Uninterruptable power supply

• US 6,175,511 B1
• Filed: 04/28/2000
• Issued: 01/16/2001
• Est. Priority Date: 12/24/1999
• Status: Expired due to Term

• Current Assignee: Toshiba Mitsubishi-Electric Industrial Systems Corporation (Toshiba Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Ooba, Norio
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US09/559,829
• Time in Patent Office: 263 Days
• Field of Search: 363/34, 363/37, 363/80, 363/124, 307/46, 307/64, 307/66
• US Class Current: 363/37
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

An uninterruptable power supply in which, even if the consumed electric power of a load is increased, the voltage of a D.C. intermediate circuit is not decreased below a set voltage and the input electric power from an A.C. power source is limited to no more than a set value. The uninterruptable power supply includes: a rectifier for converting an alternating current into a direct current; an inverter for converting the direct current into an alternating current output to a load; a stepup/stepdown chopper for charging batteries and for discharging the batteries; a service interruption detector for detecting the service interruption of the A.C. power source; and a control circuit for operating the stepup/stepdown chopper as a stepdown chopper during non-interruption to charge the batteries, and as a boosting chopper to supply direct current with the batteries as the D.C. power source, wherein, when the input electric power exceeds a limit, the stepup/stepdown chopper operates as the boosting chopper to supply electric power from the batteries, reducing the electric power input from the A.C. power source.

Claims

1. An uninterruptable power supply comprising:

an input filter for smoothing an A.C. current from an A.C. power source;

a rectifier for converting an alternating current from said input filter into a direct current;

a D.C. intermediate circuit receiving the direct current;

an inverter for converting a direct current from said D.C. intermediate circuit into an alternating current supplied to a load;

a chopper reactor;

a stepup/stepdown chopper having batteries charged through said chopper reactor from said D.C. intermediate circuit, and discharged to said D.C. intermediate circuit through said chopper reactor;

A.C. power source voltage detecting means for detecting voltage of the A.C. power source;

service interruption detecting means for detecting a service interruption from the voltage detected by said voltage detecting means; and

control means for operating said stepup/stepdown chopper as a stepdown chopper during non-interruption of the A.C. power source in response to by said service interruption detecting means to charge said batteries, for operating said stepup/stepdown chopper as a boosting chopper during a service interruption to supply the direct current to said D.C. intermediate circuit with the batteries as a D.C. power source, wherein said control means, when input electric power inputted from the A.C. power source exceeds an electric power limitation, operates said stepup/stepdown chopper as the boosting chopper to supply a part of the electric power supplied from said inverter to the load from said batteries, thereby reducing the input electric power from the A.C. power source.

2. The uninterruptable power supply according to claim 1, further comprising a D.C. intermediate circuit voltage detecting means for detecting a voltage across said D.C. intermediate circuit, wherein said control means detects, in response to the voltage detected by said D.C. intermediate circuit voltage detecting means, when the input electric power input from the A.C. power source exceeds the electric power limitation.

3. The uninterruptable power supply according to claim 1, further comprising:

D.C. intermediate circuit voltage detecting means for detecting a voltage across said D.C. intermediate circuit, current detecting means for detecting current output by said rectifier, and input electric power detecting means for detecting the input electric power by multiplying the voltage detected by said D.C. intermediate circuit voltage detecting means by the current detected by said current detecting means, wherein said control means detects, the response to the electric power detected by said input electric power detecting means, when the input electric power input from the A.C. power source exceeds the electric power limitation.

4. The uninterruptable power supply according to claim 1, further comprising D.C. intermediate circuit voltage detecting means for detecting a voltage of the D.C. intermediate circuit, and input electric power detecting means for detecting the input electric power in response to the voltage detected by said D.C. intermediate circuit voltage detecting means, the voltage detected by said A.C. power source voltage detecting means, and impedance of said input filter, wherein the control means detects, in response to the input electric power detected by said input electric power detecting means, when the input electric power input from the A.C. power source exceeds the electric power limitation.

5. The uninterruptable power supply according to claim 1, further comprising:

inverter output voltage detecting means for detecting output voltage of said inverter;

inverter output current detecting means for detecting output current of said inverter;

inverter output electric power detecting means for detecting output electric power of said inverter by multiplying the voltage detected by said inverter output voltage detecting means by the current detected by said inverter output current detecting means;

battery output voltage detecting means for detecting output voltage of said batteries;

battery output current detecting means for detecting output current of said batteries; and

battery output electric power detecting means for detecting output electric power of said batteries by multiplying the voltage detected by said battery output voltage detecting means by the current detected by said battery output current detecting means, wherein said control means detects, in response to a sum of the electric power detected by said inverter output electric power detecting means and the electric power detected by said battery output electric power detecting means, when the input electric power input from the A.C. power source exceeds the electric power limitation.

6. The uninterruptable power supply according to claim 1, wherein said stepup/stepdown chopper includes switching means connected between said batteries and said chopper reactor for protection against an overcurrent, and circulation means for making a current which flows due to the energy accumulated in said chopper reactor upon opening of said switching means, circulate through said D.C. intermediate circuit.

7. The uninterruptable power supply according to claim 1, wherein said stepup/stepdown chopper includes, as said chopper reactor, a charging chopper reactor in a charging path leading to said batteries and a discharging chopper reactor in a discharging path leading to said D.C. intermediate circuit, wherein said charging chopper reactor has a first inductance and said discharging chopper reactor has a second inductance smaller than the first inductance.