CN115032450B - Harmonic evaluation method of multi-pulse rectifier under non-ideal condition - Google Patents

Harmonic evaluation method of multi-pulse rectifier under non-ideal condition Download PDF

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CN115032450B
CN115032450B CN202210972065.7A CN202210972065A CN115032450B CN 115032450 B CN115032450 B CN 115032450B CN 202210972065 A CN202210972065 A CN 202210972065A CN 115032450 B CN115032450 B CN 115032450B
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CN115032450A (en
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孙媛媛
李亚辉
许庆燊
李博文
徐龙威
张安彬
庄静茹
路彤
徐恭德
刘振
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Shandong University
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Abstract

The application belongs to the technical field of power electronics, and particularly relates to a harmonic evaluation method of a multi-pulse rectifier under a non-ideal condition, which comprises the following steps: obtaining fundamental voltage and harmonic voltage magnitude values on the power grid side of the multi-pulse rectifier under non-ideal conditions, and fundamental voltage and harmonic voltage magnitude values on the rectifier side; calculating a trigger angle and a conduction angle of a basic unit of the rectification circuit, and constructing a mapping relation between the voltage of the side-group wave of the power grid and the trigger angle and the conduction angle; determining a voltage modulation relation and a current modulation relation of a basic unit of the rectifying circuit under a non-ideal condition; calculating the voltage and current of the AC-DC side of the basic unit of the rectifying circuit; obtaining side harmonic current and harmonic current of the power grid, and constructing a harmonic coupling model representing the relation between side harmonic voltage and harmonic voltage of the power grid and fundamental current and harmonic current; and correcting the voltage magnitude of the fundamental wave on the side of the power grid, determining the coupling relation between the phase current and the phase voltage, and realizing the harmonic evaluation of the multi-pulse-wave rectifier.

Description

Harmonic evaluation method of multi-pulse rectifier under non-ideal condition
Technical Field
The application belongs to the technical field of power electronics, and particularly relates to a harmonic evaluation method of a multi-pulse rectifier under a non-ideal condition.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The multi-pulse rectifier using the 6-pulse rectifier circuit as the basic circuit unit has been widely used in high voltage direct current transmission, aircraft power supply, energy storage system, etc. The multi-pulse rectifier has the advantages of a 6-pulse rectifier circuit, and has higher alternating current side power density and better electric energy quality, and the main types of the multi-pulse rectifier include a 12-pulse rectifier, an 18-pulse rectifier, a 24-pulse rectifier and the like.
As the inventor knows, the three-phase supply voltage has a variable characteristic due to the line, the load, and the like, and there may be a three-phase voltage imbalance phenomenon, and at this time, the multi-pulse rectifier still operates under a non-ideal condition. The existing harmonic wave evaluation method is mainly oriented to a 6-pulse wave rectifier circuit, and harmonic wave evaluation is difficult to be carried out on the pulse wave rectifier circuits except the 6-pulse wave rectifier circuit; therefore, the conventional harmonic evaluation method is not universal, and is difficult to be applied to any type of multi-pulse rectifier. In addition, most of the existing harmonic wave evaluation methods are directed at ideal conditions and are not suitable for harmonic wave evaluation oriented to three-phase voltage unbalance working conditions and changes of running states.
Disclosure of Invention
In order to solve the problems, the application provides a harmonic evaluation method of a multi-pulse rectifier under a non-ideal condition, a harmonic coupling model suitable for any form of multi-pulse rectifier under the non-ideal condition is established, and harmonic current of the multi-pulse rectifier under the non-ideal condition is evaluated based on actual operating voltage, so that the problems that the harmonic evaluation method is not universal and the non-ideal condition is not applicable are solved, and the harmonic evaluation precision of the multi-pulse rectifier is improved.
