CN114826009B - Control method and device of three-phase four-bridge-arm auxiliary converter - Google Patents

Control method and device of three-phase four-bridge-arm auxiliary converter Download PDF

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CN114826009B
CN114826009B CN202210579548.0A CN202210579548A CN114826009B CN 114826009 B CN114826009 B CN 114826009B CN 202210579548 A CN202210579548 A CN 202210579548A CN 114826009 B CN114826009 B CN 114826009B
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voltage
component
result
phase
sequence component
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CN114826009A (en
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李骄松
周双雷
尚付磊
林显琦
王磊
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CRRC Qingdao Sifang Rolling Stock Research Institute Co Ltd
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CRRC Qingdao Sifang Rolling Stock Research Institute Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a control method and a device of a three-phase four-bridge arm auxiliary converter, wherein the control method comprises the following steps: voltage acquisition: collecting three-phase output voltage; a first compensation result obtaining step: obtaining a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotation coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to obtain a positive sequence component compensation result and a negative sequence component compensation result; a second compensation result obtaining step: obtaining a zero sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage, and performing feedback compensation on the zero sequence voltage component to obtain a zero sequence component compensation result; and (3) balancing three-phase output voltage: and performing three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applying the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage.

Description

Control method and device of three-phase four-bridge-arm auxiliary converter
Technical Field
The invention relates to a control method and a control system of a three-phase four-leg auxiliary converter, in particular to a control method and a control device of a three-phase four-leg auxiliary converter for improving the single-phase load carrying capacity of a high-frequency auxiliary converter.
Background
The train auxiliary converter converts high-voltage direct current (DC 1500V/DC 750V) into three-phase alternating current (AC 380V) to provide electric energy for medium-voltage loads of a train. The conventional medium-voltage load is single, the unbalanced load is less, and the requirement can be met by adopting a three-phase three-wire system output system. However, with the development of urban rail transit, medium-voltage loads of urban rail trains become increasingly complex, and besides balancing loads, the introduction of loads such as electric heating, lighting, single-phase sockets, dynamic maps and the like requires that an auxiliary converter has a certain single-phase load carrying capacity, and a three-phase four-wire system output system is generally adopted.
The train auxiliary converter usually electrically isolates the grid supply side from the train load side, conventional isolation
The technology comprises isolation of a power frequency transformer and isolation of a high frequency transformer. The former usually adopts a D/Yn type transformer, and an output N line is led out from the secondary side of the industrial frequency transformer; in the high-frequency transformer isolation topology, an output N line is led out from the midpoint of a three-phase filter capacitor or the midpoint of a front-end support capacitor. When a single-phase unbalanced load is connected, the single-phase load current flows into the transformer, the phenomenon of unbalanced magnetic circuits on the secondary side of the transformer can be caused, the winding can be heated unevenly after long-time operation, the insulation performance is influenced, and the influence on the output voltage is small; when an N line is led out from the midpoint of a three-phase filter capacitor and is connected into a single-phase unbalanced load, the single-phase load current flows into the three-phase filter capacitor, so that the output voltage imbalance phenomenon (see fig. 1) can be caused, wherein fig. 1 shows that the U-phase carries 1kW, the upper part is output voltage waveform, and the lower part is output current waveform. The service life of the three-phase filter capacitor can be shortened when the three-phase filter capacitor works in an unbalanced state for a long time; when the N line is led out from the midpoint of the front-end supporting capacitor and is connected into a single-phase unbalanced load, although the influence on the output voltage is small, the single-phase load current flows into the front-end direct-current side supporting capacitor, extra current stress can be brought to the front-end supporting capacitor, the loss is increased, meanwhile, the loop stray inductance is increased by the series capacitor, a high-voltage peak can be generated when the power device is turned off, and the service life of the device is influenced. Obviously, the performance of the auxiliary converter adopting the power frequency isolation technology is superior to that of the high-frequency isolation auxiliary converter under the unbalanced load working condition, but the auxiliary converter has no advantages in the aspects of volume, weight, noise and the like, and is contrary to the concept of 'green trip' advocated at present.
