Method and compensation modulator for dynamically controlling induction machine regenerating energy flow and direct current bus voltage for an adjustable frequency drive system

• US 6,768,284 B2
• Filed: 09/30/2002
• Issued: 07/27/2004
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Lee, Kevin, Becker, Scott K., Schmidt, Kevin J.
• Primary Examiner(s): Patel, Rajnikant B
• Application Number:
  US10/260,917
• Publication Number:
  US 20040062062A1
• Time in Patent Office: 666 Days
• Field of Search: 318/268, 318/805, 318/807, 318/808, 318/809, 318/269, 318/99, 318/801, 318/802, 318/803, 318/810, 363/37.39, 363/41, 363/127, 363/132, 363/98, 363/37, 363/40
• US Class Current: 318/808
• CPC Class Codes: H02M 7/797 using semiconductor devices only
• CPC Class Codes: H02P 21/36 Arrangements for braking or slowing; Four quadrant control

Abstract

A method for dynamically controlling regenerating energy flow and direct current bus voltage for an adjustable frequency drive system includes sensing a direct current voltage of a direct current bus; and sensing a plurality of alternating currents at outputs of an inverter. The sensed alternating currents are transformed to a stationary current vector. Voltage and frequency values are converted to a stationary voltage vector and an angle. The angle and the stationary current vector are transformed to a rotating current vector including torque and flux producing current components. An induction machine generating mode is determined when the torque producing current component reverses polarity. The voltage and frequency values limit the direct current voltage of the direct current bus at a predetermined threshold responsive to the generating mode. The stationary voltage vector and the angle are converted to pulse width modulated control inputs of the inverter.

Claims

1. A method for dynamically controlling induction machine regenerating energy flow and direct current bus voltage for an adjustable frequency drive system comprising a direct current bus and an inverter inputting the direct current bus, said inverter including a plurality of control inputs and a plurality of alternating current outputs, said method comprising:

sensing a direct current voltage of said direct current bus;

sensing a plurality of alternating currents at the alternating current outputs of said inverter;

transforming said sensed alternating currents to a stationary current vector;

converting a voltage value and a frequency value to a stationary voltage vector and an angle;

transforming the angle and said stationary current vector to a rotating current vector including a torque producing current component and a flux producing current component;

determining a generating mode of said induction machine when said torque producing current component reverses polarity;

employing the voltage value and the frequency value to limit the direct current voltage of said direct current bus at a predetermined threshold responsive to said generating mode of said induction machine;

determining a voltage difference between the direct current voltage of said direct current bus and the predetermined threshold;

employing a compensation modulator to compensate the voltage difference and provide a compensated voltage difference;

applying the voltage difference to a first algorithm having a first gain and a first output quantity in the generating mode;

applying the compensated voltage difference to second and third algorithms having second and third gains and second and third output quantities, respectively, in the generating mode;

providing an intermediate frequency from a set frequency and the first output quantity;

adding the second output quantity to the intermediate frequency to provide a change frequency value;

employing the third output quantity as a change voltage value;

calculating the voltage value as the sum of a set voltage value and the change voltage value, and calculating the frequency value as the sum of a set frequency value and the chance frequency value; and

converting the stationary voltage vector and the angle to pulse width modulated control signals for the control inputs of said inverter.

2. The method of claim 1 further comprising:

employing said direct current bus having a nominal voltage; and

determining when said induction machine is no longer in the generating mode, and responsively resetting the direct current voltage of said direct current bus to said nominal voltage.

3. The method of claim 1 further comprising:

adjusting the predetermined threshold as a function of the direct current voltage of said direct current bus.

4. The method of claim 3 further comprising:

calculating the predetermined threshold as the direct current voltage of said direct current bus plus a predetermined voltage.

5. The method of claim 4 further comprising:

employing +60 VDC as said predetermined voltage.

6. The method of claim 1 further comprising:

determining a motoring mode when the generating mode of said induction machine is not active, and responsively setting the second and third output quantities to zero.

