CN108695892A - A kind of distribution network voltage control method adjusted based on photovoltaic DC-to-AC converter - Google Patents

A kind of distribution network voltage control method adjusted based on photovoltaic DC-to-AC converter Download PDF

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CN108695892A
CN108695892A CN201810608230.4A CN201810608230A CN108695892A CN 108695892 A CN108695892 A CN 108695892A CN 201810608230 A CN201810608230 A CN 201810608230A CN 108695892 A CN108695892 A CN 108695892A
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inverter
voltage
power
photovoltaic
access point
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CN108695892B (en
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凌平
王蕾
谢伟
赵艳雷
柳劲松
张勇
方陈
刘舒
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Shandong University of Technology
State Grid Shanghai Electric Power Co Ltd
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Shandong University of Technology
State Grid Shanghai Electric Power Co Ltd
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    • H02J3/385—
    • 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
    • H02J3/48—Controlling the sharing of the in-phase component
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electrical Variables (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

To be simple and effective realize the voltage control to photovoltaic plant access point, the invention discloses a kind of distribution network voltage control methods adjusted based on photovoltaic DC-to-AC converter, it includes the following steps:When node voltage is out-of-limit and inverter power factor angle also be not up to capacity limit angle, into the reactive-load compensation stage of contravarianter voltage control strategy;In the case where node voltage is out-of-limit, the maximum power adjusting stage of inverter is then entered when inverter reaches maximum power but is also not up to maximum power factor angle;In the case where node voltage is out-of-limit, if inverter has reached the maximum power-factor angle, the power reduction stage of inverter is entered in the state that inverter is maintained at maximum power factor angle.The present invention obtains feeder load level and distribution situation without communicating, and can make full use of inverter capacity and carry out quick voltage adjustment, has good control effect and economy.

Description

Power distribution network voltage control method based on photovoltaic inverter regulation
Technical Field
The invention relates to the technical field of voltage control of grid connection of photovoltaic power stations, in particular to a power distribution network voltage control method based on photovoltaic inverter regulation.
Background
The access of the photovoltaic power station has great influence on the operation of the power distribution network, especially the influence on the voltage rise of the power distribution network cannot be ignored, and especially when the permeability of the photovoltaic power station is high, the situation that the voltage of the access point is overhigh easily occurs, so that the voltage of the access point is out of limit. At present, the allowable deviation of three-phase power supply voltage of 10kV and below is +/-7% of rated voltage, the situation that the node voltage of a power distribution network is too high or too low can occur due to the determinacy of external environment on photovoltaic output and the change characteristic of the all-day load requirement according to the difference of the output power direction and the output power size of the power distribution line, and the quality of the power supply voltage has great influence on the performance of electrical equipment of the power distribution network, so that the voltage control of a photovoltaic power station access point is very important, and the simple, quick and effective voltage control measures are adopted to have important significance on the stable operation of a photovoltaic power station with high permeability.
At present, the control of the voltage of a photovoltaic power station access point in documents is mostly realized by a parallel Static Var Compensator (SVC), but the SVC cannot be continuously adjusted and has the defects that when the voltage of a node is greatly reduced, the reactive power output is reduced and the like.
Therefore, it is necessary to provide a voltage control method for grid connection of photovoltaic power stations to overcome the above-mentioned drawbacks.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a power distribution network voltage control method based on photovoltaic inverter regulation, which can save equipment investment by controlling the power distribution network voltage through a photovoltaic inverter, can realize the rapid and continuous regulation of an access point by fully utilizing the capacity of the inverter, and can better realize the voltage control of the access point of a photovoltaic power station.
The technical scheme adopted for solving the technical problems is as follows:
on one hand, the method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter provided by the embodiment of the invention comprises the following steps:
when the voltage of a node (a photovoltaic power station access point) exceeds a limit and the power factor angle of the inverter does not reach a capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
if the inverter has reached the maximum power factor angle in the case where the node voltage is out of limit, the power reduction stage of the inverter is entered in a state where the inverter is maintained at the maximum power factor angle.