At present, an auxiliary converter based on a high-frequency isolation technology is a main direction of development in the field of urban rail transit, and in order to improve the single-phase load carrying capacity of the high-frequency auxiliary converter, it is urgently needed to develop a control method and a control device of a three-phase four-leg auxiliary converter, which overcome the defects and improve the single-phase load carrying capacity of the high-frequency auxiliary converter.
Disclosure of Invention
In order to solve the above problem, the present invention provides a control method for a three-phase four-leg auxiliary converter, wherein an inverter unit of the three-phase four-leg auxiliary converter includes a fourth leg, an output point of the fourth leg is connected to an ac output N line through an inductor, and the control method includes:
voltage acquisition: collecting three-phase output voltage;
a first compensation result obtaining step: obtaining a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to obtain a positive sequence component compensation result and a negative sequence component compensation result;
a second compensation result obtaining step: obtaining a zero-sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage, and performing feedback compensation on the zero-sequence voltage component to obtain a zero-sequence component compensation result;
and (3) balancing three-phase output voltage: and performing three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applying the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage.
In the control method, the obtaining of the first compensation result includes:
a two-phase conversion voltage obtaining step: 3/2 conversion and PARK conversion are carried out on the three-phase output voltage to obtain two-phase conversion voltage;
double DQ conversion step: carrying out positive and negative synchronous rotation coordinate transformation on the two-phase conversion voltage and eliminating a double frequency component to obtain four variables;
a filtering step: low-pass filtering is carried out on the four variables to obtain a direct current component U dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
PID control step: taking the target value of the output voltage as a given value, and taking the direct-current component U as a given value dpFltr As a feedback value, an output result U is obtained through PID control dpout Taking 0 as a given value, and taking the direct current component U as a given value qpFltr 、U dnFltr And U qpFltr As a reverseFeeding values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout For the positive sequence component compensation result, output result U dnout And output the result U qnout The result is compensated for the negative sequence component.
In the above control method, the second compensation result obtaining step includes:
a zero-sequence voltage component obtaining step: obtaining the zero sequence voltage component by a symmetrical component method according to the three-phase output voltage;
PR control step: taking the zero sequence component as a feedback value and 0 as a target value, and obtaining an output result U through proportion-resonance control nout Output the result U nout And obtaining the zero sequence component compensation result.
In the above control method, the balancing of the three-phase output voltages includes:
a conversion step: respectively carrying out 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain three-phase conversion voltage, and obtaining first voltage, second voltage and third voltage according to the three-phase conversion voltage and the zero sequence component compensation result;
a three-dimensional modulated wave voltage obtaining step: obtaining a three-dimensional modulation wave according to the first voltage, the second voltage and the third voltage through sector judgment, vector action time calculation and a seven-segment switch voltage vector action sequence;
a control pulse obtaining step: comparing the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse of a switching device corresponding to each bridge arm of the inversion unit;
controlling and adjusting: and correspondingly controlling the action of each switching device according to each control pulse.
The control method described above, wherein the control pulse obtaining step includes:
and outputting high-level pulses when the triangular carrier wave is larger than the three-dimensional modulation wave, and outputting low-level pulses when the triangular carrier wave is smaller than the three-dimensional modulation wave.
The control method described above, wherein the control adjusting step includes: the switching devices of the upper bridge arm of each bridge arm are opposite in action to the switching devices of the lower bridge arm thereof.
