CN113515838A - Direct current system modeling simulation method and device, computer equipment and storage medium - Google Patents
Direct current system modeling simulation method and device, computer equipment and storage medium Download PDFInfo
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Abstract
The application relates to a direct current system modeling simulation method, a direct current system modeling simulation device, computer equipment and a storage medium. The method comprises the following steps: acquiring equivalent circuit parameters of a secondary circuit of the direct current system, and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay; respectively performing transient simulation on a direct current system ground fault and a direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result; and analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output prevention data for preventing the fault of the secondary circuit of the direct current system. The method and the device fully consider the equivalent circuit parameters of the secondary circuit of the direct current system, perfect the fault model of the direct current system, improve the accuracy of fault analysis of the secondary circuit of the direct current system, and perfect the obtained precaution data.
Description
Technical Field
The present application relates to the field of power system simulation technologies, and in particular, to a method and an apparatus for modeling and simulating a dc system, a computer device, and a storage medium.
Background
The direct current system is an important component of a transformer substation, and the main task of the direct current system is to provide power for a relay protection device, a breaker operation and various signal loops. Whether the direct current system operates normally or not is related to whether relay protection and a breaker can act correctly or not, and safe operation of a transformer substation and even the whole power grid can be influenced.
The direct current system ground fault and the alternating current-direct current series-parallel fault are the most common faults in the direct current system, at present, a simplified model is often adopted for modeling research on the direct current system, only positive and negative earth capacitance, earth resistance, relay resistance and the like of the direct current system are considered, a comprehensive simulation model of a charger, an insulation monitoring system, a secondary control cable, relay coil inductance, relay equivalent resistance, relay series resistance and the like does not exist, how to comprehensively consider modeling of the models and building a corresponding simulation model have certain research value.
However, in the implementation process, the inventor finds that at least the following problems exist in the conventional technology: the existing direct current system model is not accurate enough for analyzing the fault of the secondary loop of the direct current system.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a method, an apparatus, a computer device and a storage medium for modeling and simulating a dc system.
A direct current system modeling simulation method comprises the following steps:
acquiring equivalent circuit parameters of a secondary circuit of the direct current system, and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
respectively performing transient simulation on a direct current system ground fault and a direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result;
and analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output prevention data for preventing the fault of the secondary circuit of the direct current system.
In one embodiment, the step of processing the equivalent circuit parameters of the secondary circuit of the dc system to obtain a fault model of the dc system includes:
obtaining a charger equivalent model according to the charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and obtaining a direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
In one embodiment, the charger parameters include an equivalent reactance parameter of a storage battery transformer, a power transmission line parameter, an equivalent inductance parameter of a rectifying side, an equivalent resistance parameter of the rectifying side and an equivalent capacitance parameter of the rectifying side.
In one embodiment, the secondary cable parameters include a secondary cable dimension parameter, a secondary cable resistance unit length parameter, a secondary cable inductance unit length parameter, a secondary cable capacitance unit length parameter, and a secondary cable conductance unit length parameter;
the step of obtaining a secondary cable equivalent model based on secondary cable parameters includes:
determining the secondary parameter characteristic impedance and the secondary cable propagation constant of the secondary cable by adopting a distributed parameter model based on the unit length parameter of the secondary cable resistance, the unit length parameter of the secondary cable inductance, the unit length parameter of the secondary cable capacitance and the unit length parameter of the secondary cable conductance;
and obtaining a secondary cable equivalent model according to the secondary parameter characteristic impedance of the secondary cable, the propagation constant of the secondary cable and the size parameter of the secondary cable.
In one embodiment, the relay parameters include a relay coil resistance parameter and a relay coil inductance parameter;
the inductance parameters of the relay coil comprise the inductance at the moment when the armature starts to move towards the iron core and the inductance at the moment when the armature starts to separate from the iron core.
In one embodiment, the results of the transient simulation include: voltage change data of two ends of the relay under the direct current system ground fault and voltage change data of two ends of the relay under the direct current system series-parallel fault.
A direct current system modeling simulation device comprises:
the model establishing module is used for acquiring the equivalent circuit parameters of the secondary circuit of the direct current system and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
the processing module is used for respectively carrying out transient simulation on the direct current system ground fault and the direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result;
and the output module is used for analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output precaution data for preventing the fault of the secondary circuit of the direct current system.
In one embodiment, the model building module comprises:
the first model establishing unit is used for obtaining a charger equivalent model according to the charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and the second model establishing unit is used for obtaining a direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
A computer device comprising a memory and a processor, the memory storing a computer program, the processor implementing the steps of the method when executing the computer program.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method.