As a possible implementation manner of this embodiment, the process of entering the reactive compensation phase of the inverter voltage control strategy includes the following steps:
when the voltage U of the access point of the photovoltaic power stationkExceeding the limit voltage Uk,limIf the power S of the inverter does not reach the maximum, entering a reactive compensation stage of the inverter;
in the reactive compensation stage of the inverter, the reactive power Q required to be emitted by the photovoltaic inverterPV,bCalculated using the formula:
wherein, the reactance value of the path from the photovoltaic power station access point to the main transformer low-voltage bus;
by adjusting the power factor angle of the inverter to put QPV,bThe node voltage of the photovoltaic access point k is recorded as Uk,b；
According to node voltage U after reactive power compensation of inverterk,bFor the reactive power Q output by the inverterPV，bThe following correction was used:
QPV＝QPV，b+ΔQPV，b
wherein, is Δ QPV，bFor the reactive compensation phase of the inverterThe work power correction quantity is calculated according to the following formula:
as a possible implementation manner of this embodiment, the process of entering the maximum power adjustment phase of the inverter includes the following steps:
reaches its maximum capacity S at inverter power SmaxBut has not yet reached the maximum power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,lAnd transferring to the maximum power adjustment stage of the inverter;
active power P required to be generated by the photovoltaic inverter in the maximum power regulation stage of the inverterPV，tCalculated using the formula:
wherein Andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting inverter input PPV，tActive power of (b), the node voltage of the photovoltaic access point k is recorded as Uk,t；
According to the node voltage U after the maximum power adjustment stage of the inverterk,tTo active power P output by the inverterPV，tThe following correction was used:
PPV＝PPV，t+ΔPPV，t
wherein, Δ PPV，tThe calculation formula of the active power correction quantity of the maximum power regulation stage of the inverter is as follows:
as a possible implementation manner of this embodiment, the process of entering the maximum power adjustment phase of the inverter includes the following steps:
reaches a maximum value theta at an inverter power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,mAnd entering a power reduction stage of the inverter;
in the power reduction stage of the inverter, the active power P required to be emitted by the photovoltaic inverterPV，sCalculated using the formula:
wherein,andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting active power P output by inverterPV，sAnd recording the node voltage of the photovoltaic power station access point k as Uk,s；
According to the node voltage U after the power reduction stage of the inverterk,sTo active power output by the inverterPPV,sThe following correction was used:
PPV＝PPV，s+ΔPPV，s
wherein, Δ PPV，sThe calculation formula of the active power correction quantity in the maximum power regulation stage of the inverter is as follows:
in a second aspect, the method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter, provided by the embodiment of the present invention, before entering the reactive compensation phase of the inverter voltage control strategy, further includes the following steps:
and setting a target voltage limit value and an inverter capacity of the photovoltaic power station access point, and monitoring the power, the power factor angle and the node voltage of the inverter.
As a possible implementation manner of this embodiment, the process of monitoring the power, the power factor angle, and the node voltage of the inverter includes the following steps:
limiting voltage U for setting photovoltaic power station nodek,limMaximum power S of photovoltaic invertermaxAnd maximum power factor angle thetamax；
Real-time monitoring photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle θ;
calculating resistance value of path from photovoltaic power station access point to main transformer low-voltage busAnd reactance value
In a third aspect, the method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter provided by the embodiment of the present invention further includes the following steps after entering the maximum power regulation stage of the inverter:
and after the inverter voltage adjustment strategy is executed, the node voltage is continuously monitored to form closed-loop control.
As a possible implementation manner of this embodiment, the process of continuing to monitor the node voltage to form the closed-loop control includes the following steps:
after the voltage control strategy of the photovoltaic power station inverter is adjusted, the voltage of the photovoltaic power station access point is stabilized at the limit voltage Uk,lim；
Continuing to monitor photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta, forming a closed loop control.
