06-06-2012, 05:08 PM
A Modular Single-Phase Power-Factor-Correction Scheme With a Harmonic Filtering Function
A Modular Single-Phase Power-Factor-Correction.pdf (Size: 708.62 KB / Downloads: 10)
INTRODUCTION
THE recent developments in power electronics technology
enable us to introduce power converters into
telecommunication applications to drive various loads in
single-phase power distribution systems. The expanding use
of electric loads controlled by power electronics has made
power converters an important and unquestionable part of the
modern society. Power supply systems in telecommunication
applications employ several parallel-connected ac-to-dc and
dc-to-dc power converters. Such a system offers modularity,
redundancy, and is easily scalable to higher power levels.
Such parallel-connected systems normally consist of several
single-phase power-factor-correction (PFC) stages connected
to the same input utility as shown in Fig. 1 [1]–[3]. Therefore,
the system cannot accomplish low-cost power supply and its
control could be complicated.
PROPOSED TOPOLOGY
The typical converter system in telecommunication applications
has several PFC circuits in parallel as shown in Fig. 1.
Such a system can be replaced by either dc-link shared or independent
modular scheme which consists of several ac-to-dc
and dc-to-dc power converters employing only one PFC circuit
and several NLs. Fig. 2 shows the possible combination with
isolated converter. Each scheme is capable of achieving unity
power factor with sinusoidal current waveform by injecting harmonic
current through a PFC circuit [6], [7]. Fig. 3 shows the
proposed telecommunication PFC-BC paralleled with nonlinear
loads and its waveforms.
CONTROLLER DESIGN
The control block diagram for the PFC boost converter is
shown in Fig. 5 with and without current reference generator.
Fig. 5(a) introduces the principle for the harmonic compensation
and Fig. 5(b) shows a simple control block diagram which
can be easily implemented by analog circuits. The control block
diagram consists of a dc-voltage proportional-plus-integral (PI)
controller, current controller, harmonic reference current generator,
and the disturbance. The rectified voltage can be considered
as a disturbance since the input voltage of the boost converter
is basically a dc quantity.
CONCLUSIONS
A modular single-phase PFC with a harmonic filtering function
has been presented. It has been shown that a single-phase
PFC scheme can be suitably altered to achieve harmonic filtering
function of nonlinear loads connected to the system.
proposed approach should result in lower cost. Experimental results
from a laboratory prototype system validate the PFC capability.
