CN112383073A - Analysis method and analysis device for zero sequence current value in power distribution network and power grid monitoring terminal - Google Patents
Analysis method and analysis device for zero sequence current value in power distribution network and power grid monitoring terminal Download PDFInfo
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Abstract
The invention discloses an analysis method and an analysis device for a zero sequence current value in a power distribution network and a power grid monitoring terminal. Wherein, the method comprises the following steps: decomposing a plurality of phase sequences of an asymmetric three-phase system in a power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component; calculating a zero-sequence current component of the three-phase system based on the positive-sequence component, the negative-sequence component and the zero-sequence component; and determining a neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component. The invention solves the technical problems that the asymmetric current in the power grid cannot be effectively analyzed, the state of three-phase load unbalance of the power grid cannot be found in time and the safe operation of the power distribution network is easily influenced in the related technology.
Description
Technical Field
The invention relates to the technical field of power grid data processing, in particular to an analysis method and an analysis device for a zero sequence current value in a power distribution network and a power grid monitoring terminal.
Background
In the related art, in the actual operation of a power distribution network, the three-phase unbalanced operation of a distribution transformer area often occurs due to the fluctuation of user loads and the asymmetry of a large number of single-phase loads. In addition, the imbalance of the three-phase load is caused by the access of part of single-phase users to the high-power single-phase load, the non-timeliness of the power consumption of the single-phase load and the like.
The phase load balance is the basis of safe power supply, the three-phase load is unbalanced, the power supply efficiency of a line and a distribution transformer is reduced if the three-phase load is not balanced, and serious consequences such as burning of a certain phase lead, burning of a switch, even single-phase burning of the distribution transformer and the like can be caused if the heavy-load phase is overloaded. In the three-phase four-wire system distribution network, the asymmetric operation of three-phase load can produce a large amount of negative sequence currents and zero sequence current, threatens the safe operation of distribution network, influences the power supply quality, and the drawback of the asymmetric operation of three-phase load includes:
the first disadvantage is that the three-phase load is severely asymmetric, the neutral point potential is shifted, and the line voltage drop and power loss are greatly increased. The problems that a single-phase user connected with a heavy-load phase is easy to have low voltage, a lamp is not bright, the efficiency of an electric appliance is reduced, a small water pump is easy to burn and the like.
The second disadvantage is that for a single-phase user connected to a light load phase, the voltage of equipment is higher due to unbalanced three-phase load, which may cause insulation breakdown of the electrical appliance, shorten the service life of the electrical appliance or damage the electrical appliance.
The third drawback is that unbalanced voltage is generated due to unbalanced three-phase load, and voltage deviation is increased, so that zero sequence current is generated in a center line, and therefore line loss is increased.
Therefore, the neutral point voltage is shifted due to the three-phase imbalance, the voltage drop of one phase with a heavy load is obvious, and the voltage of one phase with a light load is raised. When the deviation is serious, the single-phase voltage of the transformer is raised and exceeds the limit, the insulation inside the transformer is damaged, and the transformer is burnt.
When the current of the three-phase unbalance of the current distribution line is calculated, the three-phase current is usually set to be phase symmetry and have a phase difference of 120 degrees, but when the load of the power distribution network is found to be unbalanced in actual site work, the amplitude and the phase of each phase of current are different under most conditions.
In the existing research method, a symmetrical component method is mostly used for three-phase asymmetrical current analysis, and for phase asymmetrical current, calculation of a multi-element nonlinear equation set is needed for obtaining a symmetrical component, so that the calculation process is complex and is not beneficial to being adopted in actual work.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The embodiment of the invention provides an analysis method and an analysis device for a zero sequence current value in a power distribution network and a power distribution network monitoring terminal, and aims to at least solve the technical problems that asymmetric current in the power distribution network cannot be effectively analyzed, the state of three-phase load imbalance of the power distribution network cannot be found in time and the safe operation of the power distribution network is easily influenced in the related technology.
