US 12,136,816 B2 · Online voltage control method for coordinating multi-type reactive power resources using reactive voltage operation characteristics of power grids

Abstract

An online voltage control method for coordinating multi-type reactive power resources is provided. First, a linearized power flow equation of branch reactive power is established, and an online voltage control model of multi-type reactive power resources including an objective function and constraint conditions is constructed. The constraint conditions includes generator reactive power constraints, reactive power compensator constraints, transformer tap position constraints, a nodal reactive power balance constraint, and slack contained nodal voltage constraints. Then, an optimization result of voltage control is obtained by solving the model. The method makes full use of reactive voltage operation characteristics of a power grid, constructs a practical online solution model for reactive voltage control of large power grid of coordinating multiple reactive power resources, and under a condition of acceptable accuracy loss, takes in account safety of power grid operation, economy of reactive power resource actions and high reliability of online operation.

An online voltage control method for coordinating multi-type reactive power resources, comprising steps:

(1) establishing a variable set Ω of a base-state operation point model of a power system, wherein
Ω={Vn,Vnslackup,Vnslackdown,{tilde over (V)}n,ViG,Qijb,QiG,Qn,Qncp,Qnun,Qnld,Nunitcp,Nunitrc,μunit,Bicp,Bjrc,tiadj_up,tiadj_down}
where, Vn is a voltage after adjustment of a node n, Vnslack_up and Vnslack_down respectively are an up slack variable and a down slack variable of the voltage after adjustment of the node n, {tilde over (V)}n is an adjustment voltage value after slack of the node n, ViG is a voltage of a generator i, Qijb is reactive power flowing into a branch b with ports being nodes i and j from the port being the node i, QiG is reactive power of the generator i, Qn is reactive power of the node n, Qncp is reactive power supplied by a reactive power compensator connected to the node n, Qnun is reactive power supplied by a generator connected to the node n, Qnld is reactive power absorbed by a load connected to the node n, Nunitcp is a number of capacitance compensators in a state of being put in operation under a controller unit, Nunitrc is a number of inductance compensators in a state of being put in operation under the controller unit, μunit is a binary variable of the controller unit, Bicp is a Boolean variable of a capacitance compensator i to indicate the capacitance compensator numbered with i whether changes its operation state, Bjrc is a Boolean variable of an inductance compensator j to indicate the inductance compensator numbered with j whether changes its operation state, tjadj_up is an upwards adjusted tap position of a transformer i, and tiadj_down is a downwards adjusted tap position of the transformer i;
(2) establishing a linearized equation of reactive power of branch, comprising:
for each the branch b, calculating a Jacobi matrix of reactive power of the branch to obtain the following values:
∂
Q
i
⁢
j
b
∂
V
i
,
∂
Q
i
⁢
j
b
∂
V
j
,
∂
Q
j
⁢
i
b
∂
V
i
,
∂
Q
j
⁢
i
b
∂
V
j
,
∂
Q
i
⁢
j
b
∂
t
,
∂
Q
j
⁢
i
b
∂
t
;
where, i and j are node numbers respectively corresponding to two ports of the branch b,
∂
Q
i
⁢
j
b
∂
V
i
is a partial derivative of reactive power of the branch b flowing out from the port node j relative to a voltage Vi after adjustment of the port node i,
∂
Q
i
⁢
j
b
∂
V
j
is a partial derivative of the reactive power of the branch b flowing out from the port node j relative to a voltage Vj after adjustment of the port node j,
∂
Q
j
⁢
i
b
∂
V
i
is a partial derivative of reactive power of the branch b flowing out from the port node i relative to the voltage Vi after adjustment of the port node i,
∂
Q
j
⁢
i
b
∂
V
j
is a partial derivative of the reactive power of the branch b flowing out from the port node i relative to the voltage Vj after adjustment of the port node j,
