Systems and methods for grid forming control
Systems, methods, and media for grid forming control having balancing feedback across the phases are provided. The grid forming control can include phasor determination configured to, for each of the plurality of phases, receive a frequency reference and determine an active and reactive power for the phase based on an electrical measurement for the phase and the frequency reference, GFM control configured to, for each of the plurality of phases, determine the frequency reference based on the active power for the phase and balancing feedback across the plurality of phases and determine a voltage magnitude reference for the phase based on the reactive power for the phase and balancing feedback across the plurality of phases, and a control loop configured to, for each of the plurality of phases, determine a control signal for a power converter based on the determined voltage magnitude reference for the phase.
1 . A grid forming control system for a power converter having a plurality of phases, comprising:
a phasor determination unit configured to, for each of the plurality of phases:
receive a frequency reference for the phase; and
determine an active power and a reactive power for the phase based on an electrical measurement for the phase and the frequency reference for the phase;
a GFM controller configured to, for each of the plurality of phases:
determine the frequency reference for the phase based on the active power for the phase and an angle balancing feedback across the plurality of phases; and
determine a voltage magnitude reference for the phase based on the reactive power for the phase and a voltage magnitude balancing feedback across the plurality of phases; and
a control loop configured to, for each of the plurality of phases, determine a control signal for the power converter based on the determined voltage magnitude reference for the phase.
2 . The control system of claim 1 , wherein the grid forming control system comprises three phases.
3 . The control system of claim 1 , wherein:
determining the voltage magnitude reference for the phase based on the voltage magnitude balancing feedback comprises determining the voltage magnitude reference for the phase based on the voltage magnitude reference for each of the plurality of phases; and
determining the frequency reference for the phase based on the angle balancing feedback comprises determining the frequency reference for the phase based on the frequency reference for each of the plurality of phases.
4 . The control system of claim 3 , wherein the GFM controller determines the frequency reference for each phase according to:
d
d
t
δ
p
=
ω
o
-
∑
l
∈
𝒫
∖
p
k
s
(
δ
p
-
δ
l
)
+
m
P
(
P
p
*
-
P
p
)
where δ p is the deviation of the voltage phase angle reference θ p for the respective phase, m P is the active power droop gain, k s is the phase balancing gain, is the set of the plurality of phases, the subscript lower-case “p” is the phase being evaluated, ω o is the nominal frequency,
P
p
*
is the active power setpoint for the respective phase, and P p is the determined active power for the respective phase.
5 . The control system of claim 3 , wherein the GFM controller determines the voltage magnitude reference for each phase according to:
τ
d
d
t
V
p
gfm
=
-
V
p
gfm
+
V
*
-
∑
l
∈
𝒫
∖
p
k
s
(
V
p
gfm
-
V
l
gfm
)
+
m
Q
(
Q
p
*
-
Q
p
)
where
V
p
g
f
m
is the voltage magnitude reference for the respective phase, m Q is the reactive power droop gain, k s is the phase balancing gain, is the set of the plurality of phases, the subscript lower-case “p” is the phase being evaluated, V* is the voltage setpoint,
Q
p
*
is the reactive power setpoint for the respective phase, and Q p is the determined reactive power for the respective phase.
6 . The control system of claim 1 , wherein the control loop comprises, for each of the plurality of phases, a voltage controller and current limiter, wherein:
each voltage controller is configured to determine a current reference for the phase based on the determined voltage magnitude reference for the phase; and
each current limiter is configured to determine a current-limited reference for the phase based on the determined current reference for the phase.
7 . The control system of claim 6 , wherein the power converter comprises a current source inverter, and the control signal comprises the current-limited reference.
8 . The control system of claim 6 , wherein:
the power converter comprises a voltage source converter;
the control loop further comprises, for each of the plurality of phases, a voltage controller configured to receive the determined current-limited reference for the phase and determine a modulated voltage reference for the phase based on the received current-limited reference; and
the control signal comprises the modulated voltage reference.
9 . The control system of claim 1 , wherein the GFM controller comprises, for each of the plurality of phases, a separate GFM controller.
10 . The control system of claim 1 , wherein the phasor determination unit comprises a state observer.
11 . A method for controlling a power converter having a plurality of phases, comprising:
receiving, for each of the plurality of phases, a frequency reference for the phase;
determining, for each of the plurality of phases, an active power and a reactive power for the phase based on an electrical measurement for the phase and the frequency reference for the phase;
determining, for each of the plurality of phases, a voltage magnitude reference for the phase based on the reactive power for the phase and a voltage magnitude balancing feedback across the plurality of phases;
determining, for each of the plurality of phases, the frequency reference for the phase based on the active power for the phase and an angle balancing feedback across the plurality of phases; and
determining, for each of the plurality of phases, a control signal for the power converter based on the determined voltage magnitude reference for the phase.
12 . The method of claim 11 , wherein the grid comprises three phases.
13 . The method of claim 11 , wherein:
determining the voltage magnitude reference for the phase based on the voltage magnitude balancing feedback comprises determining the voltage magnitude reference for the phase based on the voltage magnitude reference for each of the plurality of phases; and
determining the frequency reference for the phase based on the angle balancing feedback comprises determining the frequency reference for the phase based on the frequency reference for each of the plurality of phases.
14 . The method of claim 13 , wherein the frequency reference for each phase is determined according to:
d
d
t
δ
p
=
ω
o
-
∑
l
∈
𝒫
∖
p
k
s
(
δ
p
-
δ
l
)
+
m
P
(
P
p
*
-
P
p
)
where δ p is the deviation of the voltage phase angle reference θ p for the respective phase, m P is the active power droop gain, k s is the phase balancing gain, is the set of the plurality of phases, the subscript lower-case “p” refers to the phase being evaluated, ω o is the nominal frequency,
P
p
*
is the active power setpoint for the respective phase, and P p is the determined active power for the respective phase.
15 . The method of claim 13 , wherein the voltage magnitude reference for each phase is determined according to:
τ
d
d
t
V
p
gfm
=
-
V
p
gfm
+
V
*
-
∑
l
∈
𝒫
∖
p
k
s
(
V
p
gfm
-
V
l
gfm
)
+
m
Q
(
Q
p
*
-
Q
p
)
where
V
p
g
f
m
is the voltage magnitude reference for the respective phase, m Q is the reactive power droop gain, k s is the phase balancing gain, is the set of the plurality of phases, the subscript lower-case “p” is the phase being evaluated, V* is the voltage setpoint,
Q
p
*
is the reactive power setpoint for the respective phase, and Q p is the determined reactive power for the respective phase.
16 . The method of claim 11 , further comprising:
determining, by a voltage controller for each of the plurality of phases, a current reference for the phase based on the determined voltage magnitude reference for the phase; and
determining, by a current limiter for each of the plurality of phases, a current-limited reference for the phase based on the determined current reference for the phase.
17 . The method of claim 16 , wherein the power converter comprises a current source inverter, and the control signal comprises the current-limited reference.
18 . The method of claim 16 , further comprising:
determining, by a voltage controller for each of the plurality of phases, a modulated voltage reference for the phase based on the current-limited reference for the phase, and wherein the power converter comprises a voltage source converter and the control signal comprises the modulated voltage reference.
19 . The method of claim 11 , wherein the active power and reactive power for a phase are determined according to a state observer.
20 . The method of claim 11 , wherein the voltage reference is determined at least 1000 time a second.