According to an aspect of the embodiments of the present invention, there is provided a method for analyzing a zero sequence current value in a power distribution network, including: decomposing a plurality of phase sequences of an asymmetric three-phase system in a power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component; calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component, and the zero sequence component; and determining a neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
Optionally, the step of decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system to obtain a positive sequence component, a negative sequence component, and a zero sequence component includes: determining a plurality of asymmetrical phase current vectors in the power distribution network system by adopting a first preset formula, wherein the first preset formula is as follows:
Optionally, the step of calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component and the zero sequence component comprises: calculating a positive sequence component and a negative sequence component of each phase current; determining two equilateral triangles by taking a first vector side as a base side in a vector triangle formed by a plurality of phase current vectors; determining phasors formed by the triangle top points and the end points of the first phase as a positive sequence component and a zero sequence component; and calculating a zero-sequence current component corresponding to each phase current in the three-phase system based on the positive-sequence component and the zero-sequence component.
Optionally, the step of calculating a positive sequence component and a negative sequence component of each phase current comprises: determining a first phase A current; and calculating the positive sequence component and the negative sequence component of the phase A current by adopting a third preset formula, wherein the third preset formula is as follows:
optionally, the step of determining a neutral zero-sequence current value of the power distribution grid system based on the zero-sequence current component includes: drawing a vector quadrangle based on the two equilateral triangles; determining a first neutral point based on the vector quadrilateral; determining a second neutral point based on the vector triangle; connecting the first neutral point and the second neutral point, and determining a neutral line zero sequence current vector; and calculating the neutral line zero-sequence current value of the power distribution network system based on the neutral line zero-sequence current vector.
Optionally, after determining a neutral zero-sequence current value of the power distribution grid system based on the zero-sequence current component, the analysis method further includes: analyzing neutral line voltage deviation parameters of an asymmetric three-phase system in the power distribution network based on the neutral line zero sequence current value; and sending the neutral line zero sequence current value and the neutral line voltage deviation parameter to a preset monitoring terminal.
Optionally, the method for analyzing the zero sequence current value in the power distribution network is applied to a preset power distribution network monitoring system.
According to another aspect of the embodiments of the present invention, there is also provided an apparatus for analyzing a zero sequence current value in a power distribution network, including: the decomposition unit is used for decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component; a calculation unit for calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component and the zero sequence component; and the determining unit is used for determining the neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
Optionally, the decomposition unit comprises: the first determining module is configured to determine a plurality of asymmetric phase current vectors in the power distribution network system by using a first preset formula, where the first preset formula is:
Optionally, the computing unit comprises: the first calculation module is used for calculating a positive sequence component and a negative sequence component of each phase current; determining two equilateral triangles by taking a first vector side as a base side in a vector triangle formed by a plurality of phase current vectors; the second determining module is used for determining phasor formed by the vertex of the triangle and the endpoint of the first phase into a positive sequence component and a zero sequence component; and the second calculation module is used for calculating a zero-sequence current component corresponding to each phase current in the three-phase system based on the positive-sequence component and the zero-sequence component.
Optionally, the first computing module comprises: a first determination submodule for determining a first phase A current; the first calculation submodule is used for calculating the positive sequence component and the negative sequence component of the A-phase current by adopting a third preset formula, wherein the third preset formula is as follows:
optionally, the determining unit includes: the drawing module is used for drawing a vector quadrangle based on the two equilateral triangles; determining a first neutral point based on the vector quadrilateral; a third determining module for determining a second neutral point based on the vector triangle; the fourth determining module is used for connecting the first neutral point and the second neutral point and determining a neutral line zero-sequence current vector; and the third calculation module is used for calculating the neutral line zero-sequence current value of the power distribution network system based on the neutral line zero-sequence current vector.
Optionally, the analysis device further comprises: the analysis module is used for analyzing neutral line voltage deviation parameters of an asymmetric three-phase system in the power distribution network based on the neutral line zero sequence current value after the neutral line zero sequence current value of the power distribution network system is determined based on the zero sequence current component; and the transmitting module is used for transmitting the neutral line zero sequence current value and the neutral line voltage deviation parameter to a preset monitoring terminal.
Optionally, the method for analyzing the zero sequence current value in the power distribution network is applied to a preset power distribution network monitoring system.
