Total transfer capability assessment of HVDC tie‐lines in asynchronous grids

Abstract

Abstract This paper discusses how frequency‐stable operational decision‐making of asynchronous grids with intensive high‐capacity HVDC tie‐lines, can be achieved leveraging a novel total transfer capability (TTC) evaluation approach. This problem is formulated as a hierarchical optimization model with multiple decision‐makers, in which the master problem is solved by the coordinator to determine the base case maximum acceptable transmission power of each HVDC tie‐line, while the sending‐ and receiving‐end grid's local TSO each autonomously solves a frequency constrained optimal power flow sub‐problem. Coordinated fast and slow frequency arrest strategies are fully integrated into the TTC assessment framework, which not only ensure that last‐resort protections are not triggered following the HVDC bi‐pole block contingency, but also take advantage of the potential control capability of the sending‐ and receiving‐end grids and would therefore increase the TTC of HVDC tie‐lines. A decentralized algorithm based on accelerated analytical target cascading is developed to solve the formulated model. Case studies on a modified two‐area RTS‐96 system and a practical large‐scale system demonstrate the effectiveness of the proposed approach.

Keywords

• Optimisation techniques
• Control of electric power systems
• Optimisation techniques
• d.c. transmission