Three-phase resonant converter and method of controlling the same

1 . A three-phase resonant converter, comprising:

a three-phase transformer, comprising three primary-side windings and three secondary-side windings,

an input bridge arm assembly, comprising a first input switch arm, a second input switch arm, and a third input switch arms respectively coupled to the three primary-side windings, wherein the first input switch arm comprises a first upper switch and a first lower switch, the second input switch arm comprises a second upper switch and a second lower switch, and the third input switch arm comprises a third upper switch and a third lower switch, and

an output bridge arm assembly, comprising a first output synchronous rectification switch arm, a second output synchronous rectification switch arm, and a third output synchronous rectification switch arm respectively coupled to the three secondary-side windings, wherein the first output synchronous rectification switch arm comprises a first upper rectification switch and a first lower rectification switch, the second output synchronous rectification switch arm comprises a second upper rectification switch and a second lower rectification switch, and the third output synchronous rectification switch arm comprises a third upper rectification switch and a third lower rectification switch, and

a current balance controller, configured to receive a first current, a second current, and a third current, and calculate a first phase angle difference and a second phase angle difference according to peak values, average values, or root-mean-square values of the first current, the second current, and the third current,

wherein the first current is a current flowing from a command node between the first upper switch and the first lower switch to the three-phase transformer, the second current is a current flowing from a command node between the second upper switch and the second lower switch to the three-phase transformer, and the third current is a current flowing from a command node between the third upper switch and the third lower switch to the three-phase transformer,

wherein the control unit maintains an output voltage of the resonant converter to be higher than a voltage threshold by configuring the first upper rectification switch to be turned on with a first phase angle leading to the first upper switch, the second upper rectification switch to be turned on with a second phase angle leading to the second upper switch, and the third upper rectification switch to be turned on with a third phase angle leading to the third upper switch; and configuring the first lower rectification switch to be turned on with the first phase angle leading to the first lower switch, the second lower rectification switch to be turned on with the second phase angle leading to the second lower switch, and the third lower rectification switch to be turned on with the third phase angle leading to the third lower switch; wherein the second phase angle is equal to the first phase angle plus the first phase angle difference, and the third phase angle is equal to the first phase angle plus the second phase angle difference.

2 . The three-phase resonant converter as claimed in claim 1 , wherein the control unit acquires a working frequency command according to the output voltage,

wherein based on the working frequency command being less than a frequency threshold of the resonant converter, the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch are turned on, and the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch are turned on, and

wherein a time period of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is longer than a period that is the reciprocal of the frequency threshold, and a time period of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is longer than a period that is the reciprocal of the frequency threshold.

3 . The three-phase resonant converter as claimed in claim 2 , wherein a time point of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is earlier than a time point of turning on one of the first upper switch, the second upper switch, and the third upper switch, and a time point of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is earlier than a time point of turning on one of the first lower switch, the second lower switch, and the third lower switch; a time point of turning off one of the first upper rectification switch, the second rectification switch, and the third rectification switch is earlier than a time point of turning off one of the first upper switch, the second upper switch, and the third upper switch, and a time point of turning off one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is earlier than a time point of turning off one of the first lower switch, the second lower switch, and the third lower switch; and the time period of turning on the upper rectification switches and turning on the lower rectification switches at different switching cycles gradually increases with time.

4 . The three-phase resonant converter as claimed in claim 2 , wherein the frequency threshold is a resonant frequency of the three-phase resonant converter.

5 . The three-phase resonant converter as claimed in claim 1 , wherein the control unit acquires a working frequency command according to the output voltage,

wherein based on the working frequency command being greater than a frequency threshold of the resonant converter, the first upper rectification switch, the second upper rectification switch, and the third upper rectification switches are turned on, and the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is turned,

wherein a time point of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is earlier than a time point of turning on one of the first upper switch, the second upper switch, and the third upper switch, and a time point of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is earlier than a time point of turning on one of the first lower switch, the second lower switch, and the third lower switch; a time period of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is equal to a time period of turning on one of the first upper switch, the second upper switch, and the third upper switch, and a time period of turning on the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is equal to a time period of turning on one of the first lower switch, the second lower switch, and the third lower switch.

6 . The three-phase resonant converter as claimed in claim 1 , wherein based on three input currents flowing into the three primary-side windings being the same, the first phase angle, the second phase angle, and the third phase angle are the same.

7 . The three-phase resonant converter as claimed in claim 6 , wherein the first phase angle difference and the second phase angle difference are zero.

8 . The three-phase resonant converter as claimed in claim 1 , wherein based on three input currents flowing into the three primary-side windings being not the same, the first phase angle, the second phase angle, and the third phase angle are not the same.

9 . The three-phase resonant converter as claimed in claim 8 , wherein the first phase angle difference and the second phase angle difference are not zero.

10 . The three-phase resonant converter as claimed in claim 9 , wherein the first phase angle difference is determined by the first current and the second current, and the second phase angle difference is determined by the first current and the third current;

wherein when the second current is greater than the first current, the first phase angle difference is negative, and when the second current is less than the first current, the first phase angle difference is positive; wherein as an absolute value of a current difference between the second current and the first current increases, an absolute value of the first phase angle difference increases;

wherein when the third current is greater than the first current, the second phase angle difference is negative, and when the third current is less than the first current, the second phase angle difference is positive; wherein as an absolute value of a current difference between the third current and the first current increases, an absolute value of the second phase angle difference increases.

