Multi-level inverter

• US 10,680,505 B2
• Filed: 06/14/2019
• Issued: 06/09/2020
• Est. Priority Date: 03/26/2014
• Status: Active Grant

• Current Assignee: Solaredge Technologies Incorporated
• Original Assignee: Solaredge Technologies Incorporated
• Inventors: Yoscovich, Ilan, Glovinsky, Tzachi, Sella, Guy, Galin, Yoav
• Primary Examiner(s): Laxton, Gary L
• Assistant Examiner(s): Jackson, Lakaisha
• Application Number:
  US16/442,161
• Publication Number:
  US 20190296633A1
• Time in Patent Office: 361 Days
• CPC Class Codes: H02M 1/0054 Transistor switching losses periodically suspending operation of switching converter in low power mode H02M1/0035
• CPC Class Codes: H02M 1/0095 Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/143 using compensating arrangements for reducing noise from the supply in transmission systems H04B15/005
• CPC Class Codes: H02M 7/483 Converters with outputs that each can have more than two voltages levels
• CPC Class Codes: H02M 7/4833 Capacitor voltage balancing
• CPC Class Codes: H02M 7/4835 comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
• CPC Class Codes: H02M 7/4837 Flying capacitor converters
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters

Abstract

A multi-level inverter having one or more banks, each bank containing a plurality of low voltage MOSFET transistors. A processor configured to switch the plurality of low voltage MOSFET transistors in each bank to switch at multiple times during each cycle.

Claims

1. An inverter comprising:

first and second DC terminals configured to receive a DC voltage;

first and second AC terminals configured to output an AC voltage at a first frequency;

a first flying capacitor circuit comprising first and second voltage inputs, and a first voltage output coupled to the first AC terminal;

a second flying capacitor circuit comprising third and fourth voltage inputs, and a second voltage output coupled to the second AC terminal; and

a switching circuit having a first plurality of switches configured to operate at the first frequency and a second plurality of switches configured to operate at the first frequency;

wherein;

during a first half cycle of the AC voltage, the first plurality of switches is configured to connect the first DC terminal to the first voltage input, the second DC terminal to the fourth voltage input, and the second voltage input to the third voltage input; and

during a second half cycle of the AC voltage, the second plurality of switches is configured to connect the first DC terminal to the third voltage input, the second DC terminal to the second voltage input, and the fourth voltage input to the first voltage input.

2. The inverter of claim 1, wherein the switching circuit is configured to switch the first plurality of switches substantially complimentary to switching the second plurality of switches at the first frequency.

3. The inverter of claim 2, wherein the first plurality of switches is configured to connect and disconnect the second voltage input to the third voltage input with mutual dead time to the second plurality of switches being configured to connect and disconnect the fourth voltage input to the first voltage input.

4. The inverter of claim 1, wherein:

the second plurality of switches comprises a first switch connected between an intersection point and the first voltage input, and a fourth switch connected between the intersection point and the fourth voltage input; and

the first plurality of switches comprises a second switch connected between the intersection point and the second voltage input, and a third switch connected between the intersection point and the third voltage input.

5. The inverter of claim 1, wherein:

the first plurality of switches comprises at least one first switch connected between the second voltage input and the third voltage input; and

the second plurality of switches comprises at least one second switch connected between the fourth voltage input and the first voltage input.

6. The inverter of claim 1, wherein:

the first plurality of switches and the second plurality of switches comprise a first switch connected between the first DC terminal and the first voltage input, a second switch connected between the second DC terminal and the second voltage input, a third switch connected between the first DC terminal and the third voltage input, and a fourth switch connected between the second DC terminal and the fourth voltage input; and

the inverter further comprises a controller configured to control the first switch and the fourth switch to be on during the first half cycle and to be off during the second half cycle, and the second switch and the third switch to be off during the first half cycle and to be on during the second half cycle.

7. The inverter of claim 1, further comprising:

a first inductor connected between the first voltage output and the first AC terminal; and

a second inductor connected between the second voltage output and the second AC terminal.

8. The inverter of claim 7, wherein:

the inverter is configured to generate a first sine wave voltage on the first AC terminal and a second sine wave voltage on the second AC terminal;

the first sine wave voltage is 180 degrees phase shifted from the second sine wave voltage; and

the AC voltage is output as a difference between the first and the second sine wave voltages.

