Library Categories: Technical Reports

Impact of HVDC Convertor Technology Choice on Reinforcement within the GB Grid

HVDC ‘bootstraps’ are becoming a key option in the reinforcement of the transmission system. As the generation mix moves towards renewables, sources are becoming more dispersed and located further from load centres, requiring extensive transmission network upgrades to get the power to where it is needed. As a result of restrictions in space and consenting issues locating new circuits onshore, there has been a move to locate new circuits offshore. This requires long cable circuits, where HVDC technology must be used. This note explores how the choice of HVDC technology can affect the system integration challenge of the required upgrades to the transmission system. Download file below.

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Stability Assessment and Mitigation of Converter Interactions (Phase 2): Report II-Development and Validation of Type 3 Turbine Impedance

The integration of AC connected wind farms into the existing power network has significantly changed the characteristics of the system and adequate small signal wind turbine models will be required to assess system stability considering the existence of difference converter technologies. While the small signal behaviour of Type 4 turbine has been extensively studied, the small signal impedance of doubly-fed induction generator (DFIG) based Type 3 turbine has not been well understood. The purpose of this study is to develop small signal admittance model of Type 3 turbine under different control modes and operating points. In this report the admittances of Type 3 turbine are then compared to the Type 4 turbine to highlight the main differences between the two. The small-signal admittances of both turbine types from the analytical models are verified against the measurements from time-domain models.

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Stability Assessment and Mitigation of Converter Interactions (Phase 2): Report I-Development and Validation of LCC HVDC System Impedance Models

This report concentrates on the development of small-signal LCC converter and LCC HVDC system models. The development of the analytical impedance model intends to provide further insight into the impact of circuit and control structure/parameters on system impedance, and similarly highlight the factors that need to be considered when an LCC HVDC connection is defining its frequency-dependent impedance accurately ahead of a network scale small-signal interaction study being performed. The developed impedance models can then be used for assessing stability and interactions between different converters (e.g., MMC, LCC, wind farm, etc.).

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