One of the above technical solutions has the following advantages and beneficial effects:
according to the method and the device, the direct current system fault model is obtained by processing the direct current system secondary circuit equivalent circuit parameters of the transformer substation, the direct current system fault model is adopted to perform transient simulation on the direct current system ground fault and the direct current system series-parallel fault respectively to obtain a transient simulation result, the fault coupling path and the relay action process are analyzed based on the transient simulation result, the precaution data are obtained and output, and therefore the precaution data are used for preventing the direct current system secondary circuit fault. The direct current system fault model is improved, simulation analysis is conducted on the direct current system ground fault and the alternating current-direct current series-parallel fault based on the direct current system fault model, accuracy of direct current system secondary circuit fault analysis is improved, and obtained prevention data are improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart diagram of a modeling simulation method for a DC system in one embodiment;
FIG. 2 is a flowchart illustrating the steps of obtaining a fault model for a DC system in one embodiment;
FIG. 3 is a schematic diagram of a dual battery charging scheme for dual batteries according to one embodiment;
FIG. 4 is a schematic diagram of a model of a charger in one embodiment;
FIG. 5 is a flowchart illustrating the steps for obtaining a secondary cable equivalent model based on secondary cable parameters in one embodiment;
FIG. 6 is a schematic diagram of the construction of a secondary cable in one embodiment;
FIG. 7 is a diagram illustrating a distributed parameter model according to an embodiment;
FIG. 8 is a schematic diagram of a fault model for the DC system in one embodiment;
FIG. 9 is a diagram illustrating results of transient simulation of a DC positive ground fault in one embodiment;
FIG. 10 is a diagram illustrating results of transient simulation of a DC negative ground fault in one embodiment;
FIG. 11 is a diagram illustrating results of a secondary loop cable ground fault transient simulation in one embodiment;
FIG. 12 is a diagram illustrating the results of transient simulation of DC positive and AC series-parallel faults in one embodiment;
FIG. 13 is a diagram illustrating transient simulation results for DC negative and AC series-parallel faults in one embodiment;
FIG. 14 is a diagram illustrating the results of a fault transient simulation for an AC-DC hybrid control loop in accordance with one embodiment;
FIG. 15 is a block diagram showing the structure of a DC system modeling simulation apparatus according to an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.
In one embodiment, as shown in fig. 1, a direct current system modeling simulation method is provided, which may include:
202, acquiring equivalent circuit parameters of a secondary circuit of the direct current system, and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
step 204, respectively performing transient simulation on the direct current system ground fault and the direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result;
and step 206, analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output prevention data for preventing the fault of the secondary circuit of the direct current system.
The direct current system is used as an operating power supply of a power plant and a transformer substation and is a power supply network with large branches and complex structures. The direct current system generally adopts a 220V or 110V direct current power supply to supply power, and the positive pole and the negative pole are not grounded. The method and the device consider real elements in the direct current system of the actual transformer substation, and perform detailed modeling equivalence on the actual elements, so that simulation is closer to the actual situation. A large number of ring networks exist in a plurality of branches of a direct current system, and the system is generally divided into the following four components: charging equipment, a battery pack, a direct current loop and a load device.
In general, the charging equipment exists as a power supply and can also float and charge a storage battery pack; the charging device generally includes a high-frequency switching power supply type device, a phase control type device, and a magnetic amplification type device. The accumulator battery is a chemical power supply, and under the condition of no fault, the charging equipment carries out floating charging on the accumulator battery, so that the impact load can obtain instantaneous large current. When the charging device fails and cannot work normally, the battery pack can temporarily supply power to the direct current system. The open type acid-proof and flame-proof storage battery used in the early period is replaced by a valve-controlled lead-acid storage battery at present, and the battery has the advantages that the open type acid-proof and flame-proof storage battery does not have, such as large energy storage, small volume, no pollution, simple maintenance and the like. In the dc circuit, since the dc system has a wide distribution of power supply objects and a long distance between them in a substation and a power plant, a complicated dc circuit is required to supply power to various loads without interruption. The direct current circuit is complex and interconnected, and is divided into various branch power supply networks which exist independently according to the functional difference of load equipment: a fault lighting power supply circuit, a protection and control power supply circuit, a signal power supply circuit, a fuse closing coil power supply circuit and the like; generally, according to different functions of loads in a transformer substation, a separate power supply network is used, so that unnecessary influence on other feeder circuits when a certain load circuit fails can be avoided. The load devices of the dc system in the substation are of two types: a control type and a power type; the control type load equipment comprises relay protection, control, measurement, automatic devices and the like; the power type load includes a closing device using a breaker electromagnetic principle, various types of direct current power, an alternating current type uninterruptible power supply device, a power source of a remote power communication device, and the like.
In addition, the ground fault is one of the most easily occurring faults in the secondary circuit of the dc system, and the ingress of the ac causes the voltage of the ac to the ground in the dc system, and thus belongs to a special dc system ground fault, i.e. a dc system series-parallel fault. In addition, due to the existence of the cable distributed capacitor and the anti-interference filter capacitor, the earth capacitance of the direct current system is not negligible, and the electric energy stored by the capacitor can be directly provided for a protective relay coil, so that a protection misoperation accident is caused.
Specifically, the method includes the steps that equivalent circuit parameters of a secondary circuit of the direct current system are obtained, the equivalent circuit parameters of the secondary circuit of the direct current system are configuration parameters of relevant elements related to the secondary circuit of the actual direct current system, and the configuration parameters include charger parameters, secondary cable parameters, relay parameters and the like; the method comprises the steps that a direct current system fault model is obtained by processing parameters of a secondary circuit equivalent circuit of a direct current system, transient simulation is respectively carried out on a direct current system ground fault and a direct current system series-parallel fault based on the direct current system fault model, namely simulation is carried out on the condition that the direct current system has faults, and a transient simulation result is obtained; and according to the transient simulation result, carrying out detailed analysis on the fault coupling path and the action process of the relay so as to obtain corresponding precautionary data, wherein the precautionary data is used for indicating corresponding precautionary measures for preventing the secondary circuit of the direct current system from generating faults. Furthermore, the precautionary data can be displayed, so that corresponding precautionary measures can be obtained more intuitively.