9. The inverter of claim 1, wherein the first plurality of switches and the second plurality of switches are configured to share current between the first flying capacitor circuit and the second flying capacitor circuit such that ripple voltage is removed across the first and the second voltage inputs and removed across the third and the fourth voltage inputs.

10. The inverter of claim 9, wherein:

the first flying capacitor circuit comprises a third plurality of switches, the second flying capacitor circuit comprises a fourth plurality of switches, and the third plurality of switches and the fourth plurality of switches are configured to switch at a second frequency that is greater than the first frequency; and

a first connection made by the first plurality of switches between the second and the third voltage inputs, and a second connection made by the second plurality of switches between the fourth and the first voltage inputs are configured to filter current at the second frequency from flowing between the first and the second flying capacitor circuits.

11. The inverter of claim 1, further comprising a controller, wherein:

the first flying capacitor circuit comprises a third plurality of switches, the second flying capacitor circuit comprises a fourth plurality of switches, and the third plurality of switches corresponds one-to-one with the fourth plurality of switches; and

the controller is configured to switch the third plurality of switches and the fourth plurality of switches at a second frequency that is greater than the first frequency such that, during each cycle of the second frequency, each switch of the third plurality of switches turns on and off in a complementary manner to its corresponding switch of the fourth plurality of switches.

12. The inverter of claim 1, further comprising a controller, wherein:

the first flying capacitor circuit comprises a third plurality of switches, and the second flying capacitor circuit comprises a fourth plurality of switches; and

during the first and the second half cycles of the AC voltage, the controller is configured to switch the third plurality of switches and the fourth plurality of switches at a second frequency that is greater than the first frequency and that is greater than 16 kHz.

13. The inverter of claim 12, wherein the first frequency is 50 Hz or 60 Hz.

14. A method comprising:

generating an AC voltage at a first frequency with an inverter comprising first and second DC terminals, first and second AC terminals, a switching circuit having a first plurality of switches and a second plurality of switches, a first flying capacitor circuit having first and second voltage inputs and a first voltage output coupled to the first AC terminal, and a second flying capacitor circuit having third and fourth voltage inputs and a second voltage output coupled to the second AC terminal;

wherein the generating comprises;

receiving a DC voltage across the first and the second DC terminals; and

switching the first plurality of switches and the second plurality of switches at the first frequency, including;

a) closing, during first half cycles of the AC voltage, the first plurality of switches to connect the first DC terminal to the first voltage input, the second DC terminal to the fourth voltage input, and the second voltage input to the third voltage input; and

b) closing, during second half cycles of the AC voltage, the second plurality of switches to connect the first DC terminal to the third voltage input, the second DC terminal to the second voltage input, and the fourth voltage input to the first voltage input.

15. The method of claim 14, further comprising switching the first plurality of switches substantially complimentary to switching the second plurality of switches at the first frequency.

16. The method of claim 15, wherein the switching of the first plurality of switches substantially complimentary to the switching of the second plurality of switches at the first frequency comprises connecting and disconnecting the second voltage input to the third voltage input with mutual dead time to connecting and disconnecting of the fourth voltage input to the first voltage input.

17. The method of claim 14, wherein:

the second plurality of switches comprise a first switch connected between an intersection point and the first voltage input, and a fourth switch connected between the intersection point and the fourth voltage input; and

the first plurality of switches comprise a second switch connected between the intersection point and the second voltage input, and a third switch connected between the intersection point and the third voltage input.

18. The method of claim 14, wherein:

the first plurality of switches comprises at least one first switch connected between the second voltage input and the third voltage input; and

the second plurality of switches comprises at least one second switch connected serially between the fourth voltage input and the first voltage input.

19. The method of claim 14, further comprising:

generating, with the first flying capacitor circuit, a first pulse width modulated voltage on the first voltage output;

generating, with the second flying capacitor circuit, a second pulse width modulated voltage on the second voltage output;

filtering the first pulse width modulated voltage to generate a first sine wave voltage at the first frequency on the first AC terminal;

filtering the second pulse width modulated voltage to generate a second sine wave voltage at the first frequency on the second AC terminal;

wherein the first sine wave voltage is 180 degrees phase shifted from the second sine wave voltage.

20. The method of claim 14, further comprising conducting current from the second voltage input to the third voltage input during the first half cycles, and current from the fourth voltage input to the first voltage input during the second half cycles, such that ripple voltage at the first frequency is removed across the first and the second voltage inputs, and removed across the third and the fourth voltage inputs.