According to some embodiments, the scheme of the application provides a harmonic evaluation method of a multi-pulse rectifier under non-ideal conditions, and the following technical scheme is adopted:
a harmonic evaluation method of a multi-pulse rectifier under non-ideal conditions comprises the following steps:
obtaining the fundamental voltage and the harmonic voltage magnitude on the power grid side of the multi-pulse rectifier under the non-ideal condition, and obtaining the fundamental voltage and the harmonic voltage magnitude on the rectifier side; n rectifying circuit basic units are arranged in the multi-pulse rectifier;
calculating a trigger angle and a conduction angle of a basic unit of the rectification circuit, and constructing a mapping relation between the voltage of the side-group wave of the power grid and the trigger angle and the conduction angle;
determining the voltage modulation relation and the current modulation relation of a basic unit of the rectifying circuit under the non-ideal condition;
calculating the direct current side voltage and current of the basic unit of the rectifying circuit according to the obtained voltage modulation relation; calculating the alternating current side current of the basic unit of the rectifying circuit according to the obtained current modulation relation;
obtaining a side harmonic current and a harmonic current of the power grid according to the calculated alternating side current of the basic unit of the rectification circuit, and constructing a harmonic coupling model representing the relation between the side harmonic voltage and the harmonic voltage of the power grid and the fundamental current and the harmonic current;
and modifying the voltage magnitude of the fundamental wave on the side of the power grid according to the constructed harmonic coupling model, determining the coupling relation between the phase current and the phase voltage, and realizing the harmonic evaluation of the multi-pulse rectifier.
As a further technical limitation, the non-ideal conditions include unbalanced three-phase voltage amplitude but balanced phase angle, balanced three-phase voltage amplitude but unbalanced phase angle, and unbalanced three-phase voltage amplitude and phase angle.
As a further technical limitation, the voltage data operated by the power grid side of the multi-pulse wave rectifier under the non-ideal condition is subjected to Fourier analysis, and the voltage value of the fundamental wave and the voltage value of each subharmonic wave on the power grid side are obtained.
As a further technical definition, said multi-pulse rectifier type has any form of 6N pulses, comprising a phase-shifting transformer and N rectifier circuit elementary units;
the grid side voltage is the primary side voltage of the phase-shifting transformer, namely the power supply voltage of the multi-pulse rectifier, and the rectifier side voltage is the secondary side voltage of the phase-shifting transformer, namely the power supply voltage of the basic unit of the rectification circuit.
Furthermore, the rectifier circuit basic unit adopts a three-phase full-bridge rectifier circuit, the input end of the three-phase full-bridge rectifier circuit is connected with the secondary side of the phase-shifting transformer, the output ends of the three-phase full-bridge rectifier circuit are adjacent to each other and are in short circuit, and the output ends of the two three-phase full-bridge rectifier circuits at the edge are connected with a direct current load.
As a further technical limitation, according to the structure of a phase-shifting transformer in the multi-pulse rectifier, the quantitative relation between the grid-side harmonic voltage and harmonic voltage magnitude of the multi-pulse rectifier in any form and the lateral harmonic voltage and harmonic voltage magnitude of the rectifier is determined, and the fundamental voltage and harmonic voltage magnitude on the rectifier side are calculated.
As a further technical limitation, a mapping relation between grid side fundamental wave voltage and the trigger angle and the conduction angle of each phase of thyristor of N basic units of the rectification circuit is established under the non-ideal condition, and the trigger angle and the conduction angle of the nth basic unit of the rectification circuit adopt the following expressions:
Figure DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 917481DEST_PATH_IMAGE002
、
Figure DEST_PATH_IMAGE003
and
Figure 275781DEST_PATH_IMAGE004
the firing angles of the thyristors of A phase, B phase and C phase of the basic unit of the nth rectifying circuit under the non-ideal condition are respectively,
Figure DEST_PATH_IMAGE005
、
Figure 154876DEST_PATH_IMAGE006
and
Figure DEST_PATH_IMAGE007
respectively the conduction angles of the A phase thyristor, the B phase thyristor and the C phase thyristor of the basic unit of the nth rectifying circuit under the non-ideal condition,
Figure 799484DEST_PATH_IMAGE008
、
Figure DEST_PATH_IMAGE009
and
Figure 131239DEST_PATH_IMAGE010
are respectively the firstnPhase voltages of A phase, B phase and C phase at AC side of basic unit of rectification circuit,
Figure DEST_PATH_IMAGE011
、
Figure 621126DEST_PATH_IMAGE012
and
Figure DEST_PATH_IMAGE013
the fundamental wave voltages of the A phase, the B phase and the C phase on the power grid side respectively,
Figure 89148DEST_PATH_IMAGE014
the relationship between the trigger angle of the thyristor and the voltage value of the side-group wave voltage of the power grid under the non-ideal condition,
Figure DEST_PATH_IMAGE015
the relationship between the conduction angle of the thyristor and the voltage value of the side-group wave voltage of the power grid under the non-ideal condition,
Figure 904657DEST_PATH_IMAGE016
is the voltage magnitude of side-group wave/harmonic wave of the power grid and the firstnThe conversion relationship between the voltage magnitudes of the fundamental/harmonic voltages on the rectifier side,
Figure DEST_PATH_IMAGE017
。
as a further technical limitation, a voltage modulation relationship and a current modulation relationship between both ac and dc sides of a basic unit of a multi-pulse rectifier circuit under a non-ideal condition are determined in consideration of differences in firing angles and conduction angles of thyristors in the basic unit of the multi-pulse rectifier circuit under the non-ideal condition based on a rectifier-side voltage of the multi-pulse rectifier circuit.
