CN107370165A - A kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor - Google Patents
A kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor：Step 1, input system relevant parameter simultaneously perform the calculation below：A, topological structure and its device parameter in photovoltaic plant station are inputted, and calculates the equivalent reactance of photovoltaic plant；B, circuit model and parameter are sent out in input, and calculate submitting line reactance；C, topological structure of electric and parameter, and computing system impedance are inputted；D, the negative phase-sequence non-equilibrium among three phase voltages of single inverter are inputted；Step 2, according to the equivalent reactance of photovoltaic plant, send out line reactance and system impedance calculates the positive sequence equivalent circuit of photovoltaic plant and power network；Step 3, the negative phase-sequence equivalent circuit for calculating photovoltaic plant and power network；Step 4, the negative phase-sequence non-equilibrium among three phase voltages according to the negative phase-sequence equivalent circuit and single inverter of photovoltaic plant and power networkCalculate negative sequence voltage degree of unbalancedness at points of common connection.It is simple and practical.
Description
Technical field
The present invention relates to a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor.
Background technology
Three-phase Power Systems imbalance refers to that three-phase voltage or the three-phase current different or phase difference in amplitude are not 120 °,
Or have both at the same time.Three-phase imbalance will cause the additional heating of electric rotating machine and vibration, stray transformer flux increase and hot-spot, electricity
Net wire loss increase and a variety of protections and automatics malfunction etc..Tri-phase unbalance factor refers to that three-phase is uneven in three-phase electrical power system
The degree of weighing apparatus, typically using voltage, electric current negative phase-sequence fundametal compoment or zero sequence fundametal compoment and the root-mean-square valve of positive sequence fundametal compoment
Percentage represents.Tri-phase unbalance factor need to control within the specific limits during power system normal operation, avoid transporting power system
Row damages.Therefore, Three-phase Power Systems imbalance is the weight of new energy or user engineering planning stage electricity quality evaluation
Want one of content.
Three-phase Power Systems imbalance be due to that threephase load is asymmetric or electric network element triphase parameter asymmetry caused by.One
As for, electric network element triphase parameter is symmetrical, and the three-phase imbalance problem of power network is uneven by power consumer threephase load
Weighing apparatus causes.However, had the characteristics that in the three-phase imbalance of planning and designing stage photovoltaic plant is assessed：
1st, photovoltaic plant is by grid-connected inverters, and photovoltaic cell sends out direct current (DC), and by inverter to be reverse into three intersecting
Stream electric (AC) is sent into power network.The threephase load of inverter ac side is symmetrical, but the switch element parameter of inverter has differences,
Make its caused three-phase voltage and non-ideal three-phase sine-wave, thus produce three-phase imbalance problem, the unbalanced production of its three-phase
Life reason is different from three-phase imbalance caused by threephase load asymmetry.Therefore, three caused by conventional three characteristics of the middle term load asymmetry
Mutually uneven computational methods are not suitable for three-phase imbalance caused by photovoltaic plant and calculated.
2nd, planning and designing stage, photovoltaic plant not yet put into operation, it is impossible to obtain grid entry point or commonly connected by measuring
Three-phase electricity (the voltage, electric current) amplitude and phase of point, and then its negative sequence component can not be obtained by symmetrical component method, because
This, national standard《Quality of power supply imbalance of three-phase voltage》Three-phase imbalance described in (GB/T 15523-2008) measures and meter
Calculation method is not suitable for the uneven calculating of Three-phase Power Systems caused by photovoltaic plant.
The content of the invention
In view of the above-mentioned problems, the present invention provides a kind of calculating of photovoltaic plant access system design phase tri-phase unbalance factor
Method, propose a kind of Practical assessment side for causing power network three-phase imbalance problem suitable for planning and designing stage photovoltaic plant
Method, believable conclusion can be provided before the project implementation, three-phase imbalance can propose control measures in advance if there are problems that.
