CN109274127A - A kind of power distribution network electrical simulation calculation method containing distributed generation resource - Google Patents

A kind of power distribution network electrical simulation calculation method containing distributed generation resource Download PDF

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CN109274127A
CN109274127A CN201811427291.7A CN201811427291A CN109274127A CN 109274127 A CN109274127 A CN 109274127A CN 201811427291 A CN201811427291 A CN 201811427291A CN 109274127 A CN109274127 A CN 109274127A
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short
circuit
distributed power
fault
current
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陈红
吕峰
邓鹏�
彭彦博
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Shanxi Jinhe Electric Power Design Co Ltd
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Shanxi Jinhe Electric Power Design Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The power distribution network electrical simulation calculation method containing distributed generation resource that the invention discloses a kind of: establishing general distributed generation resource equivalent model, including general motor-type distributed generation resource calculation of short-circuit current equivalent model and inverter type distributed generation resource calculation of short-circuit current equivalent model；Determine the general short-circuit current calculation method containing distributed power distribution network.The present invention has comprehensively considered the calculating and symmetrical and unsymmetrical short-circuit calculating of motor-type and inverter type distributed generation resource, can enhance calculation of short-circuit current to the adaptability of distributed generation resource and be applied to software development, versatile.

Description

Electrical simulation calculation method for power distribution network with distributed power supply
Technical Field
The invention relates to a power distribution network electrical simulation calculation method, in particular to a power distribution network electrical simulation calculation method with distributed power supplies.
Background
The access of the distributed power supply changes the power supply structure of the traditional power distribution network, and the power distribution network does not have only one power supply to supply power to the load. Because the short-circuit current characteristics of the distributed power supply are different from those of the system power supply, the applicability of the traditional short-circuit current calculation method for the power distribution network with the distributed power supply needs to be further analyzed. If the distributed power sources in the power distribution network are directly equivalent to voltage sources, the calculation can be carried out by adopting a traditional short-circuit current calculation method. However, in an actual power distribution network, the types of distributed power sources are more, and the voltage source equivalent model may not be suitable for all distributed power sources any more along with the difference of the types of the distributed power sources, and at this time, the traditional calculation method is difficult to apply and needs to be improved. At present, the researched short-circuit current calculation method for a power distribution network with distributed power supplies is not strong in universality, and only the calculation of the distributed power supplies of a motor type or a converter type is considered; or asymmetric calculation is not considered, only a method for symmetric short circuit calculation is simply proposed, and the method is only suitable for mathematical calculation and cannot be applied to general calculation software development. Therefore, it is necessary to study a method for calculating the short circuit of the power distribution network including the distributed power sources.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for calculating the electrical simulation of a power distribution network with a distributed power supply.
The purpose of the invention is realized by the following technical scheme.
The invention discloses an electrical simulation calculation method for a power distribution network with a distributed power supply, which comprises the following steps:
the first step is as follows: and establishing a universal distributed power supply equivalent model, which comprises a universal motor type distributed power supply short-circuit current calculation equivalent model and an inverter type distributed power supply short-circuit current calculation equivalent model. The specific process is as follows:
on the basis of classifying the distributed power supplies, analyzing short-circuit current characteristics of the motor type distributed power supplies and the converter type distributed power supplies in different control modes to obtain a motor type distributed power supply short-circuit full current expression and a converter type distributed power supply short-circuit full current expression, providing a basis for equivalent analysis of the distributed power supplies in short-circuit current calculation, and obtaining a universal motor type distributed power supply short-circuit current calculation equivalent circuit and a converter type distributed power supply short-circuit current calculation equivalent circuit;
the second step is that: calculation method for determining short-circuit current of universal power distribution network with distributed power supply
Deducing a short-circuit current calculation method of the distribution network containing the distributed power supply under the symmetric fault according to a symmetric short-circuit current calculation method of the distribution network, a node impedance voltage equation and a universal distributed power supply equivalent model; and deducing a short-circuit current calculation method of the power distribution network containing the distributed power supply under the asymmetric fault according to the asymmetric fault of the power distribution network without the distributed power supply.