According to the direct current system modeling simulation method, the equivalent circuit parameters of the secondary circuit of the direct current system are obtained, the configuration parameters of related elements related to the real direct current system are considered, so that a direct current system fault model which is more appropriate to actual conditions and more complete can be established, transient simulation is respectively carried out on the direct current system ground fault and the direct current system series-parallel fault by utilizing the complete direct current system fault model in the method, a more accurate transient simulation result which is closer to the actual conditions can be obtained, and the accuracy of secondary circuit fault analysis of the direct current system can be improved based on the transient simulation result; by analyzing the transient simulation result in detail aiming at the fault coupling path and the action process of the relay, more complete prevention data for preventing the fault of the secondary circuit of the direct current system can be obtained.
In one embodiment, as shown in fig. 2, the step 202 of processing the equivalent circuit parameters of the secondary circuit of the dc system to obtain a fault model of the dc system may include:
step 302, obtaining a charger equivalent model according to charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and 304, obtaining a direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
The actual direct current system relates to configuration parameters of actual elements such as a charger, an insulation monitoring system, a secondary cable, a relay coil inductor, a relay equivalent resistor, a relay series resistor and the like, so that the direct current system secondary circuit equivalent circuit parameters can comprise charger parameters, secondary cable parameters, relay parameters and the like.
Specifically, relevant actual configuration parameters related to parameters of a secondary circuit equivalent circuit of the direct current system, such as parameters of a charger, parameters of a secondary cable, parameters of a relay and the like, are respectively constructed into corresponding equivalent models; the method comprises the steps of obtaining a charger equivalent model according to charger parameters, obtaining a secondary cable equivalent model based on secondary cable parameters, determining a relay equivalent model according to relay parameters and the like; and then obtaining the direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model, wherein the direct current system fault model is also a direct current system secondary circuit equivalent circuit model considering actual configuration parameters of the charger, the secondary cable and related elements of the relay in the actual direct current system.
Relevant parameters of actual elements such as a charger, a secondary cable and a relay in an actual direct current system are comprehensively considered, a charger equivalent model is built according to the charger parameters, a secondary cable equivalent model is obtained according to the secondary cable parameters, a relay equivalent model is obtained based on the relay parameters, and a direct current system fault model is obtained by utilizing the charger equivalent model, the secondary cable equivalent model and the relay equivalent model, so that relevant factors influencing the operation of the direct current system are comprehensively considered, equivalent modeling is carried out on the elements in the actual direct current system, the building of the direct current system fault model is perfected, and a foundation is laid for improving the accuracy of fault analysis of the direct current system.
In one embodiment, the charger parameters may include an equivalent reactance parameter of the storage battery transformer, a transmission line parameter, an equivalent inductance parameter of the rectification side, an equivalent resistance parameter of the rectification side, and an equivalent capacitance parameter of the rectification side.
Specifically, the capacity and the number of the storage batteries in the dc system are closely related to the size of the substation and the importance of the load. The dc system may also include different charging configurations depending on the capacity of the battery pack, the charging device, and the like. Common charging structure configurations include single-charge single-point double-charge mode, double-charge mode, and double-charge triple-charge mode, wherein the most common charging structure configuration mode is a double-charge mode of double batteries, as shown in fig. 3. In addition, the design can be divided into single bus, single bus segmentation, multi-bus and the like according to different direct current bus connection modes. The double-bus segmentation mode has the characteristics of simple and clear wiring, can conveniently form two non-interconnected direct current systems, has high reliability, is convenient for direct current grounding search, and is more used in transformer substations of 220kV and above.
For the double-set charging mode of the double-set storage battery, when the direct-current bus section switch is in a disconnected state in normal operation, each section operates in sections; the storage battery floats on the direct current bus, and the charger supplies power to the load through the direct current bus and supplies power to the storage battery by small current; when one set of charger or storage battery is in fault, the section switch is closed, and the other set undertakes power supply; in one example, the charger model is as shown in fig. 4, the voltage of 500kV on the line is reduced by three step-down transformers, and then converted into 110V dc by a 12-pulse rectifier to supply power to the dc system; wherein L isTIs the equivalent reactance parameter of the transformer, Z is the transmission line parameter, expressed by the three-phase RLC centralized parameter in the simulation, LD、RD、CDThe equivalent inductance at the rectifying side, the equivalent resistance at the rectifying side and the equivalent capacitance at the rectifying side are respectively arranged; through equivalent reactance parameters, transmission line parameters and rectification side of storage battery transformerThe equivalent inductance parameter, the equivalent resistance parameter at the rectifying side, the equivalent capacitance parameter at the rectifying side and other charger parameters can establish a perfect equivalent model of the charger.
In one embodiment, the secondary cable parameters may include a secondary cable dimension parameter, a secondary cable resistance unit length parameter, a secondary cable inductance unit length parameter, a secondary cable capacitance unit length parameter, and a secondary cable conductance unit length parameter;
as shown in fig. 5, the step 302 of obtaining the equivalent model of the secondary cable based on the parameters of the secondary cable includes:
step 402, determining a secondary parameter characteristic impedance and a secondary cable propagation constant of the secondary cable by adopting a distributed parameter model based on a secondary cable resistance unit length parameter, a secondary cable inductance unit length parameter, a secondary cable capacitance unit length parameter and a secondary cable conductance unit length parameter;
and step 404, obtaining a secondary cable equivalent model according to the secondary parameter characteristic impedance of the secondary cable, the propagation constant of the secondary cable and the size parameter of the secondary cable.