To realize above-mentioned technical purpose and the technique effect, the present invention is achieved through the following technical solutions：
A kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor, comprise the following steps：
Step 1, input system relevant parameter simultaneously perform the calculation below：
A, topological structure and its device parameter in photovoltaic plant station are inputted, and calculates the equivalent reactance of photovoltaic plant；
B, circuit model and parameter are sent out in input, and calculate submitting line reactance；
C, topological structure of electric and parameter, and computing system impedance are inputted；
D, the negative phase-sequence non-equilibrium among three phase voltages of single inverter are inputted
Step 2, according to the equivalent reactance of photovoltaic plant, send out line reactance and system impedance calculates photovoltaic plant and power network
Positive sequence equivalent circuit；
Step 3, the negative phase-sequence equivalent circuit for calculating photovoltaic plant and power network；
It is step 4, uneven according to the negative phase-sequence three-phase voltage of the negative phase-sequence equivalent circuit and single inverter of photovoltaic plant and power network
Weighing apparatus degreeCalculate negative sequence voltage degree of unbalancedness at points of common connection.
It is preferred that the equivalent reactance X of photovoltaic plantPVFor transformer equivalent reactance, the reactance of current collection equivalent line and boosting main transformer
Reactance sum.
It is preferred that if photovoltaic plant is made up of N platform identical unit transformers, each unit transformer reactance is xd, then become
The equivalent reactance of depressor is：
It is preferred that if having n generator unit on a feeder line, then the equivalent reactance x of wall scroll feeder linesFor：
In formula, XjThe reactance of connection line, S between j-th and+1 photovoltaic generation unit of jthiSent out for i-th of photovoltaic
Electric unit installed capacity,
If photovoltaic plant has m bar feeder lines, the equivalent reactance of each feed line is xs1、xs2…xsm, then photovoltaic plant collection electric line
Equivalent reactance be：
It is preferred that if photovoltaic plant is made up of a platforms boosting main transformer, if the reactance of boosting main transformer is respectively xk1、xk2…xka, then
Boosting main transformer equivalent reactance be：
It is preferred that if it is L to send out line length, every kilometer of per unit reactance is xl, then line reactance X is sent outLFor：
XL=xl·L。
It is preferred that if the three-phase ground short circuit current perunit value at points of common connection is IPCC, then system impedance XPFor：
It is preferred that if photovoltaic combining inverter AC positive sequence voltage perunit value is U1, then photovoltaic combining inverter AC
Negative sequence voltage perunit value U2For：
It is preferred that negative sequence voltage degree of unbalancedness ε at points of common connectionU2For：
In formula, UPCCFor positive sequence voltage perunit value, X at points of common connectionP2For the negative sequence neactance of power network, XL2To send out circuit
Negative sequence neactance, XPV2For photovoltaic plant negative phase-sequence equivalent reactance, and：
It is preferred that negative sequence voltage degree of unbalancedness ε at points of common connectionU2For：
The beneficial effects of the invention are as follows：
(1) data input of the present invention is topological structure and its device parameter in photovoltaic plant station, sends out line conductor model
And parameter, topological structure of electric and parameter, the performance indications of photovoltaic combining inverter.In above-mentioned data, born without three-phase
Data are carried, therefore, the present invention is applied to three-phase imbalance caused by non-threephase load asymmetry and assesses calculating.
(2) the method for the invention can utilize planning and designing stage photovoltaic plant lectotype selection conclusion, assess photovoltaic plant
In three-phase imbalance caused by points of common connection (Point of Common Coupling, hereinafter referred to as " PCC points ") after grid-connected
Degree.Therefore, the method for the invention can provide believable conclusion before the project implementation, if there are problems that, three-phase imbalance can carry
Preceding proposition control measures.
Brief description of the drawings
Fig. 1 is a kind of flow of the computational methods of photovoltaic plant access system design phase tri-phase unbalance factor of the present invention
Figure；
Fig. 2 is the equivalent model schematic diagram of photovoltaic plant of the present invention；
Fig. 3 is the connected mode schematic diagram between photovoltaic generation unit of the present invention；
Fig. 4 is the positive sequence equivalent circuit schematic diagram of photovoltaic plant and power network of the present invention；
Fig. 5 is the negative phase-sequence equivalent circuit schematic diagram of photovoltaic plant and power network of the present invention.
Embodiment
Technical solution of the present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings, so that ability
The technical staff in domain can be better understood from the present invention and can be practiced, but illustrated embodiment is not as the limit to the present invention
It is fixed.
The mesohigh power transmission network in China is three-phase three-wire system network, line voltage, line electricity under power network normal operating mode
Zero-sequence component is not present in stream, thus the degree of unbalancedness of photovoltaic plant calculates the negative phase-sequence degree of unbalancedness that can only consider voltage, electric current.
