CN109447847A - A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch - Google Patents
A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch Download PDFInfo
- Publication number
- CN109447847A CN109447847A CN201811579251.4A CN201811579251A CN109447847A CN 109447847 A CN109447847 A CN 109447847A CN 201811579251 A CN201811579251 A CN 201811579251A CN 109447847 A CN109447847 A CN 109447847A
- Authority
- CN
- China
- Prior art keywords
- time
- failure
- isolated
- load
- distribution network
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000009826 distribution Methods 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000004088 simulation Methods 0.000 claims abstract description 31
- 238000005070 sampling Methods 0.000 claims abstract description 11
- 230000008569 process Effects 0.000 claims abstract description 8
- 238000012937 correction Methods 0.000 claims abstract description 7
- 238000002955 isolation Methods 0.000 claims description 49
- 238000011144 upstream manufacturing Methods 0.000 claims description 11
- 230000009467 reduction Effects 0.000 claims description 10
- 238000012546 transfer Methods 0.000 claims description 8
- 238000004364 calculation method Methods 0.000 claims description 7
- 238000000342 Monte Carlo simulation Methods 0.000 claims description 6
- 240000002853 Nelumbo nucifera Species 0.000 claims description 5
- 235000006508 Nelumbo nucifera Nutrition 0.000 claims description 5
- 235000006510 Nelumbo pentapetala Nutrition 0.000 claims description 5
- 230000005611 electricity Effects 0.000 claims description 5
- 230000000717 retained effect Effects 0.000 claims description 3
- 238000003860 storage Methods 0.000 claims description 2
- 230000001737 promoting effect Effects 0.000 abstract description 4
- 238000011161 development Methods 0.000 abstract description 2
- 238000011217 control strategy Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000011084 recovery Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 230000006855 networking Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000008439 repair process Effects 0.000 description 2
- 238000000638 solvent extraction Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000011218 segmentation Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q50/00—Information and communication technology [ICT] specially adapted for implementation of business processes of specific business sectors, e.g. utilities or tourism
- G06Q50/06—Energy or water supply
-
- 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
- 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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
Landscapes
- Business, Economics & Management (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Economics (AREA)
- Marketing (AREA)
- Tourism & Hospitality (AREA)
- General Health & Medical Sciences (AREA)
- Human Resources & Organizations (AREA)
- Public Health (AREA)
- Primary Health Care (AREA)
- Strategic Management (AREA)
- Water Supply & Treatment (AREA)
- Physics & Mathematics (AREA)
- General Business, Economics & Management (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch: setting the simulation year of reliability of active power distribution network, and sampling generates non-failure operation time and fault correction time of the element of active power distribution network in simulation year；Determine the type of each minimum isolated area and the operating status during failure in active power distribution network；Count the power off time of each load point during element fault in active power distribution network；Judge to simulate whether clock reaches simulation year, not up to then repeating the above process, reaching, simulation process terminates, and counts the reliability index in each simulation year, and then the average power supply availability of computing system.The present invention it can be considered that large number of intermittently distributed generation resource access, the operation control method of flexible Sofe Switch is adjusted, to promote the power supply reliability of active power distribution network.Support can be provided for the raising of existing power distribution network operational efficiency, be conducive to the management level for promoting urban power distribution network operation, promote the Rational Development of urban power distribution network.
Description
Technical field
The present invention relates to a kind of city net appraisal procedures.It is suitable for public organizations' urban power distribution network more particularly to one kind to assess
The active power distribution network Reliability Estimation Method containing flexible Sofe Switch.
Background technique
Power distribution network is the knob for contacting user and hair, transmission system as electrical energy production, transmission and the important link used
Band.Power distribution network carries the vital task that electric energy is transferred to different voltages class user from power supply or power transmission network, directly with use
Family is connected, and is affected to power supply reliability.According to the statistics of Utilities Electric Co., 80% user's power outage is by distribution system event
Caused by barrier.Therefore, it is particularly significant quickly and accurately to carry out evaluating reliability of distribution network.And in distributed generation resource, especially between
After having a rest property distributed generation resource largely accesses power distribution network, because its operation characteristic is affected by environment larger and have apparent randomness and
Fluctuation can bring problems to power distribution network, such as voltage out-of-limit, network congestion, power reliably to influence active power distribution network
Property.Therefore, the power supply reliability for promoting active power distribution network has great importance to the operation level for improving active power distribution network.
And the power supply reliability lifting means in conventional electrical distribution net are limited, it is difficult to cope with large number of intermittently distributed generation resource
Access.Flexible Sofe Switch (Soft open point, SOP) is the traditional interconnection switch of substitution derived in the above context
A kind of novel intelligent power distribution equipment.Compared with the operation of traditional interconnection switch, SOP can neatly exchange active power and compensation nothing
Function power, it might even be possible to network trend be controlled in real time, advantageously account for the access band of large number of intermittently distributed generation resource
The power supply reliability problem come.Meanwhile also the method for operation to conventional electrical distribution net and failure turn to have occurred for mode very greatly SOP
Variation.Therefore, active power distribution network Reliability Estimation Method of the research containing SOP has great importance.
Summary of the invention
The technical problem to be solved by the invention is to provide a kind of containing for power supply reliability for being able to ascend active power distribution network
The active power distribution network Reliability Estimation Method of SOP.