In one example, the secondary cable may employ KVVP2Modeling a type 22 four-core signal cable, the structure of which is shown in fig. 6; the metal armor surrounds the four core wires, and a separate shielding layer is arranged outside each cable core and is tangent to each shielding layer; the dimensional parameters of the secondary control cable are shown in table 1, the material parameters of the cable core and the metal armor can be both set to be copper, air filling is adopted between the cable core and the shielding layer, and the insulating layer is made of standard polyvinyl chloride.
TABLE 1
The modeling of the secondary cable uses a distributed parameter model, as shown in fig. 7. R, L, C, G are unit length parameters, including resistance (Ω/m), inductance (H/m), capacitance (F/m), and conductance (S/m). According to the transmission line theory, defining its secondary parameter characteristic impedance parameter ZcAnd propagation constant gammaTo describe the waveform decay and phase shift of the current and voltage along the line, their relationship to R, L, G, C is expressed as follows:
determining the secondary parameter characteristic impedance and the secondary cable propagation constant of the secondary cable by adopting a distributed parameter model based on the secondary cable parameters; and obtaining a more perfect secondary cable equivalent model according to the secondary parameter characteristic impedance of the secondary cable, the propagation constant of the secondary cable and the size parameter of the secondary cable.
In one embodiment, the relay parameters may include a relay coil resistance parameter and a relay coil inductance parameter;
the inductance parameters of the relay coil comprise the inductance at the moment when the armature starts to move towards the iron core and the inductance at the moment when the armature starts to separate from the iron core.
Specifically, the relay parameters comprise relay coil inductance parameters and relay coil resistance parameters; modeling of the relay may primarily include calculation of relay coil inductance parameters and relay coil resistance parameters. Assuming that the average radius of the relay coil is r, there are n turns of wire, and the diameter of the wire used is d. Since copper wires are generally used for relay coils, the conductivity of the wires is 18.8 Ω · mm2And/m, then the relay resistance is calculated as follows:
for example, with reference to an actual relay, if the relay coil is formed with n 600 turns, the diameter of the wire used is 0.73mm, and the size of the relay core is 50mm × 50mm × 110mm, that is, the radius r of the coil is 25 mm. The resistance of the relay coil can be found to be:
in the process of closing the relay, the air gap is changed continuously, so that the coil inductance is not a fixed value, and the value of the coil inductance is related to the size of the air gap, the magnetic leakage and the like. Inductance L at the moment when armature begins to move toward core1Value and inductance L at the moment when armature begins to separate from core2The values are shown below:
in the formula, σ1Is the magnetic leakage coefficient when the armature is opened, F1Magnetomotive force phi at the beginning of attraction1The magnetic flux of a working air gap when the armature starts to move, and n is the number of turns of a coil; sigma2For the magnetic flux leakage coefficient in armature holding, F2Is the magnetomotive force of the armature at the beginning of release2The value of the magnetic flux of a working air gap when the armature begins to release is shown, and n is the number of turns of the coil; and obtaining the values of sigma, F, phi and n according to the relay parameters, and calculating the inductance values at the moment when the armature starts to move towards the iron core (at the moment, the armature is still at the open position) and the moment when the armature starts to separate from the iron core (at the moment, the armature is still at the closed position). According to the field measurement experience, the equivalent calculation inductance of the electromagnetic type sealed relay ranges between 0.2H and 20H, and L can be taken in one examplej＝6.2H。
In another example, a corresponding direct current system fault model is built for a direct current system of a certain 500kV substation, as shown in fig. 8, after the 500kV voltage is stepped down by a transformer, a rectifier rectifies and outputs 110V direct current voltage to supply power for the direct current system; wherein BAT is a storage battery, R1Is the internal resistance of the power supply; r+Is positiveInsulation resistance to ground, R-Is a negative electrode insulation resistor to ground; r2、R3The resistance is monitored for insulation; c1、C2Respectively positive and negative stray capacitance to ground; z0For the equivalent model of the secondary cable, the two ends of the relay are respectively provided with the secondary cable connected with the direct current circuit, C3To protect the ground capacitance of the loop; rjIs the equivalent resistance of the relay, LjIs a relay coil inductor, R4A coil is connected with a resistor in series; r5And C4Respectively an equivalent resistance and an equivalent capacitance of the online monitoring device; rjThe value of (A) is mainly determined by the coil resistance, L, of the relayjThe magnetic flux leakage, the size of the excitation ampere-turn and the size of the working air gap are related; r1、R2Is much larger than R3、R4，C1、C2Is much larger than C3。
When the fault model of the direct current system is used for transient simulation and normal operation, the voltage to earth of a direct current positive electrode and a direct current negative electrode is +/-55V respectively due to the existence of the insulation monitoring resistor. The action voltage of the relay is generally 55-70% of rated direct current voltage, the starting power of the relay is not less than 5w, after the relay is normally started, the relay automatically cuts off a power loop to ensure that the relay normally runs at low power consumption, and the power is not more than 3 w; setting the action voltage of the relay to be 55% of rated direct current voltage; wherein the secondary cable adopts KVVP2And the-22 type control cable has a resistance value of 3.31 omega/km per unit length and a secondary cable length of 200 m.