National standard《Quality of power supply imbalance of three-phase voltage》(GB/T 15523-2008) be for power system accidental conditions and
Formulate, standard defines the permissible value and its measuring method of non-equilibrium among three phase voltages.However, three-phase caused by photovoltaic plant
Imbalance is not caused by threephase load asymmetry, while is not yet put into operation in planning and designing stage engineering, it is impossible to through measuring three-phase
Its negative phase-sequence electricity is obtained by symmetrical component method after electricity, therefore existing three-phase imbalance computational methods are not suitable for photovoltaic plant
Three-phase imbalance calculates caused by after grid-connected.
A kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor, as shown in figure 1, including as follows
Step：
Step 1, input system relevant parameter simultaneously perform the calculation below：
A, topological structure and its device parameter (including photovoltaic plant unit transformer quantity and every are inputted in photovoltaic plant station
Reactance, current collection line conductor model and the parameter of individual unit transformer reactance, the quantity for the main transformer that boosts and single boosting main transformer
Deng), and calculate the equivalent reactance of photovoltaic plant.
Tens of or even hundreds inverter and unit transformer, collection electric line, boosting are included in photovoltaic plant collector system
Main transformer, its equivalent model are as shown in Figure 2.In Fig. 2, photovoltaic plant high-pressure side is grid entry point (point of
Interconnection, hereinafter referred to as " POI points ").The equivalent reactance X of photovoltaic plantPVFor transformer equivalent reactance, collection electric wire
Road equivalent reactance and boosting main transformer reactance sum.
(1) equivalent reactance of unit transformer
If photovoltaic plant is made up of N platform unit transformers, then the equivalent reactance of unit transformer is approximately considered the change of N platforms unit
Equivalent reactance after depressor parallel connection.Photovoltaic plant typically uses model parameter identical unit transformer, makes each unit transformer
Reactance is xd, then the equivalent reactance of unit transformer be：
(2) equivalent reactance of electric line is collected
On same feeder line, the connected mode between photovoltaic generation unit is as shown in figure 3, current collection equivalent line reactance one
As using the constant method of reactive loss before and after equivalent, if having n generator unit on a feeder line, then wall scroll feeder line is equivalent electric
Anti- xsFor：
In formula, XjThe reactance of connection line, S between j-th and+1 photovoltaic generation unit of jthiSent out for i-th of photovoltaic
Electric unit installed capacity,
If photovoltaic plant there are m bar feeder lines, the equivalent reactance x of each feed line is calculated respectively using above formulas1、xs2…xsm, then light
The equivalent reactance of overhead utility collection electric line is：
(3) boosting main transformer reactance
If photovoltaic plant is made up of a platforms boosting main transformer, the reactance of order boosting main transformer is respectively xk1、xk2…xka, then unit change
The equivalent reactance of depressor is：
(4) equivalent reactance of photovoltaic plant
The equivalent reactance X of photovoltaic plantPVFor equivalent transformer reactance, the reactance of current collection equivalent line and boosting main transformer reactance it
With：
XPV=Xd+Xs+Xk
B, circuit model and parameter (sending out line length, every kilometer of per unit reactance) are sent out in input, and calculate submitting line
Road reactance.
It is L that line length is sent out in order, and every kilometer of per unit reactance is xl, then line reactance X is sent outLFor：
XL=xl·L
C, topological structure of electric and electric network element parameter (all generators, transformer, line parameter circuit value in power network) are inputted, and
Computing system impedance.
In the calculating of high voltage network system impedance, resistance value is much smaller than reactance value, and engineering calculation can ignore resistance.Pass through
Thevenin's equivalence theorem is understood, is observed from PCC points to power network, negligible resistance, can is system impedance X by network equivalencePAnd electricity
Source E series circuit.By electric network composition and component parameters, PCC is calculated using power system analysis software (PSASP, BPA etc.)
Three-phase ground short circuit current I at pointPCCPerunit value, then system impedance be：
D, the negative phase-sequence non-equilibrium among three phase voltages of single inverter are inputted
According to《Photovoltaic power generation grid-connected inverter technical specification》(NB/T 32004-2013), photovoltaic combining inverter dispatches from the factory
After need to detect its performance indications.Photovoltaic combining inverter performance indications include conversion efficiency, harmonic component, imbalance
The contents such as degree, DC component.Wherein degree of unbalancedness experiment is the important performance indexes of required detection after inverter dispatches from the factory.Consult light
Overhead utility uses the factory testing of inverter to report, can obtain single inverter negative phase-sequence non-equilibrium among three phase voltages
In addition, it can be reported according to the feasibility study report of photovoltaic plant, an access system design, Electric Power Network Planning
Topological structure and device parameter in photovoltaic plant station are obtained respectively, send out circuit model and parameter, topological structure of electric and parameter.
