Two-level predictive based reactive power coordination and voltage restoration for microgrids
View Patent ↗A computer-implemented method for controlling voltage fluctuations of a microgrid including a plurality of distributed generators (DGs) is presented. The computer-implemented method includes collecting, by a resiliency controller, measurement data from the microgrid, using a model predictive control (MPC) module to distribute reactive power to each of the DGs of the microgrid, and using a droop based controller to guide operation of each of the DGs of the microgrid.
1. A computer-implemented method executed on a processor for controlling voltage fluctuations of a microgrid including a plurality of distributed generators (DGs), the method comprising:
collecting, by a resiliency controller, measurement data from the microgrid, the resiliency controller including a voltage control module having a droop-based local control level and a model predictive control (MPC) based global control level;
determining, at the MPC based global control level, optimal reactive power set points of each of the DGs based on reactive power availability;
transmitting the optimal reactive power set points of each of the DGs, via a communication interface, to the droop-based local control level; and
regulating, at the droop-based local control level, via the plurality of DGs, reactive power output through droop-based tracking;
wherein the MPC based global control level enables voltage sensitivity factor determination, prediction model estimation, and MPC model formulation.
2. The method of claim 1 , wherein the resiliency controller further includes a frequency control module and a mode switching module.
3. The method of claim 2 , wherein the voltage control module is executed by a reactive power distribution algorithm for distributing the reactive power to each of the DGs of the microgrid.
4. The method of claim 2 , wherein the frequency control module utilizes a droop based controller to regulate a microgrid frequency.
5. The method of claim 2 , wherein the mode switching module controls microgrid operation status transition between grid-tied mode and islanded mode.
6. The method of claim 1 , wherein, at MPC based global control level, voltage sensitivity factors are used to estimate a relationship between reactive power change and voltage change for each of the DGs of the microgrid.
7. The method of claim 6 , wherein a prediction model for each of the DGs of the microgrid is estimated to predict a behavior of an energy management system in communication with the microgrid via the resiliency controller.
8. The method of claim 6 , wherein the voltage sensitivity factors involve power flow calculations given by:
{
P
i
=
∑
k
=
1
m
V
i
V
k
(
G
ik
cos
(
θ
i
-
θ
k
)
+
B
ik
sin
(
θ
i
-
θ
k
)
)
Q
i
=
∑
k
=
1
m
V
i
V
k
(
G
ik
sin
(
θ
i
-
θ
k
)
-
B
ik
cos
(
θ
i
-
θ
k
)
)
where m is the number of buses in the microgrid, P i and Q i are the real and reactive power at bus i, respectively, G ik and B ik are the conductance and susceptance of the line admittance between bus i and k, respectively, V i and V k are the voltage magnitude at bus i and bus k, respectively; and θ i and θ i are the voltage phase angle of bus i and bus k, respectively.
9. The method of claim 1 , wherein the MPC model formulation is given as:
J
(
V
,
Q
,
k
)
=
∑
k
=
1
N
p
-
1
(
∑
i
=
1
N
V
m
,
i
(
t
+
k
Δ
t
❘
t
)
-
V
ref
,
i
(
t
)
2
+
∑
i
=
1
n
ω
i
Δ
Q
i
(
t
)
2
)
where V m,i is the voltage measurement of bus i, V ref,i is the voltage reference of bus i, N is the total number of buses that voltage control requirements such as critical load bus, N p is the user defined prediction horizon, ω i is the weighting factor for DG i, ΔQ i is the reactive power contribution requirement of DG i adding to nominal set point, and n is the total number of DG participating in voltage control.
10. A system for controlling voltage fluctuations of a microgrid including a plurality of distributed generators (DGs), the system comprising:
a memory; and
a processor in communication with the memory, wherein the processor is configured to:
collect, by a resiliency controller, measurement data from the microgrid, the resiliency controller including a voltage control module having a droop-based local control level and a model predictive control (MPC) based global control level;
determine, at the MPC based global control level, optimal reactive power set points of each of the DGs based on reactive power availability;
transmit the optimal reactive power set points of each of the DGs, via a communication interface, to the droop-based local control level; and
regulate, at the droop-based local control level, via the plurality of DGs, reactive power output through droop-based tracking;
wherein the MPC based global control level enables voltage sensitivity factor determination, prediction model estimation, and MPC model formulation.