As a further technical limitation, the voltage modulation relation of basic units of the rectification circuit is utilized, the superposition result of the frequency voltages at the direct current side is calculated according to the frequency voltages at the alternating current side of the basic units of the N rectification circuits, the load parameter at the direct current side of the multi-pulse rectifier is determined, and the frequency currents at the direct current side are calculated;
calculating the frequency current of the alternating current side of the N rectifier circuit basic units according to the frequency current of the direct current side by using the current modulation relation of the rectifier circuit basic units to obtain the fundamental wave/each harmonic current of the rectifier side; under non-ideal conditions, due to different phase modulation relations of the N rectifying circuit basic units, the alternating side base wave/harmonic current of different phases of different circuit basic units are different.
As a further technical limitation, according to the structure of a phase-shifting transformer in the multi-pulse rectifier, determining the quantity relationship between the rectifier side fundamental wave/harmonic current flow magnitude and the grid side fundamental wave/harmonic current flow magnitude in the operation process of the multi-pulse rectifier under the non-ideal condition, and calculating to obtain the grid side fundamental wave/harmonic current of the multi-pulse rectifier under the non-ideal condition; establishing a harmonic coupling model suitable for a multi-pulse rectifier in any form under non-ideal conditions by determining the relation between the fundamental wave/harmonic wave voltage and the fundamental wave/harmonic wave current on the power grid side;
according to the operating voltage change condition of the power grid side of the multi-pulse rectifier under the non-ideal condition, the fundamental wave voltage magnitude value of the power grid side is corrected, harmonic coupling model parameters are determined, and the fundamental wave/each harmonic current evaluation value of the multi-pulse rectifier is calculated.
Compared with the prior art, the beneficial effect of this application is:
the harmonic coupling model suitable for any form of multi-pulse rectifier and non-ideal conditions is established, the voltage under the actual operation condition is used for evaluating the harmonic current under the non-ideal conditions of the multi-pulse rectifier, the problems that the harmonic evaluation method is not universal and the non-ideal conditions are not applicable are solved, and the harmonic evaluation precision of the multi-pulse rectifier is improved;
according to the method and the device, the actual operation voltage is analyzed, the harmonic current of the multi-pulse rectifier in any form is accurately evaluated, corresponding voltage treatment measures are provided according to the evaluation result, the electric energy quality of a power grid is effectively improved, and the safe and stable operation of the whole power system is guaranteed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of a harmonic evaluation method of a multi-pulse rectifier under non-ideal conditions in an embodiment of the present application;
FIG. 2 is a general schematic diagram of any type of multi-pulse rectifier in accordance with embodiments of the present application;
FIG. 3 is a schematic structural diagram of a basic unit of a rectifier circuit in an embodiment of the present application;
fig. 4 is a diagram illustrating a mapping relationship between a supply voltage, a trigger angle and a conduction angle of a basic unit of a rectifier circuit under a non-ideal condition in an embodiment of the present application.
Detailed Description
The present application will be 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 application 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 application. 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.
The embodiment of the application introduces a harmonic evaluation method of a multi-pulse rectifier under a non-ideal condition.
