CSI based drive having feedforward control of inverter input voltage

• US 6,269,010 B1
• Filed: 02/29/2000
• Issued: 07/31/2001
• Est. Priority Date: 02/29/2000
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company LLC (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Technologies, LLC (Teledyne Technologies Incorporated)
• Inventors: Wu, Bin, Zargari, Navid R., Rizzo, Steven C., Ma, Daming
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Laxton, Gary L.
• Application Number:
  US09/516,974
• Time in Patent Office: 518 Days
• Field of Search: 363/34, 363/35, 363/37, 363/89, 363/127, 363/97, 363/131, 363/135, 363/137, 363/138, 363/98
• US Class Current: 363/35
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 5/4505 having a rectifier with controlled elements

Abstract

The drive for an a.c. induction motor features a rectifier for converting alternating current into direct current and a current source inverter for converting direct current into alternating current supplied to a motor. A d.c. link choke interconnects the rectifier and the inverter. The inverter includes a first control loop which provides a desired or command d.c. link choke current to a second control loop responsible for the rectifier. For the purposes of the second control loop the actual d.c. link choke current and an input voltage of the inverter are detected. The difference or error between the desired and actual d.c. choke currents are minimized by a compensator. The output of the compensator is added to the detected inverter input voltage, and the sum is fed to a switching pattern generator which controls the switches in the rectifier. In this manner the feedback of the inverter input voltage is decoupled from the compensator responsible for the d.c. link choke current. This makes the parameters of the second control loop substantially independent of the load, thereby enhancing the ease with which the control loop may be tuned and hence the stability of the drive.

Claims

1. A motor drive, comprising:

a rectifier for converting alternating current into direct current;

a current source inverter for converting direct current into alternating current;

a d.c. link choke interconnecting the rectifier and the inverter;

an inverter controller for controlling the inverter, said controller generating a desired d.c. link choke current;

means for determining a d.c. input voltage of the inverter or current required thereby and generating a voltage or current based output signal;

means for determining the actual d.c. link current;

a rectifier controller, including a compensator receiving as inputs the desired and actual d.c. link currents, a summer for adding the output of the compensator and the output signal of the means for determining the d.c. input voltage of the inverter or current required thereby, and a switching pattern generator, receiving the output of the summer, for controlling switches in the rectifier.

2. The drive according to claim 1, wherein said means for determining the d.c. input voltage of the inverter or current required thereby includes one of a sensor and means for calculating the d.c. input voltage of the inverter based on the output voltage of the inverter.

3. The drive according to claim 2, wherein the output signal of the means for determining the d.c. input voltage of the inverter or current required thereby is the d.c. input voltage of the inverter, and the output of the summer is a voltage signal.

4. The drive according to claim 2, wherein the output signal of the means for determining the d.c. input voltage of the inverter or current required thereby is a current signal and the output of the summer is a current signal.

5. The drive according to claim 4, wherein the means for determining a d.c. input voltage of the inverter or current required thereby includes a multiplier for multiplying the d.c. input voltage of the inverter by the actual d.c. link current and a divider for dividing the output of the multiplier by an input voltage of the rectifier.

6. A method for operating a motor drive comprising a current source inverter connected to a rectifier via a d.c. link choke, wherein a controller associated with the inverter generates a desired d.c. link current, said method including:

determining the actual d.c. link current;

determining a d.c. input voltage of the inverter or current required by the inverter;

generating a signal from a minimizing compensator which receives as inputs the desired and actual d.c. link currents;

adding the value of the inverter input voltage or current required by the inverter to the compensator signal to produce a reference signal; and

establishing a switching pattern for switches of the rectifier based on the reference signal.

7. The method according to claim 6, wherein the step of determining the inverter d.c. input voltage or current required by the inverter includes one of measuring the inverter d.c. input voltage with a sensor and calculating the inverter d.c. input voltage based on the output voltage of the inverter.

8. The method according to claim 6, wherein in step 6(b) the inverter d.c. input voltage is determined, the signal produced from the compensator is a voltage signal, and the reference signal is a voltage signal.

9. The method according to claim 6, wherein in step 6(b) the current required by the inverter is determined, the signal produced from the compensator is a current signal, and the reference signal is a current signal.

10. The method according to claim 9, wherein the step of determining the current required bv the inverter includes multiplying the inverter input voltage by the actual d.c. link current and dividing the result by an input voltage of the rectifier, the result being added to the compensator signal so as to determine the reference signal.