The technical scheme adopted by the invention is that: a kind of active power distribution network Reliability Evaluation side containing flexible Sofe Switch
Method includes the following steps:
1) the simulation year of reliability of active power distribution network is set, sampling generates the element of active power distribution network in simulation year
Non-failure operation time and fault correction time in number；
2) type of each minimum isolated area and the operating status during failure in active power distribution network are determined；
3) power off time of each load point during element fault in active power distribution network, new fortune of sampling to fault element are counted
Row time TTTFnew, the non-failure operation time of fault element is updated to TTTFmin+TTTR+TTTFnew, judge to simulate clock
Whether across year, the load point power off time of statistics load point current year, power off time year U is not added to then across yearxIn；Then across year
Using the year reliability index of reliability index calculation formula computing system, and by UxIt resets；Reliability index calculation formula is such as
Under:
In formula, T is need electricity hourage at the appointed time；UxFor the idle time in year of load point x；NyFor load point y's
Number of users；NxFor the number of users of load point x；Initial user number is set as 1；P is system total load points；EsExpression system is reliable
Property target.
4) judge to simulate whether clock reaches simulation year, not up to then return step 1, reach, simulation process terminates,
Count the reliability index in each simulation year, and then the average power supply availability of computing system.
Step 1) includes: to share m element in simulation year in setting active power distribution network, simulates all members of initial time
Part works in normal condition, and the non-failure operation time TTTF of m element is randomly generated according to failure rate of transform λ, finds out most
Small non-failure operation time TTTFmin, by the smallest non-failure operation time TTTFminCorresponding element as fault element,
The fault correction time TTTR of the fault element is randomly generated according to rate of transform μ is repaired, and sets the event of the fault element
Hinder isolation time, simulation clock is advanced to TTTFmin+TTTR。
Step 2) comprise determining that in active power distribution network it is each minimum isolated area type, directly determine faulty section, normal area with
And the power off time of upstream isolated area internal loading point, the region of isolated operation is in remaining region, according to element fault model,
Using the operating status of source element in non-sequential Monte Carlo method sampling active power distribution network, real-time load value, electric power storage are obtained
Pond charge-discharge electric power sequence and photovoltaic power output sequence, and then model is cut down according to load and calculates each in the region of isolated operation bear
The power off time of lotus point；The region for turning to supply is got in touch with for needs, is sampled using non-sequential Monte Carlo method wait turn to supply and contact
The operating status of source element, in real time power output and real-time load value in region, and the load factor of interconnection tie is combined to constrain, with
Minimum isolated area is that unit carries out load transfer.
The type of each minimum isolated area includes in the active power distribution network:
Faulty section: the minimum isolated area of moment to fault restoration moment power loss always occurs in failure；
Normal area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure；
Upstream isolated area: the moment occurs to power loss at the time of failure completion isolation, in failure completion isolation in failure
It is carved into the minimum isolated area of fault restoration moment normal power supply；
Upstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure completion
To the minimum isolated area of fault restoration moment normal power supply at the time of isolation；
Downstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure completion
To the minimum isolated area of fault restoration moment isolated operation at the time of isolation；
Isolated island area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment isolated operation minimum isolated area；
Downstream is seamless isolated island association area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure
To the minimum isolated area of fault restoration moment isolated operation at the time of completing to be isolated；
Isolated island association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes in failure
To the minimum isolated area of fault restoration moment isolated operation at the time of isolation；
Association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment normal power supply minimum isolated area；
Downstream isolated island association area: the moment occurs to isolated operation at the time of failure completion isolation in failure, is completed in failure
To the minimum isolated area of fault restoration moment normal power supply at the time of isolation；
Downstream is seamless association area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure.
The power off time that model calculates each load point in the region of isolated operation is cut down according to load, comprising:
(2.1) load is provided first and is cut down determines formula:
In formula, PdmaxIt (t) is the maximum allowable discharge power of battery in t moment isolated island；PDG(t) in t moment isolated island
Photovoltaic gross capability；LktIt (t) is the real-time load of k-th of load point of t moment；NLFor load point sum；X (k) is k-th of load
Point retains when being equal to 1 in the reduction state of t moment, cuts down when being equal to 0；tstFor isolated island initial time, tendFor isolated island knot
The beam moment；
(2.2) since isolated island forms the moment, each time phase is taken as 1h, each time phase initial time setting
Each load point is retained, and judges whether isolated island meets load and cut down judgement formula in each time phase respectively, if full
Reduction that is sufficient then needing to carry out load one by one according to the significance level of load point, it is preferential to cut down the low load of significance level, until
Sub-load is cut down until determining formula, counts the power off time of each load point in each time phase, more new accumulator respectively
State-of-charge, until the isolated operation stage terminate；
(2.3) it carries out turning to supply after failure completes isolation, the Object selection of load transfer is to turn balanced for rear feeder load
Degree is maximum and turns to indicate for the maximum target of load significance level are as follows:
In formula, XlThe reduction state for indicating first of minimum isolated area indicates not cut down when equal to 1, indicates to cut when equal to 0
Subtract；RiIndicate i-th feeder line load factor；RjIndicate j-th strip feeder line load factor；Li indicates the load of i-th feeder line；Ci indicates i-th
The capacity of feeder line；LlIndicate the load of first of minimum isolated area；N indicates feeder line number；D indicates minimum isolated area number.
