CN111641217B - Reactive voltage control method and system in wind power plant - Google Patents

Reactive voltage control method and system in wind power plant Download PDF

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CN111641217B
CN111641217B CN202010527875.2A CN202010527875A CN111641217B CN 111641217 B CN111641217 B CN 111641217B CN 202010527875 A CN202010527875 A CN 202010527875A CN 111641217 B CN111641217 B CN 111641217B
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voltage
reactive
node
wind power
power plant
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CN111641217A (en
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李文博
孙勇
张世栋
张林利
刘合金
刘洋
王峰
苏国强
李帅
张鹏平
由新红
黄敏
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State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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State Grid Corp of China SGCC
Electric Power Research Institute of State Grid Shandong Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

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Abstract

The application discloses a reactive voltage control method and system in a wind power plant, wherein the method comprises the following steps: the upper layer uses the objective function according to the wind power prediction information
Figure DDA0002534289730000011
The reactive voltage to be controlled in the wind power plant is adjusted within a feasible range, and the lower layer utilizes a formula according to the reactive voltage collected at the current moment and the reactive power of the wind power plant
Figure DDA0002534289730000012
And carrying out droop control on the reactive voltage in the wind power plant according to the reactive power reference value of the wind power plant. The system comprises: the upper control module and the lower control module. Through the application, clean energy can be utilized to the maximum extent, and the quick response of voltage control is realized, so that the reactive voltage control efficiency is improved.

Description

Reactive voltage control method and system in wind power plant
Technical Field
The application relates to the technical field of electrical control of wind power plants, in particular to a reactive voltage control method and system in a wind power plant.
Background
Due to the distribution of wind energy resources, a large number of scaled wind farms are usually far from the load center and are connected by the grid end, and the position is such that the wind farms lack effective voltage support from the system side. When the wind power fluctuates greatly in a short time, severe fluctuation of the voltage of a grid-connected point is easily caused, and even chain grid disconnection accidents can be caused in serious conditions to influence the safe and stable operation of a power grid. The double-fed wind turbine serving as a mainstream machine of the current wind power plant has certain dynamic reactive power compensation capability, so how to fully utilize the double-fed wind turbine to realize reactive power compensation and further realize control on voltage in the wind power plant.
At present, a method for controlling voltage in a wind farm generally includes setting a wind farm filtering, i.e., reactive power compensation device, and performing reactive power optimization on the voltage of a wind farm system. Wherein, compensation arrangement mainly includes two parts: and calculating the dynamic reactive power demand of the system according to the dynamic reactive power supporting capability requirement of the grid-connected operation of the wind power plant by the power grid, and inputting the reactive supporting current of the system to calculate under the lowest voltage drop state. The reactive power optimization of the wind power plant system comprises the following steps: and (4) calculating the condition setting of the control system and the switching criterion of the FC tuning branch of the capacitor.
However, in the existing method for improving the voltage control efficiency of the wind power plant, because voltage reactive power optimization is a reactive power optimization strategy for the system level of the wind power plant, the reactive power optimization of each fan is not specified, the reactive power optimization capability of each fan cannot be fully adjusted, the efficiency of voltage control in the wind power plant is not high enough, and therefore clean energy cannot be utilized to the maximum extent, and the maximization of energy utilization is not facilitated.
Disclosure of Invention
The application provides a reactive voltage control method and system in a wind power plant, and aims to solve the problem that in the prior art, the voltage control efficiency in the wind power plant is not high enough.
In order to solve the technical problem, the embodiment of the application discloses the following technical scheme:
a method of reactive voltage control in a wind farm, the method employing upper and lower tier voltage control, the method comprising:
the upper layer uses the objective function according to the wind power prediction information
Figure BDA0002534289710000021
Adjusting the reactive voltage to be controlled in the wind power plant within a feasible range, wherein the constraint conditions are as follows:
Figure BDA0002534289710000022
max and min are the maximum and minimum values of the corresponding variables, Upsc (k) is the reactive voltage value to be controlled at the future k moment,
Figure BDA0002534289710000023
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power provided by the capacitor; qLRepresenting the reactive power consumed by the inductor;
the lower layer utilizes a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure BDA0002534289710000024
Calculating to obtain a reference value of reactive power of the wind power plant, wherein K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment;
and carrying out droop control on the reactive voltage in the wind power plant according to the reference value of the reactive power of the wind power plant.
