CN111313389A - Self-adaptive pilot protection method for power distribution network containing inverter type distributed power supply - Google Patents

Self-adaptive pilot protection method for power distribution network containing inverter type distributed power supply Download PDF

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CN111313389A
CN111313389A CN202010222925.6A CN202010222925A CN111313389A CN 111313389 A CN111313389 A CN 111313389A CN 202010222925 A CN202010222925 A CN 202010222925A CN 111313389 A CN111313389 A CN 111313389A
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pcc
bus
distributed power
current
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CN111313389B (en
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李海锋
邓成江
许灿雄
王钢
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South China University of Technology SCUT
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/28—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for meshed systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices

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Abstract

The invention belongs to the field of relay protection of power systems, and relates to a self-adaptive pilot protection method for a power distribution network containing an inverter type distributed power supply, which comprises the following steps: initializing line parameters; setting the installed capacity of each distributed power supply; acquiring voltage vector and current vectors before and after a fault; setting action threshold delta I 'of fault component current differential protection'IBDG_threAnd a braking coefficient k'res(ii) a Calculating positive sequence voltage of each PCC before failure; calculating the sum of the output power of the distributed power supply; calculating the reference active power of the distributed power supply; calculating the positive sequence voltage of the fault component of each PCC to obtain the fault component output current of the distributed power supply; calculating fault component differential current delta I 'of line'dAnd braking current delta I'r(ii) a Judging delta I'dWhether or not to be simultaneously greater than k'resΔI'rAnd Δ I'IBDG_threIf yes, judging the fault in the area and starting a protection action; otherwise, no intra-zone failure is indicated. The invention is not influenced by the type of line fault, transition resistance, access capacity of the distributed power supply, access position and the like, and has strong applicability and high reliability.

Description

Self-adaptive pilot protection method for power distribution network containing inverter type distributed power supply
Technical Field
The invention belongs to the field of relay protection of power systems, and relates to a self-adaptive pilot protection method for a power distribution network containing an inverter type distributed power supply.
Background
In order to relieve the energy crisis and reduce the environmental pollution, the distributed power generation technology based on renewable energy sources such as solar energy, wind energy and the like is rapidly developed and widely applied. The permeability of distributed power supplies, especially inverter-type distributed power supplies, in the power grid is increasing. However, the access of the inverter type distributed power supply changes the structure of the traditional power distribution network, so that the single-power-supply radiation type network is converted into a multi-source network. Moreover, the output of the inverter type distributed power supply depends on the control strategy, the fault response speed is high, and the transient process can be ignored, which is greatly different from the traditional power supply. In addition, the output of the inverter type distributed power source using renewable energy also has intermittency and volatility. These factors all present significant challenges to the protection of conventional power distribution networks.
Pilot protection has also been introduced into power distribution networks containing distributed power Supplies (IBDGs) because of its good selectivity and snap-action. For a medium-voltage distribution network, a distributed power supply can be accessed into a power grid through a transformer substation, and can also be accessed into the network in a T-access mode. In actual engineering, the T-connection mode has the advantages of flexible access position, low investment cost and the like, and the T-connection mode is mainly adopted for direct grid connection of small and medium-sized distributed power supplies. However, in such a grid-connected mode, the injection current of the distributed power supply is unknown for the protection devices at two ends of the line, which makes it difficult for conventional pilot protection to take into account both the selectivity and the sensitivity. Therefore, in order to solve the problem of power distribution network protection caused by grid-connected operation of a high-permeability T-type distributed power supply, improvement needs to be carried out on the principle and strategy.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a self-adaptive pilot protection method for a power distribution network containing an inverter type distributed power supply, which aims to effectively solve the relay protection problem when a high-permeability distributed power supply is T-connected to a circuit.
