CN115754481A - Quantitative characterization method and system for positive sequence impedance of equivalent fault of new energy grid-connected converter station - Google Patents
Quantitative characterization method and system for positive sequence impedance of equivalent fault of new energy grid-connected converter station Download PDFInfo
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Abstract
The invention discloses a quantitative characterization method and a quantitative characterization system for positive sequence impedance of an equivalent fault of a new energy grid-connected converter station. Based on the positive sequence voltage amplitude and the phase change condition of the bus side of the converter station, the equivalent fault positive sequence impedance of the converter system corresponding to different fault types is calculated, and the quantitative representation of the equivalent positive sequence impedance of the converter system fault is realized to a certain extent. The method can provide theoretical guidance for quantitative characterization of fault characteristics of the converter system, adaptive analysis of protection and formulation of a new protection principle.
Description
Technical Field
The invention belongs to the technical field of relay protection, and particularly relates to a quantitative characterization method and system for positive sequence impedance of an equivalent fault of a new energy grid-connected converter station.
Background
The relay protection is used as a first line of defense of the power system, and acts according to the fault characteristics of the system. For traditional power frequency quantity protection such as sudden change directional element, current phase selection element and compensation type distance protection, the protection principle of the method depends on the equivalent sequence impedance characteristic of the system. However, in a new energy grid-connected system, the equivalent fault positive sequence impedance of the converter station is related to a plurality of factors such as a system control strategy, a fault type and a fault condition, which have a significant difference from the constant inductive sequence impedance of the traditional synchronous machine system, and also bring a huge challenge to a plurality of traditional protections depending on the impedance characteristics of the back side of the system. In order to guarantee the safe operation of the power system, it is necessary to deeply research the equivalent fault positive-sequence impedance characteristics of the new energy grid-connected converter.
At present, research aiming at the equivalent sequence impedance of the new energy grid-connected converter can be divided into qualitative analysis and quantitative analysis. Most of the previous research aiming at qualitative analysis depends on simulation, and the obtained conclusion is concise and lacks of universality; in the aspect of quantitative analysis, the influence of a certain influence factor on the value of the fault sequence impedance is analyzed through a control variable method in the past research, and the coupling relation among the influence factors is not fully considered, so that the deduced result often has a certain deviation from the actual result. In summary, a more intensive study is needed for the quantitative characterization problem of the fault equivalent positive sequence impedance of the new energy grid-connected converter station.
Disclosure of Invention
The invention provides a new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization method and system, which are used for solving the technical problems that the impedance characteristics of the existing new energy converter station equivalent fault positive sequence are unclear and quantitative characterization is difficult.
In a first aspect, the invention provides a quantitative characterization method for a positive sequence impedance of an equivalent fault of a new energy grid-connected converter station, which comprises the following steps: constructing an equivalent fault composite sequence network topology of the power system according to a fault ride-through control strategy of the grid-connected converter and boundary conditions corresponding to fault types; deducing a positive sequence voltage expression at a fault point of the power system based on the equivalent fault composite sequence network topology to obtain the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point; according to the amplitude and phase change conditions of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter, deducing the amplitude and phase change conditions of the positive sequence voltage at the bus side of the converter station under different fault scenes; according to the change conditions of the positive sequence voltage amplitude and the phase of the bus side of the converter station in different fault scenes, the equivalent fault positive sequence impedance of the converter station in different fault scenes is calculated, and the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
In a second aspect, the invention provides a new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization system, which includes: the building module is configured to build an equivalent fault composite sequence network topology of the power system according to a fault ride-through control strategy of the grid-connected converter and boundary conditions corresponding to fault types; the first derivation module is configured to derive a positive sequence voltage expression at a fault point of the power system based on the equivalent fault composite sequence network topology to obtain the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point; the second derivation module is configured to derive the change conditions of the amplitude and the phase of the positive sequence voltage at the bus side of the converter station under different fault scenes according to the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter; and the calculation module is configured to calculate the equivalent fault positive sequence impedance of the converter station under different fault scenes according to the change conditions of the positive sequence voltage amplitude and the phase at the bus side of the converter station under different fault scenes, so that the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
In a third aspect, an electronic device is provided, which includes: the quantitative characterization method comprises at least one processor and a memory which is in communication connection with the at least one processor, wherein the memory stores instructions which can be executed by the at least one processor, and the instructions are executed by the at least one processor, so that the at least one processor can execute the steps of the quantitative characterization method for the positive sequence impedance of the equivalent fault of the new energy grid-connected converter station according to any embodiment of the invention.