A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch of the invention, it can be considered that between a large amount of
The access of having a rest property distributed generation resource adjusts the operation control method of flexible Sofe Switch, so that the power supply for promoting active power distribution network can
By property.Support can be provided for the raising of existing power distribution network operational efficiency, be conducive to the management water for promoting urban power distribution network operation
It is flat, promote the Rational Development of urban power distribution network.
Detailed description of the invention
Fig. 1 is a kind of flow chart of the active power distribution network Reliability Estimation Method containing flexible Sofe Switch of the present invention；
Fig. 2 is containing three port SOP and to contain two for one for patch bay abortive haul structure of modification comparison diagram；
Fig. 3 is typical Feeder partitioning schematic diagram；
Fig. 4 is the practical distribution net work structure schematic diagram in somewhere；
Fig. 5 is the active power distribution network structural schematic diagram containing three port SOP.
Specific embodiment
Below with reference to embodiment and attached drawing to a kind of active power distribution network power supply reliability containing flexible Sofe Switch of the invention
Appraisal procedure is described in detail.
The control model of flexible Sofe Switch (SOP) includes SOP control model and fault recovery under normal running (operation) conditions
Under the conditions of SOP control model.Wherein,
SOP control model under normal running (operation) conditions: being under power distribution network normal running (operation) conditions, SOP controls feeder line trend
Two close cycles Current Control Strategy is taken in distribution, and side VSC is controlled using PQ, and other side VSC uses VdcQ control.The control strategy
The advantages of be SOP can with independent control active power and reactive power, and can limit when breaking down by SOP's
Size of current.Two close cycles Current Control Strategy includes outer layer power control closed loop, internal layer current control closed loop and phaselocked loop.
SOP control model under the conditions of fault recovery: being after power distribution network breaks down, closure contact is opened after isolated fault
Pass can make power loss load be connected with power supply.When power loss region can be connected by interconnection switch with upper network, SOP event
Barrier side VSC is completed to turn off, restarted, after Vf control model boost process, and fault recovery stage control strategy is that Vf controls mould
Formula；Normal side VSC is VdcQ control model.
Active power distribution network networking form containing SOP
The two of conventional electrical distribution net have higher permission load factor than simply connected network wiring for wiring for one, following to divide at high proportion
Cloth power supply needs more flexible smooth network structure.Therefore, urban power distribution network carries out networking to more feedback lines using multiterminal SOP
It is more particularly suitable.To supply an active power distribution network networking for patch bay abortive haul Structure Comparison discussion containing SOP containing three port SOP and containing two
Form, for transformation process as shown in Fig. 2, the top Fig. 2 is divided into the aerial web frame for not accessing SOP, lower part is divided into the frame for not accessing SOP
Abortive haul structure.
In Fig. 2, interconnection switch S1 is replaced with three port SOP and the mode of connection is transformed, be closed interconnection switch S3, remove superfluous
Remaining switch S2,3 feedback lines realize flexible operation with closed ring (after access SOP) after transformation.Feeder line 3 is in the aerial web frame before transformation
Only spare feeder line 2, which provides, to be turned for support, but after transformation, turns to supply when feeder line 1 and feeder line 2 can provide failure for feeder line 3
Power supply reliability can be improved in the case where feeder line heavy duty in support.It is right but if feeder load has met N-1 criterion
Side feeder line can provide enough turn for support, therefore replace interconnection switch that will not improve confession again using three port SOP
Electric reliability, the problem will be described below example and be discussed in detail.In addition, load is generally unevenly distributed weighing apparatus in practice, but by
In in normal operation, the marine tidal-current energy choice direction between 3 feedback lines got in touch with SOP phase is smoothly mutually supported, therefore is contained
The feeder line equivalent load of SOP power distribution network can but accomplish relative equilibrium, the mesh for reaching balanced feeder load, improving feeder load distribution
's.
As shown in Figure 1, a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch of the invention, including
Following steps:
1) the simulation year of reliability of active power distribution network is set, sampling generates the element of active power distribution network in simulation year
Non-failure operation time and fault correction time in number；Include:
It sets and shares m element in active power distribution network in simulation year, simulation all elements of initial time work in
Normal condition.The non-electrical source element such as main transformer, feeder line and switch can repair forced outage model using two states, and failure turns in model
Shifting rate is λ, and the reparation rate of transform is μ, the sequential sampling adoption status duration sampling of state.According to failure rate of transform λ
The non-failure operation time TTTF of m element is randomly generated, finds out the smallest non-failure operation time TTTFmin, by the smallest nothing
Failure operation time TTTFminThe fault element is randomly generated as fault element, according to rate of transform μ is repaired in corresponding element
Fault correction time TTTR, and set the Fault Isolation time of the fault element, simulation clock be advanced to TTTFmin+
TTTR。
2) type of each minimum isolated area and the operating status during failure in active power distribution network are determined；Include:
The type for determining each minimum isolated area in active power distribution network directly determines faulty section, normal area and upstream isolation
The power off time of area's internal loading point is in the region of isolated operation in remaining region, according to element fault model, using non-sequential
The operating status of source element, obtains real-time load value, accumulator cell charging and discharging function in Monte Carlo method sampling active power distribution network
Rate sequence and photovoltaic power output sequence, and then the power failure that model calculates each load point in the region of isolated operation is cut down according to load
Time；
Distributed photovoltaic array and battery use three condition model, are divided into normal, stoppage in transit and drop volume operating status.Photovoltaic
The calculating of power output can calculate annual photovoltaic power output in real time using photovoltaic segmentation power output model according to annual light intensity hourly.