A self-adaptive pilot protection method for a power distribution network containing an inverter type distributed power supply comprises the following steps:
s1, powering on the relay protection device;
s2, initializing line parameters;
s3, setting the installed capacity of each distributed power supply;
s4, respectively sampling and converting three-phase voltage and three-phase current before and after the fault of the bus M and the bus N by the relay protection devices at the bus M and the bus N to obtain positive sequence voltage vectors before the fault of the bus M and the fault of the bus N
Figure BDA0002426705710000011
And fault component voltage vectors of bus M and bus N
Figure BDA0002426705710000012
And fault component current vector
Figure BDA0002426705710000013
Simultaneously obtaining active power P flowing through a bus M and a bus NM、PN；
S5, setting operation threshold delta I 'of fault component current differential protection'IBDG_threAnd a braking coefficient k'res；
S6, deducing the positive sequence voltage of each PCC before the fault according to the positive sequence voltage vectors before the fault of the bus M and the bus N
Figure BDA0002426705710000021
S7, calculating the sum P of the output active power of the distributed power supply on the line MNout；
S8, distributing according to the ratio of the installed capacity of each distributed power supply to the total capacity of the distributed power supplies on the line MN to obtain the reference active power of each distributed power supply;
s9, respectively deducing the fault component positive sequence voltage of each PCC by the relay protection devices at the bus M and the bus N
Figure BDA0002426705710000022
Obtaining actual fault component positive sequence voltage of each PCC;
s10, calculating the estimated value of the fault component current of each distributed power supply according to the positive sequence voltage of each PCC before the fault, the reference active power of each distributed power supply and the actual fault component positive sequence voltage of each PCC
Figure BDA0002426705710000023
S11, current vector according to fault component
Figure BDA0002426705710000024
And fault component current estimates for distributed power sources
Figure BDA0002426705710000025
Calculating fault component differential current delta I 'of line'dAnd braking current delta I'r；
S12, judging fault component differential current delta I'dWhether or not to be simultaneously greater than k'resΔI'rAnd Δ I'IBDG_threIf yes, judging the fault in the area and starting a protection action; otherwise, no intra-zone fault is indicated, and the process returns to step S4.
Preferably, the operation threshold Δ I 'of the fault component current differential protection'IBDG_threAnd a braking coefficient k'resThe calculation method is as follows:
Figure BDA0002426705710000026
Figure BDA0002426705710000027
in the formula,. DELTA.Ithre＝KerKstKnpIn，KerFor transmission error of current transformers, KstIs the same type coefficient of mutual inductor, KnpIs a coefficient of a non-periodic component, InRated current flowing through the mutual inductor; kerrFor the distributed power supply fault component current maximum error coefficient,
Figure BDA0002426705710000028
rated current of the distributed power supply in a protection range; delta Iu′nbIs the unbalanced fault component current in the case of an out-of-range fault; delta l'r.min＝ΔI'IBDG_thre/kres，kresIs the braking coefficient of a conventional distribution network.
Preferably, the positive sequence voltage of each PCC before failure
Figure BDA0002426705710000029
The calculation method is as follows:
Figure BDA00024267057100000210
in the formula (I), the compound is shown in the specification,
Figure BDA00024267057100000211
the positive sequence voltage of the jth PCC when the system normally operates;
Figure BDA00024267057100000212
the positive sequence voltage vector is the positive sequence voltage vector before the fault of the bus M and the bus N; zM-NAnd ZM-jRespectively the impedance of the line MN and the impedances of the bus M to the jth PCC.
Preferably, the sum P of the output active power of the distributed power supplies on the line MNoutThe calculation method is as follows:
Figure BDA0002426705710000031
in the formula: poutThe total active power output by the distributed power supply in the line MN when the power grid operates normally is represented; pM、PNRespectively the active power flowing through the bus M and the bus N; rM-NIs the resistance of line MN.
Preferably, the reference active power P of each distributed power supplyIBDGjThe calculation method is as follows:
Figure BDA0002426705710000032
in the formula, SIBDGjIndicating the installed capacity of the jth distributed power source.