In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the program instructions, when executed by a processor, cause the processor to perform the steps of the quantitative characterization method for positive sequence impedance of equivalent fault of a new energy grid-connected converter station according to any one of the embodiments of the present invention.
According to the quantitative characterization method and system for the equivalent fault positive sequence impedance of the new energy grid-connected converter station, an equivalent composite sequence network of the system is established by combining a fault ride-through control strategy of a grid-connected converter and fault boundary conditions corresponding to different fault types, then a positive sequence voltage expression at a fault point is deduced by combining a weak feed characteristic of the converter system and a system fault composite sequence network topology, the positive sequence voltage expression at a converter station bus is deduced on the basis, amplitude phase change conditions of the positive sequence voltage at the converter station bus side under different fault scenes are researched, finally the equivalent positive sequence impedance of the converter system fault is calculated by using the deduced positive sequence voltage amplitude and phase change conditions at the converter station bus side, and quantitative characterization of the equivalent fault positive sequence impedance of the converter system is realized.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a flowchart of a new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization method according to an embodiment of the present invention;
fig. 2 is a failure diagram of a photovoltaic system according to an embodiment of the present invention;
fig. 3 is an equivalent composite sequence network diagram when a phase-a ground fault occurs in the system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an equivalent fault positive sequence impedance fluctuation region of the converter system when a three-phase symmetric fault occurs in the system according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an equivalent fault positive sequence impedance fluctuation region of the converter system in the event of a single-phase ground fault according to an embodiment of the present invention;
fig. 6 is a structural block diagram of a new energy grid-connected converter station equivalent fault positive-sequence impedance quantitative characterization system according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
Please refer to fig. 1, which shows a flowchart of a new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization method according to the present application.
As shown in fig. 1, the method for quantitatively characterizing the positive sequence impedance of the equivalent fault of the new energy grid-connected converter station specifically includes steps S101 to S104.
And S101, constructing an equivalent fault composite sequence network topology of the power system according to a fault ride-through control strategy of the grid-connected converter and boundary conditions corresponding to fault types.
And S102, deducing a positive sequence voltage expression at the fault point of the power system based on the equivalent fault composite sequence network topology to obtain the amplitude and phase change condition of the positive sequence voltage at the fault point of the power system, wherein the fault points of the power system comprise a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point.
In the present embodiment, among others, the positive sequence voltage expression at the power system slight three-phase symmetric fault point:
in the formula (I), the compound is shown in the specification,
is a positive sequence voltage at the fault point, R f In order to provide a transition resistance, the resistance,
is the positive sequence fault current flowing through the fault point,
the equivalent electromotive force of the conventional system at the opposite end of the converter station is obtained;
a positive sequence voltage expression at a severe three-phase symmetrical fault point of a power system is as follows:
in the formula, Z N1 Positive sequence system impedance, Z, for peer-to-peer conventional systems LN1 K is a proportionality coefficient, a constant, and is the positive sequence line impedance from the fault point to the opposite terminal bus.
And S103, deducing the amplitude and phase change conditions of the positive sequence voltage at the bus side of the converter station under different fault scenes according to the amplitude and phase change conditions of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter.
In this embodiment, an expression of the fault ride-through rule of the grid-connected converter is as follows:
in the formula i dref1 D-axis reference value, i, for positive sequence current at a common point of the converter station qref1 Q-axis reference value, P, for positive sequence current at a common point of a converter station ref As an active power reference value, I rate For rated current of the converter station, I max For maximum withstand current, U, of the converter station 1 Is the positive sequence voltage magnitude at the common point,
is the per unit value of the positive sequence voltage;
specifically, the expression of the positive sequence voltage at the bus side of the converter station is as follows:
in the formula (I), the compound is shown in the specification,
being a positive sequence voltage on the bus side of the converter station,
for positive sequence currents on the bus side of the converter station,
positive sequence voltage, Z, at the point of failure Ld1 Is the positive sequence line impedance from the point of failure to the converter station bus.
