CN116431961A - Real-time calculation method for wave impedance of direct current line of flexible direct current power grid - Google Patents
Real-time calculation method for wave impedance of direct current line of flexible direct current power grid Download PDFInfo
- Publication number
- CN116431961A CN116431961A CN202310420382.2A CN202310420382A CN116431961A CN 116431961 A CN116431961 A CN 116431961A CN 202310420382 A CN202310420382 A CN 202310420382A CN 116431961 A CN116431961 A CN 116431961A
- Authority
- CN
- China
- Prior art keywords
- fault
- direct current
- mode
- line
- voltage
- 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.)
- Granted
Links
- 238000004364 calculation method Methods 0.000 title description 6
- 238000000034 method Methods 0.000 claims abstract description 33
- 230000010354 integration Effects 0.000 claims description 9
- 230000008859 change Effects 0.000 claims description 7
- 239000011159 matrix material Substances 0.000 claims description 4
- 238000012546 transfer Methods 0.000 description 13
- 238000005070 sampling Methods 0.000 description 8
- 230000007704 transition Effects 0.000 description 6
- 238000004088 simulation Methods 0.000 description 3
- 230000001052 transient effect Effects 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000005404 monopole Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/04—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant in circuits having distributed constants, e.g. having very long conductors or involving high frequencies
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
- G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
- G06F17/12—Simultaneous equations, e.g. systems of linear equations
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Mathematical Physics (AREA)
- Theoretical Computer Science (AREA)
- Mathematical Optimization (AREA)
- Pure & Applied Mathematics (AREA)
- Mathematical Analysis (AREA)
- Business, Economics & Management (AREA)
- Computational Mathematics (AREA)
- Data Mining & Analysis (AREA)
- Health & Medical Sciences (AREA)
- Economics (AREA)
- Water Supply & Treatment (AREA)
- General Health & Medical Sciences (AREA)
- Operations Research (AREA)
- General Engineering & Computer Science (AREA)
- Software Systems (AREA)
- Public Health (AREA)
- Databases & Information Systems (AREA)
- Algebra (AREA)
- Human Resources & Organizations (AREA)
- Marketing (AREA)
- Primary Health Care (AREA)
- Strategic Management (AREA)
- Tourism & Hospitality (AREA)
- General Business, Economics & Management (AREA)
- Locating Faults (AREA)
Abstract
The invention relates to the technical field of fault protection after a direct current line of a flexible direct current power grid has faults, in particular to a method for calculating the wave impedance of the direct current line of the flexible direct current power grid in real time. The invention uses the relation between the line mode fault voltage, current and line mode wave impedance on the same direct current bus non-fault line signal measuring point, and writes into discrete form to obtain the overdetermined equation set. And similarly, writing the relation between the zero-mode fault voltage, the zero-mode fault current and the zero-mode wave impedance at the non-fault line signal measuring point on the same direct current bus into an overdetermined equation set in a discrete form. And solving an overdetermined equation set by using a least square method to obtain the parameter information of the linear mode wave impedance and the zero mode wave impedance. According to the invention, a new and more accurate numerical value can be obtained through recalculating according to each fault signal, the dynamic self-adaption is realized, and the accuracy can be improved.
Description
Technical Field
The invention relates to the technical field of fault protection after a direct current line of a flexible direct current power grid has faults, in particular to a method for calculating the wave impedance of the direct current line of the flexible direct current power grid in real time.