According to the method and the device, the equivalent circuit parameters of the secondary circuit of the direct current system are obtained by referring to the configuration parameters of all elements of the actual direct current system, the equivalent model of the charger, the equivalent model of the secondary cable, the equivalent model of the relay and the like are obtained respectively based on the charger parameters, the secondary cable parameters, the relay parameters and the like in the equivalent circuit parameters of the secondary circuit of the direct current system, and the fault model of the direct current system is obtained through the equivalent model of the charger, the equivalent model of the secondary cable and the equivalent model of the relay, so that the complete modeling thought and model are provided for the elements such as the insulation monitoring device, the charger, the secondary cable, the relay and the like, the integrity of the fault model of the direct current system is improved, and the accuracy of fault analysis of the direct current system is further improved.
In one embodiment, the result of the transient simulation may include: voltage change data of two ends of the relay under the direct current system ground fault and voltage change data of two ends of the relay under the direct current system series-parallel fault.
In one example, the results of the transient simulation may further include: the method comprises the following steps of amplifying voltage change data at two ends of a relay under the condition of a direct-current system ground fault, amplifying voltage change data at two ends of the relay under the condition of a direct-current system series-parallel fault, frequency spectrum analysis data of voltage at two ends of the relay under the condition of the direct-current system ground fault and frequency spectrum analysis data of voltage at two ends of the relay under the condition of the direct-current system series-parallel fault.
The direct-current system faults can include direct-current system ground faults and direct-current system series-parallel faults, the direct-current system ground faults can include direct-current positive pole ground faults, direct-current negative pole ground faults and secondary circuit cable ground faults, and the direct-current system series-parallel faults can include direct-current positive pole and alternating-current series-parallel faults, direct-current negative pole and alternating-current series-parallel faults and alternating-current mixed direct-current control loops.
Specifically, transient simulation is performed based on a fault model of the direct current system, and a result of the transient simulation may include voltage change data at two ends of the relay under the ground fault of the direct current system, voltage change data at two ends of the relay under the series-parallel fault of the direct current system, amplified voltage change data at two ends of the relay under the ground fault of the direct current system, amplified voltage change data at two ends of the relay under the series-parallel fault of the direct current system, spectral analysis data of voltages at two ends of the relay under the ground fault of the direct current system, and spectral analysis data of voltages at two ends of the relay under the series-parallel fault of the direct current system.
For the fault coupling approach of the direct current system ground fault, the situation that the insulation level of a certain point in the system to the ground is reduced due to the complicated environmental problem or the aging problem of the cable is inevitable during the long-term operation of the direct current system. The direct current system is in a floating type working mode, namely the system does not need to be grounded, the grounding does not mean that a certain pole of the direct current system is directly connected with zero potential, but the insulation level of the positive pole or the negative pole of a bus or a branch of the system to the ground is reduced, and when the insulation resistance is reduced to be lower than a threshold value, the grounding problem is considered to occur. The probability of single-point grounding in a direct current system is high, the single-point grounding generally cannot directly influence the operation of the direct current system, but if the single-point grounding is not eliminated as soon as possible, when a certain point of grounding occurs again in the system, potential safety hazards are brought to the direct current system.
For the dc positive ground fault in the dc system ground fault, in an example, after the dc system ground fault occurs, due to the action of the stray capacitance to the ground and the distributed capacitance of the cable, the voltage across the relay may generate a process of continuous oscillation change, when the voltage exceeds the action voltage value of the relay, the malfunction of the relay may be caused, the dc positive is grounded at 20ms, and the voltage waveform across the relay is as shown in fig. 9. In fig. 9(a), at the moment of ground fault, the voltage across the relay will suddenly and rapidly rise within 30 μ s, and the amplitude can reach 175V at most, which far exceeds the rated voltage of the dc system, so that the relay malfunctions. The sudden increase of the voltage across the relay is an oscillating increase due to the presence of stray capacitance to ground. Then, under the voltage division action of the relay current-limiting resistor and the relay equivalent resistor, the voltage at two ends of the relay presents a continuous oscillation change process, and the oscillation period is about 6.63 ms; FIG. 9(b) is an amplified waveform of the voltage across the relay under a DC positive ground fault; fig. 9(c) is a spectrum analysis of the voltage across the relay, the fundamental frequency is set to 50Hz, and 3, 5, 9, 12, 18 th harmonics are seen as the major harmonic components.
For a dc negative ground fault in a dc system ground fault, in one example, similar to the transient simulation of a dc positive fault, as shown in fig. 10, the dc power supply negative is grounded at fault point 2 at time 20ms, and the voltage waveform across the relay is as shown in fig. 10 (a). At the moment of grounding the negative electrode, the voltage at the two ends of the relay is rapidly increased within 10 mu s, and can reach 135V at most, and exceeds the rated voltage value of a direct current system. The negative earth fault rises faster than the dc positive earth fault, but also exhibits a process of oscillating rise. After 10ms the voltage gradually decreases, and due to the voltage regulation effect of the zener diode, the voltage across the relay does not always exhibit an oscillating process as does the positive ground fault. Fig. 10(c) is a spectrum analysis of the voltage waveform across the relay in the case of a dc negative ground fault, and it can be seen that 6 th harmonic is mainly present, and the amplitude of the harmonic is also small compared to the fundamental.
