Page 124 - Power Electronic Control in Electrical Systems

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112 Power flows in compensation and control studies

Fig. 4.4 STATCOM. (a) VSC connected to the AC networkvia a shunt transformer; and (b) shunt connected
variable solid-state voltage source.

of a synchronous generator with zero active power generation. A more flexible
STATCOM power flow model is presented in this chapter. It adjusts the voltage
source magnitude and phase angle using Newton's algorithm to satisfy a specified
voltage magnitude at the point of connection with the AC network
V vR ˆjV vR j(cos y vR ‡ j sin y vR ) (4:7)
It should be pointed out that maximum and minimum limits will exist for jV vR j which
are a function of the STATCOM capacitor rating. On the other hand, y vR can take
any value between 0 and 2p radians but in practice it will keep close to y l .

4.2.5 The DVR
The DVR is a series connected VSC. The strength of this device is in low-voltage
distribution applications where it is used to alleviate a range of dynamic power
quality problems such as voltage sags and swells (Hingorani, 1995).