Optionally, the upper layer utilizes an objective function based on wind power prediction information
Figure BDA0002534289710000025
Before the reactive voltage to be controlled in the wind farm is regulated within a feasible range, the method further comprises:
and calculating the reactive voltage value to be controlled at the future k moment.
Optionally, the calculating a reactive voltage value to be controlled at a future time k includes:
calculating a voltage sensitivity coefficient by adopting a current injection method;
using a formula based on the voltage sensitivity coefficient
Figure BDA0002534289710000026
Figure BDA0002534289710000027
Calculating to obtain a reactive voltage value to be controlled at the future k moment, wherein Upcc (k) is the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure BDA0002534289710000028
and
Figure BDA0002534289710000029
is the voltage sensitivity coefficient, P is the active power of the wind farm,
Figure BDA00025342897100000210
the predicted maximum output of wind power of one minute in the future.
Optionally, the method for calculating the voltage sensitivity coefficient by using a current injection method includes:
defining a wind power plant system with N nodes, wherein the node 1 is a balanced node, the rest nodes are PQ nodes, and the voltage amplitude of the balanced node keeps V1 equal to Vs 1;
using admittance matrices
Figure BDA00025342897100000211
Establishing a relationship between the voltage and current of the PQ node, wherein i ═ 2, 3, …, N, Y are the self-admittance or the mutual admittance of the respective nodes;
using an impedance matrix based on the admittance matrix
Figure BDA0002534289710000031
Establishing a relation between the voltage and the current of a PQ node, wherein gamma in a first column of the impedance matrix is a corresponding coefficient obtained by inverting the admittance matrix, and Z is the self-impedance or the mutual impedance of the corresponding node;
except for defining a node j, the currents of other nodes are all 0;
using formula Vi＝γi1Vsl+Zij×IjCalculating the voltage of any one of the other nodes, wherein ViIs the voltage at any of the remaining nodes, i, j ═ 2, L, N;
according to the power injected at the node j, the reactive power of the wind power plant and the node voltage, a formula is utilized
Figure BDA0002534289710000032
Figure BDA0002534289710000033
Calculating to obtain the current injected at the node j, wherein the power injected at the node j is PjThe reactive power of the wind power plant at the node j is QjThe node voltage at the node j is Vj；
Using formulas
Figure BDA0002534289710000034
And calculating the sensitivity coefficient of the voltage change of the node i relative to the power injection at the node j.
Optionally, the droop coefficient K takes the value of
Figure BDA0002534289710000035
A reactive voltage control system within a wind farm, the system comprising:
an upper control module for utilizing the objective function according to the wind power prediction information
Figure BDA0002534289710000036
Adjusting the reactive voltage to be controlled in the wind power plant within a feasible range, wherein the constraint conditions are as follows:
Figure BDA0002534289710000037
max and min are the maximum and minimum values of the corresponding variables, Upsc (k) is the reactive voltage value to be controlled at the future k moment,
Figure BDA0002534289710000038
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power provided by the capacitor; qLRepresenting the reactive power consumed by the inductor;
the lower layer control module is used for utilizing a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure BDA0002534289710000039
Calculating to obtain a reference value of reactive power of the wind power plant, wherein K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment;
and the lower layer control module is also used for carrying out droop control on the reactive voltage in the wind power plant according to the reference value of the reactive power of the wind power plant.
Optionally, the system further includes a reactive voltage to be controlled calculation module, configured to calculate a reactive voltage value to be controlled at a future k time.
Optionally, the reactive voltage to be controlled calculation module includes:
the sensitivity coefficient calculation unit is used for calculating a voltage sensitivity coefficient by adopting a current injection method;
a reactive voltage value calculating unit for using a formula according to the voltage sensitivity coefficient
Figure BDA0002534289710000041
Figure BDA0002534289710000042
Calculating to obtain a reactive voltage value to be controlled at the future k moment, wherein Upcc (k) is the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure BDA0002534289710000043
and
Figure BDA0002534289710000044
is the voltage sensitivity coefficient, P is the active power of the wind farm,
Figure BDA0002534289710000045
the predicted maximum output of wind power of one minute in the future.
