Patent ID: 8315077

Claim:
A space vector modulation method for a multi-phase AC-AC direct conversion device that PWM-controls bidirectional switches with space vector modulation by a direct AC/AC conversion system, the space vector modulation method for the AC-AC direct conversion device comprising: defining a vector state in which a line voltage of multi-phase AC output is expanded onto a two-phase static αβ coordinates; defining a phase-lagging simple harmonic oscillation vector axis and a phase-leading simple harmonic oscillation vector axis in a sector where an output voltage command value vector Vo* exists as an X axis and a Y axis respectively; setting eight vectors as base vectors, the eight vectors comprising maximum voltage vectors X L , Y L , middle vectors X M , Y M and minimum vectors X S , Y S in each axis, a zero vector Z that is an intermediate voltage phase of a power source, and a rotation vector R that is one rotation vector existing in the sector; determining a switching selection pattern formed by a combination of four vectors among the eight vectors, which satisfies predetermined conditions for reducing higher harmonics of an input current and/or an output voltage, deriving a duty coefficient matrix associated with an input and output for the four vectors of the selection pattern on a basis of power source voltage information and output current information; calculating an inverse matrix of the duty coefficient matrix and determining a duty solution of the four vectors; and converting input and output waveforms into sine waves simultaneously by the determined duty solution.