CN113541515A - Control method and terminal for AC/DC bus interface converter - Google Patents
Control method and terminal for AC/DC bus interface converter Download PDFInfo
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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
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc 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
- H02M7/217—Conversion of ac power input into dc 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
- H02M7/219—Conversion of ac power input into dc 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 in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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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
- 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
- H02M3/33576—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 having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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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
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc 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
- H02M7/217—Conversion of ac power input into dc 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
- H02M7/2173—Conversion of ac power input into dc 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 in a biphase or polyphase circuit arrangement
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
The invention discloses a control method and a terminal of an AC/DC bus interface converter, wherein the AC/DC bus interface converter comprises a three-phase full-bridge AC/DC converter and a DC transformer, the signal input end of the three-phase full-bridge AC/DC converter is used for connecting an AC microgrid, and the signal output end of the three-phase full-bridge AC/DC converter is used for connecting the signal input end of the DC microgrid through the DC transformer; meanwhile, the influence of double frequency pulsation of the first output voltage of the direct current transformer on the voltage of the direct current micro-grid bus is restrained by adding a voltage feedforward control mode to the direct current transformer, the safety of equipment is guaranteed, and the stable operation of a system is guaranteed.
Description
Technical Field
The invention relates to the technical field of micro-grids, in particular to a control method and a terminal of an AC/DC bus interface converter.
Background
The distributed renewable energy has the advantages of high flexibility, environmental protection, low carbon and the like, and is an effective constituent factor for realizing the carbon peak reaching and carbon neutralization targets in China. However, its uncertainty in output and the randomness of the load supply make it difficult to incorporate directly into a large grid. The microgrid couples together distributed power sources, loads, interface converters, protection equipment, and energy storage equipment. By the operation control and energy management of the micro-grid, the distributed power supply can be utilized to the maximum extent and adverse effects on the power quality of the large power grid can be avoided. According to different bus types, the micro-grid is divided into an alternating current micro-grid, a direct current micro-grid and an alternating current and direct current hybrid micro-grid. The alternating current-direct current hybrid micro-grid has the advantages of alternating current and direct current micro-grids, can be compatible with various alternating current and direct current loads and distributed power supplies, and greatly reduces power loss caused by a plurality of AC/DC or DC/AC converters. Therefore, the bidirectional AC/DC bus interface converter is a key device for connecting the AC/DC bus in the hybrid micro-grid. It is necessary to intensively study it.
Most of the existing documents propose non-isolated bidirectional AC/DC bus interface converters. However, common mode interference on the direct current side and the alternating current side of the bidirectional non-isolated AC/DC alternating current/direct current bus interface converter is serious. The introduction of the transformer is an effective means for electrical isolation and common-mode interference suppression on the two sides of alternating current and direct current.
Compared with the traditional power frequency transformer, the high-frequency direct current transformer has the advantages of small volume, light weight, low loss and wide application prospect. At present, a double-active bridge type direct current transformer (DAB-DCT) and a CLLC resonance type direct current transformer (CLLC-DCT) are two types of bidirectional direct current transformers with the best application prospect. The DAB-DCT has the advantages of high modularization degree, quick dynamic response and the like, and generally adopts phase-shift control. However, the DAB-DCT has large return power and narrow soft switching range, which reduces the operating efficiency. Compared with DAB-DCT, CLLC-DCT has the advantages of wide soft switching range, small electromagnetic interference, strong voltage regulation capability, high working efficiency and the like, and is suitable for being used in a micro-grid.
However, in an actual microgrid, the voltage of the ac microgrid is unbalanced due to the access of a high-power single-phase load on the ac side and the unbalanced distribution of the single-phase load in a three-phase system, so that the current asymmetry of the ac microgrid and the double-frequency ripple of the bus voltage of the dc microgrid are caused, and further, the electric energy is reduced, and even equipment is burned.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method and the terminal for controlling the AC/DC bus interface converter solve the problems of the asymmetry of AC microgrid current and the influence of the frequency doubling pulsation of DC microgrid bus voltage caused by the imbalance of the AC microgrid voltage, and ensure the safety of equipment.
