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Our HVDC expertise

The large-scale development of renewable energy sources in transmission grids, along with public demand to avoid construction of new overhead lines, has led to increased applications of long high-voltage underground cables, the addition of dynamic reactive power support, and new HVDC links using underground DC cables. The increasing penetration of power electronics-based devices in the network has a significant impact on grid performance and reliability. It requires improvements in control and protection systems and understanding of dynamic behavior.

RTE international via its HVDC Square services provides services in power systems with a focus on HVDC and FACTS. We offer comprehensive services to meet the needs of the ever-changing power industry.

With its team of experts coming from multiple backgrounds and specialized in Power Electronics and Power Systems, HVDC Square tackles a wide variety of technical challenges in power transmission.

Testing HVDC/FACTS control and protection systems

Testing implementation of new C&P functions several years after commissioning require specialized tools and skills.

  • Testing C&P software update
  • Acceleration of equipment’s service recovery
  • Analysis of events recorded on site

Dynamic performance analysis of HVDC/FACTS

Detailed power systems studies with HVDC/FACTS.

  • Development of converter station models for EMT simulations
  • EMT simulation with complex AC grids
  • Real-time simulation with physical C&P cubicles
  • Identification of potential interactions

Integration of renewables

Specific analysis for wind farms connection to transmission grids.

  • Harmonic amplification analysis
  • Sizing harmonic filters
  • Time domain EMT simulation for transformer and cable energization
  • Develop

Real-time simulation facility with HVDC/FACTS control replicas

Largest Multivendor Real Time Simulation Lab for HVDC and FACTS in Europe

  • Investigate interaction phenomena related to HVDC and FACTS devices
  • Studying and testing multi-vendors and multi-infeed schemes
  • Training engineers and support maintenance activities
  • Testing Control and Protection software update
  • Network studies and improve offline models

Principle of real-time simulation with physical control replicas

  • More than 10 real-time simulators with associated IO boards
  • 2000 m² technical rooms to host HVDC and FACTS control replicas
  • Dedicated rooms to host replicas for third-party projects


Power systems studies

Analysis of complex systems

  • HVDC/FACTS systems in transmission grids
  • Integration of long AC cables or reactive compensation device
  • Integration of wind farms

Various types of analysis

  • Electromagnetic transients (EMT) simulation
  • Harmonic analysis
  • Transient stability simulation
  • Harmonic analysis and impedance locus calculations

Harmonic analysis for offshore wind farm connection example

The TSO usually provides the harmonic impedances to the Point of Common Coupling for wind farms. RTE determined the harmonic impedances based on the minimum and maximum system short-circuit.  The final harmonic study reflects the results of several thousands of simulations that correspond to different network topologies and loading conditions.

Overall results are summarized as surfaces in the RX plan (R: real part of the impedance and X: imaginary part of the impedance)

HVDC/FACTS project management

To support projects from planning to maintenance

  • HVDC/FACTS equipment technical specification
  • Improve specifications and optimize system performance
  • Tender evaluation for HVDC applications
  • Analysis of design reports
  • Control and protection factory test witnessing
  • Preparation of testing and commissioning procedures for HVDC/FACTS control and protection systems
  • Site tests supervision
  • Training engineers and support maintenance activities


Wide range of topics for HVDC projects and EMT simulation

  • HVDC-LCC and HVDC-VSC basics
  • HVDC control and protection
  • HVDC modelling and studies
  • Maintenance of HVDC systems and integration in AC grids
  • HVDC VSC project management
  • EMT modelling and simulation – basic concepts
  • EMT modelling and simulation – advanced concepts for transmission grids

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