CN111697611B - Direct-current side voltage indirect control method applied to multi-terminal flexible power transmission system - Google Patents

Direct-current side voltage indirect control method applied to multi-terminal flexible power transmission system Download PDF

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CN111697611B
CN111697611B CN202010507235.5A CN202010507235A CN111697611B CN 111697611 B CN111697611 B CN 111697611B CN 202010507235 A CN202010507235 A CN 202010507235A CN 111697611 B CN111697611 B CN 111697611B
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voltage
current
phase
power transmission
direct
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CN111697611A (en
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刘进军
宋曙光
杜思行
陈星星
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Xian Jiaotong University
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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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • 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
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a direct current side voltage indirect control method applied to a multi-terminal flexible power transmission system, which comprises the following steps of: 1) replacing a direct-current side voltage controller in the rectifying side MMC system by a total capacitance voltage controller; 2) solving the amplitude and the phase of a modulation signal, output current and circulation current in the rectification side MMC system under the dq rotation coordinate system; 3) calculating a voltage compensation signal in real time according to the amplitude and the phase of a modulation signal, an output current and a circulating current in the MMC system at the rectifying side
Figure DDA0002526998070000011
4) Compensating the voltage compensation signal obtained in the step 3)
Figure DDA0002526998070000012
And adding the voltage command into the voltage commands of the upper and lower bridge arms to obtain final voltage commands of the upper and lower bridge arms, and then controlling the direct-current side voltage of the multi-terminal flexible power transmission system according to the final voltage commands of the upper and lower bridge arms.

