Bilateral power converter for a satellite power system

• US 5,359,280 A
• Filed: 02/04/1994
• Issued: 10/25/1994
• Est. Priority Date: 01/10/1992
• Status: Expired due to Fees

• Current Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Lenk, Ronald J., Canter, Stanley
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/192,186
• Time in Patent Office: 263 Days
• Field of Search: 323/282, 323/283, 323/222, 323/224, 323/284, 323/285, 323/259, 323/263, 323/906, 363/16, 320/30, 320/32, 320/39, 320/40
• US Class Current: 323/282
• CPC Class Codes: B64G 1/428 Power distribution and management
• CPC Class Codes: G05F 1/66 Regulating electric power
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A bilateral power converter (10) for a satellite power system comprises a battery (12), an inductor (14), a switching means (18, 20), and a controller (16). The battery (12) preferably has a first and second terminals. The inductor (14) is coupled to the first terminal of the battery (12) and the switching means (18, 20). The switching means (18, 20) selectively couples the second end of the inductor (14) to a bus (28) or to ground ill response to a control signal. The controller (16) monitors the bus (28) voltage, current flow to the battery (12) and the current flow through the switching means (18, 20). The controller (16) also receives control signals from the satellite'"'"'s computer (13) and automatically regulates the voltage on the bus (28) by adjusting the duty cycle of the signal output by the controller (16) to the switching means (18, 20). Responsive to the duty cycle of the signal output by the controller (16), the bilateral converter (10) acts either as a buck converter or a boost converter to charge or discharge the battery according to the amount of power on the bus (28).

Claims

1. A bilateral power converter system comprising at least one bilateral power conversion unit, said at least one power conversion unit comprising:

at least one inductance having a first terminal and a second terminal, said first terminal for coupling to a first terminal of an electrical power source/sink;

a common bus for coupling to a second terminal of the power source/sink;

a power bus for coupling to an electrical power source;

a capacitance coupled between said power bus and said common bus;

at least one first switching means having a first terminal coupled to said second terminal of said at least one inductance, a second terminal coupled to said common bus, and a control terminal responsive to a first control signal for coupling said first terminal to said second terminal in response to a first state of said first control signal and for uncoupling said first terminal from said second terminal in response to a second state of said first control signal;

at least one second switching means having a first terminal coupled to said second terminal of said at least one inductance, a second terminal coupled to said power bus, and a control terminal responsive to a second control signal for coupling said first terminal to said second terminal in response to said first state of said second control signal and for uncoupling said first terminal from said second terminal in response to said second state of said second control signal; and

a control circuit having a first input terminal for inputting a first signal that indicates a magnitude of a voltage potential between said power bus and said common bus, said control circuit having a second input terminal for inputting a second signal that indicates a magnitude of a reference voltage potential, said control circuit having a third input terminal for inputting a third signal that indicates a magnitude of a current flow through said first switching means, said control circuit having an output terminal for outputting a single control signal having a pulse width set in accordance with said first signal, said second signal, and said third signal for controlling both the magnitude and the direction of the current flow through said at least one inductance to maintain the magnitude of the voltage potential of said power bus at a magnitude specified by said second signal;

wherein said single control signal is coupled to said control terminal of one of said first switching means and said second switching means, and wherein an inverse of said single control signal is coupled to said control terminal of the other one of said first switching means and said second switching means.

2. A bilateral power converter system as set forth in claim 1 wherein there are at least two of said power conversion units, and further comprising:

multiplier means having a first input terminal coupled to said third signal and a second input terminal coupled to a predetermined current proportionality signal, said multiplier means having an output terminal coupled to a fourth input terminal of said control circuit for outputting thereto a signal that is indicative of a product of said third signal and said predetermined current proportionality signal, and wherein

said control circuit outputs said single control signal to have a pulse width set in accordance with said first signal, said second signal, said third signal, and also said output of said multiplier means for maintaining the magnitude of the current flow through said at least one inductance at a level indicated by said predetermined current proportionality signal, wherein said predetermined current proportionality signal specifies a ratio of currents to be supplied by individual ones of said at least two power conversion units.

3. A bilateral power converter system as set forth in claim 1 wherein said at least one power conversion unit further comprises:

means for sensing the magnitude of the current flow through said at least one inductance, said sensing means having an output; and

first comparing means having a first input coupled to said output of said sensing means and a second input coupled to an input signal that specifies a maximum magnitude of a current flow through said at least one inductance, said first comparing means having an output coupled to said control circuit, and wherein said control circuit is responsive to said output of said first comparing means for selectively limiting the current flow through said at least one inductance in accordance therewith.