7. The method of claim 1 further comprising:

employing a first range of frequencies of said alternating currents;

employing a second range of frequencies of said alternating currents, said second range being greater than said first range;

employing a third range of frequencies of said alternating currents, said third range being greater than said second range;

employing the voltage difference for the first range of frequencies to provide the compensated voltage difference, which is output with a first constant gain;

nonlinearly increasing amplitude of the compensated voltage difference with frequency of said alternating currents; and

employing the voltage difference for the third range of frequencies to provide the compensated voltage difference, which is output with a second constant gain, which is greater than the first constant gain.

8. The method of claim 7 further comprising:

employing the voltage difference and the compensated voltage difference having about equal phase angles for said first range of frequencies;

employing the voltage difference and the compensated voltage difference having about equal phase angles for said third range of frequencies;

employing a first phase angle of the compensated voltage difference for the second range of frequencies; and

employing a second phase angle of the voltage difference for the second range of frequencies, with said first phase angle leading the second phase angle by more than about 40 degrees.

9. The method of claim 1 further comprising:

employing the torque producing current vector and the flux producing current vector to calculate power factor of said induction machine.

10. An adjustable frequency drive system comprising:

a three-phase induction machine; and

an adjustable frequency drive comprising;

a converter including a plurality of alternating current inputs and a direct current output having a first node and a second node;

a capacitor electrically connected between the first and second nodes of said direct current output;

an inverter including a direct current input, a plurality of switches, a plurality of control inputs, and a plurality of alternating current outputs, said direct current input electrically connected to said direct current output, said alternating current outputs adapted to electrically connect to said alternating current inputs of said induction machine;

each of said switches electrically connected between one of the first and second nodes and one of the alternating current outputs of said inverter, each of said control inputs controlling one of said switches;

a voltage sensor sensing a direct current voltage at the direct current output of said converter and outputting a sensed voltage value;

a plurality of current sensors sensing a plurality of alternating currents at the alternating current outputs of said inverter and outputting a plurality of sensed current values; and

a processor comprising;

a plurality of inputs for said sensed current values and said sensed voltage value,

a plurality of outputs for the control inputs of said inverter,

a Clarke Transform module transforming said sensed current values to a stationary current vector,

a space vector module including a plurality of inputs and a plurality of outputs, the inputs of said space vector module comprising a set voltage value, a set frequency value, a change voltage value, and a change frequency value, the outputs of said space vector module comprising a stationary voltage vector and an angle,

a pulse width modulation (PWM) module including a plurality of inputs and a plurality of outputs, the inputs of said PWM module comprising the stationary voltage vector and the angle, the outputs of said pulse width modulation module providing the control inputs of said inverter,

a Park Transform module transforming the angle and said stationary current vector to a rotating current vector, and

a regeneration override module comprising a plurality of inputs and a plurality of outputs, the inputs of said regeneration override module comprising the sensed voltage value and said rotating current vector, the outputs of said regeneration override module comprising the change voltage value and the change frequency value, said regeneration override module dynamically controlling regenerating energy flow from the induction machine to the direct current output of said converter, wherein said regeneration override module includes means for determining a voltage difference between the sensed voltage value and a predetermined threshold, means for compensating the voltage difference and providing a compensated voltage difference, means for providing a first output quantity in the generating mode from the voltage difference and a first gain, means for providing a second output quantity in the generating mode from the compensated voltage difference and a second gain, and means for providing a third output quantity in the generating mode from the compensated voltage difference and a third gain.

11. The adjustable frequency drive system of claim 10 wherein said regeneration override module further includes means for providing an intermediate frequency from the set frequency value and the first output quantity, and means for adding the second output quantity to the intermediate frequency to provide the change frequency value;

and wherein said third output quantity is the change voltage value.

12. The adjustable frequency drive system of claim 10 wherein said predetermined threshold is the sensed voltage value plus a predetermined voltage.