CN110970906B - Method and system for coordinated control of reactive voltage of wind power plant - Google Patents

Method and system for coordinated control of reactive voltage of wind power plant Download PDF

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CN110970906B
CN110970906B CN201911071218.5A CN201911071218A CN110970906B CN 110970906 B CN110970906 B CN 110970906B CN 201911071218 A CN201911071218 A CN 201911071218A CN 110970906 B CN110970906 B CN 110970906B
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voltage
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power
wind power
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CN110970906A (en
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孙华东
李文锋
卜广全
许涛
于钊
陶向宇
魏巍
王官宏
贾媛
李莹
张健
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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

Abstract

The invention provides a method and a system for coordinately controlling reactive voltage of a wind power plant. The method and the system measure the voltage of a grid-connected point of a wind power plant and the voltage of a wind turbine generator in the wind power plant, compare the measured value with a preset first threshold interval of normal work, when the grid-connected point of the wind power plant generates transient sudden rise/sudden fall of the voltage in the normal work interval, adjust the optimal voltage value to coordinate reactive power distribution between the SVG and the wind turbine generator in the wind power plant, and when the voltage of the grid-connected point of the wind power plant and the voltage of a generator end exceed the first threshold interval, the SVG and the wind turbine generator in the wind power plant enter an emergency closed-loop control mode to respectively adjust the reactive power. According to the method and the system, the reactive power distribution between the SVG and the wind turbine in the wind power plant is coordinated when the grid-connected point of the wind power plant generates voltage transient sudden rise/sudden fall, so that the transient reactive power supporting capability of the wind power plant when the grid-connected point of the wind power plant generates voltage transient sudden rise/sudden fall is well improved.

Description

Method and system for coordinately controlling reactive voltage of wind power plant
Technical Field
The present invention relates to the field of power control, and more particularly, to a method and system for coordinated control of wind farm reactive voltage.
Background
As one of the most mature and promising renewable energy sources, photovoltaic power generation keeps a strong development trend in recent years, the new energy ratio of some local power grids can reach 80% or even higher in the near future, and the ultrahigh-ratio new energy grid-connected operation becomes an important characteristic of a future power supply structure.
However, as the proportion of new energy in the power grid is higher and higher, the range of influence of the new energy on the power grid is gradually enlarged from part to part. The output of the new energy unit has obvious intermittence and fluctuation, so that the large-scale access of photovoltaic power generation brings great pressure to the stable operation of a local power grid, and the frequent occurrence of large-scale interlocking grid disconnection accidents is caused.
The voltage support index of a grid connection point is achieved by means of SVG when a wind power plant is connected to a power grid at present, and the reactive power regulation capability of a wind power unit in the wind power plant is not fully called. SVG consumes a large amount of station powers in work, influences economic nature, and in the area that a large amount of new forms of energy are incorporated into the power networks, the many points of connection adopt the SVG action simultaneously also can bring the coordination problem that dynamic voltage supported. The key problem to be solved urgently is how to dig the reactive power regulation capability of the new energy unit and improve the reactive power voltage coordination control capability of the new energy station.
Disclosure of Invention
In order to solve the technical problem that the reactive power regulation capability of a wind power plant in the prior art is not fully developed when the wind power plant is connected to a power grid, the invention provides a method for coordinately controlling the reactive voltage of the wind power plant, which comprises the following steps:
step 1, measuring voltage U of grid-connected point of wind power plant T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine generator in the field w ；
Step 2, determining the communication state of the wind power plant station control system and the wind turbine generator in the plant, and adjusting the reactive power of the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the plant according to the communication state, wherein when the communication fault occurs between the wind power plant station control system and the wind turbine generator in the plant, the SVG of the wind power plant and the wind turbine generator in the plant carry out first reactive power adjustment, and when the communication between the wind power plant station control system and the wind turbine generator in the plant is normal, the voltage U of the grid-connected point of the wind power plant is adjusted T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether the static var generator SVG of the wind power plant and the wind turbine in the plant carry out second reactive power regulation when the preset first machine end voltage threshold value interval exists, and when the wind power plant control system and the wind turbine in the plant are in normal communication, the voltage U of the grid-connected point of the wind power plant T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage of the first machine terminal is not within a preset threshold interval of the voltage of the first machine terminal, a Static Var Generator (SVG) of the wind power plant and a wind power generator set in the plant carry out third reactive power regulation;
step 3, when the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the farm carry out third reactive power regulation, respectively measuring the voltage U 'of the grid-connected point of the wind power plant after the SVG and the wind turbine generator in each farm enter a voltage emergency control mode and carry out power regulation' T Wind turbine generator terminal voltage U 'in wind power plant' w Voltage U 'at wind farm grid-connected point' T In a preset second SVG voltage threshold interval or in-situ wind generating set terminal voltage U' w Returning to the step 1 when the preset second generator-side voltage threshold interval is reached, and obtaining the voltage U 'of the wind power plant grid-connected point' T Is not in the preset second SVG voltage threshold interval or in-situ wind motorGroup terminal voltage U' w And returning to the step 2 when the voltage is not in the preset second terminal voltage threshold interval.
Further, when the wind power station control system and the wind turbine generator in the field have a communication fault, the SVG and the wind turbine generator in the field perform first reactive power regulation, namely when the wind power station control system and the wind turbine generator in the field have a communication fault, the SVG and the wind turbine generator in the field enter a voltage closed-loop control mode, and the SVG reads the voltage U of the grid-connected point of the wind power station according to the wind power station control system T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w The reactive power emitted is regulated.
