Converter unit system having inrush-current suppression circuit

Patent metadata

Field	Value
Publication number	US-9876438-B2
Application number	US-201515118949-A
Country	US
Kind code	B2
Filing date	Mar 19, 2015
Priority date	Mar 19, 2015
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

In a converter unit system, converter units are connected in parallel. The converter unit includes a converter circuit connected to an AC power supply and a DC bus, a first inrush-current suppression resistor connected to the DC bus, a first contactor connected in parallel to the first inrush-current suppression resistor, a smoothing capacitor provided after the first inrush-current suppression resistor and the first contactor, a second contactor externally outputting ON/OFF signal, a voltage detection unit measuring a DC voltage value across the smoothing capacitor, and a control unit controlling the first contactor and the second contactor. The converter unit system includes a third contactor connected to the converter units, and a second inrush-current suppression resistor connected in parallel to the third contactor. When contacts of the second contactors are all closed, a contact of the third contactor is closed.

First claim

The invention claimed is:

1. A converter unit system comprising:
a first converter unit connected in parallel to a second converter unit, wherein each of the first and second converter units is connected to an AC power supply and a DC bus, and comprises:
a converter circuit that rectifies an AC voltage input from the AC power supply to a DC voltage, and outputs the DC voltage to the DC bus;
a first inrush-current suppression resistor that is connected to the DC bus;
a first contactor that is connected in parallel to the first inrush-current suppression resistor;
a smoothing capacitor that is provided on the DC bus on a side further from the AC power supply than the first inrush-current suppression resistor and the first contactor;
a second contactor that outputs an ON signal or an OFF signal to an external source;
a voltage detection unit that measures a value of the DC voltage across both ends of the smoothing capacitor;
a control unit that controls the first contactor and the second contactor on a basis of the value of the DC voltage detected by the voltage detection unit;
a third contactor that is connected to the first converter unit and the second converter unit and to the AC power supply; and
a second inrush-current suppression resistor that is connected in parallel to the third contactor,
wherein a contact of the second contactor of the first converter unit is connected to one side of a coil of the third contactor,
a contact of the second contactor of the second converter unit is connected to other side of the coil of the third contactor,
the second contactor of the first converter unit is connected in series with the second contactor of the second converter unit,
a contact of the third contactor is closed in response to the coil of the third contactor being energized by current flowing through the coil when the contacts of the second contactor of the first converter unit and the second converter unit are closed, and
the contact of the third contactor is opened when at least one among the contact of the second contactor of the first converter unit and the contact of the second contactor of the second converter unit is opened, thereby de-energizing the coil of the third contactor.

2. The converter unit system according to claim 1 , wherein
at a time of power-on, the control unit outputs a signal for closing a contact of the first contactor after a lapse of a first predetermined time since the DC voltage across the both ends of the smoothing capacitor becomes equal to or higher than a first predetermined value, and, outputs a signal for closing the contact of the second contactor after a lapse of a second predetermined time since the control unit outputs the signal for closing the contact of the first contactor, and
at a time of power-off, the control unit outputs a signal for opening the contact of the second contactor when the DC voltage across the both ends of the smoothing capacitor becomes equal to or lower than a second predetermined value, and, outputs a signal for opening the contact of the first contactor after a lapse of a third predetermined time since the control unit outputs the signal for opening the contact of the second contactor.

3. The converter unit system according to claim 1 , wherein
at a time of power-on, the control unit outputs a signal for closing a contact of the first contactor after a lapse of a first predetermined time since the DC voltage across the both ends of the smoothing capacitor becomes equal to or higher than a first predetermined value, and, outputs a signal for closing the contact of the second contactor after a lapse of a second predetermined time since the DC voltage across the both ends of the smoothing capacitor becomes equal to or higher than a first value that is obtained by adding a predetermined first voltage value to the first predetermined value, and
at a time of power-off, the control unit outputs a signal for opening the contact of the second contactor when the DC voltage across the both ends of the smoothing capacitor becomes equal to or lower than a second predetermined value, and outputs a signal for opening the contact of the first contactor when the DC voltage across the both ends of the smoothing capacitor becomes equal to or lower than a second value that is obtained by subtracting a predetermined second voltage value from the second predetermined value.

4. A converter unit comprising:
a first converter unit connected in parallel to a second converter unit, each of the first and second converter units including:
a converter circuit that rectifies an AC voltage input from an AC power supply to a DC voltage and outputs the DC voltage to a DC bus;
a first inrush-current suppression resistor that is connected to the DC bus;
a first contactor that is connected in parallel to the first inrush-current suppression resistor;
a smoothing capacitor that is provided on the DC bus on a side further from the AC power supply than the first inrush-current suppression resistor and the first contactor;
a second contactor that outputs an ON signal or an OFF signal to an external source;
a voltage detection unit that measures a value of the DC voltage across both ends of the smoothing capacitor; and
a control unit that controls the first contactor and the second contactor on a basis of the value of the DC voltage detected by the voltage detection unit,
wherein the second contactor of the first converter unit is connected in series with the second contactor of the second converter unit and connected to a third contactor and a second inrush-current suppression resistor that are disposed in parallel,
a contact of the second contactor of the first converter unit is connected to one side of a coil of the third contactor,
a contact of the second contactor of the second converter unit is connected to other side of the coil of the third contactor,
a contact of the third contactor is closed in response to the coil of the third contactor being energized by current flowing through the coil when the contact of the second contractors of the first converter unit and the second converter unit are closed, and
the contact of the third contactor is opened when at least one among the contact of the second contactor of the first converter unit and the contact of the second contactor of the second converter unit is opened, thereby de-energizing the coil of the third contactor.

5. The converter unit according to claim 4 , wherein
at a time of power-on, and after a lapse of a first predetermined time since the DC voltage across the both ends of the smoothing capacitor becomes equal to or higher than a first predetermined value, the control unit outputs a signal for closing a contact of the first contactor, and
at a time of power-off, when the DC voltage across the both ends of the smoothing capacitor becomes equal to or lower than a second predetermined value, the control unit outputs a signal for opening the contact of the first contactor.

6. The converter unit according to claim 4 , wherein
at a time of power-on, the control unit outputs a signal for closing a contact of the first contactor after a lapse of a first predetermined time since the DC voltage across the both ends of the smoothing capacitor becomes equal to or higher than a first predetermined value, and, outputs a signal for closing the contact of the second contactor after a lapse of a second predetermined time since the control unit outputs the signal for closing the contact of the first contactor, and
at a time of power-off, the control unit outputs a signal for opening the contact of the second contactor when the DC voltage across the both ends of the smoothing capacitor becomes equal to or lower than a second predetermined value, and, outputs a signal for opening the

Assignees

• Mitsubishi Electric Corp

Inventors

• Kato Masanori

Classifications

• H02M1/36

  Means for starting or stopping converters · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02P27/06

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

• H02M5/458

  using semiconductor devices only · CPC title

• H02M7/08 Primary

  arranged for operation in parallel · CPC title