CN105119255A - Photovoltaic microgrid fault isolation method based on fault state - Google Patents
Photovoltaic microgrid fault isolation method based on fault state Download PDFInfo
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Abstract
For the single-phase grounding fault and instant fault of a power distribution network including a photovoltaic microgrid, the invention discloses a photovoltaic microgrid fault isolation method based on a fault state. The method includes the following steps of (1) partitioning the microgrid; (2) isolating the fault sections; (3) cutting off a single-phase grounding fault wire; and (4) recovering the power supply of fault microgrid partitions. The microgrid is reasonably partitioned, the fault sections are isolated through a boundary switch, and the power-off range is reduced. By the full use of the anti-islanding protection function of a photovoltaic inverter, a fault line is selected through S transform after the photovoltaic power supply and the power grid are isolated, so that the reliability of relay protection and the accuracy of line selection are improved, and the problem that the power distribution network including the photovoltaic power supply is unreliable in relay protection due to the bidirectional flow of power is solved. The photovoltaic microgrid fault isolation method has better protection effects on the single-phase grounding fault and other instant faults in the power distribution network.
Description
Technical field
The present invention relates to a kind of distribution network failure processing method, specifically a kind of photovoltaic micro failure separation method based on fault case, belongs to technical field of new energy power generation.
Background technology
Along with modern electric user to power supply continuity and reliability requirement improve constantly and power supply enterprise to the pay attention to day by day of user satisfaction, how after power distribution network breaks down, analyzing failure cause, select fault feeder, isolated fault platform district fast recovery of power supply become and become more and more important.On the other hand; along with industrial expansion; a large amount of nonlinear-load is as access electrical networks such as rectifying device, arc furnace, converter plants; photovoltaic, wind-force distributed Blast Furnace Top Gas Recovery Turbine Unit (TRT) access distribution side; the access of Novel load and Blast Furnace Top Gas Recovery Turbine Unit (TRT) will change the structure of power distribution network; further, the flowing of the unidirectional power of original power distribution network is become bi-directional power flow, and this is by more complicated for the protection and failure diagnosis causing power distribution network.Therefore, how for distributed power source fault post analysis, how to take suitable relay protecting method, and the partition method of distributed power source under fault case, so that the power supply of fast quick-recovery power distribution network, more and more become the focus of concern.
Photovoltaic, wind-force distributed Blast Furnace Top Gas Recovery Turbine Unit (TRT) access distribution side changes the structure of power distribution network, and the flowing of the unidirectional power of original power distribution network is become bi-directional power flow, and this is by more complicated for the protection and failure diagnosis causing power distribution network.The fault of the power distribution network of access distributed power source can not be located and eliminate by traditional relay protecting method fast, and this scope that can cause power failure is excessive, is difficult to the place determining to break down.When there is unplanned isolated island there is the risk continuing to be incorporated into the power networks in distributed power inverter, and this causes a hidden trouble for the overhaul of the equipments under Distribution Network Failure state.
In low and medium voltage distribution network, the fault of more than 80% is single phase ground fault, different from the heavy current grounding system of power transmission network, the neutral point of power distribution network is usually earth-free, or by arc suppression coil and high resistance grounding, be small current neutral grounding system, when there is single phase ground fault, due to can not short-circuit loop be formed, although now line voltage keeps normal, still can be customer power supply more than one hour, but the phase voltage do not broken down be by rising 1.732 times, the insulation property of serious threat system.When having accessed photo-voltaic power supply in power distribution network or having contained by the micro-capacitance sensor of photo-voltaic power supply, energy storage device and load structure, during power distribution network generation earth fault, not only need accurately to isolate fault wire, isolated fault section, and, should the power supply of quick-recovery distributed power source load or micro-capacitance sensor internal load soon, reduce interruption duration and customer complaint.
Summary of the invention
For overcoming the deficiency that above-mentioned prior art exists, the invention provides a kind of photovoltaic micro failure separation method based on fault case, it effectively can reduce power failure range when there is single phase ground fault or transient fault, improves the power supply reliability of the power distribution network containing photovoltaic micro.
