ÇUKUROVA UNIVERSITY INSTITUTE OF NATURAL AND APPLIED ...

4. MODELING OF PROPOSED DVR Mustafa İNCİ
presented with different control algorithms and different topologies in dynamic
voltage restorer. Voltage sag and swell must be detected fast and compensated
accurately. SRF and EPLL are widely used for sag/swell detection and reference
extraction. In addition to these controllers, SOGI-PLL is used to generate reference
signals when sag/swell is detected. The DVR must inject the series voltage according
to several criteria. In proposed system, it uses presage compensation method which
prevent phase-jump problem and requires less power transfer compared to in-phase
compensation method. Due to the lack of damping and poor dynamic performance in
the open loop control, the closed-loop control is preferred in proposed method.
4.3.1. Sag Detection
Many sag detection methods are presented with different control algorithms
in literature. Voltage sag and swell must be detected fast and compensated
accurately. SRF and EPLL are widely used for sag/swell detection and reference
extraction. In addition to these controllers, SOGI-PLL is a new method to generate
reference signals when sag/swell is detected. This section is also to explain the
structures of the EPLL, SRF, SogiPLL for three phase Dynamic Voltage Restorer for
sag/swell compensation and consists of their comparison results.
4.3.1.1. Enhanced Phase Locked Loop (EPLL)
This section analysis Enhanced Phase-Locked Loop (EPLL) which is used to
obtain signal magnitude and phase angle information in DVR systems. Conventional
PLLs are used to extract phase angle of a signal. However, EPLL has a capability
determination of amplitude and phase angle detection compared to conventional
PLLs.
The main building block of the system is an enhanced phase-locked loop
(EPLL) which extracts the synchronised fundamental component of the input signal
and its amplitude, phase angle and frequency(Karimi et al, 2005). When compared
60