Power plant ramp rate control
View Patent ↗A method for controlling plant active power output ramp rate of a power plant to a PCC with a power grid includes obtaining information about a current RES active power output of a Renewable Energy Source (RES) in the power plant. The method also includes forecasting future RES active power output, during a predefined future time period. The method also includes, based on the obtained current RES active power output information and on the forecasted RES active power output, determining whether an expected ramp rate of the RES active power output during the predefined time period exceeds a predefined maximum ramp rate limit of a plant active power output. The method also includes, based on the determining, selecting a first control method which is based on the forecasted future RES active power output if it is determined that the expected ramp rate exceeds the predefined maximum ramp rate limit, or selecting a second control method, different from the first control method, if it is determined that the expected ramp rate does not exceed the predefined maximum ramp rate limit. The method also includes using the selected first or second control method to generate an ESS control signal for controlling the ESS active power output P ESS such that the plant active power output ramp rate is kept below the predefined maximum ramp rate limit during the predefined time period.
1. A method for controlling plant active power output ramp rate of a power plant to a Point of Common Coupling, PCC, with a power grid, the method comprising:
obtaining information about a current RES active power output of a Renewable Energy Source, RES, comprised in the power plant;
forecasting future RES active power output, during a predefined future time period, based on input signals from a meteorological sensor;
based on the obtained current RES active power output information and on the forecasted RES active power output, determining whether an expected ramp rate of the RES active power output during said predefined time period exceeds a predefined maximum ramp rate limit of a plant active power output, the plant active power output being a combination of the RES active power output and an ESS active power output, of an Energy Storage System, ESS, comprised in the power plant, at any given time;
selecting a first control method which is based on the forecasted future RES active power output when it has been determined that the expected ramp rate exceeds the predefined maximum ramp rate limit during the predefined time period, wherein the first control method is a forecast ramp rate (FCRR) control method that is based on only the forecasted future RES active power output;
selecting a second control method which is not based on the forecasted future RES active power output when it has been determined that the expected ramp rate does not exceed the predefined maximum ramp rate limit during the predefined time period, wherein the second control method is a combination of less than 50% of the FCRR control method and at least 50% of a standard ramp rate (STDRR) control method that does not require any forecasted future RES active power output; and
generating an ESS control signal for controlling the ESS active power output such that the plant active power output ramp rate is kept below the predefined maximum ramp rate limit during the predefined time period, wherein the ESS control signal is generated using the selected one of the first control method and the second control method, no matter which one of the first control method and the second control method is selected,
wherein the first control method and the second control method are two different control methods that are independent of each other, and lead to different ESS control signals respectively.
2. The method of claim 1 , wherein the sensor is placed a distance away from the power plant.
3. The method of claim 1 , wherein the forecasting is based on input signals from a sensor of solar radiation or wind speed.
4. The method of claim 1 , wherein the forecasting is based on numerical analysis of past RES active power output.
5. The method of claim 1 , wherein the first control method comprises generating a RES control signal for reducing the RES active power output during said predefined time period.
6. The method of claim 1 , wherein the first control method comprises minimizing a cost function C(t) of time t where P RES, fc is a forecast of the RES active power output P RES and t f is the length of the predefined time period, according to:
C
(
t
)
=
∫
t
t
+
t
f
(
P
plant
(
τ
)
-
P
RES
,
fc
(
τ
)
)
2
d
τ
subject
to
dP
plant
dt
≤
r
l
wherein r l is the ramp rate limit.
7. The method of claim 1 , wherein the first control method comprises utilizing a gain which is dependent on a coefficient as well as the length of the predefined time period and the time when the expected ramp rate exceeds the maximum ramp rate limit if the expected ramp rate exceeds the maximum ramp rate limit, while the gain is equal to the coefficient if the expected ramp rate does not exceed the maximum ramp rate limit.
8. The method of claim 1 , wherein the method is performed periodically with a period which is shorter than the length of the predefined time period.