4. A bilateral power converter system as set forth in claim 1 wherein said at least one power conversion unit further comprises:

second comparing means for comparing said first signal to said second signal, said second comparing means having an output signal for indicating a difference between (a) the magnitude of the voltage potential between said power bus and said common bus and (b) the magnitude of a reference voltage potential, said output of said second comparing means being coupled to said output of said first comparing means at a power conversion unit voltage control node;

wherein

said bilateral power conversion system is comprised of a plurality of said power conversion units;

wherein

said power conversion unit voltage control node of each of said power conversion units is coupled in common to said power conversion unit voltage control node of each of said plurality of power conversion units; and

wherein

the duty cycle of said control signal output from each of said control units of each of said plurality of power conversion units is set in accordance with a power conversion unit voltage control node that has a greatest magnitude.

5. A bilateral power converter system for use on a space-based platform having a battery and a solar panel, said converter system comprising at least one bilateral power conversion unit, said at least one power conversion unit comprising:

at least one inductance having a first terminal and a second terminal, said first terminal for coupling to a first terminal of said battery;

a common bus for coupling to a second terminal of said battery;

a power bus for coupling to an output of said solar panel;

a capacitance coupled between said power bus and said common bus;

at least one first switching means having a first terminal coupled to said second terminal of said at least one inductance, a second terminal coupled to said common bus, and a control terminal responsive to a first control signal for coupling said first terminal to said second terminal in response to a first state of said first control signal and for uncoupling said first terminal from said second terminal in response to a second state of said first control signal;

at least one second switching means having a first terminal coupled to said second terminal of said at least one inductance, a second terminal coupled to said power bus, and a control terminal responsive to a second control signal for coupling said first terminal to said second terminal in response to said first state of said second control signal and for uncoupling said first terminal from said second terminal in response to said second state of said second control signal; and

a control circuit having a first input terminal for inputting a first signal that indicates a magnitude of a voltage potential between said power bus and said common bus, said control circuit having a second input terminal for inputting a second signal that indicates a magnitude of a reference voltage potential, said control circuit having a third input terminal for inputting a third signal that indicates a magnitude of a current flow through said at least one first switching means, said control circuit having an output terminal for outputting a single control signal having a pulse width set in accordance with said first signal, said second signal, and said third signal for controlling the magnitude and the direction of the current flow through said at least one inductance to maintain the magnitude of the voltage potential of said power bus at a magnitude specified by said second signal;

wherein said single control signal is coupled to said control terminal of one of said at least one first switching means and said at least one second switching means,

and wherein an inverse of said single control signal is coupled to said control terminal of the other one of said at least one first switching means and said at least one second switching means.

6. A bilateral power converter system as set forth in claim 5 wherein there are at least two of said power conversion units, and further comprising:

multiplier means having a first input terminal coupled to said third signal and a second input terminal coupled to a predetermined current proportionality signal, said multiplier means having an output terminal coupled to a fourth input terminal of said control circuit for outputting thereto a signal that is indicative of a product of said third signal and said predetermined current proportionality signal, and wherein

said control circuit outputs said single control signal to have a pulse width set in accordance with said first signal, said second signal, said third signal, and also said output of said multiplier means for maintaining the magnitude of the current flow to or from said battery at a level indicated by said predetermined current proportionality signal, wherein said predetermined current proportionality signal specifies a ratio of currents to be supplied by individual ones of said at least two power conversion units.

7. A bilateral power converter system as set forth in claim 5 wherein said at least one power conversion unit further comprises:

means for sensing the magnitude of the current flow to or from said battery, said sensing means having an output; and

first comparing means having a first input coupled to said output of said sensing means and a second input coupled to an input signal that specifies a maximum magnitude of a battery charging current, said first comparing means having an output coupled to said control circuit, and wherein said control circuit is responsive to said output of said first comparing means for selectively limiting said battery charging current in accordance therewith.

8. A bilateral power converter system as set forth in claim 5 wherein said at least one power conversion unit further comprises:

second comparing means for comparing said first signal to said second signal, said second comparing means having an output signal for indicating a difference between (a) the magnitude of the voltage potential between said power bus and said common bus and (b) the magnitude of a reference voltage potential, said output of said second comparing means being coupled to said output of said first comparing means at a power conversion unit voltage control node;

wherein

said bilateral power conversion system is comprised of a plurality of said power conversion units, each having an associated battery that is charged or discharged therefrom;

wherein

said power conversion unit voltage control node of each of said power conversion units is coupled in common to said power conversion unit voltage control node of each of said plurality of power conversion units; and

wherein

the duty cycle of said control signal output from each of said control units of each of said plurality of power conversion units is set in accordance with a power conversion unit voltage control node that has a greatest magnitude.

