CN108120878A - The D.C. resistance choosing method and system of a kind of Complicated Distribution Network complex optimum device - Google Patents
The D.C. resistance choosing method and system of a kind of Complicated Distribution Network complex optimum device Download PDFInfo
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Abstract
The invention discloses the D.C. resistance choosing methods and system of a kind of Complicated Distribution Network complex optimum device.The D.C. resistance choosing method of the present invention includes：1) equivalent circuit under positive sequence, negative phase-sequence, three sequence fundamental frequency equivalent circuit of zero sequence and the sample frequency of Complicated Distribution Network complex optimum device is built；2) fundamental frequency of fault point distribution system and positive sequence under sample frequency, negative phase-sequence, three sequence equivalent circuit of zero sequence are built；3) relational expression between fault current and D.C. resistance is calculated；4) lower limiting value of D.C. resistance is determined；5) relational expression between the electric current and D.C. resistance of trouble point sample frequency is calculated；6) upper limit value of D.C. resistance is determined；7) relation according to lower limiting value and upper limit value and between the two obtains D.C. resistance.The D.C. resistance resistance value that the present invention chooses can take into account the effective extinguishing arc of distribution system and accurate route selection, can effectively promote the control performance of complex optimum device, realize its substitution effect to arc suppression coil.
Description
Technical field
The invention belongs to flexible distribution network technology fields, and in particular to a kind of direct current of Complicated Distribution Network complex optimum device
Resistance choosing method and system.
Background technology
In recent years, many new electrical equipments based on Power Electronic Technique are appeared in power supply-distribution system, these
Nonlinear-load has non-linear and impact characteristic, not only causes the distortion of system median generatrix voltage and current waveform,
It also results in power grid busbar voltage and flickering, fluctuation and three-phase imbalance phenomenon occurs, serious pollution, shadow are caused to power supply quality
Ring the economic security operation of the electrical equipment into power grid.Voltage converter has superior control runnability, at present
It is widely used as active filter, reactive-load compensator etc., for optimizing power quality, alleviates the above problem.
With the expansion of distribution scale and the increase of cable run, the capacitance current of power distribution network severely exceeds, and neutral point is not
Earthing mode has been unable to meet the requirement of operation of power networks.Currently, 10kV power distribution networks in China have greatly used arc suppression coil
Earthing mode is to inhibit fault current.But due to the compensating action of arc suppression coil, faulty line and non-fault line during stable state
The feature of zero-sequence current may be identical, which greatly increases the difficulty of failure line selection, route selection is caused to be not allowed and to report phenomenon by mistake normal
There is generation.Meanwhile traditional grounding through arc mode automatically cannot continuously follow electrical network parameter variation most preferably to be adjusted, no
Fault residual current can be made to be in minimum state at any time.
Voltage converter under DC side Contact patch possesses residual voltage current regulation ability, makes full use of active
The equipment such as wave filter, using timesharing regulating measure, (such as during normal operation, current transformer is used for filtering optimization power quality, failure
When, it is used for extinguishing arc route selection using control means such as zero-sequence currents), power distribution network is enabled to remove the use of arc suppression coil from, and only
The function of active filter and arc suppression coil is realized with a current transformer.Possess multiple functions in the voltage-source type unsteady flow of one
Device can be described as Complicated Distribution Network complex optimum device herein.Equipment investment cost can be not only reduced, current transformer can also be utilized
Zero-sequence current rapid adjustability compensation fault current maintains its minimum state, meanwhile, utilize the hand for being analogous to " S injection methods "
Section, by injecting the voltage and current signal of certain frequency, can effectively promote route selection accuracy.
The resistance value of D.C. resistance affects the route selection accuracy effect under the extinguishing arc effect and the injection of certain frequency signal of current transformer
Fruit.Effectively to inhibit the earth current and overvoltage of singlephase earth fault moment, while take into account the lower system of certain frequency signal injection
Route selection accuracy, it is necessary to D.C. resistance resistance value carry out parameter designing.
The content of the invention
For the above problem present in current transformer D.C. resistance, the present invention provides a kind of Complicated Distribution Network complex optimum dress
The D.C. resistance choosing method put can realize effective extinguishing arc, and it is same in prescribed limit to inhibit short circuit current in single phase grounding
When meet the route selection requirement of system high accuracy, provide condition for the good control performance of complex optimum device.
