Power conversion system and control method thereof

• US 9,843,278 B2
• Filed: 04/22/2015
• Issued: 12/12/2017
• Est. Priority Date: 11/28/2012
• Status: Active Grant

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Toba, Akio
• Primary Examiner(s): Ip, Paul
• Application Number:
  US14/693,281
• Publication Number:
  US 20150229252A1
• Time in Patent Office: 965 Days
• Field of Search: 318139, 31840004, 31840027, 318442, 363132, 307 91
• CPC Class Codes: H02M 1/0067 Converter structures employing plural converter units, other than for parallel operation of the units on a single load
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H02P 6/14 Electronic commutators

Abstract

Aspects of a power conversion system can include a capacitor which stores direct current power, an inverter, and a pair of direct current terminals of which are connected to two ends of the capacitor and to the alternating current terminals of which an alternating current motor acting as a load is connected. Also included can be an upper and lower arm portion of which the connection point of semiconductor switches connected in series is connected to the neutral point of the motor, a direct current power source connected in parallel to the upper and lower arm portion and a switch connected between one of the direct current terminals of the inverter and one end of the upper and lower arm portion. The other direct current terminal of the inverter can be connected to the other end of the upper and lower arm portion.

Claims

1. A power conversion system, comprising:

a power storage device which stores direct current power,

an inverter having a positive direct current terminal, a negative direct current terminal, and a plurality of alternating current terminals, the power storage device being connected between the positive direct current terminal and the negative direct current terminal, and a load having a leakage inductance being connected between the plurality of alternating current terminals;

a control circuit configured to turn switches included in the inverter on and off;

a first upper and lower arm portion, configured by connecting first and second semiconductor switches in series, the connection point of the first and second semiconductor switches being connected to a neutral point of the load; and

a direct current power source connected in parallel to the first upper and lower arm portion,

wherein at least one pair of homopolar terminals, among pairs of terminals of the positive and negative direct current terminals of the inverter and positive and negative terminals of the first upper and lower arm portion, are connected by a switch, and the other pair of homopolar terminals among the positive and negative direct current terminals of the inverter and the positive and negative terminals of the first upper and lower arm portion are set at the same potential,

wherein in a first case where the switch connecting the at least one pair of homopolar terminals is off, one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to a first end of the leakage inductance of the load, first switches included in the inverter are on, thereby equivalently configuring a first equivalent switch, in an on-state, connected to a second end of the leakage inductance of the load, and energy from the direct current power source is stored in the leakage inductance of the load; and

wherein in a second case where the switch connecting the at least one pair of homopolar terminals is off, the other one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to the first end of the leakage inductance of the load, second switches included in the inverter are on, thereby equivalently configuring a second equivalent switch, in an on-state, connected to the second end of the leakage inductance of the load, and energy stored in the leakage inductance of the load is supplied to the power storage device.

2. The power conversion system according to claim 1, wherein

only one pair of homopolar terminals, of pairs of homopolar terminals out of the positive and negative direct current terminals of the inverter and the positive and negative terminals of the first upper and lower arm portion, are connected by a switch, and the other pair of homopolar terminals are directly connected together.

3. The power conversion system according to claim 2, wherein

the switch connecting the at least one pair of homopolar terminals is turned off, the first and second switches of the inverter are turned on or off at the same time, thereby equivalently configuring a second upper and lower arm portion formed of a series circuit of the first equivalent switch and the second equivalent switch, and that the first and second semiconductor switches are turned on and off, thereby causing a buck-boost chopper formed of the first upper and lower arm portion, the second upper and lower arm portion, and the leakage inductance of the load to operate, thus charging and discharging the power storage device.

4. The power conversion system according to claim 3, wherein

a switching pattern of the inverter for carrying out a buck-boost operation by the second upper and lower arm portion configures one portion of a switching pattern for outputting an alternating current voltage from the inverter to drive the load.

5. The power conversion system according to claim 1, wherein

both pairs of homopolar terminals, of the positive and negative direct current terminals of the inverter and the positive and negative terminals of the first upper and lower arm portion, are connected by respective switches.

6. The power conversion system according to claim 5, wherein

in a condition in which one switch of the respective switches is constantly turned on, the other switch of the respective switches is turned off, and the first and second switches of the inverter are turned on or off at the same time, thereby equivalently configuring a second upper and lower arm portion formed of a series circuit of the first equivalent switch and the second equivalent switch, and that the first and second semiconductor switches are turned on and off, thereby causing a buck-boost chopper formed of the first upper and lower arm portion, the second upper and lower arm portion, and the leakage inductance of the load to operate, thus charging and discharging the power storage device.

7. The power conversion system according to claim 6, wherein

a switching pattern of the inverter for carrying out a buck-boost operation by the second upper and lower arm portion forms one portion of a switching pattern for outputting an alternating current voltage from the inverter to drive the load.

8. The power conversion system according to claim 1, wherein

semiconductor switches configuring the first and second switches of the inverter and the first and second semiconductor switches configuring the first upper and lower arm portion are each configured of a semiconductor switching element and a reflux diode connected in reverse parallel thereto.

