS forward to become a new power technology.

1.1.2 The Power Electronics of FACTS

After decades of development, power electronic devices have been divided into several categories and after several generations of updating, their pressure toleration, flow capacity, and switching speed are all increasing. Based on their degree of controllability, power electronics can be divided into two categories.

1.1.2.1 Semi-controlled devices

In the 1950s, silicon thyristors were invented by GE, marking the beginning of power electronics technology. Thereafter, more and more derivatives of thyristor devices followed. Up to the 1970s, a fast thyristor, a reverse conducting thyristor, a triac, an asymmetrical thyristor, and another, semi-controlled thyristor with more power and better performance were derived. However, owing to the low operating frequency of the thyristor itself, its application was greatly restricted. In addition, these devices require forced commutation circuits, so that the overall weight and volume of power electronic devices increases, reducing their efficiency and reliability.

1.1.2.2 Fully-controlled devices

Since the late 1970s, as the fully-controlled device can be controlled to switch on or off, flexibility has been greatly improved and the gate turn-off thyristor (GTO), power transistor (giant transistor, GTR), and its modules have been used in practical fields. After that, various high-frequency fully-controlled devices continued to come out, and the technology was developing rapidly. Among these devices are the metal oxide semiconductor, insulated gate bipolar transistor, MOS controlled thyristors, integrated gate-commutated thyristor, injection enhanced gate transistor, etc. Classifications and typical uses of power electronic devices are shown in Table 1.1; Table 1.2.

Table 1.1

Classifications and Typical Uses of Power Electronic Devices

Table 1.2

Domestic and Foreign Power Electronic Devices Power Levels

1.1.3 Typical FACTS Device Classification and Principle

FACTS technology is an energy conversion, transmission and control technology that uses high power semiconductor switching devices. It is a high-tech area based on the development of high-voltage and large-current electronic switching devices. Facing electric power systems, it integrates manufacturing technology, modern control technology, and the traditional power grid technology, and has become the core of FACTS. Further development of this technology will lead to a revolutionary change in power systems, greatly improve the level of security and stability of transmission lines as well as power transmission capacity, and greatly improve system reliability and operational flexibility. It can even replace the traditional mechanical breaker power electronic switches, making the traditional power system as easy to control as electronic circuits. Based on its structure, a FACTS device can be classified as shunt, series, and hybrid.

1.1.3.1 Shunt FACTS

Shunt FACTS include the SVC, the STATCOM, the magnetic shunt reactor, grading controllable shunt reactors, the thyristor controlled reactor, the thyristor switched capacitor, thyristor switched reactors, and others. Taking the SVC and STATCOM, e.g., the basic principle can be explained as follows:

1. The SVC controls specific parameters of the power system by adjusting the output of capacitive or inductive current. The SVC has been successfully applied to improving transient stability of synchronous motors and has become an important technical means of overcoming the bottleneck of power transmission. There are nearly 20 sets of SVCs put into operation in China, with a single set of maximum capacity 180 Mvar. SVCs can be applied to power systems at all levels, improving the transmission capacity and power transmission efficiency of the grid and thus improving power quality and grid stability. But when the voltage drops, there will be a problem of severe compensating capacity shortage and harmonic interference, which is effectively solved in STATCOM (Fig. 1.1).

2. The STATCOM is the core of the FACTS family and compared with conventional compensation devices, it is small in size, with good low voltage characteristics and fast response, making it the hotspot of research in the reactive power control field. It is a static synchronous generator in parallel on the system and by controlling the capacitive or inductive output current, it is able to improve the safety and stability of the power system as well as bringing huge economic and social benefits to the power industry. Based on the STATCOM’s damping characteristics, different methods can be designed for its damping controller, such as pole placement, multivariable feedback linearization, H∞ control (with good robust design methods), and intelligent control methods. In 2006, China’s first set of 50 Mvar STATCOM was put into operation in Shanghai.

Figure 1.1 Thyristor control structure of SVC.

1.1.3.2 Series FACTS

Series FACTS include the thyristor controlled series capacitor (TCSC), the thyristor switched series capacitor, the static synchronous series compensator (SSSC), the fault current limiter (FCL), the thyristor controlled phase modulator (TCPAR), etc. Taking TCSC, SSSC, FCL, e.g., to explain the basic principle as follows:

1. The TCSC is based on the conventional Series Compensation technology. When used to improve system stability and line transmission capacity, it can also damp SSR and low frequency oscillation and reduce line losses. China began research on TCSC technology in the 1990s, and the first localization TCSC project was successfully put into operation at the end of 2004. So far, more than 33 sets of TCSC have been independently developed and used in China, with a total capacity up to 10.87 Gvar (Figs. 1.2 and 1.3).