In order to solve the technical problems, the invention adopts the technical scheme that:
the control method of the AC/DC bus interface converter comprises a three-phase full-bridge AC/DC converter and a DC transformer, wherein the signal input end of the three-phase full-bridge AC/DC converter is used for being connected with an AC micro-grid, the signal output end of the three-phase full-bridge AC/DC converter is used for being connected with the signal input end of the DC micro-grid through the DC transformer, and the DC transformer is a DC resonance converter based on a CLLC structure and comprises the following steps:
s1, when the voltage of the alternating-current microgrid is unbalanced, suppressing the negative sequence current of the three-phase full-bridge alternating-current and direct-current converter;
s2, collecting a first output voltage of the direct current transformer;
and S3, controlling the direct current transformer to output a second output voltage according to the first output voltage so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
In order to solve the technical problem, the invention adopts another technical scheme as follows:
the utility model provides an alternating current-direct current bus interface converter control terminal, alternating current-direct current bus interface converter includes three-phase full-bridge alternating current-direct current converter and direct current transformer, the signal input part of three-phase full-bridge alternating current-direct current converter is used for connecting the little electric wire netting of alternating current, the signal output part of three-phase full-bridge alternating current-direct current converter is used for passing through direct current transformer connects the output of the little electric wire netting of direct current, direct current transformer is the direct current resonance converter based on CLLC structure, including memory, treater and storage on the memory and can computer program of operation on the treater, the treater respectively with the control signal input part of three-phase full-bridge alternating current-direct current converter and direct current transformer's control signal input part links to each other, the treater execution realize following step during the computer program:
s1, when the voltage of the alternating-current microgrid is unbalanced, suppressing the negative sequence current of the three-phase full-bridge alternating-current and direct-current converter;
s2, collecting a first output voltage of the direct current transformer;
and S3, controlling the direct current transformer to output a second output voltage according to the first output voltage so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
In conclusion, the beneficial effects of the invention are as follows: when the voltage of an alternating current micro-grid is unbalanced, current waveforms generated by the alternating current micro-grid on the alternating current side of a three-phase full-bridge alternating current-direct current converter become symmetrical and sinusoidal by restraining the negative sequence current of the three-phase full-bridge alternating current-direct current converter in the alternating current-direct current bus interface converter; meanwhile, the influence of double frequency pulsation of the first output voltage of the direct current transformer on the voltage of the direct current micro-grid bus is restrained by adding a voltage feedforward control mode to the direct current transformer, the safety of equipment is guaranteed, and the stable operation of a system is guaranteed.
Drawings
Fig. 1 is a schematic step diagram of a method for controlling an ac/dc bus interface converter according to an embodiment of the present invention;
fig. 2 is a connection structure diagram of an ac/dc bus interface converter in the control method of the ac/dc bus interface converter according to the embodiment of the present invention;
fig. 3 is a timing diagram illustrating control of a dc transformer in the method for controlling an ac/dc bus interface converter according to the embodiment of the present invention;
fig. 4 is a system block diagram of a control terminal of an ac/dc bus interface converter according to an embodiment of the present invention.
Description of reference numerals:
1. an alternating current microgrid; 2. a three-phase full-bridge AC-DC converter; 3. a DC transformer; 4. a direct current microgrid; 5. a control terminal of an AC/DC bus interface converter; 6. a processor; 7. a memory.
Detailed Description
In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.
Referring to fig. 1 to 3, a method for controlling an ac/dc bus interface converter includes a three-phase full-bridge ac/dc converter 2 and a dc transformer 3, where a signal input end of the three-phase full-bridge ac/dc converter 2 is used to connect to an ac microgrid 1, a signal output end of the three-phase full-bridge ac/dc converter 2 is used to connect to a signal input end of a dc microgrid 4 through the dc transformer 3, and the dc transformer 3 is a dc resonant converter based on a CLLC structure, and includes the following steps:
s1, when the voltage of the alternating-current microgrid 1 is unbalanced, suppressing the negative-sequence current of the three-phase full-bridge alternating-current and direct-current converter 2;
s2, collecting a first output voltage of the direct current transformer 3;
and S3, controlling the direct current transformer 3 to output a second output voltage according to the first output voltage so as to suppress the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
From the above description, the beneficial effects of the present invention are: when the voltage of an alternating current micro-grid 1 is unbalanced, the negative sequence current of a three-phase full-bridge alternating current-direct current converter 2 in the alternating current-direct current bus interface converter is suppressed, so that the current waveform generated by the alternating current micro-grid 1 on the alternating current side of the three-phase full-bridge alternating current-direct current converter 2 becomes symmetrical and sinusoidal; meanwhile, by adding a voltage feedforward control mode to the direct current transformer 3, the influence of double frequency pulsation of the first output voltage of the direct current transformer 3 on the bus voltage of the direct current micro-grid 4 is inhibited, the safety of equipment is guaranteed, and the stable operation of the system is guaranteed.