∂
Q
i
⁢
j
b
∂
t
is a partial derivative of the reactive power of the branch b flowing out from the port node j relative to a tap position t of a transformer connected to the branch b, and
∂
Q
j
⁢
i
b
∂
t
is a partial derivative of the reactive power of the branch b flowing out from the port node i relative to the tap position t of the transformer connected to the branch b;
an expression of the linearized equation of reactive power of the branch b is as follows:
Q
i
⁢
j
b
=
Q
i
⁢
j
⁢
0
b
+
∂
Q
j
⁢
i
b
∂
V
i
·
(
V
i
-
V
i
⁢
0
)
+
∂
Q
j
⁢
i
b
∂
V
j
·
(
V
j
-
V
j
⁢
0
)
+
∂
Q
j
⁢
i
b
∂
t
·
(
t
-
t
0
)
where, Qijb is the reactive power flowing into the branch b from the port node i, Qij0b is an initial reactive power flowing into the branch b from the port node i, Vi0 is an original voltage of the node i, Vj0 is an original voltage of the node j, t is a tap position after adjustment of the transformer connected to the branch b, and t0 is an original tap position of the transformer connected to the branch b;
(3) establishing an online voltage control model of multi-type reactive power resources, wherein the online voltage control model comprises an objective function and constraint conditions, specifically comprising the following steps:
(3-1) establishing an expression of the objective function of the online voltage control model as follows:
minCtotal,
wherein
minCtotal,
wherein,
Ctotal=Σ(Qncp,op·Cncp,op)+Σ(Qnun,adj_up·Cnun,adj_up+Qnun,adj_down·Cnun,adj_down)+Σ(tiadj_up+tiadj_down)·Cit,adj+Σ(Vnslack_up2+Vnslack_down2)·Cp,
where, Ctotal is a sum of a total cost and a penalty term of regulation, Qncp,op is a 0-1 variable of the reactive power compensator connected to the node n whether is put in operation, Cncp,op is a cost of the reactive power compensator connected to the node n in operation, Qnun,adj_up is an amount of upward adjustment of output reactive power of the generator connected to node n, Cnun,adj_up is a cost of upward adjustment of output reactive power of the generator connected to node n, Qnun,adj_down is an amount of downward adjustment of output reactive power of the generator connected to node n, Cnun,adj_down is a cost of downward adjustment of output reactive power of the generator connected to node n, Cit,adj is a cost per unit tap position of adjustment of the transformer i, Σ(Vnslack_up2+Vnslack_down2)·Cp is the penalty term, and Cp is a penalty coefficient of slack variable;
(3-2) establishing the constraint conditions as follows:
(3-2-1) generator reactive power constraints:
when the QC is adjustable, there is a constraint condition:
QiG_min≤QiG≤QiG_max, ∀i∈IG,
where, QiG_min is a lower limit of the reactive power of the generator i, QiG_max is an upper limit of the reactive power of the generator i, and IG is a collection of generators;
when the QiG is non-adjustable and the generator i is a PQ node whose real power P and reactive power Q are specified, there is a constraint condition:
QiG=Qi0G;
when the QiG is non-adjustable and the generator i is a PV node whose real power P and a voltage magnitude V are specified, there is a constraint condition:
ViG=Vi0G,
where, Qi0G and Vi0G respectively are original reactive power and an original voltage of the generator i;
(3-2-2) reactive power compensator constraints:
Nunitcp=Nunitcp0+Σi∈I0Bicp−Σi∈I1Bicp,
where, the controller is a minimum control unit of a group of reactive power compensators, the group of reactive power compensators comprise capacitance compensators and inductance compensators, I0 is a capacitance compensator set in exit state under the controller unit, I1 is a capacitance compensator set in the state of being put in operation under the controller unit, Nunitcp0 is a number of the capacitance compensators in the state of being put in operation under the controller unit at an initial stage;
Nunitrc=Nunitrc0+Σj∈J0Bjrc−Σj∈J1Bjrc,
