Introduction: As a consequence of the European Union Renewable Energy Directive, the UK is committed to a target of more than 30% of electricity to be generated from renewable sources by 2020. The transmission network reinforcements and expansion necessary to allow the EU 2020 renewable target and long-term energy goals to be achieved in an effective and efficient manner were studied by ENA’s Electricity Network Strategy Group and detailed in their report Our Electricity Transmission Network: A vision for 2020.

It was recognized in the report that due to planning constraints and environmental concerns, traditional methods of enhancing system capacity can be difficult to achieve and consideration was given to employing the latest technology, especially where this would yield additional economical and environment benefits. One such technology potentially contributing to the achievement of the above aims is HVDC transmission.

The Western High Voltage Direct Current (HVDC) link uses the thyristor based AC/DC converter technology and was proposed to be built as a major link across the Anglo-Scottish border to increase the inter-area power transfer capability and eliminate the constraints currently imposed on the border transfer for stability reason. In addition, there are many more HVDC projects that are currently under consideration and require a model which can be used in simulation studies effectively, accurately and easily.

National Grid has not previously implemented HVDC modelling in the old system analysis suites. The model provided by DIgSILENT in PowerFactory has been studied comprehensively and the results were reported in TR (E) 466; Computer simulation Tests of HVDC converter model in DIgSILENT. One of the major short comings identified in the model is the lack of the representation of the reactive power control while the converter operation moves from one level to another. It is essential and urgent to develop the reactive power control function and incorporate it into the current model for future use. The developed model will be crossed checked and verified by means of a real time digital simulator.

Objectives: The objective of the project is to develop the PowerFactory Line-Commutated Converter (LCC) HVDC converter model for performing power flow studies and the network stability studies by National Grid engineers. The project aims to add the reactive power control, the filter switching and the converter transformer tap changes into the PowerFactory model. These areas have been identified as requiring to be addressed when the model is used to represent the thyristor based HVDC systems and operate not only at the DC system full rating but over a wide range of power transfer levels of the DC link. The project will deliver a model that can be integrated with any simplified circuits and the entire National Grid network model for power flow studies and stability studies. The work forms an essential step in developing National Grid's capability of network performances studies