Feedforward control of motor drives with output sinewave filter

Patent metadata

Field	Value
Publication number	US-10158314-B2
Application number	US-201715421576-A
Country	US
Kind code	B2
Filing date	Feb 1, 2017
Priority date	Jan 16, 2013
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

Disclosed examples include power conversion systems and methods to operate an inverter to drive a motor load through an intervening output filter, a transformer and a cable, including a current regulator to compute a command value according to a current reference value and a motor current feedback value, a cross-coupled feedforward component to compensate the command value by an estimated cross-coupled voltage value to compute a control output value, a cross-coupled object component to compute the motor current feedback value according to a voltage value using a plant transfer function representing the output filter, the transformer, the cable and the motor load, and a controller to provide the inverter switching control signals to control the inverter according to the control output value.

First claim

The following is claimed:

1. A power conversion system, comprising:
an inverter comprising a DC input, an AC output, and a plurality of switching devices coupled between the DC input and the AC output and operative according to inverter switching control signals to convert DC electrical power received at the DC input to provide AC electrical output power at the AC output to drive a motor load through an intervening output filter, a transformer and a cable; and
a controller, including:
a current regulator component implemented by a processor to compute a command value according to a current reference value and a motor current feedback value,
a cross-coupled feedforward component implemented by the processor to compensate the command value by an estimated cross-coupled voltage value to compute a control output value, and
a cross-coupled object component implemented by the processor to compute the motor current feedback value according to a voltage value using a plant transfer function representing the output filter, the transformer, the cable and the motor load;

the controller being operative to provide the inverter switching control signals to control the inverter according to the control output value;
wherein the current regulator component computes a d-axis command value according to a d-axis current reference value and a d-axis motor current feedback value, and computes a q-axis command value according to a q-axis current reference value and a q-axis motor current feedback value; and
wherein the cross-coupled feedforward component compensates the d-axis command value by subtracting an estimated q-axis voltage value from the d-axis command value to compute a d-axis control output value, and wherein the cross-coupled feedforward component compensates the q-axis command value by adding an estimated d-axis voltage value to the q-axis command value to compute a q-axis control output value.

2. The power conversion system of claim 1 , wherein the cross-coupled feedforward component computes the estimated q-axis voltage value according to an estimated q-axis motor back EMF value.

3. The power conversion system of claim 1 , wherein the cross-coupled feedforward component computes the estimated d-axis voltage value according to a reference or feedback q-axis motor current value and an estimated inverter electrical frequency, and wherein the cross-coupled feedforward component computes the estimated q-axis voltage value according to a reference or feedback d-axis motor current value and the estimated inverter electrical frequency.

4. The power conversion system of claim 3 , wherein the cross-coupled feedforward component computes the estimated d-axis voltage value according to a reference or feedback q-axis inverter current value and the estimated inverter electrical frequency, and wherein the cross-coupled feedforward component computes the estimated q-axis voltage value according to a reference or feedback d-axis inverter current value and the estimated inverter electrical frequency.

5. The power conversion system of claim 1 ,
wherein the cross-coupled object component computes a d-axis output voltage value by adding a q-axis motor voltage value to a d-axis inverter voltage value;
wherein the cross-coupled object component computes a d-axis motor current feedback value according to the d-axis output voltage value using the plant transfer function;
wherein the cross-coupled object component computes a q-axis output voltage value by subtracting a d-axis motor voltage value from a q-axis inverter voltage value; and
wherein the cross-coupled object component computes a q-axis motor current feedback value according to the q-axis output voltage value using the plant transfer function.

6. The power conversion system of claim 5 , wherein the cross-coupled object component computes the d-axis motor voltage value according to a q-axis motor back EMF value.

7. The power conversion system of claim 5 , wherein the cross-coupled object component computes the d-axis motor voltage value according to the d-axis motor current feedback value, and wherein the cross-coupled object component computes the q-axis motor voltage value according to the q-axis motor current feedback value.

8. The power conversion system of claim 7 , wherein the cross-coupled object component computes the d-axis motor voltage value according to a d-axis inverter current feedback value (I inv.d ), and wherein the cross-coupled object component computes the q-axis motor voltage value according to a q-axis inverter current feedback value.

9. A method of operating an inverter to drive a motor load through an output filter and a transformer, the method comprising:
implementing a current regulator component to compute a command value according to a current reference value and a motor current feedback value;
implementing a cross-coupled feedforward component to compensate the command value by an estimated cross-coupled voltage value to compute a control output value;
implementing a cross-coupled object component to compute the motor current feedback value according to a voltage value using a plant transfer function representing the output filter, the transformer, the cable and the motor load; and
providing inverter switching control signals to control the inverter according to the control output value;
further comprising implementing the current regulator component to compute a d-axis command value according to a d-axis current reference value and a d-axis motor current feedback value, and to compute a q-axis command value according to a q-axis current reference value and a q-axis motor current feedback value; and
further comprising implementing the cross-coupled feedforward component to compensate the d-axis command value by subtracting an estimate q-axis voltage value from the d-axis command value to compute a d-axis control output value, and implementing the cross-coupled feedforward component to compensate the q-axis command value by adding an estimated d-axis voltage value to the q-axis command value to compute a q-axis control output value.

10. The method of claim 9 , wherein the cross-coupled feedforward component computes the estimated q-axis voltage value according to an estimated q-axis motor back EMF value.

11. The method of claim 9 , further comprising implementing the cross-coupled feedforward component to compute the estimated d-axis voltage value according to a reference or feedback q-axis motor current value and an estimated inverter electrical frequency, and implementing the cross-coupled feedforward component to compute the estimated q-axis voltage value according to a reference or feedback d-axis motor current value and the estimated inverter electrical frequency.

12. The method of claim 11 , further comprising implementing the cross-coupled feedforward component to compute the estimated d-axis voltage value according to a reference or feedback q-axis inverter current value and the estimated inverter electrical frequency, and implementing the cross-coupled feedforward component to compute the estimated q-axis voltage value according to a reference or feedback d-axis inverter current value and the estimated inverter electrical frequency.

13. The method of claim 9 , further comprising:
implementing the cross-coupled object component to compute a d-axis output voltage value by adding a q-axis motor voltage value to a d-axis inverter voltage value;
implementing the cross-coupled object component to compute a d-axis motor current feedback value according to the d-axis output voltage value using the plant transfer function;
implementing the cross-coupled object component to compute a q-axis

Assignees

• Rockwell Automation Tech Inc

Inventors

• Royak Semyon
• Dai Jingya
• Nondahl Thomas A
• Liu Jingbo
• Breitzmann Robert J
• Schmidt Peter B

Classifications

• H02M7/53873

  with digital control · CPC title

• H02P21/13

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title

• H02M2001/0009

  Electricity · mapped topic

• H02P21/22

  Current control, e.g. using a current control loop · CPC title

• H02P21/18

  Estimation of position or speed · CPC title