According to another aspect of the embodiments of the present invention, there is also provided a power grid monitoring device, including: a processor; and a memory for storing executable instructions of the processor; wherein the processor is configured to execute the method for analyzing the zero sequence current value in the power distribution network according to any one of the above items through executing the executable instructions.
According to another aspect of the embodiments of the present invention, a computer-readable storage medium is further provided, where the computer-readable storage medium includes a stored computer program, and when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute any one of the above methods for analyzing the zero-sequence current value in the power distribution network.
In the embodiment of the invention, a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system are decomposed to obtain a positive sequence component, a negative sequence component and a zero sequence component, the zero sequence current component of the three-phase system is calculated based on the positive sequence component, the negative sequence component and the zero sequence component, and the zero sequence current value of a neutral line of the power distribution network system is determined based on the zero sequence current component. In the embodiment, when the power distribution network system is asymmetric (indicating that the three-phase current amplitude phase is asymmetric), each sequence component of the asymmetric current and the neutral zero sequence current can be obtained by analysis, and the asymmetric current in the power grid can be quickly analyzed without performing complex nonlinear equation set calculation, so that the technical problems that the asymmetric current in the power grid cannot be effectively analyzed, the state of three-phase load imbalance of the power grid cannot be found in time and the safe operation of the power distribution network is easily influenced in the related technology are solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is a flowchart of an alternative method for analyzing zero sequence current values in a power distribution network according to an embodiment of the present invention;
fig. 2 is an alternative three-phase asymmetric current vector diagram for a power distribution network in accordance with an embodiment of the present invention;
fig. 3 is an alternative three-phase asymmetric current vector diagram for a power distribution network in accordance with an embodiment of the present invention;
fig. 4 is an alternative three-phase asymmetric transformation current vector diagram of a power distribution network according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an alternative analysis apparatus for zero sequence current values in a power distribution network according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, 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 only a part of the embodiments of the present invention, and not all of the embodiments. 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.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
At present, a three-phase four-wire system power supply is generally adopted in a power distribution network, a transformer used in the power distribution network adopts a connection mode of Dyn11, and when the phase and the amplitude of a three-phase load at the outlet of a low-voltage side of the transformer are symmetrical, no current flows on a central line. However, in practice, three phases are not completely balanced, so that the sum of three-phase current vectors on the distribution secondary winding side is not 0, and the voltage drop on the neutral line caused by the generated unbalanced current may cause the potential of the neutral point of the secondary side line of the transformer to shift.
According to the loop current method, a first formula is adopted to indicate the zero sequence current flowing through the neutral line, wherein the first formula is as follows:
IOO'＝-(IA+IB+IC)＝UO'(Ya+Yb+Yc)-(Ua0Ya+Ub0Yb+Uc0Yc) (1)
indicating the resulting neutral offset voltage using a second formula, wherein the second formula is:
in the above formula, UAO、UBO、UCOThree-phase voltage at the low-voltage side of the distribution transformer is respectively; y isa、Yb、Yc、YNRespectively three-phase load containing lead and zero line admittance.
Suppose UAO、UBO、UCOThree phases are symmetrical, each phase is a resistive load, with UAOIs a reference vector, then Yb＝KbYa，Yc＝Kc Ya，YN＝KN Ya. When three phases are unbalanced and three-phase load is not uniform, Kb≠Kc≠1。
The new neutral offset voltage is represented again using a third formula
Transforming into a fourth formula by the third formula, wherein the fourth formula
The analysis by the formula can obtain:
1) impedance Z of zero lineNLower than the load impedance, KNVery large, UAO' the value is small and the neutral point voltage is not greatly shifted.
2) But if the zero line impedance ZNGreater than the load impedance, i.e. KNVery small, UAOThe value of' is large and the neutral point voltage shifts significantly. In extreme cases, the zero line is broken, when Z isNThe value approaches infinity, KNIs very close to 0, UOOThe' value will be large and the phase voltage may rise significantly, possibly causing equipment burnout.