Calculating for load power output is formed and is born in real time by the Typical Year of load-week curve, day in week-curve and hour day-curve
Lotus data use t hours load LtFor
Lt=Lp×Pw×Pd×Ph(t) (1)
In formula, LpFor year load peak；PwFor year-corresponding with t-th hour all load percentage coefficients；PdFor correspondence
Week-daily load percent coefficient；Ph(t) be corresponding hour day-load percentage coefficient, be divided into resident, commercially with industry
Three classes load coefficient.
Battery model uses two pool models of lead-acid accumulator.Its timing simulation can be divided into the simulation of charge and discharge process
With the simulation of state-of-charge variation, it can determine that the power output of battery is bent by the simulation repeatedly of charge-discharge electric power and state-of-charge
Line.
The region for turning to supply is got in touch with for needs, is sampled using non-sequential Monte Carlo method wait turn to supply and electricity in contact region
The operating status of source element, in real time power output and real-time load value, and the load factor of interconnection tie is combined to constrain, with minimum isolation
Area is that unit carries out load transfer.Wherein,
The type of each minimum isolated area includes in the active power distribution network:
Faulty section: the minimum isolated area of moment to fault restoration moment power loss always occurs in failure；
Normal area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure；
Upstream isolated area: the moment occurs to power loss at the time of failure completion isolation, in failure completion isolation in failure
It is carved into the minimum isolated area of fault restoration moment normal power supply；
Upstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure completion
To the minimum isolated area of fault restoration moment normal power supply at the time of isolation；
Downstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure completion
To the minimum isolated area of fault restoration moment isolated operation at the time of isolation；
Isolated island area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment isolated operation minimum isolated area；
Downstream is seamless isolated island association area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure
To the minimum isolated area of fault restoration moment isolated operation at the time of completing to be isolated；
Isolated island association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes in failure
To the minimum isolated area of fault restoration moment isolated operation at the time of isolation；
Association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment normal power supply minimum isolated area；
Downstream isolated island association area: the moment occurs to isolated operation at the time of failure completion isolation in failure, is completed in failure
To the minimum isolated area of fault restoration moment normal power supply at the time of isolation；
Downstream is seamless association area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure.
The example of typical Feeder partitioning is as shown in Figure 3 and Table 1.
Active power distribution network area principle of the table 1 containing SOP
| Area type | t1~t2 | t2~t3 | Example |
| Faulty section | A1 | A1 | S5 |
| Normal area | A2 | A2 | S1 |
| Upstream isolated area | A1 | A2 | S2、S3 |
| Upstream is seamless isolated island area | A3 | A2 | S4 |
| Downstream is seamless isolated island area | A3 | A3 | S7 |
| Isolated island area is isolated in downstream | A1 | A3 | S8 |
| Downstream is seamless isolated island association area | A3 | A3 | S9 |
| Isolated island association area is isolated in downstream | A1 | A3 | S10 |
| Association area is isolated in downstream | A1 | A4 | S12、S14 |
| Downstream isolated island association area | A3 | A4 | S13 |
| Downstream is seamless association area | A4 | A4 | -- |
Described cuts down the power off time that model calculates each load point in the region of isolated operation according to load, comprising:
(2.1) load is provided first and is cut down determines formula:
In formula, PdmaxIt (t) is the maximum allowable discharge power of battery in t moment isolated island；PDG(t) in t moment isolated island
Photovoltaic gross capability；LktIt (t) is the real-time load of k-th of load point of t moment；NLFor load point sum；X (k) is k-th of load
Point retains when being equal to 1 in the reduction state of t moment, cuts down when being equal to 0；tstFor isolated island initial time, tendFor isolated island knot
The beam moment；
(2.2) since isolated island forms the moment, each time phase is taken as 1h, each time phase initial time setting
Each load point is retained, and judges whether isolated island meets load and cut down judgement formula in each time phase respectively, if full
Reduction that is sufficient then needing to carry out load one by one according to the significance level of load point, it is preferential to cut down the low load of significance level, until
Sub-load is cut down until determining formula, counts the power off time of each load point in each time phase, more new accumulator respectively
State-of-charge, until the isolated operation stage terminate；
(2.3) it carries out turning to supply after failure completes isolation, the Object selection of load transfer is to turn balanced for rear feeder load
Degree is maximum and turns to indicate for the maximum target of load significance level are as follows:
In formula, XlThe reduction state for indicating first of minimum isolated area indicates not cut down when equal to 1, indicates to cut when equal to 0
Subtract；RiIndicate i-th feeder line load factor；RjIndicate j-th strip feeder line load factor；Li indicates the load of i-th feeder line；Ci indicates i-th
The capacity of feeder line；LlIndicate the load of first of minimum isolated area；N indicates feeder line number；D indicates minimum isolated area number.
