CN117171502B - Method for calculating DC fault overvoltage peak value of multi-DC external power supply system by bundling wind and fire - Google Patents
Method for calculating DC fault overvoltage peak value of multi-DC external power supply system by bundling wind and fire Download PDFInfo
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Abstract
The invention discloses a method for calculating a DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire, which comprises the following steps: determining a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system according to a plurality of voltages and a plurality of powers of the multi-direct current external power transmission system with different fan numbers in a direct current near zone; determining active power and reactive power consumed by a direct current system in the multi-direct current external power supply system under different fault types; and substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value. According to the method, the low voltage ride through characteristic of the fan and the direct current fault reactive characteristic and overvoltage coupling relation are considered, so that the direct current fault overvoltage peak value of the multi-direct current external power transmission system bundled by wind and fire can be calculated, and the accuracy of a calculation result is improved.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a method for calculating a DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire.
Background
The high-proportion wind power access scene provides higher requirements for quantitatively evaluating the safety stability of the power grid voltage. In order to solve the problem of the digestion, the HVDC transmission engineering is continuously constructed, so that a large-scale DC output system appears in the area. In such a system, two or more direct currents, which are electrically close to each other, and the ac power grid fed out as a whole constitute a multi-direct current feed-out system. Although the multi-dc delivery system can improve the power generation and consumption reverse distribution pattern, however, the voltage safety problem of the large-scale wind power after suffering from direct current disturbance by the multi-direct current output system is serious. Therefore, it is necessary to establish a proper method for calculating the dc fault overvoltage peak value of the multi-dc delivery system bundled by wind and fire.
At present, the research methods of the calculation method of the overvoltage peak value of the direct current fault current conversion bus mainly comprise an estimation method, an alternating current equivalence method, a reactive short-circuit ratio method, a single-branch voltage drop method and the like. In the prior art, the analysis of the system overvoltage peak value is often aimed at the analysis of a single direct current transmission system, and the analysis of the system direct current fault overvoltage by a plurality of transmission direct currents is also fuzzy. In addition, the analysis of the overvoltage peak value of the system mainly considers the influence of the reactive power characteristic of the direct current fault on the overvoltage independently, and the analysis of the low voltage ride through characteristic of the fan and the coupling relation between the reactive power characteristic of the direct current fault and the overvoltage is lacked, so that the calculation result is inaccurate.
Disclosure of Invention
In order to solve at least one technical problem, the invention provides a method for calculating the DC fault overvoltage peak value of a multi-DC external power transmission system by wind and fire bundling, which can improve the accuracy of the DC fault overvoltage peak value calculation result of the multi-DC external power transmission system by wind and fire bundling.
The invention provides a method for calculating a DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire, which comprises the following steps:
according to a plurality of direct-current external power transmission systems with different fans in a direct-current near zone, determining a converter bus overvoltage calculation model after the direct-current fault of the plurality of direct-current external power transmission systems occurs;
determining active power and reactive power consumed by a direct current system in the multi-direct current external power supply system under different fault types;
and substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value. Determining a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system according to a plurality of voltages and a plurality of powers of the multi-direct current external power transmission system with different fan numbers in a direct current near zone;
determining active power and reactive power consumed by a direct current system in the multi-direct current external power supply system under different fault types;
and substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value.
Preferably, the determining the active power and the reactive power consumed by the dc system of the multi-dc power-out system under different fault types includes:
when a direct current blocking fault occurs, the active power and the reactive power consumed by the direct current system are determined to be 0.
Preferably, the determining the active power and the reactive power consumed by the dc system of the multi-dc power-out system under different fault types further includes:
when a commutation failure fault occurs, calculating the active power consumed by the direct current system according to the minimum value of the direct current and the minimum value of the direct current voltage after the fault;
and calculating reactive power consumed by the direct current system according to the minimum value of the direct current after the fault, the no-load direct current voltage and the direct current resistance.
Preferably, before determining the converter bus overvoltage calculation model after the dc fault of the multi-dc external power supply system, the method further includes:
and changing the equivalent impedance of the system to obtain a plurality of direct-current external power transmission systems with different fans in the direct-current near areas.