Therefore, the neutral point voltage is shifted due to the three-phase imbalance, the voltage drop of one phase with a heavy load is obvious, and the voltage of one phase with a light load is raised. When the deviation is serious, the single-phase voltage of the transformer is raised and exceeds the limit, the insulation inside the transformer is damaged, and the transformer is burnt.
Therefore, the invention provides an analysis method of the zero sequence current value in the power distribution network, and the unbalanced zero sequence current of the three-phase current of the power distribution network can be calculated based on a vector analysis method. Through vector analysis, each sequence component in the symmetrical component method can be obtained quickly, the three-phase unbalance degree can be analyzed, and the neutral line unbalance current can be obtained.
The invention provides a double-triangle vector analysis method, which is characterized in that when three-phase current amplitude phases are all asymmetric, each sequence component of asymmetric current is obtained through vector analysis based on the auxiliary effect of an equilateral triangle; meanwhile, the zero sequence current of the central line and the neutral line voltage deviation result are obtained by a double-triangle vector analysis method. The present invention will be described in detail with reference to examples.
Example one
According to an embodiment of the present invention, an embodiment of a method for analyzing a zero sequence current value in a power distribution network is provided, it should be noted that the steps illustrated in the flowchart of the drawings may be executed in a computer system such as a set of computer executable instructions, and although a logical order is illustrated in the flowchart, in some cases, the steps illustrated or described may be executed in an order different from that here.
Fig. 1 is a flowchart of an alternative method for analyzing a zero sequence current value in a power distribution network according to an embodiment of the present invention, as shown in fig. 1, the method includes the following steps:
step S102, decomposing a plurality of phase sequences of an asymmetric three-phase system in a power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component;
step S104, calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component and the zero sequence component;
and S106, determining a neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
Through the steps, a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system can be decomposed to obtain a positive sequence component, a negative sequence component and a zero sequence component, the zero sequence current component of the three-phase system is calculated based on the positive sequence component, the negative sequence component and the zero sequence component, and the zero sequence current value of a neutral line of the power distribution network system is determined based on the zero sequence current component. In the embodiment, when the power distribution network system is asymmetric (indicating that the three-phase current amplitude phase is asymmetric), each sequence component of the asymmetric current and the neutral zero sequence current can be obtained by analysis, and the asymmetric current in the power grid can be quickly analyzed without performing complex nonlinear equation set calculation, so that the technical problems that the asymmetric current in the power grid cannot be effectively analyzed, the state of three-phase load imbalance of the power grid cannot be found in time and the safe operation of the power distribution network is easily influenced in the related technology are solved.
Optionally, the step of decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system to obtain a positive sequence component, a negative sequence component, and a zero sequence component includes: a plurality of asymmetrical phase current vectors in the power distribution network system are determined by adopting a first preset formula, wherein the first preset formula is as follows:
The above a may refer to the horizontal phase, and B and C indicate the other phases at 120 degrees to a, respectively.
FIG. 2 is an alternative three-phase asymmetric current vector diagram for a power distribution network according to an embodiment of the present invention, shown in FIG. 2, with a set of asymmetric phase current vectors I in the power distribution networkA、IB、ICLine current is IBA、ICB、IACIn which IA、IB、ICThe amplitudes and phases of the two phases are different, and only the frequencies are the same.
For asymmetrical phase current vector IA、IB、ICExpressed by the following fifth formula:
the asymmetric three-phase system is decomposed into the superposition of three independent symmetric systems with positive, negative and zero phase sequences respectively by a symmetric component method.
The phase current vector after transformation, each sequence component and the value a are respectively expressed by the following sixth formula, seventh formula and eighth formula, wherein the sixth formula is as follows:
the seventh formula is:
the eighth formula is:
in the above calculation, since I1、I2、I0The amplitude needs to be in accordance with IA、IB、ICThe three phasors with different amplitudes and different phases are searched for the proper symmetrical components by adopting a vector analysis method in the embodiment of the invention.
Optionally, the step of calculating the zero-sequence current component of the three-phase system based on the positive-sequence component, the negative-sequence component, and the zero-sequence component includes: calculating a positive sequence component and a negative sequence component of each phase current; determining two equilateral triangles by taking a first vector side as a base side in a vector triangle formed by a plurality of phase current vectors; determining phasors formed by the triangle top points and the end points of the first phase as a positive sequence component and a zero sequence component; and calculating a zero-sequence current component corresponding to each phase current in the three-phase system based on the positive-sequence component and the zero-sequence component.
