ÇUKUROVA UNIVERSITY INSTITUTE OF NATURAL AND APPLIED ...

3. FUNDAMENTALS OF DVR Mustafa İNCİ
signal firstly. In this thesis, EPLL, SRF and SOGI-PLL methods which are
comprehensively expressed in Chapter 4 are used to generate reference values.
3.3.5. Voltage Control Methods
The accuracy and dynamic behavior of the pulse width modulation and
voltage drop due to switching devices and passive components in DVR directly
affects the injected voltage generated by DVR. In available literature, there are two
voltage control systems used in the DVR applications: open loop and closed loop.
3.3.5.1. Open Loop
Usually, the control voltage of the DVR is derived by comparing the
incoming supply voltage against a desired reference voltage. Although system
stability is guaranteed in this type of control, damping is poor, and the stability
margin may not be sufficient in the presence of inverter-side filter (Vilathgamuwa et
al., 2006). In this method, the control signal , is simply compared supply voltage
against a reference voltage.
Figure 3.16. Open Loop Control Method
V
i
i
( V −V
)
= k
(3.16)
ref
s
In this control system, the voltage at source side of the DVR is compared with
the voltage at load-side reference voltage. Error between source-side and load-side
voltages is used to compare with a triangle signal in PWM module.
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