Medium voltage variable frequency driving system

• US 8,811,048 B2
• Filed: 11/10/2011
• Issued: 08/19/2014
• Est. Priority Date: 09/13/2011
• Status: Active Grant

• Current Assignee: Delta Electronics Company Limited (Delta Electronics Incorporated)
• Original Assignee: Delta Electronics Company Limited (Delta Electronics Incorporated)
• Inventors: Zhang, Yi, Chen, Wei, Pu, Bo-Yu
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US13/293,757
• Publication Number:
  US 20130063070A1
• Time in Patent Office: 1,013 Days
• Field of Search: 363/34, 363/35, 363/37, 363/40, 363/41, 363/45, 363/67, 363/98
• US Class Current: 363/37
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H02P 27/14 with three or more levels of voltage

Abstract

The present invention provides a medium voltage variable frequency driving system, including a three-phase switch-mode rectification module, a multilevel inverter and a high-capacity capacitor module. The three-phase switch-mode rectification module is coupled with a three-phase electrical grid, for converting an AC voltage input with a fixed operating frequency on the three-phase electrical grid into a DC voltage. The multilevel inverter is used for converting the DC voltage into an AC voltage with a required variable frequency, so as to drive an induction motor. The high-capacity capacitor module is coupled between the three-phase switch-mode rectification module and the multilevel inverter, for temporarily storing the DC voltage. In the present invention, a three-phase switch-mode rectification technology is used at the front-end rectifier, and a diode-clamped three-level inverter is adapted correspondingly at the rear-end inverter.

Claims

1. A medium voltage variable frequency driving system coupled with a three-phase electrical grid for driving an induction motor, the medium voltage variable frequency driving system comprising:

a three-phase switch-mode rectification module coupled with the three-phase electrical grid for converting an alternating current voltage input with a fixed operating frequency on the three-phase electrical grid into a direct current voltage, wherein the three-phase switch-mode rectification module is a three-phase Vienna rectification module;

a multilevel inverter for converting the direct current voltage into alternating current voltage with a required variable frequency, wherein the alternating current voltage is used for driving the induction motor; and

a high-capacity capacitor module coupled between the three-phase switch-mode rectification module and the multilevel inverter, for temporarily storing the direct current voltage.

2. The medium voltage variable frequency driving system of claim 1, wherein the three-phase switch-mode rectification module comprises:

three single-phase rectification circuits, wherein the three single-phase rectification circuits are coupled in parallel with each other and form a three-level rectification circuit, the three single-phase rectification circuits respectively receive a single-phase voltage input from the three-phase electrical grid, all of the three single-phase rectification circuits are coupled to a first output terminal, a midpoint and a second output terminal, and the three-phase switch-mode rectification module is used for adjusting a power factor of the three-phase electrical grid and eliminating total current harmonic distortion of the three-phase electrical grid.

3. The medium voltage variable frequency driving system of claim 2, wherein an inductance is coupled between a voltage input terminal of each of the three single-phase rectification circuits and the three-phase electrical grid respectively.

4. The medium voltage variable frequency driving system of claim 3, wherein each of the three single-phase rectification circuits comprises at least two diodes, wherein one diode is a commutating diode for ensuring the unidirectivity of the current, and the other diode is a non-commutating diode.

5. The medium voltage variable frequency driving system of claim 4, wherein, in the three single-phase rectification circuits, the commutating diode operates at a switching frequency, and the commutating diode adopts a fast-recovery diode.

6. The medium voltage variable frequency driving system of claim 4, wherein each of the three single-phase rectification circuits respectively comprises:

a first diode, an anode of the first diode is coupled to the single-phase voltage input;

a second diode, an anode of the second diode is coupled to a cathode of the first diode, and a cathode of the second diode is coupled to the first output terminal;

a third diode, a cathode of the third diode is coupled to the single-phase voltage input;

a fourth diode, a cathode of the fourth diode is coupled to an anode of the third diode, and an anode of the fourth diode is coupled to the second output terminal;

a first switch, a first terminal of the first switch is coupled between the first diode and the second diode, and a second terminal of the first switch is coupled to the midpoint; and

a second switch, a first terminal of the second switch is coupled to the midpoint, and a second terminal of the second switch is coupled between the third diode and the fourth diode.

7. The medium voltage variable frequency driving system of claim 6, wherein the second diode and the fourth diode are commutating diodes and adopt fast-recovery diodes, and the first diode and the third diode are non-commutating diodes and adopt slow-recovery or fast-recovery diodes.

