Parallel power supply device

• US 10,742,128 B2
• Filed: 03/15/2017
• Issued: 08/11/2020
• Est. Priority Date: 06/30/2016
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Higaki, Yusuke, Kondo, Ryota
• Primary Examiner(s): Barnie, Rexford N
• Assistant Examiner(s): Emeaba, Kalu Kelly
• Application Number:
  US16/094,977
• Publication Number:
  US 20190157979A1
• Time in Patent Office: 1,245 Days
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 1/106 for load balancing, symmetrisation, or sharing
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
• CPC Class Codes: H02M 3/33584 Bidirectional converters
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel

Abstract

A parallel power supply device includes a plurality of DC/DC converters connected in parallel, and each DC/DC converter includes: first and second switching circuits with a transformer therebetween; first and second reactors; and a control circuit. The control circuit generates a duty cycle so that a deviation between voltage of a load and target voltage becomes 0. Correction is performed such that, when the magnitude of the duty cycle is smaller than a set value Vth, the magnitude is fixed at 0, and otherwise, the magnitude is decreased by the set value Vth. Then, the phase shift amounts for drive signals for the first and second switching circuits are determined, and the first and second switching circuits are subjected to phase shift control.

Claims

1. A parallel power supply device in which a plurality of DC/DC converters each performing bidirectional power transmission are connected in parallel to supply power to a common load, each DC/DC converter comprising:

a transformer;

a first switching circuit configured to be a full-bridge circuit with two bridge circuits having a plurality of semiconductor switching elements to which diodes are respectively connected in antiparallel, the first switching circuit being connected between the common load and a first winding of the transformer and performing power conversion between DC and AC;

a second switching circuit configured to be a full-bridge circuit with two bridge circuits having a plurality of semiconductor switching elements to which diodes are respectively connected in antiparallel, the second switching circuit being connected between a DC power supply and a second winding of the transformer and performing power conversion between DC and AC;

a first reactor and a second reactor connected to AC input/output lines of the first switching circuit and the second switching circuit, respectively; and

a control circuit for controlling the first switching circuit and the second switching circuit, wherein

each control circuit includes a voltage control unit having a compensator and generating a duty cycle so that a deviation between voltage of the common load and target voltage becomes 0, and on the basis of the duty cycle, the control circuit determines first and second phase shift amounts for drive signals for the first and second switching circuits, to control the first and second switching circuits, and

each control circuit uses the duty cycle corrected such that, when a magnitude of the duty cycle generated by the voltage control unit is smaller than a set value, the magnitude is fixed at 0, and otherwise, the magnitude is decreased by the set value.

2. The parallel power supply device according to claim 1, wherein the voltage control unit in each control circuit includes:

a first compensator and a second compensator as the compensator;

a voltage control circuit for generating target current so that the deviation between the voltage of the common load and the target voltage becomes 0 by the first compensator; and

a current control circuit for generating the duty cycle so that a deviation between the target current and current between the second switching circuit and the DC power supply becomes 0 by the second compensator.

3. The parallel power supply device according to claim 1, wherein

capacitors are connected in parallel to the respective semiconductor switching elements in the first and second switching circuits so as to allow the semiconductor switching elements to perform zero voltage switching.

4. The parallel power supply device according to claim 1, wherein

one of the semiconductor switching elements in each of the first and second switching circuits is defined as a reference element, and one of the semiconductor switching elements that is diagonal thereto in each of the first and second switching circuits is defined as a diagonal element, and

each control circuit determines, as the first and second phase shift amounts, phase differences of drive signals for the respective diagonal elements in the first and second switching circuits relative to phases of drive signals for the reference elements in a power-transmitting-side circuit of the first and second switching circuits.

5. The parallel power supply device according to claim 4, wherein

when the magnitude of the duty cycle generated by the voltage control unit is smaller than the set value, the control circuit fixes the first and second phase shift amounts at a maximum value.

6. The parallel power supply device according to claim 5, wherein

when the magnitude of the duty cycle is equal to or greater than the set value, the control circuit performs control such that, in a region not exceeding a reference point of the duty cycle at which the first and second phase shift amounts are both minimum, the first and second phase shift amounts are decreased by an equal amount as the magnitude of the duty cycle increases, and in a region where the magnitude of the duty cycle exceeds the reference point, one of the first and second phase shift amounts is kept minimum and the other one is increased as the magnitude of the duty cycle increases.

