CN111564840A - Power distribution network additional loss modeling and analyzing method under composite power quality disturbance - Google Patents

Power distribution network additional loss modeling and analyzing method under composite power quality disturbance Download PDF

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CN111564840A
CN111564840A CN202010474047.7A CN202010474047A CN111564840A CN 111564840 A CN111564840 A CN 111564840A CN 202010474047 A CN202010474047 A CN 202010474047A CN 111564840 A CN111564840 A CN 111564840A
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loss
distribution network
transformer
phase
power distribution
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肖驰
张卫东
辛昂倍
王蒙
洪福
郝杰
蔡英明
侯军
于文牮
刘震
刘腾
许春华
江丽
吕彬
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State Grid Corp of China SGCC
Weihai Power Supply Co of State Grid Shandong Electric Power Co Ltd
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Weihai Power Supply Co of State Grid Shandong Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

Abstract

The invention provides a modeling and analyzing method for additional loss of a power distribution network under composite power quality disturbance, which comprises the following steps: when the loss of a transformer and a power distribution network line of the power distribution network is calculated, the influence of harmonic waves, three-phase imbalance and voltage deviation is considered, dynamic harmonic wave imbalance and voltage deviation indexes are introduced, and the loss of power quality disturbance to key energy consumption equipment of the power distribution network is represented; by taking optimization of the network loss of the power distribution network as a target, key energy consumption equipment of the power distribution network is provided under three power quality disturbances of harmonic waves, three-phase imbalance and voltage deviation, and a basis can be provided for energy conservation and loss reduction of the power distribution network.

Description

Power distribution network additional loss modeling and analyzing method under composite power quality disturbance
Technical Field
The disclosure belongs to the technical field of power distribution network optimization control, and relates to a power distribution network additional loss modeling and analyzing method under composite power quality disturbance.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The loss analysis is a method for analyzing rationality of a network structure and an operation mode, scientificity of loss management of a power distribution network and loss key links in the power distribution network by calculating theoretical loss and comparing the theoretical loss with statistical loss on the basis of power network parameters such as load power, actual voltage values and the like. The research on the loss influence factors of the low-voltage distribution network goes through the development process from the initial simple qualitative induction and analysis of the loss influence factors to intellectualization, automation and multifunction. The technology of analysis and the realization of analysis function are greatly developed.
In the aspect of qualitative analysis, the influence factors of the loss of the power distribution network are divided into four categories, namely power grid planning and construction factors, power grid technical factors, operation management factors, external factors and the like, and the influence of each factor on the loss is analyzed respectively; in addition, a GIS system is introduced into the loss analysis of the power distribution network, software capable of realizing loss calculation and analysis is developed, and the practicability and functionality of loss analysis research are improved. However, in the aspect of quantitative analysis, a method for quantifying the influence degree of the loss influence factors on the overall loss of the distribution network is still lacked.
Disclosure of Invention
The method aims at optimizing the network loss of the power distribution network, provides an additional loss method under the composite power quality disturbance, gives key energy consumption equipment of the power distribution network under the consideration of three power quality disturbances of harmonic waves, three-phase imbalance and voltage deviation, and can provide a basis for energy conservation and loss reduction of the power distribution network.
According to some embodiments, the following technical scheme is adopted in the disclosure:
a modeling and analyzing method for additional loss of a power distribution network under composite power quality disturbance comprises the following steps:
when the loss of a transformer and a line of the power distribution network is calculated, the influence of harmonic waves, three-phase imbalance and voltage deviation is considered, dynamic harmonic wave imbalance and voltage deviation indexes are introduced, and the loss of the power quality disturbance to key energy consumption equipment of the power distribution network is represented.
As an alternative implementation mode, neglecting the influence of harmonic waves on the iron loss of the transformer, generating a skin effect and a proximity effect based on the influence of harmonic current of a transformer winding, constructing a harmonic equivalent model of the transformer according to equivalent resistance, harmonic impedance and harmonic inductive reactance of the transformer winding under corresponding subharmonic waves, and calculating the loss of the distribution transformer winding under the influence of the corresponding subharmonic waves;
the additional loss of the distribution transformer under the influence of each subharmonic is the sum of the losses of the windings of the distribution transformer under the influence of the corresponding subharmonic.
As an alternative embodiment, the harmonic parasitic loss of the line is calculated from the harmonic impedances of the line conductors based on the skin effect of the line under the influence of harmonic currents.