The present invention solves the technical scheme that its technical problem takes: a kind of photovoltaic micro failure separation method based on fault case, is characterized in that, comprise the following steps:
(1) subregion is carried out to micro-capacitance sensor: according to the annexation with power distribution network major network, the micro-capacitance sensor containing photovoltaic in power distribution network is carried out subregion, be divided into multiple micro-capacitance sensor subregion, point of common coupling PCC between each micro-capacitance sensor subregion and higher level's electrical network installs demarcation switch, between each micro-capacitance sensor subregion bus and higher level's electrical network bus, be equiped with open delta voltage instrument transformer, each load feeder and supply line of power distribution network are installed three phase current mutual inductors and a zero sequence current mutual inductor respectively;
(2) fault section is isolated: when open delta voltage instrument transformer detects single phase ground fault or overcurrent protection action, by the zero sequence current mutual inductor determination faulty line on circuit, determine the micro-capacitance sensor subregion that breaks down and subordinate's subregion thereof according to faulty line, and fault micro-capacitance sensor subregion is isolated;
(3) single phase ground fault line is excised: the three-phase current sampled signal obtaining each load feeder and supply line in fault micro-capacitance sensor subregion, three-phase current signal obtains phase angle and the amplitude of zero-sequence current through S-transformation, the three-line of zero-sequence current amplitude maximum is selected to compare, fault phase line is selected, excision single phase ground fault line by the phase angle comparing zero-sequence current;
(4) fault micro-capacitance sensor partition recovery is powered: measure whether also there is fault by the current transformer of the voltage transformer at fault micro-capacitance sensor subregion demarcation switch place, each feeder line and supply line, when this fault micro-capacitance sensor subregion still exists single phase ground fault, repeat step (3) and single phase ground fault line is excised; When this fault micro-capacitance sensor subregion exists other permanent faults, disconnect its demarcation switch and make subordinate's subregion islet operation, again restore electricity; When each feeder line in this fault micro-capacitance sensor subregion and supply line recover normal, in this fault micro-capacitance sensor subregion, photo-voltaic power supply DG again accesses micro-capacitance sensor after the time delay T1 time, and the demarcation switch of this fault micro-capacitance sensor subregion closed and subordinate's subregion demarcation switch thereof, distribution system recovers normal power supply again.
Preferably, whether described demarcation switch is directly connected with higher level's electrical network bus according to micro-capacitance sensor subregion bus is carried out classification, and demarcation switch is divided into 1 to N level demarcation switch, and wherein N >=1, N is natural number.
Preferably, the demarcation switch of described micro-capacitance sensor subregion and transformer station's outlet switch have single-phase earth fault line selection and a high-speed reclosure function simultaneously.
Preferably, the described process by the zero sequence current mutual inductor determination faulty line on circuit comprises the following steps:
Set up substation cable outlet fault simulation model: set up substation cable outlet fault simulation model according to substation cable outlet and distribution network model, described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault;
Obtain training sample: respectively different faults distance, different transition resistance and different faults initial phase angle are arranged to bar outlet circuit each in substation cable outlet fault simulation model and emulate, extract electric current initial row ripple and the transient signal of each bar outlet circuit; According to amplitude, the phase place of the amplitude of electric current initial row ripple zero _exit, polarity and transient state dominant frequency, obtain training sample;
BP neural metwork training: utilize training sample to train BP neural network model;
Obtain modulus maximum and the polarity of electric current initial row ripple zero _exit: zero sequence current mutual inductor is set in every bar outlet circuit of transformer station, utilize zero sequence current mutual inductor to obtain zero mould electric current of each bar circuit, extracted modulus maximum and the polarity of initial wavefront by wavelet analysis method;
Extract transient state dominant frequency amplitude and phase place: utilize zero sequence current mutual inductor to obtain zero mould current temporary state waveform, obtained amplitude and the phase place of each bar circuit transient state dominant frequency by fft algorithm;
Undertaken determining faulty line by neural net: the BP neural net that the amplitude of the modulus maximum of capable for the initial current extracted ripple, polarity and transient state dominant frequency, polarity input are trained, determine faulty line.
