Drive signal modulation method of modular multilevel converter and fault isolation method

• US 10,224,833 B2
• Filed: 07/13/2016
• Issued: 03/05/2019
• Est. Priority Date: 07/01/2015
• Status: Active Grant

• Current Assignee: NR Electric Co., Ltd., Nr Engineering Co.,Ltd.
• Original Assignee: NR Electric Co., Ltd., Nr Engineering Co.,Ltd.
• Inventors: Xie, Yeyuan, Cao, Dongming, Jiang, Tiangui, Zhu, Minglian, Yin, Guanxian
• Primary Examiner(s): Kinkead, Arnold
• Application Number:
  US15/579,935
• Publication Number:
  US 20180226900A1
• Time in Patent Office: 965 Days
• Field of Search: 363 5602, 363 65, 363 78, 318701
• CPC Class Codes: G06F 13/00 Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units interface circuits for specific input/output devices G06F3/00 ; multiprogram control therefor G06F9/46; multiprocessor systems G06F15/16
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/325 with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
• CPC Class Codes: H02M 1/327 against abnormal temperatures
• CPC Class Codes: H02M 3/137 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/139 with digital control
• CPC Class Codes: H02M 7/00 Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
• CPC Class Codes: H02M 7/219 in a bridge configuration
• 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 7/5387 in a bridge configuration
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Disclosed are a modulation method of a modular multilevel converter and a fault isolation method of a submodule unit. The modulation method comprises a first mode and a second mode, and the first mode and the second mode operate cyclically. In the first mode, a first power semiconductor switch and a second power semiconductor switch are turned on alternately, while a third power semiconductor switch is turned off normally and a fourth power semiconductor switch is turned on normally. In the second mode, the third power semiconductor switch and the fourth power semiconductor switch are turned on alternately, while the first power semiconductor switch is turned on normally and the second power semiconductor switch is turned off normally. The method enables junction temperatures of the power semiconductor switches used to be equalized, increases an operation safety margin of the converter, effectively increase the capacity of the converter without increasing engineering costs, and achieve better performance in both economic efficiency and technicality.

Claims

1. A method of modulating a drive signal for a modular multilevel converter, the modular multilevel converter comprising at least one bridge arm, the bridge arm comprising at least one full-bridge submodule unit, the full-bridge submodule unit comprising a first power semiconductor switch, a second power semiconductor switch, a third power semiconductor switch and a fourth power semiconductor switch, the method comprising:

the full-bridge submodule unit operates in two alternate operation modes, designated a first mode and a second mode;

firstly enters the first mode, then enters the second mode, re-enters the first mode and so on;

or firstly enters the second mode, then enters the first mode, re-enters the second mode and so on;

in the first mode, an alternate drive signal is applied to the first power semiconductor switch and the second power semiconductor switch, such that the first power semiconductor switch and the second power semiconductor switch are turned on alternately in the same time sequence, while a complementary drive signal is applied to the third power semiconductor switch and the fourth power semiconductor switch, such that the third power semiconductor switch remains in an off state and the fourth power semiconductor switch remains in an on state in the time sequence of the alternate turning-on of the first power semiconductor switch and the second power semiconductor switch; and

in the second mode, an alternate drive signal is applied to the third power semiconductor switch and the fourth power semiconductor switch, such that the third power semiconductor switch and the fourth power semiconductor switch are turned on alternately in the same time sequence, while a complementary drive signal is applied to the first power semiconductor switch and the second power semiconductor switch, such that the first power semiconductor switch remains in an on state and the second power semiconductor switch remains in an off state in the time sequence of the alternate turning-on of the third power semiconductor switch and the fourth power semiconductor switch.

2. The method of modulating the drive signal for a modular multilevel converter of claim 1, wherein the first power semiconductor switch comprises a switching transistor T1 and a freewheel diode D1 in anti-parallel with the switching transistor T1;

the second power semiconductor switch comprises a switching transistor T2 and a freewheel diode D2 in anti-parallel with the switching transistor T2;

the third power semiconductor switch comprises a switching transistor T3 and a freewheel diode D3 in anti-parallel with the switching transistor T3; and

the fourth power semiconductor switch comprises a switching transistor T4 and a freewheel diode D4 in anti-parallel with the switching transistor T4.

3. The method of modulating a drive signal for a modular multilevel converter of claim 1, wherein each of the switching transistors T1, T2, T3, and T4 is an IGBT, an IGCT, a GTO, or a MOSFET.

