CN110752764B - Flexible direct current control method and device - Google Patents

Flexible direct current control method and device Download PDF

Info

Publication number
CN110752764B
CN110752764B CN201910988256.0A CN201910988256A CN110752764B CN 110752764 B CN110752764 B CN 110752764B CN 201910988256 A CN201910988256 A CN 201910988256A CN 110752764 B CN110752764 B CN 110752764B
Authority
CN
China
Prior art keywords
transistor
direct current
diode
bridge
bridge arm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201910988256.0A
Other languages
Chinese (zh)
Other versions
CN110752764A (en
Inventor
杨柳
黄伟煌
朱喆
周月宾
许树楷
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Research Institute of Southern Power Grid Co Ltd
Original Assignee
Research Institute of Southern Power Grid Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Research Institute of Southern Power Grid Co Ltd filed Critical Research Institute of Southern Power Grid Co Ltd
Priority to CN201910988256.0A priority Critical patent/CN110752764B/en
Publication of CN110752764A publication Critical patent/CN110752764A/en
Application granted granted Critical
Publication of CN110752764B publication Critical patent/CN110752764B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • 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
    • 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
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • 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
    • H02M7/53871—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 with automatic control of output voltage or current
    • 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 flexible direct current control method, which is suitable for a flexible direct current transmission system and comprises the following steps: when an overhead line in the flexible direct current transmission system has a direct current ground fault, acquiring direct current of the flexible direct current transmission system; inputting the direct current and a preset target value into a PI controller to generate a target voltage; adding the target voltages into bridge arm modulation wave reference voltages of the modular multilevel converter respectively; and generating a trigger signal of each power module in the modular multilevel converter according to the reference voltage of the bridge arm modulation wave so as to control the direct-current voltage output of the modular multilevel converter. The invention also discloses a flexible direct current control device. By adopting the embodiment of the invention, the direct current system can be effectively prevented from being locked and stopped after the direct current fault occurs to the overhead line in the flexible direct current transmission system, and the power transmission capability can be quickly recovered.