7. The parallel power supply device according to claim 1, wherein

the set value with respect to the magnitude of the duty cycle is determined on the basis of a detection error level of the voltage of the common load and a gain of the compensator.

8. The parallel power supply device according to claim 7, wherein

each control circuit adjusts the gain of the compensator in accordance with voltage of the DC power supply.

9. The parallel power supply device according to claim 1, wherein

of the plurality of DC/DC converters, two or more DC/DC converters are connected in common to the DC power supply.

10. The parallel power supply device according to claim 2, wherein

capacitors are connected in parallel to the respective semiconductor switching elements in the first and second switching circuits so as to allow the semiconductor switching elements to perform zero voltage switching.

11. The parallel power supply device according to claim 2, wherein

one of the semiconductor switching elements in each of the first and second switching circuits is defined as a reference element, and one of the semiconductor switching elements that is diagonal thereto in each of the first and second switching circuits is defined as a diagonal element, and

each control circuit determines, as the first and second phase shift amounts, phase differences of drive signals for the respective diagonal elements in the first and second switching circuits relative to phases of drive signals for the reference elements in a power-transmitting-side circuit of the first and second switching circuits.

12. The parallel power supply device according to claim 3, wherein

one of the semiconductor switching elements in each of the first and second switching circuits is defined as a reference element, and one of the semiconductor switching elements that is diagonal thereto in each of the first and second switching circuits is defined as a diagonal element, and

each control circuit determines, as the first and second phase shift amounts, phase differences of drive signals for the respective diagonal elements in the first and second switching circuits relative to phases of drive signals for the reference elements in a power-transmitting-side circuit of the first and second switching circuits.

13. The parallel power supply device according to claim 10, wherein

one of the semiconductor switching elements in each of the first and second switching circuits is defined as a reference element, and one of the semiconductor switching elements that is diagonal thereto in each of the first and second switching circuits is defined as a diagonal element, and

each control circuit determines, as the first and second phase shift amounts, phase differences of drive signals for the respective diagonal elements in the first and second switching circuits relative to phases of drive signals for the reference elements in a power-transmitting-side circuit of the first and second switching circuits.

14. The parallel power supply device according to claim 11, wherein

when the magnitude of the duty cycle generated by the voltage control unit is smaller than the set value, the control circuit fixes the first and second phase shift amounts at a maximum value.

15. The parallel power supply device according to claim 12, wherein

when the magnitude of the duty cycle generated by the voltage control unit is smaller than the set value, the control circuit fixes the first and second phase shift amounts at a maximum value.

16. The parallel power supply device according to claim 13, wherein

when the magnitude of the duty cycle generated by the voltage control unit is smaller than the set value, the control circuit fixes the first and second phase shift amounts at a maximum value.

17. The parallel power supply device according to claim 14, wherein

when the magnitude of the duty cycle is equal to or greater than the set value, the control circuit performs control such that, in a region not exceeding a reference point of the duty cycle at which the first and second phase shift amounts are both minimum, the first and second phase shift amounts are decreased by an equal amount as the magnitude of the duty cycle increases, and in a region where the magnitude of the duty cycle exceeds the reference point, one of the first and second phase shift amounts is kept minimum and the other one is increased as the magnitude of the duty cycle increases.

18. The parallel power supply device according to claim 15, wherein

when the magnitude of the duty cycle is equal to or greater than the set value, the control circuit performs control such that, in a region not exceeding a reference point of the duty cycle at which the first and second phase shift amounts are both minimum, the first and second phase shift amounts are decreased by an equal amount as the magnitude of the duty cycle increases, and in a region where the magnitude of the duty cycle exceeds the reference point, one of the first and second phase shift amounts is kept minimum and the other one is increased as the magnitude of the duty cycle increases.

19. The parallel power supply device according to claim 16, wherein

when the magnitude of the duty cycle is equal to or greater than the set value, the control circuit performs control such that, in a region not exceeding a reference point of the duty cycle at which the first and second phase shift amounts are both minimum, the first and second phase shift amounts are decreased by an equal amount as the magnitude of the duty cycle increases, and in a region where the magnitude of the duty cycle exceeds the reference point, one of the first and second phase shift amounts is kept minimum and the other one is increased as the magnitude of the duty cycle increases.

20. The parallel power supply device according to claim 2, wherein

the set value with respect to the magnitude of the duty cycle is determined on the basis of a detection error level of the voltage of the common load and a gain of the compensator.