9. The power conversion system according to claim 1, wherein

the load is an alternating current motor.

10. The power conversion system according to claim 1, wherein

the first and second switches of the inverter are configured by a plurality of semiconductor switches, and by switching the plurality of semiconductor switches in a condition in which the switch connecting the at least one pair of homopolar terminals is turned on and the first and second semiconductor switches are turned off, an alternating current voltage is output from the inverter to drive the load.

11. The power conversion system according to claim 10, wherein

a switching pattern of the inverter for carrying out a buck-boost operation by the second upper and lower arm portion configures one portion of a switching pattern for outputting an alternating current voltage from the inverter to drive the load.

12. The power conversion system according to claim 1, wherein in the second case where the switch connecting the at least one pair of homopolar terminals is off, the one of the first and second semiconductor switches included in the first upper and lower arm portion connected to the first end of the leakage inductance of the load is off, and the first switches included in the inverter are off, thereby placing the first equivalent switch connected to the second end of the leakage inductance of the load in an off-state.

13. The power conversion system according to claim 1, wherein in the second case where the switch connecting the at least one pair of homopolar terminals is off, the one of the first and second semiconductor switches included in the first upper and lower arm portion connected to the first end of the leakage inductance of the load is on, and the first switches included in the inverter are off, thereby placing the first equivalent switch connected to the second end of the leakage inductance of the load in an off-state.

14. A power conversion system, comprising:

a power storage device configured to store power;

an inverter having a positive direct current terminal, a negative direct current terminal, and a plurality of alternating current terminals, the power storage device being connected between the positive and negative direct current terminals, and the plurality of alternating current terminals being connected to a load having a leakage inductance;

a control circuit configured to turn switches included in the inverter on and off;

a first upper and lower arm portion including a first semiconductor switch and a second semiconductor switch connected in series, a first side of the first semiconductor switch and a first side of the second semiconductor switch being connected to each other and to a neutral point of the load;

a direct current power source connected in parallel to the first upper and lower arm portion such that a second side of the first semiconductor switch is connected to a positive pole of the direct current power source, and a second side of the second semiconductor switch is connected to a negative pole of the direct current power source; and

a switch connecting the second side of the first semiconductor switch and the positive direct current terminal of the inverter,

wherein in a first case where the switch connecting the second side of the first semiconductor switch and the positive direct current terminal of the inverter is off, one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to a first end of the leakage inductance of the load, first switches included in the inverter are on, thereby equivalently configuring a first equivalent switch, in an on-state, connected to a second end of the leakage inductance of the load, and energy from the direct current power source is stored in the leakage inductance of the load; and

wherein in a second case where the switch connecting the second side of the first semiconductor switch and the positive direct current terminal of the inverter is off, the other one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to the first end of the leakage inductance of the load, second switches included in the inverter are on, thereby equivalently configuring a second equivalent switch, in an on-state, connected to the second end of the leakage inductance of the load, and energy stored in the leakage inductance of the load is supplied to the power storage device.

15. The power conversion system according to claim 14, wherein the switch connecting the second side of the first semiconductor switch and the positive direct current terminal of the inverter is directly connected to the second side of the first semiconductor switch and the positive direct current terminal of the inverter.

16. A power conversion system, comprising:

a power storage device configured to store power;

an inverter having a positive direct current terminal, a negative direct current terminal, and a plurality of alternating current terminals, the power storage device being connected between the positive and negative direct current terminals, and the plurality of alternating current terminals being connected to a load having a leakage inductance;

a control circuit configured to turn switches included in the inverter on and off;

a first upper and lower arm portion including a first semiconductor switch and a second semiconductor switch connected in series, a first side of the first semiconductor switch and a first side of the second semiconductor switch being connected to each other and to a neutral point of the load;

a direct current power source connected in parallel to the first upper and lower arm portion such that a second side of the first semiconductor switch is connected to a positive pole of the direct current power source, and a second side of the second semiconductor switch is connected to a negative pole of the direct current power source, and

a switch connecting the second side of the second semiconductor switch and the negative direct current terminal of the inverter,

wherein in a first case where the switch connecting the second side of the second semiconductor switch and the negative direct current terminal of the inverter is off, one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to a first end of the leakage inductance of the load, first switches included in the inverter are on, thereby equivalently configuring a first equivalent switch, in an on-state, connected to a second end of the leakage inductance of the load, and energy from the direct current power source is stored in the leakage inductance of the load; and

wherein in a second case where the switch connecting the second side of the second semiconductor switch and the negative direct current terminal of the inverter is off, the other one of the first and second semiconductor switches included in the first upper and lower arm portion is on and connected to the first end of the leakage inductance of the load, second switches included in the inverter are on, thereby equivalently configuring a second equivalent switch, in an on-state, connected to the second end of the leakage inductance of the load, and energy stored in the leakage inductance of the load is supplied to the power storage device.

17. The power conversion system according to claim 16, wherein the switch connecting the second side of the second semiconductor switch and the negative direct current terminal of the inverter is directly connected to the second side of the second semiconductor switch and the negative direct current terminal of the inverter.