Step 2, according to the equivalent reactance of photovoltaic plant, send out line reactance and system impedance calculates photovoltaic plant and power network
Positive sequence equivalent circuit.
Theoretical by sequence network, any group of asymmetric amount (electric current, voltage etc.) all can be analyzed to positive sequence, bear in three-phase network
Three groups of sequence, zero sequence symmetrical components, its corresponding network turn into sequence network.According to the equivalent reactance of foregoing photovoltaic system, send out line
The equivalence of road reactance and electric network impedance obtains the positive sequence equivalent circuit of photovoltaic plant and power network, as shown in Figure 4 with calculating.
Step 3, the negative phase-sequence equivalent circuit for calculating photovoltaic plant and power network.
Equivalent circuit shown in Fig. 4 is positive sequence equivalent circuit, and reactance uses perunit value.The stationary elements such as transformer, circuit
Negative sequence neactance it is identical with forward-sequence reactance, generator negative sequence impedance is approximately considered, then photovoltaic plant negative phase-sequence equal with positive sequence impedance
Equivalent reactance XPV2, send out circuit negative sequence neactance XL2, power network negative sequence neactance XP2Respectively：
The structure of negative sequence network is identical with positive sequence network, and simply generator-motor gesture is equal to zero in negative sequence network, then photovoltaic
The negative phase-sequence equivalent circuit of power station and power network is as shown in Figure 5.Three-phase imbalance source is inverter ac caused by photovoltaic plant
Side, when carrying out three-phase imbalance analysis, inverter ac side can be considered to a negative sequence voltage source.U in Fig. 52For photovoltaic
Combining inverter AC negative sequence voltage perunit value, make photovoltaic combining inverter AC positive sequence voltage perunit value U1, then U2For：
It is step 4, uneven according to the negative phase-sequence three-phase voltage of the negative phase-sequence equivalent circuit and single inverter of photovoltaic plant and power network
Weighing apparatus degreeCalculate negative sequence voltage degree of unbalancedness at PCC points.
《Quality of power supply imbalance of three-phase voltage》(GB/T 15523-2008) is provided：" it is connected to each use of points of common connection
Family causes this negative sequence voltage degree of unbalancedness permissible value to be generally 1.3%, in short-term no more than 2.6% ".Standard defines photovoltaic electric
Stand in the permissible value of negative sequence voltage degree of unbalancedness caused by PCC points.Caused according to sequence network theory and Ohm's law, photovoltaic plant
Negative sequence voltage U at PCC pointsPCC2For：
It is U to make PCC point positive sequence voltages perunit valuePCC, then photovoltaic plant negative sequence voltage degree of unbalancedness caused by the PCC points
εU2For：
I.e.：
Under power network normal operating mode, U1≈1、UPCC≈ 1, then εU2It can be reduced to：
The beneficial effects of the invention are as follows：
(1) data input of the present invention is topological structure and its device parameter in photovoltaic plant station, sends out line conductor model
And parameter, topological structure of electric and parameter, the performance indications of photovoltaic combining inverter.In above-mentioned data, born without three-phase
Data are carried, therefore, the present invention is applied to three-phase imbalance caused by non-threephase load asymmetry and assesses calculating.
(2) the method for the invention can utilize planning and designing stage photovoltaic plant lectotype selection conclusion, assess photovoltaic plant
In three-phase imbalance degree caused by PCC points after grid-connected.Therefore, the method for the invention can provide believable before the project implementation
Conclusion, if there are problems that, three-phase imbalance can propose control measures in advance.
The preferred embodiments of the present invention are these are only, are not intended to limit the scope of the invention, it is every to utilize this hair
The equivalent structure that bright specification and accompanying drawing content are made either equivalent flow conversion or to be directly or indirectly used in other related
Technical field, be included within the scope of the present invention.