3) power off time of each load point during element fault in active power distribution network, new fortune of sampling to fault element are counted
Row time TTTFnew, the non-failure operation time of fault element is updated to TTTFmin+TTTR+TTTFnew, judge to simulate clock
Whether across year, the load point power off time of statistics load point current year, power off time year U is not added to then across yearxIn；Then across year
Using the year reliability index of reliability index calculation formula computing system, and by UxIt resets；Reliability index calculation formula is such as
Under:
In formula, T is need electricity hourage at the appointed time；UxFor the idle time in year of load point x；NyFor load point y's
Number of users；NxFor the number of users of load point x；Initial user number is set as 1；P is system total load points；EsExpression system is reliable
Property target.
4) judge to simulate whether clock reaches simulation year, not up to then return step 1, reach, simulation process terminates,
Count the reliability index in each simulation year, and then the average power supply availability of computing system.
A specific example is given below:
Using the practical distribution net work structure in somewhere as example, as shown in the figure 4, its tradition interconnection switch is transform as containing three ends
The active power distribution network of mouth SOP, as shown in Figure 5.The reliability of its grid structure is analyzed.Each substation's relevant information such as table
Shown in 2, emphasis considers shadow of the failure for load point of single element in grid structure during carrying out Calculation of Reliability
It rings, specifically includes: main transformer failure, bus-bar fault, distribution transformer failure, circuit breaker failure, line fault and switch fault etc.,
The dependability parameter of each class component is as shown in table 3.
Substation's configuring condition table in 2 example of table
Main element dependability parameter in 3 system of table
| Element | λ | r | rp |
| Bus | 0.001 | 5 | ? |
| Feeder line | 0.065 | 5 | ? |
| Distribution transformer | 0.013 | ? | 5 |
| Block switch | 0.006 | 5 | ? |
| Main transformer | 0.01 | 200 | ? |
| High-voltage circuitbreaker | 0.002 | 50 | ? |
| Low-voltage circuit breaker | 0.005 | 20 | ? |
In table 2, λ be each element failure rate, unit be times/year, for feeder line be Ci/˙ km, be for main transformer
Secondary/Tai ˙；R is mean repair time, rpFor mean time between replacement, unit is hour.
Based on above description, the overall condition of example includes 2 substations, 4 main transformers, 12 feeder lines, 140 load sections
Point (8 industrial load nodes, 28 Commercial Load nodes, 104 resident load nodes), 170 distribution transformers.Industry is negative
Lotus, Commercial Load and resident load are as shown in table 4.
4 load type of table and load
| Load type | Load (family MV/) |
| Industrial load | 0.1802 |
| Commercial Load | 0.4697 |
| Resident load | 0.8472 |
Having containing three port SOP is calculated using the above-mentioned active power distribution network Reliability Estimation Method for containing three port SOP
The reliability index of source power distribution network and the active power distribution network containing traditional interconnection switch averagely powers availability index (ASAI).
According to above-mentioned analysis, it can be divided into that feeder load meets N-1 criterion scene and feeder line heavy duty scene calculates separately ASAI index, analysis
Influence of the three port SOP for power supply reliability.
(1) feeder load meets N-1 criterion scene
Choosing the initial Rate of average load of feeder line is 66.7%, calculates the active power distribution network containing three port SOP and contains tradition
The ASAI index of the active power distribution network of interconnection switch, as shown in table 5:
5 feeder load of table meets the comparison of N-1 criterion scenario A SAI index
| Power distribution network | ASAI |
| Active power distribution network containing three port SOP | 0.999820 |
| Active power distribution network containing traditional interconnection switch | 0.999802 |
(2) feeder line heavy duty scene
Choosing the initial Rate of average load of feeder line is 85%, calculates the active power distribution network containing three port SOP and connection containing tradition
The ASAI index of the active power distribution network of network switch, as shown in table 6:
The comparison of 6 feeder line heavy duty scenario A SAI index of table
| Power distribution network | ASAI |
| Active power distribution network containing three port SOP | 0.999816 |
| Active power distribution network containing traditional interconnection switch | 0.999791 |
It can analyze to obtain according to the above results: 1) in the case where feeder load meets N-1 criterion, containing the active of three port SOP
Power distribution network ASAI index is higher than the active power distribution network ASAI index containing traditional interconnection switch, because of the faster fault recovery speed of SOP
Degree and load transfer speed can directly will be wait turn the reduction for load transfer to opposite side interconnection tie after failure completes isolation
Be closed at the time of failure completes isolation to traditional interconnection switch complete downstream turn at the time of between load have a power failure loss, by
After each feed line failure, interconnection tie can provide enough turn for capacity, thus at this time three port SOP can not by for
Feeder line increases interconnection tie and improves feeder reliability；2) when being unsatisfactory for N-1 criterion, the ASAI index under two scenes is all
Meet N-1 criterion scene relative to feeder load to be declined, the active power distribution network ASAI index fall containing three port SOP
The fall of the active power distribution network ASAI index containing traditional interconnection switch can be lower than, because under traditional interconnection switch, simply connected
After network feeder fault, interconnection tie can't always be enough turn of offer for capacity.So three port SOP at this time can by for
Single interconnection tie increases interconnection tie and improves feeder reliability.