Further, when the communication between the wind power station control system and the wind turbine in the station is normal, the voltage U of the grid-connected point of the wind power station T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether in the preset first machine terminal voltage threshold interval, the second reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system and the wind power generator in the plant are in normal communication, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining an optimal value of reactive power of an in-plant wind turbine generator and an optimal value of reactive power of an SVG (static var generator) of a wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the in-plant wind turbine generator;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold interval is reached, the SVG adjusts power according to an SVG reactive power optimal value sent by a wind power plant station control system;
when the terminal voltage U is w And when a preset first machine end voltage threshold value interval is obtained, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the wind farm station control system to carry out power regulation.
Further, when the wind power plant station control system and the wind power generator set in the plant are in normal communication, the voltage U of the wind power plant grid-connected point T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage threshold value interval of the first machine terminal is not preset, the third reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out;
when the wind power station control system is normally communicated with the wind turbine generator in the plant, and the generator terminal voltage U of the wind turbine generator in the plant w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Power regulation is performed.
Further, when the wind power plant station control system and the wind power generator set in the plant are in normal communication, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of a wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant; step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure BDA0002260991430000041
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure BDA0002260991430000042
in the formula, V i And V j Respectively representing the voltages of node i and node j, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrangian function based on the target function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure BDA0002260991430000043
wherein λ is 1 ，λ 2 And λ 3 Are all Lagrange multipliers,. DELTA.P i Is the active power error of node i, Q svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
step 4, obtaining conditions according to Lagrange extremum
Figure BDA0002260991430000044
Figure BDA0002260991430000045
Figure BDA0002260991430000046
Figure BDA0002260991430000047
Figure BDA0002260991430000051
And 5, when a current collecting line in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrangian function, and taking the solution of the equation set as a reactive power optimal value of the wind turbine generator in each plant and a SVG (static var generator) reactive power optimal value, wherein when the solution of the node exceeds the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant, the inequality constraint condition is converted into an equality constraint, and the value of the inequality constraint condition is the boundary value of the constraint condition.
Further, the establishing of an equality constraint condition of the alternating current line, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant includes:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC line equality constraint condition of each node is constructed, wherein the constraint condition is that the active power error delta P of the node is enabled i And reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by superior scheduling, an equality constraint condition of the active power and the voltage of a wind power plant grid-connected point is established;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of the wind turbine generator and the SVG in the wind power plant, respectively constructing the upper and lower limit constraint conditions of the voltage of each node in the wind power plant and the upper and lower limit constraint conditions of the reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower voltage limits, Q, respectively, of node i wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper limit and the lower limit of the SVG reactive power.
Further, when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
when the wind power station control system and the wind power generator in the station are in normal communication, and the generator terminal voltage U of the wind power generator in the station is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Performing power regulation is referred to asTerminal voltage U of wind turbine generator in each station w And carrying out PI control, and carrying out reactive power regulation according to the output value of the PI control.
Furthermore, the range of the first SVG voltage threshold interval is larger than the second SVG voltage threshold interval, and the first machine terminal voltage threshold interval is larger than the second machine terminal voltage threshold interval.
According to another aspect of the invention, there is provided a system for coordinated control of reactive voltage of a wind farm, the system comprising:
a data acquisition unit for measuring voltage U of wind power plant grid-connected point T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine generator in the field w ；
The data communication unit is used for carrying out data communication between the wind power plant station control system and each inverter in the wind power plant and determining the communication state between the wind power plant station control system and a wind turbine generator in the plant;
the first power adjusting unit is used for performing first passive power adjustment on the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the wind power plant when a communication fault occurs between the station control system of the wind power plant and the wind turbine generator in the plant;
a second power regulating unit, which is used for the voltage U of the wind power plant grid-connected point when the communication between the wind power plant station control system and the wind power set in the plant is normal T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether the first machine terminal voltage threshold interval is preset or not is judged, and second reactive power regulation is carried out on a Static Var Generator (SVG) of the wind power plant and a wind power unit in the plant;
a third power regulating unit, which is used for regulating the voltage U of the grid-connected point of the wind power plant when the communication between the wind power plant station control system and the wind power set in the plant is normal T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage is not in the preset first machine terminal voltage threshold interval, the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant carry out third reactive power regulation;
coordinated control unit for lightWhen the SVG and the in-station inverter of the photovoltaic power station carry out third reactive power regulation, the data acquisition unit respectively measures the voltage U 'of the grid-connected point of the photovoltaic power station after the SVG and the in-station inverter enter a voltage emergency control mode and carry out power regulation' T And the terminal voltage U 'of the in-station inverter' w When voltage U 'of grid-connected point of photovoltaic power station' T In a preset second SVG voltage threshold interval or in-station inverter terminal voltage U' w Returning to the second power unit when a preset second generator terminal voltage threshold interval is reached, and when the voltage U 'of a grid-connected point of the photovoltaic power station' T Is not in a preset second SVG voltage threshold interval or is in an in-station inverter terminal voltage U' w And when the voltage is not in the preset second terminal voltage threshold interval, returning to the third power regulation unit to continue the third reactive power regulation.
Furthermore, the first power adjusting unit is used for adjusting the first reactive power of the Static Var Generator (SVG) of the wind power plant and the wind power generator in the wind power plant when the communication between the wind power plant station control system and the wind power generator in the plant fails, that is, when the communication between the wind power plant station control system and the wind power generator in the plant fails, the SVG of the wind power plant and the wind power generator in the plant enter a voltage closed-loop control mode, and the SVG reads the voltage U of the grid-connected point of the wind power plant according to the wind power plant station control system T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w The reactive power emitted is regulated.