For the secondary circuit cable ground fault in the direct current system ground fault, in one example, in the secondary circuit, there are several secondary cables for connecting the relay, and the length is long. In addition to the direct current positive and negative earth faults, the secondary cable earth fault also causes certain interference to a secondary circuit and a relay. When the long cable of the secondary loop is grounded, the voltage of the ground end of the long cable is reduced to 0, and the voltage of the negative electrode of the direct current power supply is-110V, which is equivalent to that a direct current voltage of 110V is applied to two ends of the secondary cable and the relay. The secondary loop long cable is grounded at 20ms, and the transient simulation waveform is shown in fig. 11. At the moment of grounding, the voltage across the relay drops to-11.74V, then rapidly changes to 0 again, and after keeping for about 0.7ms, the process begins to present an oscillation rising and falling process, and then the process is kept, the voltage can reach 61.98V at most, and the main harmonic components are 3, 6, 9, 12 and 18 times. Compared with the direct current positive and negative electrode ground faults, the transient overvoltage amplitude generated by the secondary cable ground fault is lower, but exceeds 55% of the rated voltage of a direct current system, and the misoperation of the relay can be caused.
For the fault coupling approach of the series-parallel fault of the direct current system, the alternating current fleeing into the direct current fault also belongs to the ground fault of the direct current system in essence. The station direct current system is an ungrounded system, namely, the positive electrode and the negative electrode are well electrically isolated from the ground in normal operation, and in the alternating current system, a neutral line is generally connected to a transformer substation grounding grid. Therefore, when an Alternating Current (AC) flees into a Direct Current (DC) fault, the DC circuit is equivalent to one point of grounding, and an attenuated driving voltage appears at two ends of the relay.
For a dc positive electrode and ac series-parallel fault in a dc system series-parallel fault, in an example, when ac 220V enters a dc system, a ringing voltage may appear across a relay, similar to a dc system ground fault, but since ac 220V enters, which is equivalent to injecting a 220V ac power supply into the ground, the voltage amplitude is higher compared to the ground fault, and thus the malfunction of the relay is more easily caused. The maximum instantaneous value of 220V AC voltage can reach 311V, and after the DC voltage is superposed, the maximum voltage at two ends of the relay can reach 590.2V, resulting in the malfunction of the relay. An ac 220V ingress dc fault was simulated at 20ms, and the transient voltage waveforms across the relay are shown in fig. 12. Fig. 12(a) is a transient waveform of the voltage across the relay for 20 to 90ms, and fig. 12(b) is an enlargement of the voltage waveform of fig. 12 (a). At the moment of alternating current channeling, the voltage at two ends of the relay begins to rise rapidly, and damped oscillation occurs, the peak voltage is 590.2V, and the peak voltage far exceeds the action voltage of the relay. At the moment 32.4ms the oscillation process is over and then the voltage waveform approaches a sinusoidal waveform, the voltage across the relay only exhibiting a positive half wave due to the presence of the zener diode. The harmonic components that are mainly present are the 2 rd and 3 rd order harmonics.
For the dc negative electrode and ac series-parallel fault in the dc system series-parallel fault, in one example, an ac 220V voltage is applied to the dc negative electrode at 20ms, and its transient simulation waveform is shown in fig. 13. Compared with a direct-current positive electrode series-parallel fault, the voltage peak value of a fault that 220V alternating current jumps into a direct-current negative electrode is reduced, and under the action of a voltage stabilizing diode, voltage fluctuation is greatly reduced after the oscillation process is finished, so that damage to a relay and a secondary system is not as great as that of the positive electrode series-parallel fault, the voltage peak value at two ends of the relay can reach 533.4V at most, and is far larger than the action voltage of the relay, and misoperation of the relay is caused. The voltage is relatively reduced compared to a dc positive series-parallel fault, but this also causes malfunction of the relay. The main harmonic components are 2 and 3 harmonics, and the amplitude component of the direct current voltage is the highest.
For an ac mixed dc control loop fault in a dc system series-parallel fault, in one example, an ac 220V voltage is applied at fault point 2 at 20ms, and its transient simulation waveform is shown in fig. 14. The voltage at two ends of the relay rises rapidly at the moment of fault, the maximum voltage can reach 300V, then the voltage oscillates within 5ms and falls to 0, then the voltage at two ends presents a waveform of sine half-wave, and the main harmonic components are 2, 3 and 4 harmonics. The voltage peak is lowest compared to the positive and negative series-parallel faults.
Further, simulation analysis is carried out on the direct current system grounding and the direct current system series-parallel connection faults, and it can be found that after the faults occur, voltages at two ends of the relay are increased to different degrees and exceed the action voltage of the relay, so that false operation of the relay is caused, and safe operation of the system is damaged. The reliability of the operation of the direct current system is reduced when the action voltage of the relay is too small and the stray capacitance of the direct current system to the ground is too large. Therefore, the interference resistance of the secondary circuit of the direct current system can be improved in terms of both improving the operational reliability of the relay and reducing the stray capacitance to ground existing in the secondary circuit.
In one example, the precautionary data may include data to improve the operational reliability of the relay and data to reduce the capacitance to ground of the secondary loop.