Preferably, the process of establishing of described substation cable outlet fault simulation model comprises the following steps:
The selection of simulation modeling instrument and data analysis tool: PSCAD selected by simulation modeling instrument, data analysis tool selects MATLAB;
Set up substation cable outlet fault simulation model and emulation module: described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault; Described emulation module comprises cable line module, overhead transmission line module, short trouble and FCM fault control module, cable main insulation fault and overhead wire fault verification module;
Simulation parameter is arranged: arrange the setting of PSCAD simulation parameter, cable data, overhead transmission line parameter and failed controller parameter;
Generate substation cable outlet fault simulation model: generate substation cable outlet fault simulation model according to the foundation of emulation module and optimum configurations.
Preferably, described the process that fault micro-capacitance sensor subregion carries out isolating to be comprised the following steps:
The demarcation switch of fault micro-capacitance sensor subregion and subordinate's subregion demarcation switch thereof are all disconnected;
The photo-voltaic power supply DG of disconnection is connected with electrical network by the anti-islanding switch triggering photo-voltaic power supply DG in this fault micro-capacitance sensor subregion;
The demarcation switch time delay T2 time of fault micro-capacitance sensor subregion carries out a high-speed reclosure, by a high-speed reclosure of this demarcation switch, and excision transient fault circuit.
Preferably, described time T2 is 1.5 ~ 2.5 seconds.
Preferably, the selection course of described single phase ground fault line comprises the following steps:
When generation single phase ground fault, faulty line and the zero-sequence current phase angle difference 180 degree perfecting circuit, gather the zero sequence current signal of many feeder lines, sample frequency is 10kHZ;
S-transformation is carried out to current sampling signal, obtains amplitude and the phase angle of zero-sequence current;
The three-line choosing zero-sequence current amplitude maximum compares, if the difference of the phase angle of a certain phase current and other phase current phase angles exceedes phase angle threshold value 90 degree, then this circuit is fault phase, if the difference of the phase angle of a certain phase current and other phase current phase angles is less than phase angle threshold value 90 degree, then this circuit is for being healthy phases.
Preferably, described time T1 is 30 seconds.
Beneficial effect of the present invention is as follows:
Present invention utilizes the thought of micro-capacitance sensor rationalization partition, strong tie in micro-capacitance sensor partitioned area, interregional weak coupling, rationally arranges protected mode, reduces power failure range, improves power supply reliability.Micro-capacitance sensor is carried out rational subregion, by demarcation switch isolated fault section, decreases the scope of power failure; By making full use of the intrinsic anti-islanding protection function of photovoltaic DC-to-AC converter; after photo-voltaic power supply and power distribution network are isolated; power distribution network will revert to traditional Radial network again; traditional fault-line selecting method can be adopted, solve the insecure problem of relaying protection that the power distribution network containing photo-voltaic power supply causes due to the two-way flow of power.
The S-transformation method of the present invention by zero-sequence current in failure line selection chooses single-phase fault ground path, after small current neutral grounding distribution system generation single phase ground fault, containing abundant fault message in zero-sequence current fault component, and the phase information of fault component is the important evidence judging faulty line.Therefore the present invention utilize can extract phase information time frequency analyzing tool---S-transformation is as the signal analysis means of failure line selection.Because the capacity of distributed power source is less, it can not produce larger impact to the impact of short circuit current, therefore adopts S-transformation method to carry out single-phase fault route selection and can accurately select fault phase line, improve the reliability of relaying protection and the accuracy rate of route selection.
