CN106018924A - Direct-current power grid bipolar short-circuit fault current calculation method - Google Patents
Direct-current power grid bipolar short-circuit fault current calculation method Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention relates to a direct-current power grid bipolar short-circuit fault current calculation method and belongs to the power transmission and distribution technical field. The objective of the invention is to solve the problem of inexistence of a specific fault current calculation method for inter-coupling of the capacitor discharge of various converters after a bipolar short-circuit fault occurs on a direct-current power grid. According to the method of the invention, based on the discharge process of the equivalent capacitors of the converters after a fault, a modular multilevel direct-current power grid is simplified into an RLC equivalent network with the fault feed current of an alternating current side ignored; and according to the characteristics of direct-current power grid nodes, the direct-current power grid nodes are divided into real station nodes and virtual station nodes. According to the technical schemes of the invention, based on Kirchhoff circuit basic principle, matrixes required by the calculation of the whole direct-current power grid bipolar short-circuit fault current are written, and the written matrixes are corrected according to the location of a fault, and fast calculation of the magnitude of fault current of all direct-current lines after a bipolar short-circuit fault occurs on any line of the direct-current power grid can be realized.
Description
Technical field
The invention belongs to power transmission and distribution technical field, particularly relate to a kind of direct current network bipolar short-circuit current calculating side
Method.
Background technology
Direct current network is one has the DC transmission network that multiple inverter is interconnected by DC line.It can be integrated
Multiple new forms of energy power supplys, and in the range of thousands of miles, electric energy be transmitted with minimum loss and maximum efficiency and divide
Join.
The development of direct current network has caused worldwide extensive attention, and the safe and reliable operation face of direct current network
Face great number of issues and challenge.Distinct issues are how direct current network processes DC side fault.Direct current network generation direct current
After the bipolar short trouble in side, the electric capacity in inverter will discharge rapidly, and owing to direct current network middle impedance is relatively low, will cause straight
Stream electrical network short circuit currents increases rapidly.If after DC Line Fault the whole current conversion station of locking and use AC circuit breaker excision exchange
Circuit, will cause whole direct current network to lose power supply, and this is that direct current network operation is not intended to see.So direct current network needs
Dc circuit breaker excises DC side faulty line, isolated DC fault.When chopper is chosen and Protection parameters adjusts, need
Want the amplitude of fault current after the bipolar short trouble of direct current network.For both-end DC transmission system, there is bipolar short trouble
After, the existing computational methods of fault current.But after there is bipolar short trouble in direct current network, inverter equivalent capacity is discharged
There is coupling, there is not direct current network the whole network fault current size after the bipolar short trouble of DC side currently for direct current network
Computational methods.After the bipolar short trouble of direct current network, on each bar circuit, fault current size can only be imitated by simulation software
Really obtain.How to calculate the fault current after the bipolar short trouble of direct current network circuit be direct current network development crucial science and
Engineering problem.
Summary of the invention
For the bipolar short trouble of the direct current network mentioned in above-mentioned background technology, and pay close attention to the current conversion station after fault occurs
Equivalent capacity discharge process, ignores the fault feed-in electric current of AC.The present invention is with the discharge loop of inverter electric capacity after fault
For point of penetration, it is RLC by modular multilevel (Modular Multilevel Converter, MMC) type direct current network abbreviation
The equivalent network of series circuit.Consider the generality of direct current network topology, according to the characteristic of node, direct current network node is divided into
Real tiny node and empty tiny node, on this basis, it then follows kirchhoff circuit ultimate principle (KCL and KVL) proposes a set of event
Barrier current calculation method.
The feature of technical scheme comprises the following steps:
Step 1: according to the characteristic of direct current network interior joint, the node in direct current network is numbered with branch road.
Step 2: according to KCL and KVL, row write do not consider fault branch direct current network start node capacitance voltage matrix,
Branch current matrix, branch node incidence matrix, resistor matrix and inductance matrix.
Step 3: according to DC Line Fault point position, revise each matrix write listed by step 2, and set up by each matrix group
The differential equation group become, utilizes direct current network steady parameter result, solves differential equation group.
The present invention passes through above three step, it is possible to solves each MMC when the bipolar short-circuit current of direct current network calculates and changes
The coupled problem of stream station equivalent capacity electric discharge, calculates for the bipolar short-circuit current of direct current network and provides effective method.