Background
The future new power system will take new energy (solar energy, wind energy, etc.) as main body. The new energy has the characteristic of randomness, and how to efficiently connect the renewable energy with large scale and high permeability into the power grid is an urgent problem. The flexible direct current (flexible direct current) power grid is based on a voltage source converter (voltage source converter, VSC), has the advantages of low power supply requirement, no commutation failure, active and reactive decoupling control and the like, and is one of important technical means for solving the problem of accessing new energy sources with volatility into the power grid. The modularized multi-level converter (modular multilevel converter, MMC) technology improves the voltage grade of a flexible direct current system, reduces the operation loss, and rapidly occurs in recent years, and the recently established demonstration engineering in China is represented by a North-Beijing + -500 kV four-terminal flexible direct current power grid, a Xiamen + -320 kV two-terminal flexible direct current system, a Nana-Australian three-terminal flexible system and the like. However, since MMCs employ a semiconductor device that can be turned off, on the one hand, the capability of overcurrent is weak. On the other hand, after the direct current circuit fails, the MMC is equivalent to the equivalent capacitor discharging to the failure point through the equivalent inductance before the sub-module is locked, the failure loop impedance is small, the failure current will quickly exceed the rated value of the semiconductor device, and the current high-performance direct current circuit breaker (DC circuit breaker, DCCB) is expensive and the technology is not mature, so the direct current circuit failure protection problem of the flexible direct current power grid is the bottleneck for preventing the further development of the flexible direct current power grid.
Because the flexible direct current power grid has extremely high requirements on line protection speed, the main protection is required to be designed based on single-ended transient quantity. However, protection based on single-ended transients may produce false identification in complex and varying fault conditions, and methods that utilize the properties of line protection boundary current limiting reactors (Fault current limiting reactor, FCLR) based on voltage change rates, etc. have difficulty in efficiently identifying high-resistance faults. In order to improve the accuracy of single-end fault identification, most methods need to accurately acquire the wave impedance of the direct current line, and estimate the parameter information of the fault by adopting methods such as parameter estimation to improve the reliability of single-end fault protection, for example, the wave impedance of the line must be used when calculating the reverse voltage traveling wave or the reverse current traveling wave. The existing method generally assumes that the wave impedance of the line is a known quantity (a constant), or the wave impedance of the line is measured in an off-line mode, but the mode is time-consuming and labor-consuming, not simple enough, and cannot be dynamically and self-adjusted according to the actual fault condition. In a practical environment, a large error occurs because the line wave impedance fluctuates with the values of specific fault conditions.
On the basis of deriving a transient traveling wave transfer function of a fault of a flexible direct current power grid, the invention discovers that the ratio of line mode fault voltage to line mode fault current of a non-fault line of the same direct current bus is line mode wave impedance, the ratio of zero mode fault voltage to zero mode fault current is zero mode wave impedance, and accordingly provides a method for solving the wave impedance of the direct current line of the flexible direct current power grid by using a least square method, and can accurately acquire wave impedance parameter information of the line in real time according to fault conditions.
Disclosure of Invention
The invention aims to solve the defects in the prior art, and provides a method for calculating the wave impedance of the direct current line of a flexible direct current power grid in real time, which utilizes a real-time fault signal and a least square method to solve the wave impedance of the direct current line of the flexible direct current power grid, can accurately and simply acquire the wave impedance parameter information of the direct current line under the current fault condition, and can be used as a basis for designing single-end quantity main protection with higher reliability.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a method for calculating the wave impedance of a direct current line of a flexible direct current power grid in real time comprises the following specific steps:
firstly, detecting the pole voltage and the pole current on a signal measuring point of a flexible direct current power grid in real time, and acquiring and recording the positive and negative pole voltages U on a non-fault line signal measuring point on the same direct current bus through a starting criterion and a direction criterion hP (t)、U hP (t) and Pole Current I hP (t)、I hN (t)；
Secondly, obtaining a fault component by making a difference between the measured value and the steady-state value, and decoupling the fault component by utilizing a pole mode decoupling matrix to obtain a line mode fault voltage and current and a zero mode fault voltage and current, namely:
then, the relation between the line mode fault voltage, the line mode fault current and the line mode wave impedance on the same direct current bus non-fault line signal measuring point is utilized, and is written into a discrete form, so as to obtain an overdetermined equation set, namely:
ΔI h1 ·Z c1 ＝ΔU h1
wherein:
similarly, the relation between the zero-mode fault voltage, the zero-mode fault current and the zero-mode wave impedance at the non-fault line signal measuring point on the same direct current bus is written into an overdetermined equation set in a discrete form, namely:
ΔI h0 ·Z c0 ＝ΔU h0
wherein:
the new and more accurate overdetermined equation set is obtained by recalculating according to each fault signal in real time, and the dynamic self-adaption is achieved;
finally, solving an overdetermined equation set by using a least square method to obtain parameter information of the linear mode wave impedance and the zero mode wave impedance, namely:
Z c1 ＝(ΔI h1 T ·ΔI h1 ) -1 ·ΔI h1 T ·ΔU h1
Z c0 ＝(ΔI h0 T ·ΔI h0 ) -1 ·ΔI h0 T ·ΔU h0
thus, it is calculated thatSelf-impedance Z to DC line s ＝(Z c0 +Z c1 ) /2 and trans-impedance Z m ＝(Z c0 -Z c1 )/2。
Preferably, the starting criterion can be a low-voltage criterion, a current change rate criterion, a voltage change rate criterion and the like, and the starting criterion is used for distinguishing a normal operation state from a disturbance state; the direction criteria can be polarity of voltage on FCLR, positive and negative of fault current integration, ratio of reverse line mode fault voltage integration to forward line mode fault voltage integration, time difference between reverse line mode voltage and forward line mode voltage reaching a port, and the like, and the direction criteria are used for distinguishing fault lines and non-fault lines on the same direct current bus. Where it is required to obtain the voltage and current of the non-faulty wire on the same dc bus.
