Voltage regulation controller for microgrids with renewables and hybrid energy storage
View Patent ↗The present disclosure envisages a hybrid energy storage system (HESS) for power management of a microgrid. The system includes a plurality of renewable energy sources (RES), a plurality of power converters, a DC bus and a power management controller. Each RES is configured to generate a current I RES . Each RES is connected to a power converter. Each power converter generates a DC voltage V dc from the current I RES . The DC bus is connected to the plurality of power converters. The DC bus receives the DC voltage V dc . The power management controller controls a battery energy storage system (BESS) and a supercapacitor energy storage system (SCSS). The BESS includes a battery which is connected to receive the DC voltage V dc and generate a battery current i batt . The SCSS includes a supercapacitor which is connected to receive the DC voltage V dc and generate a supercapacitor current i SC .
1 . A hybrid energy storage system (HESS) for power management of a microgrid, comprising:
a plurality of renewable energy sources (RES) located within the microgrid, wherein each RES is configured to generate a current I RES ;
a plurality of power converters, wherein each RES is connected to a power converter, wherein each power converter generates a DC voltage V dc from the current I RES ;
a DC bus connected to the plurality of power converters, wherein the DC bus is configured to receive the DC voltage V dc ;
a power management controller configured to control:
a battery energy storage system (BESS) including a battery, wherein the battery is connected to receive the DC voltage V dc and generate a battery current i batt ;
a supercapacitor energy storage system (SCSS) including a supercapacitor, wherein the supercapacitor is connected to receive the DC voltage V dc and generate a supercapacitor current i SC ;
a first bidirectional converter connected across a positive terminal and a negative terminal of the battery; and
a second bidirectional converter connected across a positive terminal and a negative terminal of the SCSS;
wherein the power management controller comprises:
a first adder configured to receive the DC voltage V dc from the DC bus, subtract the DC voltage V DC from a voltage reference V ref , and generate a voltage error signal;
a voltage controller connected to the first adder, wherein the voltage controller is configured to receive the voltage error signal and generate a gain modified battery current;
a second adder connected to the voltage controller, wherein the second adder is configured to subtract the battery current i batt from the gain modified battery current and generate a battery current error signal;
a current controller connected to the second adder, wherein the current controller is configured to compensate a phase difference between the battery current I batt and the battery current error signal, and generate a phase and gain compensated battery current error signal;
a first pulse width modulator (PWM) controller connected to the current controller, wherein the first PWM controller is configured to generate a low power frequency current I LPF from the phase and gain compensated battery current error signal; and
a battery switch SW b connected to the first PWM controller, wherein the first PWM controller is configured to actuate the battery switch SW b to transmit the low power frequency current I LPF to the first bidirectional converter, wherein the first bidirectional converter is configured to charge the battery with the low power frequency current, I LPF .
2 . The hybrid energy storage system of claim 1 , wherein:
the voltage controller is a type II voltage compensator configured to adjust the gain of the DC voltage V dc to match a desired gain v; and
the current controller is a type II current compensator configured to compensate the phase difference between the battery current i batt and the battery current error signal.
3 . The hybrid energy storage system of claim 2 , wherein the voltage controller is configured to adjust the gain of the DC voltage V dc to match the desired gain v by converting the voltage error signal to a frequency domain having a frequency s, identifying poles w z and w p in the voltage error signal in the frequency domain, and restricting a transfer function H T (s) of the voltage controller to:
H
T
(
s
)
=
v
(
1
+
w
z
s
1
+
s
w
p
)
.
4 . The hybrid energy storage system of claim 3 , wherein the current controller is configured to compensate the phase difference between the battery current I batt and the battery current error signal by boosting the phase such that:
f
p
=
tan
(
phase boost
2
+
π
4
)
f
c
f
z
=
f
c
tan
(
phase boost
2
+
π
4
)
,
where f c is a zero crossover frequency of the poles.
