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AC MOTOR DRIVE SYSTEM

  • US 20170149369A1
  • Filed: 06/19/2014
  • Published: 05/25/2017
  • Est. Priority Date: 06/19/2014
  • Status: Active Grant
First Claim
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1. An AC motor drive system comprising:

  • a converter that supplies DC power;

    an inverter that converts the DC power into AC power;

    a DC bus that connects the converter and the inverter;

    an AC motor that is driven by the AC power;

    a DC voltage value detector that detects a DC voltage value on an output side of the converter;

    a power storage device that stores the DC power from the DC bus and releases the stored DC power to the DC bus;

    a charging and discharging circuit that is connected to the DC bus and is in parallel with the inverter, and charges and discharges the power storage device;

    a charging and discharging current value detector that detects a charging and discharging current value of the power storage device; and

    a charge and discharge controller that outputs a control signal to control the charging and discharging circuit on a basis of the DC voltage value and the charging and discharging current value, whereinwhen regenerative power from the AC motor via the inverter exceeds a predetermined power threshold, the charge and discharge controller causes the power storage device to be charged such that the DC voltage value becomes a voltage threshold corresponding to the power threshold,when the regenerative power is lower than or equal to the power threshold, the converter performs a regeneration operation when the DC voltage value rises to reach a predetermined regeneration start voltage threshold and ends the regeneration operation when the DC voltage value drops to reach a predetermined regeneration end voltage threshold, anda time average value of the DC voltage value during the regeneration operation in the converter is lower than the DC voltage value at no-load time when the converter does not perform power supply and regeneration, andthe charge and discharge controller maintains constant current with which the power storage device is charged only during a period based on a cycle in which the DC bus voltage value reaches a voltage threshold based on a DC bus voltage value at which the converter starts the regeneration operation.

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