Apparatus and method for restarting medium voltage inverter

• US 9,768,679 B2
• Filed: 09/25/2015
• Issued: 09/19/2017
• Est. Priority Date: 10/15/2014
• Status: Active Grant

• Current Assignee: LSIS Co. Ltd. (LS Corporation)
• Original Assignee: LSIS Co. Ltd. (LS Corporation)
• Inventors: Chae, Beom Seok, Choi, Seung Cheol
• Primary Examiner(s): Leykin, Rita
• Application Number:
  US14/866,690
• Publication Number:
  US 20160111953A1
• Time in Patent Office: 725 Days
• Field of Search: 318503, 318727, 318700, 31840001, 31840004, 318606, 318607, 318148, 318723, 318807, 318827, 361157, 327 8, 327 9, 324166
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02P 1/028 wherein the motor voltage is increased at low speed, to start or restart high inertia loads
• CPC Class Codes: H02P 1/029 Restarting, e.g. after power failure
• CPC Class Codes: H02P 21/14 Estimation or adaptation of machine parameters, e.g. flux, current or voltage
• CPC Class Codes: H02P 21/18 Estimation of position or speed
• 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 27/047 V/F converter, wherein the voltage is controlled proportionally with the frequency
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence

Abstract

An apparatus for restarting a medium voltage inverter is disclosed, wherein the medium voltage inverter can be restarted by estimating a rotor speed when an input power returns from an instantaneous defective state to a normal state, whereby a time to restart the medium voltage inverter can be reduced by a simple configuration to dispense with the need to wait until the rotor speed reaches zero speed.

Claims

1. An apparatus for restarting a medium voltage inverter, the apparatus comprising:

a measurement unit configured to measure an induced voltage of a motor;

an estimation unit configured to estimate a rotor speed of the motor using the induced voltage; and

a controller configured to controllably change an output voltage or an output frequency of the inverter in response to a first ratio corresponding to a frequency relative to a predetermined voltage using the induced voltage and the rotor speed,

wherein the estimation unit includes;

a generation unit configured to generate a first voltage corresponding to a frequency applied by the medium voltage inverter from an induced voltage of the motor by the inverter and a second voltage substantially lagging by 90°

in phase from the first voltage,

a determination unit configured to determine a control bandwidth for determining a frequency of the induced voltage of the motor,

a second detection unit configured to determine the rotor speed based on the control bandwidth; and

a normalization unit configured to normalize the first and second voltages as separate voltages generated by the generation unit.

2. The apparatus of claim 1, wherein the controller maintains an output frequency of the inverter and increases the output voltage until a second ratio reaches the first ratio when the second ratio corresponding to the rotor speed relative to the induced voltage is smaller than the first ratio.

3. The apparatus of claim 2, wherein the controller increases the output voltage and output frequency of the inverter in response to the first ratio when the second ratio reaches the first ratio.

4. The apparatus of claim 1, wherein the controller maintains an output voltage of the inverter and increases the output frequency until the second ratio reaches the first ratio when the second ratio corresponding to the rotor speed relative to the induced voltage is greater than the first ratio.

5. The apparatus of claim 4, wherein the controller increases the output voltage and output frequency of the inverter in response to the first ratio when the second ratio reaches the first ratio.

6. A method for restarting a medium voltage inverter, the method comprising:

generating a first voltage corresponding to a frequency applied by the medium voltage inverter from an induced voltage of a motor and a second voltage substantially lagging by 90°

in phase from the first voltage;

determining a control bandwidth to determine a frequency of an output voltage of the motor;

estimating a rotor speed of the motor based on the control bandwidth; and

normalizing the first and second generated voltages as separate voltages.

7. The method of claim 6, further comprising:

maintaining an output frequency of the inverter and increasing an output voltage until a second ratio reaches a first ratio when the first ratio corresponding to a frequency relative to a predetermined voltage is smaller than the second ratio corresponding to the rotor speed relative to the induced voltage.

8. The method of claim 7, further comprising:

increasing the output voltage and the output frequency of the inverter in response to the first ratio when the second ratio reaches the first ratio.

9. The method of claim 6, further comprising:

maintaining an output voltage of the inverter and increasing an output frequency until a second ratio reaches a first ratio when the first ratio corresponding to a frequency relative to a predetermined voltage is greater than the second ratio corresponding to the rotor speed relative to the induced voltage.

10. The method of claim 9, further comprising:

increasing the output voltage and the output frequency of the inverter in response to the first ratio when the second ratio reaches the first ratio.