A harmonic evaluation method of a multi-pulse rectifier under non-ideal conditions as shown in fig. 1 includes:
step S01: carrying out Fourier analysis on the power grid side operating voltage data of the multi-pulse rectifier under the non-ideal condition to obtain power grid side-group wave voltage and each subharmonic voltage magnitude;
step S02: determining the quantity relation between the voltage magnitude of the fundamental wave/harmonic wave voltage at the power grid side of the multi-pulse wave rectifier and the voltage magnitude of the fundamental wave/harmonic wave voltage at the rectifier side in any form according to the structure of the phase-shifting transformer in the multi-pulse wave rectifier;
step S03: establishing a mapping relation between grid side fundamental wave voltage and trigger angles and conduction angles of thyristors of all phases of basic units of N rectifying circuits under a non-ideal condition;
step S04: according to the rectifier side voltage of the multi-pulse rectifier, considering the difference of the trigger angle and the conduction angle of a thyristor in the 6-pulse rectifier circuit basic unit under the non-ideal condition, and determining the AC-DC two-side voltage and current modulation relation of the 6-pulse rectifier circuit basic unit under the non-ideal condition;
step S05: calculating the superposition result of each frequency voltage at the direct current side according to each frequency voltage at the alternating current side of the basic units of the N6-pulse rectification circuits by utilizing the voltage modulation relation of the basic units of the circuit, and further calculating each frequency current at the direct current side by determining the load parameters at the direct current side of the multi-pulse rectifier;
step S06: calculating frequency currents at alternating current sides of N6-pulse rectifier circuit basic units according to frequency currents at direct current sides by using a circuit basic unit current modulation relation, namely rectifier side fundamental waves/harmonic currents;
step S07: according to the phase-shifting transformer structure in the multi-pulse rectifier, the quantitative relation between the rectifier side fundamental wave/harmonic current flow magnitude and the grid side fundamental wave/harmonic current flow magnitude in the operation process of the multi-pulse rectifier under the non-ideal condition can be determined, and further the multi-pulse rectifier grid side fundamental wave/harmonic current under the non-ideal condition can be calculated; establishing a harmonic coupling model suitable for any form of multi-pulse wave rectifier and non-ideal conditions by determining the relation between the fundamental wave/harmonic wave voltage and the fundamental wave/harmonic wave current on the power grid side;
step S08: according to the change condition of the grid-side running voltage of the multi-pulse wave rectifier under the non-ideal condition, the voltage vector values of the A phase, the B phase and the C phase are corrected, the coupling relation between the phase current and the phase voltage is determined, and the evaluation value of the fundamental wave/each harmonic current of the multi-pulse wave rectifier is calculated.
As one or more embodiments, in step S01, the voltage magnitudes of the grid-side fundamental wave voltage and the subharmonic voltage obtained are:
Figure 723708DEST_PATH_IMAGE018
wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE019
，
Figure 952040DEST_PATH_IMAGE020
，
Figure DEST_PATH_IMAGE021
representing k-order voltage vector values of A, B, C phases on the power grid side, wherein the k =1 represents a fundamental wave, and the k represents a harmonic order when the k is an integer greater than 1; k is an integer and represents the maximum harmonic voltage number under consideration.
The non-ideal conditions of the multi-pulse rectifier comprise conditions that three-phase voltage amplitude is unbalanced but phase angles are balanced, conditions that three-phase voltage amplitude is balanced but phase angles are unbalanced, and conditions that three-phase voltage amplitude and phase angles are not balanced, and under the non-ideal conditions, the voltage magnitude of each phase needs to be solved through Fourier analysis.
It can be understood that the three-phase voltage amplitude is balanced only when the three-phase voltages are equal, and the three-phase voltages are copied and unbalanced in other cases; only when the phase difference of three-phase voltage is 120 o The phase angle is balanced, and the phase angles are unbalanced in other cases.
As one or more embodiments, in step S02, the magnitudes of the obtained nth rectifier-side fundamental voltage and the voltage of each subharmonic are:
Figure 399202DEST_PATH_IMAGE022
wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE023
the conversion relation between the voltage magnitude of the fundamental wave/harmonic wave on the side of the power grid and the voltage magnitude of the fundamental wave/harmonic wave on the side of the nth rectifier is obtained.
The multi-pulse wave rectifier type includes a 6-pulse wave rectifier, a 12-pulse wave rectifier, a 18-pulse wave rectifier, etc., and the general structure diagram of any form of multi-pulse wave rectifier is shown in fig. 2, and the structure thereof includes a phase-shifting transformer and N rectifier circuit basic units, so that any form of multi-pulse wave rectifier with 6N pulse waves can be formed, and the structure diagram of the rectifier circuit basic units is shown in fig. 3;
the power grid side voltage refers to the power supply voltage of the multi-pulse rectifier and is also the primary side voltage of the phase-shifting transformer; the rectifier-side voltage is the supply voltage of the basic unit of the 6-pulse rectification circuit and is also the secondary side voltage of the phase-shifting transformer.