8. The medium voltage variable frequency driving system of claim 4, wherein each of the three single-phase rectification circuits respectively comprises:

a first diode, an anode of the first diode is coupled to the single-phase voltage input, and a cathode of the first diode is coupled to the first output terminal;

a second diode, an anode of the second diode is coupled to the single-phase voltage input;

a third diode, a cathode of the third diode is coupled to the single-phase voltage input, and an anode of the third diode is coupled to the second output terminal;

a fourth diode, a cathode of the fourth diode is coupled to the single-phase voltage input;

a first switch, a first terminal of the first switch is coupled to a cathode of the second diode, and a second terminal of the first switch is coupled to the midpoint; and

a second switch, a first terminal of the second switch is coupled to the midpoint, and a second terminal of the second switch is coupled to an anode of the fourth diode.

9. The medium voltage variable frequency driving system of claim 8, wherein the first diode and the third diode are commutating diodes and adopt fast-recovery diodes, and the second diode and the fourth diode are non-commutating diodes and adopt slow-recovery or fast-recovery diodes.

10. The medium voltage variable frequency driving system of claim 4, wherein each of the three single-phase rectification circuits respectively comprises:

a first diode, an anode of the first diode is coupled to the single-phase voltage input;

a second diode, an anode of the second diode is coupled to the midpoint;

a third diode, a cathode of the third diode is coupled to the first output terminal;

a fourth diode, a cathode of the fourth diode is coupled to the single-phase voltage input;

a fifth diode, a cathode of the fifth diode is coupled to the midpoint;

a sixth diode, an anode of the sixth diode is coupled to the second output terminal;

a switch, a first terminal of the switch is coupled between the cathode of the first diode, a cathode of the second diode and an anode of the third diode, and a second terminal of the switch is coupled between an anode of the fourth diode, an anode of the fifth diode and a cathode of the sixth diode.

11. The medium voltage variable frequency driving system of claim 10, wherein the third diode and the sixth diode are commutating diodes and adopt fast-recovery diodes, and the first diode, the second diode, the fourth diode and the fifth diode are non-commutating diodes and adopt slow-recovery or fast-recovery diodes.

12. The medium voltage variable frequency driving system of claim 4, wherein each of the three single-phase rectification circuits respectively comprises:

a first switch, a second terminal of the first switch is coupled to the single-phase voltage input;

a second switch, a first terminal of the second switch is coupled to the single-phase voltage input;

a first diode, an anode of the first diode is coupled to a first terminal of the first switch, and a cathode of the first diode is coupled to the first output terminal;

a second diode, an anode of the second diode is coupled to the midpoint, and a cathode of the second diode is coupled to the first terminal of the first switch;

a third diode, a cathode of the third diode is coupled to a second terminal of the second switch, and an anode of the third diode is coupled to the second output terminal; and

a fourth diode, an anode of the fourth diode is coupled to the second terminal of the second switch, and a cathode of the fourth diode is coupled to the midpoint.

13. The medium voltage variable frequency driving system of claim 12, wherein the first diode and the third diode are commutating diodes and adopt fast-recovery diodes, and the second diode and the fourth diode are non-commutating diodes and adopt slow-recovery or fast-recovery diodes.

14. The medium voltage variable frequency driving system of claim 2, wherein, in the multilevel inverter, by coupling the first output terminal, the midpoint and the second output terminal with the high-capacity capacitor module, the input from the three-phase electrical grid is converted into a required three-phase alternating current output through the multilevel inverter, so as to drive the induction motor.

15. The medium voltage variable frequency driving system of claim 14, wherein the multilevel inverter is a three-level inverter, and each single-phase three-level inverter at least comprises two switches and a clamping diode, wherein one terminal of the clamping diode is connected with the midpoint of the three-level rectification circuit, and the other terminal of the clamping diode is connected with the two switches.

16. The medium voltage variable frequency driving system of claim 2, wherein the high-capacity capacitor module comprises:

a first capacitor coupled between the first output terminal and the midpoint; and

a second capacitor coupled between the midpoint and the second output terminal.

17. The medium voltage variable frequency driving system of claim 1, wherein the alternating current voltage is a pulse-width modulation (PWM) square-wave alternating current signal, and the medium voltage variable frequency driving system further comprises at least one controller coupled with the multilevel inverter and the three-phase switch-mode rectification module, wherein the at least one controller is used for controlling the variable frequency, a pulse width or an amplitude of the pulse-width modulation square-wave alternating current signal, accordingly the controller is used for superimposing the pulse-width modulation square-wave alternating current signal into an alternating current output similar to a sinusoidal wave, so as to drive the induction motor.

18. The medium voltage variable frequency driving system of claim 17, wherein the controller of the medium voltage variable frequency driving system is used for controlling the variable frequency, the pulse width or the amplitude of the pulse-width modulation square-wave alternating current signal at the alternating current side of the rectification module, so as to control the power factor and the total harmonic distortion of the three-phase switch-mode rectification module, further to respectively achieve an appropriate value of the power factor and the total harmonic distortion.

19. The medium voltage variable frequency driving system of claim 18, wherein the controller of the medium voltage variable frequency driving system is a digital microprocessor.