Modulation to extend dual-active bridge converter zero-voltage switching margin under parameter variation
Systems and methods for controlling a dual active bridge converter are disclosed herein. A probability of losing zero voltage switching (ZVS) of a dual active bridge (DAB) converter comprising is determined. At least one control variable of a plurality of control variables of the DAB converter is modified to change ZVS margin to achieve ZVS based on a determined probability of losing ZVS. A plurality of switch control signals, which are provided to respective switches of the primary bridge and the secondary bridge of the DAB, are caused to switch according to a time-based switching sequence based on the plurality of control variables.
1. A method comprising:
determining a probability of losing zero voltage switching (ZVS) of a dual active bridge (DAB) converter comprising a primary bridge, a secondary bridge, and a transformer coupling the primary bridge and the secondary bridge;
modifying at least one control variable of a plurality of control variables of the DAB converter to change ZVS margin to achieve ZVS based on a determined probability of ZVS; and
causing a plurality of switch control signals, which are provided to respective switches of the primary bridge and the secondary bridge, to switch according to a time-based switching sequence based on the plurality of control variables.
2. The method of claim 1 , wherein determining the probability of losing ZVS comprises:
measuring a temperature of the DAB converter; and
determining the probability of losing ZVS based on the measured temperature.
3. The method of claim 2 , wherein determining the probability of losing ZVS further comprises:
determining whether the DAB converter is operating under partial ZVS;
determining a difference between a predetermined phase shift between the primary bridge and the secondary bridge and a real-time phase shift between the primary bridge and the secondary bridge; and
determining the probability of losing ZVS based on the determination of whether the DAB converter is operating under partial ZVS, the determination of the difference between the predetermined phase shift and the real-time phase shift, and the measured temperature.
4. The method of claim 2 , wherein the probability of losing ZVS based on measured temperature corresponds to a determined temperature rise, where the determined temperature rise is:
Δ
T
rise
=
❘
"\[LeftBracketingBar]"
δ
(
T
pri
-
T
sec
)
δ
P
out
❘
"\[RightBracketingBar]"
,
wherein T pri is a temperature of the primary bridge, T sec is a temperature of the secondary bridge, and P out is a power output of the DAB converter.
5. The method of claim 2 , wherein modifying at least one control variable of the plurality of control variables of the DAB converter to change ZVS margin to achieve ZVS based on a determined probability of ZVS comprises iteratively modifying the at least one control variable until the measured temperature reaches a minimum temperature corresponding to a desired ZVS margin.
6. The method of claim 5 , wherein the desired ZVS margin comprises a minimum current value of the transformer sufficient to enable an anti-parallel diode of each of the respective switches of the primary bridge and the secondary bridge to switch on and discharge charge stored on the respective switch.
7. The method of claim 5 , wherein the minimum temperature corresponds to ZVS with an optimal ZVS margin.
8. The method of claim 5 , wherein:
the plurality of control variables of the DAB converter comprises a first duty ratio of the primary bridge, a second duty ratio of the secondary bridge, and a phase shift between the primary bridge and the secondary bridge; and
modifying at least one control variable comprises modifying at least one of the first duty ratio and the second duty ratio.
9. The method of claim 8 , wherein modifying at least one of the first duty ratio and the second duty ratio comprises adjusting at least one of a differential mode (DM) adjustment variable and a common mode (CM) adjustment variable.
10. The method of claim 1 , wherein determining the probability of losing ZVS comprises:
measuring a current of the transformer; and
determining the probability of losing ZVS based on the measured current of the transformer.
11. A system for controlling a dual active bridge (DAB) converter having a primary bridge, a secondary bridge, and a transformer coupling the primary bridge to the secondary bridge, the system comprising:
a plurality of output ports coupled to switches of the DAB converter; and
control circuitry coupled to the plurality of output ports and configured to:
determine a probability of losing zero voltage switching (ZVS) of the DAB;
modify at least one control variable of a plurality of control variables of the DAB converter to change ZVS margin to achieve ZVS based on a determined probability of ZVS; and
cause a plurality of switch control signals, which are provided to respective switches of the primary bridge and the secondary bridge, to switch according to a time-based switching sequence based on the plurality of control variables.
12. The system of claim 11 , further comprising a port of the DAB converter, wherein the control circuitry is coupled to the port and is configured to determine the probability of losing ZVS by:
measuring a temperature of the DAB converter; and
determining the probability of losing ZVS based on the measured temperature.
13. The system of claim 12 , wherein the control circuitry is further configured to determine the probability of losing ZVS by:
determining whether the DAB converter is operating under partial ZVS;
determining a difference between a predetermined phase shift between the primary bridge and the secondary bridge and a real-time phase shift between the primary bridge and the secondary bridge; and
determining the probability of losing ZVS based on the determination of whether the DAB converter is operating under partial ZVS, the determination of the difference between the predetermined phase shift and the real-time phase shift, and the measured temperature.
14. The system of claim 12 , wherein the probability of losing ZVS based on measured temperature corresponds to a determined temperature rise, where the determined temperature rise is:
Δ
T
rise
=
❘
"\[LeftBracketingBar]"
δ
(
T
pri
-
T
sec
)
δ
P
out
❘
"\[RightBracketingBar]"
,
wherein T pri is a temperature of the primary bridge, T sec is a temperature of the secondary bridge, and P out is a power output of the DAB converter.
15. The system of claim 12 , wherein the control circuitry is configured to modify at least one control variable of the plurality of control variables of the DAB converter to change ZVS margin to achieve ZVS by iteratively modifying the at least one control variable until the measured temperature reaches a minimum temperature corresponding to a desired ZVS margin.
16. The system of claim 15 , wherein the desired ZVS margin comprises a minimum current value of the transformer sufficient to enable an anti-parallel diode of each of the respective switches of the primary bridge and the secondary bridge to switch on and discharge charge stored on the respective switch.
17. The system of claim 15 , wherein the minimum temperature corresponds to ZVS with an optimal ZVS margin.
18. The system of claim 15 , wherein:
the plurality of control variables of the DAB converter comprises a first duty ratio of the primary bridge, a second duty ratio of the secondary bridge, and a phase shift between the primary bridge and the secondary bridge; and
the control circuitry is configured to modify at least one control variable by modifying at least one of the first duty ratio and the second duty ratio.
19. The system of claim 18 , wherein the control circuitry is configured to modify at least one of the first duty ratio and the second duty ratio by adjusting at least one of a differential mode (DM) adjustment variable and a common mode (CM) adjustment variable.
20. The system of claim 11 , wherein the control circuitry is configured to determine the probability of losing ZVS by:
measuring a current of the transformer, and
determining the probability of losing ZVS based on the measured current of the transformer.