As an alternative embodiment, the three-phase imbalance includes both magnitude and phase angle aspects, which need to be considered simultaneously when calculating the additional three-phase imbalance loss model of the transformer.
As an alternative embodiment, only when the phase angle imbalance of the three-phase current occurs, no influence is exerted on the loss of the distribution transformer.
As an alternative embodiment, when the three-phase load unbalance of the power distribution network is calculated, the dynamic three-phase unbalance is used for calculation, namely, a time period to be calculated is divided into a plurality of small time periods, the three-phase unbalance is calculated in each small time period, and the dynamic value is used for replacing the original unchanged three-phase unbalance.
As an alternative embodiment, the transformer no-load loss percentage is used for representing the actual no-load loss change condition of the transformer, and the additional loss of the transformer and the loss of the distribution line under the voltage deviation are calculated.
As an alternative embodiment, under the disturbance of three composite power qualities of harmonic wave, three-phase imbalance and voltage deviation, the additional loss of the distribution transformer and the distribution line is considered from two aspects of fundamental wave loss and harmonic wave loss, the three-phase imbalance is decomposed into a three-phase imbalance coefficient of fundamental wave current and a three-phase imbalance coefficient of each subharmonic wave current, and an additional loss calculation model under the composite power disturbance is obtained through calculation.
A computer readable storage medium having stored therein a plurality of instructions adapted to be loaded by a processor of a terminal device and to execute the method for modeling and analyzing parasitic losses in a power distribution network under a composite power quality disturbance.
A terminal device comprising a processor and a computer readable storage medium, the processor being configured to implement instructions; the computer readable storage medium is used for storing a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing the method for modeling and analyzing the additional loss of the power distribution network under the composite power quality disturbance.
Compared with the prior art, the beneficial effect of this disclosure is:
and under the three power quality disturbances of harmonic waves, three-phase unbalance and voltage deviation, giving an additional loss calculation method for the distribution transformer and the distribution line, considering the additional loss of the distribution transformer and the distribution line from two aspects of fundamental wave loss and harmonic wave loss, and decomposing the three-phase unbalance into a three-phase unbalance coefficient of fundamental wave current and a three-phase unbalance coefficient of each subharmonic wave current. The method can quickly calculate the additional loss, realize the purposes of energy conservation and consumption reduction, effectively realize the work of energy conservation and loss reduction, and has the advantage of double control on the improvement of the power supply quality and the power supply benefit of the low-voltage distribution network.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
FIG. 1 is a harmonic equivalent model of a transformer;
the specific implementation mode is as follows:
the present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Aiming at optimizing the network loss of the power distribution network, an additional loss model under the composite power quality disturbance is provided, and under the three power quality disturbances of harmonic waves, three-phase imbalance and voltage deviation, an additional loss calculation formula of key energy consumption equipment of the power distribution network, namely a distribution transformer and a distribution line, is given out by the model.
The embodiment is mainly solved by the following technical scheme:
constructing harmonic wave additional loss model of main energy consumption equipment
The losses of low voltage distribution transformers are mainly composed of copper and iron losses. The influence of the harmonic wave on the transformer core is mainly to increase the hysteresis loss and the eddy current loss of the core, the iron loss difference is not large under the general condition and the fundamental wave condition, and the value is smaller compared with the copper loss of the transformer caused by the harmonic wave, so the influence of the harmonic wave on the iron loss of the transformer can be ignored. The transformer winding can generate skin effect and proximity effect under the influence of harmonic current, and further has influence on the resistance value of the winding, and the equivalent resistance of the transformer winding under the h-th harmonic can be expressed as:
Figure BDA0002515263680000051
in the formula: rThThe equivalent resistance, omega, of the transformer winding under the action of the h-th harmonic wave; rTThe equivalent resistance of the transformer winding in fundamental wave, omega;
Figure BDA0002515263680000052
which can be considered as a harmonic resistance correction factor.
In general, the leakage inductance of the transformer varies little and can be regarded as a constant, so the inductive reactance can be expressed as:
XTh＝jhXT(2)
in the formula: xThRepresenting h-th harmonic leakage reactance, omega, of a transformer winding; xTRepresenting the fundamental leakage reactance, omega, of the transformer winding. The harmonic impedance of the transformer can be expressed as:
Figure BDA0002515263680000061
therefore, the harmonic equivalent model of the transformer without considering the influence of the harmonic on the excitation branch of the transformer is shown in fig. 1.
