Power converting apparatus

• US 7,577,007 B2
• Filed: 11/29/2006
• Issued: 08/18/2009
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Mori, Osamu, Yamada, Masaki, Iwata, Akihiko
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US11/564,456
• Publication Number:
  US 20070147098A1
• Time in Patent Office: 993 Days
• Field of Search: 363/71, 363/43, 363/41, 363/72, 363/68, 323/266
• US Class Current: 363/71
• CPC Class Codes: H02J 3/01 Arrangements for reducing harmonics or ripples
• CPC Class Codes: H02J 3/1857 wherein such bridge converter is a multilevel converter
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]
• CPC Class Codes: Y02E 40/40 Arrangements for reducing harmonics

Abstract

A power converting apparatus used as an active filter includes single-phase multiplex inverter unit for converting DC power into AC power and a control unit for controlling the single-phase multiplex inverter unit. The single-phase multiplex inverter unit includes a first single-phase inverter and a second single-phase inverter. The first single-phase inverter to which a maximum DC voltage is supplied outputs voltage pulses at a rate of one pulse per half the period of an AC voltage fed from an AC source. The control unit includes a pair of hysteresis comparator circuits for driving the second single-phase inverter such that an AC source current follows a sinusoidal target current.

Claims

1. A power converting apparatus comprising:

a single-phase multiplex converter connected to a load via a reactor to provide electric power to the load, said single-phase multiplex converter including a first single-phase inverter to which a maximum DC source voltage is supplied and at least one second single-phase inverter, said first single-phase inverter outputting voltage pulses at a rate of one pulse per half period of a reference AC voltage, said first and at least one second single-phase inverters being connected in series at AC output sides of said single-phase inverters, wherein said first and at least one second single-phase inverters convert DC power fed from a DC power supply into AC power; and

a control unit for controlling said single-phase multiplex converter to produce an output voltage having a quasi-sinusoidal waveform simulated by the sum of output voltages of respective single-phase inverters, said control unit including a current controller for regulating an output current of said single-phase multiplex converter to follow a target current which is determined in accordance with the load, wherein

said current controller drives said at least one second single-phase inverter such that the output current of said single-phase multiplex converter follows the target current,

said control unit includes

a central processing unit having a mathematical processing capability, and

a control circuit including a digital signal processing circuit and an analog circuit including a hysteresis comparator circuit having an ordinary range of hysteresis,

said central processing unit outputs a current signal corresponding to the target current,

said current controller regulates the output current using said control circuit,

said current controller generates a control signal which is supplied to said at least one second single-phase inverter so that the output current of said single-phase multiplex converter increases and decreases within the ordinary range of hysteresis, and

said hysteresis comparator circuit has a marginal range of hysteresis encompassing the ordinary range of hysteresis and, if the output current of said single-phase multiplex converter goes out of the ordinary range of hysteresis, said control unit makes a correction so that output current of said single-phase multiplex converter varies within the ordinary range of hysteresis.

2. The power converting apparatus according to claim 1, wherein a ratio V/Vm of a total DC source voltage V, supplied to said at least one second single-phase inverter, to the DC source voltage Vm, supplied to said first single-phase inverter, is within a range of 0.5 to 1.0.

3. The power converting apparatus according to claim 1, wherein the ordinary range of hysteresis of said hysteresis comparator circuit is determined based on amplitude of output voltage of said second single-phase inverter and a maximum switching frequency of switching devices constituting said second single-phase inverter.

4. The power converting apparatus according to claim 1, wherein said first single-phase inverter is controlled such that output voltage of said first single-phase inverter produces a stepwise waveform inscribed in each half-wave portion of the reference AC voltage and absolute value of the output voltage of said first single-phase inverter is equal to or smaller than absolute value of the reference AC voltage at all times.

5. The power converting apparatus according to claim 1, wherein said first single-phase inverter is controlled such that output voltage of said first single-phase inverter produces a stepwise waveform circumscribed about each half-wave portion of the reference AC voltage and absolute value of the output voltage of said first single-phase inverter is equal to or larger than absolute value of the reference AC voltage at all times.

6. The power converting apparatus according to claim 1, wherein

the DC source voltage supplied to said first single-phase inverter is variable, and

said control unit controllably drives said second single-phase inverter in such a manner that amounts of electric power supplied to and discharged from the DC power supply of said second single-phase inverter through said second single-phase inverter are balanced.

7. The power converting apparatus according to claim 1, wherein said plurality of single-phase inverters includes said first single-phase inverter and only one second single-phase inverter.

8. The power converting apparatus according to claim 1, wherein

said single-phase multiplex converter is connected between an AC power supply and the load in parallel with the load via the reactor, and

said single-phase multiplex converter is used as an active filter which outputs a harmonic compensation current for canceling harmonics generated by the load.

9. A power converting apparatus comprising:

a single-phase multiplex converter connected to a load via a reactor to provide electric power to the load, said single-phase multiplex converter including a first single-phase inverter to which a maximum DC source voltage is supplied and at least one second single-phase inverter, said first single-phase inverter outputting voltage pulses at a rate of one pulse per half period of a reference AC voltage, said first and at least one second single-phase inverters being connected in series at AC output sides of said single-phase inverters, wherein said first and at least one second single-phase inverters convert DC power fed from a DC power supply into AC power; and

a control unit for controlling said single-phase multiplex converter to produce an output voltage having a quasi-sinusoidal waveform simulated by the sum of output voltages of respective single-phase inverters, said control unit including a current controller for regulating an output current of said single-phase multiplex converter to follow a target current which is determined in accordance with the load, wherein

said current controller drives said at least one second single-phase inverter such that the output current of said single-phase multiplex converter follows the target current, and

said control unit adjusts the DC source voltage supplied to said first single-phase inverter so that said control unit controllably drives said second single-phase inverter in such a manner that amounts of electric power supplied to and discharged from the DC power supply of said second single-phase inverter through said second single-phase inverter are balanced.

10. The power converting apparatus according to claim 9, wherein

said control unit includes a hysteresis comparator circuit having an ordinary range of hysteresis, and

said current controller generates a control signal which is supplied to said at least one second single-phase inverter so that the output current of said single-phase multiplex converter increases and decreases within the ordinary range of hysteresis.