The invention also provides a control device of the three-phase four-leg auxiliary converter, wherein an inversion unit of the three-phase four-leg auxiliary converter comprises a fourth leg, an output point of the fourth leg is connected with an alternating current output N line through an inductor, and the control device comprises:
the voltage acquisition unit is used for acquiring three-phase output voltage;
the first compensation result acquisition unit is used for acquiring a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to acquire a positive sequence component compensation result and a negative sequence component compensation result;
the second compensation result acquisition unit is used for acquiring a zero-sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage and carrying out feedback compensation on the zero-sequence voltage component to acquire a zero-sequence component compensation result;
and the three-phase output voltage balancing unit performs three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applies the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage.
The control device described above, wherein the first compensation result obtaining unit includes:
the two-phase conversion voltage obtaining module is used for carrying out 3/2 conversion and PARK conversion on the three-phase output voltage to obtain two-phase conversion voltage;
the double-DQ conversion module is used for carrying out positive and negative synchronous rotation coordinate conversion on the two-phase conversion voltage and eliminating a double frequency component to obtain four variables;
a low-pass filtering module for low-pass filtering the four variables to obtain DC componentU dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
A PID control module for taking the output voltage target value as a given value and taking the DC component U as a given value dpFltr As a feedback value, an output result U is obtained through PID control dpout Taking 0 as a given value, and taking the direct current component U as a given value qpFltr 、U dnFltr And U qpFltr As feedback values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout For the positive sequence component compensation result, output result U dnout And output the result U qnout The result is compensated for the negative sequence component.
The control device described above, wherein the second compensation result obtaining unit includes:
the zero sequence voltage component acquisition module is used for acquiring the zero sequence voltage component according to the three-phase output voltage by a symmetrical component method;
the PR control module takes the zero-sequence component as a feedback value and 0 as a target value to obtain an output result U through proportional-resonant control nout Output the result U nout And obtaining the zero sequence component compensation result.
The above control device, wherein the three-phase output voltage balancing unit comprises:
the transformation module is used for respectively carrying out 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain three-phase conversion voltage, and obtaining first voltage, second voltage and third voltage according to the three-phase conversion voltage and the zero sequence component compensation result;
the SVPWM module obtains a three-dimensional modulation wave through sector judgment, vector action time calculation and a seven-segment switch voltage vector action sequence according to the first voltage, the second voltage and the third voltage;
the control pulse obtaining module is used for comparing the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse corresponding to a switching device of each bridge arm of the inversion unit;
and the control regulating module correspondingly controls the action of each switching device according to each control pulse.
In summary, compared with the prior art, the invention has the following effects: the control method and the control device of the three-phase four-bridge-arm auxiliary converter decompose by adopting a symmetrical component method, and respectively compensate positive sequence, negative sequence and zero sequence components so as to overcome the unbalanced phenomenon.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a waveform diagram illustrating a voltage imbalance phenomenon;
FIG. 2 is a schematic circuit diagram of a three-phase four-leg auxiliary converter according to the present invention;
FIG. 3 is a flow chart of a control method of the present invention;
FIG. 4 is a flowchart of step S2 in FIG. 3;
FIG. 5 is a flowchart of step S3 in FIG. 3;
FIG. 6 is a flowchart of step S4 in FIG. 3;
FIG. 7 is a schematic diagram of the control device of the present invention;
FIG. 8 is a waveform diagram of a balanced three-phase output voltage;
FIG. 9 is a flow chart of DC component acquisition;
FIG. 10 is a flow chart of PID control;
FIG. 11 is a PR control flow chart;
fig. 12 is a schematic view of SVPWM modulation.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The exemplary embodiments of the present invention and the description thereof are provided to explain the present invention and not to limit the present invention. Additionally, the same or similar numbered elements/components used in the drawings and the embodiments are used to represent the same or similar parts.
As used herein, "first," "second," "S1," "S2," "8230," etc., do not refer specifically to sequential or ordinal meanings, nor are they intended to limit the invention, but merely to distinguish between elements or operations described in the same technical language.
With respect to directional terminology used herein, for example: up, down, left, right, front or rear, etc., are directions with reference to the drawings only. Accordingly, the directional terminology used is intended to be illustrative and is not intended to be limiting of the present teachings.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
As used herein, "and/or" includes any and all combinations of the described items.