9. A method for operating a bilateral power converter system for use on a space-based platform comprised of a solar panel having an output coupled to a power bus, the converter system comprising at least two bilateral power conversion units that are coupled to a first terminal of an inductance and, through the inductance, to a battery having a first terminal coupled to a second terminal of the inductance and a second terminal coupled to a common bus, the method operating each one of the bilateral power conversion units by the steps of:

comparing a signal indicating a magnitude of a voltage potential between the power bus and the common bus to a signal indicating a reference voltage potential to obtain a first difference signal;

sensing a total current flowing through the power bus to generate a sensed current signal;

comparing the sensed current signal to a signal indicating a reference battery charging current signal to obtain a second difference signal;

selecting a largest one of the first difference signal and the second difference signal to provide a voltage control signal;

multiplying the sensed current signal times a signal indicating a proportion of a total current to be provided by one of at least two bilateral power conversion units to provide a first current control signal;

sensing a peak current flowing through the bilateral power conversion unit to generate a sensed peak current signal;

adding the sensed peak current signal to the first current control signal to generate a second current control signal;

combining the second current control signal with the voltage control signal and varying the output of a pulse width modulator in accordance with the combined signal to generate a pulse width modulated switching signal;

driving a first switching transistor with a first version of the pulse width modulated switching signal, the first switching transistor being coupled between the power bus and the first terminal of the inductance; and

simultaneously driving a second switching transistor with a second, inverted version of the pulse width modulated switching signal, the second switching transistor being coupled between the first terminal of the inductance and the common bus.

10. A method as set forth in claim 9 wherein each of said at least two bilateral power conversion units has an associated battery that is charged or discharged therefrom, and further including the steps of:

coupling together in common the voltage control signal from each of the power conversion units; and

varying the output of the pulse width modulator in accordance with a largest one of the voltage control signals to generate the pulse width modulated switching signal.

11. A bilateral power converter system for use on a space-based platform comprised of a solar panel having an output coupled to a power bus, comprising:

at least two bilateral power conversion units each of which is coupled to a first terminal of an inductance and, through said inductance, to a battery having a first terminal coupled to a second terminal of said inductance and a second terminal coupled to a common bus;

each of said bilateral power conversion units further comprising,

a first switching transistor coupled between said power bus and said first terminal of said inductance;

a second switching transistor coupled between said first terminal of said inductance and said common bus;

means for comparing a signal indicating a magnitude of a voltage potential between said power bus and said common bus to a signal indicating a reference voltage potential to obtain a first difference signal;

means for sensing a total current flowing through the power bus to generate a sensed current signal;

means for comparing said sensed current signal to a signal indicating a reference battery charging current signal to obtain a second difference signal;

means for selecting a largest one of said first difference signal and said second difference signal to provide a voltage control signal;

means for multiplying said sensed current signal times a signal indicating a proportion of a total current to be provided by said bilateral power conversion unit to provide an first current control signal;

means for sensing a peak current flowing through said bilateral power conversion unit to generate a sensed peak current signal;

means for adding said sensed peak current signal to said first current control signal to generate a second current control signal;

means for combining said second current control signal with said voltage control signal;

means for varying an output of a pulse width modulator in accordance with said combined signal to generate a single pulse width modulated switching signal;

means for driving said first switching transistor with a first version of said single pulse width modulated switching signal, said first switching transistor being coupled between said power bus and said first terminal of said inductance; and

means for simultaneously driving said second switching transistor with a second version of said single pulse width modulated switching signal, said second switching transistor being coupled between said first terminal of said inductance and said common bus, wherein said second version is the inverse of said first version.

12. A system as set forth in claim 11 wherein each of said at least two bilateral power conversion units has an associated battery that is charged or discharged therefrom, and further comprising:

means for coupling together in common said voltage control signal from each of said power conversion units; and

wherein

said means for varying said output of said pulse width modulator is responsive to a largest one of said voltage control signals to generate said pulse width modulated switching signal in accordance therewith.

13. A system as set forth in claim 11 wherein each of said at least two bilateral power conversion units includes a plurality of pairs of said first and second switching transistors, and further comprising:

means for generating a synchronizing clock signal for use in driving said plurality of pairs of switching transistors; and

means for delaying said synchronizing clock signal to provide a plurality of phases thereof, each of the phases being used for driving one of the plurality of pairs of switching transistors.

14. A system as set forth in claim 13 wherein there are n pairs of said switching transistors and wherein a phase delay between said plurality of phases is 360°

/n, whereby a ripple amplitude is reduced and a ripple frequency is increased for power flowing through said power bus.