The loss of the distribution transformer winding under the influence of the h-th harmonic can be calculated as follows:
Figure BDA0002515263680000062
in the formula: HRIhThe h-th harmonic content.
The loss calculation formula of the distribution transformer without considering the harmonic wave is as follows:
Figure BDA0002515263680000063
the additional loss of the distribution transformer under the influence of the h-th harmonic is as follows:
Figure BDA0002515263680000064
the additional loss of the distribution transformer under the influence of each harmonic is as follows:
Figure BDA0002515263680000065
the formula (7) is defined as the harmonic content HRIhA mathematical model of the parasitic losses of the characterized distribution transformer is provided that accounts for the effects of harmonics.
The method is similar to a transformer when analyzing the influence of harmonic waves on the additional loss of the line, and the skin effect can occur in the line due to the fact that the harmonic frequency is high; and as the harmonic frequency increases, the skin effect becomes more and more obvious, so a method for determining harmonic impedance with wider application is adopted. The harmonic impedances of the conductors are:
Figure BDA0002515263680000071
the harmonic parasitic loss calculation formula of the line thus translates into:
Figure BDA0002515263680000072
additional three-phase unbalanced loss model of main energy consumption equipment
Three-phase load in a power distribution network is asymmetric, so that unbalanced current can be generated in a system, and further, the transformer and a line in an unbalanced operation state generate more active loss, the output capacity of the transformer is reduced, the power supply quality is reduced, and other adverse effects are caused. The three-phase unbalance of the system not only increases the load loss of the transformer, but also influences the no-load loss of the transformer.
The asymmetry of the three-phase load will cause zero-sequence flux to occur at the low-voltage side of the transformer. However, due to the structural characteristics of the transformer, the primary side usually has no zero sequence current, which results in that the zero sequence current on the secondary side has no path, and only a loop is formed through the oil tank wall and the steel member of the transformer. The magnetic resistance of the transformer oil tank wall and the steel member is larger than that of the winding, and when zero-sequence current component flows through the steel member, larger magnetic hysteresis and eddy current loss are inevitably formed, so that additional heating of the steel member is caused.
The additional iron loss of the transformer is:
Figure BDA0002515263680000073
in the formula: i isocRepresenting a zero sequence current component of the secondary side of the transformer, A; rocAnd (3) representing the equivalent resistance omega of the zero-sequence current path at the secondary side of the transformer.
When the three-phase winding current amplitude is balanced, the transformer winding loss can be expressed as:
Figure BDA0002515263680000081
when the current amplitude of the three-phase winding is unbalanced, the winding loss of the transformer can be expressed as:
Figure BDA0002515263680000082
additional iron loss of the transformer is generally ignored when performing the three-phase unbalance loss calculation of the low-voltage distribution network, and β is taken into accountA+βB+βCAt 0, the parasitic loss of the low voltage distribution transformer can now be expressed as:
Figure BDA0002515263680000083
in the formula: kTRepresenting the three-phase unbalance coefficient of the transformer.
Equation (13) is an additional loss model of the distribution transformer under the condition of unbalanced three-phase current amplitude.
The current flowing through the neutral line is zero when the three-phase load is balanced, so there is no neutral loss. When the three-phase load is asymmetric, the phase line and the neutral line generate additional loss due to the existence of unbalanced current, and the loss is generated more when the unbalanced degree is larger.
The expression for neutral current can be derived from the vector method as follows:
Figure BDA0002515263680000084
Figure BDA0002515263680000085
the additional loss on the neutral line in unbalanced operation can be expressed as follows:
Figure BDA0002515263680000091
when the three-phase current is balanced, the loss on the phase line of the low-voltage distribution network can be calculated as follows:
Figure BDA0002515263680000092
when the three-phase current is unbalanced, the loss on the phase line of the low-voltage distribution network can be calculated as follows:
Figure BDA0002515263680000093
the phase line loss on the low-voltage distribution network line due to three-phase imbalance can be expressed as:
Figure BDA0002515263680000094
assuming that the neutral model is the same as the phase model, i.e. RL＝R0. When three-phase is unbalanced, the loss on the three-phase four-wire system low-voltage distribution network line can be expressed as:
Figure BDA0002515263680000095
order to
Figure BDA0002515263680000096
Is the three-phase amplitude unbalance coefficient of the line, then
Figure BDA0002515263680000097
Equation (21) is an additional loss model of the power distribution line in the case of an unbalanced three-phase current amplitude.