In the first step, a short-circuit full current expression of the motor type distributed power supply is as follows:
wherein, UNRated phase voltage for the generator; x's' is the generator sub-transient reactance; t issAnd TτThe time constant is the sub-transient time constant of the stator and the rotor of the generator, sigma is the total leakage reactance coefficient of the generator, α is the electronic voltage phase angle of the generator in short circuit;
in the first step, an inverter type distributed power supply short-circuit full current expression is as follows:
(a) short-circuit current of the inverter type distributed power supply under the vector decoupling control strategy:
wherein, Isc.maxIs the maximum steady state short circuit current; i issc.limIs the steady state short circuit current after limiting; t isDG.CThe response time of the distributed power supply control system is shown, and tau is a time constant of the short circuit loop;
(b) under the current instantaneous value control strategy, short-circuit current of a converter type distributed power supply:
in the second step, a short-circuit current calculation method of the power distribution network containing the distributed power supply under the fault is called, and the specific process is as follows:
converting a system power supply and a motor type distributed power supply into equivalent current sources, wherein the converter type distributed power supply is equivalent to the current sources; when a node k of the power distribution network with the distributed power supply fails, a node voltage equation is listed according to a universal port network of the power distribution network:
U＝ZI
wherein U is the voltage of each node, I is the current of each node, Z is the node impedance matrix of the power grid, and n is the number of nodes of the power grid;
according to the superposition theorem, the voltage U of each node of the power distribution network after the fault is expressed as follows:
U＝U0+ΔU
wherein, U0The voltage is a normal component of the node voltage of the power distribution network, and the delta U is a fault component of the node voltage of the power distribution network;
U0＝ZISC
wherein, ISCFor the node current to be in normal operation,to switch in the short circuit current of the distributed power supply for node k,is the normal component of the voltage at node k;
ΔU＝ZkkIk
wherein,for short-circuit point current, ZkkIs the equivalent resistance at the point of failure,is the fault component of the voltage at node k;
for fault voltage at short circuit point:
wherein Z iskIs a ground resistor;
the short-circuit point current is obtained by the following steps:
the calculation method of the voltage of the rest points and the current of each branch circuit is the same as the calculation method without the distributed power supply.
In the second step, a short-circuit current calculation method of a power distribution network containing a distributed power supply under the asymmetric fault comprises the following specific processes: firstly, all power supplies are equivalent to current sources according to a symmetrical fault calculation method; secondly, after a three-phase asymmetric fault occurs at the point k, the voltage and the current are asymmetric, and a symmetric component method is applied to decompose the asymmetric vector at the point k into three groups of symmetric vectors, namely a positive sequence component, a negative sequence component and a zero sequence component; at this time, the network is represented by the superposition of three sequential networks;
according to the superposition theorem, each sequence voltage of the power distribution network containing the distributed power supply is decomposed into a normal component and a fault component:
wherein, U(1)、U(2)、U(3)Respectively positive sequence, negative sequence and zero sequence components of each node voltage; respectively positive sequence, negative sequence and zero sequence components of the normal components of the voltage of each node; delta U(1)、ΔU(2)、ΔU(0)Respectively positive sequence, negative sequence and zero sequence components of voltage fault components of each node;
the following equation is established for the normal component:
because the power in the distribution network only has the positive sequence component when normal operation, consequently each node voltage of distribution network only contains the positive sequence component, promptly:
wherein,
the following equation is established for the fault component:
wherein:
the current fault components of the positive sequence component network, the negative sequence component network and the zero sequence component network are respectively; z(1)、Z(2)、Z(0)Respectively representing impedance matrix column vectors of all sequence nodes related to the short circuit point;
obtaining the following components:
U(2)＝0+Z(2)I(2)
U(0)＝0+Z(0)I(0)
wherein
At the moment, 3n equations are shared, but the unknown variables comprise n positive-sequence, negative-sequence and zero-sequence voltages and three-sequence fault currents of fault points, and the ratio of the equations is increased by 3 unknowns; in addition, when solving the short-circuit current, the three-sequence current under different short-circuit faults under different short-circuit situations should be considered as follows:
(a) single phase earth fault
When a single-phase earth fault occurs, taking the phase A as a reference phase, regarding the k three-phase voltage and current of a fault point, the boundary conditions of the single-phase earth fault are as follows:
wherein,the a-phase voltage at the point k,respectively corresponding phase A, phase B and phase C currents at k points;
converting the above equation into symmetric components, yielding:
and then obtaining the three-sequence current at the fault as follows:
(b) two-phase short circuit fault
In the case of a two-phase short-circuit fault, a two-phase short-circuit occurs at the fault point k (B, C phase) with the a phase as the reference phase, and the following boundary conditions are satisfied at the time of the two-phase short-circuit fault with respect to the three-phase voltage and current:
wherein,b phase voltage and C phase voltage at a k point;
they are converted to a symmetric component representation using a symmetric component method:
three-sequence current component at fault:
(c) short circuit between two opposite grounds
In the case of a short-circuit fault between the two phases, two phases (B, C phases) are short-circuited and grounded at point k with the normal phase a as a reference phase, and the boundary conditions are as follows:
converted into a symmetrical component in the form of
Obtaining three-sequence current components at the fault:
compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) the invention provides a general short-circuit current calculation equivalent circuit of a motor type distributed power supply and a converter type distributed power supply, and solves the problem that a voltage source equivalent model is not suitable for various distributed power supplies.