Preferably, the measured values of the pole voltage and the pole current are values measured in real time by a voltage sensor and a current sensor; the steady state value is a value obtained by measuring a sensor when the starting criterion meets the normal operation of the system at the first M moments, wherein M is more than 1; after the fault component is obtained, a polar mode decoupling method is utilized to decouple to obtain a linear mode component and a zero mode component, and the linear mode component and the zero mode component are respectively solved. The number n of the non-fault lines on the same direct current bus is more than or equal to 1, and the cable lines or overhead lines with different lengths are applicable to flexible direct current power grids with various forms.
By adopting the technical scheme: and according to the deduction conclusion, the ratio of the line mode fault voltage to the line mode fault current of the direct current bus non-fault line is the line mode wave impedance. The conclusion is established for any sampling time, the result is written into a discrete form, a set of overdetermined equation sets can be obtained, and the overdetermined equation sets are solved through a least square method to obtain the linear mode wave impedance. Similarly, the ratio of zero-mode fault voltage to zero-mode fault current of the same direct current bus non-fault line is zero-mode wave impedance. For any sampling time, the relation is established, a set of overdetermined equation sets is obtained by writing the relation into a discrete form, and zero-mode wave impedance is obtained by solving the overdetermined equation sets through a least square method. Finally, the self-impedance and the transimpedance of the direct current line can be obtained by using the obtained linear-mode impedance and zero-mode impedance.
Compared with the prior art, the invention has the following beneficial effects:
1. the method is simple and easy to realize, is applicable to any line fault, has strong repeatability, and can verify the calculation accuracy by taking the calculation results of multiple cases.
2. According to the invention, a new and more accurate line wave impedance value can be obtained through recalculation in real time according to the signal of the specific fault, the small value difference of the line wave impedance caused by the difference of the signal is eliminated, the dynamic self-adaption is realized, and the accuracy of a value result can be improved.
3. The method solves the overdetermined equation set through the least square method, greatly improves the accuracy of the line wave impedance obtained by solving, has stronger anti-interference capability, can be used as a basis for designing single-end quantity main protection with higher reliability, and has higher application prospect.
Drawings
Fig. 1 is a flexible dc grid topology according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram after a dc line fault in an embodiment of the present invention;
FIG. 3 is a flow chart of the present invention;
fig. 4 is a graph showing the results of simulation verification according to an embodiment of the present invention.
Detailed Description
The following technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus the protection scope of the present invention is more clearly defined. The described embodiments of the present invention are intended to be only a few, but not all embodiments of the present invention, and all other embodiments that may be made by one of ordinary skill in the art without inventive faculty are intended to be within the scope of the present invention.
