Energy storage systems for electrical microgrids with pulsed power loads
Pulsed power loads (PPLs) are highly non-linear and can cause significant stability and power quality issues in an electrical microgrid. According to the present invention, many of these issues can be mitigated by an Energy Storage System (ESS) that offsets the PPL. The ESS can maintain a constant bus voltage and decouple the generation sources from the PPL. For example, the ESS specifications can be obtained with an ideal, band-limited hybrid battery and flywheel system.
1. An electrical microgrid, comprising
a pulsed power load that provides a load transient to a bus of the electrical microgrid, wherein the pulsed power load has a time-varying power consumption waveform P(t) having a duty cycle, D p , a period, T p , and a peak value, P peak ,
an energy storage system,
a bus interface converter electrically connected between the energy storage system and the bus, the bus interface converter having a control input duty cycle to control switching of the bus interface converter to provide an injected current at the bus from the energy storage system, and
a controller that adjusts the control input duty cycle of the bus interface converter to control the injected current at the bus to track an injected current reference value, u, so as to mitigate the load transient from the pulsed power load and maintain a desired load voltage at the bus, calculated according to the equation:
u
=
-
2
(
R
+
R
L
)
(
D
P
P
p
e
a
k
-
P
(
t
)
)
R
(
λ
2
R
v
b
2
-
4
R
L
D
p
P
p
e
a
k
(
R
+
R
L
)
)
+
λ
R
v
b
where R is a modeled resistance of the bus interface converter, R L is a modeled line resistance of the microgrid, λ is the control input duty cycle, and v b is a voltage of the bus.
2. The electrical microgrid of claim 1 , wherein the energy storage system has a baseline energy storage capacity greater or equal to W u =−(D p −1)D p T p P peak .
3. The electrical microgrid of claim 1 , wherein the energy storage system comprises at least one of a supercapacitor, flywheel, or battery.
4. The electrical microgrid of claim 3 , wherein the energy storage system comprises a hybrid battery and flywheel configuration.
5. The electrical microgrid of claim 1 , wherein the energy storage system comprises a spinning mass flywheel and a permanent magnet DC machine and the bus interface converter comprises a buck converter.
6. The electrical microgrid of claim 1 , wherein the energy storage system comprises a battery and the bus interface converter comprises a boost converter.