As can be understood, the phase difference of each secondary side of the phase-shifting transformer is δ =2 pi/M, where M is the number of pulses of the multi-pulse rectifier; however, the model construction method in this embodiment is applicable to any type of phase-shifting transformer, and is not limited to the phase-shifting transformer structure, and the number relationship between the fundamental wave/harmonic current flow magnitude on the rectifier side and the grid-side fundamental wave/harmonic current flow magnitude can be obtained by combining the phase-shifting transformer structure
Figure 995399DEST_PATH_IMAGE024
Thereby evaluating the harmonic current of the rectifier and improving the applicability of the method
As one or more embodiments, the calculation of the firing angle and the conduction angle is related to the actual requirement: when the actual demand voltage of the DC side is U dc The effective value of the actual voltage on the AC side is U ac Then, the values of the firing angle α and the conduction angle θ can be calculated as follows:
Figure DEST_PATH_IMAGE025
in the formula (I), the compound is shown in the specification,
Figure 426381DEST_PATH_IMAGE026
is the angular frequency of the fundamental wave,
Figure DEST_PATH_IMAGE027
the number of basic units of the rectifying circuit of the multi-pulse rectifier,
Figure 399016DEST_PATH_IMAGE028
is the leakage inductance of the phase-shifting transformer.
As one or more embodiments, in step S03, the relationship of the circuit basic unit supply voltage to the firing angle and the conduction angle of the thyristor under the non-ideal condition is as shown in fig. 4, and the following expressions are adopted for the firing angle and the conduction angle of the n-th rectifier circuit basic unit:
Figure 497422DEST_PATH_IMAGE001
wherein, the first and the second end of the pipe are connected with each other,
Figure 264521DEST_PATH_IMAGE002
、
Figure 386061DEST_PATH_IMAGE003
and
Figure 552600DEST_PATH_IMAGE004
the firing angles of the thyristors of A phase, B phase and C phase of the basic unit of the nth rectifying circuit under the non-ideal condition are respectively,
Figure 849720DEST_PATH_IMAGE005
、
Figure 381195DEST_PATH_IMAGE006
and
Figure 786769DEST_PATH_IMAGE007
respectively the conduction angles of the A phase thyristor, the B phase thyristor and the C phase thyristor of the basic unit of the nth rectifying circuit under the non-ideal condition,
Figure 694682DEST_PATH_IMAGE008
、
Figure 377467DEST_PATH_IMAGE009
and
Figure 79844DEST_PATH_IMAGE010
are respectively the firstnPhase voltages of A phase, B phase and C phase at AC side of basic unit of rectification circuit,
Figure 707135DEST_PATH_IMAGE011
、
Figure 90842DEST_PATH_IMAGE012
and
Figure 690451DEST_PATH_IMAGE013
the fundamental wave voltages of the A phase, the B phase and the C phase on the power grid side are respectively,
Figure 626046DEST_PATH_IMAGE014
the relationship between the trigger angle of the thyristor and the voltage value of the side-group wave voltage of the power grid under the non-ideal condition,
Figure 943895DEST_PATH_IMAGE015
for the relationship between the conduction angle of the thyristor and the voltage value of the side-group wave of the power grid under the non-ideal condition,
Figure 865715DEST_PATH_IMAGE016
is the voltage magnitude of side-group wave/harmonic wave of the power grid and the firstnThe conversion relationship between the voltage magnitudes of the fundamental/harmonic voltages on the rectifier side,
Figure 382147DEST_PATH_IMAGE017
。
in one or more embodiments, in step S04, a modulation relationship between ac and dc voltages and currents on both sides of the basic unit of the 6-pulse rectifier circuit under the non-ideal condition is determined according to the rectifier-side voltage of the multi-pulse rectifier, taking into account differences between firing angles and conduction angles of thyristors in the basic unit of the 6-pulse rectifier circuit under the non-ideal condition, and for the nth basic unit of the rectifier circuit, the specific modulation relationship is as follows:
Figure DEST_PATH_IMAGE029
Figure 118938DEST_PATH_IMAGE030
wherein s and t are the harmonic frequency of the modulation relationship, MU respectively An ，MU Bn ，MU Cn Respectively, the voltage modulation relationship under non-ideal conditions, MI An ，MI Bn ，MI Cn Respectively, are the current modulation relationship under non-ideal conditions,
Figure DEST_PATH_IMAGE031
is the angular frequency of the fundamental wave,
Figure 720820DEST_PATH_IMAGE032
the thyristor commutation overlap angle under non-ideal conditions is related to the leakage inductance of the phase-shifting transformer.