Preferably, the determining a converter bus overvoltage calculation model after the dc fault occurs in the multi-dc external power supply system includes:
calculating the system side voltage of the alternating current system after the direct current fault according to the voltage of the alternating current system after the fault and the active power and reactive power transmitted by the system side direction alternating current bus of the alternating current system after the fault; the method comprises the steps of,
and calculating the voltage of the fan side of the alternating current system after the fault according to the voltage of the commutation bus of the alternating current system after the fault and the active power and the reactive power sent out by the fan side after the fault.
Preferably, the determining the converter bus overvoltage calculation model after the dc fault of the multi-dc external power supply system further includes:
and calculating the current alternating current system conversion bus voltage according to the active power and reactive power sent by the current alternating current system after the fault to the other alternating current system and the equivalent impedance connecting the current alternating current system and the other alternating current system.
Preferably, the determining the converter bus overvoltage calculation model after the dc fault of the multi-dc external power supply system further includes:
calculating the active power sent out by the fan side after the fault according to the rated active power output of the fan of the alternating current system and the proportional coefficient of the active power output of the fan of the alternating current system during the low voltage ride through period;
and calculating reactive power sent out by the fan side after the fault according to rated reactive power output of the fan of the alternating current system and the proportional coefficient of reactive power output of the fan of the alternating current system during low voltage ride through.
Preferably, the determining the converter bus overvoltage calculation model after the dc fault of the multi-dc external power supply system further includes:
and according to the active power sent out by the wind turbine side of the AC system after the fault, the active power consumed by the DC system, the AC system after the fault sends out the sum of the active powers to other AC systems, and the active power sent by the system side converter bus of the AC system after the fault is calculated.
Preferably, the determining the converter bus overvoltage calculation model after the dc fault of the multi-dc external power supply system further includes:
according to the reactive power sent out by the wind turbine side of the AC system after the fault, the reactive power sent out by the reactive compensation of the AC system after the fault and the sum of the reactive power sent out by the AC system after the fault to other AC systems, the reactive power consumed by the DC system calculates the reactive power transmitted by the lateral converter bus of the AC system after the fault;
and the reactive power sent by the reactive compensation of the AC system after the fault is in direct proportion to the voltage of the commutation bus of the AC system after the fault.
The invention also provides a system for calculating the direct-current fault overvoltage peak value of the multi-direct-current external power supply system by bundling wind and fire, which comprises the following components:
the model construction unit is used for determining a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system according to the multi-direct current external power transmission system with different fans in the direct current near zone;
the parameter calculation unit is used for determining active power and reactive power consumed by a direct current system in the multi-direct current external power transmission system under different fault types;
and the peak value calculation unit is used for substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate the direct current fault overvoltage peak value.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a method for calculating a DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire, which comprises the following steps: according to a plurality of direct-current external power transmission systems with different fans in a direct-current near zone, determining a converter bus overvoltage calculation model after the direct-current fault of the plurality of direct-current external power transmission systems occurs; determining active power and reactive power consumed by a direct current system in the multi-direct current external power supply system under different fault types; and substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value. According to the method, the low voltage ride through characteristic of the fan and the direct current fault reactive characteristic and overvoltage coupling relation are considered, so that the direct current fault overvoltage peak value of the multi-direct current external power transmission system bundled by wind and fire can be calculated, and the accuracy of a calculation result is improved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
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In order to more clearly describe the embodiments of the present invention or the technical solutions in the background art, the following description will describe the drawings that are required to be used in the embodiments of the present invention or the background art.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the disclosure and together with the description, serve to explain the technical aspects of the disclosure.
Fig. 1 is a schematic flow chart of a method for calculating a dc fault overvoltage peak value of a multi-dc external power transmission system by bundling wind and fire according to an embodiment of the present invention.
Fig. 2 is a simplified wind-fire bundling multi-dc external power system model diagram according to an embodiment of the present invention.
Fig. 3 is a dynamic diagram of commutation bus voltage after failure in commutation under different numbers of fans in a direct current near zone according to an embodiment of the present invention.
Fig. 4 is a dynamic diagram of the voltage of the converter bus after the dc blocking failure under different numbers of fans in the dc near zone according to the embodiment of the present invention.
FIG. 5 is a graph of equivalent impedance of different systems provided by an embodiment of the present inventionAnd converting the busbar voltage dynamic diagram after the failure fault of the lower commutation.
