Dual active bridge converter with deadtime compensation reducing heat for varying loads
An electronic controller is configured to provide control signals to the control terminals of the semiconductor switches of the primary converter and the secondary converter based on a commanded current or target output current; the electronic controller is configured to adjust the phase angle(s), between a respective pairs of semiconductor switches of the primary converter and second converter based on a deadtime compensation module responsive to a current error or current difference between the target output current and the observed output current. A low-pass filter facilitates estimation of the current error for compensation in the commanded current.
1 . A dual-active-bridge converter comprising:
a primary converter having a first switched terminal of low-side semiconductor switch coupled to a corresponding second switched terminal of high-side semiconductor switch at a primary alternating current node, the low-side semiconductor switch having a second switched terminal coupled to one terminal of a primary direct current bus; the high-side semiconductor switch having a first switched terminal coupled to another terminal of the primary direct current bus;
a secondary converter having a first switched terminal of low-side semiconductor switch coupled to a corresponding second switched terminal of high-side semiconductor switch at a secondary alternating current node, the low-side semiconductor switch having a second switched terminal coupled to one terminal of a secondary direct current bus; the high-side semiconductor switch having a first switched terminal coupled to another terminal of the secondary direct current bus;
an output voltage estimator configured to estimate an observed output voltage the secondary converter;
an output current estimator configured to estimate an observed output current of the secondary converter;
a transformer coupled between the primary current node and the secondary current node;
an electronic controller configured to provide control signals to the control terminals of the semiconductor switches of the primary converter and the secondary converter based on a commanded current or target output current; the electronic controller configured to adjust the phase angle(s), between a respective pairs of semiconductor switches of the primary converter and second converter based on a deadtime compensation module responsive to a current error or current difference between the target output current and the observed output current.
2 . The converter according to claim 1 wherein the bandwidth of the deadtime compensation is greater than a bandwidth of a voltage regulation loop of the secondary DC bus output.
3 . The converter according to claim 1 wherein a feedforward component of the target output current is susceptible to current oscillation of the load current.
4 . The method according to claim 1 wherein the bandwidth of the deadtime compensation is greater than a bandwidth of a voltage regulation loop of the secondary DC bus output.
5 . The method according to claim 1 wherein a feedforward component of the target output current is susceptible to current oscillation of the load current.
6 . The converter according to claim 1 wherein the current error is a function of a low-pass filter bandwidth, its cut-off frequency or its Q (quality) ratio that enables the current error to be estimated within a limited bandwidth or potentially resonant frequency of the low-pass filter.
7 . The converter according to claim 6 such that within a certain bandwidth the current error can be estimated based on the following equation:
f
D
T
=
C
d
U
D
A
B
d
t
+
I
D
A
B
-
I
c
m
d
where f DT is the current error between the ideal output current and the actual output current that is influenced or disturbed by deadtime;
where C is the capacitance of a secondary capacitor between secondary DC output terminals;
u DAB is the voltage or voltage potential between the terminals of the capacitor C;
dU DAB/dt is the derivative of the observed output voltage between the terminals of the capacitor C, where the derivative measures an alternating current component or transient of predominately direct current output at the secondary DC output terminals;
I DAB is the observed output current or observed load current at the secondary DC output terminals;
I cmd is the commanded output current at the secondary DC output terminals.
8 . The converter according to claim 7 wherein the deadtime compensation module is configured to generate a phase shift between corresponding semiconductor switches of the primary converter and the secondary converter to compensate for the error or difference associated with the deadtime with attenuated components in the error arising from sensor noise of the current estimator, the voltage estimator, or both.
9 . The converter according to claim 8 wherein the deadtime compensation module is configured to adjust a phase offset between a low-side switch and a high-side switch of the primary converter or the secondary converter consistent with a target duty cycle.
10 . The converter according to claim 7 wherein the deadtime compensation module is configured to apply an adaptive hysteresis loop to reduce the error over one or more successive measurement intervals of the sensors.
11 . The converter according to claim 10 wherein a maximum compensating phase shift of adaptive hysteresis loop is bounded by or proportional to the switching frequency and the deadtime duration in the primary converter or secondary converter.
12 . The converter according to claim 11 wherein the adaptive hysteresis loop is based on the operating point of the converter, such as dual-active-bridge (DAB) converter power equations.
13 . The converter according to claim 7 wherein the deadtime compensation module is configured to adjust the phase shift based on the error consistent with maintaining a zero-voltage-switching (ZVS) state within the primary and secondary switches of the converter.
14 . A method of operating a dual-active-bridge (DAB) direct-current-to-direct current converter, the method comprising:
estimating an observed output voltage of the secondary converter;
estimating an observed output current of the secondary converter;
providing control signals to a plurality of control terminals of the semiconductor switches of the primary converter and the secondary converter based on a commanded current or target output current; and
adjusting one or more phase angles between respective pairs of semiconductor switches of the primary converter and the secondary converter based on a deadtime compensation responsive to a current error or current difference between the target output current and the observed output current.
15 . The method according to claim 14 further comprising:
adjusting a phase offset between a low-side switch and a high-side switch of the primary converter or the secondary converter consistent with a target duty cycle.
16 . The method according to claim 14 wherein the current error is a function of a low-pass filter bandwidth or its cut-off frequency, or its Q (quality) ratio that enables the current error to be estimated within a limited bandwidth or about a potentially resonant frequency of the low-pass filter.
17 . The method according to claim 16 , within a certain bandwidth, defined by the Q ratio, estimating the current error based on the following equation:
f
D
T
=
C
d
U
D
A
B
d
t
+
I
D
A
B
-
I
c
m
d
where C is the secondary capacitor between secondary DC output terminals;
dU DAB/dt is the derivative of the observed output voltage with respect to time, which measures an alternating current component or transient of predominately direct current output at the secondary DC output terminals;
I DAB is the observed output current or observed load current at the secondary DC output terminals;
I cmd is the commanded output current at the secondary DC output terminals.
18 . The method according to claim 14 further comprising:
generating a phase shift between corresponding semiconductor switches of the primary converter and the secondary converter to compensate for the error or difference associated with the deadtime with attenuated components in the error arising from sensor noise of the current estimator, the voltage estimator, or both.
19 . The method according to claim 18 further comprising:
applying an adaptive hysteresis loop to reduce the error over one or more successive measurement intervals of any sensors or estimators for estimating the output current and output voltage of the secondary converter.
20 . The method according to claim 19 wherein a maximum compensating phase shift of adaptive hysteresis loop is bounded by or proportional to the switching frequency and the deadtime duration in the primary converter or secondary converter.
21 . The method according to claim 19 wherein the adaptive hysteresis loop is based on the operating point of DAB converter, such as dual-active-bridge (DAB) converter power equations.
22 . The method according to claim 14 further comprising:
adjusting the phase shift based on the error consistent with maintaining a zero-voltage-switching (ZVS) state within the primary and secondary switches of The method.