where, J0 is an inductance compensator set in exit state under the controller unit, J1 is an inductance compensator set in the state of being put in operation under the controller unit, Nunitrc0 is a number of the inductance compensators in the state of being put in operation under the controller unit at the initial stage;
using a big-M method to establish a constraint as follows:
{
0
≤
N
unit
cp
≤
μ
u
⁢
n
⁢
i
⁢
t
⁢
N
u
⁢
n
⁢
i
⁢
t
s
⁢
u
⁢
m
0
≤
N
u
⁢
n
⁢
i
⁢
t
r
⁢
c
≤
(
1
-
μ
u
⁢
n
⁢
i
⁢
t
)
⁢
N
u
⁢
n
⁢
i
⁢
t
s
⁢
u
⁢
m
μ
u
⁢
n
⁢
i
⁢
t
=
0
,
1
where, Nsumunit is a number of all the reactive power compensators under the controller unit;
(3-2-3) slack contained nodal voltage constraints:
{
V
~
n
=
V
n
+
V
n
slack_up
-
V
n
slack_down
V
n
slack_up
,
V
n
slack_down
≥
0
,
when a voltage on the node n has upper and lower limit constraints, there is a constraint condition:
Vnmin≤{tilde over (V)}n≤Vnmax,
when the voltage on the node n has an objective voltage value, there is a constraint condition:
{tilde over (V)}n=Vnobj,
where, Vnmin is an allowable minimum value of the voltage on the node n, Vnmax is an allowable maximum value of the voltage on the node n, and Vnobj is the objective voltage value of the node n;
(3-2-4) transformer tap position constraints:
when a tap of the transformer i is adjustable, there is a constraint condition:
{
t
i
min
≤
t
i
0
+
t
i
adj_up
-
t
i
adj_down
≤
t
i
max
0
≤
t
i
adj_up
,
t
i
adj_down
≤
2
where, timin is a minimum value of the tap position of the transformer i, timax is a maximum value of the tap position of the transformer i, and to is an original value of the tap position of the transformer i;
(3-2-5) a nodal reactive power balance constraint:
Qn=ΣQncp+ΣQnun−ΣQnld−ΣjQnjb=0,
where, ΣQncp is a sum of reactive power flowing in the node n from all the reactive power compensators connected to the node n, ΣQnun is a sum of reactive power flowing in the node n from all generators connected to the node n, ΣQnld is a sum of reactive power of flowing from the node n into all loads connected to the node n, ΣjQnjb is a sum of reactive power of flowing from the node n into all branches each with the node n as its port, and Qnjb is calculated by the linearized equation of reactive power of branch established in the step (2);
(4) solving the online voltage control model of multi-type reactive power resources established in the step (3) to obtain optimal values of respective optimization variables contained in the variable set Ω;
wherein the method further comprises the following steps:
performing the voltage control on the power system based on the obtained optimal values of respective optimization variables contained in the variable set Ω, which comprises:
adjusting the voltage and the reactive power of the node n to the respective optimal values, adjusting the voltage and the reactive power of the generator i to the respective optimal values, adjusting the reactive power supplied by the reactive power compensator connected to the node n to the respective optimal value, adjusting the reactive power supplied by the generator i connected to the node n to the respective optimal value, adjusting the reactive power absorbed by the load connected to the node n to the respective optimal value, adjusting the number of the capacitance compensators in the state of being put in operation under the controller unit to the respective optimal value, adjusting the number of the inductance compensators in the state of being put in operation under the controller unit to the respective optimal value, and adjusting the upwards adjusted tap position and the downwards adjusted tap position of the transformer i to the respective optimal values.

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Online voltage control method for coordinating multi-type reactive power resources using reactive voltage operation characteristics of power grids

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Online voltage control method for coordinating multi-type reactive power resources using reactive voltage operation characteristics of power grids

Life of this patent

Abstract

Claims1