Further, the step S3 specifically includes:
s30, calculating a deviation value of the first output voltage and a preset voltage value, and performing linear synthesis on the deviation value to obtain a first control frequency;
s31, performing proportional resonance control on the input voltage of the direct current transformer 3 to obtain a second control frequency;
s32, adding the first control frequency, the second control frequency and the resonant frequency of the dc transformer 3 to obtain a third control frequency;
and S33, controlling the dc transformer 3 to output the second output voltage through the third control frequency, so as to suppress an influence of a frequency doubling ripple of the first output voltage on the second output voltage.
As is apparent from the above description, the resonance type dc transformer 3 adjusts the output voltage by changing the output impedance of the load by changing the switching frequency of the switching tube. When the dc transformer 3 is the resonant dc transformer 3, the first output voltage, the input voltage data, and the like of the dc transformer 3 are used as important data bases for generating the third control frequency, so as to control the switching frequency of the resonant dc transformer 3, so as to adjust the output voltage of the dc transformer 3, thereby suppressing the influence of the double frequency ripple of the first output voltage of the dc transformer 3 on the bus voltage of the dc microgrid 4.
Further, the linear synthesis of the deviation value to obtain the first control frequency specifically includes:
performing PI regulation on the deviation value to obtain a control quantity for controlling the direct current transformer 3;
and recording the control quantity as the first control frequency.
As can be seen from the above description, the first control frequency is generated by linearly combining the proportion and the integral of the deviation value, which can improve the operation stability of the dc transformer 3 and reduce the error caused by the frequency doubling ripple of the bus voltage of the dc microgrid 4.
Further, the step S32 is specifically:
an ac double frequency component of the input voltage of the dc transformer 3 is extracted as the second control frequency by a PR regulator.
As can be seen from the above description, the PR regulator extracts the ac double frequency component of the input voltage of the dc transformer 3 to perform a compensation function, so as to gain the ac signal with the resonant frequency and improve the control accuracy.
Further, the step S33 is specifically:
performing pulse frequency modulation on the third control frequency to obtain a driving signal;
and driving and controlling the direct current transformer 3 to output the second output voltage by using the driving signal so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
As is apparent from the above description, the pulse frequency modulation is used to convert the control frequency into a pulse signal for controlling the switching tube of the resonance type dc transformer 3.
Further, the step S1 is specifically:
when the voltage of the alternating-current micro-grid 1 is unbalanced, generating a positive sequence current instruction and a negative sequence current instruction of the three-phase full-bridge alternating-current-direct-current converter 2 in a synchronous rotating coordinate system;
and performing feedforward decoupling control on the three-phase full-bridge alternating current-direct current converter 2 according to the positive sequence current instruction and the negative sequence current instruction to complete the suppression of the negative sequence current.
As can be seen from the above description, the specific content of the negative-sequence current of the three-phase full-bridge ac/dc converter 2 is to convert the operating parameters of the three-phase full-bridge ac/dc converter 2 into a mathematical model of a synchronous rotating coordinate system for analysis when the ac microgrid 1 has an unbalanced voltage, so as to generate a corresponding current command for continuously controlling the three-phase full-bridge ac/dc converter 2.
Further, the generating of the positive sequence current command and the negative sequence current command of the three-phase full-bridge ac-dc converter 2 in the synchronous rotating coordinate system specifically includes:
calculating a positive sequence component and a negative sequence component of the three-phase voltage of the three-phase full-bridge AC/DC converter 2 in the synchronous rotating coordinate system by a symmetrical component method, and further calculating the transmission power of the three-phase full-bridge AC/DC converter 2 in the synchronous rotating coordinate system;
establishing a coordinate system according to the positive sequence voltage vector, and calculating the steady-state component of active power and the steady-state component of reactive power in the transmission power;
and converting the steady-state component of the work power and the steady-state component of the reactive power to obtain the positive sequence current instruction and the negative sequence current instruction.