The specific embodiment of the invention provides a calculation method of line wave impedance aiming at a flexible direct current power grid with four ends of annular +/-500 kV, as shown in figure 1, the topology is from the simplified Zhang Bei-Beijing flexible direct current power grid actual engineering, takes a shape of a Chinese character 'kou', and adopts a true bipolar and metal reflux wiring mode. The direct current lines are overhead lines, and the lengths of the lines are shown in fig. 1. In a specific embodiment, the non-faulty wire on the same dc bus is n=1. The method is applicable to various flexible direct current power grids, such as monopole wiring, pseudo-dipole wiring, true dipole wiring, cable lines with n being more than or equal to 1 and different lengths or overhead lines. F of the DC link 12 in FIG. 1 1 After the position has positive electrode ground fault, the transition resistance is R f 。
In the specific embodiment of the invention, taking the direct current bus 1 as an example, R12 is the signal measuring point of the fault line port and is distant from the fault point F 1 And R14 is the signal measurement point of the non-fault line port on the same DC bus.
Using the superposition theorem, etc., one can obtain the graph of FIG. 1 at F 1 An equivalent circuit diagram of the fault append state after the position fault is shown in fig. 2. In fig. 2, the line adopts a dyvenin equivalent frequency dependent model, and the equivalent impedance of the MMC converter is:
wherein: l (L) eq And C eq The equivalent reactance and the equivalent capacitance of the MMC before the locking of the submodule are respectively shown. Equivalent impedance Z for the converter station 1 t1 Equivalent impedance for the converter station 2 is Z t2 . Line mode wave impedance of direct current transmission line is Z c1 Zero mode impedance Z c0 Solving the equivalent circuit shown in fig. 2 by laplace transform or the like can obtain a fault voltage transfer function as follows:
wherein: u (U) b1-tf As a transfer function of the fault voltage of the upper line mode of the direct current bus 1, deltaU b1 Is the line mode fault voltage delta U on the direct current bus 1 s To consider the equivalent voltage of the fault point after the traveling wave is refracted and reflected for a plurality of times, H 1(d) The transfer function is the transfer function of the linear-mode traveling wave when the transfer distance d is long, and L is the size of FCLR of the line outlet of the converter station 1. U (U) h1-tf Transfer function of line mode fault voltage for R14 position of non-fault line signal measuring point of DC bus 1, deltaU h1 The line mode fault voltage at the position of the point R14 is measured for the direct current bus 1 non-fault line signal.
Similarly, the fault current transfer function at different locations can be obtained as:
wherein: i c1-tf Transfer function of fault current of 1-line mode of MMC flowing to DC bus, delta I c1 Line mode fault current for MMC to flow to DC bus 1, I h1-tf Transfer function of line mode fault current at position R14 of non-fault line signal measuring point of direct current bus 1, delta I h1 The line mode fault current at the position of the point R14 is measured for the direct current bus 1 non-fault line signal.
From the transfer functions of the positions of the non-faulty line signal measurement points R14 on the dc bus 1 of equations (2) and (3), it is possible to obtain:
as is clear from the equation (4), the ratio of the line mode fault voltage to the line mode fault current at the R14 position is the line mode wave impedance. For the zero-mode component, the same can be done:
wherein: u (U) h0-tf As a transfer function of zero-mode fault voltage at the position of a non-fault line signal measuring point R14 on the direct current bus 1, deltaU h0 Zero-mode fault voltage at R14 position of non-fault line signal measuring point of direct current bus 1, I h0-tf Transfer function of zero-mode fault current at position of non-fault line signal measuring point R14 of direct current bus 1, delta I h0 The zero-mode fault current at the position of the point R14 is measured for the direct current bus 1 non-fault line signal.
Equations (4) and (5) are established at any sampling time after a failure, and thus can be written in discrete form. Formula (4) is written in discrete form as:
wherein: k is the starting sampling time satisfying the starting criterion, and N is the total sampling data length for calculating the wave impedance. Equation (6) is a set of overdetermined equations written in matrix form as:
ΔI h1 ·Z c1 ＝ΔU h1 (7)
wherein:
for the overdetermined equation set of the formula (7), the invention adopts a least square method to solve, and the linear mode wave impedance can be obtained by solving as follows:
Z c1 ＝(ΔI h1 T ·ΔI h1 ) -1 ·ΔI h1 T ·ΔU h1 (8)
similarly, the zero mode impedance can be obtained by a least square method by solving:
Z c0 ＝(ΔI h0 T ·ΔI h0 ) -1 ·ΔI h0 T ·ΔU h0 (9)
wherein:
therefore, the line wave impedance can be obtained by obtaining the fault voltage and the fault current of the non-fault line on the same direct current bus after the direct current line breaks down. Notably, this solution process can be followed byThe method is obtained by solving in real time according to the fault condition, has good dynamic self-adaption, and can dynamically adapt to different line fault states.