FIG. 6 is a graph of differential system equivalent impedance provided by an embodiment of the present inventionAnd a voltage dynamic diagram of the converter bus after the lower direct current blocking fault.
Fig. 7 is a flowchart illustrating a specific implementation process of a dc fault overvoltage peak value calculation method for a multi-dc external power system with wind-fire bundling according to another embodiment of the present invention.
Fig. 8 is a schematic structural diagram of a dc fault overvoltage peak calculation system of a multi-dc external power transmission system with wind and fire bundling according to an embodiment of the present invention.
Fig. 9 is a schematic hardware structure of an electronic device according to an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terms first, second and the like in the description and in the claims and in the above-described figures are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.
The term "and/or" is herein merely an association relationship describing an associated object, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the term "at least one" herein means any one of a plurality or any combination of at least two of a plurality, for example, including at least one of A, B, C, and may mean including any one or more elements selected from the group consisting of A, B and C.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better illustration of the invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, well known methods, procedures, components, and circuits have not been described in detail so as not to obscure the present invention.
At present, the analysis of the overvoltage peak value of the system mainly considers the influence of the reactive power characteristic of the direct current fault on the overvoltage independently, and the analysis of the low voltage ride through characteristic of the fan and the coupling relation of the reactive power characteristic of the direct current fault and the overvoltage is lacking. Along with the rapid development of the high-voltage direct-current system, a plurality of direct-current outgoing channels exist in the direct-current outgoing system, and the analysis of the direct-current fault overvoltage of the system by the plurality of outgoing direct currents is more fuzzy in the prior art. Therefore, the method provided by the invention considers the analysis of the low voltage ride through characteristic, the reactive power characteristic of the direct current fault and the overvoltage coupling relation of the fan, thereby improving the accuracy of the direct current fault overvoltage peak value calculation result.
Referring to fig. 1, fig. 1 is a flowchart illustrating a method for calculating a dc fault overvoltage peak value of a multi-dc power system with wind-fire bundling according to an embodiment (a) of the present invention.
A method for calculating DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire comprises the following steps:
s10, determining a converter bus overvoltage calculation model after the DC fault of the multi-DC external power transmission system according to a plurality of voltages and a plurality of powers of the multi-DC external power transmission system with different fan numbers in a DC near zone;
s20, determining active power and reactive power consumed by a direct current system in the multi-direct current external power transmission system under different fault types;
s30, substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value.
The direct current near zone comprises multiple direct current external power supply systems with different fan numbers, and various scenes can be established through the direct current external power supply systems.
Specifically, on the basis of a multi-output power system model, the total power generation output of the system is kept unchanged, and the number of direct-current near-area fans is changed, so that the change of the near-area fan output is realized, and multi-output power system scenes of different near-area fan numbers or outputs can be obtained.
Preferably, the method for calculating the direct-current fault overvoltage peak value of the multi-direct-current external power supply system by bundling wind and fire further comprises the following steps:
and changing the equivalent impedance of the system to obtain a plurality of direct-current external power transmission systems with different numbers of fans in the direct-current near areas. It can be appreciated that the multi-dc external power system structure is generally determined by the equivalent impedance of the system, and the multi-output power system scenario of different system structures can be obtained by changing one type of parameters.
In step S10, through the built multi-dc external power transmission system with different numbers of fans in the dc near zone, the calculation model of the overvoltage of the converter bus after the dc fault of the multi-dc external power transmission system can be determined, so that the model considers both the multi-dc external power transmission system and the influence of the fans.
In step S20, the active power and reactive power consumed by the dc system in the multi-dc external power transmission system under different fault types are further determined, and then the active power and reactive power consumed by the dc system under different fault types are substituted into the model obtained in step S10, so that the dc fault overvoltage peak value of the multi-dc external power transmission system including wind fire bundling can be calculated.
Therefore, in the embodiment, the analysis of the low voltage ride through characteristic, the direct current fault reactive characteristic and the overvoltage coupling relation of the fan is considered to establish a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system occurs, so that the finally calculated direct current fault overvoltage peak value is more accurate.