(2) The invention provides a general short-circuit current calculation method for a power distribution network with a distributed power supply, and solves the problem that only symmetrical or asymmetrical short-circuit calculation and a calculation method cannot be used for developing general computer software in the prior art.
Drawings
FIG. 1 is a general electromechanical distributed power equivalent circuit model;
FIG. 2 is a general converter type distributed power equivalent circuit model;
FIG. 3 is a generalized representation of a symmetrical fault equivalent circuit for a power distribution network including distributed power sources;
FIG. 4 is a general representation of a three-phase asymmetric fault with a distributed power distribution network;
fig. 5 is a flow chart of short circuit current calculation of a power distribution network including distributed power sources.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention discloses an electrical simulation calculation method for a power distribution network containing distributed power supplies, which fully considers the influence of the access of the distributed power supplies on short-circuit current for the power distribution network containing the distributed power supplies and obtains a universal equivalent model of the distributed power supplies by analyzing the short-circuit characteristics of a motor type and a converter type distributed power supplies; all power supplies are characterized as current sources, a network impedance matrix is adopted to describe the network structure of the power distribution network, and the symmetrical and asymmetrical fault short-circuit currents of the power distribution network are calculated by using an superposition method, so that the universal short-circuit current calculation method of the power distribution network containing the distributed power supplies is obtained. The method standardizes the short circuit calculation process, is suitable for short circuit calculation of various distributed power supplies and is very suitable for software development, and the calculation universality is realized. The method provides reference for the problems that the traditional relay protection setting method is not suitable for use due to the fact that a large number of distributed power supplies are connected, and the original electrical equipment cannot stably run when being connected to the distributed power supply distribution network, and has great practical value.
The invention discloses an electrical simulation calculation method for a power distribution network containing a distributed power supply, which comprises the following concrete implementation processes:
the first step is as follows: and establishing a universal distributed power supply equivalent model, which comprises a universal motor type distributed power supply short-circuit current calculation equivalent model and an inverter type distributed power supply short-circuit current calculation equivalent model.
The specific process is as follows: on the basis of classifying the distributed power supplies, short-circuit current characteristics of the motor type distributed power supplies and the converter type distributed power supplies in different control modes are analyzed to obtain a motor type distributed power supply short-circuit full current expression and a converter type distributed power supply short-circuit full current expression, a basis is provided for equivalent analysis of the distributed power supplies in short-circuit current calculation, and a universal motor type distributed power supply short-circuit current calculation equivalent circuit and a converter type distributed power supply short-circuit current calculation equivalent circuit are obtained, as shown in fig. 1 and fig. 2.
(a) Short-circuit full current expression of motor type distributed power supply
Wherein, UNRated phase voltage for the generator; x's' is the generator sub-transient reactance; t issAnd TτThe time constant of the sub-transient state of the stator and the rotor of the generator, the total leakage reactance coefficient of the generator, and the electronic voltage phase angle of the generator in the short circuit are α.
(b) Converter type distributed power supply short-circuit full current expression
Short-circuit current of the inverter type distributed power supply under the vector decoupling control strategy:
wherein, Isc.maxIs the maximum steady state short circuit current; i issc.limIs the steady state short circuit current after limiting; t isDG.CAnd tau is the time constant of the short circuit loop, and is the response time of the distributed power control system.
Under the current instantaneous value control strategy, short-circuit current of a converter type distributed power supply:
the second step is that: calculation method for determining short-circuit current of universal power distribution network with distributed power supply
And deducing a short-circuit current calculation method of the power distribution network containing the distributed power supply under the symmetric fault according to the symmetric short-circuit current calculation method of the power distribution network, a node impedance voltage equation and a universal distributed power supply equivalent model. And deducing a short-circuit current calculation method of the power distribution network containing the distributed power supply under the asymmetric fault according to the asymmetric fault of the power distribution network without the distributed power supply.
