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TB 536 2013 C4/B4/C1.604 Influence of Embedded HVDC Transmission on System Security and AC Network Performance

This brochure highlights the gain in flexibility provided by an embedded HVDC link (defined as a DC link with at least two ends connected to a single synchronous AC network) for an existing HVAC grid. It also points out the possible technical issues that may arise, along with the different capabilities and performances depending on the underlying DC technology. Illustrations through existing or planned projects are proposed, in addition to open models for a benchmark network and VSC converters.

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TABLE OF CONTENTS

1    INTRODUCTION

      1.1    Drivers for the development of embedded HVDC systems

      1.2    Definition of embedded HVDC system

      1.3    Overview of past work within CIGRE

      1.4    Purposes and organization of the document

2    STATE OF THE ART

      2.1    Introduction

      2.2    HVDC transmission using line-commutated current-source converters

      2.3    HVDC transmission using self-commutated voltage-source converters

      2.4    Main LCC and VSC HVDC features, and limitations compared to HVAC

            2.4.1    The specific case of back-to-back configuration

      2.5    New trends in VSC-HVDC

            2.5.1    Existing VSC topologies: recent advances and remaining limitations

            2.5.2    Toward DC fault current blocking capability: the full-bridge valve

            2.5.3    The hybrid VSC topology

      2.6    HVDC link technologies

           2.6.1    Submarine and underground cables

           2.6.2    Overhead lines

3    DESCRIPTION OF PROJECTS

      3.1    Existing embedded HVDC links

            3.1.1    Caprivi link (Namibia)

           3.1.2    Kii Channel HVDC Project (Japan)

            3.1.3    Fenno-Skan (Finland-Sweden)

           3.1.4    Directlink (Australia)

            3.1.5    Murraylink (Australia)

           3.1.6    Minami Fukumitsu (Japan)

           3.1.7    Kingsnorth HVDC Link (England)

            3.1.8    Other existing embedded HVDC links

      3.2    Projects of embedded HVDC links

            3.2.1    France-Spain HVDC link

            3.2.2    ALEGRO (Belgium-Germany)

            3.2.3    France-Italy HVDC link

            3.2.4    Switzerland-Italy: Greenconnector project

            3.2.5    The Western HVDC Link (UK)

            3.2.6    South-West Link (Sweden-Norway)

4    SYSTEM TECHNICAL PERFOMANCE ISSUES WITH EMBEDDED HVDC LINES 

      4.1    Power flow control functionalities

            4.1.1    Static power flow optimization

            4.1.2    Overload capability

            4.1.3    Special power flow controls for LCC-HVDC

            4.1.4    Automatic frequency control

            4.1.5    Black start

      4.2    Voltage and reactive power support functionalities

            4.2.1    Voltage and reactive power management under normal operation

            4.2.2    Voltage support under contingency conditions

      4.3    System stability enhancement functionalities

            4.3.1    Power oscillation damping

            4.3.2    Transient stability and fault recovery

            4.3.3    Subsynchronous damping enhancement

5    BENCHMARK MODELS 

      5.1    Models expectations

      5.2    LCC converter model

      5.3    VSC converter models

            5.3.1    VSC-HVDC modeling for power system steady-state studies

            5.3.2    VSC-HVDC modeling for dynamic studies

      5.4    HVDC line modeling

      5.5    Network benchmark model

            5.5.1    General considerations of benchmark network created “from scratch”

            5.5.2    Descriptions of the benchmark Network

            5.5.3    An example benchmark network implementation and simulations

6    INSERTING A NEW HVDC INTO AN AC NETWORK: AN OPERATIONAL PERSPECTIVE 

      6.1    Long-term planning studies

            6.1.1    Drivers for embedded HVDC

            6.1.2    Technical evaluations particular to HVDC

            6.1.3    Credible faults in reliability or security standards: highlight on AC to DC conversion

            6.1.4    Organisational issues in planning

      6.2    First HVDC operations

      6.3    Daily HVDC operations

            6.3.1    Control room aspects

            6.3.2    Coordination HVDC links in an international setting

7    CONCLSUIONS AND PROSPECTS

8    LEXICON

9    REFERENCES

10   APPENDIX

      10.1     Terms Of Reference of the group

      10.2     Usual applications of HVDC (embedded or not)

            10.2.1    Submarine and underground cable transmission

            10.2.2    Long-distance bulk-transmission

            10.2.3    Offshore transmission of renewable energy

            10.2.4    Infeed to large urban areas

            10.2.5    Weak AC network connections

            10.2.6    Asynchronous interconnection

            10.2.7    Toward DC segmented grids

      10.3     HVDC systems based on line-commutated converters (LCC-HVDC)

            10.3.1    Description of classical HVDC

            10.3.2    Operation of the LCC-HVDC system

            10.3.3    Effects of different control strategies

      10.4     Voltage Source Converter based HVDC system (VSC-HVDC)

            10.4.1    2-level VSC-HVDC converters

            10.4.2    Multi-Level VSC-HVDC converters

      10.5     HVDC configurations

            10.5.1    Back-to-Back Configuration

            10.5.2    Monopolar Configuration

            10.5.3    Bipolar Configuration

            10.5.4    Multiterminal Configuration

      10.6     HVDC links connected to weak AC systems

      10.7     Special case study of VSC-HVDC inserted in AC networks

            10.7.1    Series operation of an AC line and VSC HVDC

            10.7.2    Parallel operation of an AC-line and VSC-HVDC

      10.8     VSC-HVDC modeling for power system steady-state studies

      10.9     Load-flow results for the benchmark network model