DC Protection Design for VSC-HVDC Systems Based On Transient Stability Issue

HVDC transmission systems are an attractive option for transmitting bulk power through long distance. Protection of HVDC grids plays a major role to have a secure and reliable power delivery to customers. However, design of DC protection has always been a challenge. On the other hand, transient stability of AC/DC grid is important, especially when it comes to situations with faults. The AC/DC grid should keep its stability during and after DC fault interruption. Based on grid characteristics and dynamics, there can be different solutions and circuit breaker selection for different HVDC grids. An effective design of DC protection can reduce system cost, while assuring system security at the same time. This study investigates design of HVDC protection considering system transient stability. The paper presents a method to select appropriate circuit breakers based on transient stability of AC/DC grid. The proposed method can keep transient stability under DC fault condition while avoiding over-qualified and more expensive DCCBs. Different simulation tests have been performed in PSCAD platform and test results are discussed in this study.