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TB 149 1999 SC 14 WG 14.29 Coordination of controls of multiple FACTS/HVDC links in the same system.

Power electronics applications in high-voltage electric power systems date from the early 1970s when converters for HVDC systems bagan using thyristors to replace mercury arc valves. Since the mid-1970s all new HVDC systems have employed thyristor valves. Advances in power electronics have extended the application of fast switching currents to AC systems as well, resulting in the technology commonly known as FACTS, Flexible AC Transmission Systems. This document is intended to provide guidelines into the kinds of interactions that can occur and the means of analysis and design that are available to assure that a coordinated response is achieved and adverse interactions are avoided.

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TABLE OF CONTENS

1 INTRODUCTION

      1.1 References

2 STARTEMENT OF WORK, STUDY PLAN, FORMAT OF REPORT

3 HVDC/HVDC INTERACTIONS

      3.1 Description of Control Structures

            3.1.1 Types of DC link to DC link interactions

            3.1.2 DC Converter Station Control Structure

            3.1.3 Where Signals can be injected into DC controls

            3.1.4 Other Control Structures

      3.2 Reason and Justifications for Applying Interaction Control

            3.2.1 Power Transfer Capability

            3.2.2 Increased System Security/Reliability

            3.2.3 Power and Voltage Control

            3.2.4 Improvements in Stability Margins

            3.2.5 Overvoltage Limitations

            3.2.6 Economic

      3.3 Problems Associated with Configurations

            3.3.1 Steady State Stability

            3.3.2 Electromechanical Stability

            3.3.3 Overvoltage

            3.3.4 Small Signal or Control Oscillations

            3.3.5 Electromagnetic Transients

            3.3.6 Subsynchronous Resonance

      3.4 Small Signal System Analysis of HVDC Control System

            3.4.1 Small Signal Model of a DC Link

            3.4.2 Calculation Procedure

            3.4.3 The Complete Current Control Open Loop Transfer Function

            3.4.4 Practical Examples

            3.4.5 Steady State Analysis for Multi-Infeed Configuration

      3.5 Study Methods

      3.6 Examples from Studies and Field Results

            3.6.1 Example Study System

            3.6.2 Steady State Voltage Power Stability

            3.6.3 Electromechanical Stability

            3.6.4 Control Stability

            3.6.5 Electromagnetic Stability

            3.6.6 The Northern Europe HVDC Cable Schemes

            3.6.7 Characteristics of the Skagerrak/Konti-Skan Systems

            3.6.8 The Baltic Cable/Kontek/Great Belt Schemes

            3.6.9 Central China and Eastern China Interconnection

      3.7 References

4 FACTS/FACTS INTERACTIONS

      4.1 Conceptual Control Structures for FACTS Devices

            4.1.1 Thyristor Controlled Series Compensator – TCSC

            4.1.2 TCSC Control Model

            4.1.3 Static VAr Compensator – SVC

            4.1.4 SVC Control Model

            4.1.5 Advanced Static VAr Compensator – STATCOM

                  4.1.5.1 General Description of the STATCOM

                  4.1.5.2 STATCOM Conceptual Control Structure

                  4.1.5.3 48-Pulse STATCOM Control Structure

      4.2 Frequency Response of FACTS Devices

            4.2.1 SVCs

            4.2.2 TCSCs

            4.2.3 STATCOMs

      4.3 Test Systems for Studies of Dynamic Interactions

            4.3.1 Test System # 1

            4.3.2 Test System # 2

            4.3.3 Test System # 3

            4.3.4 Test System # 1 with Dynamic Representation

      4.4 Control Interactions between FACTS Devices

            4.4.1 SVC Interactions: Conventional Eigen value Analysis

            4.4.2 SVC integrations: High-Frequency Eigen value Analysis

            4.4.3 TCSC Interactions: High-Frequency Eigen value Analysis

      4.5 High Frequency Analysis – TCSC to SVC Interactions

      4.6 Operational Experience at the Hydro-Quebec System (Canada)

            4.6.1 Supervisor

            4.6.2 Optimizer

      4.7 Operational Experience at the ESKOM System (South Africa)

            4.7.1 Cape Transmission SVCs

                  4.7.1.1 SVC parallel control Philosophy

                  4.7.1.2 Operational Experience

            4.7.2 Natal SVCs

                  4.7.2.1 Coordination of Controls between the SVCs

                  4.7.2.2 Operational Experience

      4.8 References

5 HVDC/FACTS INTERACTIONS

      5.1 Possible Configurations and Control Structures

      5.2 Control Interactions between HVDC and FACTS Devices

            5.2.1 Steady-State Control Interactions

            5.2.2 Electromechanical Oscillation Interactions (0-3/5 Hz)

            5.2.3 Small Signal Oscillations or Control Interactions (2-15 Hz or higher)

            5.2.4 Subsynchronous Resonance Interactions (10-50/60Hz)

            5.2.5 Electromagnetic transients, High Frequency or Harmonic Resonance Interactions (>15 Hz)

      5.3 Examples from System Studies and Field Results

            5.3.1 Mid Continent Area Power Pool (MAPP) System

                  5.3.1.1 Electromechanical Interactions

                  5.3.1.2 Small Signal or Control Oscillations

                  5.3.1.3 Subsynchronous Resonance

            5.3.2 India Western Region System

            5.3.3 Chateauguay System (Canada)

            5.3.4 Intermountain System (IPP DC) (USA)

            5.3.5 Study System of HVDC/TCSC

      5.4 References

6 FUTURE TRENDS

      6.1 New Device Technology

      6.2 New Control Algorithms

      6.3 Information System Trends

      6.4 Market Trends

      6.5 References

7 CONCLUSIONS