Control system for a power converter and method of controlling operation of a power converter
First Claim
1. A control system for a controlled current source that receives DC power as an energy input and provides an AC power output for delivery to an AC power network, the AC power output having an output voltage, the control system comprising:
- a. a voltage signal device, connectable to the controlled current source, for providing a voltage feedback signal representing voltage in the AC power output as an input to control the controlled current source; and
b. an impedance current regulator for generating an impedance current signal as a function of characteristics of the AC power output from the controlled current source.
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Accused Products
Abstract
A control system (20) for a power converter (22) designed to convert DC power from a source (30) such as a battery, flywheel or fuel cell into AC power. The control system includes an impedance current regulator (106) for providing an impedance current signal to a summing unit (110) where it may be combined with real and reactive current command signals provided from respective sources (62, 64). The resultant current signal provided by the summing unit is provided to a voltage correction unit (112) that uses the resultant current signal in developing a correction voltage signal provided to the power converter. The correction voltage signal contains information used by the power converter in adjusting the real and reactive currents in its output AC power based on the ability of the AC power network to accept changes in current. Multiple power converters having the control system of the present invention may be connected in parallel to a single AC load or multiple AC loads, without the need for a separate control system interconnecting the power converters. The control system may be advantageously incorporated into a distributed generation network and in uninterruptible power systems, whether or not such systems are included in a distributed generation network.
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Citations
51 Claims
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1. A control system for a controlled current source that receives DC power as an energy input and provides an AC power output for delivery to an AC power network, the AC power output having an output voltage, the control system comprising:
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a. a voltage signal device, connectable to the controlled current source, for providing a voltage feedback signal representing voltage in the AC power output as an input to control the controlled current source; and
b. an impedance current regulator for generating an impedance current signal as a function of characteristics of the AC power output from the controlled current source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A system for providing AC power to an AC power network, the system intended for use with a first source that provides a reference AC voltage signal, a second source that provides a real current command signal and a third source that provides a reactive current command signal, the system comprising:
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a. a controlled current source including;
i. a source of DC power;
ii. a converter for converting said DC power to AC power having an output voltage;
b. a current command unit for generating a resultant current command signal, wherein said current command unit is connected to said controlled current source and is connectable to said first and second sources, said current command unit including;
i. an impedance current regulator that provides an impedance current signal; and
ii. a summing unit for adding said impedance current to the real current command signal from the second source and the reactive current command signal from the third source so as to create said resultant current command signal. - View Dependent Claims (32, 33, 34, 35)
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36. An impedance current regulator for use in a power converter control system including a power converter providing an AC power output, a first source for a reference AC voltage signal, a second source for a real current command signal, a third source for a reactive current command signal, and a voltage signal device for generating a feedback voltage signal representing voltage of the AC power output from the power converter, the impedance current regulator comprising;
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a. a difference unit, connected to the device and to the first source, for determining a voltage difference between the reference AC voltage signal and a feedback voltage signal and generating a voltage difference signal representing said voltage difference;
b. a gain unit connected to said difference unit for multiplying said voltage difference signal by a first gain so as to generate an impedance current signal; and
c. a summing unit, connected to said gain unit, the second source, the third source and the controlled current source, that combines said impedance current signal with the real current command signal and the reactive current command signal to produce a resultant current signal usable for controlling the power converter. - View Dependent Claims (37, 38)
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39. An AC power system comprising:
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a. a power converter for converting a DC power input to an AC power output having an output voltage, said power converter having a rated output voltage and a rated output current;
b. a first source for providing a reference AC voltage signal;
c. a second source for providing a real current command signal;
d. a third source for providing a reactive current command signal;
e. an impedance current regulator including;
i. a difference unit, connectable to said power converter and said first source, for determining the voltage difference between said output voltage from the power converter and said reference AC voltage and providing a voltage difference signal representing said voltage difference;
ii. a gain unit, connected to the difference unit, for multiplying said voltage difference signal by a gain 1/R, where R is 2-20% of the rated output voltage divided by the rated output current, so as to generate an impedance current signal;
iii. a summing unit, connected to said gain unit and connectable to said second source and said third source, for adding said impedance current signal to said real current command signal and said reactive current command signal to produce a resultant current command signal; and
f. a voltage correction unit, connected to said summing unit and connectable to said power converter, for multiplying said resultant current command signal by a gain P to generate a correction voltage signal that is provided to said power converter.