In an embodiment of the present invention, the step of calculating the positive sequence component and the negative sequence component of each phase current includes: determining a first phase A current; and calculating the positive sequence component and the negative sequence component of the phase A current by adopting a third preset formula, wherein the third preset formula is as follows:
taking the phase A as a first phase, the phase B as a second phase and the phase C as a third phase, obtaining a positive sequence component and a negative sequence component of the phase A current through transformation, and expressing the positive sequence component and the negative sequence component by adopting a ninth formula, wherein the ninth formula is as follows:
using a tenth formula to represent the vector IA、IB、ICInstead of the result of the interphase current superposition calculation, the tenth formula is:
after transforming the tenth formula, an eleventh formula may be obtained:
optionally, the step of determining the zero-sequence current value of the neutral line of the power distribution grid system based on the zero-sequence current component includes: drawing a vector quadrangle based on the two equilateral triangles; determining a first neutral point based on the vector quadrilateral; determining a second neutral point based on the vector triangle; connecting the first neutral point and the second neutral point, and determining a neutral line zero-sequence current vector; and calculating the neutral line zero-sequence current value of the power distribution network system based on the neutral line zero-sequence current vector.
For example, to find the vector 3A1And 3A2In the linear vector triangle, only I is neededCBMaking 2 equilateral triangles delta KMN for the base1And Δ KMN2I.e. the triangle apex and IAThe phasor formed by the end points is the positive sequence component and the zero sequence component, and the positive sequence component and the zero sequence component are expressed by a twelfth formula:
fig. 3 is an alternative three-phase asymmetric current vector diagram for a power distribution network according to an embodiment of the present invention, the vector diagram including two equilateral triangles Δ KMN1And Δ KMN2。
Based on the vector diagram shown in fig. 3, the component of the a zero-sequence current is obtained, and the zero-sequence current is calculated by using a thirteenth formula:
fig. 4 is an alternative three-phase asymmetric transformation current vector diagram of a power distribution network according to an embodiment of the present invention, where the vector diagram is a parallelogram, and the parallelogram is a vector IAB、ICBDrawn on both sides, the vector PO' may be equal to (I)AB+ICB)/3. Therefore, when the point O' is connected to the point O, the zero-sequence current vector of the neutral line is obtained, and the zero-sequence current value of the neutral line is obtained by calculating a fourteenth formula, where the fourteenth formula is:
as can be seen from fig. 4, if the point O' is at the center of gravity of the line vector triangle, the zero sequence component of the phase vector system is equal to zero. When the line vector system is a symmetric system, the negative sequence component of the phase vector system is equal to zero.
In an embodiment of the present invention, after determining the zero-sequence current value of the neutral line of the power distribution grid system based on the zero-sequence current component, the analysis method further includes: analyzing neutral line voltage deviation parameters of an asymmetric three-phase system in the power distribution network based on the neutral line zero sequence current value; and sending the zero sequence current value of the neutral line and the neutral line voltage deviation parameter to a preset monitoring terminal.
Optionally, the method for analyzing the zero sequence current value in the power distribution network is applied to a preset power distribution network monitoring system.
As can be seen from the graphical solution, the positive and negative sequence components decomposed by the phase vectors are invariant, regardless of the change of the phase vectors, provided that the line vector (interphase vector) system is invariant. Thus, there is only a difference in zero sequence components between the line vector system and the corresponding phase vector system.
By the embodiment, in three-phase unbalanced currents with unequal phase angles and amplitudes, vector relationships among the currents can be analyzed, equilateral triangles are made to assist vector analysis, positive sequence, negative sequence and zero sequence component values can be conveniently obtained, neutral zero sequence current is obtained, complex nonlinear equation set calculation is not needed, analysis speed of the neutral zero sequence current value is accelerated, monitoring accuracy of three-phase unbalance is improved, and safety of a power grid is improved.