Description

Direct-current side voltage indirect control method applied to multi-terminal flexible power transmission system
Technical Field
The invention belongs to the technical field of modular multilevel converters in power electronics, and relates to a direct-current side voltage indirect control method applied to a multi-terminal flexible power transmission system.
Background
With the wide application of high-power electronic conversion devices, the multilevel conversion technology is rapidly developed. Modular Multilevel Converter (MMC) is a novel Multilevel voltage source Converter, which has been proposed since the beginning of 2000, because it has the advantages of Modular characteristics, easy expansion, convenient assembly, high quality output and high voltage level, and the like, it is a research hotspot in recent years, and it has obvious advantages in the field of medium and high voltage applications. At present, the MMC has been widely used in the field of High Voltage Direct Current (HVDC) transmission, and multiple lines have been put into operation, such as TransBayCable engineering in the united states, south australia three-terminal flexible dc transmission engineering in china, and a navian five-terminal flexible dc transmission system.
In order to maintain stable operation of the multi-terminal flexible power transmission system, the voltage on the direct current side of the multi-terminal flexible power transmission system must be well controlled. Currently, to control the dc side voltage, it relies on measuring the dc side voltage. In HVDC systems, the dc side voltage is typically up to several hundred kilovolts, and reliable measuring instruments are required to achieve voltage measurements. According to the national standard, a typical dc voltage measuring device of a high-voltage dc transmission system includes a dc voltage divider, a dc voltage measuring device, a converter, a transmission system, etc. It must meet the design requirements of digital quantity, external insulation requirements, painting and rust prevention requirements, electromagnetic compatibility requirements, radio interference voltage requirements and the like. Therefore, the whole direct-current voltage measuring system is complex and high in cost, and when the measuring system breaks down, the direct-current side voltage of the system cannot be effectively controlled.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a direct-current side voltage indirect control method applied to a multi-terminal flexible power transmission system, which can realize effective control of the direct-current side voltage of the system and has lower complexity and cost of the system.
In order to achieve the above object, the indirect control method for dc side voltage applied to a multi-terminal flexible power transmission system according to the present invention comprises the following steps:
1) replacing a direct-current side voltage controller in the rectifying side MMC system by a total capacitance voltage controller;
2) solving the amplitude and the phase of a modulation signal, output current and circulation current in the rectification side MMC system under the dq rotation coordinate system;
3) according to the amplitude and the phase of a modulation signal, output current and circulation current in the MMC system at the rectifying side in real timeCalculating a voltage compensation signal
Figure BDA0002526998050000021
4) Compensating the voltage compensation signal obtained in the step 3)
Figure BDA0002526998050000022
And adding the voltage command into the voltage commands of the upper and lower bridge arms to obtain final voltage commands of the upper and lower bridge arms, and then controlling the direct-current side voltage of the multi-terminal flexible power transmission system according to the final voltage commands of the upper and lower bridge arms.
In step 2), the modulation ratio M and the phase α of the modulation signal of the multi-terminal flexible power transmission system are respectively:
Figure BDA0002526998050000023
wherein the content of the first and second substances,
Figure BDA0002526998050000024
which represents the command voltage of the d-axis,
Figure BDA0002526998050000025
which represents the q-axis command voltage,
Figure BDA0002526998050000026
indicating the dc side rated voltage.
Under dq rotation coordinate system, the amplitude I of the output current of the multi-terminal flexible power transmission systemoAnd phase
Figure BDA0002526998050000031
Comprises the following steps:
Figure BDA0002526998050000032
wherein idRepresenting d-axis current, iqRepresenting the q-axis current.
Under dq rotating coordinate system, the amplitude I of the circulating current of the multi-terminal flexible power transmission system2And phase beta2Comprises the following steps:
Figure BDA0002526998050000033
wherein icir,dRepresenting d-axis flow, icir,qRepresenting q-axis circulation.
The specific operation of the step 3) is as follows:
calculating a voltage compensation signal in the controller according to the MMC steady state analysis model
Figure BDA0002526998050000034
Wherein the content of the first and second substances,
Figure BDA0002526998050000035
the specific operation of the step 4) is as follows:
compensating the voltage signal
Figure BDA0002526998050000036
Switching function S acting on upper and lower bridge arms respectivelyU(t) and SL(t) finally, the control of the phase capacitor voltage is realized, wherein the switching functions S of the upper and lower bridge armsU(t) and SL(t) are respectively:
Figure BDA0002526998050000037
compared with the existing control method, the method has the following beneficial effects:
in the direct current side voltage indirect control method applied to the multi-terminal flexible power transmission system, during specific operation, a direct current side voltage controller in a rectification side MMC system is replaced by a total capacitance voltage controller, the amplitude and the phase of a modulation signal, output current and circulating current in the rectification side MMC system are solved, and a voltage compensation signal is calculated according to the amplitude and the phase
Figure BDA0002526998050000041
Then using the voltage compensation signal
Figure BDA0002526998050000042
The voltage command is generated and the direct current side voltage of the multi-terminal flexible power transmission system is controlled, and the method has the advantages that an additional direct current side voltage measuring device is not needed, the complexity and the cost of the system are reduced, the reliability is higher when the measuring device fails, the voltage compensation signal is obtained by adopting a real-time calculation mode, the control effect is good, and the like.
Drawings
FIG. 1 is a corresponding MMC control block diagram of the present invention;
FIG. 2 is a diagram of DC side voltage waveforms when active power of the system dynamically changes according to the present invention;
FIG. 3 is a diagram of DC side voltage waveforms when the reactive power of the system dynamically changes according to the present invention;
fig. 4 is a voltage waveform diagram of the dc side when the active power and the reactive power of the system dynamically change simultaneously in the invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the invention discloses a direct-current side voltage indirect control method applied to a multi-terminal flexible power transmission system, which comprises the following steps of:
1) replacing a direct-current side voltage controller in the rectifying side MMC system by a total capacitance voltage controller;
2) solving the amplitude and the phase of a modulation signal, output current and circulation current in the rectification side MMC system under the dq rotation coordinate system;
3) calculating a voltage compensation signal in real time according to the amplitude and the phase of a modulation signal, an output current and a circulating current in the MMC system at the rectifying side
Figure BDA0002526998050000051
4) Compensating the voltage compensation signal obtained in the step 3)
Figure BDA0002526998050000052
And adding the voltage command into the voltage commands of the upper and lower bridge arms to obtain final voltage commands of the upper and lower bridge arms, and then controlling the direct-current side voltage of the multi-terminal flexible power transmission system according to the final voltage commands of the upper and lower bridge arms.
The specific operation of the step 1) is as follows:
in the existing direct current side voltage controller in the rectification side MMC system, the direct current side voltage controller needs to measure the direct current side voltage of the system to realize control, and in the method, the direct current side voltage controller is replaced by a total capacitance voltage controller.
In step 2), the modulation ratio M and the phase α of the modulation signal of the multi-terminal flexible power transmission system are respectively:
Figure BDA0002526998050000053
wherein the content of the first and second substances,
Figure BDA0002526998050000054
which represents the command voltage of the d-axis,
Figure BDA0002526998050000055
which represents the q-axis command voltage,
Figure BDA0002526998050000056
indicating the dc side rated voltage.
Under dq rotation coordinate system, the amplitude I of the output current of the multi-terminal flexible power transmission systemoAnd phase
Figure BDA0002526998050000057
Comprises the following steps:
Figure BDA0002526998050000061
wherein idRepresenting d-axis current, iqRepresenting the q-axis current.
Under dq rotating coordinate system, the amplitude I of the circulating current of the multi-terminal flexible power transmission system2And phase beta2Comprises the following steps:
Figure BDA0002526998050000062
wherein icir,dRepresenting d-axis flow, icir,qRepresenting q-axis circulation.
The specific operation of the step 3) is as follows:
calculating a voltage compensation signal in the controller according to the MMC steady state analysis model
Figure BDA0002526998050000063
Wherein the content of the first and second substances,
Figure BDA0002526998050000064
the specific operation of the step 4) is as follows:
compensating the voltage signal
Figure BDA0002526998050000065
Switching function S acting on upper and lower bridge arms respectivelyU(t) and SL(t) and finally realizing the control of the phase capacitance voltage, wherein the switching functions S of the upper and lower bridge armsU(t) and SL(t) are respectively:
Figure BDA0002526998050000066
simulation experiment
The circuit parameter settings are shown in table 1:
TABLE 1
Figure BDA0002526998050000071
Fig. 2 is a voltage waveform diagram of the dc side of the system when the present invention is applied during the active power dynamic change process of the system, and it can be found by comparison that after the present invention is applied, the voltage of the dc side is well maintained at the rated value of 320kV, and when the control is not applied, the voltage of the dc side has a deviation. Fig. 3 shows a voltage waveform diagram of the dc side of the system when the present invention is applied during the dynamic change of the reactive power of the system. After the invention is applied, the voltage of the direct current side is well kept at the rated value of 320kV, and when the control is not carried out, the voltage deviation of the direct current side is changed greatly. Fig. 4 shows a voltage waveform diagram of the dc side of the system when the present invention is applied in the process of the active power and the reactive power of the system changing dynamically at the same time, after the present invention is applied, the voltage of the dc side is well maintained at the rated value of 320kV, and when no control is applied, the voltage deviation of the dc side changes greatly.

