Converter and power conversion device having an imbalance detection unit

Patent metadata

Field	Value
Publication number	US-9641094-B2
Application number	US-201515114464-A
Country	US
Kind code	B2
Filing date	Mar 11, 2015
Priority date	Mar 11, 2015
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A converter includes a converter circuit that converts the AC voltages supplied from the Δ-connection and the Y-connection, which are two systems of a 12-phase rectifier transformer, to a DC voltage; a current detector that detects the current in a DC bus output from the converter circuit; and an imbalance detection unit that detects the occurrence of an imbalance between the current output from the Δ-connection and the current output from the Y-connection, the currents being detected by the current detector. The converter can detect an imbalance that occurs between the current flowing in the diode bridge on the Δ-connection side and the current flowing in the diode bridge on the Y-connection side.

First claim

The invention claimed is:

1. A converter comprising:
a converter circuit that converts an AC voltage supplied from a Δ-connection and a Y-connection, which are two systems of a 12-phase rectifier transformer, to a DC voltage;
a current detector that detects a current in a DC bus output from the converter circuit; and
an imbalance detection unit that detects occurrence of imbalance between a current output from the Δ-connection and detected by the current detector and a current output from the Y-connection and detected by the current detector, wherein
the imbalance detection unit includes
a DC-current detection unit that detects a DC current on the basis of a detection value detected by the current detector,
a peak-value detection unit that detects a peak value of the DC current,
a bottom-value detection unit that detects a bottom value of the DC current,
a difference detection unit that detects a difference between the peak value and the bottom value,
a setting unit that sets a threshold for a difference between the peak value and the bottom value of the DC current,
a comparison unit that compares a threshold set by the setting unit with the difference detected by the difference detection unit, and
a signal output unit that outputs an alarm signal when a result of a comparison made by the comparison unit is detected by the difference detection unit as a difference that exceeds the threshold set by the setting unit.

2. A converter comprising:
a converter circuit that converts an AC voltage supplied from a Δ-connection and a Y-connection, which are two systems of a 12-phase rectifier transformer, to a DC voltage;
a current detector that detects a current in a DC bus output from the converter circuit; and
an imbalance detection unit that detects occurrence of imbalance between a current output from the Δ-connection and detected by the current detector and a current output from the Y-connection and detected by the current detector, wherein
the imbalance detection unit includes
a DC-current detection unit that detects a DC current on the basis of a detection value detected by the current detector,
a ripple-frequency calculation unit that calculates a ripple frequency of a DC current detected by the DC-current detection unit,
a mean-value calculation unit that calculates a mean value of a DC current detected by the DC-current detection unit,
a setting unit that sets a threshold,
a current-imbalance detection unit that, when a ripple frequency of a DC current calculated by the ripple-frequency calculation unit is other than 12 times a value of a power-supply voltage frequency and when a mean value of a DC current calculated by the mean-value calculation unit exceeds a threshold set by the setting unit, detects occurrence of current imbalance on the basis of a detection value detected by the current detector, and
a signal output unit that outputs an alarm signal when current imbalance is detected by the current-imbalance detection unit.

3. A power conversion device comprising:
the converter according to claim 1 ; and
an inverter that receives an alarm signal output from the converter.

Assignees

• Mitsubishi Electric Corp

Inventors

• Kato Masanori

Classifications

• H02M7/08 Primary

  arranged for operation in parallel · CPC title

• H02M5/458

  using semiconductor devices only · CPC title

• H02P27/06

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

• H02M7/06 Primary

  using discharge tubes without control electrode or semiconductor devices without control electrode · CPC title

• H02M1/14

  Arrangements for reducing ripples from DC input or output · CPC title