The method for calculating the short-circuit current of the power distribution network with the distributed power supply under the symmetrical fault comprises the following specific processes:
the motor type distributed power supply obtained from the first step can be equivalent to a voltage source, and the converter type distributed power supply can be equivalent to a current source. For convenient calculation, a system power supply and a motor type distributed power supply are converted into equivalent current sources.
When a node k of the power distribution network containing the distributed power supply fails, the universal port network of the power distribution network is shown in fig. 3. WhereinIs the equivalent current of the system power supply,is the equivalent current of the distributed power supply,in order to be able to short-circuit the fault voltage,is the short circuit point current.
The node voltage equation is listed according to FIG. 3, where ZkIs a ground resistor.
U＝ZI (4)
Wherein, U is each node voltage, I is each node current, Z is the node impedance matrix of the power grid, and n is the node number of the power grid.
According to the superposition theorem, the voltage U of each node of the power distribution network after the fault can be expressed as follows:
U＝U0+ΔU (8)
wherein, U0The voltage of the node of the power distribution network is a normal component, and the delta U is a fault component of the voltage of the node of the power distribution network.
For the normal component of the voltage, the normal component can be obtained according to load flow calculation, and for a network containing the distributed power supply, the normal component must be calculated according to an equivalent circuit.
At this time, the normal component of the node voltage is:
U0＝ZISC(9)
wherein, ISCFor the node current to be in normal operation,to switch in the short circuit current of the distributed power supply for node k,the normal component of the voltage at node k.
The node voltage equation for the fault component is:
ΔU＝ZkkIk(12)
wherein,for short-circuit point current, ZkkIs the equivalent resistance at the point of failure,the normal component of the voltage at node k.
For fault voltages at short-circuit points, there are:
at the same time, the user can select the desired position,
the short-circuit point current is obtained by the following steps:
the calculation method of the voltage of the rest points and the current of each branch circuit is the same as the calculation method without the distributed power supply.
The method for calculating the short-circuit current of the power distribution network with the distributed power supply under the asymmetric fault comprises the following specific processes:
for a power distribution network with distributed power supplies, after a three-phase asymmetric fault occurs at a node k in the network, the node k is represented by a universal port network, as shown in fig. 4. WhereinRespectively are phase A, phase B and phase C voltages at a point k,are respectively a pairAnd the corresponding k points are the phase A, the phase B and the phase C.
Firstly, all power supplies are equivalent to current sources according to a symmetrical fault calculation method. Secondly, after a three-phase asymmetric fault occurs at the point k, the voltage and the current are asymmetric, and a symmetric component method is applied to decompose the asymmetric vector at the point k into three groups of symmetric vectors, namely a positive sequence component, a negative sequence component and a zero sequence component. At this time, the network is represented by the superposition of three sequential networks;
according to the superposition theorem, each sequence voltage of the power distribution network containing the distributed power supply can be decomposed into a normal component and a fault component:
wherein, U(1)、U(2)、U(3)Respectively positive sequence, negative sequence and zero sequence components of each node voltage; respectively positive sequence, negative sequence and zero sequence components of the normal components of the voltage of each node; delta U(1)、ΔU(2)、ΔU(0)Respectively positive sequence, negative sequence and zero sequence components of the voltage fault components of each node.
The following equation is established for the normal component:
because the power in the distribution network only has the positive sequence component when normal operation, consequently each node voltage of distribution network only contains the positive sequence component, promptly:
wherein,
the following equation is established for the fault component:
wherein:
the current fault components of the positive sequence component network, the negative sequence component network and the zero sequence component network are respectively; z(1)、Z(2)、Z(0)Respectively, the impedance matrix column vector of each sequence node related to the short circuit point.