Claims (5)
1. a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch, which comprises the steps of:
1) the simulation year of reliability of active power distribution network is set, sampling generates the element of active power distribution network in simulation year
Non-failure operation time and fault correction time；
2) type of each minimum isolated area and the operating status during failure in active power distribution network are determined；
3) power off time for counting each load point during element fault in active power distribution network, to fault element sample new operation when
Between TTTFnew, the non-failure operation time of fault element is updated to TTTFmin+TTTR+TTTFnew, judge whether simulate clock
Across year, the load point power off time of statistics load point current year, power off time year U is not added to then across yearxIn；It is then used across year
The year reliability index of reliability index calculation formula computing system, and by UxIt resets；Reliability index calculation formula is as follows:
In formula, T is need electricity hourage at the appointed time；UxFor the idle time in year of load point x；NyFor the user of load point y
Number；NxFor the number of users of load point x；Initial user number is set as 1；P is system total load points；EsIndicate system reliability mesh
Mark.
4) judge to simulate whether clock reaches simulation year, not up to then return step 1, reach, simulation process terminates, statistics
The reliability index in each simulation year, and then the average power supply availability of computing system
2. a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch according to claim 1, special
Sign is that step 1) includes: to share m element in simulation year in setting active power distribution network, simulates all members of initial time
Part works in normal condition, and the non-failure operation time TTTF of m element is randomly generated according to failure rate of transform λ, finds out most
Small non-failure operation time TTTFmin, by the smallest non-failure operation time TTTFminCorresponding element as fault element,
The fault correction time TTTR of the fault element is randomly generated according to rate of transform μ is repaired, and sets the event of the fault element
Hinder isolation time, simulation clock is advanced to TTTFmin+TTTR。
3. a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch according to claim 1, special
Sign is, step 2) comprises determining that the type of each minimum isolated area in active power distribution network, directly determine faulty section, normal area with
And the power off time of upstream isolated area internal loading point, the region of isolated operation is in remaining region, according to element fault model,
Using the operating status of source element in non-sequential Monte Carlo method sampling active power distribution network, real-time load value, electric power storage are obtained
Pond charge-discharge electric power sequence and photovoltaic power output sequence, and then model is cut down according to load and calculates each in the region of isolated operation bear
The power off time of lotus point；The region for turning to supply is got in touch with for needs, is sampled using non-sequential Monte Carlo method wait turn to supply and contact
The operating status of source element, in real time power output and real-time load value in region, and the load factor of interconnection tie is combined to constrain, with
Minimum isolated area is that unit carries out load transfer.
4. a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch according to claim 1 or 3,
It is characterized in that, the type of each minimum isolated area includes in the active power distribution network:
Faulty section: the minimum isolated area of moment to fault restoration moment power loss always occurs in failure；
Normal area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure；
Upstream isolated area: the moment occurs to power loss at the time of failure completion isolation in failure, is arrived at the time of failure is completed and is isolated
The minimum isolated area of fault restoration moment normal power supply；
Upstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, complete isolation in failure
At the time of to fault restoration moment normal power supply minimum isolated area；
Downstream is seamless isolated island area: failure occur the moment complete isolation to failure at the time of isolated operation, complete isolation in failure
At the time of to fault restoration moment isolated operation minimum isolated area；
Isolated island area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation, in failure completion isolation in failure
It is carved into the minimum isolated area of fault restoration moment isolated operation；
Downstream is seamless isolated island association area: failure occur the moment complete isolation to failure at the time of isolated operation, in failure completion
To the minimum isolated area of fault restoration moment isolated operation at the time of isolation；
Isolated island association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment isolated operation minimum isolated area；
Association area is isolated in downstream: the moment occurs to power loss at the time of failure completion isolation, in failure completion isolation in failure
It is carved into the minimum isolated area of fault restoration moment normal power supply；
Downstream isolated island association area: the moment occurs to isolated operation at the time of failure completion isolation in failure, completes to be isolated in failure
At the time of to fault restoration moment normal power supply minimum isolated area；
Downstream is seamless association area: the minimum isolated area of moment to fault restoration moment normal power supply always occurs in failure.