As can be seen from the above description, in order to calculate the specific calculation process of the positive sequence current command and the negative sequence current command, the control method of the three-phase full-bridge ac/dc converter 2 under the unbalanced condition is obtained by using mathematical analysis and calculation under the synchronous rotation coordinate system.
Referring to fig. 4, a control terminal 5 of an ac/dc bus interface converter includes a three-phase full-bridge ac/dc converter 2 and a dc transformer 3, the signal input end of the three-phase full-bridge AC/DC converter 2 is used for connecting with an AC micro-grid 1, the signal output end of the three-phase full-bridge AC/DC converter 2 is used for connecting with the output end of a DC micro-grid 4 through the DC transformer 3, and the three-phase full-bridge AC/DC converter comprises a memory 7, a processor 6 and a computer program which is stored on the memory 7 and can be operated on the processor 6, the processor 6 is respectively connected with the control signal input end of the three-phase full-bridge AC/DC converter 2 and the control signal input end of the DC transformer 3, the dc transformer 3 is a dc resonant converter based on a CLLC structure, and the processor 6 implements the following steps when executing the computer program:
s1, when the voltage of the alternating-current microgrid 1 is unbalanced, suppressing the negative-sequence current of the three-phase full-bridge alternating-current and direct-current converter 2;
s2, collecting a first output voltage of the direct current transformer 3;
and S3, controlling the direct current transformer 3 to output a second output voltage according to the first output voltage so as to suppress the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
From the above description, the beneficial effects of the present invention are: when the voltage of an alternating current micro-grid 1 is unbalanced, the negative sequence current of a three-phase full-bridge alternating current-direct current converter 2 in the alternating current-direct current bus interface converter is suppressed, so that the current waveform generated by the alternating current micro-grid 1 on the alternating current side of the three-phase full-bridge alternating current-direct current converter 2 becomes symmetrical and sinusoidal; meanwhile, by adding a voltage feedforward control mode to the direct current transformer 3, the influence of double frequency pulsation of the first output voltage of the direct current transformer 3 on the bus voltage of the direct current micro-grid 4 is inhibited, the safety of equipment is guaranteed, and the stable operation of the system is guaranteed.
Further, the step S3 specifically includes:
s30, calculating a deviation value of the first output voltage and a preset voltage value, and performing linear synthesis on the deviation value to obtain a first control frequency;
s31, performing proportional resonance control on the input voltage of the direct current transformer 3 to obtain a second control frequency;
s32, adding the first control frequency, the second control frequency and the resonant frequency of the dc transformer 3 to obtain a third control frequency;
and S33, controlling the dc transformer 3 to output the second output voltage through the third control frequency, so as to suppress an influence of a frequency doubling ripple of the first output voltage on the second output voltage.
As is apparent from the above description, the resonance type dc transformer 3 adjusts the output voltage by changing the output impedance of the load by changing the switching frequency of the switching tube. When the dc transformer 3 is the resonant dc transformer 3, the first output voltage, the input voltage data, and the like of the dc transformer 3 are used as important data bases for generating the third control frequency, so as to control the switching frequency of the resonant dc transformer 3, so as to adjust the output voltage of the dc transformer 3, thereby suppressing the influence of the double frequency ripple of the first output voltage of the dc transformer 3 on the bus voltage of the dc microgrid 4.
Further, the linear synthesis of the deviation value to obtain the first control frequency specifically includes:
performing PI regulation on the deviation value to obtain a control quantity for controlling the direct current transformer 3;
and recording the control quantity as the first control frequency.
From the above description, it can be known that, the first control frequency is generated by linear combination of the proportion and the integral of the deviation value, so that the operation stability of the dc transformer 3 can be improved, and the error caused by the frequency doubling ripple of the bus voltage of the dc microgrid 4 can be reduced.