11. The system of claim 10 , wherein the resiliency controller includes a frequency control module and a mode switching module.
12. The system of claim 11 , wherein the voltage control module is executed by a reactive power distribution algorithm for distributing the reactive power to each of the DGs of the microgrid.
13. The system of claim 11 , wherein the frequency control module utilizes a droop based controller to regulate a microgrid frequency.
14. The system of claim 11 , wherein the mode switching module controls microgrid operation status transition between grid-tied mode and islanded mode.
15. The system of claim 10 , wherein, at MPC based global control level, voltage sensitivity factors are used to estimate a relationship between reactive power change and voltage change for each of the DGs of the microgrid.
16. The system of claim 15 , wherein a prediction model for each of the DGs of the microgrid is estimated to predict a behavior of an energy management system in communication with the microgrid via the resiliency controller.
17. The system of claim 15 , wherein voltage sensitivity factors involve power flow calculations given by:
{
P
i
=
∑
k
=
1
m
V
i
V
k
(
G
ik
cos
(
θ
i
-
θ
k
)
+
B
ik
sin
(
θ
i
-
θ
k
)
)
Q
i
=
∑
k
=
1
m
V
i
V
k
(
G
ik
sin
(
θ
i
-
θ
k
)
-
B
ik
cos
(
θ
i
-
θ
k
)
)
where m is the number of buses in the microgrid, P i and Q i are the real and reactive power at bus i, respectively, G ik and B ik are the conductance and susceptance of the line admittance between bus i and k, respectively, V i and V k are the voltage magnitude at bus i and bus k, respectively; and θ i and θ i are the voltage phase angle of bus i and bus k, respectively.
18. The system of claim 10 , wherein the the MPC model formulation is given as:
J
(
V
,
Q
,
k
)
=
∑
k
=
1
N
p
-
1
(
∑
i
=
1
N
V
m
,
i
(
t
+
k
Δ
t
❘
t
)
-
V
ref
,
i
(
t
)
2
+
∑
i
=
1
n
ω
i
Δ
Q
i
(
t
)
2
)
where V m,i is the voltage measurement of bus i, V ref,i is the voltage reference of bus i, N is the total number of buses that voltage control requirements such as critical load bus, N p is the user defined prediction horizon, ω i is the weighting factor for DG i, ΔQ i is the reactive power contribution requirement of DG i adding to nominal set point, and n is the total number of DG participating in voltage control.
19. A non-transitory computer-readable storage medium comprising a computer-readable program for controlling voltage fluctuations of a microgrid including a plurality of distributed generators (DGs), wherein the computer-readable program when executed on a computer causes the computer to perform the steps of:
collecting, by a resiliency controller, measurement data from the microgrid, the resiliency controller including a voltage control module having a droop-based local control level and a model predictive control (MPC) based global control level;
determining, at the MPC based global control level, optimal reactive power set points of each of the DGs based on reactive power availability;
transmitting the optimal reactive power set points of each of the DGs, via a communication interface, to the droop-based local control level; and
regulating, at the droop-based local control level, via the plurality of DGs, reactive power output through droop-based tracking;
wherein the MPC based global control level enables voltage sensitivity factor determination, prediction model estimation, and MPC model formulation.
20. The non-transitory computer-readable storage medium of claim 19 ,
wherein the MPC model formulation is given as:
J
(
V
,
Q
,
k
)
=
∑
k
=
1
N
p
-
1
(
∑
i
=
1
N
V
m
,
i
(
t
+
k
Δ
t
❘
t
)
-
V
ref
,
i
(
t
)
2
+
∑
i
=
1
n
ω
i
Δ
Q
i
(
t
)
2
)
where V m,i is the voltage measurement of bus i, V ref,i is the voltage reference of bus i, N is the total number of buses that voltage control requirements such as critical load bus, N p is the user defined prediction horizon, ω i is the weighting factor for DG i, ΔQ i is the reactive power contribution requirement of DG i adding to nominal set point, and n is the total number of DG participating in voltage control.