In one embodiment, establishing a multi-dc external power system scenario with different numbers of fans and different system structures in a dc near zone includes:
according to the Dai Weining theorem, the equivalence of the multi-direct-current external power transmission system bundled by the actual wind and fire is expressed as a fixed electromotive force in a form of equivalent impedance connection, as shown in fig. 1. Wherein,for communication system->System side equivalent impedance, < >>For communication system->System side equivalent impedance, < >>For connecting communication systems->Communication system->Equivalent impedance of->For communication system->Equivalent impedance of fan side->For communication system->Equivalent impedance at the fan side.
The specific method for constructing the multi-DC output system scene of the fan output of different DC near areas comprises the following steps: on the basis of a multi-output power system model, the total power generation output of the system is kept unchanged, and the number of direct-current near-area fans is changed, so that the change of the near-area fan output is realized, and multi-output power system scenes of different near-area fan numbers or outputs can be obtained.
The specific method for constructing the multi-direct-current power-output system scene with different system structures comprises the following steps: the multi-output system structure is composed of system equivalent impedanceAnd determining, namely, changing a certain type of parameters to obtain multiple-output power system scenes of different system structures.
According to the embodiment, various scenes and structures are established, so that the calculation process of the overvoltage of the converter bus after the direct current fault under various conditions is considered, and the calculation result is more accurate.
In one embodiment, determining a converter bus overvoltage calculation model after a dc fault in a multi-dc power-out system includes:
calculating the system side voltage of the alternating current system after the direct current fault according to the voltage of the alternating current system after the fault and the active power and reactive power transmitted by the system side direction alternating current bus of the alternating current system after the fault; the method comprises the steps of,
and calculating the voltage of the fan side of the alternating current system after the fault according to the voltage of the commutation bus of the alternating current system after the fault and the active power and the reactive power sent out by the fan side after the fault.
Preferably, the reactive power generated by the reactive compensation of the AC system after the fault is in direct proportion to the voltage of the converting bus of the AC system after the fault.
Preferably, the current alternating current system converter bus voltage is calculated according to the active power and the reactive power sent by the current alternating current system after the fault to the other alternating current system and the equivalent impedance connecting the current alternating current system and the other alternating current system.
Calculating the active power sent out by the fan side after the fault according to the rated active power output of the fan of the alternating current system and the proportional coefficient of the active power output of the fan of the alternating current system during the low voltage ride through period;
and calculating reactive power sent out by the fan side after the fault according to rated reactive power output of the fan of the alternating current system and the proportional coefficient of reactive power output of the fan of the alternating current system during low voltage ride through.
And according to the active power sent out by the wind turbine side of the AC system after the fault, the active power consumed by the DC system, the AC system after the fault sends out the sum of the active powers to other AC systems, and the active power sent by the system side converter bus of the AC system after the fault is calculated.
And calculating the reactive power transmitted by the system lateral converter bus of the AC system after the fault according to the reactive power transmitted by the AC system fan side after the fault, the reactive power transmitted by the AC system after the fault and the reactive power transmitted by the AC system to other AC systems after the fault.
In this embodiment, a calculation model of the dc fault overvoltage of the converter bus after the dc fault of the multi-dc external power transmission system is determined mainly according to a theoretical analysis method of the dc fault overvoltage of the multi-dc external power transmission system bundled by wind and fire.
Firstly, a theoretical analysis method of the overvoltage of the converter bus after the direct current fault of the multi-direct current external power transmission system bundled by wind and fire is deduced. Referring to fig. 2, fig. 2 provides a schematic structural diagram of the system in a quasi-steady state mode, the converter stations all operate in a rectifying state, and the ac system is simplified to a fixed electromotive force series reactance. The power of the wind fire bundled multi-DC output system at the rectifying side can be described by the following algebraic equation:
wherein:for communication system during steady state->The fan side sends out active power; />For communication system during steady state->The fan side sends out reactive power; />For communication system during steady state->Active power sent out by the system side; />For communication system during steady state->The system side sends out reactive power; />For communication system during steady state->The converter stations are connected in parallel to compensate reactive power; />For communication system during steady state->Active power consumed by the connected direct current system; />For communication system during steady state->Reactive power consumed by the connected direct current system; />For communication system during steady state->To exchange system->The active power delivered; />For communication system during steady state->To exchange system->Reactive power delivered.