Referring to fig. 1 and fig. 2, a first embodiment of the present invention is:
as shown in fig. 1 and 2, the ac/dc bus interface converter includes a three-phase full-bridge ac/dc converter 2 and a dc transformer 3, a signal input end of the three-phase full-bridge ac/dc converter 2 is used for connecting an ac microgrid 1, a signal output end of the three-phase full-bridge ac/dc converter 2 is used for connecting a signal input end of a dc microgrid 4 through the dc transformer 3, and the dc transformer 3 is a dc resonant converter based on a CLLC structure, including the following steps:
s1, when the voltage of the alternating-current microgrid 1 is unbalanced, inhibiting the negative-sequence current of the three-phase full-bridge alternating-current and direct-current converter 2;
s2, collecting a first output voltage of the direct current transformer 3;
and S3, controlling the DC transformer 3 to output a second output voltage according to the first output voltage so as to suppress the influence of the frequency doubling ripple of the first output voltage on the second output voltage.
In the embodiment, when the voltage of the alternating-current microgrid 1 is unbalanced, the negative-sequence current of the three-phase full-bridge alternating-current/direct-current converter 2 in the alternating-current/direct-current bus interface converter is suppressed, so that the current waveform generated by the alternating-current microgrid 1 on the alternating-current side of the three-phase full-bridge alternating-current/direct-current converter 2 becomes symmetrical and sinusoidal; meanwhile, by adding a voltage feedforward control mode to the direct current transformer 3, the influence of double frequency pulsation of the first output voltage of the direct current transformer 3 on the bus voltage of the direct current microgrid 4 is inhibited, so that the negative problem caused by unbalanced voltage of the alternating current microgrid 1 is solved, and the stable operation of an alternating current/direct current system is ensured.
Referring to fig. 2 and fig. 3, a second embodiment of the present invention is:
based on the first embodiment, as shown in the figure, the dc transformer 3 is a resonant dc transformer 3, and step S3 specifically includes:
s30, calculating a deviation value of the first output voltage and a preset voltage value, and performing linear synthesis on the deviation value to obtain a first control frequency;
in this embodiment, as shown in fig. 3 specifically, a deviation value between the first output voltage and the preset voltage value is subjected to a linear combination of proportion and integration by the PI regulator to obtain a control quantity, i.e., a first control frequency. Wherein, V0Representing the output voltage, V, of the DC transformer 30Representing a preset voltage value; f. of1Representing the first control frequency.
And S31, performing proportional resonance control on the input voltage of the direct current transformer 3 to obtain a second control frequency.
In the present embodiment, as shown in fig. 3 in particular, the ac double frequency component of the input voltage of the dc transformer 3 is extracted as the second control frequency by the PR regulator. Wherein, VabRepresenting an input voltage; f. of2Representing the second control frequency.
S32, adding the first control frequency, the second control frequency and the resonance frequency of the direct current transformer 3 to obtain a third control frequency;
and S33, controlling the DC transformer 3 to output the second output voltage through the third control frequency so as to inhibit the influence of the frequency doubling pulsation of the first output voltage on the second output voltage.
In this embodiment, as shown in fig. 3, a third control frequency obtained by adding the first control frequency, the second control frequency, and the resonant frequency of the dc transformer 3 is pulse-width modulated by the PFM regulator to obtain a driving signal, and the driving signal is used to control the dc transformer 3. Wherein f isrRepresents the resonant frequency; f. ofsRepresents a third control frequency; vg represents the drive signal.
Referring to fig. 2, a third embodiment of the present invention is:
on the basis of the first or second embodiment, as shown in fig. 2, the step S1 specifically includes:
when the voltage of the alternating-current micro-grid 1 is unbalanced, a positive sequence current instruction and a negative sequence current instruction of the three-phase full-bridge alternating-current-direct-current converter 2 in a synchronous rotating coordinate system are generated.
The specific process of generating the positive sequence current command and the negative sequence current command is as follows:
firstly, a positive sequence component and a negative sequence component of the three-phase voltage of the three-phase full-bridge AC/DC converter 2 in a synchronous rotating coordinate system are calculated by a symmetrical component method. The concrete expression is as follows:
wherein e isa、ebAnd ecRepresents the three-phase voltage of the ac microgrid 1; c23Representing a static coordinate variation matrix; r (theta) represents a positive sequence rotation coordinate transformation matrix; r (-theta) represents a negative sequence rotation coordinate transformation matrix;
and
a positive sequence component representing a three-phase fundamental electromotive force;
and
representing the negative sequence component of the three-phase fundamental electromotive force.
