Digital signal processor controlled uninterruptable power supply

• US 6,169,669 B1
• Filed: 07/17/2000
• Issued: 01/02/2001
• Est. Priority Date: 07/15/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Choudhury, Shamim A.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/617,341
• Time in Patent Office: 169 Days
• Field of Search: 363/34, 363/37, 363/67, 363/95, 363/98, 307/64, 307/66, 320/118
• US Class Current: 363/37
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements

Abstract

An uninterruptable power supply controlled by a digital signal processor. The digital signal processor periodically senses an input current, an input voltage, a battery current, a battery voltage boost circuit, first and second DC bus voltages, an output current and an output voltage. The digital signal processor controls an AC to DC conversion unit, a battery charger, a battery voltage boost circuit and a DC to AC inverter via an inner current loop and an outer voltage loop. The digital signal processor calculates the inner current loops each predetermined time interval and calculates the outer voltage loops every two predetermined time intervals. The digital signal processor preferably alternately senses a first group of signals consisting of the input voltage, the input current, the output voltage and the output current and a second group of signals consisting of the battery voltage, the battery current, the first DC bus voltage and a second DC bus voltage. The timing of the input signal sensing and the respective current loop and voltage loop calculations are timed by one or more repetitive interrupt timers.

Claims

1. An uninterruptable power supply comprising:

an AC to DC conversion unit receiving an AC power input and generating a DC voltage on a DC bus;

a battery;

a battery charger connected to said DC bus and said battery for charging said battery from said DC bus when receiving AC power;

a battery boost circuit connected to said DC bus and said battery for supplying electric power on said DC bus from said battery when not receiving AC power;

a DC to AC inverter connected to said DC bus for generating AC power for a load from said DC bus; and

a digital signal processor connected to said AC to DC conversion unit, said battery charger, said battery boost circuit and said DC to AC inverter, said digital signal processor programmed to

periodically sense an input current, an input voltage, a battery current, a battery voltage, a first DC bus voltage, a second DC bus voltage, an output current and an output voltage,

control said AC to DC conversion unit to present a stable input power factor to the AC power input via an inner current loop dependent upon an input current and an outer voltage loop dependent upon an input voltage,

control said battery charger upon receipt of AC power via an inner current loop dependent upon a battery current and an outer voltage loop dependent upon a difference between a battery voltage and a first DC bus voltage,

control said battery boost circuit upon failure of AC power via an inner current loop dependent upon said battery current and an outer voltage loop dependent upon a difference between said battery voltage and said first DC bus voltage,

control said DC to AC inverter to supply stable AC power via an inner current loop dependent upon an output current and an outer voltage loop dependent upon an output voltage;

calculate said inner current loops in said controlling of said AC to DC conversion unit, said battery charger, said battery boost circuit and said DC to AC inverter each predetermined time interval, and

calculate said outer voltage loops in said controlling of said AC to DC conversion unit, said battery charger, said battery boost circuit and said DC to AC inverter every two predetermined time intervals.

2. The uninterruptable power supply of claim 1, wherein:

said digital signal processor is programmed to alternately sense a first group of signals consisting of said input voltage, said input current, said output voltage and said output current and a second group of signals consisting of said battery voltage, said battery current, said first DC bus voltage and a second DC bus voltage.

3. The uninterruptable power supply of claim 2, wherein:

said digital signal processor includes a first repetitive interrupt timer capable of generating an interrupt upon counting to a first predetermined number and counting to a second predetermined number, said digital signal processor programmed to

sense said first group of signals in response to said first repetitive interrupt timer counting to said first predetermined number, and

sense said second group of signals in response to said first repetitive interrupt timer counting said second predetermined number.

4. The uninterruptable power supply of claim 3, wherein:

said digital signal processor includes a second repetitive interrupt timer having a time interval twice a time interval of said first repetitive interrupt timer, said digital signal processor programmed to

calculate said inner current loops dependent upon sensed current in response to said first repetitive interrupt timer counting to said first predetermined number; and

calculate said outer voltage loops dependent upon sensed voltage in response to said second repetitive interrupt timer counting to a third predetermined number.

5. A method of uninterruptable power supply comprising the steps of:

controlling input power factor presented to an AC power input of an AC to DC conversion unit via an inner current loop dependent upon an input current and an outer voltage loop dependent upon an input voltage;

controlling battery charging upon receipt of AC power via an inner current loop dependent upon a battery current and an outer voltage loop dependent upon a difference between a battery voltage and a first DC bus voltage;

controlling battery boost voltage upon failure of AC power via an inner current loop dependent upon said battery current and an outer voltage loop dependent upon a difference between said battery voltage and said first DC bus voltage;

controlling DC to AC inversion via an inner current loop dependent upon an output current and an outer voltage loop dependent upon an output voltage;

calculating said inner current loops in said controlling of said input power factor, said battery charging, said battery voltage boost and said DC to AC inversion once each predetermined time interval; and

calculating said outer voltage loops in said controlling of said input power factor, said battery charging, said battery voltage boost and said DC to AC inversion every two predetermined time intervals.

6. The method of uninterruptable power supply of claim 5, further comprising:

alternately sensing a first group of signals consisting of said input voltage, said input current, said output voltage and said output current and a second group of signals consisting of said battery voltage, said battery current, said first DC bus voltage and a second DC bus voltage.

7. The method of uninterruptable power supply of claim 5, wherein:

said step of alternately sensing a first group of signals and a second group of signals includes sensing said first group of signals in response to a repetitive interrupt timer counting to a first predetermined number and sensing said second group of signals in response to the repetitive interrupt timer counting to a second predetermined number different from the first predetermined number.

8. The method of uninterruptable power supply of claim 5, wherein:

said step of calculating said inner current loops includes calculation of control parameters dependent upon sensed current in response to a first repetitive interrupt timer reaching a first predetermined number; and

said step of calculating said outer voltage loops includes calculation of control parameters dependent upon sensed voltage in response to a second repetitive interrupt timer counting to a second predetermined number, said second repetitive interrupt timer having a repeat interval twice a repeat interval of the first repetitive interrupt timer.