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Converter and a method for controlling a converter

  • US 6,995,994 B2
  • Filed: 09/17/2002
  • Issued: 02/07/2006
  • Est. Priority Date: 09/21/2001
  • Status: Expired due to Fees
First Claim
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1. A converter comprising:

  • a series connection of at least two current valves (2, 3) arranged between two poles (4, 5), a positive and a negative, of a direct voltage side of the converter, each of which current valves comprising at least one circuit (12) provided with a semiconductor component (13a, 13b) of turn-off type and a rectifying component (14a, 14b) connected in anti-parallel therewith, an alternating voltage phase line (11) being connected to a mid-point (10), denominated phase output, of the series connection between two current valves while dividing the series connection into two equal parts (1a, 1b),a resonant circuit (16) comprising snubber capacitors (15), which are connected in parallel with a respective one of the semiconductor components (13a, 13b) of turn-off type of the current valves, and at least one inductor (17) and an auxiliary valve (18) provided with semiconductor components (20a, 20b) of turn-off type for recharging said snubber capacitors (15) in connection with a commutation of the phase current, anda control device (24) for controlling the turn-on and turn-off of the semiconductor components (13a, 13b) of turn-off type of the current valves, wherein the converter comprises a device (31) for measuring the derivative (dI/dt) of the current through the current valves (2, 3), and a detection device (32) co-operating with said measuring device (31) for detecting a short-circuit in the converter, the detection device (32) being adapted to detect a short-circuit current when the current derivative (dI/dt) measured by the measuring device (31) is equal to or exceeds a stipulated current derivative limit value (dI/dtlim) during a length of time exceeding a stipulated time limit value (tlim).

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