Optionally, the droop coefficient K takes the value of
Figure BDA0002534289710000046
The technical scheme provided by the embodiment of the application can have the following beneficial effects:
the method comprehensively considers the dynamic characteristics of different supplementary devices, effectively coordinates a capacitor, an inductor and a double-fed fan by adopting a layered voltage control mode of an upper layer and a lower layer, adjusts the reactive voltage to be controlled in the wind power plant in a set feasible range by utilizing the target function according to the wind power prediction information of the upper layer, and realizes the coarse adjustment of the reactive voltage; and then, the lower layer calculates a reactive power reference value of the wind power plant by using a formula according to the reactive voltage acquired at the current moment and the current reactive power of the wind power plant, and finally, droop control is carried out on the reactive voltage in the wind power plant by using the reactive power reference value, so that fine adjustment of the reactive voltage is realized. The switching capacity of the capacitor and the inductor can be determined by fully utilizing wind power prediction information through upper-layer control, so that wind abandonment is effectively avoided, clean energy is utilized to the maximum extent, and reactive voltage control efficiency is improved. Through the droop control of the lower layer, on the basis of local voltage measurement, the quick response of voltage control can be realized, and therefore the reactive voltage control efficiency is improved.
The utility model also provides a reactive voltage control system in wind power plant, this system mainly includes upper control module and lower floor's control module, through hierarchical control's structural design, the upper strata is coarse adjustment control, mainly used according to wind power prediction information, utilizes the objective function to adjust the reactive voltage who treats control in the feasible scope of settlement, through the electric capacity and the inductance control on upper strata for wind power plant can have sufficient reactive power to adjust the reactive voltage who treats control. The lower layer is fine adjustment control, a reactive power reference value of the wind power plant is obtained by utilizing company calculation mainly according to reactive voltage collected at the current moment and reactive power of the wind power plant, droop control is carried out on the reactive voltage in the wind power plant according to the reactive power reference value, and quick response of voltage control can be realized through local droop control of the lower layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a reactive voltage control method in a wind farm according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a reactive voltage control system in a wind farm according to an embodiment of the present application.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
For doubly-fed wind turbines, the reactive power is limited by the limits of the converter operation, QmaxAnd QminIs the maximum value and the minimum value of the reactive power of the wind power plant and respectively depends on the reactive voltage U to be controlledPCCAnd active power output of the wind power plant. When the active output is close to the rated power of the wind power plant, the reactive power is insufficient to adjust UPCC. This embodiment can realize effectual reactive voltage control through upper and lower two-layer voltage control.
For a better understanding of the present application, embodiments of the present application are explained in detail below with reference to the accompanying drawings.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a reactive voltage control method in a wind farm according to an embodiment of the present application. As can be seen from fig. 1, the method for controlling reactive voltage in a wind farm in this embodiment mainly includes the following steps:
s1: the upper layer uses the objective function according to the wind power prediction information
Figure BDA0002534289710000051
And adjusting the reactive voltage to be controlled in the wind power plant within a feasible range.
Wherein the constraint conditions are as follows:
Figure BDA0002534289710000052
max and min are the maximum and minimum values of the corresponding variables, Upsc (k) is the reactive voltage value to be controlled at the future k moment,
Figure BDA0002534289710000053
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power provided by the capacitor; qLRepresenting the reactive power consumed by the inductor.
In the embodiment, the reactive voltage to be controlled in the wind farm can be adjusted within a set range through the objective function, wherein the set range is a feasible range in which the wind farm can normally operate and is a rough voltage range. The capacitor and the inductor are used for providing reactive power within a set time scale for the wind power plant, and can provide reactive support for the wind power plant for a long time scale, so that wind abandon is avoided. By setting a target function and constraint adjustment of the target function, the switching capacity of the capacitor and the inductor can be determined according to wind power prediction information.
Further, before step S1, the present embodiment further includes step S0: and calculating the reactive voltage value to be controlled at the future k moment.
Specifically, step S0 further includes:
s01: and calculating a voltage sensitivity coefficient by adopting a current injection method.
The wind power cluster area has a radial structure the same as that of a power distribution network, the voltage grade is low, the R/X value is large, and the voltage sensitivity coefficient calculated by adopting a current injection method can be converged in time, so that the calculation efficiency is improved, and the efficiency of the whole reactive voltage control method is improved.
The method for calculating the voltage sensitivity coefficient by the current injection method comprises the following steps:
s011: a wind farm system having N nodes is defined.
The node 1 is a balanced node, the other nodes are PQ nodes, and the voltage amplitude of the balanced node keeps V1 equal to Vs 1.
S012: using admittance matrices
Figure BDA0002534289710000061
A relationship between the voltage and current of the PQ node is established, where i ═ 2, 3, …, N, Y are the self-admittance or the mutual admittance of the respective nodes.
S013: using impedance matrices based on admittance matrices
Figure BDA0002534289710000062
A relationship between the voltage and current of the PQ node is established. Wherein γ in the first column of the impedance matrix is a corresponding coefficient obtained by inverting the admittance matrix, and Z is the self-impedance or the mutual impedance of the corresponding node.