Further, after a direct current fault occurs, the power transmitted by the direct current system changes sharply, and the theoretical analysis method of the overvoltage of the converter bus after the direct current fault is as follows:
step 1: AC system after DC faultSystem side voltage->Can pass through the communication system after fault->Converter bus voltage->Post-fault communication system->Power supplied by lateral converter bus of system +.>And->And (3) obtaining:
wherein:for post-fault communication system->The fan side sends out active power; />For post-fault communication system->Reactive power sent out by the fan side; />For post-fault communication system->The system side sends out active power; />For post-fault communication system->The system side sends out reactive power; />For post-fault communication system->To exchange system->The active power sent out; />For post-fault communication system->To exchange system->Sending out reactive power; />For post-fault communication system->Reactive power generated by reactive compensation; />For post-fault communication system->Active power consumed by the connected direct current system; />For post-fault communication system->Reactive power consumed by the connected direct current system; />For post-fault communication system->System side bus voltage; />For post-fault communication system->Commutation bus voltage.
Step 2: post-fault communication systemSide voltage of wind turbine>Can pass through the communication system after fault->Converter bus voltageFan side output power after failure>And->And (3) obtaining:
in the method, in the process of the invention,for post-fault communication system->Fan side bus voltage.
Step 3: post-fault communication systemConverter bus voltage->Through post-fault converter bus>Voltage->And the active power sent by the AC system i to the AC system j after the fault>And reactive power->And (3) obtaining:
wherein,for post-fault communication system->Commutation bus voltage.
Step 4: the ac filter and the reactive power compensator are mostly composed of capacitors, the reactive power output by the ac filter and the reactive power compensator is proportional to the square of the voltage, and then the reactive power output by the ac filter and the reactive power compensator during a fault can be expressed as:
step 5: the control logic during the low voltage ride through of the blower is typically: the reactive power output of the fan is in direct proportion to the voltage drop amplitude of the machine end, and the active power output of the fan is limited to be a smaller value. Therefore, the active and reactive power output of the fan after the fault is as follows:
wherein:alternating current system during low voltage ride through>The fan reactive power output proportionality coefficient; />Alternating current system during low voltage ride through>The fan active output proportionality coefficient; />For communication system->Rated active force of the fan; />For communication system->The rated reactive power of the fan is output.
Step 6: and (3) solving the formulas from the 1 st step to the 5 th step simultaneously to obtain the calculation formulas of the bus overvoltage of each convertor station after the direct-current fault.
In the embodiment, when the model is established, the influence of the low-voltage ride-through characteristic, the direct-current fault reactive characteristic and the overvoltage coupling relation of the fan on the direct-current fault overvoltage peak value of the multi-direct-current external power transmission system which is used for bundling wind and fire is considered, so that the calculation result can be accurate.
In order to obtain the method for calculating the overvoltage peak value caused by the direct current fault, active and reactive power consumed by the direct current system during the direct current fault needs to be dynamically analyzed. The reactive power consumed by the rectifier can change along with the change of the direct current voltage, the current and the trigger angle when the commutation fails or the direct current is blocked, and only the minimum reactive power consumed by the converter station in the fault process is needed to be considered when the fault overvoltage peak value is calculated, so that the impact of the reactive power emitted by the direct current system on the system voltage of the transmitting end is maximum. Due to the magnitude and the overvoltageAnd->The magnitude of the overvoltage will thus be different for different dc faults, and the following considerations are made for dc blocking and commutation failure faults, respectively.
Preferably, determining the active power and the reactive power consumed by the dc system in the multi-dc power-out system under different fault types includes:
when a direct current blocking fault occurs, the active power and the reactive power consumed by the direct current system are determined to be 0.
When a commutation failure fault occurs, calculating the active power consumed by the direct current system according to the minimum value of the direct current and the minimum value of the direct current voltage after the fault;
and calculating reactive power consumed by the direct current system according to the minimum value of the direct current after the fault, the no-load direct current voltage and the direct current resistance.
1) DC blocking fault overvoltage peak analysis
When a dc blocking fault occurs, the dc system is considered to be gradually shut down and the active and reactive power ultimately consumed is 0. The system voltage reaches a peak value when the direct current system completely stops working, namely, the active power and the reactive power consumed by the direct current system when the overvoltage of the direct current blocking fault reaches the peak value are as follows:
and substituting the value into the formula of the step 1 in the embodiment, and simultaneously solving to obtain the overvoltage peak value of the converter bus after the direct current blocking fault.
