Method and apparatus for compensating for device dynamics in inverter based control systems
AssigneeRockwell Automation Technologies, Inc.
InventorsRussel J. Kerkman, David Leggate
Life of this patent
Estimating the term…
Abstract
A method and apparatus for reducing distortion at the outputs of an inverter system, the apparatus including a polarity discriminator for determining the polarity of a current passing through an output terminal to a load, a compensator programmed with different upper and lower compensation values and controlled by the discriminator to provide the upper compensation value as an output when the current polarity is positive and providing the lower compensation value when the polarity is negative and a combiner for receiving a modulating signal and the compensation value provided by the compensator and mathematically combining the two signals to generate a modified modulating signal.
Claims24
An apparatus for reducing distortion at the output terminals of an inverter drive system, wherein the system includes an N phase inverter and an inverter controller, the inverter including a plurality of switches that link positive and negative DC buses to N output terminals, a separate terminal for each of the inverter phases, the controller receiving N modulating signals and a carrier signal and comparing the modulating signals and the carrier signals to generate firing pulses to control the switches, the apparatus comprising, for each of the N phases:
- a polarity discriminator for determining the polarity of the current passing through the phase output terminal;
- a device dynamics compensator including upper and lower compensation values where the upper compensation value is different than the lower compensation value, the compensator linked to and receiving the polarity signal from the discriminator and, when the polarity is positive, providing the upper compensation value as an compensation signal and, when the polarity is negative, providing the lower compensation value as the compensation signal;
- and
- a combiner for receiving the modulating signal and the compensation signal and mathematically combining the modulating and compensation signals.
A method for identifying compensation values to be used to reduce distortion at the output terminals of an inverter drive system linked to a load wherein the system includes an N phase inverter, a current regulator and a modulator, the inverter including a plurality of switches that link positive and negative DC buses to N output terminals, a separate terminal for each of the inverter phases, the regulator receiving a command current value and generating a command voltage value, the modulator receiving the command voltage value and generating modulating signals used to generate firing pulses to control the switches, the compensation values used to modify the modulating signals to reduce the terminal distortion, the method comprising the steps of:
- providing a first high DC current of a first polarity to the regulator and sensing a high regulator output voltage;
- providing a first low DC current of the first polarity to the regulator and sensing a low regulator output voltage;
- mathematically combining the high and low DC currents and the high and low voltages to generate a compensation value;
- and
- storing the compensation value for subsequent mathematical combination with the modulating signals.
A method for reducing distortion at the output terminals of an inverter drive system linked to a load wherein the system includes an N phase inverter and an inverter controller, the inverter including a plurality of switches that link positive and negative DC buses to N output terminals, a separate terminal for each of the inverter phases, the controller receiving N modulating signals and a carrier signal and comparing the modulating signals and the carrier signals to generate firing pulses to control the switches, the method comprising the steps of
- providing upper and lower compensation values where the upper compensation value is different than the lower compensation value;
- determining the polarity of the current passing through the phase output terminal;
- when the current polarity is positive, providing the upper compensation value as a compensation signal and, when the polarity is negative, providing the second compensation value as the compensation signal;
- and
- mathematically combining the modulating and compensation signals.
An apparatus for reducing distortion at the output terminals of an inverter drive system, wherein the system includes an N phase inverter and an inverter controller, the inverter including a plurality of switches that link positive and negative DC buses to N output terminals, a separate terminal for each of the inverter phases, the controller receiving N modulating signals and a carrier signal and comparing the modulating signals and the carrier signals to generate firing pulses to control the switches, the apparatus comprising, for each of the N phases:
- means for storing upper and lower compensation values where the upper compensation value is different than the lower compensation value, the means for storing linked to and receiving the polarity signal from the means for determining and, when the polarity is positive, providing the upper compensation value as a compensation signal and, when the polarity is negative, providing the lower compensation value as the compensation signal;
- and
- means for mathematically combining the modulating and compensation signals.
An apparatus for reducing distortion at the output terminals of an inverter drive system, wherein the system includes an N phase inverter and an inverter controller, the inverter including a plurality of switches that link positive and negative DC buses to N output terminals, a separate terminal for each of the inverter phases, the controller receiving N modulating signals and a carrier signal and comparing the modulating signals and the carrier signals to generate firing pulses to control the switches, the apparatus comprising:
- a processor running a pulse sequencing program to perform the steps of:
- providing upper and lower compensation values where the upper and compensation value is different than the lower compensation value;
- determining the polarity of the current passing through the phase output terminal;
- when the current polarity is positive, providing the upper compensation value as a compensation signals and, when the polarity is negative, providing the second compensation value as the compensation signal;
- and
- mathematically combining the modulating and compensation signals.
Dependencies are inferred from the claim text.