Further, the second power regulating unit is used for enabling the voltage U of the wind power plant grid-connected point to be normal when the wind power plant station control system and the wind turbine generator in the plant are in communication T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether in the preset first machine terminal voltage threshold interval, the second reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power station control system and the wind turbine generator in the station are in normal communication, the wind power station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining an optimal value of reactive power of the wind turbine generator in the plant and an optimal value of reactive power of the SVG of the wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the wind turbine generator in the plant;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold interval is reached, the SVG adjusts power according to an SVG reactive power optimal value sent by a wind power plant station control system;
when the terminal voltage U is w And when a preset first machine end voltage threshold value interval is obtained, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the wind farm station control system to carry out power regulation.
Further, the third power regulating unit is used for enabling the voltage U of the wind power plant grid-connected point to be normal when the wind power plant station control system and the wind turbine generator in the plant are in communication T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the first machine terminal voltage threshold value interval is not preset, the third reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out;
when the wind power station control system and the wind power generator in the plant are normally communicated, and the generator terminal voltage U of the wind power generator in the plant is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Power regulation is performed.
Further, when the second power regulating unit is in normal communication with the wind turbine generator in the wind farm station control system, the wind farm station control system is based on the voltage U of the grid-connected point T Wind turbine in parkActive power P, reactive power Q, terminal voltage U w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of a wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure BDA0002260991430000081
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure BDA0002260991430000091
in the formula, V i And V j Respectively representing the voltages of node i and node j, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrange function based on the objective function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure BDA0002260991430000092
wherein λ is 1 ，λ 2 And λ 3 Are all Lagrange multipliers,. DELTA.P i Is the active power error of node i, Q svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
step 4, obtaining conditions according to Lagrange extremum
Figure BDA0002260991430000093
Figure BDA0002260991430000094
Figure BDA0002260991430000095
Figure BDA0002260991430000096
Figure BDA0002260991430000097
And 5, when a current collecting circuit in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrange function, and taking the solution of the equation set as a reactive power optimal value of a wind turbine generator in each plant and a SVG (scalable vector graphics) reactive power optimal value of the wind power plant, wherein when the solution of the node exceeds the constraint conditions of the upper and lower limits of voltage of each node in the wind power plant and the constraint conditions of the upper and lower limits of reactive power of each inverter in the wind power plant, the inequality constraint conditions are converted into equality constraints, and the value of the inequality constraint conditions is a boundary value of the constraint conditions.
Further, the third power adjusting unit establishes an equality constraint condition of the alternating current line, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant, and includes:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC line equality constraint condition of each node is constructed, wherein the constraint condition is that the active power error delta P of the node is enabled i And reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by superior scheduling, an equality constraint condition of the active power and the voltage of a wind power plant grid-connected point is established;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of the wind turbine generator and the SVG in the wind power plant, respectively constructing the upper and lower limit constraint conditions of the voltage of each node in the wind power plant and the upper and lower limit constraint conditions of the reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower voltage limits, Q, respectively, of node i wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper and lower limits of the SVG reactive power output.
Further, the third power adjusting unit serves as a wind power stationThe control system is normally communicated with the wind turbine generator in the wind power plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage is not in a preset first SVG voltage threshold interval, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
the third power regulating unit is used for ensuring that the communication between the wind power station control system and the wind power generator in the plant is normal, and the generator terminal voltage U of the wind power generator in the plant is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w The power regulation refers to the terminal voltage U of the wind turbine generator in each station w And carrying out PI control, and carrying out reactive power regulation according to the output value of the PI control.
Furthermore, the range of the first SVG voltage threshold interval is larger than the second SVG voltage threshold interval, and the first machine terminal voltage threshold interval is larger than the second machine terminal voltage threshold interval.
The method and the system for coordinately controlling the reactive voltage of the wind power plant measure the voltage of a grid-connected point of the wind power plant and the voltage of an inverter in the wind power plant, compare the measured value with a preset first threshold interval for normal operation, when the grid-connected point of the wind power plant generates voltage transient sudden rise/sudden drop in the normal operation interval, perform voltage optimal value adjustment to coordinate reactive power distribution between the SVG and wind power sets in the wind power plant, and when the voltage of the grid-connected point of the wind power plant and the voltage of a generator end exceed the first threshold interval, the SVG and the wind power sets in the wind power plant enter an emergency closed-loop control mode to respectively perform reactive power adjustment. According to the method and the system for coordinately controlling the reactive voltage of the wind power plant, the reactive power distribution between the SVG and the wind power generation sets in the wind power plant is coordinated when the grid-connected point of the wind power plant generates transient sudden voltage rise/drop, so that the transient reactive power supporting capability of the wind power plant is better improved when the grid-connected point of the wind power plant generates transient voltage rise/drop.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a flow chart of a method of coordinated control of wind farm reactive voltage according to a preferred embodiment of the present invention;
fig. 2 is a schematic structural diagram of a system for coordinately controlling reactive voltage of a wind farm according to a preferred embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same unit/element is denoted by the same reference numeral.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their context in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flow chart of a method for coordinated control of reactive voltage of a wind farm according to a preferred embodiment of the present invention. As shown in fig. 1, a method 100 for coordinated control of reactive voltage of a wind farm according to the present preferred embodiment starts with step 101.