Preferably, the first and second electrodes are formed of a metal,
Figure BDA0002426705710000033
the calculation method is as follows:
Figure BDA0002426705710000034
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000035
represents the fault component positive sequence voltage of the PCC at node k derived from the bus M side; zM-jIs the impedance between bus M and the jth PCC; zM-dIs the impedance between bus M and the d-th PCC;
Figure BDA0002426705710000036
the calculated value of the distributed power supply fault component output current at the jth PCC deduced from the bus M side in the protection range,
Figure BDA0002426705710000037
the calculation method is as follows:
Figure BDA0002426705710000038
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure BDA0002426705710000039
and
Figure BDA00024267057100000310
respectively representing the positive sequence voltage of jth PCC before failure and the slave M sideThe positive sequence voltage of the jth PCC fault component during the deduced fault; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
Preferably, the first and second electrodes are formed of a metal,
Figure BDA0002426705710000041
the calculation method is as follows:
Figure BDA0002426705710000042
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000043
represents the fault component positive sequence voltage of PCC at node k derived from bus N side; zN-jIs the impedance between bus N and the jth PCC; zN-dIs the impedance between bus N and the d-th PCC;
Figure BDA0002426705710000044
the calculated value of the distributed power source fault component output current at the jth PCC derived from the N side of the bus in the protection range,
Figure BDA0002426705710000045
the calculation method is as follows:
Figure BDA0002426705710000046
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Initial phase representing common vector of PCC voltages before failure；
Figure BDA0002426705710000047
And
Figure BDA0002426705710000048
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage during the fault deduced from the N side; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
Preferably, the calculation method of the actual fault component positive sequence voltage of each PCC is:
Figure BDA0002426705710000051
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000052
a fault component positive sequence voltage actual value of a kth PCC;
Figure BDA0002426705710000053
and
Figure BDA0002426705710000054
and respectively calculating the fault component positive sequence voltage of the kth PCC derived from the side of the bus M and the bus N.
Preferably, the fault component current estimate for the distributed power source at the jth PCC
Figure BDA0002426705710000055
The calculation method is as follows:
Figure BDA0002426705710000056
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure BDA0002426705710000057
and
Figure BDA0002426705710000058
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage actual value during the fault; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the pre-fault voltage, i representing the imaginary component, and rel () representing the calculated real component.
Preferably, the fault component differential current Δ I 'of the line'dAnd braking current delta I'rThe calculation method is as follows:
Figure BDA0002426705710000059
compared with the prior art, the invention has at least the following beneficial effects:
1. the invention is not influenced by the line fault type, the transition resistance, the access capacity and the access position of the distributed power supply, and has strong applicability and high reliability.
2. The invention aims at solving the relay protection problem of the inverter type distributed power distribution network with high permeability, can effectively solve the adverse effect of the access of a plurality of inverter type distributed power supplies on the line protection, protects the inverter type distributed power supplies from the influence of the capacity, the access positions and the number of the distributed power supplies, and has strong applicability.
3. The method fully utilizes the electrical information on two sides of the line to deduce the positive sequence voltage before the fault and the positive sequence voltage of the fault component during the fault of each PCC (Point of common coupling), and further estimates the fault component output current of each distributed power supply in real time, and the estimation precision is high.
4. The method does not need iterative operation and has high calculation speed.
5. The method fully considers various practical conditions, the differential protection based on the fault components is not influenced by the system load, and the method has high sensitivity.
Drawings
Fig. 1 is a single line diagram of a power distribution network in one embodiment of the invention;
fig. 2 is a flowchart of an adaptive pilot protection method for a power distribution network including an inverter-type distributed power supply according to an embodiment of the present invention.
Detailed Description
It should be noted that, in the present application, the embodiments and features of the embodiments may be combined with each other without conflict, and the present invention is further described in detail with reference to the accompanying drawings and specific embodiments.
Examples
In this embodiment, the power distribution network shown in fig. 1 is taken as an example, where the line impedance is: 0.13+ j 0.356 Ω/km, line M-PCC1、PCC1-PCC2、PCC2-PCC3、PCC3The lengths of N are respectively: 2km, 1km, 3km and 2 km; IBDG1、IBDG2、IBDG3The capacities of the two capacitors are respectively 2MW, 1MW and 3 MW; load LD1、LD2The capacity of (A) is 8+ j0.5MVA, 2 MVA; fault point f1、f2Are respectively positioned in the IBDG2、IBDG3And the end of the bus MN.
An adaptive pilot protection method for a power distribution network with an inverter-type distributed power supply is shown in fig. 2, and comprises the following steps:
(1) powering on a relay protection device;
(2) initializing line parameters;
initializing line parameters includes: initializing rated current of distributed power supply in protection range
Figure BDA0002426705710000061
Initializing line impedance Z between distributed power sources0、Z1、…Zi、…ZnWherein Z is0Is the line impedance between bus M and the 1 st PCC; znIs the line impedance between the nth PCC and bus N; ziIs the line impedance between the ith PCC and the (i + 1) th PCC, wherein i is more than or equal to 1 and less than or equal to n-1.
