Transient Stability and Performance Based on Nonlinear Power Flow Control Design of Renewable Energy Systems

AbstractIn this paper, the swing equations for renewablegenerators are formulated as a natural Hamiltonian system withexternally applied non-conservative forces. A two-step processreferred to as Hamiltonian Surface Shaping and Power FlowControl (HSSPFC) is used to analyze and design feedbackcontrollers for the renewable generator system. The resultsof this research include the determination of the requiredperformance of a proposed Flexible AC Transmission System(FACTS)/storage device, such as a Unified Power FlowController (UPFC), to enable the maximum power output ofa wind turbine while meeting the power system constraintson frequency and phase. The UPFC is required to operateas both a generator and load (energy storage) on the powersystem in this design. Necessary and sufficient conditions forstability of renewable generator systems are determined basedon the concepts of Hamiltonian systems, power flow, exergy (themaximum work that can be extracted from an energy flow)rate, and entropy rate. An illustrative example demonstratesthis HSSPFC methodology. It includes a 600 kW wind turbine,variable speed variable pitch configuration. The wind turbineis operated with a turbulent wind profile for below-rated windpower conditions. The wind turbine is connected in seriesthrough a UPFC to the infinite bus. Numerical simulationcases are reviewed that best demonstrate the stability andperformance of HSSPFC as applied to a renewable energysystem.6 Halama