S014: except for the node j, the currents of the other nodes are 0.
S015: using formula Vi＝γi1Vsl+Zij×IjCalculating the voltage of any one of the other nodes, wherein ViI, j is 2, L, N, which is the voltage of any of the remaining nodes.
S016: according to the power injected at the node j, the reactive power of the wind power plant and the node voltage, a formula is utilized
Figure BDA0002534289710000063
And calculating to obtain the current injected at the node j. Wherein the power injected at the node j is PjThe reactive power of the wind power plant at the node j is QjThe node voltage at the node j is Vj。
S017: using formulas
Figure BDA0002534289710000071
And calculating the sensitivity coefficient of the voltage change of the node i relative to the power injection at the node j.
From steps S016 and S017, the equation
Figure BDA0002534289710000072
Where re represents the real part, im represents the imaginary part, and the variable γ is combinedi1And VslSo that V isγi＝γi1VslThen formula Vi＝γi1Vsl+Zij×IjCan be further expressed as:
Figure BDA0002534289710000073
wherein R isij+jXij＝ZijWherein R isijRepresents ZijReal part of, XijRepresents ZijThe imaginary part of (c).
General formula
Figure BDA0002534289710000074
According to the real part and imaginary part expansion, obtaining
Figure BDA0002534289710000075
And
Figure BDA0002534289710000076
relative to PjAnd QjThe partial derivatives of (a) are:
Figure BDA0002534289710000077
and
Figure BDA0002534289710000078
after the voltage sensitivity coefficient is calculated through the step S01, a step S02 is performed: according to the voltage sensitivity coefficient, using the formula
Figure BDA0002534289710000079
And calculating to obtain a reactive voltage value to be controlled at the future k moment.
Wherein Upcc (k) is the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure BDA00025342897100000710
and
Figure BDA00025342897100000711
is the voltage sensitivity coefficient, P is the active power of the wind farm,
Figure BDA00025342897100000712
the predicted maximum output of wind power of one minute in the future.
According to the formula, the reactive voltage of the wind power plant is simultaneously influenced by active output, capacitance and inductance change, and the control on the reactive voltage of the wind power plant can be more accurately realized by fully considering various influence factors, so that the control efficiency and the reliability of the control method are improved.
As can be seen from fig. 1, after the upper control adjusts the reactive voltage to be controlled in the wind power plant to be within the set range, step S2 is executed: the lower layer utilizes a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure BDA00025342897100000713
And calculating to obtain a reactive power reference value of the air outlet electric field. And K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment.
In this embodiment, the droop coefficient K takes the value of
Figure BDA00025342897100000714
After the reference value of the reactive power of the wind farm is obtained, step S3 is executed: and carrying out droop control on the reactive voltage in the wind power plant according to the reactive power reference value of the wind power plant.
Through steps S2 and S3, local droop control of reactive voltage of the wind power plant is achieved, reactive reference can be provided for the wind power plant according to the measured voltage, and therefore reactive voltage control is achieved more effectively and accurately.
In summary, in this embodiment, through voltage hierarchical control, the wind farm can utilize wind energy to the maximum extent by additionally installing capacitors and inductors or cutting off the capacitors and the inductors, so that wind abandoning is avoided, the utilization rate of clean energy is improved, and the reactive voltage control efficiency is improved. Lower floor's droop control is based on local voltage measurement, can provide quick reactive support, especially under emergency, can in time realize reactive support, is favorable to improving reactive voltage control efficiency.
Example two
Referring to fig. 2 based on the embodiment shown in fig. 1, fig. 2 is a schematic structural diagram of a reactive voltage control system in a wind farm according to an embodiment of the present application. As can be seen from fig. 2, the structure of the reactive voltage control system in the wind farm in this embodiment mainly includes: the upper control module and the lower control module.
Wherein, the upper control module is used for utilizing the objective function according to the wind power prediction information
Figure BDA0002534289710000081
Adjusting the reactive voltage to be controlled in the wind power plant within a feasible range, wherein the constraint conditions are as follows:
Figure BDA0002534289710000082
max and min are the maximum and minimum values of the corresponding variables, Upsc (k) is the reactive voltage value to be controlled at the future k moment,
Figure BDA0002534289710000083
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power, Q, supplied by the capacitorLRepresenting the reactive power consumed by the inductor. The lower layer control module is used for utilizing a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure BDA0002534289710000084
And calculating to obtain a reference value of the reactive power of the wind power plant, wherein K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment. And the lower layer control module is also used for carrying out droop control on the reactive voltage in the wind power plant according to the reactive power reference value of the wind power plant.
