Control method during zero-crossing operation of bridge arms in UPS
View Patent ↗A control method is disclosed that involves controlling zero-crossing operation of bridge arms in a UPS, wherein the UPS has a rectifying bridge with first and second switching transistors, a midline bridge arm with third and fourth switching transitors, and an inverter bridge arm with fifth and sixth switching transitors. The midline and rectifying bridge arms are controlled to cross zero synchronously. The inverter bridge arm is controlled to be disconnected during a period before a zero-crossing point of the rectifying bridge arm to a period after the zero-crossing point of the rectifying bridge arm. The periods before and after the zero-crossing point of the rectifying bridge arm are time differences between the zero-crossing points of the inverter bridge arm and the rectifying bridge arm. The influence of asynchronous zero-crossing between the PFC circuit and the inverter circuit on the UPS performance indices may be reduced by using the present control method.
1. A control method to control zero-crossing operation of bridge arms in an uninterruptible power supply (UPS), wherein the UPS has a rectifying bridge arm consisting of a first switching transistor (Q 1 ) and a second switching transistor (Q 2 ), a midline bridge arm consisting of a third switching transistor (Q 3 ) and a fourth switching transistor (Q 4 ), and an inverter bridge arm consisting of a fifth switching transistor (Q 5 ) and a sixth switching transistor (Q 6 ), the method comprising:
controlling the midline bridge arm and the rectifying bridge arm to cross zero synchronously;
controlling both the fifth and sixth switching transistors of the inverter bridge arm to be continuously disconnected during a period beginning before a zero-crossing point of the rectifying bridge arm to a period after the zero-crossing point of the rectifying bridge arm has been passed; and
wherein a first period length before the zero-crossing point and a second period length after the zero-crossing point are determined based on a time difference between a zero-crossing point of the inverter bridge arm and the zero-crossing point of the rectifying bridge arm.
2. The control method to control the zero-crossing operation of the bridge arms in the UPS of claim 1 , wherein the zero-crossing point of the rectifying bridge arm is a zero-crossing point of the rectifying bridge arm from a positive half cycle to a negative half cycle, or a zero-crossing point of the rectifying bridge arm from the negative half cycle to the positive half cycle.
3. The control method to control the zero-crossing operation of the bridge arms in the UPS of claim 2 , further comprising:
during the period before the rectifying bridge arm reaches the crossing zero from the positive half cycle to the negative half cycle, turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 ), while both the fifth switching transistor (Q 5 ) and the sixth switching transistor (Q 6 ) are turned off;
during the period after the zero-crossing point of the rectifying bridge arm, turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ), while both the fifth switching transistor (Q 5 ) and sixth switching transistor (Q 6 ) are turned off; and
wherein the period before and the period after the zero-crossing point of the rectifying bridge arm each are twice as much as a cycle of a driving signal for the fifth switching transistor (Q 5 ) or the sixth switching transistor (Q 6 ).
4. The control method to control the zero-crossing operation of the bridge arms in the UPS of claim 2 , further comprising:
when the rectifying bridge arm is crossing zero from the negative half cycle to the positive half cycle, turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ), while both the fifth switching transistor (Q 5 ) and the sixth switching transistor (Q 6 ) are turned off during the period before the zero-crossing point of the rectifying bridge arm is reached;
turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 ), while both the fifth switching transistor (Q 5 ) and sixth switching transistor (Q 6 ) are turned off during the period after the zero-crossing point of the rectifying bridge arm is passed; and
wherein the period before and the period after the zero-crossing point of the rectifying bridge arm each are twice as much as a cycle of a driving signal for the fifth switching transistor (Q 5 ) or the sixth switching transistor (Q 6 ).
5. A control method to control zero-crossing operation of bridge arms in an uninterruptible power supply (UPS), the UPS having a rectifying bridge arm consisting of a first switching transistor (Q 1 ) and a second switching transistor (Q 2 ), a midline bridge arm consisting of a third switching transistor (Q 3 ) and a fourth switching transistor (Q 4 ), and an inverter bridge arm consisting of a fifth switching transistor (Q 5 ) and a sixth switching transistor (Q 6 ), the method comprising:
controlling the midline bridge arm and the inverter bridge arm to cross zero synchronously and controlling the first and second switching transistors of the rectifying bridge arm to be continuously disconnected throughout a period beginning before a zero-crossing point of the inverter bridge arm is reached, and until a period after the zero-crossing point of the inverter bridge arm has occurred; and
wherein a first period length before the zero-crossing point and a second period length after the zero-crossing point are determined based on a time difference between a zero-crossing point of the inverter bridge arm and the zero-crossing point of the rectifying bridge arm.