For this purpose, the present invention adopts the following technical scheme that：A kind of D.C. resistance choosing of Complicated Distribution Network complex optimum device
Take method, the Complicated Distribution Network complex optimum device is transformerless mixed type MMC, the friendship of the mixed type MMC
Stream side is connected directly by AC circuit breaker and substation bus bar, intermediate without connection transformer；The anode of DC side and capacitance C1
It is connected, cathode and the capacitance C of DC side2It is connected, capacitance C1The other end and capacitance C2The other end be connected, and simultaneously and direct current
Resistance R0It is connected, D.C. resistance R0The other end be directly grounded；
The D.C. resistance choosing method includes the following steps：
1) positive sequence, negative phase-sequence, three sequence fundamental frequency equivalent circuit of zero sequence and the sampling frequency of Complicated Distribution Network complex optimum device are built
Rate fsUnder equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance；
2) n (n is integer) typical Single-phase Ground Connection Failures are chosen, build the fundamental frequency of fault point distribution system and are adopted
Sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence；
3) different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, the equivalent electricity of three sequence fundamental frequency of zero sequence
Fault current I is calculated in roadfWith D.C. resistance R0Between relational expression；
4) maximum short circuit current I is no more than based on maximum fault currentf0Principle, determine the lower limiting value R of D.C. resistancemin；
5) according to fault point sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence, trouble point is calculated
Sample frequency is fsElectric current IfsWith D.C. resistance R0Between relational expression；
6) setting resistance value R is less than based on fault ground resistancef0And it is f to flow into failure dot frequencysElectric current not less than having
Imitate the minimum current I of signalfs0Principle, determine the upper limit value R of D.C. resistancemax；
7) R obtained according to step 4)min, R that step 6) obtainsmaxAnd relation between the two, obtain D.C. resistance
R0。
As the supplement of above-mentioned D.C. resistance choosing method, in step 1),
Positive sequence fundamental frequency equivalent voltage source is e+, positive sequence fundamental frequency equivalent impedance is Z+；Negative phase-sequence fundamental frequency equivalent voltage source is 0, negative phase-sequence
Fundamental frequency equivalent impedance is Z-；Zero sequence fundamental frequency equivalent voltage source is 0, and zero sequence fundamental frequency equivalent impedance is Z0；Wherein,ω0=2 π f0, f0=50Hz；J represents imaginary part unit；
R and L is respectively bridge arm equivalent resistance and inductance；R0For D.C. resistance；CdFor capacitance C1And C2Capacitance；e+For MMC outputs
Positive sequence fundamental frequency voltages control gained by MMC according to distribution system；
Positive sequence fsFrequency equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequency equivalent voltage source is
0, negative phase-sequence fsFrequency equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence fsFrequency equivalent impedance isIts
In,ωs=2 π fs, fs=220Hz；It is defeated for MMC
The frequency gone out is fsResidual voltage, by MMC according to distribution system control gained.
As the supplement of above-mentioned D.C. resistance choosing method, in step 2),
The positive sequence fundamental frequency equivalent voltage source of fault point is k11Es+k12e+, positive sequence fundamental frequency equivalent impedance is k13+k14Z+；It is negative
Sequence fundamental frequency equivalent voltage source is 0, and positive sequence fundamental frequency equivalent impedance is k13+k14Z-；Zero sequence fundamental frequency equivalent voltage source is 0, zero sequence fundamental frequency
Equivalent impedance is k15+k16Z0；Wherein, Es be power distribution network supply voltage, k11、k12、k13、k14、k15、k16By distribution net work structure and ginseng
Number determines, is constant for specified abort situation；
Fault point positive sequence fsFrequency equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequently
Rate equivalent voltage source is 0, negative phase-sequence fsFrequency equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence
fsFrequency equivalent impedance isks1、ks2、ks3、ks4、ks5It is determined by distribution net work structure and parameter, for specified event
Hinder position, be constant.
As the supplement of above-mentioned D.C. resistance choosing method, in step 3), fault current IfWith D.C. resistance R0Between pass
It is that formula is as follows：
Wherein,k17And with distribution net work structure and ginseng
The relevant constant of number.
As the supplement of above-mentioned D.C. resistance choosing method, in step 4),
For i-th of trouble point, 1≤i≤n, in maximum short circuit current If0Limitation under, obtain D.C. resistance R0Lower limit
ValueWherein If0Take 30A,
It choosesThe value of middle maximum is D.C. resistance R0Lower limiting value Rmin,
As the supplement of above-mentioned D.C. resistance choosing method, in step 5), electric current IfsWith D.C. resistance R0Between relation
Formula is as follows：
Wherein,ks6And with distribution net work structure and ginseng
The relevant constant of number.
As the supplement of above-mentioned D.C. resistance choosing method, in step 6),
I-th of trouble point, R0Upper limit valueFor：
Wherein,It is arranged to less than the 10% of fundamental frequency rated voltage；Rf0Selection be related to device DC side effectively connect
Ground problem takes 100 Ω, Ifs0Take 1A；It choosesThe value of middle minimum is D.C. resistance R0Upper limit value Rmax,
As the supplement of above-mentioned D.C. resistance choosing method, in step 7),
If Rmax≥Rmin, then D.C. resistance R0In { Rmin, RmaxIn the range of choose；According to fault current control and route selection
R is partial in the further requirement of accuracy, selectionmaxOr Rmin；
If Rmax<Rmin, then in step 6), by reducing Rf0Calculate RmaxParameter, until meeting Rmax≥RminCondition,
By R0It is arranged to RminOr Rmax, and record corresponding Rf0.At this point, the meaning included is：In the R0Under, if ground resistance is less than
Corresponding Rf0, then route selection accuracy can be ensured, otherwise, it is necessary to which other existing selection methods participate in route selection calculating together, to protect
Demonstrate,prove route selection accuracy.