And step S104, calculating equivalent fault positive sequence impedance of the converter station under different fault scenes according to the change conditions of the positive sequence voltage amplitude and the phase at the bus side of the converter station under different fault scenes, so that the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
In this embodiment, the expression of the positive sequence impedance of the equivalent fault of the converter station is as follows:
in the formula (I), the compound is shown in the specification,
the fault component of the positive sequence voltage at the bus side of the converter station and the fault component of the positive sequence current at the bus side of the converter station are respectively.
In conclusion, according to the method of the embodiment, the equivalent composite sequence network of the system is established by combining the fault ride-through control strategy of the grid-connected converter and the fault boundary conditions corresponding to different fault types, then the positive sequence voltage expression at the fault point is deduced by combining the weak feedback characteristic of the converter system and the topology of the system fault composite sequence network, the positive sequence voltage expression at the bus of the converter station is deduced on the basis, the amplitude phase change condition of the positive sequence voltage at the bus side of the converter station under different fault scenes is researched, and finally the equivalent positive sequence impedance of the converter system fault is calculated by using the deduced amplitude and phase change condition of the positive sequence voltage at the bus side of the converter station, so that the quantitative representation of the equivalent positive sequence impedance of the converter system fault is realized.
Example two
The second embodiment of the invention also provides a new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization method, which is realized through software and/or hardware and specifically comprises the steps S1-S3.
S1, for the system shown in fig. 2, when a slight ABCG fault occurs in the system, the converter system may be equivalent to a negative resistance with a phase of-180 °. The positive sequence current of the peer-to-peer system and the positive sequence voltage at the protection installation at this time can be approximated as:
in the formula (I), the compound is shown in the specification,
for positive sequence current to the fault point for the peer-to-peer system,
is equivalent electromotive force, Z, of a conventional system at the opposite end of a converter station N1 Positive sequence system impedance, Z, for peer-to-peer conventional systems LN1 Is the positive sequence line impedance from the fault point to the opposite bus,
positive sequence voltage, positive sequence current, Z, respectively, at the bus side of the converter station Ld1 For positive sequence line impedance from the point of failure to the converter station bus,
positive sequence voltage, R, at the fault point f In order to provide a transition resistance, the resistance,
is the positive sequence current flowing through the fault point;
from the formula (2)
The phase is approximately 0, taking into account commutationThe system has a weak ability to provide short circuit current, so that when the system has a slight ABCG fault
Phase of (2) and
similarly, i.e., no large jump occurs, k can be considered to be u >At 0.8 time (k) u The ratio of the positive sequence voltage amplitude after the fault to the normal operating amplitude),
the value range of [ -30 degrees, 15 degrees °](
The phase change values before and after the positive sequence voltage fault).
When the system has serious ABCG faults, due to the weak feed of the converter system,
will be much larger than
At this time
And
can be expressed as:
as can be seen from the formula (3),
is approximately-80 deg.. In view of
Mainly composed of
To provide, can be considered as
The phase is approximately equal to-80 deg., and therefore
Is also approximately equal to-80 deg.. Due to the fact that
And is
Is small in amplitude and therefore
May be large, where k is considered to be u <At the time of 0.2, the temperature of the solution,
the range of values of (A) is [ -120 degrees, 90 degrees ]]And considering the positive sequence q-axis current reference value I of the converter control system when the voltage seriously drops qref Possibly approaching the maximum tolerant current I of the converter max Thus to I qref ＝1.05I rate And I qref ＝sin80°I max Two cases were analyzed (I) rate Rated current for the inverter). When it is 0.2<k u <At 0.8 time, at this time
Generally lags behind 0-80 deg. before the fault, but is weak due to the converter system's ability to supply short-circuit current (I is considered to be qref Maximum equal to 1.05I N ) Thus, therefore, it is
Is also out of phase with
With a large gap, it is considered herein that
The value range of [ -90 DEG, 30 DEG ]]。
And for single-phase earth faults, a current converter is arranged to realize fault ride-through by adopting current balance control. When a system has a serious failure, taking an a-phase grounding (AG) failure as an example, fig. 2 shows a failure complex sequence network thereof, and at this time
And
can be expressed as:
in the formula, Z LN2 、Z N2 Line negative sequence impedance from fault point to opposite terminal system bus and equivalent negative sequence impedance of opposite terminal system, Z ∑0 ＝(Z d0 +Z Ld0 )||(Z N0 +Z LN0 ) The subscript "0" is the zero sequence impedance of the corresponding variable.