Accompanying drawing explanation
Fig. 1 is (a) MMC structure in detail and (b) MMC equivalence electric discharge rlc circuit.In figureU dcFor direct current extremely to pole tension,I dc
For DC current,R 0WithL 0It is respectively arm resistance and brachium pontis inductance.R c、L cWithC cBe respectively substitutional resistance, equivalent inductance with etc.
Value electric capacity.RFor aerial line substitutional resistance,LFor DC side equivalent inductance, comprise aerial line equivalent inductance and direct current reactor.Fig. 2
Direct current network RLC equivalent network is radiated for certain.R ci 、C ci WithL ci (in Fig. 2i=1,2,3) it is respectively MMCiSubstitutional resistance, equivalence
Electric capacity and equivalent inductance.n1、n2、n3And n4It is respectively node,R ij 、L ij It is respectively node n i 、n j Between resistance and inductance,i ij
For branch road b ij On electric current, direction is from node n i Flow to node n j (in Fig. 2i、j=1,2,3,4).Fig. 3 is fault branch b ij 's
Equivalent circuit.n0For malfunctioning node,R i0WithR j0It is respectively the resistance after fault branch updates,L i0WithL j0It is respectively fault branch
Inductance after renewal,i i0Withi j0For fault current, direction is respectively from node n i Flow to node n0With from node n j Flow to node
n0。
Detailed description of the invention
A kind of direct current network bipolar short-circuit current computational methods that the present invention relates to will be elaborated below.Should
Should be it is emphasized that the description below be merely exemplary rather than in order to limit the scope of the present invention and application thereof.
The technical problem to be solved is each matrix write by row and simplify direct current network, builds the differential equation
Group, solves and obtains direct current network the size of fault current on each circuit occurs after bipolar short trouble.The present invention uses following skill
Art scheme realizes:
The present invention is realized by following three steps:
Step 1: according to the characteristic of direct current network interior joint, the node in direct current network is numbered with branch road.
It is RLC equivalent circuit by current conversion station each in direct current network to be solved and transmission line of electricity equivalence as shown in Figure 1.And by it
In each node be divided into real tiny node and empty tiny node.Defining the node definition being joined directly together with MMC current conversion station is real tiny node, as
N in Fig. 21、n2、n3Node, definition is not directly connected to current conversion station, is only that the node playing the effect coupling DC line is
Empty tiny node, such as the n in Fig. 24Node.Each node in direct current network is numbered.Assume that direct current network hasnIndividual joint
Point,bBar branch road.WhereinNIndividual real tiny node,MIndividual empty tiny node,n=N+M.Real tiny node numbering 1 ~N, empty tiny node numberingN+1~N+M。
Step 2: according to KCL and KVL, row write do not consider fault branch direct current network start node capacitance voltage matrix,
Branch current matrix, branch node incidence matrix, resistor matrix and inductance matrix.
Branch current matrixi 0With node capacitor voltage matrixu 0Can be written as
(1)
(2)
According to KVL and VAR, the loop equation of each branch road of whole direct current network can be written as
(3)
Wherein A0For the incidence matrix of branch road Yu node, and its order isb×n, the element definition in A is as follows:
(4)
R0It isb×bThe resistor matrix on rank, matrix column represents that each bar branch road, row represent each branch current.Assume branch road b ij On
The sense of current sends out debit to consistent with branch road, and the direction of branch road determine in the calculation after do not change, then R0Follow following row
Write rule:
(1) diagonal element: diagonal element comprises this correspondence branch road whole resistance when row write KVL equation, such as: branch road b ij
Diagonal element, be 2R ij +R ci +R cj 。
(2) off-diagonal element: what off-diagonal element represented is the equivalent resistance of two branch road common points current conversion stations, but due to
The regulation of branch current positive direction, the sign calcaneus branches road sign number of off-diagonal element is relevant.If common node is all branch road and sends out a little
Or being all sink, then symbol is just；If common node is respectively point and a sink of two branch roads, then symbol is negative.With branch road
b ij As a example by the off-diagonal element being likely to occur, result is as shown in table 1, whereink,pFor non-i、jArbitrary node.
Table 1R0Matrix off-diagonal element row write rule
| Non-diagonal correspondence branch road | i ik | i ki | i kj | i jk | i pk | i kp |
| R0Interior corresponding element | R ci | -R ci | R cj | -R cj | 0 | 0 |
Owing to resistance and inductance are to occur in pairs, L0Matrix column writes rule and R0Matrix is consistent, simply changes resistance into electricity
Sense.
Step 3: according to DC Line Fault point position, revise each matrix write listed by step 2, and set up by each matrix group
The differential equation group become, utilizes direct current network steady parameter result, solves differential equation group.