5 . The hybrid energy storage system of claim 1 , wherein the power management controller further comprises:
a look up table LUT controller connected to the first adder, wherein the LUT controller is configured to receive the voltage error signal, match the voltage error signal to a corresponding supercapacitor current error signal, and generate an LUT current error signal:
a third adder connected to the LUT controller, wherein the third adder is configured to subtract the supercapacitor current I SC , from the LUT current error signal and generate a supercapacitor current error signal:
a proportional integral (PI) controller configured to receive the supercapacitor current error signal, correct the supercapacitor current, I SC , and generate a corrected supercapacitor current:
a second PWM controller connected to the PI controller, wherein the second PWM controller is configured to receive the corrected supercapacitor current and generate a high power frequency current, I HPF ; and
a supercapacitor switch, SW SC , connected to the second PWM controller, wherein the second PWM controller is configured to actuate the supercapacitor switch, SW b , to transmit the high power frequency current, I HPF , to the second bidirectional converter, wherein the second bidirectional converter is configured to charge the supercapacitor with the high power frequency current, I HPF .
6 . The hybrid energy storage system of claim 5 , further comprising:
a point of common contact (PCC) configured to connect the hybrid energy storage system to any of an AC load, a DC load, and a utility grid, wherein:
the first bidirectional converter is connected to the PCC and configured to supply DC current and DC voltage from the battery to the PCC; and
the second bidirectional converter is connected to the PCC and configured to supply AC current and AC voltage to the PCC.
7 . A method for power management of a hybrid energy storage system (HESS) of a microgrid, comprising:
generating, by a plurality of renewable energy sources (RES) located within the microgrid, a current I RES :
generating, by a plurality of power converters, wherein each RES is connected to a power converter, a DC voltage V dc from the current I RES ;
receiving, by a DC bus connected to the plurality of power converters, the DC voltage V dc ;
receiving, by a battery of a battery energy storage system (BESS), the DC voltage V dc and generating a battery current i batt ;
receiving, by a supercapacitor of a supercapacitor energy storage system (SCSS), the DC voltage V dc and generating a supercapacitor current i SC ,
connecting a first bidirectional converter across a positive terminal and a negative terminal of the battery;
connecting a second bidirectional converter across a positive terminal and a negative terminal of the SCSS;
receiving, by a first adder, the DC voltage V dc from the DC bus, subtracting the DC voltage V DC from a voltage reference V ref ; and generating a voltage error signal;
receiving, by a voltage controller connected to the first adder, the voltage error signal and generating a gain modified battery current;
subtracting, by a second adder connected to the voltage controller, the battery current I batt from the gain modified battery current and generating a battery current error signal;
compensating, by a current controller connected to the second adder, a phase difference between the battery current i batt and the battery current error signal and generating a phase and gain compensated battery current error signal;
generating, by a first pulse width modulator (PWM) controller connected to the current controller, a low power frequency current I LPF from the phase and gain compensated battery current error signal;
actuating, a battery switch SW, by the first PWM controller, to transmit the low power frequency current I LPF to the first bidirectional converter; and
charging the battery with the low power frequency current, I LPF .
8 . The method of claim 7 , further comprising:
receiving, by a look up table LUT controller connected to the first adder, the voltage error signal;
matching, by the LUT controller, the voltage error signal to a corresponding supercapacitor current error signal;
generating, by the LUT controller, an LUT current error signal;
receiving, by a third adder connected to the LUT controller, the LUT current error signal;
subtracting, by the third adder, the supercapacitor current i SC , from the LUT current error signal;
generating, by the third adder, a supercapacitor current error signal;
receiving, by a proportional integral (PI) controller, the supercapacitor current error signal;
correcting, by the PI controller, the supercapacitor current, i SC ;
generating, by the PI controller, a corrected supercapacitor current;
receiving, by a second PWM controller connected to the PI controller, the corrected supercapacitor current;
generating, by the second PWM controller, a high power frequency current, I HPF ;
actuating, by the second PWM controller, a supercapacitor switch SW SC ; and
transmitting, by the supercapacitor switch SW SC the high power frequency current, I HPF , to the second bidirectional converter, wherein the second bidirectional converter is configured to charge the supercapacitor with the high power frequency current, I HPF .
9 . The method of claim 8 , further comprising:
connecting the first bidirectional converter is connected to a point of common contact (PCC);
supplying DC current and DC voltage from the battery to the PCC;
connecting the second bidirectional converter to the PCC; and
supplying AC current and AC voltage to the PCC from the supercapacitor.