21. The method of claim 20, further comprising:

switching, at a second frequency that is greater than the first frequency, a third plurality of switches in the first flying capacitor circuit and a fourth plurality of switches in the second flying capacitor circuit; and

filtering current at the second frequency from flowing between the first flying capacitor circuit and the second flying capacitor circuit.

22. The method of claim 14, wherein the first flying capacitor circuit comprises a third plurality of switches, the second flying capacitor circuit comprises a fourth plurality of switches, the third plurality of switches correspond one-to-one with the fourth plurality of switches, and the method further comprises:

switching each switch of the third plurality of switches in a complementary manner to its corresponding switch in the fourth plurality of switches.

23. The method of claim 14, wherein the first flying capacitor circuit comprises a third plurality of switches and the second flying capacitor circuit comprises a fourth plurality of switches, and the method further comprises:

switching on and off the third plurality of switches and the fourth plurality of switches at a second frequency that is greater than the first frequency and that is greater than 16 kHz.

24. The method of claim 23, wherein the first frequency is 50 Hz or 60 Hz.

25. An inverter comprising:

first and second DC terminals configured to receive a DC voltage;

first and second AC terminals configured to output an AC voltage at a first frequency;

a first flying capacitor circuit comprising first and second voltage inputs, and a first voltage output coupled to the first AC terminal;

a second flying capacitor circuit comprising third and fourth voltage inputs, and a second voltage output coupled to the second AC terminal;

a first plurality of switches configured to switch at the first frequency, including closing during first half cycles of the AC voltage to connect the first DC terminal to the first voltage input, the second DC terminal to the fourth voltage input, and the second voltage input to the third voltage input; and

a second plurality of switches configured to switch at the first frequency, including closing during second half cycles of the AC voltage to connect the first DC terminal to the third voltage input, the second DC terminal to the second voltage input, and the fourth voltage input to the first voltage input;

wherein, during outputting of the AC voltage;

the first plurality of switches is configured to open whenever the first DC terminal is connected to the third voltage input, and the second plurality of switches is configured to open whenever the first DC terminal is connected to the first voltage input.

26. The inverter of claim 25, wherein:

the first flying capacitor circuit comprises a third plurality of switches, the second flying capacitor circuit comprises a fourth plurality of switches, and the third plurality of switches correspond one-to-one with the fourth plurality of switches; and

the inverter further comprises a controller configured to switch the third plurality of switches and the fourth plurality of switches at a second frequency that is greater than the first frequency such that, during each cycle of the second frequency, each switch of the third plurality of switches turns on and off in a complementary manner to its corresponding switch in the fourth plurality of switches.

27. The inverter of claim 26, wherein the second frequency is greater than 16 kHz, and the first frequency is 50 Hz or 60 Hz.

28. A method comprising:

generating an AC voltage at a first frequency with an inverter comprising first and second DC terminals, first and second AC terminals, a switching circuit having a first plurality of switches and a second plurality of switches, a first flying capacitor circuit having first and second voltage inputs and a first voltage output coupled to the first AC terminal, and a second flying capacitor circuit having third and fourth voltage inputs and a second voltage output coupled to the second AC terminal;

wherein the generating comprises;

receiving a DC voltage across the first and the second DC terminals; and

switching the first plurality of switches and the second plurality of switches at the first frequency, including;

a) closing, during first half cycles of the AC voltage, the first plurality of switches to connect the first DC terminal to the first voltage input, the second DC terminal to the fourth voltage input, and the second voltage input to the third voltage input; and

b) closing, during second half cycles of the AC voltage, the second plurality of switches to connect the first DC terminal to the third voltage input, the second DC terminal to the second voltage input, and the fourth voltage input to the first voltage input;

c) opening, during the generating of the AC voltage, each switch of the first plurality of switches whenever the first DC terminal is connected to the third voltage input; and

d) opening, during the generating of the AC voltage, each switch of the second plurality of switches whenever the first DC terminal is connected to the first voltage input.

29. The method of claim 28, wherein the first flying capacitor circuit comprises a third plurality of switches, the second flying capacitor circuit comprises a fourth plurality of switches, the third plurality of switches correspond one-to-one with the fourth plurality of switches, and the method further comprises:

switching the third plurality of switches and the fourth plurality of switches at a second frequency that is greater than the first frequency, including switching each switch of the third plurality of switches in a complementary manner to its corresponding switch in the fourth plurality of switches.

30. The method of claim 29, wherein the second frequency is greater than 16 kHz, and the first frequency is 50 Hz or 60 Hz.