DYNAMIC STABILITY ASSESSMENT MODEL OF A PARALLEL AC-DC POWER SYSTEM.

A linearized or small displacement model of an ac-dc system has been developed and verified by comparison with a detailed hybrid computer representation of the system, the contribution being the linearized equations which permit the machine and the dc link to be combined in a form which is amenable to linear control and eigenvalue analysis. This allows one to study the dynamic performance of an ac-dc system, including the interaction between machine controls (excitation system and power system stabilizer) and the controls associated with the dc link (current regulator with dc modulation). The techniques set forth are general and may be extended to any number of machine and dc links in any combination. Perhaps, more important is that these techniques may be used to readily incorporate the dynamic characteristics of a dc link into a standard digital program for dynamic stability or security assessment studies of an ac-dc power system. It is clear, however, that the resulting equations are not applicable for large system excursions as would occur in transient stability studies, for example.