METHOD FOR VOLTAGE DIP COMPENSATION OF INVERTER

• US 20150357936A1
• Filed: 06/09/2015
• Published: 12/10/2015
• Est. Priority Date: 06/10/2014
• Status: Active Grant

• Current Assignee: LSIS Co. Ltd. (LS Corporation)
• Original Assignee: LSIS Co. Ltd. (LS Corporation)
• Inventors: JEON, Jae Hyun
• Granted Patent: US 9,525,363 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/325 with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
• CPC Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters

Abstract

Disclosed is a method for voltage dip compensation of inverter, the method including reducing an output frequency of an inverter to obtain a regenerative energy when it is determined that power failure has occurred during the inverter operation, adjusting increase/decrease of inverter output frequency in response to size of exceeding current and voltage based on an output current and DC-link voltage of the inverter, increasing the inverter output frequency in order to prevent excessive current flow when power restoration occurs at a power failure state, and returning to a speed prior to the momentary voltage dip by gradually increasing the inverter output frequency in a state where the inverter output frequency does not exceed an over-current limit by monitoring the inverter output frequency.

Claims

1. A method for voltage dip compensation of inverter, the method comprising:

performing a momentary voltage dip test for grasping a load characteristic of a load installed at a field site with a basic set point to cope with a momentary voltage dip;

determining whether a relevant load is a load that requires an additional current control in response to the grasped load characteristic;

setting the relevant load as a current control subject when it is determined that the relevant load is the current control subject as a result of determination, and setting the relevant load as not a current control subject when it is determined that the relevant load is not the current control subject as a result of determination;

setting to perform a momentary voltage dip compensation using voltage and current control on a relevant inverter when a momentary power failure occurs to a load set as the current control subject during inverter operation;

reducing an output frequency of an inverter to obtain a regenerative energy when it is determined that power failure has occurred during the inverter operation;

adjusting increase/decrease of inverter output frequency in response to size of exceeding current and voltage based on an output current and DC-link voltage of the inverter;

increasing the inverter output frequency in order to prevent excessive current flow when power restoration occurs at a power failure state; and

returning to a speed prior to the momentary voltage dip by gradually increasing the inverter output frequency in a state where the inverter output frequency does not exceed an over-current limit by monitoring the inverter output frequency.

2. The method of claim 1, wherein the step of determining whether the relevant load is a load that requires an additional current control in response to the grasped load characteristic further includes determining that a current control is additionally required when the load characteristic is not equal to a normalized load characteristic.

3. The method of claim 1, wherein the step of setting to perform the momentary voltage dip compensation includes setting to perform a momentary voltage dip compensation by controlling the inverter output frequency in response to current change using a set deceleration gradient while checking an output current in addition to checking a DC-link voltage of a load set for the current control subject when a power failure occurs.

4. The method of claim 1, wherein the step of setting to perform a momentary voltage dip compensation includes setting to perform a momentary voltage dip compensation by controlling the inverter output frequency in response to voltage change using a set deceleration gradient while checking a DC-link voltage of a load not set for the current control subject when a power failure occurs.

5. The method of claim 1, wherein the step of adjusting increase/decrease of inverter output frequency includes controlling adjustment of increase/decrease of the inverter output frequency for momentary voltage dip compensation in response to an output current change and DC-link voltage change using a set deceleration gradient while checking an inverter output current and DC-link voltage.

6. The method of claim 1, wherein the step of adjusting increase/decrease of inverter output frequency includes controlling adjustment of increase/decrease of the inverter output frequency for momentary voltage dip compensation in response to a voltage change using a set deceleration gradient while checking a DC-link voltage of the inverter.

7. The method of claim 1, wherein the step of returning to the speed prior to the momentary voltage dip includes maintaining an output frequency at the time of power restoration for a predetermined time lest the inverter output current should exceed a predetermined over-current limit.

8. The method of claim 7, wherein a time for maintaining the output frequency is set by being determined in advance in response to a load amount of the load.

9. The method of claim 7, wherein a time for maintaining the output frequency is determined to maintain an output frequency so that a load speed becomes smaller than an output frequency of the inverter.