Electric power conversion systems – Current conversion – Using semiconductor-type converter
Patent
1996-06-28
1998-05-26
Berhane, Adolf
Electric power conversion systems
Current conversion
Using semiconductor-type converter
363 84, H02M 704
Patent
active
057576378
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a power converter for supplying an isolated supply or other electrical source from a multiphase mains supply not having a neutral connection. More particularly, but not exclusively, the present invention relates to a power converter in which converter modules are connected in star configuration and the node voltage is compared with the node voltage of a star network in parallel to the converter modules to provide feedback signals for each converter module to ensure balanced operation.
BACKGROUND TO THE INVENTION
Referring to FIG. 1, typical prior art power conversion equipment for high power applications is shown. 3 phase lines 1, 2, 3 supply three phase power to AC to DC converter modules 4, 5 and 6. The outputs of the converter modules 4, 5 and 6 are combined via combiner 7 to provide a DC supply for a load 8 or battery etc. In this case a neutral line 9 is also provided. This ensures that the arrangement remains stable with any unbalanced currents being returned through the neutral wire 9.
Many electricity supply authorities prefer not to supply a neutral connection. If the neutral connection 9 is removed from the arrangement of FIG. 1 it becomes unstable unless the star point junction of 4,5 and 6 is somehow made to behave as if it were a neutral point.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a stable power converter for a multiphase power supply that may not be supplied with a neutral line, or at least to provide the public with a useful choice.
According to one aspect of the invention there is provided a power converter for producing an output supply from a multiphase AC supply which may not have a neutral connection, said power converter having AC input terminals for each phase of said AC supply and output terminals, said power converter further comprising: being connected between said AC terminals in a star configuration, outputs of said converter supplying output power to said output terminals; with the star connected converter modules; output terminals, compares this with a required value and produces a demand signal related thereto; of said star connected converter modules and the node of said star network and produces output signals for each phase representative of the monitored voltage difference for each phase; and for each phase with the demand signal of said output sensing means to provide a control signal for each phase which is supplied to a control input of each converter.
Preferably the star network consists of a network of equal value impedances. These impedances shall be substantially resistive. Preferably a combiner combines the output of said converter modules and supplies the combined output to said output terminals. The output supply can be AC or DC.
BRIEF DESCRIPTION OF THE DRAWINGS
Further aspects of this invention, which should be considered in all its novel aspects, will become apparent from the following description, given by way of example of possible embodiments thereof, and in which reference is made the accompanying drawings wherein:
FIG. 1: shows diagrammatically a prior art arrangement suitable for use with a multiphase power supply including a neutral connection.
FIG. 2: shows a block diagram of a power converter which produces a DC output according to a first embodiment of the invention.
FIGS. 3A-3H illustrate the operation of the feedback circuitry of the three phase converter of FIG. 2.
FIG. 4: shows a block diagram of a power converter according to an alternate embodiment of the invention.
FIGS. 5A-5H illustrate the operation of the feedback circuitry of the power converter in FIG. 2 for two phases of AC input.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring firstly to FIG. 2 a preferred embodiment producing a DC output, is shown. AC input terminals 10, 11, 12 are in use connected to a three phase AC supply having no neutral connection. Converter modules 13, 14 and 15 are connected in a star configuration across AC input terminals 10, 11 and 12. A node S is defi
REFERENCES:
patent: 5198970 (1993-03-01), Kawabata et al.
patent: 5345375 (1994-09-01), Mohan
patent: 5499178 (1996-03-01), Mohan
Chapman Dennis Allan
James David Alun
Tuck Colin John
Berhane Adolf
Switchtec Power Systems Limited
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