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UBC Theses and Dissertations

Modelling of parallel HVDC-AC power systems for dynamic studies and optimal stabilization Metwally, Aly Abdelhameed


Due to the fast response, the hvdc lines, when properly controlled, are very useful in stabilizing power systems. In this thesis dynamic modelling and linear optimal controls for dc/ac parallel power systems are Investigated. Beginning with a detailed representation of one machine-infinite bus dc/ac parallel power system several reduced order models with very good accuracy are developed. They are derived mainly through eigenvalue analysis but are compared in detail with the high order nonlinear model tests. Linear optimal control schemes, comprising excitation and/or dc reference current control signals, are designed and tested for two different one machine-infinite bus systems. After that a dynamic model for a three-terminal dc line in parallel with a delta-connected ac system is developed and again linear optimal controls are designed and tested. Two systems are studied; a two machine-infinite bus system and a three machine system. For each system two cases are investigated; two rectifiers and one inverter, or one rectifier and two inverters. It is found that in all cases the hvdc reference current control provides the most effective means in stabilizing large power systems.

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