6. The control method to control the zero-crossing operation of the bridge arms in the UPS of claim 5 , wherein the zero-crossing point of the inverter bridge arm is a zero-crossing point of the inverter bridge arm from a positive half cycle to a negative half cycle, or a zero-crossing point of the inverter bridge arm from the negative half cycle to the positive half cycle.
7. The control method to control the zero-crossing operation of the bridge arms in the UPS of claim 6 , further comprising:
for the period before the inverter bridge arm begins crossing zero from the positive half cycle to the negative half cycle,
turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 );
turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ); and
wherein the period before and the period after the zero-crossing point of the inverter bridge arm each are twice as much as a cycle of a driving signal for the first switching transistor (Q 1 ) or the second switching transistor (Q 2 ).
8. The control method to control the zero-crossing operation of the bridge arms in UPS of claim 6 , further comprising:
during the period before the inverter bridge arm begins crossing zero from the negative half cycle to the positive half cycle, turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ), while both the first switching transistor (Q 1 ) and the second switching transistor (Q 2 ) are turned off;
turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 ), while both the first switching transistor (Q 1 ) and second switching transistor (Q 2 ) are turned off;
wherein the period before and the period after the zero-crossing point of the inverter bridge arm each are twice as much as a cycle of a driving signal for the first switching transistor (Q 1 ) or the second switching transistor (Q 2 ).
9. A method for controlling a zero-crossing operation of the bridge arms in an uninterruptible power supply (UPS), the UPS comprising a rectifying bridge arm, a midline bridge arm and an inverter bridge arm coupled in parallel, the method comprising:
controlling the midline bridge arm and the rectifying bridge arm to cross zero synchronously;
controlling the inverter bridge arm to be disconnected continuously during a period extending before a zero-crossing point of the rectifying bridge arm to a period after the zero-crossing point of the rectifying bridge arm, and
wherein a first period length before the zero-crossing point and a second period length after the zero-crossing point are determined based on a time difference between a zero-crossing point of the inverter bridge arm and the zero-crossing point of the rectifying bridge arm.
10. The method of claim 9 , further comprising:
configuring the UPS to have:
the rectifying bridge arm consisting of a first switching transistor (Q 1 ) and a second switching transistor (Q 2 );
the midline bridge arm consisting of a third switching transistor (Q 3 ) and a fourth switching transistor (Q 4 );
the inverter bridge arm consisting of a fifth switching transistor (Q 5 ) and a sixth switching transistor (Q 6 ); and
further controlling the UPS such that:
during the period before the rectifying bridge arm begins crossing zero from the positive half cycle to the negative half cycle, turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 ), and turning off both the fifth switching transistor (Q 5 ) and the sixth switching transistor (Q 6 );
turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ), and turning off both the fifth switching transistor (Q 5 ) and sixth switching transistor (Q 6 ), during the period after the zero-crossing point of the rectifying bridge arm; and
wherein the period before and the period after the zero-crossing point of the rectifying bridge arm each are twice as much as a cycle of a driving signal for the fifth switching transistor (Q 5 ) or the sixth switching transistor (Q 6 ).
11. The method of claim 9 , wherein the zero-crossing point of the rectifying bridge arm is a zero-crossing point of the rectifying bridge arm from a positive half cycle to a negative half cycle, or a zero-crossing point of the rectifying bridge arm from the negative half cycle to the positive half cycle.
12. The method of claim 11 , further comprising:
during the period before the rectifying bridge arm begins crossing zero from the negative half cycle to the positive half cycle, turning on the third switching transistor (Q 3 ) and turning off the fourth switching transistor (Q 4 ), and turning off both the fifth switching transistor (Q 5 ) and the sixth switching transistor (Q 6 );
turning off the third switching transistor (Q 3 ) and turning on the fourth switching transistor (Q 4 ), and turning off both the fifth switching transistor (Q 5 ) and sixth switching transistor (Q 6 ), during the period after the zero-crossing point of the rectifying bridge arm; and
wherein the period before and the period after the zero-crossing point of the rectifying bridge arm each are twice as much as a cycle of a driving signal for the fifth switching transistor (Q 5 ) or the sixth switching transistor (Q 6 ).