Further, the system of this embodiment further includes a reactive voltage to be controlled calculation module, configured to calculate a reactive voltage value to be controlled at a future time k.
The reactive voltage calculation module to be controlled comprises: the device comprises a sensitivity coefficient calculating unit and a reactive voltage value calculating unit. The sensitivity coefficient calculation unit is used for calculating a voltage sensitivity coefficient by adopting a current injection method. A reactive voltage value calculating unit for using a formula according to the voltage sensitivity coefficient
Figure BDA0002534289710000085
Figure BDA0002534289710000086
Calculating to obtain a reactive voltage value to be controlled at the future k moment, wherein Upcc (k) is the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure BDA0002534289710000087
and
Figure BDA0002534289710000088
is the voltage sensitivity coefficient, P is the active power of the wind farm,
Figure BDA0002534289710000089
the predicted maximum output of wind power of one minute in the future.
In this embodiment the droop coefficient K takes the value of
Figure BDA00025342897100000810
The working principle and the working method of the reactive voltage control system in the wind farm in this embodiment have been explained in detail in the embodiment shown in fig. 1, and the two embodiments can be referred to each other, and are not described herein again.
The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (4)

1. A method for controlling reactive voltage in a wind farm, the method using upper and lower tier voltage control, the method comprising:
calculating a reactive voltage value to be controlled at the future k moment;
the upper layer uses the objective function according to the wind power prediction information
Figure FDA0003096995980000011
Adjusting the reactive voltage to be controlled in the wind power plant within a feasible range, wherein the constraint conditions are as follows:
Figure FDA0003096995980000012
max and min are the maximum and minimum values of the corresponding variables, UPCCFor the reactive voltage value to be controlled at the future moment k,
Figure FDA0003096995980000013
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power provided by the capacitor; qLRepresenting the reactive power consumed by the inductor;
the lower layer utilizes a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure FDA0003096995980000014
Calculating to obtain a reference value of reactive power of the wind power plant, wherein K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment;
according to the reference value of the reactive power of the wind power plant, droop control is carried out on the reactive voltage in the wind power plant;
wherein, the calculating the reactive voltage value to be controlled at the future k moment comprises:
calculating a voltage sensitivity coefficient by adopting a current injection method;
using a formula based on the voltage sensitivity coefficient
Figure FDA0003096995980000015
Figure FDA0003096995980000016
Calculating to obtain a reactive voltage value to be controlled at the future k moment, wherein UPCCFor the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure FDA0003096995980000017
and
Figure FDA0003096995980000018
is the voltage sensitivity coefficient, P is the active power of the wind farm，
Figure FDA0003096995980000019
Predicting the maximum output of wind power in one minute in the future, wherein P (0) is the active power of the wind power plant at the starting moment;
the method for calculating the voltage sensitivity coefficient by adopting the current injection method comprises the following steps:
defining a wind power plant system with N nodes, wherein the node 1 is a balance node, the other nodes are PQ nodes, and the voltage amplitude of the balance node is kept V1＝Vsl；
Using admittance matrices
Figure FDA00030969959800000110
Establishing a relationship between the voltage and current of the PQ node, wherein i is 2, 3, N, Y is the self-or mutual-admittance of the respective node, V1To balance the voltage of the nodes, VslIs a set value of the balanced node voltage;
using an impedance matrix based on the admittance matrix
Figure FDA0003096995980000021
Establishing a relationship between the voltage and current of the PQ node, wherein γ in a first column of the impedance matrix is a corresponding coefficient inverted by the admittance matrix, Z is a self-impedance or a mutual impedance of the corresponding node, ViIs the voltage of any one of the other nodes, I, j ═ 2 … … N, IiIs the current of any of the remaining nodes;
except for defining a node j, the currents of other nodes are all O;
using formula Vi＝γi1Vsl+Zij×IjCalculating the voltage of any one of the other nodes, wherein ViIs the voltage at any of the remaining nodes, i, j ═ 2 … … N;
according to the power injected at the node j, the reactive power of the wind power plant and the node voltage, a formula is utilized
Figure FDA0003096995980000022
Figure FDA0003096995980000023
Calculating to obtain the current injected at the node j, wherein the power injected at the node j is PjThe reactive power of the wind power plant at the node j is QjThe node voltage at the node j is Vj，
Figure FDA0003096995980000024
Is the node voltage V at node jjThe real part of (a) is,
Figure FDA0003096995980000025
is the node voltage V at node jjAn imaginary part of (d);
using formulas
Figure FDA0003096995980000026
And calculating the sensitivity coefficient of the voltage change of the node i relative to the power injection at the node j.