The technical scheme of the embodiment of the invention has the following beneficial effects:
in order to simply and effectively realize the voltage control of the photovoltaic power station access point, the voltage control strategy provided by the technical scheme of the embodiment of the invention is divided into three stages according to different operation states of the inverter, and the voltage is adjusted by adjusting the active/reactive power of the photovoltaic inverter in different operation stages; the active/reactive power calculation method is only related to the voltage of the photovoltaic power station access point, the line impedance value and the inverter power factor angle, and is a linear formula, so that the calculation amount is small.
According to the technical scheme of the embodiment of the invention, the active/reactive power of the inverter is estimated and adjusted according to the out-of-limit voltage of the photovoltaic power station access point, and then the active/reactive power of the inverter is corrected according to the adjusted voltage. The method is simple and convenient to calculate, does not relate to complex mathematical calculation, does not need to acquire the load distribution condition of the power distribution network system, is high in calculation result precision, can accurately control the voltage amplitude of the photovoltaic power station access point, and has high engineering practical value.
According to the technical scheme of the embodiment of the invention, the photovoltaic inverter is used for controlling the voltage of the power distribution network, so that the equipment investment can be saved, the capacity of the inverter can be fully utilized to realize the rapid and continuous adjustment of the access point, the voltage control of the access point of the photovoltaic power station can be better realized, the load level and the distribution condition of a feeder line can be obtained without communication, the capacity of the inverter can be fully utilized to perform rapid voltage adjustment, and the photovoltaic power distribution network has good control effect and economy.
Drawings
FIG. 1 is a flow diagram illustrating a method for photovoltaic inverter regulation based voltage control of a power distribution grid in accordance with an exemplary embodiment;
FIG. 2 is a schematic diagram illustrating feeder wiring with photovoltaic power plant access in accordance with an exemplary embodiment;
fig. 3 is a comparison graph of calculation results obtained by applying the method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter, which is provided by the invention.
Detailed Description
In order to clearly explain the technical features of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. It should be noted that the components illustrated in the figures are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and procedures are omitted so as to not unnecessarily limit the invention.
Example 1
As shown in fig. 1 to fig. 3, a method for controlling a voltage of a power distribution network based on photovoltaic inverter regulation according to an embodiment of the present invention may include the following steps:
when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
if the inverter has reached the maximum power factor angle in the case where the node voltage is out of limit, the power reduction stage of the inverter is entered in a state where the inverter is maintained at the maximum power factor angle.
In one possible implementation, the process of entering the reactive compensation phase of the inverter voltage control strategy comprises the following steps:
when the voltage U of the access point of the photovoltaic power stationkExceeding the limit voltage Uk,limIf the power S of the inverter does not reach the maximum, entering a reactive compensation stage of the inverter;
in the reactive compensation stage of the inverter, the reactive power Q required to be emitted by the photovoltaic inverterPV,bCalculated using the formula:
wherein, the reactance value of the path from the photovoltaic power station access point to the main transformer low-voltage bus;
by adjusting the power factor angle of the inverter to put QPV,bThe node voltage of the photovoltaic access point k is recorded as Uk,b；
According to node voltage U after reactive power compensation of inverterk,bFor the reactive power Q output by the inverterPV，bThe following correction was used:
QPV＝QPV，b+ΔQPV，b
wherein, is Δ QPV，bThe calculation formula of the reactive power correction quantity of the reactive compensation stage of the inverter is as follows:
in one possible implementation, the process of entering the maximum power adjustment phase of the inverter includes the following steps:
reaches its maximum capacity S at inverter power SmaxBut has not yet reached the maximum power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,lAnd transferring to the maximum power adjustment stage of the inverter;
active power P required to be generated by the photovoltaic inverter in the maximum power regulation stage of the inverterPV，tCalculated using the formula:
wherein Andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting inverter input PPV，tActive power of (b), the node voltage of the photovoltaic access point k is recorded as Uk,t；