The present invention is by the zero sequence current mutual inductor determination faulty line on circuit, and it can solve the problem of current fault line selection for indirectly grounding power system difficulty, effectively realizes the failure line selection of substation cable outlet and distribution line thereof.Because row ripple route selection method affects comparatively large by fault moment phase angle, affect less by transition resistance and fault distance; And affecting comparatively large by transition resistance and fault distance based on the selection method of transient state dominant frequency, the impact by fault moment phase angle is less; Therefore, the present invention utilizes artificial neural net to determine faulty line to traveling wave method and transient state dominant frequency method by proposition, achieve the mutual supplement with each other's advantages of traveling wave method and transient state dominant frequency method, solve the problem of current fault line selection for indirectly grounding power system difficulty, effectively achieve the failure line selection of substation cable outlet and distribution line thereof.
Accompanying drawing explanation
Below in conjunction with accompanying drawing, the present invention is further described:
Fig. 1 is method flow diagram of the present invention;
Fig. 2 is that the present invention carries out the schematic diagram of subregion to photovoltaic micro;
In figure: PCC0, PCC1 are point of common coupling, S11, S12 are one-level demarcation switch, and S21 is secondary demarcation switch, and DG is distributed power source.
Embodiment
For clearly demonstrating the technical characterstic of this programme, below by embodiment, and in conjunction with its accompanying drawing, the present invention will be described in detail.Disclosing hereafter provides many different embodiments or example is used for realizing different structure of the present invention.Of the present invention open in order to simplify, hereinafter the parts of specific examples and setting are described.In addition, the present invention can in different example repeat reference numerals and/or letter.This repetition is to simplify and clearly object, itself does not indicate the relation between discussed various embodiment and/or setting.It should be noted that parts illustrated in the accompanying drawings are not necessarily drawn in proportion.Present invention omits the description of known assemblies and treatment technology and process to avoid unnecessarily limiting the present invention.
As shown in Figure 1, a kind of photovoltaic micro failure separation method based on fault case of the present invention, it comprises the following steps:
(1) subregion is carried out to micro-capacitance sensor: according to the annexation with power distribution network major network, the micro-capacitance sensor containing photovoltaic in power distribution network is carried out subregion, be divided into multiple micro-capacitance sensor subregion, point of common coupling PCC between each micro-capacitance sensor subregion and higher level's electrical network installs demarcation switch, whether described demarcation switch is directly connected according to micro-capacitance sensor subregion bus and higher level's electrical network bus is divided into 1 to N level demarcation switch, wherein N >=1, N is natural number; Open delta voltage instrument transformer is equiped with, for detecting single phase ground fault between each micro-capacitance sensor subregion bus and higher level's electrical network bus; Each load feeder and supply line of power distribution network are installed three phase current mutual inductors and a zero sequence current mutual inductor respectively; The demarcation switch of described micro-capacitance sensor subregion and transformer station's outlet switch have single-phase earth fault line selection and a high-speed reclosure function simultaneously.
(2) fault section is isolated: when open delta voltage instrument transformer detects single phase ground fault or overcurrent protection action; by the zero sequence current mutual inductor determination faulty line on circuit; determine the micro-capacitance sensor subregion that breaks down and subordinate's subregion thereof according to faulty line, and fault micro-capacitance sensor subregion is isolated.
(3) single phase ground fault line is excised: the three-phase current sampled signal obtaining each load feeder and supply line in fault micro-capacitance sensor subregion, three-phase current signal obtains phase angle and the amplitude of zero-sequence current through S-transformation, the three-line of zero-sequence current amplitude maximum is selected to compare, fault phase line is selected, excision single phase ground fault line by the phase angle comparing zero-sequence current.
(4) fault micro-capacitance sensor partition recovery is powered: measure whether also there is fault by the current transformer of the voltage transformer at fault micro-capacitance sensor subregion demarcation switch place, each feeder line and supply line, when this fault micro-capacitance sensor subregion still exists single phase ground fault, repeat step (3) and single phase ground fault line is excised; When this fault micro-capacitance sensor subregion exists other permanent faults, disconnect its demarcation switch and make subordinate's subregion islet operation, again restore electricity; When each feeder line in this fault micro-capacitance sensor subregion and supply line recover normal, in this fault micro-capacitance sensor subregion, photo-voltaic power supply DG again accesses micro-capacitance sensor after the time delay T1 time, and the demarcation switch of this fault micro-capacitance sensor subregion closed and subordinate's subregion demarcation switch thereof, distribution system recovers normal power supply again, and described time T1 is preferably 30 seconds.