9. The method of claim 1 , wherein the predefined time period has a length of less than 1 hour, such as a length within the range of 1 or 10 minutes to 1 hour.
10. A computer program product comprising computer-executable components for causing a controller to perform the method of claim 1 when the computer-executable components are run on processor circuitry comprised in the controller.
11. A controller for controlling plant active power output ramp rate of a power plant to a Point of Common Coupling, PCC, with a power grid, the controller comprising:
processor circuitry; and
a storage unit storing software executable by said processor circuitry whereby said controller is operative to:
obtain information about a current RES active power output of a Renewable Energy Source, RES, comprised in the power plant;
forecast future RES active power output, during a predefined future time period, based on input signals from a meteorological sensor;
based on the obtained current RES active power output information and on the forecasted RES active power output, determine whether an expected ramp rate of the RES active power output during said predefined time period exceeds a predefined maximum ramp rate limit of a plant active power output, the plant active power output being a combination of the RES active power output and an ESS active power output, of an Energy Storage System, ESS, comprised in the power plant, at any given time;
select a first control method which is based on the forecasted future RES active power output when it has been determined that the expected ramp rate exceeds the predefined maximum ramp rate limit during the predefined time period, or select a second control method which is not based on the forecasted future RES active power output (P RES ) when it has been determined that the expected ramp rate does not exceed the predefined maximum ramp rate limit during the predefined time period, wherein the first control method is a forecast ramp rate (FCRR) control method that is based on only the forecasted future RES active power output, and the second control method is a combination of less than 50% of the FCRR control method and at least 50% of a standard ramp rate (STDRR) control method that does not require any forecasted future RES active power output; and
generate an ESS control signal for controlling the ESS active power output such that the plant active power output ramp rate is kept below the predefined maximum ramp rate limit during the predefined time period, wherein the ESS control signal is generated using the selected one of the first control method and the second control method, no matter which one of the first control method and the second control method is selected,
wherein the first control method and the second control method are two different control methods that are independent of each other, and lead to different ESS control signals respectively.
12. The method of claim 2 , wherein the forecasting is based on input signals from a sensor of solar radiation or wind speed.
13. The method of claim 2 , wherein the forecasting is based on numerical analysis of past RES active power output.
14. The method of claim 3 , wherein the forecasting is based on numerical analysis of past RES active power output.
15. The method of claim 2 , wherein the first control method comprises generating a RES control signal for reducing the RES active power output during said predefined time period.
16. The method of claim 3 , wherein the first control method comprises generating a RES control signal for reducing the RES active power output during said predefined time period.
17. The method of claim 4 , wherein the first control method comprises generating a RES control signal for reducing the RES active power output during said predefined time period.
18. The method of claim 2 , wherein the first control method comprises minimizing a cost function C(t) of time t where P RES, fc is a forecast of the RES active power output P RES and t f is the length of the predefined time period, according to:
C
(
t
)
=
∫
t
t
+
t
f
(
P
plant
(
τ
)
-
P
RES
,
fc
(
τ
)
)
2
d
τ
subject
to
dP
plant
dt
≤
r
l
wherein r l is the ramp rate limit.
19. The method of claim 3 , wherein the first control method comprises minimizing a cost function C(t) of time t where P RES, fc is a forecast of the RES active power output P RES and t f is the length of the predefined time period, according to:
C
(
t
)
=
∫
t
t
+
t
f
(
P
plant
(
τ
)
-
P
RES
,
fc
(
τ
)
)
2
d
τ
subject
to
dP
plant
dt
≤
r
l
wherein r l is the ramp rate limit.
20. The method of claim 1 , wherein the first control method is using the FCRR control method that is based on only the forecasted future RES active power output only when there is a ramping violation forecasted, and then using the STDRR control method that does not require any forecasted future RES active power output instead of the FCRR control method at the end of ramping.