4. The method of modulating a drive signal for a modular multilevel converter of claim 2, comprising the following steps:

1) a capacitor discharge state in the first mode;

an on-signal is applied to the switching transistors T1 and T4, an off-signal is applied to the switching transistors T2 and T3,

and the switching transistors T1 and T4 are turned on and an energy storage element C1 is discharged, at a forward current;

2) a forward bypass state in the first mode;

an on-signal is applied to the switching transistors T2 and T4, an off-signal is applied to the switching transistors T1 and T3, and the freewheel diode D2 and the switching transistor T4 are turned on and the full-bridge submodule unit is bypassed, at a forward current;

3) a capacitor discharge state in the first mode;

an on-signal is applied to the switching transistors T1 and T4, an off-signal is applied to the switching transistors T2 and T3, and the freewheel diodes D1 and D4 are turned on and the energy storage element C1 is charged, at a reverse current;

4) a reverse bypass state in the first mode;

an on-signal is applied to the switching transistors T2 and T4, an off-signal is applied to the switching transistors T1 and T3, and the switching transistor T2 and the freewheel diode D4 are turned on and the full-bridge submodule unit is bypassed, at a reverse current;

5) capacitor discharge state in the second mode;

an on-signal is applied to the switching transistors T1 and T4, an off-signal is applied to the switching transistors T2 and T3, and the switching transistors T1 and T4 are turned on and the energy storage element C1 is discharged, at a forward current;

6) a forward bypass state in the second mode;

an on-signal is applied to the switching transistors T1 and T3, an off-signal is applied to the switching transistors T2 and T4, and the switching transistor T1 and the freewheel diode D3 are turned on and the full-bridge submodule unit is bypassed, at a forward current;

7) a capacitor discharge state in the second mode;

an on-signal is applied to the switching transistors T1 and T4, an off-signal is applied to the switching transistors T2 and T3, and the freewheel diodes D1 and D4 are turned on and the energy storage element C1 is charged, at a reverse current; and

8) a reverse bypass state in the second mode;

an on-signal is applied to the switching transistors T1 and T3, an off-signal is applied to the switching transistors T2 and T4, and the freewheel diode D1 and the switching transistor T3 are turned on and the full-bridge submodule unit is bypassed, at a reverse current.

5. A method of isolating a fault of a submodule unit, wherein the submodule unit is the at least one full-bridge submodule unit, the method comprising:

when the method of modulating a drive signal for a modular multilevel converter of claim 1 is used to perform modulation, if a second power semiconductor switch or a third power semiconductor switch in the at least one full-bridge submodule unit breaks down or if a drive circuit of the second power semiconductor switch or the third power semiconductor switch breaks down, the broken-down power semiconductor switch is isolated by changing the mode of the drive signal modulation, while the at least one full-bridge submodule unit does not stop operating.

6. The method of modulating a drive signal for a modular multilevel converter of claim 2, wherein each of the switching transistors T1, T2, T3, and T4 is an IGBT, an IGCT, a GTO, or a MOSFET.

7. A method of isolating a fault of a submodule unit, the submodule unit is the at least one full-bridge submodule unit, the method comprising:

when the method of modulating a drive signal for a modular multilevel converter of claim 2 is used to perform modulation, if a second power semiconductor switch or a third power semiconductor switch in the at least one full-bridge submodule unit breaks down or if a drive circuit of the second power semiconductor switch or the third power semiconductor switch breaks down, the broken-down power semiconductor switch is isolated by changing the mode of the drive signal modulation, while the at least one full-bridge submodule unit does not stop operating.

8. A method of isolating a fault of a submodule unit, the submodule unit is the at least one full-bridge submodule unit, the method comprising:

when the drive signal modulation method of a modular multilevel converter of claim 3 is used to perform modulation, if a second power semiconductor switch or a third power semiconductor switch in the at least one full-bridge submodule unit breaks down or if a drive circuit of the second power semiconductor switch or the third power semiconductor switch breaks down, the broken-down power semiconductor switch is isolated by changing the mode of the drive signal modulation, while the at least one full-bridge submodule unit does not stop operating.

9. A method of isolating a fault of a submodule unit, the submodule unit is at least one full-bridge submodule unit, the method comprising:

when the drive signal modulation method of a modular multilevel converter of claim 4 is used to perform modulation, if a second power semiconductor switch or a third power semiconductor switch in the at least one full-bridge submodule unit breaks down or if a drive circuit of the second power semiconductor switch or the third power semiconductor switch breaks down, the broken-down power semiconductor switch is isolated by changing the mode of the drive signal modulation, while the at least one full-bridge submodule unit does not stop operating.

10. A method of isolating a fault of a submodule unit, the submodule unit is the at least one full-bridge submodule unit, the method comprising:

when the drive signal modulation method of a modular multilevel converter of claim 6 is used to perform modulation, if a second power semiconductor switch or a third power semiconductor switch in the at least one full-bridge submodule unit breaks down or if a drive circuit of the second power semiconductor switch or the third power semiconductor switch breaks down, the broken-down power semiconductor switch is isolated by changing the mode of the drive signal modulation, while the at least one full-bridge submodule unit does not stop operating.