Preferably, the described process by the zero sequence current mutual inductor determination faulty line on circuit comprises the following steps:
Set up substation cable outlet fault simulation model: set up substation cable outlet fault simulation model according to substation cable outlet and distribution network model, described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault;
Obtain training sample: respectively different faults distance, different transition resistance and different faults initial phase angle are arranged to bar outlet circuit each in substation cable outlet fault simulation model and emulate, extract electric current initial row ripple and the transient signal of each bar outlet circuit; According to amplitude, the phase place of the amplitude of electric current initial row ripple zero _exit, polarity and transient state dominant frequency, obtain training sample;
BP neural metwork training: utilize training sample to train BP neural network model;
Obtain modulus maximum and the polarity of electric current initial row ripple zero _exit: zero sequence current mutual inductor is set in every bar outlet circuit of transformer station, utilize zero sequence current mutual inductor to obtain zero mould electric current of each bar circuit, extracted modulus maximum and the polarity of initial wavefront by wavelet analysis method;
Extract transient state dominant frequency amplitude and phase place: utilize zero sequence current mutual inductor to obtain zero mould current temporary state waveform, obtained amplitude and the phase place of each bar circuit transient state dominant frequency by fft algorithm;
Undertaken determining faulty line by neural net: the BP neural net that the amplitude of the modulus maximum of capable for the initial current extracted ripple, polarity and transient state dominant frequency, polarity input are trained, determine faulty line.
Preferably, the process of establishing of described substation cable outlet fault simulation model comprises the following steps:
The selection of simulation modeling instrument and data analysis tool: PSCAD selected by simulation modeling instrument, data analysis tool selects MATLAB;
Set up substation cable outlet fault simulation model and emulation module: described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault; Described emulation module comprises cable line module, overhead transmission line module, short trouble and FCM fault control module, cable main insulation fault and overhead wire fault verification module;
Simulation parameter is arranged: arrange the setting of PSCAD simulation parameter, cable data, overhead transmission line parameter and failed controller parameter;
Generate substation cable outlet fault simulation model: generate substation cable outlet fault simulation model according to the foundation of emulation module and optimum configurations.
Preferably, described the process that fault micro-capacitance sensor subregion carries out isolating to be comprised the following steps:
The demarcation switch of fault micro-capacitance sensor subregion and subordinate's subregion demarcation switch thereof are all disconnected;
The photo-voltaic power supply DG of disconnection is connected with electrical network by the anti-islanding switch triggering photo-voltaic power supply DG in this fault micro-capacitance sensor subregion;
The demarcation switch time delay T2 time of fault micro-capacitance sensor subregion carries out a high-speed reclosure, and by a high-speed reclosure of this demarcation switch, excision transient fault circuit, described time T2 is preferably 1.5 ~ 2.5 seconds.
Preferably, the selection course of described single phase ground fault line comprises the following steps:
When generation single phase ground fault, faulty line and the zero-sequence current phase angle difference 180 degree perfecting circuit, gather the zero sequence current signal of many feeder lines, sample frequency is 10kHZ;
S-transformation is carried out to current sampling signal, obtains amplitude and the phase angle of zero-sequence current;
The three-line choosing zero-sequence current amplitude maximum compares, if the difference of the phase angle of a certain phase current and other phase current phase angles exceedes phase angle threshold value 90 degree, then this circuit is fault phase, if the difference of the phase angle of a certain phase current and other phase current phase angles is less than phase angle threshold value 90 degree, then this circuit is for being healthy phases.