According to the node voltage U after the maximum power adjustment stage of the inverterk,tTo active power P output by the inverterPV，tThe following correction was used:
PPV＝PPV，t+ΔPPV，t
wherein, Δ PPV，tThe calculation formula of the active power correction quantity of the maximum power regulation stage of the inverter is as follows:
in one possible implementation, the process of entering the maximum power adjustment phase of the inverter includes the following steps:
reaches a maximum value theta at an inverter power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,mAnd entering a power reduction stage of the inverter;
in the power reduction stage of the inverter, the active power P required to be emitted by the photovoltaic inverterPV，sCalculated using the formula:
wherein,andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting active power P output by inverterPV，sAnd recording the node voltage of the photovoltaic power station access point k as Uk,s；
According to the node voltage U after the power reduction stage of the inverterk,sTo active power P output by the inverterPV,sThe following correction was used:
PPV＝PPV，s+ΔPPV，s
wherein, Δ PPV，sThe calculation formula of the active power correction quantity in the maximum power regulation stage of the inverter is as follows:
in order to simply and effectively realize the voltage control of the photovoltaic power station access point, the voltage control strategy provided by the embodiment is divided into three stages according to different operation states of the inverter, and the voltage is adjusted by adjusting the active/reactive power of the photovoltaic inverter in different operation stages; the active/reactive power calculation method is only related to the voltage of the photovoltaic power station access point, the line impedance value and the inverter power factor angle, and is a linear formula, so that the calculation amount is small.
Example 2
As shown in fig. 1 to fig. 3, a method for controlling a voltage of a power distribution network based on photovoltaic inverter regulation according to an embodiment of the present invention may include the following steps:
setting a target voltage limit value and an inverter capacity of a photovoltaic power station access point, and monitoring the power, a power factor angle and a node voltage of the inverter;
when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
if the inverter has reached the maximum power factor angle in the case where the node voltage is out of limit, the power reduction stage of the inverter is entered in a state where the inverter is maintained at the maximum power factor angle.
In one possible implementation, the process of monitoring the power, the power factor angle and the node voltage of the inverter includes the following steps:
limiting voltage U for setting photovoltaic power station nodek,limMaximum power S of photovoltaic invertermaxAnd maximum power factor angle thetamax；
Real-time monitoring photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle θ;
calculating resistance value of path from photovoltaic power station access point to main transformer low-voltage busAnd reactance value
The process of entering the reactive compensation phase of the inverter voltage control strategy, entering the maximum power adjustment phase of the inverter and entering the power reduction phase of the inverter is the same as in embodiment 1.
The method comprises the steps of firstly setting a target voltage limit value and an inverter capacity of a photovoltaic power station access point, monitoring power, a power factor angle and node voltage of the inverter, secondly estimating and adjusting active/reactive power of the inverter aiming at the out-of-limit voltage of the photovoltaic power station access point, and then correcting the active/reactive power of the inverter according to the adjusted voltage. The method is simple and convenient to calculate, does not relate to complex mathematical calculation, does not need to acquire the load distribution condition of the power distribution network system, is high in calculation result precision, can accurately control the voltage amplitude of the photovoltaic power station access point, and has high engineering practical value.
Example 3
As shown in fig. 1 to fig. 3, a method for controlling a voltage of a power distribution network based on photovoltaic inverter regulation according to an embodiment of the present invention may include the following steps:
when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
under the condition that the node voltage is out of limit, if the inverter reaches the maximum power factor angle, the power reduction stage of the inverter is started under the state that the inverter is kept at the maximum power factor angle;
and after the inverter voltage adjustment strategy is executed, the node voltage is continuously monitored to form closed-loop control.
In a possible implementation manner, the process of continuing to monitor the node voltage to form the closed-loop control includes the following steps:
after the voltage control strategy of the photovoltaic power station inverter is adjusted, the voltage of the photovoltaic power station access point is stabilized atLimiting voltage Uk,lim；
Continuing to monitor photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta, forming a closed loop control.