Then, the transmission power of the three-phase full-bridge ac/dc converter 2 in the synchronous rotating coordinate system is calculated, and the expression is as follows:
wherein,
and
represents the positive sequence component of the three-phase fundamental current;
and
represents the negative sequence component of the three-phase fundamental current; p is a radical of0Representing the steady-state component of active power; q. q.s0Reactive power steady state component. In the present embodiment, only the active power steady-state component and the reactive power steady-state component are considered.
Then, a coordinate system is established with the positive sequence voltage vectors, i.e.
The negative sequence component of the three-phase fundamental current is made to be 0, and the active power steady-state component and the reactive power steady-state component in the transmission power are calculated to obtain the following expression:
and then, converting the steady-state component of the work power and the steady-state component of the reactive power to obtain a positive sequence current instruction and a negative sequence current instruction. The expression for the positive sequence circuit instruction is as follows:
the PI regulation is performed on the dc bus voltage of the three-phase full-bridge ac/dc converter 2 to obtain active power corresponding to the dc side voltage, and the expression is as follows:
wherein, K1And K2Respectively representing a proportional coefficient and an integral coefficient of PI regulation; s represents the transfer function of the PI regulator; u shape2Represents the dc bus voltage; u shape1Representing a reference value for the dc bus voltage. Q furthermore0And when the active power steady-state component is equal to 0, substituting the expression of the active power steady-state component into a positive sequence circuit instruction to obtain a negative sequence current instruction.
And finally, performing feedforward decoupling control on the three-phase full-bridge AC/DC converter 2 according to the positive sequence current instruction and the negative sequence current instruction to complete the suppression of the negative sequence current.
Referring to fig. 4, a fourth embodiment of the present invention is:
as shown in fig. 4, the ac/dc bus interface converter control terminal 5 includes a three-phase full-bridge ac/dc converter 2 and a dc transformer 3, a signal input end of the three-phase full-bridge ac/dc converter 2 is used for connecting an ac microgrid 1, a signal output end of the three-phase full-bridge ac/dc converter 2 is used for connecting an output end of the dc microgrid 4 through the dc transformer 3, and the ac/dc bus interface converter control terminal includes a memory 7, a processor 6 and a computer program stored in the memory 7 and operable on the processor 6, the processor 6 is respectively connected to a control signal input end of the three-phase full-bridge ac/dc converter 2 and a control signal input end of the dc transformer 3, and the processor 6 executes one of the ac/dc bus interface converter control methods in the first, second or third embodiments.
In summary, the invention discloses a method and a terminal for controlling an ac/dc bus interface converter, when an ac microgrid has a voltage imbalance, a current command is calculated through a mathematical model established under a synchronous rotating coordinate system to control a three-phase ac/dc full-bridge converter, so as to suppress a negative sequence current of the three-phase full-bridge ac/dc converter in the ac/dc bus interface converter, and to make a current waveform generated by the ac microgrid on an ac side of the three-phase full-bridge ac/dc converter become symmetrical and sinusoidal; meanwhile, a voltage feedforward control mode is added to the direct current transformer, the first output voltage, the input voltage and the resonant frequency are combined to obtain a control quantity for controlling the direct current transformer, the influence of double frequency pulsation of the first output voltage of the direct current transformer on the direct current micro-grid bus voltage is restrained, the equipment safety is guaranteed, and the stable operation of a system is guaranteed.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent modifications made by the contents of the present specification and the drawings, or applied to the related technical fields directly or indirectly, are included in the scope of the present invention.
Claims (10)
1. The control method of the AC/DC bus interface converter comprises a three-phase full-bridge AC/DC converter and a DC transformer, wherein a signal input end of the three-phase full-bridge AC/DC converter is used for being connected with an AC micro-grid, a signal output end of the three-phase full-bridge AC/DC converter is used for being connected with a signal input end of the DC micro-grid through the DC transformer, and the DC transformer is a DC resonance converter based on a CLLC structure, and is characterized by comprising the following steps:
s1, when the voltage of the alternating-current microgrid is unbalanced, suppressing the negative sequence current of the three-phase full-bridge alternating-current and direct-current converter;
s2, collecting a first output voltage of the direct current transformer;
and S3, controlling the direct current transformer to output a second output voltage according to the first output voltage so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
2. The ac-dc bus interface converter control method according to claim 1, wherein the step S3 specifically includes:
s30, calculating a deviation value of the first output voltage and a preset voltage value, and performing linear synthesis on the deviation value to obtain a first control frequency;
s31, performing proportional resonance control on the input voltage of the direct current transformer to obtain a second control frequency;
s32, adding the first control frequency, the second control frequency and the resonance frequency of the direct current transformer to obtain a third control frequency;
and S33, controlling the direct current transformer to output the second output voltage through the third control frequency so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
3. The method according to claim 2, wherein the linear synthesis of the deviation value to obtain the first control frequency specifically comprises:
performing PI regulation on the deviation value to obtain a control quantity for controlling the direct current transformer;
and recording the control quantity as the first control frequency.