In this embodiment, the rated current of the distributed power supply in the protection range is initialized
Figure BDA0002426705710000062
The line impedance between the distributed power supplies is Z0＝0.26+j*0.712Ω、Z1＝0.13+j*0.356Ω、Z2＝0.39+j*1.068Ω、Z30.26+ j 0.712 Ω, wherein Z0Is the line impedance between bus M and the first PCC; z1Is the line impedance between the 1 st PCC and the 2 nd PCC; z2Is the line impedance between the 2 nd and 3 rd PCC; z3Is the line impedance between the 3 rd PCC and bus N.
(3) Setting actual rated power capacity S of each distributed power supplyIBDG1＝2MW、SIBDG2＝1MW、SIBDG3＝3MW。
(4) The relay protection devices at the bus M and the bus N respectively sample and convert three-phase voltage and three-phase current before and after the fault of the bus M and the fault of the bus N to obtain positive sequence voltage before the fault of the bus M and the fault of the bus N
Figure BDA0002426705710000071
And fault component voltage vectors of buses M and N
Figure BDA0002426705710000072
And fault component current vector
Figure BDA0002426705710000073
Simultaneously obtaining active power P flowing through buses M and NM、PN；
(5) Setting action threshold delta I 'of fault component current differential protection'IBDG_threAnd a braking coefficient k'resComprises the following steps:
Figure BDA0002426705710000074
Figure BDA0002426705710000075
in the formula,. DELTA.Ithre＝KerKstKnpIn，KerFor transmission error of current transformers, KstIs the same type coefficient of mutual inductor, KnpIs a coefficient of a non-periodic component, InRated current flowing through the mutual inductor; kerr0.05 is the maximum error coefficient of the distributed power supply fault component current,
Figure BDA0002426705710000076
rated current of the distributed power supply in a protection range; delta Iu′nbIs the unbalanced fault component current in the case of an out-of-range fault; delta l'r.min＝ΔI'IBDG_thre/kres，kresIs the braking coefficient of a conventional distribution network. In this example,. DELTA.I 'was taken'IBDG_thre＝0.0404kA，k'res＝0.61。
(6) Calculating positive sequence voltage of each PCC before failure
Figure BDA0002426705710000077
Figure BDA0002426705710000078
In the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000079
in order for the system to operate normally,positive sequence voltage of jth PCC;
Figure BDA00024267057100000710
the positive sequence voltage at two ends of the line MN is obtained when the system normally operates; zM-NAnd ZM-jThe impedance of the line MN and the impedances of M to jth PCCs, respectively, in this embodiment: zM-N＝1.04+j*2.848Ω。
(7) Sum P of output active power of distributed power supply on bus MNoutComprises the following steps:
Figure BDA0002426705710000081
in the formula: poutThe total active power output by the distributed power supply in the line MN when the power grid operates normally is represented; pM、PNActive power flowing through two ends of the line MN respectively; rM-NIs the resistance of line MN. In this example, RM-N1.04 omega
(8) Calculating reference active power P of each distributed power supplyIBDGjComprises the following steps:
Figure BDA0002426705710000082
in the formula, SIBDGjIndicating the installed capacity of the jth distributed power source.
(9) Fault component positive sequence voltage of PCC
Figure BDA0002426705710000083
Comprises the following steps:
Figure BDA0002426705710000084
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000085
representing the positive sequence voltage, Z, of the fault component of PCC at node k derived from bus M sideM-jTo be the impedance between bus M and the jth PCC,
Figure BDA0002426705710000086
the calculated value Z of the distributed power supply fault component output current at the jth PCC deduced from the bus M side in the protection rangeM-dIs the impedance between bus M and the d-th PCC.
Distributed power source fault component output current calculated value derived from bus M side at jth PCC
Figure BDA0002426705710000087
The calculation method is as follows:
Figure BDA0002426705710000088
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure BDA0002426705710000089
and
Figure BDA00024267057100000810
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage during the fault deduced from the M side; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
Fault component positive sequence voltage of PCC
Figure BDA0002426705710000091
The calculation method is as follows:
Figure BDA0002426705710000092
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000093
representing the fault component positive sequence voltage, Z, of PCC at node k derived from the N sideN-jBeing the impedance between bus N and the jth PCC,
Figure BDA0002426705710000094
calculating value Z of distributed power supply fault component output current at jth PCC deduced from N side in protection rangeN-dIs the impedance between bus N and the d-th PCC.
