To Obtain the Three-Phase Current via adjusting width of pulses with Single DC-Link Current Sensor

A pulse-width modulation system adjusting a width of pulses through collecting information of a three-phase current, comprising:

• a three-phase AC motor for generating a three-phase current;
• a pulse-width modulator, coupled to the three-phase AC motor, for modulating the three-phase current to generate an original voltage space vector;
• a detecting device for detecting voltage composition of the original voltage space vector;
• a detecting vector generator for offering three detecting vectors with a sum of zero according to the detecting result;
• a control chip, coupled to the pulse-width modulator, for adding the three detecting vectors with a sum of zero after the original voltage space vector;
• and
• an A/D converter, coupled to the control chip, for sampling a current to generate a sampling result while adding the three detecting vectors;
• wherein the control chip adjusts the width of pulses generated by the pulse width modulator according to the sampling result.

A method for adjusting a width of pulses through collecting information of a three-phase current, comprising:

• an AC motor generating the three-phase current;
• modulating the three-phase current to generate a first sequence of voltage space vectors through a pulse-width modulator, the first sequence of voltage space vectors comprising a plurality of first voltage space vectors;
• detecting each first voltage space vector in the first sequence of voltage space vectors to generate a first detecting result;
• detecting voltage composition of a sum of the plurality of first voltage space vectors to generate a second detecting result;
• replacing different zero voltage space vectors in the first sequence of voltage space vectors with a same zero voltage space vector chosen from the first sequence of voltage space vectors to generate a second sequence of voltage space vectors according to the first detecting result, the second sequence of voltage space vectors comprising a plurality of second voltage space vectors;
• re-arranging orders of the second voltage space vectors in the second sequence of voltage space vectors to generate a third sequence of voltage space vectors;
• offering three detecting vectors with a sum of zero according to the second detecting result;
• adding the three detecting vectors with a sum of zero after the third sequence of voltage space vectors orderly;
• sampling a current to generate a sampling result while adding the three detecting vectors;
• and
• adjusting the width of pulses generated by the pulse width modulator according to the sampling result.

A pulse-width modulation system adjusting a width of pulses through collecting information of a three-phase current, comprising:

• a three-phase AC motor for generating a three-phase current;
• a pulse-width modulator, coupled to the three-phase AC motor, for modulating the three-phase current to generate a first sequence of voltage space vectors, the first sequence of voltage space vectors comprising a plurality of first voltage space vectors;
• a detecting device for detecting each first voltage space vector in the first sequence of voltage space vectors to generate a first detecting result, and detecting voltage composition of a sum of the plurality of first voltage space vectors to generate a second detecting result;
• a replacing device for replacing different zero voltage space vectors in the first sequence of voltage space vectors with a same zero voltage space vector chosen from the first sequence of voltage space vectors to generate a second sequence of voltage space vectors according to the first detecting result, the second sequence of voltage space vectors comprising a plurality of second voltage space vectors;
• a re-arranging device for re-arranging orders of the second voltage space vectors in the second sequence of voltage space vectors to generate a third sequence of voltage space vectors;
• a detecting vector generator for offering three detecting vectors with a sum of zero according to the second detecting result;
• a control chip, coupled to the pulse-width modulator, for adding the three detecting vectors with a sum of zero after the third sequence of voltage space vectors;
• and
• an A/D converter, coupled to the control chip, for sampling a current to generate a sampling result while adding the three detecting vectors;
• wherein the control chip adjusts the width of pulses generated by the pulse width modulator according to the sampling result.