Hybrid optimized control for dc-dc converter
Systems and methods for controlling a dual active bridge converter or other type of DC-DC converter are disclosed herein. An output voltage of the dual active bridge converter is detected. Based at least in part on the output voltage, a first target duty ratio of a primary bridge of the dual active bridge converter and a second target duty ratio of a secondary bridge of the dual active bridge converter are retrieved from a table. Based on the output voltage, a target phase shift between the primary bridge and the secondary bridge is determined. Based on the first target duty ratio, the second target duty ratio, and the target phase shift, a plurality of switch control signals is caused to be provided to respective switches of the primary bridge and the secondary bridge, to switch according to a time-based switching sequence.
1 . A method for controlling a dual active bridge converter, comprising:
detecting an output voltage of the dual active bridge converter;
retrieving, from a predetermined lookup table stored in memory prior to detecting the output voltage, a first target duty ratio of a primary bridge of the dual active bridge converter and a second target duty ratio of a secondary bridge of the dual active bridge converter associated with the output voltage;
determining a target phase shift between the primary bridge and the secondary bridge, based on the output voltage; 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 first target duty ratio, the second target duty ratio, and the target phase shift.
2 . The method of claim 1 , wherein each of the first target duty ratio, the second target duty ratio, and the target phase shift is associated with a desired output current of the dual active bridge converter in the predetermined lookup table.
3 . The method of claim 2 , wherein the desired output current is selected from among a maximum output current of the dual active bridge converter and a maximum output power of the dual active bridge converter, based on the output voltage.
4 . The method of claim 1 , wherein the determining the target phase shift comprises retrieving, from the predetermined lookup table, the target phase shift based on the output voltage.
5 . The method of claim 1 , wherein the determining the target phase shift further comprises retrieving a phase shift from the predetermined lookup table and adjusting the retrieved phase shift based on a comparison between the output voltage and a reference voltage.
6 . The method of claim 1 , wherein the predetermined lookup table comprises a plurality of reference voltages and a plurality of reference currents, and wherein the determining the target phase shift comprises calculating the target phase shift based on a first comparison between the output voltage and a reference voltage of the plurality of reference voltages and a second comparison between an output current of the dual active bridge converter and a reference current of the plurality of reference currents.
7 . The method of claim 1 , further comprising determining, in advance of providing the plurality of switch control signals to the respective switches of the primary bridge and the secondary bridge, values in the predetermined lookup table by using a generalized-harmonic approximation (GHA) model to optimize a plurality of control variables.
8 . The method of claim 7 , wherein the determining the values in the predetermined lookup table comprises determining, for each voltage at predetermined intervals within a voltage operating range of the dual active bridge converter, the plurality of control variables for at least one output current of the dual active bridge converter by minimizing an expression representing a primary winding current of the dual active bridge converter, the plurality of control variables comprising the first target duty ratio, the second target duty ratio, and the target phase shift.
9 . The method of claim 8 , wherein the minimizing the primary winding current comprises minimizing:
I
RMS
=
∑
k
=
1
2
i
+
1
〈
V
pri
〉
k
2
+
〈
V
sec
〉
k
2
-
2
〈
V
pri
〉
k
〈
V
sec
〉
k
cos
(
k
φ
)
2
k
2
π
f
s
L
,
where:
I RMS is the primary winding current,
〈
V
pri
〉
k
=
4
V
in
k
π
cos
(
k
δ
1
)
〈
V
sec
〉
k
=
4
V
out
k
π
cos
(
k
δ
2
)
φ is the phase shift,
δ 1 is the first target duty ratio,
δ 2 is the second target duty ratio,
V in is an input voltage of the primary bridge,
V out is the output voltage,
L is an inductance of an inductor of the dual active bridge converter, and
f s is a switching frequency of the respective switches of the primary bridge and the secondary bridge.
10 . The method of claim 1 , wherein determining the output voltage comprises detecting a signal level at an output port of the dual active bridge converter that is coupled to a rechargeable battery.
11 . A system for controlling a dual active bridge converter, comprising:
a memory storing instructions and a predetermined lookup table;
an input port coupled to an output port of the dual active bridge converter;
a plurality of output ports coupled to switches of the dual active bridge converter; and
control circuitry coupled to the memory, the input port, and the plurality of output ports and configured to execute the stored instructions to:
determine an output voltage of the dual active bridge converter via the input port, wherein the storing the predetermined lookup table occurs prior to detecting the output voltage;
retrieve, from the predetermined lookup table, a first target duty ratio of a primary bridge of the dual active bridge converter and a second target duty ratio of a secondary bridge of the dual active bridge converter associated with the output voltage;
determine a target phase shift between the primary bridge and the secondary bridge, based on the output voltage; and
cause a plurality of switch control signals, which are provided to respective switches of the primary bridge and the secondary bridge via the plurality of output ports, to switch according to a time-based switching sequence based on the first target duty ratio, the second target duty ratio, and the target phase shift.
