Stability Analysis of a DC Power System

A stability study of a dc power system is performed by applying Nyquist stability criterion to a mathematical model that describes the behavior of the system during small disturbances about a steady-state operating point. The operating-point stability, as predicted by this linearized model, is compared with the response of the hybrid computer simulation of the actual system. Regions of instability for various system parameters, including the impedance of the ac system and the transmission line length, are established by a digital computer study. The delay and attenuation of the transmission line as well as the action of the converters with typical controllers are accurately taken into account. The linearized model presented should be helpful in the design and development of converter control systems for two-terminal dc power systems. Moreover, this method of analysis may be readily extended to include multiterminal dc power systems.