Efficient approach for commutation failure immunity level assessment in hybrid multi‐infeed HVDC systems

Abstract

Commutation failure (CF) of hybrid multi-infeed high voltage-direct current (HMIDC) systems, comprising line commutated converter-based high-voltage direct current (LCC-HVDC) and voltage source converter-based high-voltage direct current (VSC-HVDC) links, has been mainly analysed by electromagnetic transient simulation tools, resulting in heavy workload and long computational time. This study proposes an efficient approach for CF immunity level assessment based on CF immunity index in HMIDC systems. Thus, an equivalent dual-bus analytical model of the HMIDC systems is first established, which then provides a theoretical basis for defining an equivalent voltage stability indicator (EVSI). It is then shown that such an EVSI index can be employed in the proposed approach. Moreover, the proposed approach is validated by a hybrid dual-infeed HVDC system. In particular, an unexpected phenomenon is observed that the CF characteristic of the LCC-HVDC link is somewhat deteriorated, due to the incorporation of the VSC-HVDC link when the VSC-HVDC link feeds into the alternating current system with both active and reactive power transferred in relatively high levels close to their limits.