In step 101, the voltage U of the grid-connected point of the wind farm is measured T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine in the field w 。
In step 102, the communication state between the wind power station control system and the wind power set in the wind power station is determined according toThe communication state carries out reactive power regulation to wind-powered electricity generation field SVG and wind turbine generator in the place, wherein, when wind-powered electricity generation field station control system and wind turbine generator in the place take place communication failure, wind-powered electricity generation field SVG and wind turbine generator in the place carry out first reactive power regulation, when wind-powered electricity generation field station control system and wind turbine generator in the place communicate normally, the voltage U of wind-powered electricity generation field grid-connection point T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether the static var generator SVG of the wind power plant and the wind turbine in the plant carry out second reactive power regulation when the preset first machine end voltage threshold value interval exists, and when the wind power plant control system and the wind turbine in the plant are in normal communication, the voltage U of the grid-connected point of the wind power plant T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage of the first machine terminal is not within a preset threshold interval of the voltage of the first machine terminal, a Static Var Generator (SVG) of the wind power plant and a wind power generator set in the plant carry out third reactive power regulation;
step 103, when the static var generator SVG of the wind farm and the wind turbine generator in the farm carry out third reactive power regulation, respectively measuring the voltage U 'of the grid-connected point of the wind farm after the SVG and the wind turbine generator in each farm enter the voltage emergency control mode and carry out power regulation' T And wind turbine generator terminal voltage U 'in field' w When voltage U 'of wind power plant grid-connected point' T In a preset second SVG voltage threshold interval or in-situ wind generating set terminal voltage U' w Returning to the step 101 when the preset second generator-side voltage threshold interval is reached, and obtaining the voltage U 'of the wind power plant grid-connected point' T Is not in a preset second SVG voltage threshold value interval or in-situ wind generating set terminal voltage U' w And returning to the step 102 when the voltage is not in the preset second terminal voltage threshold interval.
Preferably, when the communication fault occurs between the wind power station control system and the wind turbine generator in the farm, the SVG of the wind power station and the wind turbine generator in the farm perform the first reactive power regulation, which means that when the communication fault occurs between the wind power station control system and the wind turbine generator in the farm, the SVG of the wind power station and the wind turbine generator in the farm enter the voltageIn a closed-loop control mode, the SVG reads the voltage U of the grid-connected point of the wind power plant according to the station control system of the wind power plant T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w The reactive power emitted is regulated.
Preferably, when the wind power plant station control system and the wind power generator set in the plant are in normal communication, the voltage U of the grid-connected point of the wind power plant T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether in the preset first machine terminal voltage threshold interval, the second reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system and the wind power generator in the plant are in normal communication, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining an optimal value of reactive power of the wind turbine generator in the plant and an optimal value of reactive power of the SVG of the wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the wind turbine generator in the plant;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold interval is reached, the SVG adjusts power according to an SVG reactive power optimal value sent by a wind power plant station control system;
when the terminal voltage U is w And when a preset first machine end voltage threshold value interval is obtained, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the wind farm station control system to carry out power regulation.
Preferably, when the wind power plant station control system and the wind power generator set in the plant are in normal communication, the voltage U of the grid-connected point of the wind power plant T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage threshold value interval of the first machine terminal is not preset, the third reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage is not in a preset first SVG voltage threshold interval, the SVG enters a voltage emergencyIn the control mode, the SVG reactive power optimal value adjusting instruction sent by the wind power plant station control system is locked, and the adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out;
when the wind power station control system and the wind power generator in the plant are normally communicated, and the generator terminal voltage U of the wind power generator in the plant is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Power regulation is performed.
Preferably, when the wind power plant station control system and the wind power generator in the plant are in normal communication, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of a wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure BDA0002260991430000141
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure BDA0002260991430000142
in the formula, V i And V j Respectively representing the voltages of node i and node j, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrangian function based on the target function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure BDA0002260991430000151
wherein λ is 1 ，λ 2 And λ 3 Are all Lagrange multipliers,. DELTA.P i Is the active power error of node i, Q svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
step 4, obtaining conditions according to Lagrange extremum
Figure BDA0002260991430000152
Figure BDA0002260991430000153
Figure BDA0002260991430000154
Figure BDA0002260991430000155
Figure BDA0002260991430000156
And 5, when a current collecting line in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrangian function, and taking the solution of the equation set as a reactive power optimal value of the wind power generator set in each plant and a SVG (static var generator) reactive power optimal value of the wind power plant, wherein when the solution of the node exceeds the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant, the inequality constraint condition equation is converted into constraint, and the value of the inequality constraint condition equation is taken as a boundary value of the constraint condition. Specifically, in the chain structure of the collecting lines in the wind power plant, at most one branch is arranged between every two nodes, and no loop is formed, so that the total number of the branches in the network is N-1, the number of the unknown variables in the lagrangian function is M +2N, and in the same way, the number of equations which can be obtained according to the lagrangian extreme value calculation condition is also M +2N, and the equations have unique solutions. The wind power plant control system replaces the reactive power of the SVG in the wind power plant by the reactive power of the wind power generation set in the plant through calculating the reactive adjustable capacity of the wind power generation set in the plant and the transmission capacity of the line, so that the active loss of the reactive power compensation device in the wind power plant is reduced, and the overall economic benefit of the wind power plant is improved.
Preferably, the establishing of the equality constraint condition of the alternating current line, the equality constraint condition of the active power and the voltage of the grid-connected point of the wind power plant, the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant, and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant includes:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC line equality constraint condition of each node is constructed, wherein the constraint condition is that the active power error delta P of the node is enabled i And reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by superior scheduling, an equality constraint condition of the active power and the voltage of a wind power plant grid-connected point is established;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of wind turbine generators and SVG in a wind power plant, respectively constructing constraint conditions of upper and lower limits of voltage of each node in the wind power plant and constraint conditions of upper and lower limits of reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower voltage limits, Q, respectively, of node i wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper and lower limits of the SVG reactive power output.
Preferably, when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
when the wind power station control system and the wind power generator in the station are in normal communication, and the generator terminal voltage U of the wind power generator in the station is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters the electric compactionIn the emergency control mode, an intra-plant wind turbine generator reactive power optimal value instruction sent by a wind power plant station control system is locked, and the regulated power Q of the intra-plant wind turbine generator is calculated w The power regulation is based on the terminal voltage U of the wind turbine generator in each station w And carrying out PI control, and carrying out reactive power regulation according to the output value of the PI control.