Claims (3)

1. A direct current side voltage indirect control method applied to a multi-terminal flexible power transmission system is characterized by comprising the following steps:
1) replacing a direct-current side voltage controller in the rectifying side MMC system by a total capacitance voltage controller;
2) solving the amplitude and the phase of a modulation signal, output current and circulation current in the rectification side MMC system under the dq rotation coordinate system;
3) calculating a voltage compensation signal in real time according to the amplitude and the phase of a modulation signal, an output current and a circulating current in the MMC system at the rectifying side
Figure FDA0003457385710000011
4) Compensating the voltage compensation signal obtained in the step 3)
Figure FDA0003457385710000012
Adding the voltage commands into the voltage commands of the upper and lower bridge arms to obtain final voltage commands of the upper and lower bridge arms, and then controlling the direct-current side voltage of the multi-terminal flexible power transmission system according to the final voltage commands of the upper and lower bridge arms;
in step 2), the modulation ratio M and the phase α of the modulation signal of the multi-terminal flexible power transmission system are respectively:
Figure FDA0003457385710000013
wherein the content of the first and second substances,
Figure FDA0003457385710000014
which represents the command voltage of the d-axis,
Figure FDA0003457385710000015
which represents the q-axis command voltage,
Figure FDA0003457385710000016
represents the rated voltage of the direct current side;
under dq rotation coordinate system, the amplitude I of the output current of the multi-terminal flexible power transmission systemoAnd phase
Figure FDA0003457385710000017
Comprises the following steps:
Figure FDA0003457385710000018
wherein idRepresenting d-axis current, iqRepresents the q-axis current;
under dq rotating coordinate system, the amplitude I of the circulating current of the multi-terminal flexible power transmission system2And phase beta2Comprises the following steps:
Figure FDA0003457385710000021
wherein icir,dRepresenting d-axis circulation, icir,qRepresenting q-axis circulation.
2. The indirect direct-current-side voltage control method applied to the multi-terminal flexible power transmission system according to claim 1, wherein the specific operation of the step 3) is as follows:
calculating a voltage compensation signal in the controller according to the MMC steady state analysis model
Figure FDA0003457385710000022
Wherein the content of the first and second substances,
Figure FDA0003457385710000023
where M denotes the modulation ratio of the modulation signal, α denotes the phase of the modulation signal, IoWhich is indicative of the magnitude of the system output current,
Figure FDA0003457385710000024
indicating the phase of the system output current, I2Indicating the system circulating current amplitude, beta2Representing the circulating current phase of the system, C representing the capacitance value of the sub-module capacitor, UcThe direct current component of the sub-module capacitor voltage is represented, and omega represents the angular frequency of the system.
3. The method for indirectly controlling the direct-current side voltage applied to the multi-terminal flexible power transmission system according to claim 1, wherein the specific operation of the step 4) is as follows:
compensating the voltage signal
Figure FDA0003457385710000025
Switching function S acting on upper and lower bridge arms respectivelyU(t) and SL(t) finally, the control of the phase capacitor voltage is realized, wherein the switching functions S of the upper and lower bridge armsU(t) and SL(t) are respectively:
Figure FDA0003457385710000026
where M denotes the modulation ratio of the modulation signal, α denotes the phase of the modulation signal, t denotes time, and ω denotes the system angular frequency.
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