11 . The three-phase resonant converter as claimed in claim 1 , wherein the three primary-side windings of the three-phase transformer are star-connected or delta-connected, and the three secondary-side windings of the three-phase transformer are star-connected or delta-connected.

12 . A method of controlling a three-phase resonant converter, comprising steps of:

providing a three-phase resonant converter having a three-phase transformer, an input bridge arm assembly comprising a first input switch arm, a second input switch arm, and a third input switch arm, and an output bridge arm assembly comprising a first output synchronous rectification switch arm, a second output synchronous rectification switch arm, and a third output synchronous rectification switch arm; wherein the first input switch arm, the second input switch arm, and the third input switch arms respectively comprise a first upper switch and a first lower switch, a second upper switch and a second lower switch, and a third upper switch and a third lower switch; wherein the first output synchronous rectification switch arm, the second output synchronous rectification switch arm, and the third output synchronous rectification switch arms respectively comprise a first upper rectification switch and a first lower rectification switch, a second upper rectification switch and a second lower rectification switch, and a third upper rectification switch and a third lower rectification switch;

maintaining an output voltage of the resonant converter to be higher than a voltage threshold by configuring the first upper rectification switch to be turned on with a first phase angle leading to the first upper switch, the second upper rectification switch to be turned on with a second phase angle leading to the second upper switch, and the third upper rectification switch to be turned on with a third phase angle leading to the third upper switch; and configuring the first lower rectification switch to be turned on with the first phase angle leading to the first lower switch, the second lower rectification switch to be turned on with the second phase angle leading to the second lower switch, and the third lower rectification switch to be turned on with the third phase angle leading to the third lower switch; wherein the second phase angle is equal to the first phase angle plus the first phase angle difference, and the third phase angle is equal to the first phase angle plus the second phase angle difference; and

receiving a first current, a second current, and a third current, and calculating a first phase angle difference and a second phase angle difference according to peak values, average values, or root-mean-square values of the first current, the second current, and the third current,

wherein the first current flows from a node between the first upper switch and the first lower switch to the three-phase transformer, the second current flows from a node between the second upper switch and the second lower switch to the three-phase transformer, and the third current flows from a node between the third upper switch and the third lower switch to the three-phase transformer.

13 . The method of controlling a three-phase resonant converter as claimed in claim 12 , further comprising acquiring a working frequency command according to the output voltage,

wherein based on the working frequency command being less than a frequency threshold of the resonant converter, the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch are turned on, and the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch are turned on, and

wherein a time period of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is longer than a period that is the reciprocal of the frequency threshold, and a time period of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is longer than a period that is the reciprocal of the frequency threshold.

14 . The method of controlling a three-phase resonant converter as claimed in claim 13 , a time point of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is earlier than a time point of turning on one of the first upper switch, the second upper switch, and the third upper switch, and a time point of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is earlier than a time point of turning on one of the first lower switch, the second lower switch, and the third lower switch; and the time period of turning on the upper rectification switches and turning on the lower rectification switches at different switching cycles gradually increases with time.

15 . The method of controlling a three-phase resonant converter as claimed in claim 12 , further comprising acquiring a working frequency command according to the output voltage,

wherein based on the working frequency command being greater than a frequency threshold of the resonant converter, a time point of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is earlier than a time point of turning on one of the first upper switch, the second upper switch, and the third upper switch, and turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is earlier than a time point of turning on one of the first lower switch, the second lower switch, and the third lower switch; a time period of turning on one of the first upper rectification switch, the second upper rectification switch, and the third upper rectification switch is equal to a time period of turning on one of the first upper switch, the second upper switch, and the third upper switch, and a time period of turning on one of the first lower rectification switch, the second lower rectification switch, and the third lower rectification switch is equal to a time period of turning on one of the first lower switch, the second lower switch, and the third lower switch.

16 . The method of controlling a three-phase resonant converter as claimed in claim 12 , wherein based on three input currents flowing into the three primary-side windings of the three-phase transformer being not the same, the first phase angle, the second phase angle, and the third phase angle not the same.

17 . The method of controlling a three-phase resonant converter as claimed in claim 16 , wherein the first phase angle difference and the second phase angle difference are not zero.

18 . The method of controlling a three-phase resonant converter as claimed in claim 17 , wherein the first phase angle difference is determined by the first current and the second current, and the second phase angle difference is determined by the first current and the third current,

wherein when the second current is greater than the first current, the first phase angle difference is negative, and when the second current is less than the first current, the first phase angle difference is positive; wherein as an absolute value of a current difference between the second current and the first current increases, an absolute value of the first phase angle difference increases, and

wherein when the third current is greater than the first current, the second phase angle difference is negative, and when the third current is less than the first current, the second phase angle difference is positive; wherein as an absolute value of a current difference between the third current and the first current increases, an absolute value of the second phase angle difference increases.