Preferably, the range of the first SVG voltage threshold interval is greater than the second SVG voltage threshold interval, and the first terminal voltage threshold interval is greater than the second terminal voltage threshold interval. Specifically, when the first SVG voltage threshold interval is 0.93pu to 1.07, the second SVG voltage threshold interval may be 0.95pu to 1.05 pu. The interval that makes the scope of first voltage interval be greater than the second voltage range has avoided when carrying out the distribution of reactive voltage to SVG and wind turbine generator system in the place, voltage vibrates back and forth at the boundary value of first voltage threshold value always, has improved the efficiency of voltage distribution.
Fig. 2 is a schematic structural diagram of a system for coordinately controlling reactive voltage of a wind farm according to a preferred embodiment of the present invention. As shown in fig. 2, the system 200 for coordinately controlling the reactive voltage of the wind farm according to the present preferred embodiment includes:
a data acquisition unit 201 for measuring the voltage U of the wind farm grid connection point T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine generator in the field w ；
The data communication unit 202 is used for carrying out data communication between the wind power plant station control system and each inverter in the wind power plant and determining the communication state between the wind power plant station control system and a wind turbine generator in the plant;
the first power adjusting unit 203 is used for performing first reactive power adjustment on the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the wind power plant when the communication fault occurs between the wind power plant station control system and the wind turbine generator in the plant;
a second power adjusting unit 204, configured to, when the wind farm station control system is in normal communication with the wind turbine in the farm, obtain a voltage U of a grid-connected point of the wind farm T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether the first machine terminal voltage threshold interval is preset or not is judged, and second reactive power regulation is carried out on a Static Var Generator (SVG) of the wind power plant and a wind power unit in the plant;
a third power adjusting unit 205, configured to, when the wind farm station control system is in normal communication with the wind turbine in the farm, obtain a voltage U of a grid-connected point of the wind farm T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage is not in the preset first machine terminal voltage threshold interval, the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant carry out third reactive power regulation;
and the coordination control unit is used for measuring the voltage U 'of the photovoltaic power station grid-connected point after the SVG and the inverters in the stations enter a voltage emergency control mode and perform power regulation respectively through the data acquisition unit when the SVG and the inverters in the stations perform third reactive power regulation' T And the terminal voltage U 'of the in-station inverter' w When voltage U 'of grid-connected point of photovoltaic power station' T In a preset second SVG voltage threshold interval or in-station inverter terminal voltage U' w Returning to the second power unit when a preset second generator-side voltage threshold interval exists, and obtaining the voltage U 'of the grid-connected point of the photovoltaic power station' T Is not in a preset second SVG voltage threshold interval or is in an in-station inverter terminal voltage U' w And when the voltage is not in the preset second terminal voltage threshold interval, returning to the third power regulation unit to continue the third reactive power regulation.
Preferably, the first power adjusting unit 203 is configured to, when a communication fault occurs between the wind farm station control system and the wind turbine in the farm, perform first reactive power adjustment on the static var generator SVG of the wind farm and the wind turbine in the farm, that is, when a communication fault occurs between the wind farm station control system and the wind turbine in the farm, the static var generator SVG of the wind farm and the wind turbine in the farm enter a voltage closed-loop control mode, and the SVG reads the voltage U of the grid-connected point of the wind farm according to the wind farm station control system T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w The reactive power emitted is regulated.
Preferably, the second power adjusting unit 204 is configured to, when the wind farm station control system and the wind turbine generator in the farm are in normal communication, obtain the voltage U of the grid-connected point of the wind farm T In a preset first SVG voltage threshold interval, and the terminal voltage U w Whether in the preset first machine terminal voltage threshold interval, the second reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system and the wind power generator in the plant are in normal communication, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining an optimal value of reactive power of an in-plant wind turbine generator and an optimal value of reactive power of an SVG (static var generator) of a wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the in-plant wind turbine generator;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold interval is reached, the SVG adjusts power according to an SVG reactive power optimal value sent by a wind power plant station control system;
when the terminal voltage U is w And when a preset first machine end voltage threshold value interval is obtained, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the wind farm station control system to carry out power regulation.
Preferably, the third power adjusting unit 205 is configured to, when the wind farm station control system and the wind turbine in the farm are in normal communication, obtain the voltage U of the grid-connected point of the wind farm T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage threshold value interval of the first machine terminal is not preset, the third reactive power regulation of the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant comprises the following steps:
when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out;
when the wind power station control system and the wind power generator in the plant are normally communicated, and the generator terminal voltage U of the wind power generator in the plant is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Power regulation is performed.
Preferably, when the wind farm station control system and the wind turbine generator in the farm are in normal communication, the wind farm station control system is based on the voltage U of the grid-connected point by the second power adjusting unit 204 T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of a wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure BDA0002260991430000191
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure BDA0002260991430000192
in the formula, V i And V j Respectively representing the voltages of node i and node j, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrangian function based on the target function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure BDA0002260991430000201
wherein λ is 1 ，λ 2 And λ 3 Are all Lagrange multipliers,. DELTA.P i Is the active power error of node i, Q svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
step 4, obtaining conditions according to Lagrange extremum
Figure BDA0002260991430000202
Figure BDA0002260991430000203
Figure BDA0002260991430000204
Figure BDA0002260991430000205
Figure BDA0002260991430000206
And 5, when a current collecting line in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrangian function, and taking the solution of the equation set as a reactive power optimal value of the wind turbine generator in each plant and a SVG (static var generator) reactive power optimal value, wherein when the solution of the node exceeds the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant, the inequality constraint condition is converted into an equality constraint, and the value of the inequality constraint condition is the boundary value of the constraint condition.