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40. A method of controlling the operation of a power converter connected to an AC power network that provides an AC power output, the method comprising the steps of:
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a. providing reference AC voltage signal representing output voltage from the power converter;
b. generating an impedance current command signal, wherein said impedance current command signal is generated based on said reference AC voltage signal; and
c. generating a voltage command signal for controlling the operation of the power converter based on said impedance current command signal and providing said voltage command signal to the power converter. - View Dependent Claims (41)
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42. A method of controlling the supply of AC power to at least one load comprising the steps of:
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a. connecting in parallel a plurality of power converters, each for converting DC input power from a corresponding respective DC power source into an AC output power having an output voltage;
b. relative to each of said plurality of power converters, performing the steps of;
i. providing a reference AC voltage signal representing output voltage from the power converter;
ii. generating an impedance current command signal, wherein said impedance current command signal is generated based on said reference AC voltage signal; and
iii. generating a voltage command signal for controlling the operation of the power converter based on said impedance current command signal and providing said voltage command signal to the power converter;
iv. providing said AC output power from at least one of the power converters to said at least one load. - View Dependent Claims (43)
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44. A distributed generation network, comprising:
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a. an AC power network for providing AC power;
b. a DC power source for providing DC power;
c. a power converter for converting said DC power into AC power, said power converter connected to said AC power network and said DC power source; and
d. a control system connected to said power converter for providing a voltage command signal that controls the operation of said power converter, wherein said control system generates (i) a voltage feedback signal representing voltage in said AC power provided by said DC power source and (ii) an impedance current signal as a function of AC power provided by said DC power source, further wherein said control system generates said voltage command signal based on said voltage feedback signal and said impedance current signal. - View Dependent Claims (45, 46, 47)
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48. An uninterruptible power supply, comprising:
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a. an AC power network for providing AC power;
b. a DC power source for providing DC power, wherein said DC power source does not directly use fuel in developing said DC power;
c. a power converter for converting said DC power into AC power, said power converter connected to said AC power network and said DC power source; and
d. a control system connected to said power converter for providing a voltage command signal that controls the operation of said power converter, wherein said control system generates (i) a voltage feedback signal representing voltage in said. AC power provided by said DC power source and (ii) an impedance current signal as a function of AC power provided by said DC power source, further wherein said control system generates said voltage command signal based on said voltage feedback signal and said impedance current signal. - View Dependent Claims (49)
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50. An AC power system connectable to an AC power network, the system comprising:
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a. a plurality of DC power sources for providing DC power;
b. a plurality of power converters for converting DC power into AC power, each of said plurality of power converters connected to an associated one of said plurality of DC power sources, further wherein said power converters are connected in parallel;
c. a plurality of control systems, each connected to an associated one of said plurality of power converters, for providing a voltage command signal that controls the operation of said associated power converter, wherein said each control system generates (i) a voltage feedback signal representing voltage in said AC power provided by said DC power source connected to said associated one of said power converters and (ii) an impedance current signal as a function of AC power provided by said DC power source connected to said associated one of said power converters, further wherein said each control system generates said voltage command signal based on said voltage feedback signal and said impedance current signal.
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51. A control system for a three-phase power converter for converting DC power into three-phase AC power, the converter having at least first and second output nodes for said AC power, said control system comprising:
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a. a first control system including;
i. a voltage signal device, connectable to the power converter, for providing a voltage feedback signal representing voltage in the AC power output from the first output node as a first input to control the power converter; and
ii. an impedance current regulator for generating an impedance current signal as a function of characteristics of the AC power output from the first output node of the power converter; and
b. a second control system including;
i. a voltage signal device, connectable to the power converter, for providing a voltage feedback signal representing voltage in the AC power output from the second output node as a second input to control the power converter; and
ii. an impedance current regulator for generating an impedance current signal as a function of characteristics of the AC power output from the second output node of the power converter.
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Specification