20-10-2010, 02:43 PM
Operation and Control of Single Phase Micro-
Sources in a Utility Connected Grid
Ritwik Majumder, Student Member, IEEE, Arindam Ghosh, Fellow, IEEE,
Gerard Ledwich, Senior Member, IEEE and Firuz Zare, Senior Member, IEEE
ABSTRACT: This paper proposes operation and control of
converter based single phase distributed generators (DG) in a
utility connected grid. A common utility practice is to distribute
the household single-phase loads evenly between the three phases.
The voltage unbalance between the phases remains within a reasonable
limit. However the voltage unbalance can be severe if
single-phase rooftop mounted PVs are distributed randomly between
the households. Moreover, there can also be single-phase
nonlinear loads present in the system. The cumulative effect of all
these will cause power quality problem at the utility side. The
problem can be macabre if three-phase active loads (e.g., induction
motors) are connected to the utility feeder. To counteract
this problem, we have proposed two different schemes. In this
first scheme a distribution static compensator (DSTATCOM) is
connected at the utility bus to improve the power quality. The
DSTATCOM only supplies reactive power and no real power. In
the second scheme, a larger three-phase converter controlled DG
is placed that not only supplies the reactive power but also provides
active power. The efficacies of the controllers have been
validated through simulation for various operating conditions
using PSCAD.
I. INTRODUCTION
S MORE countries are aiming at a reduction in greenhouse
gas emissions, the requirements for adding new
generation capacity can no longer be met by traditional power
generation methods of burning the primary fossil fuels such as
coal, oil, natural gas, etc. [1]. This is why distributed generators
(DG) have significant opportunity in the evolving power
system network. Both consumers and power utilities can benefit
from the widespread deployment of DG systems which
offer secure and diversified energy options, increase generation
and transmission efficiency, reduce greenhouse gas emissions,
improve power quality and system stability, cut energy
costs and capital expenditures, and alleviate the bottleneck
caused by distribution lines [2].
Properly sited DG can increase the feeder capacity limit, but
this does not necessarily produce an improvement in system
reliability or power quality, as quantified by standard indices
[3]. With improving reliability of the owner, the DG may reduce
the severity of voltage sags near the DG. The DG often
has a negative impact on reliability indices through sympathetic
tripping, required changes to utility overcurrent device settings,
and increased fuse blowing. The utility cannot assume
DG automatically improves system reliability, and action may
be required to ensure that reliability does not actually degrade
for other customers [3].
for more ::->
http://eprints.qut.edu.au/19288/1/c19288.pdf