The operation reliability of the relay mainly depends on the operation voltage and the operation power of the relay. According to relevant standards in China, the action voltage of all relays relevant to a direct tripping relevant loop is within the range of 55-70% of the rated voltage of a direct current system, and the action power of the relays is more than or equal to 5W. In the transient simulation of the present application, the condition that tripping is most likely to occur can be taken, the action voltage of the relay is set to 55% of the rated voltage of the direct current system, namely 60.5V, and the action power is set to 5W. Therefore, the safety data can be related data for setting a higher relay operation voltage and a higher relay operation power, thereby improving the reliability of the relay operation and reducing the malfunction rate of the relay, but care should be taken that the rated voltage of the 70% dc system specified in the related standard is not exceeded.
Direct current systemThe stray capacitance to ground of (1) mainly comes from two aspects, namely the capacitance to ground of the control cable on one hand, and the input stage filter capacitance of the switching power supply of the protection equipment and the like on the other hand, wherein the input stage filter capacitance of the switching power supply is generally fixed, so that the consideration can be taken from reducing the capacitance to ground of the control cable. The secondary cable is used for connecting various electrical equipment and loads in a secondary loop of the direct current system, and a secondary side and a control chamber of the field mutual inductor. In one specific example, KVVP may be employed in the simulation2-22 type four-core secondary cable with a shielding layer outside each phase core. According to the relevant standards of national network, the shielding layer of the secondary cable should be grounded at two ends, so as to enhance the electromagnetic shielding effect. However, since the two ends of the secondary cable shielding layer are grounded, stray capacitance to ground cannot be avoided, a path for interference coupling is increased, and the longer the cable length is, the more significant the distributed capacitance effect is. Therefore, the following precautionary data may be included: when the wiring design of a power plant and a transformer substation is carried out, the length of a secondary cable is reduced as much as possible, and wiring is reasonably arranged; for a power plant and a transformer substation with large floor area, a plurality of point protection cells are designed, and if the conditions do not allow only a single relay cell to be arranged, the cell position is arranged at the center of the power plant or the transformer substation as far as possible; cables for different purposes can be separately arranged, so that the length of a secondary cable is reduced; and eliminating the distributed capacitance effect of the secondary cable by transmitting signals using an optical front channel.
In the method, relevant parameters such as a charger parameter, a secondary cable parameter, a relay parameter and the like in a secondary circuit equivalent circuit parameter of the direct current system are processed to respectively obtain relevant models such as a charger equivalent model, a secondary cable equivalent model, a relay equivalent model and the like, a direct current system fault model is obtained according to the relevant models such as the charger equivalent model, the secondary cable equivalent model, the relay equivalent model and the like, transient simulation is respectively carried out on a direct current system ground fault and a direct current system series-parallel fault in parallel based on the direct current system fault to obtain a transient simulation result, a fault coupling path and a relay action process are analyzed in detail according to the transient simulation result, and precautionary data for preventing the direct current system secondary circuit fault are obtained and output. According to the method, the configuration parameters of all elements in the actual direct current system are opened, influence factors such as a charger, a secondary control cable and a relay are considered, and an equivalent model is established based on the configuration parameters of the actual elements, so that a direct current system fault model is perfected, detailed and accurate transient simulation result analysis is performed on the direct current system fault by using the perfected direct current system fault model, and more accurate precaution data for preventing the direct current system fault are output.
It should be understood that although the steps in the flowcharts of fig. 1, 2 and 5 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1, 2 and 5 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least some of the other steps.
In one embodiment, as shown in fig. 15, there is provided a direct current system modeling simulation apparatus, which may include:
the model establishing module 510 is configured to obtain equivalent circuit parameters of a secondary circuit of the dc system, and process the equivalent circuit parameters of the secondary circuit of the dc system to obtain a fault model of the dc system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
the processing module 520 is configured to perform transient simulation on the dc system ground fault and the dc system series-parallel fault respectively based on the dc system fault model to obtain a transient simulation result;
and the output module 530 is configured to analyze the fault coupling path and the relay action process according to the transient simulation result, and obtain and output prevention data for preventing the fault of the secondary circuit of the dc system.
In one embodiment, the model building module may include:
the first model establishing unit is used for obtaining a charger equivalent model according to the charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and the second model establishing unit is used for obtaining a direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
In one embodiment, the charger parameters may include an equivalent reactance parameter of the storage battery transformer, a transmission line parameter, an equivalent inductance parameter of the rectification side, an equivalent resistance parameter of the rectification side, and an equivalent capacitance parameter of the rectification side.
In one embodiment, the secondary cable parameters may include a secondary cable dimension parameter, a secondary cable resistance unit length parameter, a secondary cable inductance unit length parameter, a secondary cable capacitance unit length parameter, and a secondary cable conductance unit length parameter;
the first model building unit may include: the first unit is used for determining the secondary parameter characteristic impedance and the secondary cable propagation constant of the secondary cable by adopting a distributed parameter model based on the unit length parameter of the secondary cable resistance, the unit length parameter of the secondary cable inductance, the unit length parameter of the secondary cable capacitance and the unit length parameter of the secondary cable conductance;
and the second unit is used for obtaining a secondary cable equivalent model according to the secondary parameter characteristic impedance of the secondary cable, the propagation constant of the secondary cable and the size parameter of the secondary cable.
In one embodiment, the relay parameters may include a relay coil resistance parameter and a relay coil inductance parameter;
the relay coil inductance parameters may include the inductance at the instant the armature begins to move toward the core, and the inductance at the instant the armature begins to disengage from the core.