As the supplement of above-mentioned D.C. resistance choosing method, each bridge arms of mixed type MMC are by multiple submodule
Cascade forms and is serially connected with bridge arm reactor, and sub-module types have two class of HBSM and FBSM, two kinds of submodule in bridge arm
Number ratio is 1:1, the drive circuit board of submodule is powered by the capacitance voltage of submodule.
The present invention also provides a kind of D.C. resistance selecting system of Complicated Distribution Network complex optimum device, the complexity is matched somebody with somebody
Electric network synthetic optimization device is transformerless mixed type MMC；Its D.C. resistance selecting system includes：
The first construction unit of equivalent circuit：Build the positive sequence, negative phase-sequence, three sequence base of zero sequence of Complicated Distribution Network complex optimum device
Frequency equivalent circuit and sample frequency fsUnder equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance；
The second construction unit of equivalent circuit：N typical Single-phase Ground Connection Failures are chosen, build fault point distribution system
Fundamental frequency and sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence；
First relational expression computing unit：Different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, zero
Three sequence fundamental frequency equivalent circuit of sequence, is calculated fault current IfWith D.C. resistance R0Between relational expression；
D.C. resistance lower limiting value determination unit：Maximum short circuit current I is no more than based on maximum fault currentf0Principle, really
Determine the lower limiting value R of D.C. resistancemin；
Second relational expression computing unit：According to fault point sample frequency fsUnder positive sequence, negative phase-sequence, the equivalent electricity of three sequence of zero sequence
Trouble point sample frequency is calculated as f in roadsElectric current IfsWith D.C. resistance R0Between relational expression；
D.C. resistance upper limit value determination unit：Setting resistance value R is less than based on fault ground resistancef0And flow into trouble point frequency
Rate is fsElectric current be not less than useful signal minimum current Ifs0Principle, determine the upper limit value R of D.C. resistancemax；
D.C. resistance obtaining unit：According to Rmin、RmaxAnd relation between the two, obtain D.C. resistance R0。
The advantageous effects of the present invention are as follows：
(1) the D.C. resistance resistance value selected by method of the invention can take into account the effective extinguishing arc of distribution system and accurate choosing
Line can effectively promote the control performance of complex optimum device, realize its substitution effect to arc suppression coil.
(2) present invention's is versatile, suitable for the power distribution network of heterogeneous networks topological structure.
Description of the drawings
Fig. 1 is the distribution system schematic diagram of the device containing complex optimum in the embodiment of the present invention；
Fig. 2 is the flow chart of ground resistance choosing method in the embodiment of the present invention；
Fig. 3 is the equivalent model schematic diagram of mixed type MMC in the embodiment of the present invention.
Specific embodiment
In order to more specifically describe the present invention, with reference to Figure of description and specific embodiment to skill of the invention
Art scheme and its relative theory are described in detail.
Embodiment 1
The present embodiment provides a kind of D.C. resistance choosing methods of Complicated Distribution Network complex optimum device.
As shown in Figure 1, complex optimum device is using transformerless mixed type MMC, (MMC belongs to voltage converter
It is a kind of), the exchange side of mixed type MMC is connected directly by AC circuit breaker Q with substation bus bar, intermediate without connection transformer；
The anode of DC side and capacitance C1It is connected, cathode and the capacitance C of DC side2It is connected, capacitance C1The other end and capacitance C2It is another
End be connected, and simultaneously with D.C. resistance R0It is connected, D.C. resistance R0The other end be directly grounded.
Mixed type MMC uses six bridge arm structure of three-phase, and each bridge arm is made of n sub-module cascade and is serially connected with bridge arm electricity
Anti- device, wherein, submodule number n is determined by DC voltage, alternating voltage, submodule voltage and bridge arm redundancy.Each bridge
Arm includes half-bridge submodule (half-bridge sub-module, HBSM) and full-bridge submodule (full-bridge sub-
Module, FBSM) two class submodules, the number ratio of two class submodules is 1:1, the drive circuit board of submodule is by submodule
Capacitance voltage is powered.HBSM is comprising there are two IGBT (T1And T2), two anti-paralleled diode (D1And D2) and a capacitance C；
FBSM is comprising there are four IGBT (T1-T4), four anti-paralleled diode (D1-D4) and a capacitance C.
In the present invention, the selection of D.C. resistance needs to take into account the earth current inhibition of singlephase earth fault moment and f simultaneouslys
(fsGeneral be chosen for fundamental frequency N times and N+1 times of intermediate value, wherein such as 220Hz, N are integer) the lower system of frequency signal injection
Route selection accuracy, i.e. extinguishing arc and option capabilities.Therefore, it is necessary in terms of extinguishing arc and route selection two to the resistance value of D.C. resistance into
Row constraint, and then obtain suitable D.C. resistance.Fig. 2 gives the specific steps of ground resistance choosing method, is respectively：
The first step：Build positive sequence, negative phase-sequence, three sequence fundamental frequency equivalent circuit of zero sequence and the frequency f of power distribution network synthesis optimization devices
Under equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance.