In the formula (6), when the system voltage drop is not serious
The amplitude is large, namely R f When the value is close to 0
A severe drop similar to an ABCG failure does not occur. In the formula (6), when R is f Smaller, the positive and negative sequence impedance parameters can be considered approximately equal considering that the line and conventional system,
can be approximated by formula (7):
when AG high-resistance fault occurs in the system, the fault voltage drop is small,
can be approximated as:
the combination formula (8) is shown in the specification,
can be approximately represented by (9). And can be further deduced from the formula (9)
The phase of (a) does not jump greatly before and after a fault.
Based on the above analysis, for AG failures, it is considered that k is the time when u >At the time of 0.8, the temperature of the alloy is higher,
the value range of [ -30 degrees, 15 degrees °]When 0.4<k u <At the time of 0.8, the temperature of the alloy is higher,
the value range of [ -60 degrees, 30 degrees °]. The analysis process for the phase-to-phase fault and the phase-to-phase ground fault is similar to that for the single-phase ground fault, and the author does not give details.
S2, estimating by using positive sequence voltage and positive sequence current at common point of converter station
And
the amplitude phase relationship of (a). Wherein the positive sequence voltage and the positive sequence current at the common point of the converter stations satisfy a fault-ride-through guide shown by equation (10):
in the formula i dref1 D-axis reference value, i, for positive sequence current at a common point of the converter station qref1 Q-axis reference value, P, for positive sequence current at a common point of the converter station ref As an active power reference value, I rate Is the rated current of the inverter, I max For maximum withstand current of the converter, U 1 Is the positive sequence voltage magnitude at the common point,
is a per unit value of the positive sequence voltage.
According to the equation (10), the inverter can be equivalent to 1 voltage-controlled current source, and the positive sequence voltage and the positive sequence current satisfy a one-to-one correspondence relationship, so that the inverter can be operated according to the equation
Approximate estimation of amplitude and phase
Amplitude and phase.
S3, amplitude and phase changes of the positive sequence voltage on the bus side of the converter station in different fault scenes are deduced based on the step S1The condition and obtained in step S2
Method for calculating converter equivalent fault positive sequence impedance Z by using formula (11) d1 ：
In the formula (I), the compound is shown in the specification,
the fault component of the positive sequence voltage at the bus side of the converter station and the fault component of the positive sequence current at the bus side of the converter station are respectively.
The black area in fig. 4 shows the equivalent fault positive sequence impedance fluctuation area of the converter system with the voltage level of 220kV and the transmission capacity of 175MW when the system has three-phase symmetric fault. The black area in fig. 5 shows the equivalent positive sequence impedance fluctuation area of the inverter when the system has a single-phase ground fault.
Simulation verification:
a photovoltaic system with the transmission power of 175MW and the voltage level of 220kV is built in PSCAD/EMTDC software, the maximum withstand current of a converter is set to be 2 times of the rated current, and the topology of the system is shown in figure 1. Wherein the fundamental frequency of the system is 50Hz, the transformation ratio of the box transformer is 0.69kV/35kV, the transformation ratio of the main transformer is 35kV/220kV, and the main transformer adopts Y d Delta connection mode, transmission line length is 50km, simulation is carried out on the line by adopting a pi model, and positive sequence parameters of unit length are r1=0.06 omega/km, l 1 ＝0.127mH/km，c 0 ＝0.005μFkm，
Z N1 = (1.1+j6.0) omega. The sampling rate is set to 10kHz, and a full-wave Fourier algorithm is adopted to extract a power frequency signal.
Table 1 lists the calculated equivalent fault positive sequence impedances (using fault steady-state data) of the converter station when different faults occur inside the line, in combination with the fluctuation ranges of the converter fault positive sequence impedances shown in fig. 3 and 4,see Z in Table 1 d1 The calculation results are located inside or near the fluctuation region of the fault positive sequence impedance in fig. 3 and 4, so that the method can effectively realize quantitative characterization of the fault positive sequence impedance of the converter.
TABLE 1Z under different fault scenarios d1 Calculation results
EXAMPLE III
Please refer to fig. 6, which shows a structural block diagram of the new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization system of the present application.
