Power conversion device

Abstract

Absorption of a regenerative current and direct AC power conversion are made compatible with each other in a power converting apparatus. A converter (4) and an inverter (6) are connected via a clamp circuit (5). The converter (4) performs commutation in accordance with any of a first commutation mode in which trapezoidal waves are compared with a carrier and a 120-degree conduction mode. A diode (Dc1) of the clamp circuit (5) is short-circuited by a shorting switch (Qc1). The shorting switch (Qc1) is rendered conductive when a power factor reduces or a power supply voltage reduces, and capacitors (51) and (52) of the clamp circuit (5) are connected in series between DC power supply lines (LH, LL). The converter (4) performs commutation in accordance with the 120-degree conduction mode, not in accordance with the first commutation mode, while the shorting switch (Qc1) is conductive.

Description

Technical field [0001] The present invention relates to a power conversion device, and more particularly to a direct AC power conversion device of a clamp circuit (including a buffer). Background technique [0002] As a representative main circuit structure of the inverter, a so-called indirect AC power conversion circuit is generally used. In an indirect AC power conversion circuit, AC is rectified, converted into DC via a smoothing circuit, and AC output is obtained through a voltage-type converter. [0003] On the other hand, as a method of directly obtaining AC output from AC voltage, a direct AC power conversion device represented by a matrix converter is known. Direct AC power conversion devices do not require large capacitors and / or reactors for smoothing voltage ripples caused by commercial frequencies. Therefore, miniaturization of converters can be expected. In recent years, they have attracted attention as next-generation power converters. [0004] For example, Patent Do...

AI Technical Summary

Problems solved by technology

[0025] However, with the position detection method shown in Patent Document 6, the clamp circuit of Patent Document 5 cannot sufficiently cope with the operation in which the power factor is greatly reduced.

Also, since position detection is usually performed at startup, the clamp voltage in the DC link may become overvoltage, making startup difficult

[0026] In addition, in the event of an instantaneous power failure as described in Patent Document 7, it may be difficult to continue operation due to insufficient clamp voltage.

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