Constant-Parameter VBR Synchronous Machine Model for Studies of Unbalanced Faults in PSCAD

Faults and unbalanced operation of generators in power systems require appropriate models in electromagnetic transient (EMT/EMTP-type) simulation programs used for system studies. Therefore, it is essential to have computationally efficient models of synchronous machines that can also predict the unbalanced conditions and generator protection operation that is often realized by monitoring the neutral circuit current. The so-called constant-parameter voltage-behind-reactance (CP-VBR) machine models have recently been introduced for widely used nodal-analysis-based EMTP simulators as computationally advantageous alternatives to the traditional qd0 models. This paper advances the previous work and generalizes the CP-VBR model to include the floating neutral point by extending the equivalent conductance matrix that is used for interfacing within the EMTP solution. The new model is implemented in the PSCAD/EMTDC program and is demonstrated to have advantages over the built-in traditional qd0 model in studies with unbalanced faults.