References to "plurality" herein include "two" and "more than two"; reference to "multiple sets" herein includes "two sets" and "more than two sets".
As used herein, the terms "substantially", "about" and the like are used to modify any slight variation or error in quantity which does not materially alter the nature of the variation or error. Generally, the range of slight variations or errors modified by such terms may be 20% in some embodiments, 10% in some embodiments, 5% in some embodiments, or other values. It should be understood by those skilled in the art that the aforementioned values can be adjusted according to actual needs, and are not limited thereto.
Certain words used to describe the present application are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the present application.
Referring to fig. 2 to fig. 3, fig. 2 is a schematic circuit diagram of a three-phase four-leg auxiliary converter according to the present invention; fig. 3 is a flowchart of a control method of the present invention. As shown in fig. 2 to 3, the fourth bridge arm Sn is added to the inverter unit at the rear end of the three-phase four-bridge arm auxiliary converter of the present invention, and the output point of the fourth bridge arm is connected to the ac output N line through the inductor Ln. According to the invention, through the switching action of the fourth bridge arm Sn, unbalanced load current can flow into the bridge arm, the balance of output voltage and the balance of three-phase filter capacitor current are ensured, and the quality of output voltage waveform is improved. The control method of the invention comprises the following steps:
a voltage acquisition step S1: collecting three-phase output voltage;
a first compensation result obtaining step S2: obtaining a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to obtain a positive sequence component compensation result and a negative sequence component compensation result;
a second compensation result obtaining step S3: obtaining a zero-sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage, and performing feedback compensation on the zero-sequence voltage component to obtain a zero-sequence component compensation result;
and (3) balancing three-phase output voltage: and performing three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applying the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage.
Firstly, three-phase output voltages UN, VN and WN are obtained, then the three-phase voltages are subjected to 3/2 conversion and PARK conversion, direct-current components in alternating-current voltages can be eliminated through the conversion, positive sequence components and negative sequence components of the three-phase output voltages are separated through double DQ conversion, and closed-loop control is performed on the positive sequence components and the negative sequence components respectively to obtain positive sequence component compensation results and negative sequence component compensation results. And secondly, acquiring zero-sequence components in the three-phase output voltages UN, VN and WN by using a symmetrical component method, wherein the zero-sequence components are alternating current signals, and performing feedback compensation by using a proportional resonant controller to obtain a zero-sequence component compensation result. And finally, acting the compensation results of the positive sequence and the negative sequence and the compensation result of the zero sequence component in the second step on a three-dimensional space rotating vector (3D-SVPWM) modulator to obtain a modulation waveform, comparing the modulation waveform with a carrier to obtain a control pulse, and correspondingly acting the obtained control pulse on the power device of each bridge arm as shown in fig. 8 to finally obtain balanced three-phase output voltage. In fig. 7, the U-phase belt load is 1kW, the upper part is an output voltage waveform, and the lower part is an output current waveform.
Referring to fig. 4, 9 and 10, fig. 4 is a flowchart of step S2 in fig. 3; FIG. 9 is a flow chart of DC component acquisition; fig. 10 is a flowchart of PID control. As shown in fig. 4, 9 and 10, the first compensation result obtaining step S2 includes:
two-phase conversion voltage obtaining step S21: 3/2 conversion and PARK conversion are carried out on the three-phase output voltage to obtain two-phase conversion voltage;
double DQ conversion step S22: carrying out positive and negative synchronous rotation coordinate transformation on the two-phase conversion voltage and eliminating a double frequency component to obtain four variables;
a filtering step S23: low-pass filtering is carried out on the four variables to obtain a direct current component U dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
PID control step S24: taking the target value of the output voltage as a given value, and taking the direct-current component U as a given value dpFltr As a feedback value, an output result U is obtained through PID control dpout Given value of 0, will beThe DC component U qpFltr 、U dnFltr And U qpFltr As feedback values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout For the positive sequence component compensation result, output result U dnout And output the result U qnout The result is compensated for the negative sequence component.
