CN105183999B - Electric system maximum short circuit current computational methods containing photovoltaic plant - Google Patents

Electric system maximum short circuit current computational methods containing photovoltaic plant Download PDF

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CN105183999B
CN105183999B CN201510592005.2A CN201510592005A CN105183999B CN 105183999 B CN105183999 B CN 105183999B CN 201510592005 A CN201510592005 A CN 201510592005A CN 105183999 B CN105183999 B CN 105183999B
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current
photovoltaic
photovoltaic plant
voltage
electric
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CN105183999A (en
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晏青
陈进
孟兴刚
王晓飞
冯小萍
南东亮
何峰
白生荣
杨媛珍
韦翔
程晓通
高明明
杨桂兴
常喜强
孙苗苗
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Guo Wang Xinjiang Power Co
State Grid Corp of China SGCC
North China Electric Power University
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Guo Wang Xinjiang Power Co
State Grid Corp of China SGCC
North China Electric Power University
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    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation

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Abstract

The invention discloses a kind of electric system maximum short circuit current computational methods containing photovoltaic plant, are related to New-energy power system adaptive setting technical field.Described method includes following steps:1)The access of photovoltaic plant is not considered, and photovoltaic electric station grid connection point voltage and trouble point three short circuit current are calculated using existing method;2)Only consider that photovoltaic electric packs hair access, and switches computation model according to photovoltaic electric station grid connection point voltage and low-voltage crossing curve acquisition situation, calculate photovoltaic plant Injection Current;3)Calculate Injection Current and branch to the electric current of trouble point, and with step 1)The current in the fault point of calculating carries out cophase stacking, obtains the total current of trouble point to get to the electric system maximum short circuit current containing photovoltaic plant.The method calculating process is simple, accurate, and protection for the electric system containing photovoltaic plant the work such as adjusts and established good basis.