2. The SSSC has no external power supply, and its output voltage vector is orthogonal to the line current, so the voltage and current control are independent. The power transmission is controlled by increasing or reducing the inductive voltage. Transient energy storage devices may be included in the SSSC and when the additional instantaneous active power is compensated for to enhance the system’s dynamic performance, the resistive voltage of the transmission line may also increase or decrease. There are no separate SSSC devices in the world, but they have been widely used in various studies of power oscillation damping and power flow control in the grid (Fig. 1.4).

3. The basic principle of FCL is developed on the basis of a series reactor. In order to overcome the shortcomings of conventional series reactors, the switch is closed and no reactance is put into the system during normal operating conditions. When a fault occurs, the switch is quickly disconnected and the reactor is set to limit the power flow. From the perspective of developments in recent decades, FCL power electronics are divided into electronic and those based on new material. Developed by China Electric Power Research Institute and East China Power Grid Co, the series thyristor protection compensator (Thyristor Protected Series Compensation, TPSC), was installed in East China Power Grid 500 kV Pingyao substation to limit the total short-circuit current to below 47 kA. This device is put into operation to improve transient stability of EHV (extra high voltage) systems, reduce the maximum swing angle of the generator, and suppress voltage fluctuation (Fig. 1.5).

Figure 1.2 Basic structure of STATCOM.

Figure 1.3 Basic structure of TCSC.

Figure 1.4 Structure of SSSC.

Figure 1.5 The principle of FCL.

1.1.3.3 Hybrid FACTS

Hybrid FACTS include the Unified Power Flow Controller (UPFC), the Interline Power Flow Controller (IPFC), the Convertible Static Compensator (CSC), etc. Taking UPFC, IPFC, as examples to explain the basic principle:

1. The UPFC is a combination of STATCOM and SSSC, aimed at achieving the two-way power flow between series and shunt sides. Without external power storage, it can provide a series line active and reactive current compensation. By injecting a series voltage, a UPFC can independently control voltage, line impedance, and transmission angle, as well as selectively control the active and reactive power flow in the line. In addition, the UPFC can provide controllable shunt reactive power compensation, which makes UPFCs the most promising FACTS controllers. Currently, there are three UPFC devices that have been successfully put into operation; they are the UPFC project at the Inez substation in the United States, the CSC project at the Marcy substation in the United States, and the UPFC project at the Kangjin substation in South Korea (Fig. 1.6).

2. The IPFC is the latest development of applied power electronics technology, and it is made up of several DC/AC converters with all the DC sides connected together; each converter is able to provide active power to the DC link capacitor through lines connected to it. In this configuration, each converter provides SSSC series compensation to connected lines, provides flexible control of the power flow, and thus greatly improves the transmission capacity and stability and reliability of the power system (Fig. 1.7).

Figure 1.6 Basic structure of UPFC.

Figure 1.7 Basic structure of IPFC.

1.1.4 The Application of FACTS in a Power System

With fast response, no mechanical moving parts and a wide range of information, FACTS is thought to be significantly better than the conventional power flow and stability control measures. It can make full use of the existing power grid, achieve efficient use of resources and energy, realize the continuous control adjustment of power system voltage, line impedance, phase angle, and power flow, and thus significantly improve the transmission capacity of lines and the level of stability of the power system, and reduce transmission costs. Its effect on power systems is as follows.

1.1.4.1 Increasing transmission line capacity

FACTS technology allows transmission lines to overcome stability limits and substantially increase power transmission through the lines to the thermal limit, which can slow down the need for new transmission lines, improve the use of existing transmission lines, and thus not only save transmission costs and space, but also benefit environmental protection.

1.1.4.2 Provision of reactive power and voltage support

Considering power system voltage stability, when there is insufficient reactive power, it has to be compensated locally. SVCs, STATCOMs, UPFCs, and other FACTS devices can provide more rapid, continuous, and flexible compensation than traditional fixed capacitors or synchronous condensers. It is of great significance for improving system voltage quality, reducing power consumption, and ensuring the safe and reliable operation of the system.

1.1.4.3 Improving transient stability

Transient instability of power systems is caused by interference resulting from failure of other items of electrical equipment. FACTS devices can provide a quick, smooth adjustment of power, help prevent the expansion of faults, reduce recovery time and power loss in the power grid, avoid potential failures to prevent voltage collapse, thus greatly improving the transient performance of the system.

1.1.4.4 Modern large interconnected power grid

The development of the modern power grid is to link the country into a large grid, even including cross-border interconnection. The main purpose of interconnection is to provide low-cost electricity to users at all levels. FACTS technology brings flexibility to the control of the power flow and the ability to improve the stability of the power system. Thus it is possible to achieve optimal allocation of energy, reduce the spinning reserve capacity of the entire power system, improve the efficiency of electrical equipment, and reduce the cost of electricity. Therefore, FACTS technology is widely used in the power grid, and the main technical problems it can solve are the stability issue of the interconnected power grid, the bottleneck of power transmission from west to east, and the need for dynamic reactive power support in the load center. Ways in which specific problems that may occur in power systems can be solved by various FACTS