Assume that fault occurs at branch road b ij On, as shown in Figure 3.The most whole direct current network nodes bynBecomen+ 1, branch road
Number bybBecomeb+ 1, failure definition node isn 0Node, branch road b ij It is updated to branch road b i0And b j0, branch resistanceR ij With branch road electricity
SenseL ij Become respectivelyR i0、R j0WithL i0、L j0。i 0It is modified toi。
(5)
By R0And L0Middle branch road b ij Deserved row and column being modified as 2 new row 2 arrange, it is consistent, more with 2.2.1 joint that element row write rule
After new, matrix is designated as RtAnd Lt.By A0Branch road b is represented in ZhenijCorresponding row is modified as 2 new row, and renewal postscript is At, exponent number
For (b+1) ×n.Formula (3) is modified to:
(6)
Equation number shown in formula (6) isb+ 1, and unknown quantity further comprises equivalent capacity voltage and the empty station joint of real tiny node
The node voltage of point, total unknown quantity isb+n+ 1, therefore also need to add capacitance voltage and just can solve with current relationship equation.Again because of
Do not comprise the differential relationship of capacitance voltage and electric current for empty tiny node, the present invention uses malfunctioning noden 0Both positive and negative polarity to void station
Empty tiny node voltage is replaced in DC line pressure drop, as shown in formula (7).
(7)
If it should be noted that when two empty tiny nodes are connected, the Article 1 circuit that should avoid replacement path process is two void
Circuit between standing.
By premultiplication A while of about formula (7) equal signtAfter bring formula (6) into, in equation, all empty tiny node voltages are replaced,
Leave outu 0In have turned into 0 whole empty tiny node voltage elements, be designated asu.Leave out AtInN+1~ N+MRow, by new matrix
It is designated as At1, exponent number be (b+1) ×N, by deleteN+1~N+MThe matrix of row composition is designated as At2, and make
(8)
(9)
Replacement due to empty tiny node, although eliminated and need not in equation to solveMIndividual empty tiny node voltage swing, but real
Border occurs in that the redundant equation of linear correlation so that R2And L2It is not non-singular matrix, causes equation to solve.
The differential equation write listed by the Article 1 circuit in walked path during empty tiny node replacement is redundant equation, by R2
And L2The row of middle these circuits of correspondence replaces with AT t2The row of the empty tiny node of middle correspondence, is designated as R and L.Simultaneously by At1Middle correspondence
The row of redundant circuit makes full 0 row into, is designated as A.Then formula (6) can be write as
(10)
NThe capacitance voltage differential equation at individual real station is expressed as follows:
(11)
Current conversion station equivalent current is replaced as follows by branch current:
(12)
And make
(13)
Simultaneous formula (10), (11), (12) and (13) can obtain correction matrix equation finally, as shown in formula (14).
(14)
According to direct current network steady parameter result, solve differential equation group (14), just can get direct current network and occur bipolar
Fault current size on each bar circuit after short trouble.
It should be noted that step 1,2 and 3 entirety are as summary of the invention, and step 1 and 2 is the basis of step 3, three steps
For organic indivisible entirety.
The above, the only present invention preferably detailed description of the invention, but protection scope of the present invention is not limited thereto,
Any those familiar with the art in the technical scope that the invention discloses, the change that can readily occur in or replacement,
All should contain within protection scope of the present invention.Therefore, protection scope of the present invention should be with scope of the claims
It is as the criterion.
Claims (2)
1. direct current network bipolar short-circuit current computational methods, is characterized in that for the bipolar short circuit of direct current network DC side
Fault, it is considered to each current conversion station equivalent capacity electric discharge coupling, it is proposed that the unified matrix of each direct current network branch-path equation
Form arranges the method write, and solves constructed differential equation group, can obtain the fault current size of each branch road of DC side；
Comprising the following steps: step 1: according to the characteristic of direct current network interior joint, dividing the node in direct current network is real station joint
Point and empty tiny node, and the node in direct current network is numbered with branch road；
Step 2: according to kirchhoff circuit theory, row write the direct current network start node capacitance voltage square not considering fault branch
Battle array, branch current matrix, branch node incidence matrix, resistor matrix and inductance matrix；
Step 3: according to DC Line Fault point position, revise each matrix write listed by step 2, and set up and be made up of each matrix
Differential equation group, in conjunction with the real tiny node capacitance voltage differential equation, utilizes direct current network steady parameter result, solves differential
Equation group.