Description

Flexible direct current control method and device
Technical Field
The invention relates to a flexible direct current control technology, in particular to a flexible direct current control method and device.
Background
The Modular Multilevel Converter (MMC) adopts a submodule cascading mode to construct the converter valve, so that direct series connection of a large number of devices is avoided, and the requirement on device consistency is lowered. Compared with the traditional two-level and three-level converter, the MMC has the advantages of low manufacturing difficulty, low loss, low step voltage, high waveform quality, strong fault processing capability and the like, and has been widely applied to flexible direct current power transmission and static synchronous compensators.
In the technology of the flexible direct current control of the overhead line, if the MMC completely adopts a half-bridge type power module, after the overhead line fails, a voltage source converter needs to be locked, a direct current system is shut down, and after the failure is cleared, the system is restarted, so that the stable operation of the system is influenced. The MMC completely adopts a full-bridge type power module, and after the overhead line breaks down, the full-bridge structure can be controlled to output-1 level, so that the direct-current fault removal is realized. The direct current fault clearing can also be realized by changing the topological structure of the MMC power module, and the method is different from the method for controlling the direct current in the patent to a certain extent.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for controlling a flexible direct current, which can effectively ensure that a direct current system does not have locking and outage after a direct current fault occurs in an overhead line in a flexible direct current transmission system, and can quickly recover the power transmission capacity.
In order to achieve the above object, an embodiment of the present invention provides a flexible dc current control method, which is applied to a flexible dc power transmission system, and the method includes:
when an overhead line in the flexible direct current transmission system has a direct current ground fault, acquiring direct current of the flexible direct current transmission system;
inputting the direct current and a preset target value into a PI controller to generate a target voltage;
adding the target voltages into bridge arm modulation wave reference voltages of the modular multilevel converter respectively;
and generating a trigger signal of each power module in the modular multilevel converter according to the reference voltage of the bridge arm modulation wave so as to control the direct-current voltage output of the modular multilevel converter.
As an improvement of the above scheme, the bridge arm modulated wave reference voltage comprises an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcA DC voltage rating of the flexible DC power transmission system; u shapeacThe effective value of the outlet voltage of the alternating current side of the modular multilevel converter is obtained; u shapecirVoltage drop generated on a bridge arm for double frequency circulation of a bridge arm of the modular multilevel converter; Δ U is the target voltage.
As an improvement of the above scheme, each bridge arm in the modular multilevel converter comprises a plurality of half-bridge type power modules and full-bridge type power modules.
As an improvement of the above, the half-bridge type power module and the full-bridge type power module are connected in series.
As a modification of the above, the target value is 0
As an improvement of the above, the method further comprises:
when an overhead line in the flexible direct current transmission system has a direct current ground fault, the outer ring active controller outputs current to 0;
and after the fault is recovered, switching to active control before the fault again.
As an improvement of the above, the half-bridge type power module includes: the half-bridge circuit comprises a half-bridge input end, a half-bridge output end, a first transistor, a second transistor, a first capacitor, a first diode and a second diode; wherein the content of the first and second substances,
the half-bridge input end is respectively connected with the source electrode of the first transistor and the drain electrode of the second transistor, and the half-bridge output end is connected with the source electrode of the second transistor; the anode of the first diode is connected with the source electrode of the first transistor, and the cathode of the first diode is connected with the drain electrode of the first transistor; the anode of the second diode is connected with the source electrode of the second transistor, and the cathode of the second diode is connected with the drain electrode of the second transistor; the first end of the first capacitor is connected with the drain electrode of the first transistor, and the second end of the first capacitor is connected with the source electrode of the second transistor.
As an improvement of the above, the full-bridge type power module includes: the full-bridge circuit comprises a full-bridge input end, a full-bridge output end, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a second capacitor, a third diode, a fourth diode, a fifth diode and a sixth diode; wherein the content of the first and second substances,
the full-bridge input end is respectively connected with the source electrode of the third transistor and the drain electrode of the fourth transistor, and the full-bridge output end is respectively connected with the source electrode of the fifth transistor and the drain electrode of the sixth transistor; the anode of the third diode is connected with the source electrode of the third transistor, and the cathode of the third diode is connected with the drain electrode of the third transistor; the anode of the fourth diode is connected with the source electrode of the fourth transistor, and the cathode of the fourth diode is connected with the drain electrode of the fourth transistor; the anode of the fifth diode is connected with the source electrode of the fifth transistor, and the cathode of the fifth diode is connected with the drain electrode of the fifth transistor; the anode of the sixth diode is connected with the source electrode of the sixth transistor, and the cathode of the sixth diode is connected with the drain electrode of the sixth transistor; a first end of the second capacitor is connected to the drain of the third transistor and the drain of the fifth transistor respectively, and a second end of the second capacitor is connected to the source of the fourth transistor and the source of the sixth transistor respectively.
The embodiment of the invention also provides a flexible direct current control device, which is suitable for a flexible direct current power transmission system, and the device comprises:
the direct current acquisition module is used for acquiring direct current of the flexible direct current transmission system when an overhead line in the flexible direct current transmission system has a direct current ground fault;
the target voltage generation module is used for inputting the direct current and a preset target value into the PI controller to generate a target voltage;