The process of entering the reactive compensation phase of the inverter voltage control strategy, entering the maximum power adjustment phase of the inverter and entering the power reduction phase of the inverter is the same as in embodiment 1.
The method comprises the steps of firstly estimating and adjusting the active/reactive power of an inverter aiming at the out-of-limit voltage of a photovoltaic power station access point, secondly correcting the active/reactive power of the inverter according to the adjusted voltage, and then continuously monitoring the voltage U of the photovoltaic power station access pointkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta, forming a closed loop control. The method is simple and convenient to calculate, does not relate to complex mathematical calculation, does not need to acquire the load distribution condition of the power distribution network system, is high in calculation result precision, can accurately control the voltage amplitude of the photovoltaic power station access point, and has high engineering practical value.
Example 4
As shown in fig. 1 to fig. 3, a method for controlling a voltage of a power distribution network based on photovoltaic inverter regulation according to an embodiment of the present invention may include the following steps:
setting a target voltage limit value and an inverter capacity of a photovoltaic power station access point, and monitoring the power, a power factor angle and a node voltage of the inverter;
when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
under the condition that the node voltage is out of limit, if the inverter reaches the maximum power factor angle, the power reduction stage of the inverter is started under the state that the inverter is kept at the maximum power factor angle;
and after the inverter voltage adjustment strategy is executed, the node voltage is continuously monitored to form closed-loop control.
In the embodiment, firstly, a target voltage limit value and an inverter capacity of a photovoltaic power station access point are set, power, a power factor angle and node voltage of the inverter are monitored, secondly, active/reactive power of the inverter is estimated and adjusted according to the out-of-limit voltage of the photovoltaic power station access point, then, the active/reactive power of the inverter is corrected according to the adjusted voltage, and finally, the voltage Uk of the photovoltaic power station access point and the voltage U of a main transformer low-voltage bus are continuously monitored0Inverter power S and power factor angle theta, forming a closed loop control. The method is simple and convenient to calculate, does not relate to complex mathematical calculation, does not need to acquire the load distribution condition of the power distribution network system, is high in calculation result precision, can accurately control the voltage amplitude of the photovoltaic power station access point, and has high engineering practical value.
In a possible implementation manner, a specific implementation process of the embodiment of the present invention includes the following steps:
step 1, setting a limit voltage U of a photovoltaic power station access pointk,limMaximum power S of photovoltaic invertermaxAnd maximum power factor angle thetamax。
Step 2, monitoring the voltage U of the access point of the photovoltaic power station in real timekAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta.
Step 3, determining a calculation path from the photovoltaic power station access point k to the main transformer low-voltage bus according to the access position of the photovoltaic power station and the specific parameters of the distribution line, and calculating the resistance from the photovoltaic power station access point to the main transformer low-voltage bus pathValue ofAnd reactance value
Step 4, when the photovoltaic power station access point voltage UkExceeding the limit voltage Uk,limAnd if the power S of the inverter does not reach the maximum value, entering a reactive compensation stage of the inverter.
Step 5, in the reactive compensation stage of the inverter, the reactive power Q required to be sent by the photovoltaic inverterPV,bCalculated using the formula
Wherein
Step 6, putting Q by adjusting the power factor angle of the inverterPV,bThe node voltage of the photovoltaic access point k is recorded as Uk,b。
Step 7, compensating the node voltage U according to the reactive power of the inverterk,bFor the reactive power Q output by the inverterPV，bAnd (5) correcting:
QPV＝QPV，b+ΔQPV，b
wherein Δ QPV，bThe method for correcting the reactive power in the reactive compensation stage of the inverter is as follows:
step 8, after the reactive power compensation stage of the inverter, when the power S of the inverter reaches the maximum capacity SmaxBut has not yet reached the maximum power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,lAnd transferring to the maximum power regulation stage of the inverter.