The three-phase imbalance comprises two aspects of amplitude and phase angle, and the loss calculation of the three-phase imbalance is only carried out on the basis of the imbalance of the magnitude of the current amplitude. In the actual operation of the system, the phase angle is also asymmetric, and the phase angle asymmetry in the three-phase four-wire low-voltage distribution network has no influence on each phase current, but can generate asymmetric current on a neutral line, thereby influencing the loss of the neutral line. Therefore, the neutral current needs to be recalculated to account for the phase angle asymmetry.
With the phase angle of phase a as a reference, the three-phase current can be expressed as:
Figure BDA0002515263680000101
the current flowing on the neutral line can be expressed as follows:
Figure BDA0002515263680000102
let m equal to 1+ βA+(1+βB)cosφB+(1+βC)cosφC，n＝(1+βB)sinφB+(1+βC)sinφCAnd then:
Figure BDA0002515263680000103
from the above formula, it can be seen that when the phase angles of the three-phase currents are asymmetric, even if the amplitudes of the three-phase currents are the same, the currents still flow through the neutral line, and further, the electric energy loss is generated.
And (4) calculating and analyzing the additional loss of the distribution transformer. The influence of the three-phase load asymmetry on the iron loss of the transformer is relatively small and can be ignored under normal conditions, and the additional loss of the transformer can be expressed as follows:
Figure BDA0002515263680000104
equation (25) is a model of the additional loss of the distribution transformer under the condition of unbalanced three-phase current amplitude and phase angle. As can be seen from (25), only the three-phase current phase angle imbalance has no effect on the loss of the distribution transformer.
And (4) calculating and analyzing the additional loss of the distribution line. When considering the current phase angle, the additional loss of the distribution line is:
Figure BDA0002515263680000111
wherein KL represents the three-phase unbalance coefficient of the line. When the model of the neutral line of the low-voltage distribution network is different from that of the phase line, the three-phase imbalance coefficient can be approximately expressed as:
Figure BDA0002515263680000112
the three-phase load unbalance of the power distribution network usually changes along with time, in order to estimate the loss of the power distribution network more accurately and enable a calculated value to be closer to an actual value, a concept of dynamic three-phase unbalance degree is introduced, namely a time period to be calculated is divided into a plurality of small time periods, the three-phase unbalance degree is calculated in each small time period, and the dynamic value is used for replacing the original unchanged three-phase unbalance degree.
For example, three-phase currents are respectively measured every hour within 24h of a representative day, and assuming that the three-phase currents do not change within an interval time period, the measured three-phase currents are respectively used for calculating the three-phase unbalance degree within each time period, so as to calculate the dynamic three-phase unbalance degree coefficients of the distribution transformer and the line:
Figure BDA0002515263680000113
Figure BDA0002515263680000114
in the formula βAi，βBi，βCiThe unbalance degree of the three-phase current for the ith period A, B, C;
mi＝1+βAi+(1+βBi)cosφBi+(1+βCi)cosφCi(30)
ni＝(1+βBi)sinφBi+(1+βCi)sinφCi(31)
φBi，φCithe phase angles of the phase currents in the i-th time segment B, C, respectively.
The three-phase unbalance coefficient in the formula changes along with time, is more consistent with the actual condition, and can more accurately describe the influence of three-phase unbalance on the loss of the low-voltage distribution network.