In one embodiment, the results of the transient simulation include: voltage change data of two ends of the relay under the direct current system ground fault and voltage change data of two ends of the relay under the direct current system series-parallel fault.
For specific limitations of the dc system modeling simulation apparatus, reference may be made to the above limitations of the dc system modeling simulation method, which are not described herein again. All or part of each module in the direct current system modeling and simulating device can be realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules. It should be noted that, in the embodiment of the present application, the division of the module is schematic, and is only one logic function division, and there may be another division manner in actual implementation.
In one embodiment, a computer device is further provided, which includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method embodiments when executing the computer program.
In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method embodiments.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A direct current system modeling simulation method is characterized by comprising the following steps:
acquiring equivalent circuit parameters of a secondary circuit of a direct current system, and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
respectively performing transient simulation on a direct current system ground fault and a direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result;
and analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output prevention data for preventing the fault of the secondary circuit of the direct current system.
2. The direct-current system modeling simulation method according to claim 1, wherein the step of processing the parameters of the equivalent circuit of the secondary circuit of the direct-current system to obtain a fault model of the direct-current system comprises:
obtaining a charger equivalent model according to the charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and obtaining the direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
3. The direct current system modeling simulation method of claim 2, wherein the charger parameters include battery transformer equivalent reactance parameters, transmission line parameters, rectifier side equivalent inductance parameters, rectifier side equivalent resistance parameters, and rectifier side equivalent capacitance parameters.
4. The direct current system modeling simulation method of claim 2, wherein the secondary cable parameters include a secondary cable dimension parameter, a secondary cable resistance unit length parameter, a secondary cable inductance unit length parameter, a secondary cable capacitance unit length parameter, and a secondary cable conductance unit length parameter;
the step of obtaining a secondary cable equivalent model based on the secondary cable parameters includes:
determining the secondary parameter characteristic impedance and the secondary cable propagation constant of the secondary cable by adopting a distributed parameter model based on the secondary cable resistance unit length parameter, the secondary cable inductance unit length parameter, the secondary cable capacitance unit length parameter and the secondary cable conductance unit length parameter;
and obtaining the equivalent model of the secondary cable according to the characteristic impedance of the secondary parameter of the secondary cable, the propagation constant of the secondary cable and the size parameter of the secondary cable.
5. The direct current system modeling simulation method of claim 2, wherein the relay parameters include a relay coil resistance parameter and a relay coil inductance parameter;
the inductance parameters of the relay coil comprise the inductance at the moment when the armature starts to move towards the iron core and the inductance at the moment when the armature starts to separate from the iron core.
6. The direct current system modeling simulation method of claim 1, wherein the results of the transient simulation comprise: and the voltage change data of the two ends of the relay under the direct current system ground fault and the voltage change data of the two ends of the relay under the direct current system series-parallel fault.
7. A direct current system modeling simulation apparatus, the apparatus comprising:
the model establishing module is used for acquiring the equivalent circuit parameters of the secondary circuit of the direct current system and processing the equivalent circuit parameters of the secondary circuit of the direct current system to obtain a fault model of the direct current system; the parameters of the equivalent circuit of the secondary circuit of the direct current system comprise parameters of a charger, parameters of a secondary cable and parameters of a relay;
the processing module is used for respectively carrying out transient simulation on the direct current system ground fault and the direct current system series-parallel fault based on the direct current system fault model to obtain a transient simulation result;
and the output module is used for analyzing the fault coupling path and the action process of the relay according to the transient simulation result to obtain and output precaution data for preventing the fault of the secondary circuit of the direct current system.
8. The direct current system modeling simulation apparatus of claim 7, wherein the model building module comprises:
the first model establishing unit is used for obtaining a charger equivalent model according to the charger parameters; obtaining a secondary cable equivalent model based on the secondary cable parameters, and determining a relay equivalent model according to the relay parameters;
and the second model establishing unit is used for obtaining the direct current system fault model based on the charger equivalent model, the secondary cable equivalent model and the relay equivalent model.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method of any of claims 1 to 6.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 6.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114089023A (en) * | 2021-11-12 | 2022-02-25 | 中国南方电网有限责任公司超高压输电公司梧州局 | Detection method and device for secondary cable disturbance voltage by VFTO and computer equipment |
| CN114167175A (en) * | 2021-11-29 | 2022-03-11 | 广西电网有限责任公司钦州供电局 | Relay alternating current channeling and voltage fluctuation testing method |
| CN114362572A (en) * | 2022-01-13 | 2022-04-15 | 国网江苏省电力有限公司 | Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114089023A (en) * | 2021-11-12 | 2022-02-25 | 中国南方电网有限责任公司超高压输电公司梧州局 | Detection method and device for secondary cable disturbance voltage by VFTO and computer equipment |
| CN114167175A (en) * | 2021-11-29 | 2022-03-11 | 广西电网有限责任公司钦州供电局 | Relay alternating current channeling and voltage fluctuation testing method |
| CN114362572A (en) * | 2022-01-13 | 2022-04-15 | 国网江苏省电力有限公司 | Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault |
| CN114362572B (en) * | 2022-01-13 | 2024-02-09 | 国网江苏省电力有限公司 | Calculation method for maximum temporary overvoltage of parallel MMC under alternating current short circuit fault |
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