Power unit for cascade apparatus

Abstract

A novel power unit of a cascade unit comprises a DC voltage driver unit, a voltage lifting chopping part and an inverting part. The DC voltage drive of the power unit adopts a three-phase bridge type uncontrolled rectifier system, and two controllable IGBTs and two fast diodes are added at the DC side, thus forming a DC voltage lifting chopping circuit which can control the voltage at the DC link and broaden the scope of AC output voltage amplitude; an inverter adopts IGBT single-phase full bridge controllable output, and a fault bypass circuit is added at the output terminal of the inverter; and a rectifier transformer is of common wiring multi-winding type, and all secondary windings have the same wiring mode. A voltage lifting half-bridge and a neutral point in a filter capacitor set are connected with the neutral point in a harmonic current circuit to provide a channel for injecting zero sequence current so as to achieve the sinusoid of high power factor rectification and the input current.

Description

technical field [0001] The invention relates to a power unit of a cascaded device, in particular to a power unit capable of controlling DC voltage and realizing high power factor rectification. The invention belongs to the technical field of power electronics. Background technique [0002] In the application of high-power conversion, people hope that high-power, high-voltage power electronic devices can work at the highest possible switching frequency to better filter out harmonics and improve the quality of output waveforms. But too high switching frequency will lead to large switching loss, so it is difficult to apply PWM technology to traditional large-capacity converters to improve their performance. Therefore, people try to improve the performance of the power electronic converter while improving the capacity of the power electronic converter by studying the circuit topology and control strategy of the high-power converter. A good circuit topology combined with a bett...

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Problems solved by technology

[0007] However, the above two topologies have disadvantages that are difficult to overcome: topology (1) cannot directly control the voltage of the DC link, and the manufacturing of the rectifier transformer is complicated, and it is difficult to overcome the problem of voltage asymmetry caused by manufacturing; the rectifier bridge of topology (2) uses six The fully controlled device IGBT not only increases the cost, but also increases the difficulty of measurement and control

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