Finally, the self-impedance Z of the direct current circuit is obtained through calculation s ＝(Z c0 +Z c1 ) /2 and trans-impedance Z m ＝(Z c0 -Z c1 )/2。
From the above derivation, a specific flowchart for calculating line wave impedance according to a specific embodiment of the present invention is shown in fig. 3. Firstly, whether the system is abnormal or not is detected by using a starting criterion, and the starting criterion is used for distinguishing the normal operation state and the abnormal state of the system. The starting criterion can be a common low-voltage criterion, a voltage change rate criterion, a voltage gradient criterion, a current change rate criterion and the like. After the starting criterion is met, recording a sampling time k meeting the starting criterion, and recording fault data with the data length of N. The data length N may preferably take a value of 0.2ms to 1.5ms. Meanwhile, the fault line and the non-fault line on the direct current bus are judged by using direction criteria, wherein the direction criteria can be the polarity of voltage on the FCLR, the positive and negative of fault current integration, the ratio of reverse line mode fault voltage integration to forward line mode fault voltage integration, the time difference between reverse line mode voltage and forward line mode voltage reaching a port and the like. For the reverse fault, namely the non-fault line on the same direct current bus, the fault voltage and the fault current have a specific relation. Subtracting a steady-state operation value from a pole voltage and a pole current obtained by measuring a non-fault line port on the same direct current bus to obtain a fault component, namely:
Δm(t)＝m(t)-m(k-1) (10)
wherein: m may be the positive voltage U hP (t) and current I hP (t), negative electrode voltage U hN (t) and current I hN (t), M (k-M) is the sampling value at the moment M before meeting the starting criterion, M>1. And (3) performing pole mode decoupling on fault components of the positive pole and the negative pole, namely:
thereby obtaining the line mode fault voltage, current and zero mode fault electricityVoltage and current. Writing the decoupled fault components into a matrix form according to formulas (7) and (9) to obtain delta U h1 、ΔU h0 、ΔI h1 And DeltaI h0 . In the method (7) and (9), the linear mode wave impedance Z is obtained by solving an overdetermined equation set by a least square method c1 And zero mode impedance Z c0 。
In order to verify the effectiveness and performance of the specific embodiment of the invention, a four-terminal +/-500 kV flexible direct-current power grid shown in figure 1 is built in electromagnetic transient simulation software PSCAD/EMTDC, a detailed equivalent model with locking capability is adopted by MMC, a phase-domain frequency-dependent model is adopted by a direct-current power transmission line, a direct-current voltage is controlled by a converter station 1, and active power is controlled by other stations. Simulation of F on line 12 1 The position generates the grounding fault of the positive electrode passing through different transition resistances, and the transition resistance R f The fault distances d are respectively 12km, 30km, 60km, 100km, 150km and 180km. At a sampling rate of 100kHz, the calculated line mode fault voltage delta U is measured and calculated at the non-fault line port R14 of the same direct current bus h1 And line mode fault current ΔI h1 The linear mode impedance is calculated by using the flow chart shown in fig. 3, and the simulation result is shown in fig. 4. In fig. 4, the magnitude of the wave impedance is calculated taking a data length of 0.5ms, i.e., n=50. As can be seen from fig. 4, the transition resistance R f When=0.01, the calculated linear mode wave impedance Z c1 =247 Ω or so, the effect of the fault location on the line mode impedance is small. Transition resistance R f Has influence on the magnitude of the linear mode wave impedance and the transition resistance R f The larger the calculated value of the line mode wave impedance is, the larger the calculated value is. The wave impedance value is affected by the fault signals to generate small difference, and the wave impedance measuring method provided by the invention can calculate a new and more accurate value in real time according to each fault signal, has dynamic self-adaptability and can improve accuracy.