12 . The system of claim 11 , wherein each of the first target duty ratio, the second target duty ratio, and the target phase shift is associated with a desired output current of the dual active bridge converter in the predetermined lookup table.
13 . The system of claim 12 , wherein the control circuitry is further configured to select the desired output current from among a maximum output current of the dual active bridge converter and a maximum output power of the dual active bridge converter, based on the output voltage.
14 . The system of claim 11 , wherein the control circuitry is further configured, when determining the target phase shift, to retrieve, from the predetermined lookup table, the target phase shift based on the output voltage.
15 . The system of claim 11 , wherein the control circuitry is further configured to, when determining the target phase shift, retrieve a phase shift stored in the predetermined lookup table and adjust the retrieved phase shift based on a comparison between the output voltage and a reference voltage.
16 . The system of claim 11 , wherein the predetermined lookup table comprises a plurality of reference voltages and a plurality of reference currents, and wherein the control circuitry is further configured, when determining the target phase shift, to calculate the target phase shift based on a first comparison between the output voltage and a reference voltage of the plurality of reference voltages and a second comparison between an output current of the dual active bridge converter and a reference current of the plurality of reference currents.
17 . The system of claim 11 , wherein the control circuitry is further configured to:
determine, in advance of providing the plurality of switch control signals to the respective switches of the primary bridge and the secondary bridge, values in the predetermined lookup table by using a generalized-harmonic approximation (GHA) model to optimize a plurality of control variables; and
when determining the values in the predetermined lookup table, to determine for each voltage at predetermined intervals within a voltage operating range of the dual active bridge converter, the plurality of control variables for at least one output current of the dual active bridge converter by minimizing an expression representing a primary winding current of the dual active bridge converter, the plurality of control variables comprising the first target duty ratio, the second target duty ratio, and the target phase shift.
18 . The system of claim 17 , wherein the control circuitry is further configured, when minimizing the expression representing the primary winding current, to minimize:
I
RMS
=
∑
k
=
1
2
i
+
1
〈
V
pri
〉
k
2
+
〈
V
sec
〉
k
2
-
2
〈
V
pri
〉
k
〈
V
sec
〉
k
cos
(
k
φ
)
2
k
2
π
f
s
L
,
where:
I RMS is the primary winding current,
〈
V
pri
〉
k
=
4
V
in
k
π
cos
(
k
δ
1
)
〈
V
sec
〉
k
=
4
V
out
k
π
cos
(
k
δ
2
)
φ is the phase shift,
δ 1 is the first target duty ratio,
δ 2 is the second target duty ratio,
V in is an input voltage of the primary bridge,
V out is the output voltage,
L is an inductance of an inductor of the dual active bridge converter, and
f s is a switching frequency of the respective switches of the primary bridge and the secondary bridge.
19 . The system of claim 11 , wherein:
the control circuitry is further coupled to a second output port; and
the control circuitry is further configured, when determining the output voltage, to detect a signal level at the second output port of the dual active bridge converter that is coupled to a rechargeable battery.
20 . A method for generating and using a table of predetermined control variables for controlling a dual active bridge converter, having a primary bridge and a secondary bridge, across an output voltage range, the method comprising:
storing, in non-transitory memory, a plurality of pairs of output voltages and target currents arranged in a lookup table;
for each respective output voltage and target current pair in the lookup table, determining values in the table by using a generalized-harmonic approximation (GHA) model to optimize a respective plurality of control variables by minimizing an expression representing a primary winding current of the dual active bridge converter;
storing, in the non-transitory memory, the respective optimized plurality of control variables associated with the respective output voltage and target current pair in the lookup table, wherein the respective optimized plurality of control variables comprises a first target duty ratio of the primary bridge, a second target duty ratio of the second bridge, and a target phase shift between the primary bridge and the secondary bridge;
in response to receiving a detected output voltage and a desired current value from control circuitry, retrieving from the non-transitory memory a target optimized plurality of control variables associated with the detected output voltage and with the desired current value in the lookup table;
transmitting the target optimized plurality of control variables to the control circuitry; and
causing a plurality of switch control signals, which are provided to and control respective switches of the primary bridge and the secondary bridge, to switch according to a time-based switching sequence based on the target optimized plurality of control variables.