Multilevel inverter using cascade configuration and control method thereof

Abstract

A multilevel inverter using a cascade configuration with a device for equally controlling a power factor for each unit cell includes: a master controller, a plurality of power cells connected in series for each of three AC (Alternating Current) phases, a phase shift transformer for supplying a power cell input voltage, a CAN (Controller Area Network) communication network to provide a communication path between the master controller and each power cell, and cell controllers to control output voltages and output frequencies of the respective power cells according to a voltage command and a frequency command from the master controller, each cell controller having a pulse width modulator to generate a pulse width modulation control signal of a variable voltage and a variable frequency to the connected corresponding power cell, wherein each cell controller is configured to calculate a phase difference value of the corresponding power cell according to a preset total number of connected power cells and the floor number (i.e., the serial connection sequence) of the corresponding power cell to thereafter phase-shift a chopping wave by the calculated phase difference value, thereby compensating for the phase differences between each power cell.

Description

technical field [0001] The present invention relates to a high-voltage inverter, and more particularly, to a multi-level inverter using a cascade structure and a control method thereof, the inverter having means for equally controlling the power factors of a plurality of power units. Background technique [0002] Generally, a multi-level inverter using a cascade structure is a multi-level topology of high-voltage, large-capacity inverters, in which several single-phase inverters (hereinafter referred to as power units) are connected in series for three-phase currents. Each phase, therefore high voltages can be obtained using low voltage power semiconductor switches in the power cells. [0003] In this way, by connecting a plurality of single-phase power cells in series to each AC (alternating current) phase, a multi-level inverter employing a cascade structure can obtain high voltages using semiconductor switches. [0004] Also, the multilevel inverter adopting the cascade ...

AI Technical Summary

Problems solved by technology

Especially for small loads, if the difference in power factor is not compensated, the regenerative voltage is concentrated to a specific (power) unit, which will cause problems or burn out of the corresponding unit, resulting in a multi-level power supply using a cascaded structure Inverter driving becomes impossible

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