Distributed power supply fault component output current calculated value derived from N side at jth PCC
Figure BDA0002426705710000095
The calculation method is as follows:
Figure BDA0002426705710000096
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure BDA0002426705710000097
and
Figure BDA0002426705710000098
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage during the fault deduced from the N side; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
(10) The calculation mode of the actual fault component positive sequence voltage of each PCC is as follows:
Figure BDA0002426705710000101
in the formula (I), the compound is shown in the specification,
Figure BDA0002426705710000102
a fault component positive sequence voltage actual value of a kth PCC;
Figure BDA0002426705710000103
and
Figure BDA0002426705710000104
and respectively calculating the fault component positive sequence voltage of the kth PCC derived from the side of the bus M and the bus N.
(11) Fault component current estimation for distributed power supplies
Figure BDA0002426705710000105
The calculation method is as follows:
Figure BDA0002426705710000106
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure BDA0002426705710000107
and
Figure BDA0002426705710000108
respectively representing the positive sequence voltage of the jth PCC before the fault and the positive sequence voltage of the jth PCC fault component during the faultAn actual value; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the pre-fault voltage, i representing the imaginary component, and rel () representing the calculated real component.
(12) Fault component differential current Δ I 'of line'dAnd braking current delta I'rThe calculation method is as follows:
Figure BDA0002426705710000109
(13) judging fault component differential current delta I'dWhether or not to be simultaneously greater than k'resΔI'rAnd Δ I'IBDG_threIf yes, judging the fault in the area and starting a protection action; otherwise, no intra-zone fault is indicated, and the step (4) is returned.
Two different fault types are listed below for illustration:
case 1: in the protective zone f1The method comprises the steps that A phase grounding short circuit fault occurs, the transition resistance is 1 omega, the effective values of three-phase voltage measured by a relay protection device at a bus M before fault are 5.740 ∠ -1.137 degrees (kV), 5.740 ∠ -121.011 degrees (kV) and 5.740 ∠ 0118.120 degrees (kV), the effective values of three-phase current measured at the bus M by the relay protection device before fault are 0.230 ∠ -9.971 degrees (kA), 0.230 ∠ -129.412 degrees (kA), 0.231 ∠ 3110.521 degrees (kA), the effective values of three-phase voltage measured at the bus N by the relay protection device before fault are 5.244 ∠ -9.974 degrees (kV), 5.244 ∠ -130.211 degrees (kV) and 5.242 ∠ 6109.936 degrees (kV), the effective values of three-phase current measured at the bus M by the relay protection device during fault are 0.420 ∠ 166.399 degrees (kA), 0.421 ∠ 45.843 degrees (kA), 0.422-73.211 degrees (kA), the effective values of three-phase voltage measured at the bus M by the relay protection device during fault are 2.553 ∠ 16.044 degrees (kV) (367 kV), 867-147.201 degrees (1.151 ∠ degrees) and the effective values of three-1.151 ∠ degrees (1.151 ∠ degrees) measured at the bus M by the relay protection device during fault are 1.151 ∠ degrees (1.151 ∠ kV), and the relay protection device during fault is 1.151 ∠ degrees (1.151 ∠ degrees) by the relayThe effective values of three-phase voltages measured at line N were 1.236 ∠ -28.561 ° (kV), 6.577 ∠ -156.325 ° (kV) and 7.799 ∠ 123.412 ° (kV), and the effective values of three-phase currents were 0.099 ∠ 147.261 ° (kA), 0.523 ∠ 19.482 ° (kA) and 0.629 ∠ -59.592 ° (kA).d＝1.282kA，k'resΔI'r0.581 kA. Due to delta I'dIs simultaneously more than k'resΔI'rAnd Δ I'IBDG_threAnd protecting the action.
Case 2: in the protective zone f2A three-phase earth short-circuit fault occurs, the transition resistance is 100 omega, the effective values of three-phase voltages measured by the pre-fault relay protection device at the bus M are-1.137 degrees (kV), (-kV), (. kV), and (kV), the effective values of three-phase currents are 0.230-1 degree (kA), 0.230-2 degrees (kA), and 0.231 degrees (kA), the effective values of three-phase voltages measured by the pre-fault relay protection device at the bus N are 4-degree (kV), 5-degree (kV), and [ (. kV), the effective values of three-phase currents are 0.420 degrees (kA), 0.421 degrees (kA), and 0.422-degree (kA), the effective values of three-phase voltages measured by the pre-fault relay protection device at the bus M are 9-1.203 degrees (kV), (. kV), the effective values of three-phase currents are 0.414 degrees (kA), the effective values of three-phase currents are 0.1-1 degree (kA), 0.270-168 degrees (kA), the effective values measured by the pre-fault protection device at the bus M, the bus N, the effective values of three-phase currents are 0.414 DEG, and the effective values measured by the pre-1.414 DEG A, the pre-0.414 DEG, the bus N, the'd＝0.0486kA，k'resΔI'r0.0225 kA. Due to delta I'dIs simultaneously more than k'resΔI'rAnd Δ I'IBDG_threAnd protecting the action.
