US 2026/0246282 A1 · METHODS OF ROBUST UNIT SCHEDULING FOR TRANSMISSION AND DISTRIBUTION NETWORKS BASED ON FULL FREQUENCY RESPONSE PROCESSES

Abstract

Disclosed is a method of robust unit scheduling for a transmission and distribution network based on a full frequency response process. The method includes: constructing full-process frequency security constraints for three stages of inertia response, primary frequency regulation, and secondary frequency regulation; establishing a two-stage robust unit commitment optimization model for the transmission and distribution network with a min-max-min structure that considers the full frequency response process, with objectives of minimizing start-stop costs, generation costs, and primary and secondary frequency regulation reserve costs; and transforming the two-stage robust unit commitment optimization model for the transmission and distribution network into a mixed-integer second-order cone programming model by using a column-and-constraint generation algorithm and a strong duality theory, followed by iterative solution.

A method of robust unit scheduling for a transmission and distribution network based on a full frequency response process, comprising:

establishing a framework structure of the transmission and distribution network, taking into account start-stop states of thermal power units, and analyzing a dynamic frequency response process in which centralized renewable energy units and distributed energy resources jointly provide frequency support together with the thermal power units, wherein full-process frequency security constraints are constructed for three stages including inertia response, primary frequency regulation, and secondary frequency regulation;
wherein the full-process frequency security constraints include primary frequency regulation security constraints and secondary frequency regulation security constraints;
the primary frequency regulation security constraints include:
a Rate of Change of Frequency (RoCoF) constraint, wherein when a power deficit begins to occur in a transmission and distribution network system, a system frequency deviation Δft≈0, at which time no units in the transmission and distribution network system have taken action, and a system rate of change of frequency is required to satisfy a maximum allowable requirement, wherein a system inertia time constant is jointly determined by inertia time constants of all dispatchable frequency regulation resources within the transmission and distribution network system, and the RoCoF constraint is expressed as:
RoCoF
=
∂
Δ
⁢
f
t
∂
t
=
❘
"\[LeftBracketingBar]"
Δ
⁢
P
L
,
t
❘
"\[RightBracketingBar]"
·
f
0
2
⁢
H
g
,
t
≤
RoCo
⁢
F
max
wherein RoCoF denotes the system rate of change of frequency;
Δft denotes a system frequency deviation after an occurrence of the power deficit at a time t;
f0 denotes a system nominal frequency;
ΔPL,t denotes a system power deficit;
Hg,t denotes a system inertia time constant at the time t;
RoCoFmax denotes the maximum allowable requirement of the system rate of change of frequency;
a frequency nadir constraint, wherein the inertia response and the primary frequency regulation jointly act to cause a system frequency to decrease to a frequency nadir, during which each unit is required to reserve a primary frequency regulation reserve capacity to participate in the primary frequency regulation so as to prevent the system frequency deviation after the occurrence of the power deficit at the time t from exceeding a given safety threshold, and the system frequency is expressed as:
❘
"\[LeftBracketingBar]"
Δ
⁢
f
nadir
,
t
❘
"\[RightBracketingBar]"
=
2
⁢
R
t
P
⁢
H
g
,
t
T
d
P
(
D
⁢
P
t
D
)
2
⁢
log
⁡
(
2
⁢
R
t
P
⁢
H
g
,
t
T
d
P
⁢
D
⁢
P
t
D
⁢
Δ
⁢
P
L
,
t
′
+
2
⁢
R
t
P
⁢
H
g
,
t
)
+
Δ
⁢
P
L
,
t
′
D
⁢
P
t
D
+
Δ
⁢
f
D
⁢
B
≤
Δ
⁢
f
max
wherein |Δfnadir,t| denotes the system frequency deviation at the time t;
R
t
P
denotes a sum of primary frequency regulation reserve capacities of units in the transmission and distribution network system at the time t;
T
d
P
denotes a response time of the primary frequency regulation of the transmission and distribution network system;
D denotes a load damping coefficient;
P
t
D
