Patent ID: 7495936

Claim:
A three-phase voltage-fed AC/DC converter, comprising: a three-phase voltage-fed AC/DC conversion circuit which has internal equivalent impedance viewed from an AC terminal, converts power from a DC voltage source to three-phase AC power in accordance with the pulse width of gate signals generated based on a PWM reference, and outputs said three-phase AC power to said AC terminal; a UM conversion circuit which converts the three-phase output voltage at said AC terminal to dq rotational coordinates in which the component related to the amplitude of said three-phase output voltage forms the d-axis component and the component related to the frequency deviation of said three-phase output voltage forms the q-axis component, and outputs the result; a superior voltage control circuit which receives the input of a superior reference vector formed with both a voltage amplitude reference value for the amplitude of the three-phase output voltage at said AC terminal and a frequency reference value for the frequency, and generates a signal that makes the amplitude and frequency of the three-phase output voltage at said AC terminal close to the reference values prepared by said superior reference vector, based on said inputted superior reference vector and the output voltage vector obtained by said UM conversion circuit, and outputs the signal as a voltage reference vector; an inferior voltage control circuit which generates a signal that makes the amplitude and phase of said three-phase output voltage close to the combined value of both a base voltage vector and said voltage reference vector, based on said base voltage vector which prescribes the amplitude and phase of the three-phase output voltage at said AC terminal, an output voltage vector obtained by said UM conversion circuit and said voltage reference vector from said superior voltage control circuit, and outputs the signal as said PWM reference; and a frequency control circuit which synchronizes a value generated based on a base frequency which prescribes the frequency of the three-phase output voltage at said AC terminal and said q-axis component of the output voltage vector obtained by said UM conversion circuit with the rotation angle of a conversion matrix in said UM conversion circuit.