Power conversion circuit for photovoltaic power generation with high efficiency over wide input voltage range

• US 10,476,398 B1
• Filed: 05/01/2018
• Issued: 11/12/2019
• Est. Priority Date: 05/01/2018
• Status: Active Grant

• Current Assignee: Postech Academy-Industry Foundation
• Original Assignee: Postech Academy-Industry Foundation
• Inventors: Kim, Minsung, Kim, Sooa, Kim, Bumyun
• Primary Examiner(s): Ahmed, Yusef A
• Assistant Examiner(s): Tiku, Sisay G
• Application Number:
  US15/968,644
• Publication Number:
  US 20190341855A1
• Time in Patent Office: 560 Days
• CPC Class Codes: H02M 1/0051 Diode reverse recovery losses
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H02M 7/219 in a bridge configuration
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

The present invention relates to a technique for expanding an input voltage range of a power conversion circuit for photovoltaic power generation, and improving the efficiency of the power conversion circuit.

The power conversion circuit for photovoltaic power generation with high efficiency over a wide input voltage range may include: a full-bridge converter unit including a full-bridge converter constituted by first to fourth switches, and configured to operate in a resonant boost mode or phase-shift full-bridge series-resonant converter mode, and convert an input DC voltage into a DC voltage having a level equal to or lower than the input DC voltage; an active voltage-doubler rectifier circuit including a half-bridge converter constituted by fifth and sixth switches, a resonance inductor and a resonance capacitor, and configured to boost an input voltage to a target-level DC voltage, and output the DC voltage to a load; and a transformer configured to connect the full-bridge converter and the active voltage-doubler rectifier to each other in their insulation.

Claims

1. A power conversion circuit for photovoltaic power generation with high efficiency over a wide input voltage range, comprising:

a full-bridge converter unit comprising a full-bridge converter constituted by first to fourth switches, and configured to operate in a resonant boost mode or a phase-shift full-bridge series-resonant converter mode based on an input voltage, and convert an input DC voltage into a DC voltage having a level equal to or lower than the input DC voltage;

an active voltage-doubler rectifier circuit comprising a half-bridge converter constituted by fifth and sixth switches, a resonance inductor and a resonance capacitor, and configured to boost a second input voltage to a target-level DC voltage, and output the target-level DC voltage to a load; and

a transformer configured to connect the full-bridge converter and the active voltage-doubler rectifier to each other in their insulation,

wherein the resonant boost mode includes a resonant boost state, and

wherein when the full-bridge converter unit operates in the resonant boost state, either

(a) the first and fourth switches are turned on, and the second and third switches and the fifth and sixth switches are turned off,

or

(b) the second and third switches are turned on, and the first and fourth switches and the fifth and sixth switches are turned off,

so that no power is transferred through the transformer.

2. The power conversion circuit of claim 1, wherein the full-bridge converter unit is configured to operate in the resonant boost mode when the input voltage lower than a reference voltage is received, or operate in the phase-shift full-bridge series-resonant converter mode when the input voltage higher than the reference voltage is received, wherein the reference voltage indicates the input voltage when the first and fourth switches and the second and third switches are complementarily switched with a maximum turn-on phase difference, such that a maximum voltage is outputted to a secondary coil of the transformer.

3. The power conversion circuit of claim 1, wherein the fifth and sixth switches are maintained in an off state when the full-bridge converter unit operates in the phase-shift full-bridge series-resonant converter mode.

4. The power conversion circuit of claim 1, wherein the fifth and sixth switches are complementarily switched with a maximum turn-on phase difference when the full-bridge converter unit operates in the resonant boost mode.

5. The power conversion circuit of claim 1, wherein the resonant boost mode is divided into first to eighth resonant boost modes.

6. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the first resonant boost mode,

the first and fourth switches and the sixth switch are turned on, and the second and third switches and the fifth switch are turned off, so that electrical energy stored in the resonance inductor rapidly increases, and power of a primary coil of the transformer is transferred to a secondary coil.

7. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the second resonant boost mode,

the first and fourth switches and a body diode of the fifth switch are maintained in an on state, and the second and third switches and the sixth switch are turned off, so that electrical energy stored in the resonance inductor is transferred toward the load through the body diode of the fifth switch.

8. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the third resonant boost mode, which corresponds to the resonant boost state,

the first and fourth switches are turned on, and the second and third switches and the fifth and sixth switches are turned off, so that no power is transferred through the transformer.

9. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the fourth resonant boost mode,

the first to sixth switches are all maintained in an off state, and a magnetizing current of a magnetizing inductor of the transformer operates as a current source, such that parasitic capacitors of the first and fourth switches are charged while parasitic capacitors of the second and third switches are discharged.

10. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the fifth resonant boost mode,

the second and third switches and the fifth switch are turned on, and the first and fourth switches and the sixth switch are turned off, so that electrical energy stored in the resonance inductor rapidly increases, and power of a primary coil of the transformer is transferred to a secondary coil.

11. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the sixth resonant boost mode,

the second and third switches and a body diode of the sixth switch are retained in a turn-on state, and the first and fourth switches and the fifth switch are turned off, so that electrical energy stored in the resonance inductor is transferred to the load through the body diode of the sixth switch.

12. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the seventh resonant boost mode, which corresponds to the resonant boost state,

the second and third switches are turned on, and the first and fourth switches and the fifth and sixth switches are turned off, so that no power is transferred through the transformer.

13. The power conversion circuit of claim 5, wherein when the full-bridge converter unit operates in the eighth resonant boost mode,

the first to sixth switches are all retained in an off state, and a magnetizing current of a magnetizing inductor of the transformer operates as a current source which charges parasitic capacitors of the second and third switches while discharging parasitic capacitors of the first and fourth switches.

14. The power conversion circuit of claim 5, wherein a magnetizing current of a magnetizing inductor of the transformer linearly increases when the full-bridge converter unit operates in the first to fourth resonant boost modes, and linearly decreases when the full-bridge converter unit operates in the fifth to eighth resonant boost modes.

15. The power conversion circuit of claim 1, wherein the full-bridge converter unit is configured to operate in the resonant boost mode or the phase-shift full-bridge series-resonant converter mode based on the input voltage in relation to a reference voltage.

16. The power conversion circuit of claim 1, wherein the full-bridge converter unit is configured to operate in the resonant boost mode when the input voltage lower than a reference voltage is received, or operate in the phase-shift full-bridge series-resonant converter mode when the input voltage higher than the reference voltage is received.

17. The power conversion circuit of claim 1, wherein the input voltage is the input DC voltage, and the second input voltage is a voltage inputted from the transformer.