As shown in fig. 6, the system 200 for quantitatively characterizing the positive sequence impedance of the equivalent fault of the new energy grid-connected converter station includes a building module 210, a first derivation module 220, a second derivation module 230, and a calculation module 240.
The construction module 210 is configured to construct an equivalent fault composite sequence network topology of the power system according to a fault ride-through control strategy of the grid-connected converter and boundary conditions corresponding to fault types; a first derivation module 220, configured to derive a positive sequence voltage expression at a fault point of the power system based on the equivalent fault composite sequence network topology, so as to obtain a change condition of an amplitude and a phase of a positive sequence voltage at the fault point of the power system, where the fault point of the power system includes a slight three-phase symmetric fault point and a severe three-phase symmetric fault point; the second derivation module 230 is configured to derive the variation conditions of the amplitude and the phase of the positive sequence voltage at the bus side of the converter station in different fault scenes according to the variation conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter; the calculating module 240 is configured to calculate the equivalent fault positive sequence impedance of the converter station under different fault scenes according to the change conditions of the positive sequence voltage amplitude and the phase at the bus side of the converter station under different fault scenes, so that the equivalent fault positive sequence impedance of the converter station is quantitatively characterized.
It should be understood that the modules recited in fig. 6 correspond to various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are also applicable to the modules in fig. 6, and are not described again here.
In other embodiments, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the program instructions, when executed by a processor, cause the processor to execute the method for quantitatively characterizing the positive-sequence impedance of the equivalent fault of the new energy grid-connected converter station in any of the method embodiments described above;
as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:
constructing an equivalent fault composite sequence network topology of the power system according to a fault crossing control strategy of the grid-connected converter and boundary conditions corresponding to fault types;
deducing a positive sequence voltage expression at a fault point of the power system based on the equivalent fault composite sequence network topology to obtain the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point;
deducing the change conditions of the amplitude and the phase of the positive sequence voltage at the bus side of the converter station under different fault scenes according to the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter;
according to the change conditions of the positive sequence voltage amplitude and the phase of the bus side of the converter station in different fault scenes, the equivalent fault positive sequence impedance of the converter station in different fault scenes is calculated, and the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
The computer-readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area can store data created according to the use of the new energy grid-connected converter station equivalent fault positive sequence impedance quantitative representation system and the like. Further, the computer-readable storage medium may include high speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the computer readable storage medium optionally includes a memory remotely located from the processor, and the remote memory may be connected to the new energy grid-connected converter station equivalent fault positive sequence impedance quantitative characterization system through a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 7, the electronic device includes: a processor 310 and a memory 320. The electronic device may further include: an input device 330 and an output device 340. The processor 310, memory 320, input device 330, and output device 340 may be connected by a bus or other means, as exemplified by the bus connection in fig. 7. The memory 320 is the computer-readable storage medium described above. The processor 310 executes various functional applications and data processing of the server by running the nonvolatile software program, instructions and modules stored in the memory 320, that is, the method for quantitatively characterizing the positive sequence impedance of the equivalent fault of the new energy grid-connected converter station in the embodiment of the method is realized. The input device 330 can receive input numerical or character information and generate key signal input related to user setting and function control of the new energy grid-connected converter station equivalent fault positive sequence impedance quantitative representation system. The output device 340 may include a display device such as a display screen.
The electronic equipment can execute the method provided by the embodiment of the invention and has the corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.
