US 6,724,596 B2 · Hysteretic current control method and an uninterruptible power supply using same

Abstract

Presented is a control system and method for minimizing the adverse affects resulting from conventional hysteretic current control of power inverters, and an uninterruptible power supply using same. The system of the present invention uses control circuitry for monitoring and classifying the PWM switching events commanded by conventional hysteretic current control and adjusting the dead time delay injected based on these PWM events. Preferably, the control circuitry uses a minimum delay dead time component to preclude the possibility of a shoot through condition from occurring, and also includes a frequency control component of the total dead time delay. In one embodiment this frequency control component may vary in proportion to the switching frequency commanded by the hysteretic current control loop. In an alternate embodiment, the PWM switching events are classified into differing modes of operation, during which a particular fixed frequency control dead time delay is selected. The control of the present invention may also use a maximum difference current control limit for the dead time delay to preclude excessive output current swings beyond the typical hysteretic current control limits.

Claims25

Dependent claims

A current control method for use with an inverter having at least a first and a second switching element controllable to construct an AC output waveform in accordance with a pulse-width modulated (PWM) control signal from a hysteretic control circuit, comprising the steps of:

monitoring a duration of each PWM event;
classifying each of the PWM events into one of at least two classifications;
comparing each of the PWM's classification to a previous event classification;
selecting a dead time delay based on said step of comparing;
commanding off one of the switching elements;
and
delaying for the selected dead time delay a commanding on of another of the switching elements after the commanding off of the one of the switching elements.

4 more elements

A controller for use with an inverter having at least a first and a second switching element controllable to construct an output AC waveform for use by equipment coupled to an output thereof, comprising:

an inverter control circuit using hysteretic current control to generate a pulse-width modulated (PWM) inverter control signal to control transitions of the switching elements to construct the output AC waveform in response to a voltage and a current feedback from the inverter output, said PWM inverter control signal having PWM events defined by transitions thereof;
and
a logic driver circuit coupled to receive said PWM inverter control signal, said logic circuit generating a first and a second drive signal to transition the first and second switching elements in response to said PWM inverter control signal;
and
wherein said logic driver circuit monitors a duration of said PWM events and delays a generation of said first and said second drive signals for one of at least a first and a second dead time based on said duration of said PWM events.

2 more elements

An uninterruptible power supply, comprising:

an inverter having a first input adapted to receive line AC power, a second input adapted to receive stored DC power, and an inverter output, the inverter having at least a first and a second switching element controllable to supply an AC voltage and current output on said inverter output from the line AC power and the stored DC power;
and
a controller having a voltage and a current feedback input coupled to said inverter output, and a first and a second drive signal output operatively coupled to said first and said second switching elements to control construction of said AC voltage and current output, said controller using hysteretic current control to generated a pulse-width modulated (PWM) control signal, said controller further including a logic driver circuit operative to generated said first and said second drive signals in response to said PWM control signal;
and
wherein said logic driver circuit monitors a duration of each pulse-width of said PWM control signal and inserts a dead time delay between transitions of said first and said second drive signal having a duration based on said duration of each pulse-width of said PWM control signal.

2 more elements

Dependencies are inferred from the claim text.

Hysteretic current control method and an uninterruptible power supply using same

Life of this patent

Hysteretic current control method and an uninterruptible power supply using same

Life of this patent

Abstract

Claims25