Using DQ0 signals based on the central angle reference frame to model the dynamics of large-scale power systems

With increasing penetration of distributed and renewable sources into power grids, the dynamic behavior of large-scale power systems is becoming increasingly complex. These recent developments have led to several models attempting to simplify the analysis of dynamic phenomena, among them are models based on the dq0 transformation. A question that often arises when modeling interconnected systems based on dq0 quantities is how to choose the reference frame. One approach is to model the network and its components using a dq0 transformation that is based on a unified reference frame. However, when no generator is large enough to be considered an infinite bus, the unified reference frame may lead to unstable models, since the real frequency may deviate from the nominal frequency used as a reference. In this paper we propose to solve this problem by using the central angle as a basis for the dq0 transformation. Such an approach leads to models which are valid at high frequencies, and can also be used with systems with varying frequencies and no infinite bus. The proposed approach is demonstrated using networks with 9 and 57 buses.