As shown in Figure 2, micro-capacitance sensor is divided into micro-capacitance sensor subregion 1, micro-capacitance sensor subregion 1 and micro-capacitance sensor subregion 3 three districts by the present invention, each micro-capacitance sensor is connected with power distribution network outlet switch by public coupling bus PCC0, according to the annexation of micro-capacitance sensor subregion and power distribution network bus PCC0, one-level demarcation switch S11, S12 and secondary demarcation switch is divided into by demarcation switch to be S21.
When demarcation switch S11 place open delta voltage instrument transformer detects, single phase ground fault or overcurrent protection action occur, the zero sequence current mutual inductor determination fault section on circuit, supposes to determine to break down as P1 point.Then the demarcation switch S11 at the corresponding levels of fault micro-capacitance sensor subregion 1 and subordinate demarcation switch S21 all disconnects, the anti-islanding switch motion of whole photo-voltaic power supply DG in this fault micro-capacitance sensor subregion 1, disconnect the connection of photo-voltaic power supply DG and electrical network, a high-speed reclosure is carried out in the demarcation switch S11 at the corresponding levels time delay of fault micro-capacitance sensor subregion 1 for 1.5 ~ 2.5 seconds, by a high-speed reclosure of this demarcation switch, excision transient fault circuit.
Obtain fault micro-capacitance sensor subregion 1 Nei Ge supply line three-phase current sampled signal, three-phase current signal obtains phase angle and the amplitude of zero-sequence current through S-transformation, the three-line of zero-sequence current amplitude maximum is selected to compare, fault phase line is selected, the single phase ground fault line of the supply line at excision P1 place, fault point by the phase angle comparing zero-sequence current.
Micro-capacitance sensor fault subregion demarcation switch S11 place voltage transformer, each feeder line and supply line's current transformer is utilized to measure whether also there is fault, when fault micro-capacitance sensor subregion 1 still exists single phase ground fault, repeat the step of being carried out by single phase ground fault line excising; When fault micro-capacitance sensor subregion 1 exists other permanent faults, disconnect demarcation switch S11 Hou Ze subordinate micro-capacitance sensor subregion 2 islet operation, again restore electricity; When each feeder line in fault micro-capacitance sensor subregion 1 and supply line recover normal, photo-voltaic power supply DG in fault micro-capacitance sensor subregion 1 again accesses micro-capacitance sensor after the time delay of 30s, and closed subregion demarcation switch S11 at the corresponding levels and subordinate micro-capacitance sensor subregion demarcation switch S21, distribution system recovers normal power supply again.
For containing the single phase ground fault in the power distribution network of photovoltaic micro and transient fault, the invention provides a kind of effective fault case partition method, micro-capacitance sensor is carried out rational subregion, by demarcation switch isolated fault section, decreases the scope of power failure; By making full use of the intrinsic anti-islanding protection function of photovoltaic DC-to-AC converter; after photo-voltaic power supply and electrical network are isolated; faulty line is chosen by S-transformation; improve the reliability of relaying protection and the accuracy rate of route selection; solve the insecure problem of relaying protection that the power distribution network containing photo-voltaic power supply causes due to the two-way flow of power; the present invention to the single phase ground fault in power distribution network and other transient faults, such as, is struck by lightning, circuit discharges in short-term, strong wind causes wiring in short-term etc. to have good protected effect.
Present invention utilizes the thought of micro-capacitance sensor rationalization partition, strong tie in micro-capacitance sensor partitioned area, interregional weak coupling, rationally arranges protected mode, reduces power failure range, improves power supply reliability.Micro-capacitance sensor is carried out rational subregion, by demarcation switch isolated fault section, decreases the scope of power failure; By making full use of the intrinsic anti-islanding protection function of photovoltaic DC-to-AC converter; after photo-voltaic power supply and power distribution network are isolated; power distribution network will revert to traditional Radial network again; traditional fault-line selecting method can be adopted, solve the insecure problem of relaying protection that the power distribution network containing photo-voltaic power supply causes due to the two-way flow of power.