2. The reactive voltage control method in the wind power plant according to claim 1, wherein the droop coefficient K takes the value of
Figure FDA0003096995980000027
3. A reactive voltage control system within a wind farm, the system comprising:
an upper control module for utilizing the objective function according to the wind power prediction information
Figure FDA0003096995980000028
Adjusting the reactive voltage to be controlled in the wind power plant within a feasible range, wherein the constraint conditions are as follows:
Figure FDA0003096995980000031
max and min are the maximum and minimum values of the corresponding variables, UPCCFor the reactive voltage value to be controlled at the future moment k,
Figure FDA0003096995980000032
for a target value of reactive voltage to be controlled, QCRepresenting the reactive power provided by the capacitor; qLRepresenting the reactive power consumed by the inductor;
the lower layer control module is used for utilizing a formula according to the reactive voltage acquired at the current moment and the reactive power of the wind power plant
Figure FDA0003096995980000033
Calculating to obtain a reference value of reactive power of the wind power plant, wherein K is a droop coefficient, and Q is the reactive power of the wind power plant at the current moment;
the lower layer control module is also used for carrying out droop control on reactive voltage in the wind power plant according to the reference value of the reactive power of the wind power plant;
the system also comprises a reactive voltage to be controlled calculation module which is used for calculating the reactive voltage value to be controlled at the future k moment;
wherein, the reactive voltage calculation module to be controlled comprises:
the sensitivity coefficient calculation unit is used for calculating a voltage sensitivity coefficient by adopting a current injection method;
a reactive voltage value calculating unit for using a formula according to the voltage sensitivity coefficient
Figure FDA0003096995980000034
Figure FDA0003096995980000035
Calculating to obtain a reactive voltage value to be controlled at the future k moment, wherein UPCCFor the reactive voltage value to be controlled at the future k moment, Upcc (0) is the reactive voltage value at the starting moment,
Figure FDA0003096995980000036
and
Figure FDA0003096995980000037
is the voltage sensitivity coefficient, P is the active power of the wind farm,
Figure FDA0003096995980000038
predicting the maximum output of wind power in one minute in the future, wherein P (0) is the active power of the wind power plant at the starting moment;
the sensitivity coefficient calculation unit firstly defines a wind power plant system with N nodes, wherein the node 1 is a balance node, the other nodes are PQ nodes, and the voltage amplitude of the balance node is kept V1＝Vsl；
Secondly, use of admittance matrix
Figure FDA0003096995980000039
Establishing a relationship between the voltage and current of the PQ node, wherein i is 2, 3, N, Y is the self-or mutual-admittance of the respective node, V1To balance the voltage of the nodes, VslIs a set value of the balanced node voltage;
using an impedance matrix based on the admittance matrix
Figure FDA0003096995980000041
Establishing a relationship between the voltage and current of the PQ node, wherein γ in a first column of the impedance matrix is a corresponding coefficient inverted by the admittance matrix, Z is a self-impedance or a mutual impedance of the corresponding node, ViIs the voltage of any one of the other nodes, I, j ═ 2 … … N, IiIs the current of any of the remaining nodes;
except for defining a node j, the currents of other nodes are all O;
using formula Vi＝γi1Vsl+Zij×IjCalculating the voltage of any one of the other nodes, wherein ViIs the voltage at any of the remaining nodes, i, j ═ 2 … … N;
according to power and wind power injected at the node jField reactive power and node voltage, using formula
Figure FDA0003096995980000042
Figure FDA0003096995980000043
Calculating to obtain the current injected at the node j, wherein the power injected at the node j is PjThe reactive power of the wind power plant at the node j is QjThe node voltage at the node j is Vj，
Figure FDA0003096995980000044
Is the node voltage V at node jjThe real part of (a) is,
Figure FDA0003096995980000045
is the node voltage V at node jjAn imaginary part of (d);
finally, using the formula
Figure FDA0003096995980000046
And calculating the sensitivity coefficient of the voltage change of the node i relative to the power injection at the node j.
4. The reactive voltage control system in a wind farm according to claim 3, wherein the droop coefficient K takes the value of
Figure FDA0003096995980000047
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