Method for real-time control of energy storage units to reduce electricity cost
View Patent ↗A method for controlling an energy storage unit having a model which tracks each charging instances includes, for each charging event, capturing energy charged into the energy storage unit and an unit energy price of the charging source(s) at the time of charging; updating a unit price of total energy stored in the storage unit at each time-step; during a discharging event, updating the unit price of energy in the storage unit on a selected cost model; comparing the unit price of energy in the storage unit with other generation sources in the microgrid and a utility tariff; selecting a lowest cost combination from generation, storage, and grid and using the lowest cost combination to supply a load; and if a controller decides to use stored energy at any time, sending a discharge command to the energy storage unit.
1. A method for controlling an energy storage unit having a model which tracks each charging instances, comprising:
for each charging event, capturing energy charged into the energy storage unit from one of a plurality of energy sources and an unit energy price of the charging source(s) at the time of charging;
updating a unit price of total energy stored in the storage unit at each time-step;
during a discharging event, updating the unit price of energy in the storage unit on a selected cost model;
determining a unit price of electricity (UPOE) as
UPOE
(
k
)
=
x
1
(
k
)
×
y
1
(
k
)
+
x
2
(
k
)
×
y
2
(
k
)
+
…
+
x
n
(
k
)
×
y
n
(
k
)
x
1
(
k
)
+
x
2
(
k
)
+
…
+
x
n
(
k
)
where x n (k) represents a total stored amp-hour in the storage device from source n at time k and y is a rate for a generator;
comparing the unit price of energy in the storage unit with other generation sources in a microgrid and a utility tariff;
selecting a lowest cost combination from generation, storage, and grid and using the lowest cost combination to supply a load; and
if a controller decides to use stored energy at any time, sending a discharge command to the energy storage unit.
2. The method of claim 1 , comprising generating an amp-hour cost model or a wart-hour cost model.
3. The method of claim 2 , comprising generating a detailed cost model.
4. The method of claim 2 , comprising generating a recursive cost model.
5. The method of claim 2 , comprising generating a Peukert-based cost model.
6. The method of claim 1 , comprising determining the unit price of electricity charge and discharge of the energy storage unit.
7. The method of claim 1 , comprising charging or discharging with peak shaving and energy optimization.
8. The method of claim 1 , comprising charging or discharging with energy optimization.
9. The method of claim 1 , comprising charging or discharging with uninterruptible power supply (UPS) and energy optimization.
10. The method of claim 9 , comprising providing one of: voltage-based end-of-discharge control and state of charge based end-of-discharge control.
11. The method of claim 1 , comprising determining a unit price of electricity (UPOE) as
UPOE
(
k
)
=
UPOE
(
k
-
1
)
*
Total
Ah
(
k
-
1
)
+
electricity_
cost
1
(
k
)
*
charged
Ah
1
(
k
)
+
…
+
electricity_cost
n
(
k
)
*
charged
Ah
n
(
k
)
Total
Ah
(
k
-
1
)
+
charged
Ah
1
(
k
)
+
…
+
charged
Ah
n
(
k
)
.
12. The method of claim 1 , comprising determining a unit price of electricity (UPOE) as
UPOE
(
k
)
=
UPOE
(
k
-
1
)
*
Total
Ah
(
k
-
1
)
Estimated
Ah
capacity
(
k
,
p
)
where p represents discharged power and Ah represents ampere hours.
13. A method for controlling an energy storage unit in a microgrid, comprising:
an energy storage unit having a model which tracks each charging instances;
a controller coupled to the energy storage unit, comprising code for:
capturing energy charged into the energy storage unit and an unit energy price of the charging source(s) at the time of charging for each charging event;
updating a unit price of total energy stored in the storage unit at each time-step;
during a discharging event, updating the unit price of energy in the storage unit on a selected cost model;
determining a unit price of electricity (UPOE) as
UPOE
(
k
)
=
x
1
(
k
)
×
y
1
(
k
)
+
x
2
(
k
)
×
y
2
(
k
)
+
…
+
x
n
(
k
)
×
y
n
(
k
)
x
1
(
k
)
+
x
2
(
k
)
+
…
+
x
n
(
k
)
where x n (k) represents a total stored amp-hour in the storage device from source n at time k and y is a rate for a generator;
comparing the unit price of energy in the storage unit with other generation sources in the microgrid and a utility tariff;
selecting a lowest cost combination from generation, storage, and grid and using the lowest cost combination to supply a load; and
if a controller decides to use stored energy at any time, sending a discharge command to the energy storage unit.
14. The system of claim 13 , comprising code for generating an amp-hour cost model or a wart-hour cost model.
15. The system of claim 14 , comprising code for a detailed cost model.
16. The system of claim 14 , comprising code for generating a recursive cost model.
17. The system of claim 14 , comprising code for generating a Peukert-based cost model.
18. The system of claim 14 , comprising code for determining a price of electricity (UPOE) based on ampere hour Ah as
UPOE
(
k
)
=
UPOE
(
k
-
1
)
*
Total
Ah
(
k
-
1
)
+
electricity_
cost
1
(
k
)
*
charged
Ah
1
(
k
)
+
…
+
electricity_
cost
n
(
k
)
*
charged
Ah
n
(
k
)
Total
Ah
(
k
-
1
)
+
charged
Ah
1
(
k
)
+
…
+
charged
Ah
n
(
k
)
.
19. The system of claim 14 , comprising code for determining a price of electricity (UPOE) as
UPOE
(
k
)
=
UPOE
(
k
-
1
)
*
Total
Ah
(
k
-
1
)
Estimated
Ah
capacity
(
k
,
p
)
where p represents discharged power and Ah represents ampere hours.