Specifically, the three-phase output voltages UN, VN and WN obtained by the voltage acquisition device are subjected to 3/2 conversion and double-DQ conversion to obtain positive and negative sequence components after three-phase voltage direct current conversion, and the calculation method is as follows, and the three-phase output voltages UN, VN and WN are subjected to 3/2 conversion and PARK conversion:
Figure BDA0003663282230000091
wherein U is α And U β Converting voltage for two phases, and performing positive and negative synchronous rotation coordinate transformation to obtain synchronous rotation angle
Figure BDA0003663282230000092
And the output result is obtained by performing closed-loop PID control on the Q-axis component.
Positive sequence transformation:
Figure BDA0003663282230000093
negative sequence transformation:
Figure BDA0003663282230000094
eliminating the double frequency component, and decoupling as follows:
Figure BDA0003663282230000095
decoupling variable U dp 、U qp 、U dn And U qn After passing through a low pass filter LPF, a direct current can be obtainedComponent U dpFltr 、U qpFltr 、U dnFltr And U qnFltr . The cut-off frequency of the low pass filter LPF should be set to 100Hz or less. Taking the target value SIV _ V of the output voltage as a given value, U dpFltr As a feedback value, an output result U is obtained through a PID controller dpout Similarly, 0 is used as the target value, U qpFltr 、U dnFltr And U qpFltr As a feedback value, an output result U is obtained through a PID controller qpout 、U dnout 、U qnout 。
Referring to fig. 5 and 11, fig. 5 is a flowchart of step S3 in fig. 3; fig. 11 is a PR control flowchart. As shown in fig. 5 and 11, the second compensation result obtaining step S3 includes:
zero-sequence voltage component acquisition step S31: obtaining the zero sequence voltage component by a symmetrical component method according to the three-phase output voltage;
PR control step S32: taking the zero sequence component as a feedback value and 0 as a target value, and obtaining an output result U through proportion-resonance control nout Output the result U nout And obtaining the zero sequence component compensation result.
Specifically, a symmetric component method is used for obtaining UN, VN and WN zero-sequence voltage components U 0 The following were used:
Figure BDA0003663282230000101
the three-phase voltage is divided into zero sequence components U 0 As a feedback value, 0 is used as a target value, and an output result U is obtained through a PR controller nout 。
Wherein, the PR controller is a proportional-resonant controller, and the expression of the s-domain transfer function is
Figure BDA0003663282230000102
K p Is a proportional link coefficient for increasing open-loop gain and control precision, K r Is a resonance link coefficient for reducing the steady state error of the system, omega c For offsetting angular frequency, for reference waveform at frequencyPositive and negative variation of, omega 0 Is the resonant angular frequency. General requirements ω 0 ＝2×π×50＝100π，ω c ＝2×π×0.5＝π。
Referring to fig. 6 and 12, fig. 6 is a flowchart of step S4 in fig. 3; fig. 12 is a schematic view of SVPWM modulation. As shown in fig. 6 and 12, the three-phase output voltage balancing step S4 includes:
a conversion step S41: respectively carrying out 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain three-phase conversion voltage, and obtaining first voltage, second voltage and third voltage according to the three-phase conversion voltage and the zero sequence component compensation result;
three-dimensional modulated wave voltage obtaining step S42: obtaining a three-dimensional modulation wave according to the first voltage, the second voltage and the third voltage through sector judgment, vector action time calculation and a seven-segment switch voltage vector action sequence;
control pulse obtaining step S43: comparing the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse of a switching device of each bridge arm corresponding to the inversion unit;
control adjustment step S44: and correspondingly controlling the action of each switching device according to each control pulse.