Description

Electric system maximum short circuit current computational methods containing photovoltaic plant
Technical field
The present invention relates to New-energy power system adaptive setting technical field more particularly to a kind of electric power containing photovoltaic plant System maximum short circuit current computational methods.
Background technology
In recent years, with the continuous expansion of parallel network power generation scale, influence of the photovoltaic generation to power grid also begins to receive Concern, especially to the influence of electric grid relay protection.Power System Shortcuts Current calculation is to carry out relay protection setting calculation Basis, however the short circuit calculation model of photovoltaic plant is still not clear, and is ignored or will certainly caused as normal power supplies processing Large error influences relay protection fixed value setting, and then threatens the safe operation of whole system.Therefore, research photovoltaic plant event Hinder characteristic and then obtain its short circuit calculation model, and provide the Power System Shortcuts current calculation method containing photovoltaic plant there is weight Want meaning.
One of Power System Shortcuts Current calculation key containing photovoltaic plant is photovoltaic plant short circuit calculation model, however It there is no unified computation model at present.The short circuit calculation model of common photovoltaic plant mainly has following several:(1) in outer shroud PI Impedance expression under control, the lower derivation inverter frequency domain of inner ring P controls, so as to by photovoltaic DC-to-AC converter equivalence into series impedance Voltage source;(2) on the basis of (1), equivalent after photovoltaic DC-to-AC converter current inner loop amplitude limit is constant current supply;(3) current inner loop Equivalence is converted into constant current supply into constant power source (voltage controlled current source) when current limit during non-amplitude limit.These models exist There are control block diagram, parameters in practical calculating to be difficult to obtain, and the criterion of models switching is indefinite, and how Injection Current shunts or fold Add the problems such as being included in short dot.
Invention content
The technical problems to be solved by the invention are to provide a kind of electric system maximum short circuit current meter containing photovoltaic plant Calculation method, the method calculating process is simple, accurate, and protection for the electric system containing photovoltaic plant the work such as is adjusted and established Good basis.
In order to solve the above technical problems, the technical solution used in the present invention is:A kind of electric system containing photovoltaic plant Maximum short circuit current computational methods, it is characterised in that described method includes following steps:
1) access of photovoltaic plant is not considered, and photovoltaic electric station grid connection point voltage and trouble point are calculated using existing method Three short circuit current;
2) only consider that photovoltaic electric packs hair access, and according to photovoltaic electric station grid connection point voltage and low-voltage crossing curve acquisition feelings Condition switches computation model, calculates photovoltaic plant Injection Current;
3) electric current that Injection Current branches to trouble point is calculated, and the current in the fault point calculated with step 1) carries out same-phase Superposition obtains the total current of trouble point to get to the electric system maximum short circuit current containing photovoltaic plant.
Further technical solution is:The step 2) is further:Only consider the access of photovoltaic plant, and assume light Overhead utility is in full hair-like state, switches computation model according to photovoltaic electric station grid connection point voltage and low-voltage crossing curve acquisition situation, Calculate the electric current of photovoltaic plant injection.
Further technical solution is:The step 2) is specially:
(1) plants method:It does not obtain under practical low-voltage crossing curve condition, low-voltage crossing will according to as defined in Grid code Seek the electric current for calculating photovoltaic plant injection;The short circuit current that photovoltaic plant provides is calculated according to formula (1), when photovoltaic electric station grid connection point When voltage is less than 0.2pu, it is not necessary to consider short circuit current contribution;When photovoltaic electric station grid connection point voltage between 0.2pu between 1/kpu When, Injection Current kpu is calculated using constant current supply model;When photovoltaic plant site voltage is higher than 1/kpu, using constant power source Model calculates Injection Current, at this point, current value and grid entry point voltage are inversely proportional:
In formula, IpvFor photovoltaic plant Injection Current;UpccFor photovoltaic electric station grid connection point voltage;
(2) plant method:It obtains under practical low-voltage crossing curve condition, according to practical photovoltaic plant low-voltage crossing ability meter Calculate the electric current of photovoltaic plant injection;When photovoltaic plant can realize that no-voltage is passed through, computational methods are planted with (1) in the case of this Method also calculates Injection Current less than 0.2pu difference lies in grid entry point voltage by constant current supply, i.e., as shown in formula (2):
In formula, IpvFor photovoltaic plant Injection Current;UpccFor photovoltaic electric station grid connection point voltage.
Further technical solution is:The step 3) is specially:Obtain photovoltaic plant Injection Current IpvIt calculates again afterwards Branch to the electric current I of trouble pointk2, and the current in the fault point value I with being calculated in step 1)k1Cophase stacking is carried out, is obtained The total current I of trouble pointkTo get to the electric system maximum short circuit current containing photovoltaic plant, wherein Ik=Ik1+Ik2
It is using advantageous effect caused by above-mentioned technical proposal:The method calculating process is simple, accurate, to contain light The protection of the electric system of overhead utility the work such as adjusts and has established good basis.
Description of the drawings
The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
Fig. 1 is the Traditional control block diagram of photovoltaic DC-to-AC converter;
Fig. 2 is photovoltaic plant typical case's grid connected structure figure;
Fig. 3 is photovoltaic DC-to-AC converter phase voltage analogous diagram when Voltage Drop is not serious;
Fig. 4 is photovoltaic DC-to-AC converter phase current analogous diagram when Voltage Drop is not serious;
Fig. 5 is photovoltaic inverter active power, reactive power and apparent energy analogous diagram when Voltage Drop is not serious;
Fig. 6 is photovoltaic DC-to-AC converter phase voltage analogous diagram when Voltage Drop is serious;
Fig. 7 is photovoltaic DC-to-AC converter phase current analogous diagram when Voltage Drop is serious;
Fig. 8 is photovoltaic inverter active power, reactive power and apparent energy analogous diagram when Voltage Drop is serious;
Fig. 9 is the example of the Power System Shortcuts Current calculation containing photovoltaic plant;
Time transient magnetic when Figure 10 is does not consider photovoltaic plant;
Time transient magnetic when Figure 11 is only considers photovoltaic plant.
Specific embodiment
With reference to the attached drawing in the embodiment of the present invention, the technical solution in the embodiment of the present invention is carried out clear, complete Ground describes, it is clear that described embodiment is only the part of the embodiment of the present invention, instead of all the embodiments.It is based on Embodiment in the present invention, those of ordinary skill in the art are obtained every other without making creative work Embodiment shall fall within the protection scope of the present invention.
