Sensorless motor drive vector control with feedback compensation for filter capacitor current

• US 9,985,565 B2
• Filed: 04/18/2016
• Issued: 05/29/2018
• Est. Priority Date: 04/18/2016
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Royak, Semyon, Dai, Jingya, Liu, Jingbo, Nondahl, Thomas A., Al-Nabi, Ehsan
• Primary Examiner(s): Santana, Eduardo Colon
• Assistant Examiner(s): Laughlin, Charles S
• Application Number:
  US15/131,160
• Publication Number:
  US 20170302209A1
• Time in Patent Office: 771 Days
• CPC Class Codes: H02P 21/0003 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 21/24 Vector control not involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 23/14 Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
• CPC Class Codes: H02P 25/02 characterised by the kind of motor
• CPC Class Codes: H02P 6/18 without separate position detecting elements

Abstract

Disclosed examples include motor drive power conversion systems with an inverter, as well as a controller methods to drive a motor in which output filter capacitor currents are computed and used to compensate the motor control in consideration of damping resistance values of an output filter.

Claims

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 output filter; and

a controller configured to;

compute a speed error value according to a speed reference value and a speed feedback value using a summing component;

compute a torque reference value according to the speed error value using a proportional-integral control component;

compute a motor current reference value according to the torque reference value using a lookup table or a parametric equation;

compensate the motor current reference value according to capacitor currents of the output filter by computing an inverter output current reference value according to the motor current reference value, an inverter operating frequency, a capacitance value of filter capacitor components of the output filter, and a resistance value of filter resistor components of the output filter; and

provide the inverter switching control signals to control the inverter according to the inverter output current reference value using a second proportional-integral control component;

wherein the controller computes d and q axis filter capacitor current values icap.comp.d and icap.comp.q according to the following equations;

2. The power conversion system of claim 1, wherein the controller computes filter capacitor current values according to filter output voltage values representing output voltages of the filter, capacitance values representing capacitances of filter capacitors of the filter, resistance values representing resistances of filter resistors of the filter, and the inverter operating frequency representing the inverter electrical frequency of a previous control cycle.

3. The power conversion system of claim 2, wherein the controller computes filter capacitor current values for steady state filter capacitor control compensation.

4. The power conversion system of claim 2, wherein the controller computes a filter capacitor current value for instantaneous filter capacitor control compensation.

5. The power conversion system of claim 1, wherein the controller computes a filter capacitor current value for steady state filter capacitor control compensation.

6. The power conversion system of claim 5, wherein the controller compensates the motor current reference value according to the capacitor currents of the output filter by:

computing an inverter current reference value as a sum of the filter capacitor current value and the motor current reference value;

computing the inverter output current reference value by subtracting an inverter current feedback value from the inverter current reference value; and

controlling the inverter at least partially according to the inverter output current reference value.

7. The power conversion system of claim 5, wherein the controller compensates the motor current reference value according to the capacitor currents of the output filter by:

computing a motor current feedback value by subtracting the filter capacitor current value from an inverter current feedback value;

computing the inverter output current reference value as a sum of the motor current feedback value and the motor current reference value; and

controlling the inverter at least partially according to the inverter output current reference value.

8. The power conversion system of claim 1, wherein the controller computes a filter capacitor current value for instantaneous filter capacitor control compensation.

9. The power conversion system of claim 8, wherein the controller compensates the motor current reference value according to the capacitor currents of the output filter by:

computing an inverter current reference value as a sum of the filter capacitor current value and the motor current reference value;

computing the inverter output current reference value by subtracting an inverter current feedback value from the inverter current reference value; and

controlling the inverter at least partially according to the inverter output current reference value.

10. The power conversion system of claim 8, wherein the controller compensates the motor current reference value according to the capacitor currents of the output filter by:

computing a motor current feedback value by subtracting the filter capacitor current value from an inverter current feedback value;

computing the inverter output current reference value as a sum of the motor current feedback value and the motor current reference value; and

controlling the inverter at least partially according to the inverter output current reference value.