Claims (10)
1. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor, it is characterised in that including as follows
Step：
Step 1, input system relevant parameter simultaneously perform the calculation below：
A, topological structure and its device parameter in photovoltaic plant station are inputted, and calculates the equivalent reactance of photovoltaic plant；
B, circuit model and parameter are sent out in input, and calculate submitting line reactance；
C, topological structure of electric and parameter, and computing system impedance are inputted；
D, the negative phase-sequence non-equilibrium among three phase voltages of single inverter are inputted
Step 2, according to the equivalent reactance of photovoltaic plant, send out line reactance and system impedance is calculating photovoltaic plant and power network just
Sequence equivalent circuit；
Step 3, the negative phase-sequence equivalent circuit for calculating photovoltaic plant and power network；
Step 4, the negative phase-sequence non-equilibrium among three phase voltages according to the negative phase-sequence equivalent circuit and single inverter of photovoltaic plant and power networkCalculate negative sequence voltage degree of unbalancedness at points of common connection.
2. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 1,
Characterized in that, the equivalent reactance X of photovoltaic plantPVFor transformer equivalent reactance, the reactance of current collection equivalent line and boosting main transformer electricity
Anti- sum.
3. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 2,
It is made up of characterized in that, setting photovoltaic plant N platform identical unit transformers, each unit transformer reactance is xd, then transformation
The equivalent reactance of device is：
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4. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 2,
Characterized in that, setting on a feeder line has n generator unit, then the equivalent reactance x of wall scroll feeder linesFor：
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In formula, XjThe reactance of connection line, S between j-th and+1 photovoltaic generation unit of jthiFor i-th of photovoltaic generation list
First installed capacity,
If photovoltaic plant has m bar feeder lines, the equivalent reactance of each feed line is xs1、xs2…xsm, then photovoltaic plant collection electric line etc.
Value reactance is：
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5. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 2,
It is made up of characterized in that, setting photovoltaic plant a platforms boosting main transformer, if the reactance of boosting main transformer is respectively xk1、xk2…xka, then rise
Pressure main transformer equivalent reactance be：
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6. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 1,
Line length is sent out as L characterized in that, setting, and every kilometer of per unit reactance is xl, then line reactance X is sent outLFor：
XL=xl·L。
7. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 1,
Characterized in that, three-phase ground short circuit current perunit value at points of common connection is set as IPCC, then system impedance XPFor：
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8. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 1,
Characterized in that, photovoltaic combining inverter AC positive sequence voltage perunit value is set as U1, then photovoltaic combining inverter AC bear
Sequence voltage perunit value U2For：
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9. a kind of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 3-8 any one
Computational methods, it is characterised in that negative sequence voltage degree of unbalancedness ε at points of common connectionU2For：
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<mi>V</mi>
<mn>2</mn>
</mrow>
</msub>
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<msub>
<mi>U</mi>
<mrow>
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<mi>C</mi>
<mi>C</mi>
</mrow>
</msub>
</mrow>
</mfrac>
<msubsup>
<mi>&epsiv;</mi>
<mrow>
<mi>U</mi>
<mn>2</mn>
</mrow>
<mn>0</mn>
</msubsup>
</mrow>
In formula, UPCCFor positive sequence voltage perunit value, X at points of common connectionP2For the negative sequence neactance of power network, XL2To send out the negative of circuit
Sequence reactance, XPV2For photovoltaic plant negative phase-sequence equivalent reactance, and：
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<mi>P</mi>
</msub>
</mrow>
</mtd>
</mtr>
</mtable>
</mfenced>
<mo>.</mo>
</mrow>
10. a kind of computational methods of photovoltaic plant access system design phase tri-phase unbalance factor according to claim 9,
Characterized in that, negative sequence voltage degree of unbalancedness ε at points of common connectionU2For：
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<mn>2</mn>
</mrow>
<mn>0</mn>
</msubsup>
<mo>.</mo>
</mrow>
2
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| CN114188958A (en) * | 2021-11-18 | 2022-03-15 | 南京大全电气研究院有限公司 | Power grid three-phase imbalance studying and judging method and system and distribution transformer terminal |
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| WO2011032265A1 (en) * | 2009-09-15 | 2011-03-24 | The University Of Western Ontario | Utilization of distributed generator inverters as statcom |
| CN103412207A (en) * | 2013-07-11 | 2013-11-27 | 华北电力大学（保定） | Photovoltaic grid connected inverter island detection method based on negative sequence current injection |
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