The invention judges the fault position by adopting the mode of differential comparison of the fault component current of each end of the line, is suitable for grid-connected operation of the high-permeability distributed power supply, can reliably act under different positions, different fault types and transition resistances, and has good engineering practical value.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (10)

1. A self-adaptive pilot protection method for a power distribution network containing an inverter type distributed power supply is characterized by comprising the following steps:
s1, powering on the relay protection device;
s2, initializing line parameters;
s3, setting the installed capacity of each distributed power supply;
s4, respectively sampling and converting three-phase voltage and three-phase current before and after the fault of the bus M and the bus N by the relay protection devices at the bus M and the bus N to obtain positive sequence voltage vectors before the fault of the bus M and the fault of the bus N
Figure FDA0002426705700000011
And fault component voltage vectors of bus M and bus N
Figure FDA0002426705700000012
And fault component current vector
Figure FDA0002426705700000013
Simultaneously obtaining active power P flowing through a bus M and a bus NM、PN；
S5, setting operation threshold delta I 'of fault component current differential protection'IBDG_threAnd a braking coefficient k'res；
S6, deducing the positive sequence voltage of each PCC before the fault according to the positive sequence voltage vectors before the fault of the bus M and the bus N
Figure FDA0002426705700000014
S7, calculating lineSum P of output active power of distributed power supply on road MNout；
S8, distributing according to the ratio of the installed capacity of each distributed power supply to the total capacity of the distributed power supplies on the line MN to obtain the reference active power of each distributed power supply;
s9, respectively deducing the fault component positive sequence voltage of each PCC by the relay protection devices at the bus M and the bus N
Figure FDA0002426705700000015
Obtaining actual fault component positive sequence voltage of each PCC;
s10, calculating the estimated value of the fault component current of each distributed power supply according to the positive sequence voltage of each PCC before the fault, the reference active power of each distributed power supply and the actual fault component positive sequence voltage of each PCC
Figure FDA0002426705700000016
S11, current vector according to fault component
Figure FDA0002426705700000017
And fault component current estimates for distributed power sources
Figure FDA0002426705700000018
Calculating fault component differential current delta I 'of line'dAnd braking current delta I'r；
S12, judging fault component differential current delta I'dWhether or not to be simultaneously greater than k'resΔI'rAnd Δ I'IBDG_threIf yes, judging the fault in the area and starting a protection action; otherwise, no intra-zone fault is indicated, and the process returns to step S4.
2. The adaptive pilot protection method of claim 1, wherein an action threshold Δ l 'for fault component current differential protection'IBDG_threAnd a braking coefficient k'resThe calculation method is as follows:
Figure FDA0002426705700000019
Figure FDA0002426705700000021
in the formula,. DELTA.Ithre＝KerKstKnpIn，KerFor transmission error of current transformers, KstIs the same type coefficient of mutual inductor, KnpIs a coefficient of a non-periodic component, InRated current flowing through the mutual inductor; kerrFor the distributed power supply fault component current maximum error coefficient,
Figure FDA0002426705700000022
rated current of the distributed power supply in a protection range; delta l'unbIs the unbalanced fault component current in the case of an out-of-range fault; delta l'r.min＝ΔI'IBDG_thre/kres，kresIs the braking coefficient of a conventional distribution network.
3. The adaptive pilot protection method of claim 2, wherein the positive sequence voltage of each PCC prior to the fault
Figure FDA0002426705700000023
The calculation method is as follows:
Figure FDA0002426705700000024
in the formula (I), the compound is shown in the specification,
Figure FDA0002426705700000025
the positive sequence voltage of the jth PCC when the system normally operates;
Figure FDA0002426705700000026
the positive sequence voltage vector is the positive sequence voltage vector before the fault of the bus M and the bus N; zM-NAnd ZM-jRespectively the impedance of the line MN and the impedances of the bus M to the jth PCC.
