Comparativo entre Estruturas de Controle de Tensão de Máquinas Síncronas (Comparison Between Voltage Control Structures of Synchronous Machines)

Daniel dos Santos Mota (motabrasil@yahoo.com.br)1, Clovis Goldemberg2


1Voith Hydro A/S
2Escola Politécnica da Universidade de São Paulo

This paper appears in: Revista IEEE América Latina

Publication Date: Dec. 2010
Volume: 8,   Issue: 6 
ISSN: 1548-0992


Abstract:
This paper compares the behaviour of two different control structures of automatic voltage regulators of synchronous machines equipped with static excitation systems. These systems have a fully controlled thyristor bridge that supplies DC current to the rotor winding. The rectifier bridge is fed by the stator terminals through a step-down transformer. The first control structure, named “Direct Control”, has a single proportional-integral (PI) regulator that compares stator voltage setpoint with measured voltage and acts directly on the thyristor bridge's firing angle. This control structure is usually employed in commercial excitation systems for hydrogenerators. The second structure, named “Cascade Control”, was inspired on control loops of commercial DC motor drives. Such drives employ two PIs in a cascade arrangement, the external PI deals with the motor speed while the internal one regulates the armature current. In the adaptation proposed, the external PI compares setpoint with the actual stator voltage and produces the setpoint to the internal PI-loop which controls the field current.

Index Terms:
Voltage control, AC generator excitation, synchronous generators   


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