10 . The method of claim 9 , further comprising:
adjusting, by the voltage controller, the gain of the DC voltage V dc to match the desired gain v by:
converting the voltage error signal to a frequency domain having a frequency s, identifying poles w z and w p in the voltage error signal in the frequency domain, and restricting a transfer function H T (s) of the voltage controller to:
H
T
(
s
)
=
v
(
1
+
w
z
s
1
+
s
w
p
)
.
11 . The method of claim 10 , further comprising:
compensating, by the current controller, the phase difference between the battery current I batt and the battery current error signal by boosting the phase such that:
f
p
=
tan
(
phase boost
2
+
π
4
)
f
c
f
z
=
f
c
tan
(
phase boost
2
+
π
4
)
,
where f c is a zero crossover frequency of the poles.
12 . A non-transitory computer readable medium having instructions stored therein that, when executed by one or more processors, cause the one or more processors to perform a method for power management of a hybrid energy storage system (HESS) of a microgrid, comprising:
generating, by a plurality of renewable energy sources (RES) located within the microgrid, a current I RES ;
generating, by a plurality of power converters, wherein each RES is connected to a power converter, a DC voltage V dc from the current I RES ;
receiving, by a DC bus connected to the plurality of power converters, the DC voltage V dc ;
receiving, by a battery of a battery energy storage system (BESS), the DC voltage V dc and generating a battery current i batt ;
receiving, by a supercapacitor of a supercapacitor energy storage system (SCSS), the DC voltage V dc and generating a supercapacitor current i SC ;
receiving, by a first adder, the DC voltage V dc from the DC bus, subtracting the DC voltage V DC from a voltage reference V ref , and generating a voltage error signal;
receiving, by a voltage controller connected to the first adder, the voltage error signal and generating a gain modified battery current;
subtracting, by a second adder connected to the voltage controller, the battery current I batt from the gain modified battery current and generating a battery current error signal;
compensating, by a current controller connected to the second adder, a phase difference between the battery current I batt and the battery current error signal and generating a phase and gain compensated battery current error signal;
generating, by a first pulse width modulator (PWM) controller connected to the current controller, a low power frequency current I LPF from the phase and gain compensated battery current error signal;
actuating, a battery switch SW b by the first PWM controller, to transmit the low power frequency current I LPF to a first bidirectional converter connected in parallel with the battery; and
charging the battery with the low power frequency current, I LPF .
13 . The non-transitory computer readable medium method of claim 12 , further comprising:
receiving, by a look up table LUT controller connected to the first adder, the voltage error signal;
matching, by the LUT controller, the voltage error signal to a corresponding supercapacitor current error signal;
generating, by the LUT controller, an LUT current error signal;
receiving, by a third adder connected to the LUT controller, the LUT current error signal;
subtracting, by the third adder, the supercapacitor current I SC , from the LUT current error signal;
generating, by the third adder, a supercapacitor current error signal;
receiving, by a proportional integral (PI) controller, the supercapacitor current error signal;
correcting, by the PI controller, the supercapacitor current, i SC ;
generating, by the PI controller, a corrected supercapacitor current;
receiving, by a second PWM controller connected to the PI controller, the corrected supercapacitor current;
generating, by the second PWM controller, a high power frequency current, I HPF ;
actuating, by the second PWM controller, a supercapacitor switch SW SC ; and
transmitting, by the supercapacitor switch SW SC the high power frequency current, I HPF , to a second bidirectional converter connected in parallel with the supercapacitor, wherein the second bidirectional converter is configured to charge the supercapacitor with the high power frequency current, I HPF .
14 . The non-transitory computer readable medium method of claim 13 , further comprising:
adjusting, by the voltage controller, the gain of the DC voltage V dc to match the desired gain v by:
converting the voltage error signal to a frequency domain having a frequency s, identifying poles w z and w p in the voltage error signal in the frequency domain, and restricting a transfer function H T (s) of the voltage controller to:
H
T
(
s
)
=
v
(
1
+
w
z
s
1
+
s
w
p
)
.
15 . The non-transitory computer readable medium method of claim 14 , further comprising:
compensating, by the current controller, the phase difference between the battery current I batt and the battery current error signal by boosting the phase such that:
f
p
=
tan
(
phase boost
2
+
π
4
)
f
c
f
z
=
f
c
tan
(
phase boost
2
+
π
4
)
,
where f c is a zero crossover frequency of the poles.