By substituting formulae (19), (20) and (21) for formula (18):
wherein
Equation (22) has 3n equations in total. But the unknown variables comprise n positive sequence, negative sequence, zero sequence voltages and three sequence fault currents of a fault point, and the ratio is 3 more unknown variables. In addition, when solving for the short-circuit current, the three-sequence current under different short-circuit faults for different short-circuit situations should be considered as follows, as shown in fig. 5:
(a) single phase earth fault
When a single-phase earth fault occurs, taking the phase A as a reference phase, regarding the k three-phase voltage and current of a fault point, the boundary conditions of the single-phase earth fault are as follows:
converting equation (23) into a symmetric component, one can obtain:
and (3) combining the formula (24) with the formula (22) to obtain the three-sequence current at the fault position as follows:
(b) two-phase short circuit fault
In the case of a two-phase short circuit fault, the a phase is used as the reference phase. A two-phase short circuit (B, C phases) occurs at the fault point k, and the two-phase short circuit fault has the following boundary conditions in terms of three-phase voltage and current:
they are converted to a symmetric component representation using a symmetric component method:
and (2) combining the equation (27) and the equation (22) to obtain three-sequence current components at the fault:
(c) short circuit between two opposite grounds
In the case of short-circuit failure of both the phases, the normal phase A is used as a reference phase. Two phases (B, C phases) are shorted to ground at point k. The boundary conditions are as follows:
converted into a symmetrical component in the form of
And (3) combining the equation (30) and the equation (22) to obtain three-sequence current components at the fault:
while the present invention has been described in terms of its functions and operations with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise functions and operations described above, and that the above-described embodiments are illustrative rather than restrictive, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined by the appended claims.

Claims (4)

1. A power distribution network electrical simulation calculation method containing a distributed power supply is characterized by comprising the following steps:
the first step is as follows: establishing a universal distributed power supply equivalent model, which comprises a universal motor type distributed power supply short-circuit current calculation equivalent model and an inverter type distributed power supply short-circuit current calculation equivalent model; the specific process is as follows:
on the basis of classifying the distributed power supplies, analyzing short-circuit current characteristics of the motor type distributed power supplies and the converter type distributed power supplies in different control modes to obtain a motor type distributed power supply short-circuit full current expression and a converter type distributed power supply short-circuit full current expression, providing a basis for equivalent analysis of the distributed power supplies in short-circuit current calculation, and obtaining a universal motor type distributed power supply short-circuit current calculation equivalent circuit and a converter type distributed power supply short-circuit current calculation equivalent circuit;
the second step is that: calculation method for determining short-circuit current of universal power distribution network with distributed power supply
Deducing a short-circuit current calculation method of the distribution network containing the distributed power supply under the symmetric fault according to a symmetric short-circuit current calculation method of the distribution network, a node impedance voltage equation and a universal distributed power supply equivalent model; and deducing a short-circuit current calculation method of the power distribution network containing the distributed power supply under the asymmetric fault according to the asymmetric fault of the power distribution network without the distributed power supply.
2. The electrical simulation calculation method for the power distribution network with the distributed power supplies according to claim 1, wherein in the first step, the short-circuit full current expression of the motor type distributed power supply is as follows:
wherein, UNRated phase voltage for the generator; x'sIs a generator sub-transient reactance; t issAnd TτThe time constant is the sub-transient time constant of the stator and the rotor of the generator, sigma is the total leakage reactance coefficient of the generator, α is the electronic voltage phase angle of the generator in short circuit;
in the first step, an inverter type distributed power supply short-circuit full current expression is as follows:
(a) short-circuit current of the inverter type distributed power supply under the vector decoupling control strategy:
wherein, Isc.maxIs the maximum steady state short circuit current; i issc.limIs the steady state short circuit current after limiting; t isDG.CThe response time of the distributed power supply control system is shown, and tau is a time constant of the short circuit loop;
(b) under the current instantaneous value control strategy, short-circuit current of a converter type distributed power supply:
3. the electrical simulation calculation method for the power distribution network with the distributed power supplies according to claim 1, wherein in the second step, the calculation method for the short-circuit current of the power distribution network with the distributed power supplies under the fault is called, and the specific process is as follows:
converting a system power supply and a motor type distributed power supply into equivalent current sources, wherein the converter type distributed power supply is equivalent to the current sources; when a node k of the power distribution network with the distributed power supply fails, a node voltage equation is listed according to a universal port network of the power distribution network:
U＝ZI
wherein U is the voltage of each node, I is the current of each node, Z is the node impedance matrix of the power grid, and n is the number of nodes of the power grid;
according to the superposition theorem, the voltage U of each node of the power distribution network after the fault is expressed as follows:
U＝U0+ΔU
wherein, U0The voltage is a normal component of the node voltage of the power distribution network, and the delta U is a fault component of the node voltage of the power distribution network;
U0＝ZISC
wherein, ISCFor the node current to be in normal operation,to switch in the short circuit current of the distributed power supply for node k,is the normal component of the voltage at node k;
ΔU＝ZkkIk
wherein,for short-circuit point current, ZkkIs the equivalent resistance at the point of failure,is the fault component of the voltage at node k; for fault voltage at short circuit point:
wherein Z iskIs a ground resistor;
the short-circuit point current is obtained by the following steps:
the calculation method of the voltage of the rest points and the current of each branch circuit is the same as the calculation method without the distributed power supply.
