A New Method to Design Robust Power Oscillation Dampers for Distributed Synchronous Generation Systems

This paper presents a new methodology for the design of power oscillation dampers (PODs) for synchronous generators connected to distribution networks. The proposed methodology provides controllers capable of fulfilling robustness requirements and also making an effective trade-off between oscillation damping enhancement and generator terminal voltage performance. A description of the nonlinear dynamical model to be controlled in the form of norm-bounded linear differential inclusions (NLDIs) is adopted at the design stage of the controller. This is different from most of the existing POD design methods, where the control design is essentially based on a simplification of the nonlinear dynamical model in the form of linear time-invariant (LTI) models. The use of NLDIs allows us to consider the system nonlinearities as model uncertainties, and then we take into account such uncertainties at the controller design stage using a robust control methodology. Once that this NLDI takes the nonlinear behaviors of the system into account, it can better represent the relatively large excursions that occur in the system states, allowing us to add a constrain to the control problem formulation imposing a certain acceptable performance to the generator terminal voltage during transients. The proposed algorithm can be easily handled by using linear matrix inequalities (LMIs) solvers. A cogeneration plant of 10 MW added to a distribution network constituted by a feeder and six buses is adopted as a test system. The results show that the two designed objectives are quite satisfactorily achieved.