Second step：Multiple typical Single-phase Ground Connection Failures are chosen, build the fundamental frequency of fault point system and frequency fsUnder
Positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence.
3rd step：Different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, three sequence fundamental frequency of zero sequence etc.
It is worth circuit, fault current I is calculatedfWith D.C. resistance R0Between relational expression.
4th step：Limits value I is no more than based on maximum fault currentf0Principle, determine the lower limiting value R of D.C. resistancemin。
5th step：According to fault point frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence, failure is calculated
Dot frequency is fsElectric current IfsWith D.C. resistance R0Between relational expression.
6th step：Setting resistance value R is less than based on fault ground resistancef0And it is f to flow into failure dot frequencysElectric current it is not small
In the minimum current I of useful signalfs0Principle, determine the upper limit value R of D.C. resistancemax。
7th step：The R obtained according to the 4th stepmin, R that the 6th step obtainsmaxAnd relation between the two, obtain direct current
Resistance R0。
In the first step, Fig. 3 gives the equivalent model of mixed type MMC, can be listed below equation
Udp-Udn=Udc (3)
isj=ijn-ijp (4)
Wherein, ujAnd isj(j=a, b, c) exchanges the alternating voltage and alternating current of outlet side, i for MMCjpAnd ijnFor j phases
Upper and lower bridge arm current, ujpAnd ujnThe output voltage for submodule group of connecting for bridge arm in j phases and lower bridge arm, UdpAnd UdnIt is straight for anode
Galvanic electricity is pressed and negative DC voltage, UdcFor direct current voltage across poles, uoFor DC side neutral point voltage, R and L are respectively bridge arm equivalent
Resistance and inductance.
It is calculated by the substitution between formula (1)-(4), following expression can be obtained：
Wherein,
J=a, b, c are substituted into above formula, can obtain tri- phase equations of abc, is utilized
The mathematical model that can obtain positive sequence, negative phase-sequence and zero sequence is：
Wherein, subscript "+", "-" and " 0 " represent positive sequence, negative phase-sequence and zero-sequence component respectively, can be seen that from Fig. 3 structures
uo=(idcp+idcn)R0 (10)
Wherein, CdFor capacitance C1And C2Capacitance.According to kirchhoff electric current theorem, flow into total current and be equal to outflow always
Electric current has
Formula (10)-(13) are substituted into formula (7)-(9), and using Fourier transformation, positive sequence, negative phase-sequence and zero sequence base can be obtained
Frequency Equivalent Model.
Wherein,ω0=2 π f0, f0=50Hz,
Positive sequence is identical with the equivalent impedance of negative phase-sequence.
Assuming that under normal operation, power distribution network synthesis optimization device only exports positive sequence voltage component, negative phase-sequence and zero sequence control
System just comes into operation after the system failure.It can so obtain：Positive sequence fundamental frequency equivalent voltage source is e+, positive sequence fundamental frequency equivalent impedance
For Z+；Negative phase-sequence fundamental frequency equivalent voltage source is 0, and negative phase-sequence fundamental frequency equivalent impedance is Z-；Zero sequence fundamental frequency equivalent voltage source is 0, zero sequence fundamental frequency
Equivalent impedance is Z0。
Similarly, complex optimum device to power distribution network injected frequency be fsZero sequence current signal when, can equally obtain frequency
Rate fsUnder Equivalent Model.
Wherein,ωs=2 π fs, fs=220Hz.
Equally, positive sequence is identical with the equivalent impedance of negative phase-sequence.
Due to fsCurrent signal is zero-sequence component, and without positive sequence power supply and negative phase-sequence power supply under the frequency, therefore can obtain：Positive sequence
fsFrequency equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequency equivalent voltage source is 0, negative phase-sequence fsFrequency
Equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence fsFrequency equivalent impedance is
In second step, typical n trouble point is chosen first, and n is integer.Since power distribution network is radial structure,
It is general to choose the exemplary positions such as feeder line head end, end, contact point.Then, for each trouble point, build the fault point is
Unite fundamental frequency equivalent circuit and fsFrequency equivalent circuit.
In building process, the Equivalent Model analogy of the complex optimum device that the first step is obtained is into transformer, distribution wire
The force devices such as road, according to existing conventional electric power analysis means, using symmetrical component method to the entire power distribution system beyond trouble point
System carries out order components decomposition computation, finally, can obtain the positive sequence fundamental frequency equivalent voltage source k of fault point11Es+k12e+, positive sequence
Fundamental frequency equivalent impedance is k13+k14Z+；Negative phase-sequence fundamental frequency equivalent voltage source is 0, and positive sequence fundamental frequency equivalent impedance is k13+k14Z-；Zero sequence base
Frequency equivalent voltage source is 0, and zero sequence fundamental frequency equivalent impedance is k15+k16Z0.Wherein, Es be power distribution network supply voltage, k11、k12、k13、
k14、k15、k16It is determined by distribution net work structure and parameter, for specified abort situation, it is believed that be constant.