Preferably, the third power adjusting unit 205 establishes an equality constraint condition of an ac line, an equality constraint condition of active power and voltage at a grid-connected point of a wind farm, a constraint condition of upper and lower limits of voltage of each node in the wind farm, and a constraint condition of upper and lower limits of reactive power of each inverter in the wind farm include:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC circuit equality constraint condition of each node is established, wherein the constraint condition is that the active power error delta P of the node is enabled i And reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by superior scheduling, an equality constraint condition of the active power and the voltage of a wind power plant grid-connected point is established;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of the wind turbine generator and the SVG in the wind power plant, respectively constructing the upper and lower limit constraint conditions of the voltage of each node in the wind power plant and the upper and lower limit constraint conditions of the reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower voltage limits, Q, respectively, of node i wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper and lower limits of the SVG reactive power output.
Preferably, the third power adjusting unit 205 is configured to, when the wind farm station control system is in normal communication with the wind turbine in the farm, determine the voltage U of the grid-connected point of the wind farm T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
when the wind power plant station control system is in normal communication with the wind power generator in the plant, the third power regulating unit 205 regulates the wind power plant station control system to control the wind power generator in the plant according to the wind power plant station control system and the wind power generator terminal voltage U of the wind power generator in the plant w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w The power regulation is based on the terminal voltage U of the wind turbine generator in each station w And carrying out PI control, and carrying out reactive power regulation according to the output value of the PI control.
Preferably, the range of the first SVG voltage threshold interval is greater than the second SVG voltage threshold interval, and the first terminal voltage threshold interval is greater than the second terminal voltage threshold interval.
The step of the system for coordinately controlling the reactive voltage of the wind power plant to coordinately control the SVG of the wind power plant and the reactive voltage of the wind turbine generator in the plant is the same as the step of the method for coordinately controlling the reactive voltage of the wind power plant, the technical effect is the same, and the details are not repeated herein.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ means, component, etc ]" are to be interpreted openly as referring to at least one instance of said means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A method for coordinated control of reactive voltage of a wind farm, the method comprising:
step 1, measuring voltage U of grid-connected point of wind power plant T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine in the field w ；
Step 2, determining the communication state of the wind power plant station control system and the wind turbine generator in the plant, and adjusting the reactive power of the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the plant according to the communication state, wherein:
station control system of wind power plant and plantWhen the wind turbine generator has a communication fault, the Static Var Generator (SVG) of the wind power plant and the wind turbine generator in the wind power plant carry out first reactive power regulation, wherein the first reactive power regulation refers to that the SVG of the wind power plant and the wind turbine generator in the wind power plant enter a voltage closed-loop control mode, and the SVG reads the voltage U of the grid-connected point of the wind power plant according to the station control system of the wind power plant T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w Adjusting the reactive power emitted;
when the wind power plant station control system and the wind turbine generator in the plant are in normal communication, the voltage U of the wind power plant grid-connected point T In a preset first SVG voltage threshold interval, and the terminal voltage U w When a preset first machine end voltage threshold value interval is reached, a Static Var Generator (SVG) of a wind power plant and a wind power unit in the wind power plant carry out second reactive power regulation, and the method comprises the following steps:
when the wind power plant station control system and the wind power generator in the plant are normally communicated, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining an optimal value of reactive power of an in-plant wind turbine generator and an optimal value of reactive power of an SVG (static var generator) of a wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the in-plant wind turbine generator;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold interval is reached, the SVG adjusts power according to an SVG reactive power optimal value sent by a wind power plant station control system;
when the terminal voltage U is w When a preset first machine terminal voltage threshold value interval is reached, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the station control system of the wind farm to carry out power regulation;
when the wind power plant station control system and the wind turbine generator in the plant are in normal communication, the voltage U of the wind power plant grid-connected point T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the first machine terminal voltage threshold value interval is not preset, the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant carry out third reactive power regulation, and the third reactive power regulation comprises the following steps:
when wind blowsThe electric field station control system is normally communicated with the wind turbine generator in the electric field, and the voltage U of the grid-connected point of the wind turbine generator is normal T When the voltage threshold value interval of the first SVG is not preset, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out, and the regulated power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
when the wind power station control system and the wind power generator in the plant are normally communicated, and the generator terminal voltage U of the wind power generator in the plant is normal w When the voltage is not in the preset first machine end voltage threshold interval, the wind turbine generator in the field enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the field, which is sent by the wind power plant station control system, is locked, and the adjusting power Q of the wind turbine generator in the field is calculated w Performing power regulation, and calculating the regulated power Q of the wind turbine in the farm w The power regulation is based on the terminal voltage U of the wind turbine generator in each station w Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
and 3, when the static var generator SVG of the wind power plant and the wind power units in the fields carry out third reactive power regulation, respectively measuring the voltage U 'of the wind power plant grid-connected point after the SVG and the wind power units in the fields enter a voltage emergency control mode and carry out power regulation' T And wind turbine generator terminal voltage U 'in field' w Voltage U 'at wind farm grid-connected point' T In a preset second SVG voltage threshold interval or in-situ wind generating set terminal voltage U' w Returning to the step 1 when the preset second generator-side voltage threshold interval is reached, and obtaining the voltage U 'of the wind power plant grid-connected point' T Is not in a preset second SVG voltage threshold range or terminal voltage U 'of an on-site wind turbine set' w And returning to the step 2 when the voltage is not in the preset second terminal voltage threshold interval.