Example two
Fig. 5 is a schematic diagram of an alternative analysis apparatus for zero sequence current values in a power distribution network according to an embodiment of the present invention, and as shown in fig. 5, the analysis apparatus may include: a decomposition unit 51, a calculation unit 53, a determination unit 55, wherein,
the decomposition unit 51 is used for decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component;
a calculating unit 53, configured to calculate a zero-sequence current component of the three-phase system based on the positive-sequence component, the negative-sequence component, and the zero-sequence component;
and the determining unit 55 is used for determining the neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
The device for analyzing the zero sequence current value in the power distribution network can decompose a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system through the decomposition unit 51 to obtain a positive sequence component, a negative sequence component and a zero sequence component, calculate the zero sequence current component of the three-phase system through the calculation unit 53 based on the positive sequence component, the negative sequence component and the zero sequence component, and determine the neutral zero sequence current value of the power distribution network system through the determination unit 55 based on the zero sequence current component. In the embodiment, when the power distribution network system is asymmetric (indicating that the three-phase current amplitude phase is asymmetric), each sequence component of the asymmetric current and the neutral zero sequence current can be obtained by analysis, and the asymmetric current in the power grid can be quickly analyzed without performing complex nonlinear equation set calculation, so that the technical problems that the asymmetric current in the power grid cannot be effectively analyzed, the state of three-phase load imbalance of the power grid cannot be found in time and the safe operation of the power distribution network is easily influenced in the related technology are solved.
Optionally, the decomposition unit includes: the first determining module is used for determining a plurality of asymmetrical phase current vectors in the power distribution network system by adopting a first preset formula, wherein the first preset formula is as follows:
optionally, the computing unit includes: the first calculation module is used for calculating a positive sequence component and a negative sequence component of each phase current; determining two equilateral triangles by taking a first vector side as a base side in a vector triangle formed by a plurality of phase current vectors; the second determining module is used for determining phasor formed by the vertex of the triangle and the endpoint of the first phase into a positive sequence component and a zero sequence component; and the second calculation module is used for calculating the zero-sequence current component corresponding to each phase current in the three-phase system based on the positive-sequence component and the zero-sequence component.
Alternatively, the first computing module comprises: a first determination submodule for determining a first phase A current; the first calculation submodule is used for calculating the positive sequence component and the negative sequence component of the A-phase current by adopting a third preset formula, wherein the third preset formula is as follows:
in an embodiment of the present invention, the determining unit includes: the drawing module is used for drawing a vector quadrangle based on the two equilateral triangles; determining a first neutral point based on the vector quadrilateral; a third determination module for determining a second neutral point based on the vector triangle; the fourth determining module is used for connecting the first neutral point and the second neutral point and determining a zero-sequence current vector of the neutral line; and the third calculation module is used for calculating the neutral line zero-sequence current value of the power distribution network system based on the neutral line zero-sequence current vector.
Optionally, the analysis device further comprises: the analysis module is used for analyzing neutral line voltage offset parameters of an asymmetric three-phase system in the power distribution network based on the neutral line zero sequence current value after the neutral line zero sequence current value of the power distribution network system is determined based on the zero sequence current component; and the transmitting module is used for transmitting the neutral line zero sequence current value and the neutral line voltage deviation parameter to a preset monitoring terminal.
Optionally, the method for analyzing the zero sequence current value in the power distribution network is applied to a preset power distribution network monitoring system.
The analyzing device for the zero sequence current value in the power distribution network may further include a processor and a memory, where the decomposition unit 51, the calculation unit 53, the determination unit 55, and the like are stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions.
The processor comprises a kernel, and the kernel calls a corresponding program unit from the memory. One or more than one kernel can be set, and the neutral line zero-sequence current value of the power distribution network system is determined based on the zero-sequence current component by adjusting kernel parameters.
The memory may include volatile memory in a computer readable medium, Random Access Memory (RAM) and/or nonvolatile memory such as Read Only Memory (ROM) or flash memory (flash RAM), and the memory includes at least one memory chip.