Similarly, frequency f can be obtainedsUnder, each order components Equivalent Model of fault point, wherein, fault point positive sequence fsFrequently
Rate equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequency equivalent voltage source is 0, negative phase-sequence fsFrequently
Rate equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence fsFrequency equivalent impedance isks1、ks2、ks3、ks4、ks5It is determined by distribution net work structure and parameter, for specified abort situation, it is believed that be normal
Amount.
In 3rd step, singlephase earth fault resistance RfMay correspond to different resistance value sizes, for example, 0 Ω, 1 Ω, 10 Ω,
100 Ω etc..Utilize the compound sequence network equation of the single-line to ground fault proposed in existing unsymmetrical short-circuit computational methods：
With reference to the fundamental frequency Equivalent Model proposed in second step, fault current I can be calculatedfWith D.C. resistance R0It
Between relational expression.
Wherein,As it can be seen that k17And with power distribution network knot
Structure and the relevant constant of parameter.
In 4th step, from formula (22) as can be seen that except e+, RfAnd R0Three variables, remaining parameter is by distribution system rack
Structure and parameter determines, is constant.Under normal operating conditions, complex optimum device only exports positive sequence voltage e+, and e+Voltage
Amplitude is close with power distribution network ac rated voltage, therefore, in earth fault moment, e+It is a constant that can be approximately considered.From IfMeter
Formula is calculated to can be seen that in definite R0On the premise of, as fault ground resistance RfWhen=0, IfIt will obtain maximum.Fault current
IfBy factor constraints such as system overcurrent, it is impossible to which excessive, setting maximum short circuit current is If0。
Therefore, for i-th (1≤i≤n) a trouble point, in maximum short circuit current If0Limitation under, R can be obtained0Under
Limit value
It choosesThe value of middle maximum is D.C. resistance R0Lower limiting value Rmin。
In 5th step, the calculating process of the 3rd step is analogous to, according to formula (20), the compound sequence network equation of (21), with reference to
F proposed in step 2sF can be calculated in Equivalent Model under frequencysThe frequency that trouble point is flowed through under frequency is fsElectricity
Flow IfsWith D.C. resistance R0Between relational expression.
Wherein,As it can be seen that ks6And with power distribution network knot
Structure and the relevant constant of parameter.
In 6th step, from formula (25) as can be seen that removingRfAnd R0Three variables, remaining parameter is by distribution system net
Frame structure and parameter determines, is constant.After failure, complex optimum device is f by injected frequencysVoltage and current signal, make
The signal flows mostly through trouble point, so as to coordinate to improve route selection accuracy with traditional selection method.To ensure power distribution system
Phenomena such as resonance, overvoltage do not occur for system, the voltage signal of injectionIt should not be too large, general amplitude is arranged to fundamental frequency rated voltage
Less than 10%.
For faulty line is enabled effectively to monitor fsAC current frequency signal, IfsAmplitude should be greater than to be recognized
It is set to the minimum current I of useful signalfs0.Determine IfsMinimum value andMaximum, (3R can be obtainedf+3ks5R0)
Maximum.IfsIt is easily influenced by the shunting of feeder line capacitance to earth, it is assumed that the direct-to-ground capacitance parameter of a certain cable feeder line is
0.27 μ F/km, cable length 10km, then in frequency fsUnder capacitance to earth be 268 Ω.To ensure the accuracy of route selection,
Fault ground resistance Rf268 Ω cannot be necessarily more than, otherwise can cause route selection mistake.Therefore, RfIt should be less than a certain resistance value Rf0, than
Such as 100 Ω.When grounding resistance is more than Rf0When, the present invention should coordinate other existing selection methods to carry out route selection, to ensure route selection standard
Exactness.R is determinedfAfterwards, i-th of trouble point, R can be obtained0Upper limit value
It choosesThe value of middle minimum is D.C. resistance R0Upper limit value Rmax。
In 7th step, the R that is gone out by four-step calculationminThe R calculated with the 6th stepmaxParameter being related to due to the two etc. is no
Together, it is possible to can there are Rmin>RmaxSituation.If Rmax≥Rmin, then D.C. resistance R0It can be in { Rmin, RmaxIn the range of select
It takes；According to the further requirement of fault current control and route selection accuracy, may be selected to be partial to RmaxOr Rmin。
If Rmax<Rmin, then in the 6th step, by reducing Rf0Calculate RmaxParameter, until meeting Rmax≥RminCondition,
By R0It is arranged to Rmin(Rmax), and record corresponding Rf0.At this point, the meaning included is：In the R0Under, if ground resistance is small
In corresponding Rf0, then it can ensure route selection accuracy, otherwise, it is necessary to which other existing selection methods participate in route selection calculating together, with
Ensure route selection accuracy.
Embodiment 2
The present embodiment provides a kind of D.C. resistance selecting systems of Complicated Distribution Network complex optimum device.The complexity is matched somebody with somebody
Electric network synthetic optimization device is transformerless mixed type MMC, the exchange side of the mixed type MMC by AC circuit breaker with
Substation bus bar is connected directly, intermediate without connection transformer；The anode of DC side and capacitance C1It is connected, cathode and the electricity of DC side
Hold C2It is connected, capacitance C1The other end and capacitance C2The other end be connected, and simultaneously with D.C. resistance R0It is connected, D.C. resistance R0's
The other end is directly grounded.The each bridge arms of mixed type MMC are made of multiple submodule cascade and are serially connected with bridge arm reactance
Device, sub-module types have two class of HBSM and FBSM in bridge arm, and two kinds of submodule number ratio is 1:1, the driving of submodule
Circuit board is powered by the capacitance voltage of submodule.