Understandably, the overlap angle of commutation
Figure 508648DEST_PATH_IMAGE032
The calculation method of (c) is as follows:
Figure DEST_PATH_IMAGE033
in the formula, L S For the leakage inductance of the phase-shifting transformer, M is the pulse frequency of the multi-pulse rectifier, I dc Is the actual current demand on the dc side.
As one or more embodiments, in step S06, under non-ideal conditions, since the N6-pulse rectifier circuit basic units have different phase modulation relationships, the ac side fundamental waves/harmonic currents of different phases of the different circuit basic units are different.
As one or more embodiments, in step S07, the harmonic coupling model may be expressed as:
Figure 551690DEST_PATH_IMAGE034
wherein the model parameters
Figure DEST_PATH_IMAGE035
，
Figure 438875DEST_PATH_IMAGE036
，
Figure DEST_PATH_IMAGE037
Representing h-order current vector values of A, B, C phases on the power grid side, wherein the h =1 represents a fundamental wave, and the h represents the harmonic order when the h is an integer greater than 1; h is an integer and represents the maximum harmonic current number considered;
Figure 262474DEST_PATH_IMAGE038
the harmonic coupling relation related to A, B, C three-phase fundamental voltage under non-ideal conditions is characterized.
As one or more embodiments, in step S08, during the actual operation of the multi-pulse wave rectifier, since the grid-side operating voltage changes constantly, it is necessary to adjust the voltage magnitude of each phase in the harmonic coupling model and the harmonic coupling model according to the fourier analysis result of the operating voltage, thereby obtaining the harmonic evaluation value during the operation of the multi-pulse wave rectifier.
By using the harmonic coupling model applicable to any form of multi-pulse rectifier and non-ideal condition provided by the present embodiment, a 12-pulse rectifier and a 18-pulse rectifier in the multi-pulse rectifier are selected for simulation analysis, the effective value of the three-phase fundamental voltage is 220V, the dc side is a resistive load, and the voltage harmonic distortion rate under the non-ideal condition is 5.24% (the voltage distortion rate calculation formula is as follows:
Figure DEST_PATH_IMAGE039
；U k characterizing the k-th order voltage amplitude, U, of the grid side A, B, C phase 1 The fundamental voltage amplitude of A, B, C phases on the power grid side is characterized), and the voltage unbalance is 4.08% (the voltage unbalance calculation formula is as follows:
Figure 260517DEST_PATH_IMAGE040
Figure DEST_PATH_IMAGE041
，
Figure 485962DEST_PATH_IMAGE042
，
Figure DEST_PATH_IMAGE043
the fundamental voltage magnitude of A, B, C phase representing the power grid side), the voltage harmonic distortion rate is 1.59% and the voltage unbalance is 1.95% under the non-ideal condition two. The relative error of the simulation of the 12-pulse rectifier and the simulation of the 18-pulse rectifier and the calculation of the harmonic current are calculated under two non-ideal conditions respectively (the calculation formula of the relative error is as follows:
Figure 544048DEST_PATH_IMAGE044
；
Figure DEST_PATH_IMAGE045
represents the calculated h-th harmonic current amplitude,
Figure 120523DEST_PATH_IMAGE046
representing the simulated h harmonic current amplitude) as shown in table 1. As can be seen from the table, the coincidence degree of the proposed model and the actually measured data is high, and the accuracy of the proposed model and the applicability of the proposed model under non-ideal conditions are verified.
TABLE 1 relative error of calculated and experimental results
Figure DEST_PATH_IMAGE047
The harmonic coupling model suitable for any form of multi-pulse rectifier and non-ideal conditions is established, the harmonic current of the multi-pulse rectifier under the non-ideal conditions is evaluated by using the voltage under the actual operation conditions, the problems that the harmonic evaluation method is not universal and the non-ideal conditions are not applicable are solved, and the harmonic evaluation precision of the multi-pulse rectifier is improved; by analyzing the actual operating voltage, the harmonic current of the multi-pulse rectifier in any form is accurately evaluated, and corresponding voltage control measures are provided according to the evaluation result, so that the electric energy quality of a power grid is effectively improved, and the safe and stable operation of the whole power system is guaranteed.
Although the embodiments of the present application have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present application, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive effort by those skilled in the art.