9, in the maximum power adjustment stage of the inverter, the active power P required to be emitted by the photovoltaic inverterPV，tCalculated using the formula:
wherein
Step 10, adjusting inverter input PPV，tActive power of (b), the node voltage of the photovoltaic access point k is recorded as Uk,t。
Step 11, adjusting the node voltage U after the stage according to the maximum power of the inverterk,tTo active power P output by the inverterPV，tAnd (5) correcting:
PPV＝PPV，t+ΔPPV，t
wherein Δ PPV，tThe calculation method of the active power correction quantity of the maximum power regulation stage of the inverter is as follows:
and step 12, in the maximum power adjustment stage of the inverter, when the power factor angle of the inverter reaches the maximum value, the voltage of the photovoltaic power station access point still exceeds the limit, the voltage of the photovoltaic power station access point is recorded as the voltage at the moment, and the power reduction stage of the inverter is switched.
Step 13, in the power reduction stage of the inverterActive power P required to be generated by photovoltaic inverterPV，sCalculated using the formula:
step 14, adjusting the active power P output by the inverterPV，sAnd recording the node voltage of the photovoltaic power station access point k as Uk,s。
Step 15, according to the node voltage U after the inverter power reduction stagek,sTo active power P output by the inverterPV,sAnd (5) correcting:
PPV＝PPV，s+ΔPPV，s
wherein Δ PPV，sThe calculation method of the active power correction quantity in the maximum power regulation stage of the inverter is as follows:
step 16, after the voltage control strategy of the photovoltaic power station inverter is adjusted, the voltage of the photovoltaic power station access point is stabilized at the limit voltage Uk,lim。
Step 17, continuing to monitor the voltage U of the access point of the photovoltaic power stationkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta, forming a closed loop control. And when the voltage exceeds the limit, the voltage control is continuously carried out through the inverter.
In order to simply and effectively realize the voltage control of the photovoltaic power station access point, the voltage control strategy provided by the embodiment is mainly divided into three stages of reactive power compensation, maximum power adjustment and power reduction according to different operation states of the inverter, and the voltage is adjusted by adjusting the active/reactive power of the photovoltaic inverter in different operation stages. In actual operation it includesThe following steps: setting a target voltage limit value and an inverter capacity of a photovoltaic power station access point, and monitoring the power, a power factor angle and a node voltage of the inverter; when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy; at node voltage UkUnder the condition of out-of-limit, when the inverter reaches the maximum power but does not reach the maximum power factor angle, entering the maximum power adjustment stage of the inverter; under the condition that the node voltage is out of limit, if the inverter reaches the maximum power factor angle, the power reduction stage of the inverter is started under the state that the inverter is kept at the maximum power factor angle; and after the inverter voltage adjustment strategy is executed, the node voltage is continuously monitored to form closed-loop control. The invention can obtain the load level and the distribution condition of the feeder line without communication, can fully utilize the capacity of the inverter to carry out rapid voltage adjustment, and has good control effect and economy.
The foregoing is only a preferred embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the invention, and such modifications and improvements are also considered to be within the scope of the invention.

Claims (8)

1. A power distribution network voltage control method based on photovoltaic inverter regulation is characterized by comprising the following steps:
when the node voltage is out of limit and the power factor angle of the inverter does not reach the capacity limit angle, entering a reactive compensation stage of an inverter voltage control strategy;
under the condition that the node voltage is out of limit, entering a maximum power regulation stage of the inverter when the inverter reaches the maximum power but does not reach a maximum power factor angle;
if the inverter has reached the maximum power factor angle in the case where the node voltage is out of limit, the power reduction stage of the inverter is entered in a state where the inverter is maintained at the maximum power factor angle.
