Power grid configuration control method and apparatus for flexible direct current power transmission system, and medium
A method and a device for controlling grid configuration of a flexible direct current electric power transmission system, and a computer-readable storage medium are provided. The active power reference value is modified based on the frequency deviation of the alternating current grid. The reactive power reference value is modified based on the voltage deviation of the alternating current grid. The outputted active power and the outputted reactive power are controlled based on the active power reference value and the reactive power reference value, respectively. The grid voltage is further configured and controlled through power control, so that the system is capable of self-synchronization, frequency regulation and voltage regulation. In addition, the virtual synchronous machine technology is introduced into control of the reactive power, so that the system can provide inertia support for the grid voltage amplitude.
1 . A method for controlling grid configuration of a flexible direct current electric power transmission system, comprising:
modifying an active power reference value based on a frequency deviation of an alternating current grid;
modifying a reactive power reference value based on a voltage deviation of the alternating current grid;
controlling an outputted active power by using a pre-established frequency regulation motion equation of a virtual synchronous machine based on the active power reference value and configuring a phase angle;
controlling an outputted reactive power by using a pre-established voltage regulation motion equation of the virtual synchronous machine based on the reactive power reference value and configuring a grid voltage amplitude; and
performing PI control on an actual grid voltage based on the grid voltage amplitude and the phase angle, and acquiring a three-phase voltage reference value through inner-loop control;
wherein the modifying the active power reference value based on the frequency deviation of the alternating current grid comprises:
determining an active power setting value as the active power reference value when it is detected that the frequency deviation of the alternating current grid is less than a preset frequency deviation threshold; and
adding a deviation value of active power that changes with a frequency of the alternating current grid to the active power setting value and determining the obtained sum as the active power reference value when it is detected that the frequency deviation of the alternating current grid is greater than the preset frequency deviation threshold.
2 . The method according to claim 1 , wherein the modifying the reactive power reference value based on the voltage deviation of the alternating current grid comprises:
determining a reactive power setting value as the reactive power reference value when it is detected that the voltage deviation of the alternating current grid is less than a preset voltage deviation threshold; and
adding a deviation value of reactive power that changes with a voltage of the alternating current grid to the reactive power setting value and determining the obtained sum as the reactive power reference value when it is detected that the voltage deviation of the alternating current grid is greater than the preset voltage deviation threshold.
3 . The method according to claim 1 , wherein the frequency regulation motion equation of the virtual synchronous machine is expressed as:
{
d
θ
dt
=
ω
J
p
d
ω
dt
=
P
ref
/
ω
ref
-
P
/
ω
ref
+
D
p
(
ω
ref
-
ω
)
wherein ω represents an angular frequency, θ represents the phase angle, D p represents a damping coefficient of active power control, J p represents a moment of inertia of the active power control, P ref represents the active power reference value, ω ref represents an angular frequency reference value, and P represents the outputted active power.
4 . The method according to claim 1 , wherein the voltage regulation motion equation of the virtual synchronous machine is expressed as:
J
q
d
V
d
t
=
Q
ref
-
Q
+
D
q
(
V
mref
-
V
)
wherein D q represents a damping coefficient of reactive power control, J q represents a moment of inertia of the reactive power control, Q ref represents the reactive power reference value, Q represents the outputted reactive power, V mref represents a grid voltage amplitude reference value, and V represents the grid voltage amplitude.
5 . The method according to claim 1 , wherein the determining the active power setting value as the active power reference value when it is detected that the frequency deviation of the alternating current grid is less than the preset frequency deviation threshold; and adding the deviation value of the active power that changes with the frequency of the alternating current grid to the active power setting value and determining the obtained sum as the active power reference value when it is detected that the frequency deviation of the alternating current grid is greater than the preset frequency deviation threshold is expresses as:
P
ref
=
{
P
set
,
❘
"\[LeftBracketingBar]"
f
ref
-
f
❘
"\[RightBracketingBar]"
≤
Δ
f
set
P
set
+
[
K
P
(
f
ref
-
f
)
+
T
P
(
f
ref
-
f
)
]
α
i
(
P
max
i
-
P
i
)
∑
i
n
α
i
(
P
max
i
-
P
i
)
,
f
ref
-
f
>
Δ
f
set
P
set
+
[
K
p
(
f
ref
-
f
)
+
T
P
∫
(
f
ref
-
f
)
]
α
i
P
i
∑
i
n
α
i
P
i
,
f
-
f
ref
>
Δ
f
set
wherein P ref represents the active power reference value, P set represents the active power setting value, f ref represents a frequency reference value, f represents an actual frequency of the alternating current grid, K P represents a first frequency deviation control coefficient, T P represents a second frequency deviation control coefficient, Δf set represents a preset frequency deviation threshold, α i represents an operating status of an i th flexible direct current electric power transmission system, P maxi represents a maximum of active power outputted by the i th flexible direct current electric power transmission system, P i represents an actual active power outputted by the i th flexible direct current electric power transmission system, and n is the number of flexible direct current electric power transmission systems participating in frequency regulation.