Claims (7)

1. A method for harmonic estimation of a multi-pulse rectifier under non-ideal conditions, comprising:
performing Fourier analysis on voltage data operated by the power grid side of the multi-pulse rectifier under the non-ideal condition to obtain a fundamental wave voltage magnitude value and each subharmonic voltage magnitude value of the power grid side; obtaining the fundamental voltage and the harmonic voltage magnitude of the multi-pulse rectifier side under the non-ideal condition;
the multi-pulse rectifier is internally provided withNA rectifier circuit basic unit; first, thenThe voltage values of the fundamental wave voltage and each subharmonic wave voltage on the rectifier side are as follows:
Figure 313264DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 671564DEST_PATH_IMAGE002
for the voltage magnitude and the order of the side wave/harmonic wave of the power gridnThe conversion relationship between the voltage magnitudes of the fundamental/harmonic waves on the rectifier side;
calculating a trigger angle and a conduction angle of a basic unit of the rectification circuit, and constructing a mapping relation between the voltage of the side-group wave of the power grid and the trigger angle and the conduction angle; first, thenThe trigger angle and the conduction angle of the basic unit of the rectifying circuit adopt the following expressions:
Figure 144134DEST_PATH_IMAGE003
；
wherein the content of the first and second substances,
Figure 195266DEST_PATH_IMAGE004
、
Figure 58180DEST_PATH_IMAGE005
and
Figure 282488DEST_PATH_IMAGE006
the firing angles of the thyristors of A phase, B phase and C phase of the basic unit of the nth rectifying circuit under the non-ideal condition are respectively,
Figure 281668DEST_PATH_IMAGE007
、
Figure 566019DEST_PATH_IMAGE008
and
Figure 913299DEST_PATH_IMAGE009
respectively the conduction angles of the A phase thyristor, the B phase thyristor and the C phase thyristor of the basic unit of the nth rectifying circuit under the non-ideal condition,
Figure 941298DEST_PATH_IMAGE010
、
Figure 122880DEST_PATH_IMAGE011
and
Figure 250236DEST_PATH_IMAGE012
are respectively the firstnPhase voltages of A phase, B phase and C phase at AC side of basic unit of rectification circuit,
Figure 150059DEST_PATH_IMAGE013
、
Figure 653853DEST_PATH_IMAGE014
and
Figure 955521DEST_PATH_IMAGE015
the fundamental wave voltages of the A phase, the B phase and the C phase on the power grid side respectively,
Figure 253779DEST_PATH_IMAGE016
the relationship between the trigger angle of the thyristor and the voltage value of the side-group wave voltage of the power grid under the non-ideal condition,
Figure 640898DEST_PATH_IMAGE017
the relationship between the conduction angle of the thyristor and the voltage value of the side-group wave voltage of the power grid under the non-ideal condition,
Figure 948382DEST_PATH_IMAGE018
is the voltage magnitude of side-group wave/harmonic wave of the power grid and the firstnThe conversion relationship between the voltage magnitudes of the fundamental/harmonic voltages on the rectifier side,
Figure 838978DEST_PATH_IMAGE019
；
determining a voltage modulation relation and a current modulation relation of a basic unit of the rectifying circuit under a non-ideal condition; for the firstnThe basic unit of the rectification circuit has the following specific modulation relation:
Figure 573716DEST_PATH_IMAGE020
Figure 182551DEST_PATH_IMAGE021
wherein the content of the first and second substances,sandtrespectively the harmonic order of the modulation relationship,MU nA ，MU nB ，MU nC respectively, are voltage modulation relations under non-ideal conditions,MI nA ，MI nB ，MI nC respectively, are the current modulation relationship under non-ideal conditions,ωis the angular frequency of the fundamental wave,μthe thyristor commutation overlap angle under the non-ideal condition is related to the leakage inductance of the phase-shifting transformer;
calculating the direct current side voltage and current of the basic unit of the rectifying circuit according to the obtained voltage modulation relation; calculating the alternating current side current of the basic unit of the rectifying circuit according to the obtained current modulation relation;
obtaining a side harmonic current and a harmonic current of the power grid according to the calculated alternating side current of the basic unit of the rectification circuit, and constructing a harmonic coupling model representing the relation between the side harmonic voltage and the harmonic voltage of the power grid and the fundamental current and the harmonic current; the harmonic coupling model can be expressed as:
Figure 293727DEST_PATH_IMAGE022
wherein the model parameters
Figure 304408DEST_PATH_IMAGE023
，
Figure 210047DEST_PATH_IMAGE024
，
Figure 306179DEST_PATH_IMAGE025
Representing the h-order current vector value of the A, B, C phases on the power grid side, wherein h =1 represents the fundamental wave, and h is greater than h1 represents the harmonic order; h is an integer and represents the maximum harmonic current number considered;