2. The method for controlling the voltage of the power distribution network based on the photovoltaic inverter regulation, as claimed in claim 1, wherein the process of entering the reactive compensation phase of the inverter voltage control strategy comprises the following steps:
when the voltage U of the access point of the photovoltaic power stationkExceeding the limit voltage Uk,limIf the power S of the inverter does not reach the maximum, entering a reactive compensation stage of the inverter;
in the reactive compensation stage of the inverter, the reactive power Q required to be emitted by the photovoltaic inverterPV,bCalculated using the formula:
wherein, the reactance value of the path from the photovoltaic power station access point to the main transformer low-voltage bus;
by adjusting the power factor angle of the inverter to put QPV,bThe node voltage of the photovoltaic access point k is recorded as Uk,b；
According to node voltage U after reactive power compensation of inverterk,bFor the reactive power Q output by the inverterPV，bThe following correction was used:
QPV＝QPV，b+ΔQPV，b
wherein, is Δ QPV，bThe calculation formula of the reactive power correction quantity of the reactive compensation stage of the inverter is as follows:
3. the method according to claim 1, wherein the step of entering the maximum power regulation phase of the inverter comprises the steps of:
reaches its maximum capacity S at inverter power SmaxBut has not yet reached the maximum power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,lAnd transferring to the maximum power adjustment stage of the inverter;
active power P required to be generated by the photovoltaic inverter in the maximum power regulation stage of the inverterPV，tCalculated using the formula:
wherein Andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting inverter input PPV，tActive power of (b), the node voltage of the photovoltaic access point k is recorded as Uk,t；
According to the node voltage U after the maximum power adjustment stage of the inverterk,tTo active power P output by the inverterPV，tThe following correction was used:
PPV＝PPV，t+ΔPPV，t
wherein, Δ PPV，tFor maximum power regulation of invertersThe calculation formula of the active power correction quantity of the stage is as follows:
4. the method according to claim 1, wherein the step of entering the maximum power regulation phase of the inverter comprises the steps of:
reaches a maximum value theta at an inverter power factor angle thetamaxIn time, the voltage of the photovoltaic power station access point still exceeds the limit, and the voltage of the photovoltaic power station access point is recorded as Uk,mAnd entering a power reduction stage of the inverter;
in the power reduction stage of the inverter, the active power P required to be emitted by the photovoltaic inverterPV，sCalculated using the formula:
wherein,andrespectively obtaining a resistance value and a reactance value of a path from a photovoltaic power station access point to a main transformer low-voltage bus;
adjusting active power P output by inverterPV，sAnd recording the node voltage of the photovoltaic power station access point k as Uk,s；
According to the node voltage U after the power reduction stage of the inverterk,sTo active power P output by the inverterPV,sThe following correction was used:
PPV＝PPV，s+ΔPPV，s
wherein, Δ PPV，sFor active work in the maximum power regulation stage of an inverterThe rate correction amount is calculated by the following formula:
5. the method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter as claimed in any one of the claims 1 to 4, characterized by further comprising the following steps before entering the reactive compensation stage of the inverter voltage control strategy:
and setting a target voltage limit value and an inverter capacity of the photovoltaic power station access point, and monitoring the power, the power factor angle and the node voltage of the inverter.
6. The method of claim 5, wherein the monitoring of the inverter power, power factor angle and node voltage comprises the steps of:
limiting voltage U for setting photovoltaic power station nodek,limMaximum power S of photovoltaic invertermaxAnd maximum power factor angle thetamax；
Real-time monitoring photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle θ;
calculating resistance value of path from photovoltaic power station access point to main transformer low-voltage busAnd reactance value
7. The method for controlling the voltage of the power distribution network based on the regulation of the photovoltaic inverter as claimed in any one of claims 1 to 6, characterized by further comprising the following steps after entering the maximum power regulation stage of the inverter:
and after the inverter voltage adjustment strategy is executed, the node voltage is continuously monitored to form closed-loop control.
8. The method according to claim 7, wherein the step of continuing to monitor the node voltage to form the closed-loop control comprises the steps of:
after the voltage control strategy of the photovoltaic power station inverter is adjusted, the voltage of the photovoltaic power station access point is stabilized at the limit voltage Uk,lim；
Continuing to monitor photovoltaic power station access point voltage UkAnd the voltage U of the low-voltage bus of the main transformer0Inverter power S and power factor angle theta, forming a closed loop control.
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