In summary, the invention obtains the relation between the fault voltage and the fault current on the non-fault line signal measuring point on the direct current bus, writes into a discrete form to obtain a group of overdetermined equation sets, and obtains the line mode wave impedance and the zero mode wave impedance by a least square method.
The description and practice of the invention disclosed herein will be readily apparent to those skilled in the art, and may be modified and adapted in several ways without departing from the principles of the invention. Accordingly, modifications or improvements may be made without departing from the spirit of the invention and are also to be considered within the scope of the invention.
Claims (3)
1. A method for calculating the wave impedance of a direct current line of a flexible direct current power grid in real time is characterized by comprising the following specific steps:
firstly, detecting the pole voltage and the pole current on a signal measuring point of a flexible direct current power grid in real time, and acquiring and recording the positive and negative pole voltages U on a non-fault line signal measuring point on the same direct current bus through a starting criterion and a direction criterion hP (t)、U hP (t) and Pole Current I hP (t)、I hN (t)；
Secondly, obtaining a fault component by making a difference between the measured value and the steady-state value, and decoupling the fault component by utilizing a pole mode decoupling matrix to obtain a line mode fault voltage and current and a zero mode fault voltage and current, namely:
then, the relation between the line mode fault voltage, the line mode fault current and the line mode wave impedance on the same direct current bus non-fault line signal measuring point is utilized, and is written into a discrete form, so as to obtain an overdetermined equation set, namely:
ΔI h1 ·Z c1 ＝ΔU h1
wherein:
similarly, the relation between the zero-mode fault voltage, the zero-mode fault current and the zero-mode wave impedance at the non-fault line signal measuring point on the same direct current bus is written into an overdetermined equation set in a discrete form, namely:
ΔI h0 ·Z c0 ＝ΔU h0
wherein:
finally, solving an overdetermined equation set by using a least square method to obtain parameter information of the linear mode wave impedance and the zero mode wave impedance, namely:
Z c1 ＝(ΔI h1 T ·ΔI h1 ) -1 ·ΔI h1 T ·ΔU h1
Z c0 ＝(ΔI h0 T ·ΔI h0 ) -1 ·ΔI h0 T ·ΔU h0
thereby, the self-impedance Z of the direct current line is calculated s ＝(Z c0 +Z c1 ) /2 and trans-impedance Z m ＝(Z c0 -Z c1 )/2。
2. The method for calculating the wave impedance of the direct current circuit of the flexible direct current power grid in real time according to claim 1, wherein the starting criteria are a low-voltage criterion, a current change rate criterion and a voltage change rate criterion, and the starting criteria are used for distinguishing a normal running state and a disturbance state; the direction criteria are the polarity of the voltage on the FCLR, the positive and negative of fault current integration, the ratio of the fault voltage integration of the reverse line mode to the fault voltage integration of the forward line mode, and the time difference between the reverse line mode voltage and the forward line mode voltage reaching the port, and the direction criteria are used for distinguishing fault lines and non-fault lines on the same direct current bus.