The D.C. resistance selecting system includes：
The first construction unit of equivalent circuit：Build the positive sequence, negative phase-sequence, three sequence base of zero sequence of Complicated Distribution Network complex optimum device
Frequency equivalent circuit and sample frequency fsUnder equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance；
The second construction unit of equivalent circuit：N typical Single-phase Ground Connection Failures are chosen, build fault point distribution system
Fundamental frequency and sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence；
First relational expression computing unit：Different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, zero
Three sequence fundamental frequency equivalent circuit of sequence, is calculated fault current IfWith D.C. resistance R0Between relational expression；
D.C. resistance lower limiting value determination unit：Maximum short circuit current I is no more than based on maximum fault currentf0Principle, really
Determine the lower limiting value R of D.C. resistancemin；
Second relational expression computing unit：According to fault point sample frequency fsUnder positive sequence, negative phase-sequence, the equivalent electricity of three sequence of zero sequence
Trouble point sample frequency is calculated as f in roadsElectric current IfsWith D.C. resistance R0Between relational expression；
D.C. resistance upper limit value determination unit：Setting resistance value R is less than based on fault ground resistancef0And flow into trouble point frequency
Rate is fsElectric current be not less than useful signal minimum current Ifs0Principle, determine the upper limit value R of D.C. resistancemax；
D.C. resistance obtaining unit：According to Rmin、RmaxAnd relation between the two, obtain D.C. resistance R0。
It should be pointed out that for those skilled in the art, without departing from the principle of the present invention,
Can also to the present invention some improvement and modification can also be carried out, these improvement and modification also fall into the protection domain of the claims in the present invention
It is interior.
Claims (10)
1. a kind of D.C. resistance choosing method of Complicated Distribution Network complex optimum device, Complicated Distribution Network complex optimum dress
Transformerless mixed type MMC is set to, the exchange side of the mixed type MMC is direct with substation bus bar by AC circuit breaker
It is connected, it is intermediate without connection transformer；The anode of DC side and capacitance C1It is connected, cathode and the capacitance C of DC side2It is connected, capacitance C1
The other end and capacitance C2The other end be connected, and simultaneously with D.C. resistance R0It is connected, D.C. resistance R0The other end directly connect
Ground；It is characterized in that,
The D.C. resistance choosing method includes the following steps：
1) positive sequence, negative phase-sequence, three sequence fundamental frequency equivalent circuit of zero sequence and the sample frequency f of Complicated Distribution Network complex optimum device are builtsUnder
Equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance；
2) n typical Single-phase Ground Connection Failures are chosen, build the fundamental frequency of fault point distribution system and sample frequency fsUnder just
Sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence；
3) different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, three sequence fundamental frequency equivalent circuit of zero sequence, calculate
Obtain fault current IfWith D.C. resistance R0Between relational expression；
4) maximum short circuit current I is no more than based on maximum fault currentf0Principle, determine the lower limiting value R of D.C. resistancemin；
5) according to fault point sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence, failure point sampling is calculated
Frequency is fsElectric current IfsWith D.C. resistance R0Between relational expression；
6) setting resistance value R is less than based on fault ground resistancef0And it is f to flow into failure dot frequencysElectric current not less than effectively letter
Number minimum current Ifs0Principle, determine the upper limit value R of D.C. resistancemax；
7) R obtained according to step 4)min, R that step 6) obtainsmaxAnd relation between the two, obtain D.C. resistance R0。
2. D.C. resistance choosing method according to claim 1, which is characterized in that in step 1),
Positive sequence fundamental frequency equivalent voltage source is e+, positive sequence fundamental frequency equivalent impedance is Z+；Negative phase-sequence fundamental frequency equivalent voltage source is 0, negative phase-sequence fundamental frequency
Equivalent impedance is Z-；Zero sequence fundamental frequency equivalent voltage source is 0, and zero sequence fundamental frequency equivalent impedance is Z0；Wherein,ω0=2 π f0, f0=50Hz；J represents imaginary part list
Position；R and L is respectively bridge arm equivalent resistance and inductance；R0For D.C. resistance；CdFor capacitance C1And C2Capacitance；e+It is exported for MMC
Positive sequence fundamental frequency voltages, by MMC according to distribution system control gained；
Positive sequence fsFrequency equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequency equivalent voltage source is 0, is born
Sequence fsFrequency equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence fsFrequency equivalent impedance isWherein,ωs=2 π fs, fs=220Hz；For MMC outputs
Frequency is fsResidual voltage, by MMC according to distribution system control gained.
3. D.C. resistance choosing method according to claim 2, which is characterized in that in step 2),
The positive sequence fundamental frequency equivalent voltage source of fault point is k11Es+k12e+, positive sequence fundamental frequency equivalent impedance is k13+k14Z+；Negative phase-sequence base
Frequency equivalent voltage source is 0, and positive sequence fundamental frequency equivalent impedance is k13+k14Z-；Zero sequence fundamental frequency equivalent voltage source is 0, and zero sequence fundamental frequency is equivalent
Impedance is k15+k16Z0；Wherein, Es be power distribution network supply voltage, k11、k12、k13、k14、k15、k16It is determined by distribution net work structure and parameter
It is fixed, it is constant for specified abort situation；
Fault point positive sequence fsFrequency equivalent voltage source is 0, positive sequence fsFrequency equivalent impedance isNegative phase-sequence fsFrequency etc.
Threshold voltage source is 0, negative phase-sequence fsFrequency equivalent impedance isZero sequence fsFrequency equivalent voltage source isZero sequence fsFrequently
Rate equivalent impedance isks1、ks2、ks3、ks4、ks5It is determined by distribution net work structure and parameter, for specified fault bit
It puts, is constant.
4. D.C. resistance choosing method according to claim 3, which is characterized in that in step 3), fault current IfWith direct current
Resistance R0Between relational expression it is as follows：
<mrow>
<msub>
<mi>I</mi>
<mi>f</mi>
</msub>
<mo>=</mo>
<mfrac>
<mrow>
<mn>3</mn>
<mrow>
<mo>(</mo>
<msub>
<mi>k</mi>
<mn>11</mn>
</msub>
<msub>
<mi>E</mi>
<mi>s</mi>
</msub>
<mo>+</mo>
<msub>
<mi>k</mi>
<mn>12</mn>
</msub>
<msup>
<mi>e</mi>
<mo>+</mo>
</msup>
<mo>)</mo>
</mrow>
</mrow>
<mrow>
<msub>
<mi>k</mi>
<mn>17</mn>
</msub>
<mo>+</mo>
<mn>3</mn>
<msub>
<mi>R</mi>
<mi>f</mi>
</msub>
<mo>+</mo>
<mn>3</mn>
<msub>
<mi>k</mi>
<mn>16</mn>
</msub>
<msub>
<mi>R</mi>
<mn>0</mn>
</msub>
</mrow>
</mfrac>
<mo>,</mo>
</mrow>
Wherein,k17And with distribution net work structure and parameter phase
The constant of pass.
5. D.C. resistance choosing method according to claim 4, which is characterized in that in step 4),
For i-th of trouble point, 1≤i≤n, in maximum short circuit current If0Limitation under, obtain D.C. resistance R0Lower limiting valueWherein If0Take 30A,
<mrow>
<msubsup>
<mi>R</mi>
<mi>min</mi>
<mi>i</mi>
</msubsup>
<mo>=</mo>
<mfrac>
<mrow>
<mn>3</mn>
<mrow>
<mo>(</mo>
<msub>
<mi>k</mi>
<mn>11</mn>
</msub>
<msub>
<mi>E</mi>
<mi>s</mi>
</msub>
<mo>+</mo>
<msub>
<mi>k</mi>
<mn>12</mn>
</msub>
<msup>
<mi>e</mi>
<mo>+</mo>
</msup>
<mo>)</mo>
</mrow>
</mrow>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mn>16</mn>
</msub>
<msub>
<mi>I</mi>
<mrow>
<mi>f</mi>
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
<mo>-</mo>
<mfrac>
<msub>
<mi>k</mi>
<mn>17</mn>
</msub>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mn>16</mn>
</msub>
</mrow>
</mfrac>
<mo>,</mo>
</mrow>
It choosesThe value of middle maximum is D.C. resistance R0Lower limiting value Rmin,
<mrow>
<msub>
<mi>R</mi>
<mi>min</mi>
</msub>
<mo>=</mo>
<mi>m</mi>
<mi>a</mi>
<mi>x</mi>
<mo>{</mo>
<msubsup>
<mi>R</mi>
<mi>min</mi>
<mn>1</mn>
</msubsup>
<mo>,</mo>
<msubsup>
<mi>R</mi>
<mi>min</mi>
<mn>2</mn>
</msubsup>
<mo>,</mo>
<mo>...</mo>
<mo>,</mo>
<msubsup>
<mi>R</mi>
<mi>min</mi>
<mi>n</mi>
</msubsup>
<mo>}</mo>
<mo>.</mo>
</mrow>
6. D.C. resistance choosing method according to claim 5, which is characterized in that in step 5), electric current IfsWith direct current
Hinder R0Between relational expression it is as follows：
<mrow>
<msub>
<mi>I</mi>
<mrow>
<mi>f</mi>
<mi>s</mi>
</mrow>
</msub>
<mo>=</mo>
<mfrac>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>3</mn>
</mrow>
</msub>
<msubsup>
<mi>e</mi>
<mi>s</mi>
<mn>0</mn>
</msubsup>
</mrow>
<mrow>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>6</mn>
</mrow>
</msub>
<mo>+</mo>
<mn>3</mn>
<msub>
<mi>R</mi>
<mi>f</mi>
</msub>
<mo>+</mo>
<mn>3</mn>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>5</mn>
</mrow>
</msub>
<msub>
<mi>R</mi>
<mn>0</mn>
</msub>
</mrow>
</mfrac>
<mo>,</mo>
</mrow>
Wherein,ks6And with distribution net work structure and parameter phase
The constant of pass.