4. The ac-dc bus interface converter control method according to claim 2, wherein the step S32 specifically includes:
extracting an alternating current double frequency component of the input voltage of the direct current transformer as the second control frequency through a PR regulator.
5. The ac-dc bus interface converter control method according to claim 2, wherein the step S33 specifically includes:
performing pulse frequency modulation on the third control frequency to obtain a driving signal;
and driving and controlling the direct current transformer to output the second output voltage by using the driving signal so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
6. The ac-dc bus interface converter control method according to claim 1, wherein the step S1 specifically includes:
when the voltage of the alternating-current micro-grid is unbalanced, generating a positive sequence current instruction and a negative sequence current instruction of the three-phase full-bridge alternating-current-direct-current converter under a synchronous rotating coordinate system;
and performing feedforward decoupling control on the three-phase full-bridge alternating current-direct current converter according to the positive sequence current instruction and the negative sequence current instruction to complete the suppression of the negative sequence current.
7. The ac-dc bus interface converter control method according to claim 6, wherein the generating of the positive-sequence current command and the negative-sequence current command of the three-phase full-bridge ac-dc converter in the synchronous rotating coordinate system specifically comprises:
calculating a positive sequence component and a negative sequence component of a three-phase voltage of the three-phase full-bridge AC-DC converter under the synchronous rotating coordinate system by a symmetrical component method, and further calculating the transmission power of the three-phase full-bridge AC-DC converter under the synchronous rotating coordinate system;
establishing a coordinate system according to the positive sequence voltage vector, and calculating the steady-state component of active power and the steady-state component of reactive power in the transmission power;
and converting the steady-state component of the work power and the steady-state component of the reactive power to obtain the positive sequence current instruction and the negative sequence current instruction.
8. The utility model provides an alternating current-direct current bus interface converter control terminal, alternating current-direct current bus interface converter includes three-phase full-bridge alternating current-direct current converter and direct current transformer, the signal input part of three-phase full-bridge alternating current-direct current converter is used for connecting the little electric wire netting of alternating current, the signal output part of three-phase full-bridge alternating current-direct current converter is used for passing through direct current transformer connects the output of the little electric wire netting of direct current, direct current transformer is the direct current resonance converter based on CLLC structure, its characterized in that, including memory, treater and storage on the memory and can computer program of operation on the treater, the treater respectively with the control signal input part of three-phase full-bridge alternating current-direct current converter and direct current transformer's control signal input part links to each other, the treater is executed realize following step during the computer program:
s1, when the voltage of the alternating-current microgrid is unbalanced, suppressing the negative sequence current of the three-phase full-bridge alternating-current and direct-current converter;
s2, collecting a first output voltage of the direct current transformer;
and S3, controlling the direct current transformer to output a second output voltage according to the first output voltage so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
9. The ac-dc bus interface converter control terminal according to claim 7, wherein the step S3 specifically includes:
s30, calculating a deviation value of the first output voltage and a preset voltage value, and performing linear synthesis on the deviation value to obtain a first control frequency;
s31, performing proportional resonance control on the input voltage of the direct current transformer to obtain a second control frequency;
s32, adding the first control frequency, the second control frequency and the resonance frequency of the direct current transformer to obtain a third control frequency;
and S33, controlling the direct current transformer to output the second output voltage through the third control frequency so as to inhibit the influence of frequency doubling pulsation of the first output voltage on the second output voltage.
10. The ac-dc bus interface converter control terminal of claim 7, wherein the linear synthesis of the deviation value to obtain the first control frequency specifically comprises:
performing PI regulation on the deviation value to obtain a control quantity for controlling the direct current transformer;
and recording the control quantity as the first control frequency.
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