5. a kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch according to claim 3, special
Sign is, cuts down the power off time that model calculates each load point in the region of isolated operation according to load, comprising:
(2.1) load is provided first and is cut down determines formula:
In formula, PdmaxIt (t) is the maximum allowable discharge power of battery in t moment isolated island；PDGIt (t) is the light in t moment isolated island
Lie prostrate gross capability；LktIt (t) is the real-time load of k-th of load point of t moment；NLFor load point sum；X (k) is that k-th of load point exists
The reduction state of t moment retains when being equal to 1, cuts down when being equal to 0；tstFor isolated island initial time, tendAt the end of isolated island
It carves；
(2.2) since isolated island forms the moment, each time phase is taken as 1h, each time phase initial time setting is each
Load point is retained, and judges whether isolated island meets load and cut down judgement formula in each time phase respectively, if meeting
Need to carry out the reduction of load one by one according to the significance level of load point, it is preferential to cut down the low load of significance level, until discontented
Load is cut down until determining formula, counts the power off time of each load point in each time phase, the lotus of more new accumulator respectively
Electricity condition, until the isolated operation stage terminates；
(2.3) it carries out turning to supply after failure completes isolation, the Object selection of load transfer is to turn for rear feeder load equilibrium degree most
Greatly and turn to indicate for the maximum target of load significance level are as follows:
In formula, XlThe reduction state for indicating first of minimum isolated area indicates not cut down when equal to 1, indicates to cut down when being equal to 0；Ri
Indicate i-th feeder line load factor；RjIndicate j-th strip feeder line load factor；Li indicates the load of i-th feeder line；Ci indicates i-th feedback
The capacity of line；LlIndicate the load of first of minimum isolated area；N indicates feeder line number；D indicates minimum isolated area number.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811579251.4A CN109447847A (en) | 2018-12-24 | 2018-12-24 | A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811579251.4A CN109447847A (en) | 2018-12-24 | 2018-12-24 | A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN109447847A true CN109447847A (en) | 2019-03-08 |
Family
ID=65535051
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811579251.4A Pending CN109447847A (en) | 2018-12-24 | 2018-12-24 | A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109447847A (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110994595A (en) * | 2019-11-25 | 2020-04-10 | 广东电网有限责任公司 | Power grid key equipment heavy load and out-of-limit distribution monitoring method |
| CN111030068A (en) * | 2019-12-27 | 2020-04-17 | 国电南瑞科技股份有限公司 | Power distribution network fault handling method |
| CN111404267A (en) * | 2020-02-24 | 2020-07-10 | 中国科学院电工研究所 | Multi-station integrated structure and control method thereof |
| CN111428377A (en) * | 2020-03-31 | 2020-07-17 | 国网西藏电力有限公司拉萨供电公司 | Power distribution network reliability evaluation method and system considering element fault randomness |
| CN111628492A (en) * | 2020-04-13 | 2020-09-04 | 四川大学 | Power grid blocking management and control method with cooperation of high-voltage distribution network partition reconstruction and energy storage |
| CN111951126A (en) * | 2020-08-14 | 2020-11-17 | 天津大学 | Multi-stage power supply recovery method for active power distribution network with flexible multi-state switch |
| CN112434905A (en) * | 2020-10-26 | 2021-03-02 | 天津大学 | Power distribution system power supply capacity evaluation method considering influence of multiple power transfer on reliability |
| CN112491037A (en) * | 2020-11-09 | 2021-03-12 | 四川大学 | Multi-target multi-stage dynamic reconstruction method and system for urban power distribution network |
| CN113013869A (en) * | 2020-11-03 | 2021-06-22 | 国网浙江省电力有限公司 | Active power distribution network four-terminal soft switch planning method based on reliability evaluation |
| CN113779902A (en) * | 2021-09-09 | 2021-12-10 | 广东电网有限责任公司 | Method, device and equipment for determining reliability of circuit and storage medium |
| CN113793039A (en) * | 2021-09-17 | 2021-12-14 | 天津大学合肥创新发展研究院 | Medium and low voltage distribution network reliability assessment method considering multi-type terminals |
| CN114117795A (en) * | 2021-11-29 | 2022-03-01 | 南通大学 | Distribution network reliability evaluation method based on load-power supply connectivity analysis |
| CN114629125A (en) * | 2022-02-21 | 2022-06-14 | 华能浙江能源销售有限责任公司 | Flexible soft switch optimal configuration method, system, electronic equipment and storage medium |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103995921A (en) * | 2014-04-22 | 2014-08-20 | 广东电网公司电力科学研究院 | Method for simulating and assessing micro-grid power supply system reliability |
| CN107611966A (en) * | 2017-09-20 | 2018-01-19 | 天津大学 | A kind of active power distribution network evaluation of power supply capability method for considering difference reliability |
| CN107871202A (en) * | 2017-09-14 | 2018-04-03 | 国网浙江省电力公司经济技术研究院 | A kind of system adequacy evaluation method of meter and multi-voltage grade |
-
2018
- 2018-12-24 CN CN201811579251.4A patent/CN109447847A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103995921A (en) * | 2014-04-22 | 2014-08-20 | 广东电网公司电力科学研究院 | Method for simulating and assessing micro-grid power supply system reliability |
| CN107871202A (en) * | 2017-09-14 | 2018-04-03 | 国网浙江省电力公司经济技术研究院 | A kind of system adequacy evaluation method of meter and multi-voltage grade |
| CN107611966A (en) * | 2017-09-20 | 2018-01-19 | 天津大学 | A kind of active power distribution network evaluation of power supply capability method for considering difference reliability |
Non-Patent Citations (2)
| Title |
|---|
| 徐栎: "面向可靠性的含分布式电源配电***相关问题研究", 《中国博士学位论文全文数据库 工程科技Ⅱ辑》 * |
| 葛少云 等: "基于多层次协同分析的高中压配电网可靠性评估", 《电工技术学报》 * |
Cited By (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110994595A (en) * | 2019-11-25 | 2020-04-10 | 广东电网有限责任公司 | Power grid key equipment heavy load and out-of-limit distribution monitoring method |