7. D.C. resistance choosing method according to claim 6, which is characterized in that in step 6),
I-th of trouble point, R0Upper limit valueFor：
<mrow>
<msubsup>
<mi>R</mi>
<mrow>
<mi>m</mi>
<mi>a</mi>
<mi>x</mi>
</mrow>
<mi>i</mi>
</msubsup>
<mo>=</mo>
<mfrac>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>3</mn>
</mrow>
</msub>
<msubsup>
<mi>e</mi>
<mi>s</mi>
<mn>0</mn>
</msubsup>
</mrow>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>5</mn>
</mrow>
</msub>
<msub>
<mi>I</mi>
<mrow>
<mi>f</mi>
<mi>s</mi>
<mn>0</mn>
</mrow>
</msub>
</mrow>
</mfrac>
<mo>-</mo>
<mfrac>
<mrow>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>6</mn>
</mrow>
</msub>
<mo>+</mo>
<mn>3</mn>
<msub>
<mi>R</mi>
<mrow>
<mi>f</mi>
<mn>0</mn>
</mrow>
</msub>
</mrow>
<mrow>
<mn>3</mn>
<msub>
<mi>k</mi>
<mrow>
<mi>s</mi>
<mn>5</mn>
</mrow>
</msub>
</mrow>
</mfrac>
<mo>,</mo>
</mrow>
Wherein,It is arranged to less than the 10% of fundamental frequency rated voltage；Rf0Take 100 Ω, Ifs0Take 1A；It choosesMiddle minimum
Value is D.C. resistance R0Upper limit value Rmax,
<mrow>
<msub>
<mi>R</mi>
<mi>max</mi>
</msub>
<mo>=</mo>
<mi>min</mi>
<mo>{</mo>
<msubsup>
<mi>R</mi>
<mi>max</mi>
<mn>1</mn>
</msubsup>
<mo>,</mo>
<msubsup>
<mi>R</mi>
<mi>max</mi>
<mn>2</mn>
</msubsup>
<mo>,</mo>
<mo>...</mo>
<mo>,</mo>
<msubsup>
<mi>R</mi>
<mi>max</mi>
<mi>n</mi>
</msubsup>
<mo>}</mo>
<mo>.</mo>
</mrow>
8. D.C. resistance choosing method according to claim 7, which is characterized in that in step 7),
If Rmax≥Rmin, then D.C. resistance R0In { Rmin, RmaxIn the range of choose；It is accurate according to fault current control and route selection
R is partial in the further requirement of degree, selectionmaxOr Rmin；
If Rmax<Rmin, then in step 6), by reducing Rf0Calculate RmaxParameter, until meeting Rmax≥RminCondition, by R0
It is arranged to RminOr Rmax, and record corresponding Rf0。
9. D.C. resistance choosing method according to claim 1, which is characterized in that
The each bridge arms of mixed type MMC are made of multiple submodule cascade and are serially connected with bridge arm reactor, sub in bridge arm
Module type has two class of HBSM and FBSM, and two kinds of submodule number ratio is 1:1, the drive circuit board of submodule is by submodule
The capacitance voltage power supply of block.
10. a kind of D.C. resistance selecting system of Complicated Distribution Network complex optimum device, the Complicated Distribution Network complex optimum
Device is transformerless mixed type MMC；It is characterized in that, the D.C. resistance selecting system includes：
The first construction unit of equivalent circuit：Build positive sequence, negative phase-sequence, three sequence fundamental frequency of zero sequence of Complicated Distribution Network complex optimum device etc.
It is worth circuit and sample frequency fsUnder equivalent circuit, equivalent circuit is in series by equivalent voltage source and equivalent impedance；
The second construction unit of equivalent circuit：N typical Single-phase Ground Connection Failures are chosen, build the base of fault point distribution system
Frequency and sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence；
First relational expression computing unit：Different fault ground resistance R is setf, according to fault point positive sequence, negative phase-sequence, three sequence of zero sequence
Fault current I is calculated in fundamental frequency equivalent circuitfWith D.C. resistance R0Between relational expression；
D.C. resistance lower limiting value determination unit：Maximum short circuit current I is no more than based on maximum fault currentf0Principle, determine straight
The lower limiting value R of leakage resistancemin；
Second relational expression computing unit：According to fault point sample frequency fsUnder positive sequence, negative phase-sequence, three sequence equivalent circuit of zero sequence, meter
Calculation obtains trouble point sample frequency as fsElectric current IfsWith D.C. resistance R0Between relational expression；
D.C. resistance upper limit value determination unit：Setting resistance value R is less than based on fault ground resistancef0And it flows into failure dot frequency and is
fsElectric current be not less than useful signal minimum current Ifs0Principle, determine the upper limit value R of D.C. resistancemax；
D.C. resistance obtaining unit：According to Rmin、RmaxAnd relation between the two, obtain D.C. resistance R0。
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