Cascade connection polyphase converter

Abstract

The invention relates to a cascade connection polyphase converter. The cascade connection polyphase converter comprises more than two basic power units, and the basic power units are supplied with electric source by a single-phase electric source. Each of the basic power units comprises an H-bridge power inverter. The input end of the H-bridge power inverter is connected with the electric networkin a cascade connection manner, and the output end thereof is connected with a polyphase power inverter back to back by a direct current bus. The polyphase power inverter is connected with a polyphase alternating current motor. A control unit interacts information with the H-bridge power inverter. By taking the H-bridge power inverter as the access of the electric network, the invention can facilitate the input current harmonic wave of the electric network to be small and basically accordant with the input voltage phase by a control mode, the power factor is approximately equal to 1. The invention improves the working efficiency of the complete machine in the system. The invention can be widely used in the field of medium-high voltage high-capacity polyphase speed regulation.

Description

technical field [0001] The invention relates to a multi-phase and multi-level topological structure of power electronics, in particular to a cascaded multi-phase converter applied in the field of high-voltage and large-capacity speed regulation. Background technique [0002] With the application of frequency conversion devices in high-voltage and large-capacity speed regulation fields such as ship electric propulsion and electric locomotive traction, due to the limitation of power device withstand voltage level and current carrying capacity, the conversion device of traditional two-level three-phase inverter It is difficult to meet the requirements of high-voltage and high-power electric energy conversion. Therefore, multi-phase multi-level technology is a very good method to solve the current power device constraints system capacity increase, and is considered by the industry to have broad application prospects in the field of high voltage and large capacity. Multi-phase m...

AI Technical Summary

Problems solved by technology

However, there are also some problems in this topology converter: the power unit adopts an uncontrolled rectification circuit, the electric energy can only flow from the grid to the load, and the four-quadrant operation of the motor system cannot be realized, that is, the energy is fed back to the grid; at the same time, when the power is large, In the case of a large number of motor phases, a phase-shifting isolation transformer with a large capacity is required

However, the improvement of the circuit still requires a phase-shifting transformer, and the disadvantages of large volume, weight, and high cost have not changed.

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