3. The method for calculating the wave impedance of the direct current line of the flexible direct current power grid in real time according to claim 1, wherein the measured values of the pole voltage and the pole current are values obtained by measuring a voltage sensor and a current sensor in real time; the steady state value is a value obtained by measuring a sensor when the starting criterion meets the normal operation of the system at the first M moments, wherein M is more than 1; after the fault component is obtained, a polar mode decoupling method is utilized to decouple to obtain a linear mode component and a zero mode component, and the linear mode component and the zero mode component are respectively solved.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310420382.2A CN116431961B (en) | 2023-04-19 | 2023-04-19 | Real-time calculation method for wave impedance of direct current line of flexible direct current power grid |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310420382.2A CN116431961B (en) | 2023-04-19 | 2023-04-19 | Real-time calculation method for wave impedance of direct current line of flexible direct current power grid |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116431961A true CN116431961A (en) | 2023-07-14 |
| CN116431961B CN116431961B (en) | 2023-12-19 |
Family
ID=87092427
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310420382.2A Active CN116431961B (en) | 2023-04-19 | 2023-04-19 | Real-time calculation method for wave impedance of direct current line of flexible direct current power grid |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116431961B (en) |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106291113A (en) * | 2016-07-27 | 2017-01-04 | 华北电力大学（保定） | A kind of three phase line power frequency sequence impedance On-line Measuring Method |
| CN108155661A (en) * | 2018-01-30 | 2018-06-12 | 山东大学 | Consider more dc-couple degree assessment methods of direct current itself dynamic characteristic |
| CN109001589A (en) * | 2018-05-03 | 2018-12-14 | 西安理工大学 | Line parameter circuit value time-domain calculation method based on open-phase operation fault recorder data |
| CN109119977A (en) * | 2018-09-20 | 2019-01-01 | 山东大学 | Multiterminal flexible direct current power grid DC line fast protection method and system based on single ended voltage |
| US20190049497A1 (en) * | 2016-04-08 | 2019-02-14 | Abb Schweiz Ag | Islanding detection in an electrical power grid |
| CN110320436A (en) * | 2019-07-06 | 2019-10-11 | 河南理工大学 | Flexible direct current power distribution network high resistance earthing fault detection method based on color relationship classifier |
| CN110907751A (en) * | 2019-11-28 | 2020-03-24 | 国网江苏省电力有限公司电力科学研究院 | Direct-current power distribution network fault line selection method, device and system based on directional traveling waves |
| CN111130074A (en) * | 2020-01-07 | 2020-05-08 | 西安交通大学 | Direct-current transmission line ultra-high-speed protection system and method based on voltage first extreme value time |
| CN112086940A (en) * | 2020-08-21 | 2020-12-15 | 许继集团有限公司 | Rapid traveling wave protection method and device for flexible direct current transmission line |
| CN113075440A (en) * | 2021-03-29 | 2021-07-06 | 国网江苏省电力有限公司经济技术研究院 | Power grid short-circuit current calculation method containing flexible direct current transmission system |
| CN113572139A (en) * | 2021-07-12 | 2021-10-29 | 许继集团有限公司 | Flexible direct current transmission line single-end quantity fault protection method and device |
| CN115425626A (en) * | 2022-08-31 | 2022-12-02 | 国网四川省电力公司电力科学研究院 | Mixed direct-current line protection method and system based on fault voltage traveling wave compensation |
-
2023
- 2023-04-19 CN CN202310420382.2A patent/CN116431961B/en active Active
Patent Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190049497A1 (en) * | 2016-04-08 | 2019-02-14 | Abb Schweiz Ag | Islanding detection in an electrical power grid |
| CN106291113A (en) * | 2016-07-27 | 2017-01-04 | 华北电力大学（保定） | A kind of three phase line power frequency sequence impedance On-line Measuring Method |
| CN108155661A (en) * | 2018-01-30 | 2018-06-12 | 山东大学 | Consider more dc-couple degree assessment methods of direct current itself dynamic characteristic |
| CN109001589A (en) * | 2018-05-03 | 2018-12-14 | 西安理工大学 | Line parameter circuit value time-domain calculation method based on open-phase operation fault recorder data |
| CN109119977A (en) * | 2018-09-20 | 2019-01-01 | 山东大学 | Multiterminal flexible direct current power grid DC line fast protection method and system based on single ended voltage |
| CN110320436A (en) * | 2019-07-06 | 2019-10-11 | 河南理工大学 | Flexible direct current power distribution network high resistance earthing fault detection method based on color relationship classifier |
