US 5,465,011 AGranted

Uninterruptible power supply with improved output regulation

AssigneeSquare D Company

InventorsFrank D. Miller, Thomas E. Helfrich

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Abstract

A microprocessor based uninterruptible power supply generates an AC electrical output power from an AC input source when the AC input source is within settable voltage limits and from an auxiliary source of DC power when the AC input source is outside said the voltage limits. The microprocessor provides monitoring of the AC input voltage to determine its amplitude and frequency, and uses this information to set the magnitude and frequency of the AC output voltage and to select the source of the AC output power. A power factor improvement circuit boosts the selected source to a high DC voltage which is inverted by a chopper circuit to produce a high frequency AC voltage is rectified and sent to a PWM inverter to produce the AC output power. An average current feedback loop provides the output voltage regulation and utilizes current limiting to provide output current limiting for protection against short circuits and overloads. A voltage phase relationship is maintained between the AC input power and AC output power to eliminate voltage and current transients at transfer times between the AC and DC input sources. A serial data communications port sends data sent over a network that includes signals indicative of the status of the uninterruptible power supply and receives data from the network for controlling operation of the uninterruptible power supply.

Claims21

Dependent claims

An improved uninterruptible power supply for supplying a load with AC electrical output power from an AC input source when said AC input source is within settable voltage limits, and supplying said load with AC electrical output power from a DC auxiliary power source when said AC input source is outside said voltage limits, said improved uninterruptible power supply comprising:

A. means for monitoring said AC input source to determine frequency and amplitude of said AC input source;
B. means for converting said AC input source to a first DC voltage;
C. means for transferring between said AC input source and said DC auxiliary power source to select an input source of said AC electrical output power, said input source being said first DC voltage when the amplitude of said AC input source is within said voltage limits and said DC auxiliary power source when the amplitude of said AC input source is outside said voltage limits;
D. means for providing active power factor correction of said AC input source when said AC input source is said input source;
E. means for boosting and regulating said input source to produce a second and higher DC voltage;
F. means for converting said second DC voltage to produce equal and commonly grounded positive and negative DC voltages;
G. means for inverting said positive and negative DC voltages to produce said AC electrical output power;
H. means for generating a signal proportional to an average AC electrical output current of said AC;
electrical output power to provide an average current feedback loop to said inverting means:
I. means for regulating said AC electrical output power to a voltage amplitude corresponding to said determined frequency;
J. means for limiting said AC electrical output power to a current level within settable current limits to prevent failure of said inverting means;
and
K. means for maintaining a voltage phase relationship between said AC input power and said AC output power during said transferring between said AC input power source and said DC auxiliary power source.

10 more elements

In an uninterruptible power supply for supplying a load with AC electrical output power, a method for generating said AC electrical output power from an AC input source when said AC input source is within settable voltage limits and for generating said AC electrical output power from a DC auxiliary power source when said AC input source is outside said voltage limits, said method comprising:

A. monitoring said AC input source to determine frequency and amplitude of said AC input source;
B. converting said AC input source to a first DC voltage;
C. transferring between said AC input source and said DC auxiliary power source to select an input source of said AC electrical output power, said input source being said first DC voltage when the amplitude of said AC input source is within said voltage limits and said DC auxiliary power source when the amplitude of said AC input source is outside said voltage limits;
D. providing active power factor correction of said AC input source when said AC input source is said input source;
E. boosting and regulating said input source to produce a second and higher DC voltage;
F. converting said second DC voltage to produce equal and commonly grounded positive and negative DC voltages;
G. inverting said positive and negative DC voltages to produce said AC electrical output power;
H. generating a signal proportional to an average AC output current of said AC electrical output power to provide an average current feedback loop for regulating said AC electrical output power to a voltage amplitude corresponding to said determined frequency;
I. limiting said AC electrical output power to a current level within settable current limits to prevent failure of said inverting means;
and
J. maintaining a voltage phase relationship between said AC input power and said AC output power during said transferring between said AC input power source and said DC auxiliary power source and vice versa to prevent voltage and current transients at the time of said transferring.

8 more elements

Dependencies are inferred from the claim text.