Many details are elaborated in the following description to facilitate a thorough understanding of the present invention, still the present invention can be with Implemented using other different from other manner described here, those skilled in the art can be without prejudice to intension of the present invention In the case of do similar popularization, therefore the present invention is not limited by following public specific embodiment.
The invention discloses a kind of electric system maximum short circuit current computational methods containing photovoltaic plant, concrete analysis and meter It is as follows to calculate step:
Photovoltaic DC-to-AC converter equivalence is constant current supply or the theory analysis of constant power source under Traditional control strategy:
The control structure of gird-connected inverter based on grid voltage orientation as shown in Figure 1, control system by outer voltage and Current inner loop forms.The effect of outer voltage is stable DC voltage, is controlled and realized by pi regulator.Outer voltage PI is adjusted Device output is the reference value i of current inner loop watt currentd*, so as to which the active power to inverter output is adjusted, electric current Inner ring reactive current reference value iq* it then needs to give according to power grid, as given iqWhen *=0, gird-connected inverter runs on specific work Rate only conveys active power because of number state to power grid.Photovoltaic DC-to-AC converter electric current is out-of-limit in order to prevent, in current inner loop often Clipping module is added in, amplitude is set as k times (generally taking 1.2~1.5) of rated current.
The short trouble characteristic of photovoltaic plant depends primarily on the control of inverter, when electric system generation three-phase shortcircuit is tight When weight failure but not serious grid entry point Voltage Drop, electric current is not up to current limit and thinks that the front and rear irradiation of short circuit does not become Change, therefore inverter can be controlled according to reference value active and idle before failure, i.e., power remains unchanged, therefore photovoltaic plant It can be equivalent into constant power source.Outer voltage control is destroyed when electric current reaches current limit, and current inner loop control electric current is not More than given limit value, i.e. electric current is invariable, therefore photovoltaic plant can be equivalent into constant current supply.
Photovoltaic DC-to-AC converter equivalence is constant current supply or the simulation analysis of constant power source under Traditional control strategy:
It is analyzed based on above-mentioned theory, it is grid-connected that photovoltaic plant typical case shown in Fig. 2 has been built in PowerFactory softwares Model, wherein photovoltaic plant rated power are 30MW, and original state is set as full hair, and inverter current amplitude limit is specified for 1.5 times Electric current.
(1) Fig. 3-5 is photovoltaic DC-to-AC converter phase voltage, phase current and active-power P, idle work(when Voltage Drop is not serious Rate Q and apparent energy S simulation results.Contravarianter voltage falls not seriously, and output current increases less, and active power is sent out in failure It is approximately equal to the value before failure after raw half of cycle 10ms.At this time it is considered that photovoltaic plant can be equivalent into constant power source.
(2) Fig. 6-8 is photovoltaic DC-to-AC converter phase voltage, phase current and active-power P, reactive power when Voltage Drop is serious Q and apparent energy S simulation results.Contravarianter voltage falls seriously, and output current increases increase, electric current about half week after a failure Wave 10ms is controlled substantially in 1.5 times of rated current of limit value.At this time it is considered that photovoltaic plant can be equivalent into constant current supply.
The specific implementation step of this programme is as follows:
Step 1:Do not consider that the access of photovoltaic plant carries out Three-phase Power Systems calculation of short-circuit current, using conventional method Calculate the voltage of photovoltaic electric station grid connection point and the electric current I of trouble pointk1
Step 2:Consider that only having photovoltaic plant accesses and assume that photovoltaic plant is in full hair-like state, according to Grid code The size I of regulation or practical photovoltaic plant low-voltage crossing capacity calculation photovoltaic plant Injection Currentpv
(1) lower voltage ride-through requirement calculates according to as defined in Grid code.State Grid Corporation of China company standard Q/GDW617- 2011《Photovoltaic plant access electric power network technique regulation》To the nominal of large and medium-sized photovoltaic plant requirement grid entry point Voltage Drop to 20% During voltage, photovoltaic plant can guarantee the uninterrupted 1s that is incorporated into the power networks, and photovoltaic electric station grid connection point voltage can be extensive in 3s after falling When arriving the 90% of nominal voltage again, photovoltaic plant, which can guarantee, to be uninterruptedly incorporated into the power networks, in the following photovoltaic of grid entry point voltage profile line Power station can stop to power network line power transmission.Therefore, the short circuit current that photovoltaic plant provides can be calculated according to formula (1), simultaneously When site voltage is less than 0.2pu, it is not necessary to consider short circuit current contribution;Grid entry point voltage is between 0.2pu to (electric current between 1/kpu Limit value is kpu), Injection Current kpu is calculated using constant current supply model;Grid entry point voltage is higher than 1/kpu, using constant power source mould Type calculates Injection Current, and current value and grid entry point voltage are inversely proportional.
In formula, IpvFor photovoltaic plant Injection Current;UpccFor photovoltaic electric station grid connection point voltage.
(2) according to practical photovoltaic plant low-voltage crossing capacity calculation.No-voltage can be realized by having many photovoltaic plants at present It passes through, computational methods also press constant current supply difference lies in grid entry point voltage with (1) kind method less than 0.2pu in the case Calculate Injection Current.I.e.:
Step 3:Obtain photovoltaic plant Injection Current IpvCalculate the electric current I for branching to trouble point again afterwardsk2, and and step 1 The current in the fault point I of calculatingk1Superposition, finally obtains trouble point maximum current value.
In order to better illustrate the embodiment of above three step, example shown in Fig. 9, wherein component parameters are given It is worth the value for secondary transient state, and has been included in the influence of load.It is as follows that maximum short circuit current process is calculated with this method:
Photovoltaic electric packs hair before failure, it is assumed that three-phase metallic short circuit failure occurs in f points.Figure 10 and Figure 11 is respectively not Consider and only consider the short circuit calculation equivalent circuit of photovoltaic plant access.In figure, ESFor the equivalent main power source of distribution system;ZSBased on The equiva lent impedance of power supply;ZL1For circuit L1Impedance;ZL2For circuit L2Impedance;ZLD1For load equiva lent impedance;IPVFor photovoltaic electric Stand injection electric current;ZTFor photovoltaic plant step-up transformer impedance.
When not considering photovoltaic plant access by Figure 11 calculating, electric current is at failure
Photovoltaic electric station grid connection point voltage is
The electric current I of photovoltaic plant injectionPVIt is calculated according to formula (1) or formula (2).
When calculating only consideration photovoltaic plant access by Figure 11, branching to electric current at failure is
By principle of stacking, the maximum short circuit current at failure is
Ik=Ik1+Ik2 (6)
The method calculating process is simple, accurate, and protection for the electric system containing photovoltaic plant the work such as is adjusted and established Good basis.

