| 摘要 |
A multilevel inverter using a cascade configuration with a device for equally controlling a power factor for each unit cell includes: a master controller (1), a plurality of power cells (4-1,4-2,...,4-n) connected in series for each of three AC (Alternating Current) phases, a phase shift transformer for supplying a power cell input voltage, a communication network (2) to provide a communication path between the master controller (1) and each power cell (4-1,4-2,...,4-n), and cell controllers (3-1,3-2,...,3-n) 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 (1), each cell controller (3-1,3-2,...,3-n) 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 (4-1,4-2,...,4-n), wherein each cell controller (3-1,3-2,...,3-n) is configured to calculate a phase difference value of the corresponding power cell according to a predetermined 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 (4-1,4-2,...,4-n). |