Establishing a power grid equipment additional voltage deviation loss model
The no-load loss of the transformer is usually regarded as a fixed value, but in actual operation the no-load loss of the transformer increases rapidly with increasing voltage. Setting rated no-load loss of transformer as PN0With an actual no-load loss of P0Then, the actual no-load loss variation condition of the transformer can be represented by the transformer no-load loss percentage, which is as follows:
Figure BDA0002515263680000121
the loss of the distribution transformer under voltage deviation is:
Figure BDA0002515263680000122
in the formula: u shapeNRated voltage of the distribution transformer, kV; p0Is the no-load loss, kW, of the distribution transformer at rated voltage; γ is a coefficient related to the transformer voltage deviation, where:
Figure BDA0002515263680000123
the losses of the distribution transformer, regardless of the voltage deviation, are:
Figure BDA0002515263680000124
the calculation formula of the additional loss of the transformer under the voltage deviation is as follows:
Figure BDA0002515263680000131
when the operating voltage of the transformer is higher than the rated voltage, the iron loss of the transformer is obviously increased, and the copper loss of the transformer is reduced along with the iron loss; in contrast, the iron and copper losses of the transformer will be significantly reduced and increased. During the load peak, the winding loss of the low-voltage distribution network is often larger than the no-load loss of the transformer, so that the voltage level of the distribution network is improved, and the purposes of energy conservation and loss reduction can be achieved. And the loss of the transformer winding is less than the no-load loss of the transformer in the load valley, and the loss of the power distribution network is increased by improving the voltage level of the power distribution network at the moment. Therefore, when the load is in a valley, the voltage level of the power distribution network is properly reduced, and the obvious effect of saving energy and reducing loss can be achieved. Therefore, the reasonable adjustment of the running voltage of the transformer has very important significance for energy conservation and loss reduction of the power distribution network.
When the load power is constant, the voltage and the current of the power transmission line are in inverse proportion, and the current flowing through the line can be reduced by increasing the voltage of the power transmission line, so that the power loss of the line is reduced; conversely, the line loss increases.
Neglecting the voltage deviation, the loss of the distribution line is as follows:
Figure BDA0002515263680000132
the loss of the distribution line under the voltage deviation is as follows:
Figure BDA0002515263680000133
the additional loss of the distribution line due to the voltage deviation obtainable from equations (37) and (38) is as follows:
Figure BDA0002515263680000141
therefore, equation (39) is a distribution line parasitic loss model under the voltage deviation.
Establishing an additional loss model under composite power quality disturbance
Under the disturbance of three composite electric energy qualities of harmonic wave, three-phase unbalance and voltage deviation, the additional losses of the distribution transformer and the distribution line are considered from two aspects of fundamental wave loss and harmonic wave loss, and the three-phase unbalance is decomposed into a three-phase unbalance coefficient of fundamental wave current and a three-phase unbalance coefficient of each subharmonic wave current, so that an additional loss calculation model under the composite electric energy disturbance is further obtained.
The available additional loss calculation formula of the distribution transformer under the composite power quality disturbance is as follows:
Figure BDA0002515263680000142
in the formula: kTihThe h-th harmonic three-phase unbalance coefficient is obtained in the ith period of the distribution transformer;
Figure BDA0002515263680000143
is h harmonic three-phase average current in the ith period; rhTeqIs the equivalent resistance of the distribution transformer winding under the h harmonic.
The calculation formula of the additional loss of the distribution line under the composite power quality disturbance is as follows:
Figure BDA0002515263680000151
in the formula: kLihThe h-order harmonic three-phase unbalance coefficient is the ith time interval of the distribution line;
Figure BDA0002515263680000155
is h harmonic three-phase average current in the ith period; rhLeqThe equivalent resistance of the distribution line under the h-th harmonic wave.
The three-phase unbalance coefficient is analyzed in the condition that the system does not contain harmonic waves by default, when the power distribution network contains the harmonic waves, the harmonic unbalance coefficient needs to be introduced, and the harmonic unbalance is calculated as follows:
Figure BDA0002515263680000152
in the formula βA.i.h、βB.i.h、βC.i.hThe current imbalance degree of h-th harmonic of three-phase current in the ith period A, B, C is respectively; i isi.h.pIs the h-th harmonic three-phase average current in the ith period, A; i isA.i.h、IB.i.h、IC.i.hRespectively, the h harmonic currents, a, of the three phases of the i-th period A, B, C.
The harmonic unbalance coefficient of the transformer is as follows:
Figure BDA0002515263680000153
when the power distribution network contains harmonic waves, the harmonic wave unbalance coefficient of the low-voltage power distribution network line can be expressed as follows:
Figure BDA0002515263680000154
in the formula βA.i.h、βB.i.h、βC.i.hThe current imbalance degree of h-th harmonic of three-phase current in the ith period A, B, C is respectively;
mi＝1+βA.i.h+(1+βB.i.h)cosφB.i.h+(1+βC.i.h)cosφC.i.h(45)
ni＝(1+βBi)sinφBi+(1+βCi)sinφCi(46)
in the formula: cos phiB.i.h，cosφC.i.hPhase angles of the three-phase h-harmonic currents in the i-th period A, B, C, respectively.