Wherein the control pulse obtaining step S43 includes:
and outputting high-level pulses when the triangular carrier wave is larger than the three-dimensional modulation wave, and outputting low-level pulses when the triangular carrier wave is smaller than the three-dimensional modulation wave.
Wherein the control adjusting step S44 includes: the switching devices of the upper bridge arm of each bridge arm are opposite in action to the switching devices of the lower bridge arm thereof.
Due to S n 、S 3 、S 4 、S 5 Three independent outputs can be determined, so a three-dimensional coordinate system xyz with three independent variables is required to describe the operating state of the inverter, as shown in fig. 8. Applying the x, y and z voltages obtained in the above steps on an xyz coordinate axis, wherein the x, y and z voltages are a first voltage and a second voltage respectivelyAnd a third voltage. Similar to the traditional SVPWM modulation technology, three-dimensional modulation wave voltage is obtained through sector judgment, vector action time calculation and seven-segment switch voltage vector action sequence, and then control pulse is obtained through comparison with triangular wave and applied to a power device. The sector judgment is as follows:
Figure BDA0003663282230000111
Figure BDA0003663282230000112
the parameter index for each sector can be calculated as follows:
RP＝1+k 1 +2×k 2 +4×k 3 +8×k 4 +16×k 5 +32×k 6 ；
and then obtaining a modulated wave comparison value through the voltage vector duty ratio calculation result in the following table 1 and a seven-segment voltage vector conversion table in the following table 2. Wherein u is dc Supporting capacitor C for inverter front end 4 Voltage, T x And duty cycle d, where T is scaled as follows s And the value of the period corresponding to the switching frequency of the inverter.
Figure BDA0003663282230000113
Table 1:
Figure BDA0003663282230000114
Figure BDA0003663282230000121
table 2:
Figure BDA0003663282230000122
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Figure BDA0003663282230000131
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Figure BDA0003663282230000141
referring to fig. 7, fig. 7 is a schematic structural diagram of a control device according to the present invention. As shown in fig. 7, the control device includes:
a voltage acquisition unit 11 that acquires a three-phase output voltage;
the first compensation result obtaining unit 12 obtains a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performs closed-loop control on the positive sequence component and the negative sequence component to obtain a positive sequence component compensation result and a negative sequence component compensation result;
a second compensation result obtaining unit 13, obtaining a zero-sequence voltage component of the three-phase output voltage by a symmetric component method according to the three-phase output voltage, and performing feedback compensation on the zero-sequence voltage component to obtain a zero-sequence component compensation result;
and the three-phase output voltage balancing unit 14 performs three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applies the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage.
Wherein the first compensation result obtaining unit 12 includes:
a two-phase conversion voltage obtaining module 121, which performs 3/2 conversion and PARK conversion on the three-phase output voltage to obtain a two-phase conversion voltage;
a double-DQ conversion module 122, which performs the positive-negative synchronous rotation coordinate conversion on the two-phase conversion voltage and removes a double frequency component to obtain four variables;
a low-pass filtering module 123 for performing a low on four of the variablesObtaining a DC component U by filtering dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
A PID control module 124 for setting the output voltage target value as a given value and converting the DC component U into the DC component dpFltr As a feedback value, an output result U is obtained through PID control dpout Taking 0 as a given value, and taking the direct current component U as a given value qpFltr 、U dnFltr And U qpFltr As feedback values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout For the positive sequence component compensation result, output result U dnout And output the result U qnout The result is compensated for the negative sequence component.
Wherein the second compensation result obtaining unit 13 includes:
a zero-sequence voltage component obtaining module 131, which obtains the zero-sequence voltage component according to the three-phase output voltage by a symmetric component method;
the PR control module 132 takes the zero-sequence component as a feedback value and 0 as a target value, and obtains an output result U through proportional-resonant control nout Output the result U nout And obtaining the zero sequence component compensation result.
