Random Modulation in Multilevel Converters for Distributed Generation Applications
Speaker: Paul Sernia, ITEE
When: 2003-07-22 10:00:00
Venue: 78-622
Host: Dr Geoff Walker
Abstract:Integration of renewable energy technologies into the electrical
power generation market will require a shift from a centralised
model, using a few high-power generating plants, to a distributed
generation (DG) model consisting of many low-power generating
plants. Examples of suitable renewable technologies are solar
cells, hybrid-electric vehicles, batteries or fuel cells. All of
these technologies can provide power to the grid in times of high
demand, reducing the load on conventional generating plants and
storing excess energy from the grid at off-peak times. These
renewable energy sources are typically comprised of collections of
low-voltage DC sources, requiring specialised electronics to
interface them to a high-voltage AC output. One particularly
suitable power electronics converter design is the cascaded
multilevel converter. This architecture offers efficient power flow
control on a 'per cell' basis as well as advantages in terms of
low-order harmonic cancellation. A traditional mutlilevel converter
requires that switches be synchronised for proper harmonic
cancellation. The problem arises in a cascaded multilevel converter
that the cascaded 'modules' may not be physically adjacent to each
other, especially for renewable power applications such as solar
energy, and the cost of implementing fast, intelligent
communications between modules becomes prohibitive. To date,
previous applications have used only a low number of modules and the
DC sources have been arranged in close physical proximity.
This seminar introduces the idea of using random modulation
techniques in place of synchronised switching between cascaded
modules. Random modulation has been shown to reduce harmonic
spectra of a switchmode converter, although not to the extent
achieved in multilevel converters. This is overcome by increasing
the number of cascaded modules, since tight synchronisation is no
longer required. Initial study results are presented to show the
extent to which harmonic cancellation occurs in a random situation
for increasing numbers of cascaded modules. These results are
compared with traditionally controlled cascaded multilevel
converters and further strategies for improvement are discussed.
Biography:(biography unavailable)
Type: Ph.D confirmation
Contact:Dr Geoff Walker, seminar host (walkerg@itee.uq.edu.au)
or Guido Governatori (ITEE seminar co-ordinator)
(guido@itee.uq.edu.au)