2) Commutation failure fault overvoltage peak analysis
The minimum reactive power consumption moment of the commutation failure direct current system can be considered as the commutation failure overvoltage peak value moment, and at this moment, the active power and reactive power consumed by the direct current system can be expressed as:
wherein,minimum value set for direct current after failure, +.>Is no-load DC voltage>Is a direct current resistor>Is the minimum value of the direct current voltage after the fault.
And (3) substituting the formula into the formula in the step 1 of the embodiment, and simultaneously solving to obtain the overvoltage peak value of the converter bus after the direct current blocking fault.
In this embodiment, for different dc faults, the magnitude of the overvoltage will be different, and the following dc blocking and commutation failure faults are considered respectively, so that the calculation result is more accurate.
To aid understanding, embodiments of the present invention are further described below by way of example, which is only an example of embodiments of the present invention, and the embodiments of the present invention are not limited thereto.
The effectiveness of the method is verified in a two-DC power system bundled by wind and fire, and the structure is shown in figure 2.
By using the method, the system structure is kept unchanged, the direct current near-area fans of the converting bus of the alternating current system 1 are changed, and the relationship between the number of the direct current near-area fans and the direct current fault overvoltage peak value is analyzed.
When the direct current fails to commutate, the near-area fan enters low-voltage ride through, and reactive power output is increased to some extent. When the direct current blocking fault occurs, the voltage of the converter station and the near zone thereof can be rapidly increased, and the fan can not enter low voltage ride through. The peak fault overvoltage pairs for different fan numbers are shown in table 1. Voltage dynamic curves after commutation failure faults and direct current blocking faults under different numbers of direct current near-zone fans are respectively shown in fig. 3 and fig. 4.
As can be seen from fig. 3 and 4, dc blocking, dc commutation failure, etc. may cause transient overvoltage. However, the failure of direct current commutation can cause a large number of surrounding fans to enter low voltage ride through, and reactive surplus of a wind farm and a convertor station are overlapped, so that the system voltage can be further raised. The direct current blocking can not cause the fan to enter low voltage ride through, and the converter station is the only reactive power source of the transient overvoltage of the direct current blocking transmitting end. Therefore, the near-end transient voltage is generally higher than the dc blocking during the dc commutation failure. The analysis result shows that when the number of fans is increased, the commutation failure fault overvoltage peak value is increased, and the direct current blocking fault overvoltage peak value is unchanged. Comparing the simulation result and the mathematical model analysis result, the difference between the simulation result and the mathematical model analysis result is very small and the error is controlled within 1%. Simulation results demonstrate the accuracy and effectiveness of the overvoltage peak calculation method presented herein.
By using the method, the quantity of the fans in the direct current near zone is kept unchanged, and the equivalent impedance of the alternating current system 1 is changedAnd analyzing the relation between the system structure and the direct current fault overvoltage peak value.
The simulation results and calculation results of the overvoltage peaks caused by the direct current blocking and commutation failure faults under different system equivalent impedances are shown in tables 2 and 3 respectively. The voltage dynamics after system failure are shown in fig. 5 and 6.
Analysis shows that when a fault occurs in the DC system 1, the system equivalent impedance followsWhen increasing, the converter bus barThe overvoltage level may rise. Comparing the simulation result and the calculation result, the difference between the simulation result and the calculation result is found to be very small. Simulation results demonstrate the accuracy and effectiveness of the overvoltage calculation methods presented herein.
In one embodiment, a method for calculating a dc fault overvoltage peak value of a multi-dc external power system by wind-fire bundling is also provided: the method comprises the steps of establishing wind-fire bundling multiple direct-current power transmission system models of different direct-current near-area fans or different system structures, deriving a theoretical analysis method of direct-current fault overvoltage according to a formula, introducing a minimum reactive power calculation method to obtain a calculation method of direct-current fault overvoltage peak values, finally obtaining equivalent parameters of each system, and calculating the direct-current fault overvoltage peak values of the multiple direct-current external power transmission systems of different direct-current near-area fans and different system structures according to the overvoltage peak value calculation method.
By changing the equivalent impedance value of the system, different multi-DC external power transmission system scenes can be established, and finally, the number of fans in different DC near areas and the DC fault overvoltage peak value of the multi-DC external power transmission system with different system structures and bundled wind and fire can be calculated.