Claims (2)

1. a kind of electric system maximum short circuit current computational methods containing photovoltaic plant, it is characterised in that the method includes as follows Step:
1) access of photovoltaic plant is not considered, and photovoltaic electric station grid connection point voltage and trouble point three-phase are calculated using existing method Short circuit current;
2) only consider that photovoltaic electric packs hair access, and is cut according to photovoltaic electric station grid connection point voltage and low-voltage crossing curve acquisition situation Computation model is changed, calculates photovoltaic plant Injection Current;
3) electric current that Injection Current branches to trouble point is calculated, and the current in the fault point calculated with step 1) carries out same-phase and folds Add, obtain the total current of trouble point to get to the electric system maximum short circuit current containing photovoltaic plant.
2. the electric system maximum short circuit current computational methods containing photovoltaic plant as described in claim 1, it is characterised in that institute Stating step 2) is specially:
(1) plants method:It does not obtain under practical low-voltage crossing curve condition, the lower voltage ride-through requirement meter according to as defined in Grid code Calculate the electric current of photovoltaic plant injection;Photovoltaic plant Injection Current is calculated according to formula (1), when photovoltaic electric station grid connection point voltage is less than During 0.2pu, it is not necessary to consider short circuit current contribution;When photovoltaic electric station grid connection point voltage between 0.2pu between 1/kpu when, use Constant current supply model calculates Injection Current kpu;When photovoltaic plant site voltage is higher than 1/kpu, using constant power source model meter Injection Current is calculated, at this point, current value and grid entry point voltage are inversely proportional:
In formula, IpvFor photovoltaic plant Injection Current;UpccFor photovoltaic electric station grid connection point voltage;
(2) plant method:It obtains under practical low-voltage crossing curve condition, according to practical photovoltaic plant low-voltage crossing capacity calculation light The electric current of overhead utility injection;When photovoltaic plant can realize that no-voltage is passed through, computational methods plant method with (1) in the case of this Injection Current also is calculated by constant current supply less than 0.2pu difference lies in grid entry point voltage, i.e., as shown in formula (2):
In formula, IpvFor photovoltaic plant Injection Current;UpccFor photovoltaic electric station grid connection point voltage.
CN201510592005.2A 2015-09-17 2015-09-17 Electric system maximum short circuit current computational methods containing photovoltaic plant Expired - Fee Related CN105183999B (en)

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CN105048459B (en) * 2015-08-21 2017-07-07 南京工程学院 Meter and the inverse type power supply symmetrical short-circuit of low-voltage control simplify modeling method
CN106356819B (en) * 2016-09-27 2018-06-22 华北电力大学 Collect system line guard method in large-sized photovoltaic power station
CN107508322B (en) * 2017-09-22 2018-06-08 广东电网有限责任公司电力调度控制中心 A kind of short-circuit fault of power system computational methods for considering photovoltaic electric station grid connection
CN109546682B (en) * 2018-12-05 2021-07-13 广东电网有限责任公司 Photovoltaic power supply short circuit calculation method
CN110930263B (en) * 2019-11-15 2020-12-29 广东电网有限责任公司 Medium-voltage distribution network short-circuit current calculation method containing photovoltaic power supply and induction motor based on black hole particle swarm algorithm
CN112255567B (en) * 2020-10-16 2023-05-09 西安石油大学 Short-circuit current rapid determination method for power distribution network containing photovoltaic power supply

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CN104077449B (en) * 2014-07-02 2017-08-25 中国南方电网有限责任公司 A kind of inverse type DG calculation of penetration level methods based on particle cluster algorithm

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