When the loss of a distribution network transformer and a distribution network line in a representative day is calculated, the influence of harmonic waves, three-phase imbalance and voltage deviation is considered, indexes such as dynamic harmonic wave imbalance degree and voltage deviation are introduced, and the loss of power quality disturbance to key energy consumption equipment of the distribution network is represented.
And simultaneously, under three power quality disturbances of harmonic waves, three-phase imbalance and voltage deviation, giving an additional loss calculation formula of the distribution transformer and the distribution line. The additional loss of the distribution transformer and the distribution line is considered from the two aspects of the fundamental wave loss and the harmonic wave loss, and the three-phase unbalance is decomposed into a three-phase unbalance coefficient of the fundamental wave current and a three-phase unbalance coefficient of each subharmonic wave current. The calculation speed is improved to a certain extent, and the network loss optimization of the low-voltage distribution network is facilitated.
As will be appreciated by one skilled in the art, embodiments of the present disclosure may be provided as a method, system, or computer program product. Accordingly, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.

Claims (10)

1. A modeling and analyzing method for additional loss of a power distribution network under composite power quality disturbance is characterized by comprising the following steps: the method comprises the following steps:
when the loss of a transformer and a line of the power distribution network is calculated, the influence of harmonic waves, three-phase imbalance and voltage deviation is considered, dynamic harmonic wave imbalance and voltage deviation indexes are introduced, and the loss of the power quality disturbance to key energy consumption equipment of the power distribution network is represented.
2. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: neglecting the influence of harmonic waves on the iron loss of the transformer, generating a skin effect and a proximity effect based on the influence of harmonic current of a transformer winding, constructing a harmonic equivalent model of the transformer according to equivalent resistance, harmonic impedance and harmonic inductive reactance of the transformer winding under corresponding subharmonic waves, and calculating the loss of the distribution transformer winding under the influence of the corresponding subharmonic waves;
the additional loss of the distribution transformer under the influence of each subharmonic is the sum of the losses of the windings of the distribution transformer under the influence of the corresponding subharmonic.
3. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: based on the skin effect of the line under the influence of harmonic current, the harmonic additional loss of the line is calculated according to the harmonic impedance of each time of the line conductor.
4. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: the three-phase imbalance comprises two aspects of amplitude and phase angle, and the amplitude and phase angle imbalance need to be considered simultaneously when calculating an additional three-phase imbalance loss model of the transformer.
5. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: and only when the phase angle of the three-phase current is unbalanced, the loss of the distribution transformer is not influenced.
6. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: when the three-phase load unbalance of the power distribution network is calculated, the dynamic three-phase unbalance is used for calculating, namely, a time period to be calculated is divided into a plurality of small time periods, the three-phase unbalance is calculated in each small time period, and the dynamic value is used for replacing the original unchanged three-phase unbalance.
7. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: and (4) representing the actual no-load loss change condition of the transformer by using the transformer no-load loss percentage, and calculating the additional loss of the transformer and the loss of the distribution line under the voltage deviation.
8. The method for modeling and analyzing additional loss of the power distribution network under the composite power quality disturbance as claimed in claim 1, wherein the method comprises the following steps: under the disturbance of three composite electric energy qualities of harmonic wave, three-phase unbalance and voltage deviation, the additional losses of the distribution transformer and the distribution line are considered from two aspects of fundamental wave loss and harmonic wave loss, the three-phase unbalance is decomposed into a three-phase unbalance coefficient of fundamental wave current and a three-phase unbalance coefficient of each subharmonic wave current, and an additional loss calculation model under the composite electric energy disturbance is obtained through calculation.
9. A computer-readable storage medium characterized by: stored with instructions adapted to be loaded by a processor of a terminal device and to perform a method for modeling and analyzing parasitic losses of a power distribution network under a composite power quality disturbance according to any one of claims 1 to 8.
10. A terminal device is characterized in that: the system comprises a processor and a computer readable storage medium, wherein the processor is used for realizing instructions; the computer readable storage medium is used for storing a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing the method for modeling and analyzing the additional loss of the power distribution network under the composite power quality disturbance according to any one of claims 1-8.
CN202010474047.7A 2020-05-29 2020-05-29 Power distribution network additional loss modeling and analyzing method under composite power quality disturbance Pending CN111564840A (en)

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