4. The adaptive pilot protection method of claim 3, wherein the sum of the output active power P of the distributed power supplies on the line MNoutThe calculation method is as follows:
Figure FDA0002426705700000027
in the formula: poutThe total active power output by the distributed power supply in the line MN when the power grid operates normally is represented; pM、PNRespectively the active power flowing through the bus M and the bus N; rM-NIs the resistance of line MN.
5. The adaptive pilot protection method according to claim 4, wherein the reference active power P of each distributed power supplyIBDGjThe calculation method is as follows:
Figure FDA0002426705700000028
in the formula, SIBDGjIndicating the installed capacity of the jth distributed power source.
6. The adaptive pilot protection method of claim 5,
Figure FDA0002426705700000029
the calculation method is as follows:
Figure FDA00024267057000000210
in the formula (I), the compound is shown in the specification,
Figure FDA0002426705700000031
representing the positive sequence voltage of the fault component of PCC at node k derived from bus M side；ZM-jIs the impedance between bus M and the jth PCC; zM-dIs the impedance between bus M and the d-th PCC;
Figure FDA0002426705700000032
the calculated value of the distributed power supply fault component output current at the jth PCC deduced from the bus M side in the protection range,
Figure FDA0002426705700000033
the calculation method is as follows:
Figure FDA0002426705700000034
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure FDA0002426705700000035
and
Figure FDA0002426705700000036
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage during the fault deduced from the M side; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
7. The adaptive pilot protection method of claim 6,
Figure FDA0002426705700000037
the calculation method is as follows:
Figure FDA0002426705700000038
in the formula (I), the compound is shown in the specification,
Figure FDA0002426705700000039
represents the fault component positive sequence voltage of PCC at node k derived from bus N side; zN-jIs the impedance between bus N and the jth PCC; zN-dIs the impedance between bus N and the d-th PCC;
Figure FDA00024267057000000310
the calculated value of the distributed power source fault component output current at the jth PCC derived from the N side of the bus in the protection range,
Figure FDA00024267057000000311
the calculation method is as follows:
Figure FDA0002426705700000041
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; delta represents the initial phase of the PCC voltage universal vector when the system fails; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure FDA0002426705700000042
and
Figure FDA0002426705700000043
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage during the fault deduced from the N side; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support factor of LVRT in Germany, grid connectionK when the point voltage changes by less than 10%GerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the voltage before the fault, i representing the imaginary part, and rel () representing the real part of the calculation.
8. The adaptive pilot protection method of claim 7, wherein the actual fault component positive sequence voltage of each PCC is calculated by:
Figure FDA0002426705700000044
in the formula (I), the compound is shown in the specification,
Figure FDA0002426705700000045
a fault component positive sequence voltage actual value of a kth PCC;
Figure FDA0002426705700000046
and
Figure FDA0002426705700000047
and respectively calculating the fault component positive sequence voltage of the kth PCC derived from the side of the bus M and the bus N.
9. The adaptive pilot protection method of claim 8, wherein a fault component current estimate for the distributed power source at the jth PCC is
Figure FDA0002426705700000048
The calculation method is as follows:
Figure FDA0002426705700000051
in the formula,. DELTA.IdAnd Δ IqD-axis and q-axis components representing the IBDG fault component current, respectively; system of delta representationInitial phase of the general vector of the PCC voltage when the system is in fault; delta0Representing an initial phase of a common vector of PCC voltages before a fault;
Figure FDA0002426705700000052
and
Figure FDA0002426705700000053
respectively representing the jth PCC positive sequence voltage before the fault and the jth PCC fault component positive sequence voltage actual value during the fault; kmaxRepresents the maximum current coefficient; i isNRepresents the rated current of the IBDG; kGerRepresenting the voltage support coefficient of Germany LVRT, and K when the voltage change of the grid-connected point is less than 10 percentGerIs 0, more than 10% of KGerIs 2; u represents the fault positive sequence voltage amplitude, Pref＝PIBDGjRepresenting the distributed power supply reference active power, α representing the phase of the distributed power supply output current relative to the pre-fault voltage, i representing the imaginary component, and rel () representing the calculated real component.
10. The adaptive pilot protection method of claim 9, wherein a fault component differential current Δ l 'of a line'dAnd braking current delta I'rThe calculation method is as follows:
Figure FDA0002426705700000054
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