Referring to fig. 8, in one embodiment, there is also provided a multi-dc power-over-voltage peak calculation system for wind-fire bundling, comprising:
the model building unit 100 is configured to determine a converter bus overvoltage calculation model after a dc fault occurs in the multi-dc external power transmission system according to a plurality of voltages and a plurality of powers of the multi-dc external power transmission system including different numbers of fans in a dc near region;
a parameter calculation unit 200, configured to determine active power and reactive power consumed by a dc system in the multi-dc external power system under different fault types;
the peak value calculating unit 300 is configured to substitute active power and reactive power consumed by the dc system under different fault types into a converter bus overvoltage calculating model, and calculate a dc fault overvoltage peak value.
In some embodiments, a function or a module included in a system provided by the embodiments of the present disclosure may be used to perform a method described in the foregoing method embodiments, and a specific implementation of the function or the module included in the system may refer to the description of the foregoing method embodiments, which is not repeated herein for brevity.
The present invention also provides a computer readable storage medium having stored therein a computer program comprising program instructions which, when executed by a processor of an electronic device, cause the processor to perform a method of calculating a dc fault overvoltage peak value for a multi-dc power delivery system by wind fire bundling in any one of the possible ways described above.
The invention also provides an electronic device, comprising: a processor, a transmitting means, an input means, an output means and a memory for storing computer program code comprising computer instructions which, when executed by the processor, cause the electronic device to perform a method as any one of the possible implementations described above.
Referring to fig. 9, fig. 9 is a schematic diagram of a hardware structure of an electronic device according to an embodiment of the invention.
The electronic device 2 comprises a processor 21, a memory 22, input means 23, output means 24. The processor 21, memory 22, input device 23, and output device 24 are coupled by connectors including various interfaces, transmission lines or buses, etc., as are not limited by the present embodiments. It should be appreciated that in various embodiments of the invention, coupled is intended to mean interconnected by a particular means, including directly or indirectly through other devices, e.g., through various interfaces, transmission lines, buses, etc.
The processor 21 may be one or more graphics processors (graphics processing unit, GPUs), which may be single-core GPUs or multi-core GPUs in the case where the processor 21 is a GPU. Alternatively, the processor 21 may be a processor group formed by a plurality of GPUs, and the plurality of processors are coupled to each other through one or more buses. In the alternative, the processor may be another type of processor, and the embodiment of the invention is not limited.
Memory 22 may be used to store computer program instructions as well as various types of computer program code for performing aspects of the present invention. Optionally, the memory includes, but is not limited to, a random access memory (random access memory, RAM), a read-only memory (ROM), an erasable programmable read-only memory (erasable programmable read only memory, EPROM), or a portable read-only memory (compact disc read-only memory, CD-ROM) for associated instructions and data.
The input means 23 are for inputting data and/or signals and the output means 24 are for outputting data and/or signals. The output device 23 and the input device 24 may be separate devices or may be an integral device.
It will be appreciated that in embodiments of the present invention, the memory 22 may not only be used to store relevant instructions, but embodiments of the present invention are not limited to the specific data stored in the memory.
It will be appreciated that fig. 9 shows only a simplified design of an electronic device. In practical applications, the electronic device may further include other necessary elements, including but not limited to any number of input/output devices, processors, memories, etc., and all video parsing devices capable of implementing the embodiments of the present invention are within the scope of the present invention.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, and are not repeated herein. It will be further apparent to those skilled in the art that the descriptions of the various embodiments of the present invention are provided with emphasis, and that the same or similar parts may not be described in detail in different embodiments for convenience and brevity of description, and thus, parts not described in one embodiment or in detail may be referred to in description of other embodiments.
In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in the embodiments of the present invention may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit.
In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, produces a flow or function in accordance with embodiments of the present invention, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in or transmitted across a computer-readable storage medium. The computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by a wired (e.g., coaxial cable, fiber optic, digital subscriber line (digital subscriber line, DSL)), or wireless (e.g., infrared, wireless, microwave, etc.). The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains an integration of one or more available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a digital versatile disk (digital versatile disc, DVD)), or a semiconductor medium (e.g., a Solid State Disk (SSD)), or the like.