According to another aspect of the embodiments of the present invention, there is also provided a power grid monitoring device, including: a processor; and a memory for storing executable instructions for the processor; wherein the processor is configured to execute the method for analyzing the zero sequence current value in the power distribution network according to any one of the above items through executing the executable instructions.
According to another aspect of the embodiments of the present invention, there is further provided a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to perform any one of the above methods for analyzing the zero-sequence current value in the power distribution network.
The present application further provides a computer program product adapted to perform a program for initializing the following method steps when executed on a data processing device: decomposing a plurality of phase sequences of an asymmetric three-phase system in a power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component; calculating a zero-sequence current component of the three-phase system based on the positive-sequence component, the negative-sequence component and the zero-sequence component; and determining a neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for analyzing a zero sequence current value in a power distribution network is characterized by comprising the following steps:
decomposing a plurality of phase sequences of an asymmetric three-phase system in a power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component;
calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component, and the zero sequence component;
and determining a neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
2. The analysis method according to claim 1, wherein the step of decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution grid system to obtain a positive sequence component, a negative sequence component and a zero sequence component comprises:
determining a plurality of asymmetrical phase current vectors in the power distribution network system by adopting a first preset formula, wherein the first preset formula is as follows:
decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system by adopting a second preset formula to obtain a positive sequence component, a negative sequence component and a zero sequence component, wherein the second preset formula is as follows:
3. The analysis method according to claim 2, wherein the step of calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component and the zero sequence component comprises:
calculating a positive sequence component and a negative sequence component of each phase current;
determining two equilateral triangles by taking a first vector side as a base side in a vector triangle formed by a plurality of phase current vectors;
determining phasors formed by the triangle top points and the end points of the first phase as a positive sequence component and a zero sequence component;
and calculating a zero-sequence current component corresponding to each phase current in the three-phase system based on the positive-sequence component and the zero-sequence component.
4. The analysis method according to claim 3, wherein the step of calculating the positive sequence component and the negative sequence component of each phase current comprises:
determining a first phase A current;
and calculating the positive sequence component and the negative sequence component of the phase A current by adopting a third preset formula, wherein the third preset formula is as follows:
5. the analysis method of claim 3, wherein the step of determining a neutral zero sequence current value of the power distribution grid system based on the zero sequence current component comprises:
drawing a vector quadrangle based on the two equilateral triangles;
determining a first neutral point based on the vector quadrilateral;
determining a second neutral point based on the vector triangle;
connecting the first neutral point and the second neutral point, and determining a neutral line zero sequence current vector;
and calculating the neutral line zero-sequence current value of the power distribution network system based on the neutral line zero-sequence current vector.
6. The analysis method of claim 5, wherein after determining a neutral zero sequence current value of the power distribution grid system based on the zero sequence current component, the analysis method further comprises:
analyzing neutral line voltage deviation parameters of an asymmetric three-phase system in the power distribution network based on the neutral line zero sequence current value;
and sending the neutral line zero sequence current value and the neutral line voltage deviation parameter to a preset monitoring terminal.
7. The analysis method according to any one of claims 1 to 6, wherein the analysis method of the zero sequence current value in the power distribution network is applied to a preset power distribution network monitoring system.
8. The utility model provides an analytical equipment of zero sequence current value in distribution network which characterized in that includes:
the decomposition unit is used for decomposing a plurality of phase sequences of an asymmetric three-phase system in the power distribution network system to obtain a positive sequence component, a negative sequence component and a zero sequence component;
a calculation unit for calculating a zero sequence current component of the three-phase system based on the positive sequence component, the negative sequence component and the zero sequence component;
and the determining unit is used for determining the neutral line zero-sequence current value of the power distribution network system based on the zero-sequence current component.
9. A power grid monitoring device, comprising:
a processor; and
a memory for storing executable instructions of the processor;
wherein the processor is configured to perform the method of analyzing zero sequence current values in an electrical distribution network of any one of claims 1 to 7 via execution of the executable instructions.
10. A computer-readable storage medium, comprising a stored computer program, wherein when the computer program runs, the computer-readable storage medium controls an apparatus to execute the method for analyzing the zero-sequence current value in the power distribution network according to any one of claims 1 to 7.
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