Wherein the three-phase output voltage balancing unit 14 includes:
a transformation module 141, which performs 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain a three-phase transformation voltage, and obtains a first voltage, a second voltage, and a third voltage according to the three-phase transformation voltage and the zero sequence component compensation result;
the SVPWM modulation module 142 obtains a three-dimensional modulation wave according to the first voltage, the second voltage and the third voltage through sector judgment, vector action time calculation and a seven-segment switching voltage vector action sequence;
the control pulse obtaining module 143 compares the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse corresponding to the switching device of each bridge arm of the inverter unit;
and a control adjustment module 144 for correspondingly controlling the operation of each of the switching devices according to each of the control pulses.
In summary, the load carrying capacity of the single-phase load of the auxiliary converter is increased by adding the fourth bridge arm and the neutral line inductor and adopting a positive, negative and zero sequence voltage control algorithm. Under the same working condition, the simulation waveform of the control method provided by the invention is shown in fig. 8, the loading capacity of the single-phase load is greatly enhanced, and the problem of voltage imbalance under the working condition of non-power frequency isolation imbalance load is solved. The split capacitor scheme in the prior art greatly shortens the weight and the volume of a front-end supporting capacitor and a three-phase filter capacitor, reduces the stray inductance of a loop, and has certain advantages.
Although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (8)

1. A control method of a three-phase four-leg auxiliary converter is characterized in that an inversion unit of the three-phase four-leg auxiliary converter comprises a fourth leg, an output point of the fourth leg is connected with an alternating current output N line through an inductor, and the control method comprises the following steps:
a voltage acquisition step: collecting three-phase output voltage;
a first compensation result obtaining step: obtaining a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to obtain a positive sequence component compensation result and a negative sequence component compensation result;
a second compensation result obtaining step: obtaining a zero-sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage, and performing feedback compensation on the zero-sequence voltage component to obtain a zero-sequence component compensation result;
and (3) balancing three-phase output voltage: performing three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applying the control pulse to a bridge arm of the inverter unit to obtain a balanced three-phase output voltage;
wherein the first compensation result obtaining step comprises:
a two-phase conversion voltage obtaining step: 3/2 conversion and PARK conversion are carried out on the three-phase output voltage to obtain two-phase conversion voltage;
double DQ conversion step: carrying out positive and negative synchronous rotation coordinate transformation on the two-phase conversion voltage and eliminating a double frequency component to obtain four variables;
a filtering step: low-pass filtering is carried out on the four variables to obtain a direct current component U dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
PID control step: taking the target value of the output voltage as a given value, and taking the direct-current component U as a given value dpFltr As a feedback value, an output result U is obtained through PID control dpout Taking 0 as a given value, and taking the direct current component U as a given value qpFltr 、U dnFltr And U qpFltr As feedback values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout For the positive sequence component compensation result, output result U dnout And output the result U qnout The result is compensated for the negative sequence component.
2. The control method according to claim 1, wherein the second compensation result obtaining step includes:
a zero-sequence voltage component obtaining step: obtaining the zero sequence voltage component by a symmetrical component method according to the three-phase output voltage;
PR control step: taking the zero sequence component as a feedback value, taking 0 as a target value, and passing through a ratioExample-resonant control yields an output result U nout Output the result U nout And compensating the result for the zero sequence component.
3. The control method of claim 2, wherein the three-phase output voltage balancing step comprises:
a conversion step: respectively carrying out 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain three-phase conversion voltage, and obtaining first voltage, second voltage and third voltage according to the three-phase conversion voltage and the zero sequence component compensation result;
a three-dimensional modulated wave voltage obtaining step: obtaining a three-dimensional modulation wave according to the first voltage, the second voltage and the third voltage through sector judgment, vector action time calculation and a seven-segment switch voltage vector action sequence;
a control pulse obtaining step: comparing the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse of a switching device of each bridge arm corresponding to the inversion unit;
controlling and adjusting: and correspondingly controlling the action of each switching device according to each control pulse.