11. The power conversion system of claim 8, wherein the controller computes d and q axis filter capacitor current values i_cap.comp.d and i_cap.comp.q according to the following equations:

19. The power conversion system of claim 11, wherein the controller computes filter capacitor current values according to filter output voltage values representing output voltages of the filter, capacitance values representing capacitances of filter capacitors of the filter, resistance values representing resistances of filter resistors of the filter, and the inverter operating frequency representing the inverter electrical frequency of a previous control cycle.

12. 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 output filter; and

a controller configured to;

compute a speed error value according to a speed reference value and a speed feedback value using a summing component;

compute a torque reference value according to the speed error value using a proportional-integral control component;

compute a motor current reference value according to the torque reference value using a lookup table or a parametric equation;

compensate the motor current reference value according to capacitor currents of the output filter by computing an inverter output current reference value according to the motor current reference value, an inverter operating frequency, a capacitance value of filter capacitor components of the output filter, and a resistance value of filter resistor components of the output filter; and

provide the inverter switching control signals to control the inverter according to the inverter output current reference value using a second proportional-integral control component;

wherein the controller computes d and q axis filter capacitor current values icap.comp.d and icap.comp.q according to the following equations;

13. A method of operating an inverter to drive a motor load through an output filter, the method comprising:

using at least one processor implementing a summing component, computing a speed error value according to a speed reference value and a speed feedback value;

using at least one processor implementing a first proportional-integral control component, computing a torque reference value according to the speed error value;

using at least one processor implementing a lookup table or a parametric equation, computing a motor current reference value according to the torque reference value;

using at least one processor, compensating the motor current reference value according to capacitor currents of the output filter by computing an inverter output current reference value according to the motor current reference value, an inverter operating frequency, a capacitance value of filter capacitor components of the output filter, and a resistance value of filter resistor components of the output filter; and

using at least one processor implementing a second proportional-integral control component, controlling the inverter according to the inverter output current reference value; and

using at least one processor, computing d and q axis filter capacitor current values icap.comp.d and icap.comp.q according to the following equations;

14. The method of claim 13, further comprising:

using at least one processor, computing filter capacitor current values according to filter output voltage values representing output voltages of the filter, capacitance values representing capacitances of filter capacitors of the filter, resistance values representing resistances of filter resistors of the filter, and the inverter operating frequency representing the inverter electrical frequency of a previous control cycle.

15. The method of claim 13, further comprising:

using at least one processor, computing a filter capacitor current value for steady state filter capacitor control compensation.

16. The method of claim 13, further comprising:

using at least one processor, computing a filter capacitor current value for instantaneous filter capacitor control compensation.

20. The power conversion system of claim 14, wherein the controller computes filter capacitor current values according to filter output voltage values representing output voltages of the filter, capacitance values representing capacitances of filter capacitors of the filter, resistance values representing resistances of filter resistors of the filter, and the inverter operating frequency representing the inverter electrical frequency of a previous control cycle.

17. A non-transitory computer readable medium, comprising instructions that, when executed by at least one processor, cause the at least one processor to operate an inverter to drive a motor load through an output filter by:

implementing a summing component to compute a speed error value according to a speed reference value and a speed feedback value;

implementing a first proportional-integral control component to compute a torque reference value according to the speed error value;

implementing a lookup table or a parametric equation to compute a motor current reference value according to the torque reference value;

compensating the motor current reference value according to capacitor currents of the output filter by computing an inverter output current reference value according to the motor current reference value, an inverter operating frequency, a capacitance value of filter capacitor components of the output filter, and a resistance value of filter resistor components of the output filter;

implementing a second proportional-integral control component to control the inverter according to the inverter output current reference value; and

computing d and q axis filter capacitor current values icap.comp.d and icap.comp.q according to the following equations;

18. The non-transitory computer readable medium of claim 17, comprising further computer executable instructions that, when executed by at least one processor, cause the at least one processor to compute filter capacitor current values according to filter output voltage values representing output voltages of the filter, capacitance values representing capacitances of filter capacitors of the filter, resistance values representing resistances of filter resistors of the filter, and the inverter operating frequency representing the inverter electrical frequency of a previous control cycle.