A Study On On-Line Congestion Management With Transient Stability Constraints

Currently, the electric power utility industry is undergoing renovations from vertical monopoly to deregulation. With the electric transmission network being opened and market competition developed, the restructured power systems are expected to be operated at a greater variety of operating points and closer to their operating limit. Dynamic Congestion Management (DCM), as a new branch of the elementary congestion management, has the advantages of eliminating the line congestion and enhancing the security of the power system. It is of vital importance to study and develop effective DCM approach for a secure and economical dispatching under market environment.The research on DCM is focused mainly on two problems that challenge the independent system operators (ISO)– the first one is how to place the constraints of dynamic security into the existing steady security model of the optimal dispatch, and the other is to study coordination control measures for multi-contingencies cases. Aiming at the two aspects, a new model for the online dynamic congestion management model is proposed in this thesis.In this model, the DCM with transient stability constraint is described as a problem of nonlinear programming, whose objective is to adjust the real power output of generators to minimize the increment of power purchasing cost. The rotor angle transient stability constraints are transformed to the constraints of generators'active output shift using the optimal control methods. Thus, the difficulties of large dimension and heavy computational burden in solving the prototype of dynamic optimal adjustment can be avoided. Any prevalent method could be employed to tackle the reduced nonlinear programming.The algorithm to handle the multi-contingencies simultaneously is also proposed in this thesis. The transient stability constraints raised by each harmful contingency are assembled and imposed upon the optimal model of DCM concurrently. Such a treatment succeeds in preventing a circular or redundancy dispatch regulation and thus improves the calculating efficiency greatly.Case studies of DCM are performed in the New England 39-bus test system, the results are compared with that obtained by a static congestion management model.