6 . The method according to claim 2 , wherein the determining the reactive power setting value as the reactive power reference value when it is detected that the voltage deviation of the alternating current grid is less than the preset voltage deviation threshold; and adding the deviation value of the reactive power that changes with the voltage of the alternating current grid to the reactive power setting value and determining the obtained sum as the reactive power reference value when it is detected that the voltage deviation of the alternating current grid is greater than the preset voltage deviation threshold is expresses as:
Q
ref
=
{
Q
set
,
❘
"\[LeftBracketingBar]"
V
mref
-
V
m
❘
"\[RightBracketingBar]"
≤
Δ
V
set
Q
set
+
[
K
Q
(
V
mref
-
V
m
)
+
T
Q
∫
(
V
mref
-
V
m
)
]
α
i
(
Q
max
i
-
Q
i
)
∑
i
k
α
i
(
Q
max
i
-
Q
i
)
,
V
mref
-
V
m
>
Δ
V
set
Q
set
+
[
K
Q
(
V
mref
-
V
m
)
+
T
Q
∫
(
V
mref
-
V
m
)
]
α
i
(
Q
max
i
+
Q
i
)
∑
i
k
α
i
(
Q
max
i
+
Q
i
)
,
V
m
-
V
mref
>
Δ
V
set
wherein Q ref represents the reactive power reference value, Q set represents the active power setting value, V mref represents a grid voltage amplitude reference value, V m represents an actual grid voltage amplitude, K Q represents a first voltage deviation control coefficient, T Q represents a second voltage deviation control coefficient, ΔV set represents the preset voltage deviation threshold, ai represents an operating status of an i th flexible direct current electric power transmission system, Q maxi represents a maximum of reactive power outputted by the i th flexible direct current electric power transmission system, Q i represents an actual reactive power outputted by the i th flexible direct current electric power transmission system, and k is the number of flexible direct current electric power transmission systems participating in voltage regulation.
7 . The method according to claim 1 , wherein the performing the PI control on the actual grid voltage based on the grid voltage amplitude and the phase angle, and acquiring the three-phase voltage reference value through inner-loop control comprises:
performing dq transformation on the grid voltage amplitude based on the phase angle to obtain a d-axis voltage reference value and a q-axis voltage reference value;
performing the PI control on a d-axis component of the actual grid voltage based on the d-axis voltage reference value to obtain a d-axis current reference value, and performing the PI control on a q-axis component of the actual grid voltage based on the q-axis voltage reference value to obtain a q-axis current reference value;
controlling a d-axis component of an actual alternating current to track the d-axis current reference value to obtain a d-axis reference component of a valve voltage, and controlling a q-axis component of the actual alternating current to track the q-axis current reference value to obtain a q-axis reference component of the valve voltage; and
inversely transforming the d-axis reference component and the q-axis reference component of the valve voltage based on the phase angle, to obtain the three-phase voltage reference value.
8 . A non-transitory computer-readable storage medium storing a computer program that, when running, controls a device where the non-transitory computer-readable storage medium is located to perform the method according to claim 1 .
9 . A device for controlling grid configuration of a flexible direct current electric power transmission system, comprising:
a power reference value setting module configured to modify an active power reference value based on a frequency deviation of an alternating current grid, and modify a reactive power reference value based on a voltage deviation of the alternating current grid;
a power control module configured to: control an outputted active power by using a pre-established frequency regulation motion equation of a virtual synchronous machine based on the active power reference value and configure a phase angle; and control an outputted reactive power by using a pre-established voltage regulation motion equation of the virtual synchronous machine based on the reactive power reference value and configure a grid voltage amplitude; and
a voltage-current control module configured to perform PI control on an actual grid voltage based on the grid voltage amplitude and the phase angle and acquire a three-phase voltage reference value through inner-loop control;
wherein the power reference value setting module is further configured to modify the active power reference value based on the frequency deviation of the alternating current grid by:
determining an active power setting value as the active power reference value when it is detected that the frequency deviation of the alternating current grid is less than a preset frequency deviation threshold; and
adding a deviation value of active power that changes with a frequency of the alternating current grid to the active power setting value and determining the obtained sum as the active power reference value when it is detected that the frequency deviation of the alternating current grid is greater than the preset frequency deviation threshold.