As an implementation manner, the electronic device is applied to a new energy grid-connected converter station equivalent fault positive-sequence impedance quantitative characterization system, is used for a client, and includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to cause the at least one processor to:
constructing an equivalent fault composite sequence network topology of the power system according to a fault crossing control strategy of the grid-connected converter and boundary conditions corresponding to fault types;
deducing a positive sequence voltage expression at the fault point of the power system based on the equivalent fault composite sequence network topology to obtain the amplitude and phase change condition of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point;
according to the amplitude and phase change conditions of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter, deducing the amplitude and phase change conditions of the positive sequence voltage at the bus side of the converter station under different fault scenes;
according to the change conditions of the positive sequence voltage amplitude and the phase of the bus side of the converter station in different fault scenes, the equivalent fault positive sequence impedance of the converter station in different fault scenes is calculated, and the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods of the various embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (8)
1. A quantitative characterization method for a new energy grid-connected converter station equivalent fault positive sequence impedance is characterized by comprising the following steps:
constructing an equivalent fault composite sequence network topology of the power system according to a fault crossing control strategy of the grid-connected converter and boundary conditions corresponding to fault types;
deducing a positive sequence voltage expression at the fault point of the power system based on the equivalent fault composite sequence network topology to obtain the amplitude and phase change condition of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point;
according to the amplitude and phase change conditions of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter, deducing the amplitude and phase change conditions of the positive sequence voltage at the bus side of the converter station under different fault scenes;
according to the change conditions of the positive sequence voltage amplitude and the phase of the bus side of the converter station in different fault scenes, the equivalent fault positive sequence impedance of the converter station in different fault scenes is calculated, and the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
2. The quantitative characterization method for the equivalent fault positive sequence impedance of the new energy grid-connected converter station according to claim 1, wherein a positive sequence voltage expression at a slight three-phase symmetrical fault point of the power system is as follows:
in the formula (I), the compound is shown in the specification,
is a positive sequence voltage at the fault point, R f In order to be the transition resistance, the resistance,
is the positive sequence fault current flowing through the fault point,
the equivalent electromotive force of the conventional system at the opposite end of the converter station is obtained;
a positive sequence voltage expression at a severe three-phase symmetrical fault point of a power system is as follows:
in the formula, Z N1 Positive sequence system impedance, Z, for peer-to-peer conventional systems LN1 K is a proportionality coefficient, and is a constant, for the positive sequence line impedance from the fault point to the opposite-end bus.
3. The quantitative characterization method for the new energy grid-connected converter station equivalent fault positive sequence impedance according to claim 1, wherein the expression of the converter station bus side positive sequence voltage is as follows:
in the formula (I), the compound is shown in the specification,
being a positive sequence voltage on the bus side of the converter station,
for positive sequence currents on the bus side of the converter station,
is positive sequence at fault pointVoltage, Z Ld1 Is the positive sequence line impedance from the point of failure to the converter station bus.
4. The quantitative characterization method for the equivalent fault positive sequence impedance of the new energy grid-connected converter station according to claim 1, wherein the expression of the fault ride-through guide rule of the grid-connected converter is as follows:
in the formula i dref1 D-axis reference value, i, for positive sequence current at common point of converter station qref1 Q-axis reference value, P, for positive sequence current at a common point of the converter station ref As an active power reference value, I rate Rated current of the converter, I max For maximum withstand current of the converter, U 1 Is the positive sequence voltage magnitude at the common point,
is a per unit value of the positive sequence voltage.
5. The quantitative characterization method for the new energy grid-connected converter station equivalent fault positive sequence impedance according to claim 1, wherein the converter station equivalent fault positive sequence impedance has an expression:
in the formula (I), the compound is shown in the specification,
the fault component of the positive sequence voltage at the bus side of the converter station and the fault component of the positive sequence current at the bus side of the converter station are respectively.
6. The utility model provides a new forms of energy are incorporated into power networks converter station equivalence trouble positive sequence impedance quantitative characterization system which characterized in that includes:
the building module is configured to build an equivalent fault composite sequence network topology of the power system according to a fault ride-through control strategy of the grid-connected converter and boundary conditions corresponding to fault types;
the first derivation module is configured to derive a positive sequence voltage expression at a fault point of the power system based on the equivalent fault composite sequence network topology to obtain the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system, wherein the fault point of the power system comprises a slight three-phase symmetrical fault point and a serious three-phase symmetrical fault point;
the second derivation module is configured to derive the change conditions of the amplitude and the phase of the positive sequence voltage at the bus side of the converter station under different fault scenes according to the change conditions of the amplitude and the phase of the positive sequence voltage at the fault point of the power system and the fault ride-through guide rule of the grid-connected converter;
and the calculation module is configured to calculate the equivalent fault positive sequence impedance of the converter station under different fault scenes according to the change conditions of the positive sequence voltage amplitude and the phase at the bus side of the converter station under different fault scenes, so that the equivalent fault positive sequence impedance of the converter station is quantitatively represented.
7. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any of claims 1 to 5.
8. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of any one of claims 1 to 5.
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