4. The electrical simulation calculation method for the power distribution network with the distributed power supply according to claim 1, wherein in the second step, the short-circuit current calculation method for the power distribution network with the distributed power supply under the asymmetric fault comprises the following specific processes: firstly, all power supplies are equivalent to current sources according to a symmetrical fault calculation method; secondly, after a three-phase asymmetric fault occurs at the point k, the voltage and the current are asymmetric, and a symmetric component method is applied to decompose the asymmetric vector at the point k into three groups of symmetric vectors, namely a positive sequence component, a negative sequence component and a zero sequence component; at this time, the network is represented by the superposition of three sequential networks;
according to the superposition theorem, each sequence voltage of the power distribution network containing the distributed power supply is decomposed into a normal component and a fault component:
wherein, U(1)、U(2)、U(3)Respectively positive sequence, negative sequence and zero sequence components of each node voltage; respectively positive sequence, negative sequence and zero sequence components of the normal components of the voltage of each node; delta U(1)、ΔU(2)、ΔU(0)Respectively positive sequence, negative sequence and zero sequence components of voltage fault components of each node;
the following equation is established for the normal component:
because the power in the distribution network only has the positive sequence component when normal operation, consequently each node voltage of distribution network only contains the positive sequence component, promptly:
wherein,
the following equation is established for the fault component:
wherein:
the current fault components of the positive sequence component network, the negative sequence component network and the zero sequence component network are respectively; z(1)、Z(2)、Z(0)Respectively representing impedance matrix column vectors of all sequence nodes related to the short circuit point;
obtaining the following components:
U(1)＝U0 (1)+Z(1)I(1)
U(2)＝0+Z(2)I(2)
U(0)＝0+Z(0)I(0)
wherein
At the moment, 3n equations are shared, but the unknown variables comprise n positive-sequence, negative-sequence and zero-sequence voltages and three-sequence fault currents of fault points, and the ratio of the equations is increased by 3 unknowns; in addition, when solving the short-circuit current, the three-sequence current under different short-circuit faults under different short-circuit situations should be considered as follows:
(a) single phase earth fault
When a single-phase earth fault occurs, taking the phase A as a reference phase, regarding the k three-phase voltage and current of a fault point, the boundary conditions of the single-phase earth fault are as follows:
wherein,the a-phase voltage at the point k,respectively corresponding phase A, phase B and phase C currents at k points;
converting the above equation into symmetric components, yielding:
and then obtaining the three-sequence current at the fault as follows:
(b) two-phase short circuit fault
In the case of a two-phase short-circuit fault, a two-phase short-circuit occurs at the fault point k (B, C phase) with the a phase as the reference phase, and the following boundary conditions are satisfied at the time of the two-phase short-circuit fault with respect to the three-phase voltage and current:
wherein,b phase voltage and C phase voltage at a k point;
they are converted to a symmetric component representation using a symmetric component method:
three-sequence current component at fault:
(c) short circuit between two opposite grounds
In the case of a short-circuit fault between the two phases, two phases (B, C phases) are short-circuited and grounded at point k with the normal phase a as a reference phase, and the boundary conditions are as follows:
converted into a symmetrical component in the form of
Obtaining three-sequence current components at the fault:
CN201811427291.7A 2018-11-27 2018-11-27 A kind of power distribution network electrical simulation calculation method containing distributed generation resource Pending CN109274127A (en)

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Cited By (2)

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Publication number Priority date Publication date Assignee Title
CN110456223A (en) * 2019-08-19 2019-11-15 西南交通大学 A kind of power distribution network short circuit current measuring method containing distributed generation resource and electric car
CN114188944A (en) * 2022-02-15 2022-03-15 国网江西省电力有限公司电力科学研究院 Method and device for calculating short-circuit current of power grid with distributed power supply

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