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

Patent metadata

Field	Value
Publication number	US-2016173012-A1
Application number	US-201615053135-A
Country	US
Kind code	A1
Filing date	Feb 25, 2016
Priority date	Jan 16, 2013
Publication date	Jun 16, 2016
Grant date	—

Abstract

Disclosed examples include methods, computer readable mediums and motor drives power conversion systems for sensorless speed control of a motor driven by an inverter through an intervening filter, in which a controller computes motor current feedback values for a current control cycle according to inverter output current values, capacitance values representing capacitances of filter capacitors of the filter, filter output voltage values representing output voltages of the filter, and a speed feedback or reference value of a previous control cycle. The controller computes a speed feedback value for the current control cycle according to the motor current feedback values and the filter output voltage values, and controls the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback or reference value using vector control.

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 through an intervening filter; and a controller configured to:
compute motor current feedback values for a current control cycle according to inverter output current values, capacitance values representing capacitances of filter capacitors of the filter, filter output voltage values representing output voltages of the filter, and a speed reference or feedback value of a previous control cycle,
compute a speed feedback value for the current control cycle according to the motor current feedback values and the filter output voltage values, and
control the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback value using vector control.

2 . The power conversion system of claim 1 , wherein the filter output voltage values are line-line voltages measured at an output of the filter.

3 . The power conversion system of claim 1 , wherein the controller is configured to implement a current control function to compute voltage command values to generate the inverter switching control signals, and to compute the filter output voltage values according to voltage command values.

4 . The power conversion system of claim 3 , wherein the controller is configured to compute the filter output voltage values as line-line voltages according to a set of phase voltage command values.

5 . The power conversion system of claim 1 , wherein the filter capacitors of the filter are connected in a delta configuration, and wherein the controller is configured to compute the motor current feedback values i a.m ; i b.m and i c.m for filter output phases a, b and c in the current control cycle according to the following equations:
i a.m= i u− ω*C f *(3) 1/2 *V bc ; i b.m= i v− ω*C f *(3) 1/2 *V ca ; and i c.m= i u− ω*C f *(3) 1/2 *V ab ; wherein i u , i v and i w are the inverter output current values for inverter output phases u, v and w, ω is the angular frequency of inverter output voltage commands, C f is the capacitance of the filter capacitors, and V ab , V bc and V ca are the filter output voltage values representing line-line output voltages of the filter.

6 . The power conversion system of claim 1 , wherein the filter capacitors of the filter are connected in a Y configuration, and wherein the controller is configured to compute the motor current feedback values i a.m , i b.m and i c.m for filter output phases a, b and c in the current control cycle according to the following equations:
i a.m= i u− ω*C f *(3) −1/2 *V bc ; i b.m= i v− ω*C f *(3) −1/2 *V ca ; and i c.m= i u− ω*C f *(3) −1/2 *V ab ; wherein i u , i v and i w are the inverter output current values for inverter output phases u, v and w, ω is the angular frequency of the inverter output voltage commands, C f is the capacitance of the filter capacitors, and V ab , V bc and V ca are the filter output voltage values representing line-line output voltages of the filter.

7 . The power conversion system of claim 1 , wherein the controller is configured to compute the speed feedback value for the current control cycle using an emf-based observer according to the motor current feedback values and the filter output voltage values.

8 . The power conversion system of claim 1 , wherein the controller is configured to:
compute a speed error value according to a speed reference value and the speed feedback value; compute a torque reference value according to the speed error value; compute a current reference value according to the torque reference value; compute an inverter output reference value according to the motor current reference value and the motor current feedback values; and provide the inverter switching control signals to control the inverter to regulate the rotational speed of the motor according to the inverter output reference value.

9 . A method for sensorless speed control of a motor driven by an inverter through an intervening filter, the method comprising:
using at least one processor, computing motor current feedback values for a current control cycle according to inverter output current values, capacitance values representing capacitances of filter capacitors of the filter, filter output voltage values representing output voltages of the filter, and a speed feedback or reference value of a previous control cycle; using the at least one processor, computing a speed feedback value for the current control cycle according to the motor current feedback values and the filter output voltage values; and using the at least one processor, controlling the inverter to regulate the rotational speed of the motor at least partially according to the speed feedback value using vector control.

10 . The method of claim 9 , comprising measuring the filter output voltage values as line-line voltages at an output of the filter.

11 . The method of claim 9 , comprising, using the at least one processor, implementing a current control function to compute voltage command values to generate the inverter switching control signals, and computing the filter output voltage values according to voltage command values.

12 . The method of claim 11 , comprising, using the at least one processor, computing the filter output voltage values as line-line voltages according to a set of phase voltage command values.

13 . The method of claim 9 , wherein the filter capacitors of the filter are connected in a delta configuration, comprising, using the at least one processor, computing the motor current feedback values i a.m , i b.m and i c.m for filter output phases a, b and c in the current control cycle according to the following equations:
i a.m= i u− ω*C f *(3) 1/2 *V bc ; i b.m= i v− ω*C f *(3) 1/2 *V ca ; and i c.m= i u− ω*C f *(3) 1/2 *V ab ; wherein i u , i v and i w are the inverter output current values for inverter output phases u, v and w, ω is the angular frequency of inverter output voltage commands, C f is the capacitance of the filter capacitors, and V ab , V bc and V ca are the filter output voltage values representing line-line output voltages of the filter.

14 . The method of claim 9 , wherein the filter capacitors of the filter are connected in a Y configuration, comprising, using the at least one processor, computing the motor current feedback values i a.m , i b.m and i c.m for filter output phases a, b and c in the current control cycle according to the following equations:
i a.m= i u− ω*C f *(3) −1/2 *V bc ; i b.m= i v− ω*C f *(3) −1/2 *V ca ; and i c.m= i u− ω*C f *(3) −1/2 *V ab ; wherein i u , i v and i w are the inverter output current values for inverter output phases u, v and w, ω is the angular frequency of inverter output voltage commands, C f is the capacitance of the filter capacitors, and V ab , V bc and V ca are the filter output voltage values representing line-line output voltages of the filter.

15 . The method of claim 9 , comprising, using the at least one processor, computing the speed feedback value for the current control cycle using an emf-

Assignees

• Rockwell Automation Tech Inc

Inventors

• Nondahl Thomas A
• Royak Semyon
• Liu Jingbo
• Dai Jingya
• Al-Nabi Ehsan
• Schmidt Peter B

Classifications

• H02P27/06 Primary

  using DC to AC converters or inverters (H02P27/05 takes precedence) · CPC title

• H02P6/08 Primary

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• H02M7/53876

  based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times · CPC title

• H02M1/126

  using passive filters · CPC title

• H02M7/53873

  with digital control · CPC title