| CN110907751A (en) * | 2019-11-28 | 2020-03-24 | 国网江苏省电力有限公司电力科学研究院 | Direct-current power distribution network fault line selection method, device and system based on directional traveling waves |
| CN111130074A (en) * | 2020-01-07 | 2020-05-08 | 西安交通大学 | Direct-current transmission line ultra-high-speed protection system and method based on voltage first extreme value time |
| CN112086940A (en) * | 2020-08-21 | 2020-12-15 | 许继集团有限公司 | Rapid traveling wave protection method and device for flexible direct current transmission line |
| CN113075440A (en) * | 2021-03-29 | 2021-07-06 | 国网江苏省电力有限公司经济技术研究院 | Power grid short-circuit current calculation method containing flexible direct current transmission system |
| CN113572139A (en) * | 2021-07-12 | 2021-10-29 | 许继集团有限公司 | Flexible direct current transmission line single-end quantity fault protection method and device |
| CN115425626A (en) * | 2022-08-31 | 2022-12-02 | 国网四川省电力公司电力科学研究院 | Mixed direct-current line protection method and system based on fault voltage traveling wave compensation |
Non-Patent Citations (5)
| Title |
|---|
| JIANHUA YIN 等: "An online measuring method of impedance parameters of asymmetric transmission lines", 2016 12TH INTERNATIONAL CONFERENCE ON NATURAL COMPUTATION, FUZZY SYSTEMS AND KNOWLEDGE DISCOVERY, pages 2241 - 2245 * |
| 余修勇 等: "多端柔性直流电网线路故障暂态等值电路及暂态特征分析", 中国电机工程学报, pages 1 - 14 * |
| 余修勇;肖立业;林良真;邱清泉;张志丰;: "基于单端量的柔性直流电网故障识别方案", 高电压技术, no. 02, pages 440 - 447 * |
| 刘燕莹: "柔性直流输电线路故障定位方法研究", 中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑, pages 042 - 499 * |
| 鲍乐: "输电线路参数在线测量方法与应用研究", 中国优秀硕士学位论文全文数据库工程科技Ⅱ辑, pages 042 - 1342 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116431961B (en) | 2023-12-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Jia et al. | Transient current correlation based protection for DC distribution system | |
| CN109713653A (en) | The auxiliary circuit of hybrid dc circuit breaker, multiterminal flexible direct current electric network fault property identification method and system | |
| CN108957225B (en) | Direct-current distribution line single-end fault location method considering cable distribution capacitance | |
| CN111856322B (en) | Direct-current distribution network bipolar short-circuit fault accurate positioning method and device based on MMC | |
| CN111463764B (en) | Direct-current transmission line protection method based on initial voltage traveling wave frequency domain attenuation rate | |
| CN109270406B (en) | Method for calculating transition resistance based on double-end asynchronous electrical quantity | |
| Lv et al. | Voltage sag source location estimation based on optimized configuration of monitoring points | |
| CN107565549B (en) | Power system network topology analysis method based on synchronous phasor measurement | |
| CN113013850B (en) | Rapid pilot protection method and system for high-voltage direct-current line | |
| CN116431961B (en) | Real-time calculation method for wave impedance of direct current line of flexible direct current power grid | |
| CN111537832A (en) | Line fault positioning method, terminal and system for multi-terminal flexible direct current transmission system | |
| CN106786498B (en) | Master station-transformer substation data collaborative identification method and device | |
| CN112986753B (en) | Flexible direct-current power grid double-end fault location method grounded through metal return line | |
| CN114280425A (en) | Power distribution network short-circuit fault judgment method based on load end phase voltage amplitude variation | |
| CN116388178B (en) | Flexible direct current power grid fault direction criterion method based on waveform correlation coefficient | |
| CN112731240A (en) | Ground fault positioning method applied to fault indicator | |
| CN112051484A (en) | Low-voltage direct-current system single-end fault location method based on voltage balancer | |
| CN109917226A (en) | Double sampled rate distribution line fault point positioning method based on wavelet analysis | |
| CN113721115B (en) | Single-phase grounding fault positioning method for neutral point flexible grounding power distribution network | |
| Ma et al. | A new pilot protection scheme for modular multi‐level converter‐based HVDC system based on voltage matching factor | |
| Zhang et al. | A novel fault location algorithm for UHVDC transmission lines | |
| Zhang et al. | Longitudinal Protection Method for AC/DC Hybrid System Based on Measuring Current Similarity | |
| Zhang et al. | Application of transient traveling wave technology in fault location and condition monitoring of collecting line in wind farm | |
| Xiao et al. | A line fault type detection method based on optimal sample training support vector machine in MMC-HVDC transmission system | |
| CN115267474B (en) | Power converter fault diagnosis method and system based on Taylor theorem |
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 | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |