Dynamic Phasor Modeling of LCC-HVDC Systems: Unbalanced Operation and Commutation Failure

This paper develops a dynamic phasor model of a line-commutated converter high-voltage direct current (LCC-HVDC) system that includes unbalanced operation and commutation failure. This model is beneficial in studying the behavior of the HVDC systems under asymmetrical faults, and it complements the conventional transient simulation-based methods. Equally, importantly, the model includes the representation of commutation failure that may arise as a result of severe faults. Due to its selectivity of the considered harmonics, the developed model has markedly less computational intensity than an electromagnetic transient (EMT) simulation model. This gives the model a distinct advantage in the study of large-signal transients of the LCC-HVDC systems, particularly where repetitive simulations are required. Validation of the proposed model is done using a detailed EMT model of the CIGRE monopolar LCC-HVDC benchmark.