2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,the method is characterized in that when the wind power station control system and the wind turbine generator in the station are in normal communication, the wind power station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and terminal voltage U of wind turbine in field w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing equality constraint conditions of an alternating current line, equality constraint conditions of active power and voltage of a grid-connected point of a wind power plant, constraint conditions of upper and lower limits of voltage of each node in the wind power plant and constraint conditions of upper and lower limits of reactive power of each inverter in the wind power plant;
step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure FDA0003676889700000031
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure FDA0003676889700000032
in the formula, V i And V j Representing the voltages at node i and node j, respectively, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrangian function based on the target function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure FDA0003676889700000033
wherein λ is 1 ，λ 2 And λ 3 Are all Lagrange multipliers, Δ P i Is the active power error of node i, Q svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
step 4, obtaining conditions according to Lagrange extremum
Figure FDA0003676889700000041
Figure FDA0003676889700000042
Figure FDA0003676889700000043
Figure FDA0003676889700000044
Figure FDA0003676889700000045
And 5, when a current collecting line in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrangian function, and taking the solution of the equation set as a reactive power optimal value of the wind turbine generator in each plant and a SVG (static var generator) reactive power optimal value, wherein when the solution of the node exceeds the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant, the inequality constraint condition is converted into an equality constraint, and the value of the inequality constraint condition is the boundary value of the constraint condition.
3. The method of claim 2, wherein the establishing of the equality constraint of the alternating current line, the equality constraint of the active power and the voltage of the grid-connected point of the wind power plant, the constraint of the upper and lower limits of the voltage of each node in the wind power plant and the constraint of the upper and lower limits of the reactive power of each inverter in the wind power plant comprises:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC circuit equality constraint condition of each node is established, wherein the constraint condition is that the active power error delta P of the node is enabled i And a reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by upper-level scheduling, equation constraint conditions of active power and voltage of a grid-connected point of a wind power plant are constructed;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of the wind turbine generator and the SVG in the wind power plant, respectively constructing the upper and lower limit constraint conditions of the voltage of each node in the wind power plant and the upper and lower limit constraint conditions of the reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower voltage limits, Q, respectively, of node i wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper limit and the lower limit of the SVG reactive power.
4. The method of claim 1, wherein the range of the first SVG voltage threshold interval is greater than the second SVG voltage threshold interval, and the first machine side voltage threshold interval is greater than the second machine side voltage threshold interval.
5. A system for coordinated control of reactive voltage of a wind farm, the system comprising:
a data acquisition unit for measuring voltage U of wind power plant grid connection point T And measuring the active power P, the reactive power Q and the terminal voltage U output by the wind turbine generator in the field w ；
The data communication unit is used for carrying out data communication between the wind power plant station control system and each inverter in the wind power plant and determining the communication state between the wind power plant station control system and a wind turbine generator in the plant;
the first power adjusting unit is used for adjusting first passive power of the Static Var Generator (SVG) of the wind power plant and the wind turbine in the wind power plant when the communication fault occurs between the station control system of the wind power plant and the wind turbine in the wind power plant, wherein the first passive power adjustment means that the SVG of the wind power plant and the wind turbine in the wind power plant enter a voltage closed-loop control mode, and the SVG reads the voltage U of the grid-connected point of the wind power plant according to the station control system of the wind power plant T Regulating the generated reactive power according to the terminal voltage U of the wind turbine in the field w Adjusting the reactive power emitted;
a second power regulating unit, which is used for the voltage U of the wind power plant grid-connected point when the communication between the wind power plant station control system and the wind power set in the plant is normal T In a preset first SVG voltage threshold interval, and the terminal voltage U w When a preset first machine end voltage threshold value interval is adopted, a Static Var Generator (SVG) of a wind power plant and a wind power unit in the wind power plant are subjected toPerforming a second reactive power adjustment comprising:
when the wind power plant station control system and the wind power generator in the plant are normally communicated, the wind power plant station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and terminal voltage U of wind turbine in field w Determining an optimal value of reactive power of an in-plant wind turbine generator and an optimal value of reactive power of an SVG (static var generator) of a wind power plant, and sending the optimal value instruction to the SVG of the wind power plant and the in-plant wind turbine generator;
when the voltage U of the wind power plant grid-connected point T When a preset first SVG voltage threshold value interval is reached, SVG adjusts power according to an SVG reactive power optimal value sent by a station control system of a wind power plant;
when the terminal voltage U is w When a preset first machine terminal voltage threshold value interval is reached, the wind turbine generator in the wind farm receives the optimal reactive power value sent by the wind farm station control system to carry out power regulation;
a third power regulating unit, which is used for regulating the voltage U of the grid-connected point of the wind power plant when the communication between the wind power plant station control system and the wind power set in the plant is normal T Is not in the preset first SVG voltage threshold interval or the terminal voltage U w When the voltage threshold value interval of the first machine terminal is not preset, the Static Var Generator (SVG) of the wind power plant and the wind power generator set in the wind power plant carry out third reactive power regulation, and the third reactive power regulation comprises the following steps:
when the wind power plant station control system is normally communicated with the wind turbine generator in the plant, and the voltage U of the grid-connected point of the wind power plant T When the voltage is not in a preset first SVG voltage threshold interval, the SVG enters a voltage emergency control mode, an SVG reactive power optimal value adjusting instruction sent by a wind power plant station control system is locked, and adjusting power Q of the SVG is calculated SVG Then, power regulation is carried out, and the regulated power Q of the SVG is calculated SVG The later power regulation refers to the voltage U based on the wind power plant grid-connected point T Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
when the wind power station control system and the wind power generator in the plant are normally communicated, and the generator terminal voltage U of the wind power generator in the plant is normal w Not at a preset first machine terminal voltage thresholdWhen the value interval is reached, the wind turbine generator in the plant enters a voltage emergency control mode, the reactive power optimal value instruction of the wind turbine generator in the plant sent by the station control system of the wind farm is locked, and the adjusting power Q of the wind turbine generator in the plant is calculated w Performing power regulation, and calculating the regulated power Q of the wind turbine in the farm w The power regulation is based on the terminal voltage U of the wind turbine generator in each station w Carrying out PI control, and carrying out reactive power regulation according to an output value of the PI control;
and the coordination control unit is used for measuring the voltage U 'of the wind power plant grid-connected point after the SVG and the wind power units in the fields enter the voltage emergency control mode and are subjected to power regulation respectively through the data acquisition unit when the static var generator SVG of the wind power plant and the wind power units in the fields carry out third reactive power regulation' T And wind turbine generator terminal voltage U 'in field' w Voltage U 'at wind farm grid-connected point' T In a preset second SVG voltage threshold interval or in-situ wind generating set terminal voltage U' w Returning to the second power regulating unit when the preset second generator terminal voltage threshold interval exists, and when the voltage U 'of the wind power plant grid-connected point' T Is not in a preset second SVG voltage threshold value interval or in-situ wind generating set terminal voltage U' w And when the voltage is not in the preset second terminal voltage threshold interval, returning to the third power regulation unit to continue the third reactive power regulation.