Figure 946677DEST_PATH_IMAGE026
representing the harmonic coupling relation related to A, B, C three-phase fundamental voltage under the non-ideal condition;
according to the operating voltage change condition of the grid side of the multi-pulse wave rectifier under the nonideal condition in the constructed harmonic coupling model, the fundamental wave voltage magnitude value of the grid side is corrected, the coupling relation between phase current and phase voltage is determined, the fundamental wave/each subharmonic current evaluation value of the multi-pulse wave rectifier is calculated, and the harmonic evaluation of the multi-pulse wave rectifier is realized;
in the process of constructing a harmonic coupling model representing the relationship between the grid side fundamental voltage and harmonic voltage, and the fundamental wave current and harmonic current, according to the structure of a phase-shifting transformer in the multi-pulse rectifier, determining the quantity relationship between the rectifier side fundamental wave/harmonic current flow value and the grid side fundamental wave/harmonic current flow value in the operation process of the multi-pulse rectifier under the non-ideal condition, and calculating to obtain the grid side fundamental wave/harmonic current of the multi-pulse rectifier under the non-ideal condition; by determining the relation between the fundamental wave/harmonic wave voltage and the fundamental wave/harmonic wave current on the power grid side, a harmonic wave coupling model suitable for any form of multi-pulse wave rectifier under non-ideal conditions is established.
2. The method of harmonic evaluation of a multi-pulse wave rectifier under non-ideal conditions as set forth in claim 1 wherein said non-ideal conditions include three-phase voltage amplitude imbalance but phase angle balance, three-phase voltage amplitude imbalance but phase angle imbalance, and three-phase voltage amplitude and phase angle imbalance.
3. The method of claim 1, wherein the multi-pulse rectifier type has 6NAny form of pulse, including phase-shifting transformers andNa rectifier circuit basic unit;
the grid side voltage is the primary side voltage of the phase-shifting transformer, namely the power supply voltage of the multi-pulse rectifier, and the rectifier side voltage is the secondary side voltage of the phase-shifting transformer, namely the power supply voltage of the basic unit of the rectification circuit.
4. The method as claimed in claim 3, wherein the basic unit of the rectifier circuit is a three-phase full-bridge rectifier circuit, the input end of the three-phase full-bridge rectifier circuit is connected to the secondary side of the phase-shifting transformer, the output ends of the adjacent three-phase full-bridge rectifier circuits are short-circuited, and the output ends of the two marginal three-phase full-bridge rectifier circuits are connected to a dc load.
5. The method of harmonic evaluation of a multipulse rectifier under non-ideal conditions as set forth in claim 1, wherein the fundamental voltage and the harmonic voltage magnitude on the rectifier side are calculated by determining the quantitative relationship between the grid-side harmonic voltage and the harmonic voltage magnitude of the multipulse rectifier in any form and the grid-side harmonic voltage and the harmonic voltage magnitude on the rectifier side based on the structure of the phase-shifting transformer in the multipulse rectifier.
6. The method of claim 1, wherein the voltage modulation and current modulation of both AC and DC sides of the basic unit of the multi-pulse rectifier circuit under the non-ideal condition are determined based on the rectifier side voltage of the multi-pulse rectifier circuit, taking into account the difference between the firing angle and conduction angle of the thyristors in the basic unit of the multi-pulse rectifier circuit under the non-ideal condition.
7. The method of claim 1, wherein the voltage modulation relationship of the fundamental unit of the rectifier circuit is used to estimate the harmonics of the multi-pulse rectifier under non-ideal conditionsNCalculating the superposition result of the frequency voltages at the DC side from the frequency voltages at the AC side of the basic unit of the rectification circuit, determining the load parameters at the DC side of the multi-pulse rectifier, and measuringCalculating each frequency current at the direct current side;
calculating according to the current of each frequency at the DC side by using the current modulation relation of the basic unit of the rectifying circuitNEach frequency current at the alternating current side of the basic unit of the rectifier circuit obtains fundamental wave/each harmonic current at the rectifier side; wherein, under non-ideal conditions, theNThe modulation relations of all phases of the basic units of the rectification circuit are different, and the alternating side group waves/harmonic currents of different phases of the basic units of different circuits are different.
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