The present invention have employed S-transformation in single-phase fault route selection process, and after small current neutral grounding distribution system generation single phase ground fault, containing abundant fault message in zero-sequence current fault component, and the phase information of fault component is the important evidence judging faulty line.Therefore the present invention utilize can extract phase information time frequency analyzing tool---S-transformation is as the signal analysis means of failure line selection.The S-transformation that R.G.Stockwell etc. propose is that people study an important tool of the time-frequency distributions of non-stationary signal in recent years, as a kind of Time-Frequency Analysis Method, S-transformation is the expansion to continuous wavelet transform and Short Time Fourier Transform, it has the outstanding time frequency analysis ability of wavelet transformation, and by utilizing fast Fourier transform, improve arithmetic speed.Compared with wavelet transformation, S-transformation not only can extract the amplitude information of primary signal, and can extract phase angle information.Because the capacity of distributed power source is less, it can not produce larger impact to the impact of short circuit current, therefore adopts S-transformation method to carry out single-phase fault route selection and can accurately select fault phase line, improve the reliability of relaying protection and the accuracy rate of route selection.
The above is the preferred embodiment of the present invention, and for those skilled in the art, under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications are also regarded as protection scope of the present invention.
Claims (9)
1., based on a photovoltaic micro failure separation method for fault case, it is characterized in that, comprise the following steps:
(1) subregion is carried out to micro-capacitance sensor: according to the annexation with power distribution network major network, the micro-capacitance sensor containing photovoltaic in power distribution network is carried out subregion, be divided into multiple micro-capacitance sensor subregion, point of common coupling PCC between each micro-capacitance sensor subregion and higher level's electrical network installs demarcation switch, between each micro-capacitance sensor subregion bus and higher level's electrical network bus, be equiped with open delta voltage instrument transformer, each load feeder and supply line of power distribution network are installed three phase current mutual inductors and a zero sequence current mutual inductor respectively;
(2) fault section is isolated: when open delta voltage instrument transformer detects single phase ground fault or overcurrent protection action, by the zero sequence current mutual inductor determination faulty line on circuit, determine the micro-capacitance sensor subregion that breaks down and subordinate's subregion thereof according to faulty line, and fault micro-capacitance sensor subregion is isolated;
(3) single phase ground fault line is excised: the three-phase current sampled signal obtaining each load feeder and supply line in fault micro-capacitance sensor subregion, three-phase current signal obtains phase angle and the amplitude of zero-sequence current through S-transformation, the three-line of zero-sequence current amplitude maximum is selected to compare, fault phase line is selected, excision single phase ground fault line by the phase angle comparing zero-sequence current;
(4) fault micro-capacitance sensor partition recovery is powered: measure whether also there is fault by the current transformer of the voltage transformer at fault micro-capacitance sensor subregion demarcation switch place, each feeder line and supply line, when this fault micro-capacitance sensor subregion still exists single phase ground fault, repeat step (3) and single phase ground fault line is excised; When this fault micro-capacitance sensor subregion exists other permanent faults, disconnect its demarcation switch and make subordinate's subregion islet operation, again restore electricity; When each feeder line in this fault micro-capacitance sensor subregion and supply line recover normal, in this fault micro-capacitance sensor subregion, photo-voltaic power supply DG again accesses micro-capacitance sensor after the time delay T1 time, and the demarcation switch of this fault micro-capacitance sensor subregion closed and subordinate's subregion demarcation switch thereof, distribution system recovers normal power supply again.
2. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, it is characterized in that, whether described demarcation switch is directly connected with higher level's electrical network bus according to micro-capacitance sensor subregion bus is carried out classification, demarcation switch is divided into 1 to N level demarcation switch, wherein N >=1, N is natural number.
3. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, is characterized in that, the demarcation switch of described micro-capacitance sensor subregion and transformer station's outlet switch have single-phase earth fault line selection and a high-speed reclosure function simultaneously.
4. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, is characterized in that, the described process by the zero sequence current mutual inductor determination faulty line on circuit comprises the following steps:
Set up substation cable outlet fault simulation model: set up substation cable outlet fault simulation model according to substation cable outlet and distribution network model, described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault;
Obtain training sample: respectively different faults distance, different transition resistance and different faults initial phase angle are arranged to bar outlet circuit each in substation cable outlet fault simulation model and emulate, extract electric current initial row ripple and the transient signal of each bar outlet circuit; According to amplitude, the phase place of the amplitude of electric current initial row ripple zero _exit, polarity and transient state dominant frequency, obtain training sample;
BP neural metwork training: utilize training sample to train BP neural network model;
Obtain modulus maximum and the polarity of electric current initial row ripple zero _exit: zero sequence current mutual inductor is set in every bar outlet circuit of transformer station, utilize zero sequence current mutual inductor to obtain zero mould electric current of each bar circuit, extracted modulus maximum and the polarity of initial wavefront by wavelet analysis method;
Extract transient state dominant frequency amplitude and phase place: utilize zero sequence current mutual inductor to obtain zero mould current temporary state waveform, obtained amplitude and the phase place of each bar circuit transient state dominant frequency by fft algorithm;
Undertaken determining faulty line by neural net: the BP neural net that the amplitude of the modulus maximum of capable for the initial current extracted ripple, polarity and transient state dominant frequency, polarity input are trained, determine faulty line.
5. a kind of photovoltaic micro failure separation method based on fault case according to claim 4, is characterized in that, the process of establishing of described substation cable outlet fault simulation model comprises the following steps:
The selection of simulation modeling instrument and data analysis tool: PSCAD selected by simulation modeling instrument, data analysis tool selects MATLAB;
Set up substation cable outlet fault simulation model and emulation module: described substation cable outlet fault simulation model comprises transformer, three outlet circuits are connected with at the outgoing line side of transformer, cable line and overhead transmission line is all comprised in every bar outlet circuit, described cable line one end is connected with transformer, the other end is connected with overhead transmission line one end, the other end of overhead transmission line is unsettled, in every bar outlet circuit, be provided with simulated line fault; Described emulation module comprises cable line module, overhead transmission line module, short trouble and FCM fault control module, cable main insulation fault and overhead wire fault verification module;
Simulation parameter is arranged: arrange the setting of PSCAD simulation parameter, cable data, overhead transmission line parameter and failed controller parameter;
Generate substation cable outlet fault simulation model: generate substation cable outlet fault simulation model according to the foundation of emulation module and optimum configurations.
6. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, is characterized in that, describedly the process that fault micro-capacitance sensor subregion carries out isolating is comprised the following steps:
The demarcation switch of fault micro-capacitance sensor subregion and subordinate's subregion demarcation switch thereof are all disconnected;
The photo-voltaic power supply DG of disconnection is connected with electrical network by the anti-islanding switch triggering photo-voltaic power supply DG in this fault micro-capacitance sensor subregion;
The demarcation switch time delay T2 time of fault micro-capacitance sensor subregion carries out a high-speed reclosure, by a high-speed reclosure of this demarcation switch, and excision transient fault circuit.
7. a kind of photovoltaic micro failure separation method based on fault case according to claim 6, it is characterized in that, described time T2 is 1.5 ~ 2.5 seconds.
8. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, it is characterized in that, the selection course of described single phase ground fault line comprises the following steps:
When generation single phase ground fault, faulty line and the zero-sequence current phase angle difference 180 degree perfecting circuit, gather the zero sequence current signal of many feeder lines, sample frequency is 10kHZ;
S-transformation is carried out to current sampling signal, obtains amplitude and the phase angle of zero-sequence current;
The three-line choosing zero-sequence current amplitude maximum compares, if the difference of the phase angle of a certain phase current and other phase current phase angles exceedes phase angle threshold value 90 degree, then this circuit is fault phase, if the difference of the phase angle of a certain phase current and other phase current phase angles is less than phase angle threshold value 90 degree, then this circuit is for being healthy phases.
9. a kind of photovoltaic micro failure separation method based on fault case according to claim 1, it is characterized in that, described time T1 is 30 seconds.
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