Page 126 - Power Electronic Control in Electrical Systems

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114 Power flows in compensation and control studies

Fig. 4.6 UPFC. (a) back-to-back VSCs with one VSC connected to the AC network via a shunt transformer
and a second VSC connected to the AC networkvia a series transformer; and (b) equivalent circuit based on
solid-state voltage sources.

regulation and the phase angle y cR determines the mode of power flow control
(Hingorani and Gyugyi, 2000):

1. If y cR is in phase with the voltage phase angle y l , it regulates no active power
flow.
2. If y cR is in quadrature with the voltage phase angle y l , it controls active power
flow performing as a phase shifter but drawing no reactive power from the AC
network.