US 5,638,263 AGranted

Low and medium voltage PWM AC/DC power conversion method and apparatus

AssigneeHalmar Robicon Group

InventorsKenneth Opal, Harry Abrams, Peter Hammond

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Abstract

A power supply apparatus and method for supplying direct current power to low and medium voltage DC loads wherein a multi-phase transformer having multiple secondary windings provides multi-phase power to multiple power cells, each of which have a single DC output and are controllable by a modulation controller. The primary and secondary windings in the power transformer may be star- or mesh-connected; the secondary windings may be shifted in phase. Because the power cells can be connected in series, the maximum output voltage for each cell may be less than the maximum line-to-line voltage. The power cell output can have variable DC voltage and current which can be controlled using pulse-width modulation techniques. AC input power is converted to DC output power for each power output line. Output power modulation can be produced by interdigitating a selected number of carrier signals so that harmonic components reflected back to the input are attenuated.

Claims43

Dependent claims

A power converter for use with a DC load comprising:

(a) a multi-phase power transformer, said power transformer having at least one primary winding circuit and a plurality of secondary winding circuits, said at least one primary winding circuit being electrically connectable to a source of multi-phase AC power;
(b) a plurality of power cells, each of said plurality of power cells having an input connected with one of said plurality of secondary winding circuits, each of said plurality of power cells having a controllable output to such DC load, and respective ones of said plurality of power cells being electrically connectable with the common line of such DC load;
(c) modulation control means connected with respective ones of said plurality of power cells, so that the voltage of said respective ones of said plurality of power cells may be controlled, said modulator control means further including means for selectively controlling a switching event of each of said plurality of power cells so that said switching event of respective one of said plurality of power cells is spaced in time from said switching event of respective others of said plurality of power cells to produce a smooth DC output;
and
(d) each of said plurality of power cells having:
(i) a rectifier electrically connected with a respective one of said plurality of secondary winding circuits and having an electrical output;
(ii) a smoothing filter having an electrical output, said smoothing filter being connected with said electrical output of said rectifier;
(iii) a chopper having an output, said chopper being connected with said smoothing filter;
and
(iv) a current controller having an output, said current controller being connected with said output of said chopper, said output of said current controller being connected with respective one of said power output lines to such DC load.

7 more elements

A power converter for use with a DC load comprising:

a multi-phase power transformer, said power transformer having at least one primary winding circuit and a plurality of secondary winding circuits, said primary winding circuit being electrically connectable to a source of multi-phase AC power;
(b) a plurality of power cells, each of said plurality of power cells having an input connected with a respective one of said plurality of secondary winding circuits, each of said plurality of power cells having a controllable output to such DC load, respective ones of said plurality of power cells being serially-connected with respective others of said power cells in each power output line to such DC load, and respective ones of said plurality of power cells being electrically connectable with the common line of such DC load;
(c) each of said plurality of power cells having
i. a rectifier connected to one of said secondary windings,
ii a smoothing filter connected to said electrical output of said rectifier, and
iii a chopper connected to said smoothing filter, and the output of said chopper connected to respective one of said power output lines of such DC load;
(d) modulation control means connected to each of said chopper, so that the output of said chopper may be controlled, said control means having
i. a plurality of local modulator controllers connected to respective ones of said plurality of power cells, and
ii. a master modulator controller operably connected to each of said plurality of local modulator controllers;
and
(e) said modulation control means further having means for selectively controlling a switching event of each of said plurality of power cells so that said switching event of respective one of said plurality of power cells is spaced in time from said switching event of respective others of said plurality of power cells to produce a smooth DC output.

8 more elements

A method of controlling DC power to a DC load comprising:

(a) transforming an input voltage to a plurality of secondary voltage sources;
(b) supplying power to said DC load from a plurality of power cells fed from said plurality of secondary voltage sources;
(c) applying a current to said DC load from a plurality of said power cells;
(d) selectively controlling the output of said power cells to one of a preselected positive voltage level, a preselected negative voltage level, and a generally zero voltage level;
(e) selectively controlling a switching event of each of said power cells so that said switching event of respective one of said plurality of said power cells is spaced in time from said switching event of respective others of said plurality of power cells to produce a smooth DC output;
(f) selectively applying at least one control signal to said plurality of said power cells so that each of said plurality of power cells conducts a current at a predetermined voltage, with a predetermined polarity, and for a predetermined duration;
and
(g) interdigitating a preselected number of carrier signals to each of said plurality of said power cells so that harmonic components in a power frequency spectrum are generally attenuated.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/351,822Filed 8 Dec 1994 · continuation in part
Priority: 1 Mar 1994
Granted: 10 Jun 1997
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H02M 3/285
Using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC: single converters…
H02M 3/337
Using semiconductor devices only: in push-pull configuration
H02M 7/23
Using semiconductor devices only: arranged for operation in parallel
H02M 7/4835
Converters with outputs that each can have more than two voltages levels: comprising two or more cells, each including a switchable capacitor, the…