denotes a system load;
Δ
⁢
P
L
,
t
′
denotes power deficit of the transmission and distribution network system when entering the inertia response at the time t;
ΔfDB denotes a frequency dead band;
Δfmax denotes the given safety threshold;
a quasi-steady-state frequency constraint, wherein when the primary frequency regulation reserve capacities of the units in the transmission and distribution network system are fully released, the system frequency is maintained at a quasi-steady-state frequency, and a quasi-steady-state frequency deviation at the time t is required to be controlled within a maximum allowable range
Δ
⁢
f
q
⁢
s
⁢
s
max
of the transmission and distribution network system, and the quasi-steady-state frequency constraint is expressed as:
❘
"\[LeftBracketingBar]"
Δ
⁢
f
qss
,
t
❘
"\[RightBracketingBar]"
=
Δ
⁢
P
L
,
t
-
R
t
P
D
⁢
P
t
D
≤
Δ
⁢
f
q
⁢
s
⁢
s
max
;
wherein |Δfqss,t| denotes the quasi-steady-state frequency deviation at the time t;
the secondary frequency regulation security constraints include:
a secondary frequency regulation reserve capacity constraint, wherein, in order to restore the system frequency to a nominal frequency value by an end of the secondary frequency regulation, a sum of secondary frequency regulation reserve capacities and the primary frequency regulation reserve capacities of the units in the transmission and distribution network system is not less than the system power deficit, and the secondary frequency regulation reserve capacity constraint is expressed as:
R
t
P
+
R
t
S
≥
Δ
⁢
P
L
,
t
;
wherein
R
t
S
denotes a sum of the secondary frequency regulation reserve capacities of the units in the transmission and distribution network system at the time t;
a secondary frequency regulation frequency deviation accumulation constraint, wherein an accumulated amount of secondary frequency regulation frequency deviation in the transmission and distribution network system is required to be maintained within a predetermined range so as to avoid excessive deviation of the system frequency from the nominal frequency value at a beginning of the secondary frequency regulation, and the secondary frequency regulation frequency deviation accumulation constraint is expressed as:
S
⁢
F
⁢
R
min
≤
(
Δ
⁢
P
L
,
t
-
R
t
P
-
R
t
S
)
⁢
t
s
-
2
⁢
σ
2
2
⁢
0
⁢
σ
1
≤
S
⁢
F
⁢
R
max
wherein ts denotes an ending time of the accumulated secondary frequency regulation frequency deviation in the transmission and distribution network system;
σ1 denotes a system frequency deviation coefficient;
σ2 denotes an integral control parameter;
SFRmax and SFRmin denote an upper limit and a lower limit of the accumulated secondary frequency regulation frequency deviation in the transmission and distribution network system, respectively;
constructing an uncertainty set of wind power output and an uncertainty set of photovoltaic power output in an interval form by considering uncertainty of wind power output and uncertainty of photovoltaic power output, establishing a two-stage robust unit commitment optimization model of the transmission and distribution network considering the full-process frequency response with a min-max-min structure, and minimizing a sum of start-stop costs, generation costs, primary frequency regulation reserve costs, and secondary frequency regulation reserve costs as an objective;
and
converting, by using a column-and-constraint generation algorithm and a strong duality theory, the two-stage robust unit commitment optimization model of the transmission and distribution network into a mixed-integer second-order cone programming model, and iteratively solving the mixed-integer second-order cone programming model until an upper bound and a lower bound of an objective function converge, thereby obtaining an optimal unit scheduling scheme under a worst-case scenario of the wind power output and the photovoltaic power output.

289 more elements

Methods of robust unit scheduling for transmission and distribution networks based on full frequency response processes

Life of this patent

Methods of robust unit scheduling for transmission and distribution networks based on full frequency response processes

Life of this patent

Abstract

Claims7