Those of ordinary skill in the art will appreciate that implementing all or part of the above-described method embodiments may be accomplished by a computer program to instruct related hardware, the program may be stored in a computer readable storage medium, and the program may include the above-described method embodiments when executed. And the aforementioned storage medium includes: a read-only memory (ROM) or a random access memory (random access memory, RAM), a magnetic disk or an optical disk, or the like.
Claims (5)
1. A method for calculating a DC fault overvoltage peak value of a multi-DC external power supply system by bundling wind and fire is characterized by comprising the following steps:
determining a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system according to a plurality of voltages and a plurality of powers of the multi-direct current external power transmission system with different fan numbers in a direct current near zone;
determining active power and reactive power consumed by a direct current system in the multi-direct current external power supply system under different fault types;
substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate a direct current fault overvoltage peak value;
the determining the converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system comprises the following steps:
calculating the system side voltage of the alternating current system after the direct current fault according to the voltage of the alternating current system after the fault and the active power and reactive power transmitted by the system side direction alternating current bus of the alternating current system after the fault; the method comprises the steps of,
calculating the voltage of the fan side of the alternating current system after the fault according to the voltage of the commutation bus of the alternating current system after the fault and the active power and the reactive power sent by the fan side after the fault;
the determining the converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system further comprises:
calculating the current alternating current system conversion bus voltage according to the active power and reactive power sent by the current alternating current system after the fault to the other alternating current system and the equivalent impedance connecting the current alternating current system and the other alternating current system;
calculating the active power sent out by the fan side after the fault according to the rated active power output of the fan of the alternating current system and the proportional coefficient of the active power output of the fan of the alternating current system during the low voltage ride through period;
calculating reactive power sent out by a fan side after a fault according to rated reactive power output of the fan of the alternating current system and a proportional coefficient of reactive power output of the fan of the alternating current system during low-voltage ride through;
according to the active power sent out by the wind turbine side of the AC system after the fault, the active power consumed by the DC system, the AC system after the fault sends out the sum of the active powers to other AC systems, and the active power sent by the system side converter bus of the AC system after the fault is calculated;
according to the reactive power sent out by the wind turbine side of the AC system after the fault, the reactive power sent out by the reactive compensation of the AC system after the fault and the sum of the reactive power sent out by the AC system after the fault to other AC systems, the reactive power consumed by the DC system calculates the reactive power transmitted by the lateral converter bus of the AC system after the fault;
and the reactive power sent by the reactive compensation of the AC system after the fault is in direct proportion to the voltage of the commutation bus of the AC system after the fault.
2. The method for calculating the dc fault overvoltage peak value of the multi-dc external power transmission system by using the wind fire bundling according to claim 1, wherein the determining the active power and the reactive power consumed by the dc system in the multi-dc external power transmission system under different fault types comprises:
when a direct current blocking fault occurs, the active power and the reactive power consumed by the direct current system are determined to be 0.
3. The method for calculating dc fault overvoltage peak value of a multiple dc external power transmission system by using a wind fire bundling according to claim 1, wherein the determining active power and reactive power consumed by a dc system in the multiple dc external power transmission system under different fault types further comprises:
when a commutation failure fault occurs, calculating the active power consumed by the direct current system according to the minimum value of the direct current and the minimum value of the direct current voltage after the fault;
and calculating reactive power consumed by the direct current system according to the direct current minimum value, the no-load direct current voltage and the direct current resistance after the fault.
4. The method for calculating the dc fault overvoltage peak value of the multi-dc external power transmission system by using the wind fire bundling according to claim 1, before determining the dc fault-after-dc converter bus overvoltage calculation model of the multi-dc external power transmission system, the method further comprises:
and changing the equivalent impedance of the system to obtain a plurality of direct-current external power transmission systems with different fans in the direct-current near areas.
5. A multi-dc power-over-voltage peak-over-voltage calculation system for wind-fire bundling for implementing the method of any one of claims 1 to 4, the system comprising:
the model construction unit is used for determining a converter bus overvoltage calculation model after the direct current fault of the multi-direct current external power transmission system according to the multi-direct current external power transmission system with different fans in the direct current near zone;
the parameter calculation unit is used for determining active power and reactive power consumed by a direct current system in the multi-direct current external power transmission system under different fault types;
and the peak value calculation unit is used for substituting the active power and the reactive power consumed by the direct current system under different fault types into the converter bus overvoltage calculation model to calculate the direct current fault overvoltage peak value.
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