| CN111030068A (en) * | 2019-12-27 | 2020-04-17 | 国电南瑞科技股份有限公司 | Power distribution network fault handling method |
| CN111030068B (en) * | 2019-12-27 | 2021-11-19 | 国电南瑞科技股份有限公司 | Power distribution network fault handling method |
| CN111404267A (en) * | 2020-02-24 | 2020-07-10 | 中国科学院电工研究所 | Multi-station integrated structure and control method thereof |
| CN111428377A (en) * | 2020-03-31 | 2020-07-17 | 国网西藏电力有限公司拉萨供电公司 | Power distribution network reliability evaluation method and system considering element fault randomness |
| CN111428377B (en) * | 2020-03-31 | 2023-06-06 | 国网西藏电力有限公司拉萨供电公司 | Power distribution network reliability evaluation method and system considering element fault randomness |
| CN111628492A (en) * | 2020-04-13 | 2020-09-04 | 四川大学 | Power grid blocking management and control method with cooperation of high-voltage distribution network partition reconstruction and energy storage |
| CN111951126B (en) * | 2020-08-14 | 2022-04-19 | 天津大学 | Multi-stage power supply recovery method for active power distribution network with flexible multi-state switch |
| CN111951126A (en) * | 2020-08-14 | 2020-11-17 | 天津大学 | Multi-stage power supply recovery method for active power distribution network with flexible multi-state switch |
| CN112434905A (en) * | 2020-10-26 | 2021-03-02 | 天津大学 | Power distribution system power supply capacity evaluation method considering influence of multiple power transfer on reliability |
| CN113013869A (en) * | 2020-11-03 | 2021-06-22 | 国网浙江省电力有限公司 | Active power distribution network four-terminal soft switch planning method based on reliability evaluation |
| CN113013869B (en) * | 2020-11-03 | 2022-02-22 | 国网浙江省电力有限公司 | Active power distribution network four-terminal soft switch planning method based on reliability evaluation |
| CN112491037A (en) * | 2020-11-09 | 2021-03-12 | 四川大学 | Multi-target multi-stage dynamic reconstruction method and system for urban power distribution network |
| CN113779902A (en) * | 2021-09-09 | 2021-12-10 | 广东电网有限责任公司 | Method, device and equipment for determining reliability of circuit and storage medium |
| CN113793039A (en) * | 2021-09-17 | 2021-12-14 | 天津大学合肥创新发展研究院 | Medium and low voltage distribution network reliability assessment method considering multi-type terminals |
| CN113793039B (en) * | 2021-09-17 | 2023-07-18 | 天津大学合肥创新发展研究院 | Reliability evaluation method for medium-low voltage distribution network considering multiple types of terminals |
| CN114117795A (en) * | 2021-11-29 | 2022-03-01 | 南通大学 | Distribution network reliability evaluation method based on load-power supply connectivity analysis |
| CN114629125A (en) * | 2022-02-21 | 2022-06-14 | 华能浙江能源销售有限责任公司 | Flexible soft switch optimal configuration method, system, electronic equipment and storage medium |
| CN114629125B (en) * | 2022-02-21 | 2024-05-03 | 华能浙江能源销售有限责任公司 | Flexible soft switch optimal configuration method, system, electronic equipment and storage medium |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109447847A (en) | A kind of active power distribution network Reliability Estimation Method containing flexible Sofe Switch | |
| Kavousi-Fard et al. | Optimal distribution feeder reconfiguration for reliability improvement considering uncertainty | |
| CN104578427B (en) | Fault self-healing method for power distribution network containing microgrid power source | |
| CN109149555B (en) | Power distribution network generalized power transformation credible capacity evaluation method considering power supply mode | |
| CN109066659B (en) | Microgrid island operation reliability assessment method and terminal equipment | |
| CN108462210B (en) | Photovoltaic open capacity calculation method based on data mining | |
| CN109378815A (en) | A kind of closed loop network turns method for controlling power supply, device and equipment | |
| CN102570450B (en) | Static reliability assessment method for complex power grid | |
| CN110854891B (en) | Power distribution network pre-disaster resource allocation method and system | |
| WO2023005113A1 (en) | Reliability analysis method for power distribution system having micro-grid on the basis of path description | |
| CN104505825A (en) | Power supply safety diagnosis analysis method for high voltage distribution network | |
| CN104123684A (en) | Power distribution network economy reconstructing method considering network loss and reliability | |
| CN104112076A (en) | Fuzzy mathematics based operational risk assessment method and fuzzy mathematics based operational risk assessment system | |
| CN105893714B (en) | Based on the detection of automatic voltage control system closed loop and appraisal procedure under Bulk power system simulation system | |
| Lata et al. | TLBO‐based approach to optimally place and sizing of energy storage system for reliability enhancement of radial distribution system | |
| CN109066612A (en) | The switching overvoltage calculation method combined based on electromechanical transient and electro-magnetic transient | |
| CN103886514B (en) | Power grid development assessment method with economical efficiency and security considered | |
| CN104993466A (en) | Cascading fault fast dynamic simulation method applicable to alternating current-direct current power grid | |
| Zand et al. | Optimal coordination of DOCRs in microgrid via contingency reduction mechanism and clustering algorithms considering various network topologies based on N-2 contingencies | |
| CN107086565B (en) | Expected accident automatic selection method based on aggregation theory | |
| CN115292869A (en) | Diamond-type power distribution network reliability calculation method considering large-scale photovoltaic energy storage access | |
| CN114678866A (en) | Power transmission line load transfer control method based on regulation cloud | |
| CN114243754A (en) | Adaptive grid-connected and off-grid energy storage response control method and control system | |
| CN108736483B (en) | Method and system for determining power grid operation mode | |
| CN111507605A (en) | Power distribution network construction benefit evaluation method and system and computer equipment |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20190308 |
|
| RJ01 | Rejection of invention patent application after publication |