6. The system of claim 5, wherein when the wind farm station control system and the wind turbine generator in the farm are in normal communication, the wind farm station control system is based on the voltage U of the grid-connected point T Active power P, reactive power Q and generator terminal voltage U of wind turbine generator in field w Determining the optimal value of the reactive power of the wind turbine generator in the power plant and the optimal value of the reactive power of the SVG of the wind power plant comprises the following steps:
step 1, establishing an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of a wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
step 2, constructing a target function of multi-power-supply optimal reactive power output in the wind power plant based on an equality constraint condition of an alternating current circuit, an equality constraint condition of active power and voltage of a grid-connected point of the wind power plant, an upper and lower limit constraint condition of voltage of each node in the wind power plant and an upper and lower limit constraint condition of reactive power of each inverter in the wind power plant;
Figure FDA0003676889700000071
wherein, alpha and beta are weight factors respectively, and satisfy
α+β＝1
P loss.i-j The calculation formula of the active loss between the power grid node i and the power grid node j is as follows:
Figure FDA0003676889700000081
in the formula, V i And V j Respectively representing the voltages of node i and node j, theta ij Representing the voltage phase angle difference, G, between grid node i and grid node j ij Representing the conductance parameters of the line between the ith power grid node and the jth power grid node in the node admittance matrix;
step 3, constructing a Lagrangian function based on the target function of the multi-power-supply optimal reactive power output in the wind power plant, wherein the calculation formula is as follows:
Figure FDA0003676889700000082
wherein λ is 1 ，λ 2 And λ 3 Are all lagrange multipliers, Δ P i Is the active power error, Q, of node i svgm Reactive power output P for mth SVG ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively active for wind power plant grid-connected pointPower and voltage;
step 4, obtaining conditions according to Lagrange extremum
Figure FDA0003676889700000083
Figure FDA0003676889700000084
Figure FDA0003676889700000085
Figure FDA0003676889700000086
Figure FDA0003676889700000087
And 5, when a current collecting line in the wind power plant is in a chain structure, solving a solution of an equation set constructed by the Lagrangian function, and taking the solution of the equation set as a reactive power optimal value of the wind turbine generator in each plant and a SVG (static var generator) reactive power optimal value, wherein when the solution of the node exceeds the constraint condition of the upper and lower limits of the voltage of each node in the wind power plant and the constraint condition of the upper and lower limits of the reactive power of each inverter in the wind power plant, the inequality constraint condition is converted into an equality constraint, and the value of the inequality constraint condition is the boundary value of the constraint condition.
7. The system of claim 6, wherein the third power regulating unit establishes equality constraints for the ac line, equality constraints for active power and voltage at the grid-connected point of the wind farm, and constraints for voltage limits at nodes within the wind farm and reactive power limits for inverters within the wind farm include:
according to the topological structure of an electric circuit in a wind power plant, the node types in the wind power plant are divided into nodes only containing wind turbine generators in the plant, nodes only containing SVG and nodes neither containing the wind turbine generators in the plant nor the SVG, and an AC circuit equality constraint condition of each node is established, wherein the constraint condition is that the active power error delta P of the node is enabled i And a reactive power error Δ Q i Equal to 0;
for active power and voltage commands issued by superior scheduling, an equality constraint condition of the active power and the voltage of a wind power plant grid-connected point is established;
P s ＝P ord
V s ＝V ord
wherein, P ord And V ord Active power and voltage commands, P, issued for upper level dispatch respectively s And V s Respectively the active power and the voltage of a wind power plant grid-connected point;
according to the actual operation requirements of the wind turbine generator and the SVG in the wind power plant, respectively constructing the upper and lower limit constraint conditions of the voltage of each node in the wind power plant and the upper and lower limit constraint conditions of the reactive power of each inverter in the wind power plant, wherein the formulas are as follows:
V i.min ≤V i ≤V i.max
Q wk.min ≤Q wk ≤Q wk.max
Q svg.min ≤Q svg.m ≤Q svg.max
in the formula, V i.min And V i.max Upper and lower limits of the voltage at node i, Q wk.min And Q wk.max Respectively the upper and lower limits, Q, of the reactive power output of the wind turbine in the kth station svg.min And Q svg.max Respectively the upper and lower limits of the SVG reactive power output.
8. The system of claim 5, wherein the range of the first SVG voltage threshold interval is greater than the second SVG voltage threshold interval, and wherein the first machine side voltage threshold interval is greater than the second machine side voltage threshold interval.
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