2., based on a kind of direct current network bipolar short-circuit current computational methods described in claim 1, it is characterized in that step
1,2 and 3 entirety is as summary of the invention, and step 1 and 2 is the basis of step 3, and step 3 ensure that the bipolar short trouble of direct current network
The correctness of the calculating of electric current, three steps are organic indivisible entirety.
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Cited By (10)
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| CN107677931A (en) * | 2017-08-22 | 2018-02-09 | 华北电力大学 | A kind of fault rapid identification method based on dc current waveform Curvature varying difference |
| CN107817415A (en) * | 2017-11-10 | 2018-03-20 | 全球能源互联网研究院有限公司 | A kind of bipolar short trouble variable characteristics analysis method of converter and system |
| CN108933445A (en) * | 2018-06-28 | 2018-12-04 | 东北电力大学 | DC grid short-circuit current calculation method based on the loop method of analysis |
| CN109256970A (en) * | 2018-09-14 | 2019-01-22 | 四川大学 | MMC-MTDC transmission system monopolar grounding fault current calculation method |
| CN109378830A (en) * | 2018-12-03 | 2019-02-22 | 哈尔滨理工大学 | A kind of synchronous capacitor site selecting method based on long distance power transmission |
| CN110108986A (en) * | 2019-05-29 | 2019-08-09 | 华北电力大学 | DC grid fault current complex frequency domain calculation method |
| CN110824294A (en) * | 2019-10-18 | 2020-02-21 | 济南大学 | Flexible direct-current power distribution network bipolar short-circuit fault section identification and distance measurement method |
| CN112653172A (en) * | 2020-12-16 | 2021-04-13 | 华北电力大学 | Component analysis method for interelectrode short-circuit fault current of four-terminal annular flexible direct-current power grid |
| CN112684290A (en) * | 2020-12-16 | 2021-04-20 | 华北电力大学 | Efficient calculation method for interelectrode short-circuit fault current of flexible direct-current power grid |
| CN112994018A (en) * | 2021-03-22 | 2021-06-18 | 东北电力大学 | Transformer-free unified power flow controller based on chopping control impedor |
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Cited By (14)
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| CN107677931A (en) * | 2017-08-22 | 2018-02-09 | 华北电力大学 | A kind of fault rapid identification method based on dc current waveform Curvature varying difference |
| CN107817415A (en) * | 2017-11-10 | 2018-03-20 | 全球能源互联网研究院有限公司 | A kind of bipolar short trouble variable characteristics analysis method of converter and system |
| CN108933445A (en) * | 2018-06-28 | 2018-12-04 | 东北电力大学 | DC grid short-circuit current calculation method based on the loop method of analysis |
| CN109256970B (en) * | 2018-09-14 | 2019-11-19 | 四川大学 | MMC-MTDC transmission system monopolar grounding fault current calculation method |
| CN109256970A (en) * | 2018-09-14 | 2019-01-22 | 四川大学 | MMC-MTDC transmission system monopolar grounding fault current calculation method |
| CN109378830A (en) * | 2018-12-03 | 2019-02-22 | 哈尔滨理工大学 | A kind of synchronous capacitor site selecting method based on long distance power transmission |
| CN109378830B (en) * | 2018-12-03 | 2022-05-03 | 哈尔滨理工大学 | Synchronous phase modulator site selection method based on long-distance power transmission |
| CN110108986A (en) * | 2019-05-29 | 2019-08-09 | 华北电力大学 | DC grid fault current complex frequency domain calculation method |
| CN110824294A (en) * | 2019-10-18 | 2020-02-21 | 济南大学 | Flexible direct-current power distribution network bipolar short-circuit fault section identification and distance measurement method |
| CN112653172A (en) * | 2020-12-16 | 2021-04-13 | 华北电力大学 | Component analysis method for interelectrode short-circuit fault current of four-terminal annular flexible direct-current power grid |
| CN112684290A (en) * | 2020-12-16 | 2021-04-20 | 华北电力大学 | Efficient calculation method for interelectrode short-circuit fault current of flexible direct-current power grid |
| CN112684290B (en) * | 2020-12-16 | 2022-11-04 | 华北电力大学 | Efficient calculation method for interelectrode short-circuit fault current of flexible direct-current power grid |
| CN112994018A (en) * | 2021-03-22 | 2021-06-18 | 东北电力大学 | Transformer-free unified power flow controller based on chopping control impedor |
| CN112994018B (en) * | 2021-03-22 | 2023-02-28 | 东北电力大学 | Transformer-free unified power flow controller based on chopping control impedor |
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