4. The control method according to claim 3, wherein the control pulse obtaining step includes:
and outputting high-level pulse when the triangular carrier is larger than the three-dimensional modulation wave, and outputting low-level pulse when the triangular carrier is smaller than the three-dimensional modulation wave.
5. The control method according to claim 4, wherein the control adjusting step includes: the switching devices of the upper bridge arm of each bridge arm are opposite in action to the switching devices of the lower bridge arm thereof.
6. A control device of a three-phase four-leg auxiliary converter is characterized in that an inversion unit of the three-phase four-leg auxiliary converter comprises a fourth leg, an output point of the fourth leg is connected with an alternating current output N line through an inductor, and the control device comprises:
the voltage acquisition unit acquires three-phase output voltage;
the first compensation result acquisition unit is used for acquiring a positive sequence component and a negative sequence component of the three-phase output voltage through positive and negative synchronous rotating coordinate transformation according to the three-phase output voltage, and performing closed-loop control on the positive sequence component and the negative sequence component to acquire a positive sequence component compensation result and a negative sequence component compensation result;
the second compensation result acquisition unit is used for acquiring a zero-sequence voltage component of the three-phase output voltage by a symmetrical component method according to the three-phase output voltage and carrying out feedback compensation on the zero-sequence voltage component to acquire a zero-sequence component compensation result;
the three-phase output voltage balancing unit is used for carrying out three-dimensional space rotation vector modulation according to the positive sequence component compensation result, the negative sequence component compensation result and the zero sequence component compensation result to obtain a control pulse, and applying the control pulse to a bridge arm of the inverter unit to obtain balanced three-phase output voltage;
wherein the first compensation result obtaining unit includes:
the two-phase conversion voltage obtaining module is used for carrying out 3/2 conversion and PARK conversion on the three-phase output voltage to obtain two-phase conversion voltage;
the double-DQ conversion module is used for carrying out positive and negative synchronous rotation coordinate conversion on the two-phase conversion voltage and eliminating a double frequency component to obtain four variables;
the low-pass filtering module is used for carrying out low-pass filtering on the four variables to obtain a direct-current component U dpFltr 、U qpFltr 、U dnFltr 、U qpFltr ；
A PID control module for taking the output voltage target value as a given value and taking the DC component U as a given value dpFltr As a feedback value, an output result U is obtained through PID control dpout Taking 0 as a given value, and taking the direct current component U as a given value qpFltr 、U dnFltr And U qpFltr As feedback values, respectively obtaining output results U through PID control qpout 、U dnout 、U qnout Wherein the result U is output dpout And output the result U qpout Compensating the result for the positive sequence component, outputting a result U dnout And output the result U qnout The result is compensated for the negative sequence component.
7. The control apparatus according to claim 6, wherein the second compensation result acquisition unit includes:
the zero-sequence voltage component acquisition module is used for acquiring the zero-sequence voltage component by a symmetrical component method according to the three-phase output voltage;
the PR control module takes the zero-sequence component as a feedback value and 0 as a target value to obtain an output result U through proportional-resonant control nout Output the result U nout And obtaining the zero sequence component compensation result.
8. The control device according to claim 7, wherein the three-phase output voltage balancing unit includes:
the transformation module is used for respectively carrying out 3/2 inverse transformation and PARK inverse transformation on the positive sequence component compensation result and the negative sequence component compensation result to obtain three-phase transformation voltage, and obtaining first voltage, second voltage and third voltage according to the three-phase transformation voltage and the zero sequence component compensation result;
the SVPWM module obtains a three-dimensional modulation wave through sector judgment, vector action time calculation and a seven-segment switch voltage vector action sequence according to the first voltage, the second voltage and the third voltage;
the control pulse obtaining module is used for comparing the three-dimensional modulation wave with a triangular carrier wave to obtain a control pulse corresponding to a switching device of each bridge arm of the inversion unit;
and the control regulating module correspondingly controls the action of each switching device according to each control pulse.
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