the reference voltage calculation module is used for respectively adding the target voltage into bridge arm modulation wave reference voltages of the modular multilevel converter;
and the trigger signal generation module is used for generating a trigger signal of each power module in the modular multilevel converter according to the bridge arm modulation wave reference voltage so as to control the direct-current voltage output of the modular multilevel converter.
As an improvement of the above scheme, the bridge arm modulated wave reference voltage comprises an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcA DC voltage rating of the flexible DC power transmission system; u shapeacThe effective value of the outlet voltage of the alternating current side of the modular multilevel converter is obtained; u shapecirVoltage drop generated on a bridge arm for double frequency circulation of a bridge arm of the modular multilevel converter; Δ U is the target voltage.
Compared with the prior art, the flexible direct current control method and the flexible direct current control device disclosed by the embodiment of the invention can reduce the direct current fault current to zero within hundreds of milliseconds after the fault occurs, so that the purpose of clearing the direct current fault is achieved; the converter valve does not need to be locked in the whole process, the direct current system can be restarted immediately after the direct current is reduced to zero, and the direct current voltage and the power of the fault pole can be quickly recovered to the rated value; the non-fault pole can continuously keep rated stable operation in the whole process of fault occurrence and fault pole recovery, and the operation state is basically not influenced.
Drawings
Fig. 1 is a block diagram of a modular multilevel voltage source converter according to an embodiment of the present invention;
fig. 2 is a circuit diagram of an a-phase bridge arm in the modular multilevel voltage source converter according to the embodiment of the present invention;
fig. 3 is a circuit diagram of a half-bridge type power module structure provided by an embodiment of the present invention;
fig. 4 is a circuit diagram of a full-bridge power module structure according to an embodiment of the present invention;
FIG. 5 is a flow chart of a flexible DC current control method according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of DC current control provided by an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a flexible dc current control device according to an embodiment of the present invention.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments. 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.
It should be noted that the flexible dc current control method according to the embodiment of the present invention is applicable to a flexible dc power transmission system. In normal operation, the flexible direct current converter station level control mode generally adopts direct current control, and comprises an inner ring current control part and an outer ring voltage control part. The outer loop control of the transmitting/receiving end converter station generally adopts an active type control and a reactive type control.
The flexible direct current converter valve in the embodiment of the invention needs to adopt a modular multilevel converter structure (MMC), a power module on each bridge arm consists of P full-bridge power modules and Q half-bridge power modules, P + Q is N, and P: Q is more than or equal to 1: 1. Referring to fig. 1, fig. 1 is a block diagram of a modular multilevel voltage source converter according to an embodiment of the present invention, where each bridge arm of the modular multilevel voltage source converter includes a number of half-bridge power modules and a full-bridge power module.
Further, referring to fig. 2, fig. 2 is a circuit diagram of an a-phase bridge arm in the modular multilevel voltage source converter according to the embodiment of the present invention, where the half-bridge power module and the full-bridge power module are connected in series. It should be noted that fig. 2 only shows the structure of the a-phase bridge arm, and the structure of other phases of the modular multilevel voltage source converter may refer to the structure of fig. 2 or add/subtract a plurality of half-bridge type power modules/full-bridge type power modules on the basis of fig. 2, which is not limited in the present invention.
Referring to fig. 3, fig. 3 is a circuit diagram of a half-bridge type power module structure according to an embodiment of the present invention; the half-bridge type power module includes: a half-bridge input end IN1, a half-bridge output end OUT1, a first transistor IGBT1, a second transistor IGBT2, a first capacitor E1, a first diode VD1 and a second diode VD 2; wherein the content of the first and second substances,
the half-bridge input end IN1 is respectively connected with the source of the first transistor IGBT1 and the drain of the second transistor IGBT2, and the half-bridge output end OUT1 is connected with the source of the second transistor IGBT 2; the positive electrode of the VD1 of the first diode is connected with the source electrode of the first transistor IGBT1, and the negative electrode of the VD1 of the first diode is connected with the drain electrode of the first transistor IGBT 1; the anode of the second diode VD2 is connected to the source of the second transistor IGBT2, and the cathode of the second diode VD2 is connected to the drain of the second transistor IGBT 2; a first end of the first capacitor E1 is connected to the drain of the first transistor IGBT1, and a second end of the first capacitor E1 is connected to the source of the second transistor IGBT 2.
Referring to fig. 4, fig. 4 is a circuit diagram of a full-bridge power module structure according to an embodiment of the present invention; the full bridge type power module includes: a full-bridge input terminal IN2, a full-bridge output terminal OUT2, a third transistor IGBT3, a fourth transistor IGBT4, a fifth transistor IGBT5, a sixth transistor IGBT6, a second capacitor E2, a third diode VD3, a fourth diode VD4, a fifth diode VD5, and a sixth diode VD 6; wherein the content of the first and second substances,
the full-bridge input end IN2 is respectively connected with the source of the third transistor IGBT3 and the drain of the fourth transistor IGBT4, and the full-bridge output end OUT2 is respectively connected with the source of the fifth transistor IGBT5 and the drain of the sixth transistor IGBT 6; the anode of the third diode VD3 is connected to the source of the third transistor IGBT3, and the cathode of the third diode VD3 is connected to the drain of the third transistor IGBT 3; the anode of the fourth diode VD4 is connected to the source of the fourth transistor IGBT4, and the cathode of the fourth diode VD4 is connected to the drain of the fourth transistor IGBT 4; the anode of the fifth diode VD5 is connected to the source of the fifth transistor IGBT5, and the cathode of the fifth diode VD5 is connected to the drain of the fifth transistor IGBT 5; the anode of the sixth diode VD6 is connected to the source of the sixth transistor IGBT6, and the cathode of the sixth diode VD6 is connected to the drain of the sixth transistor IGBT 6; a first end of the second capacitor E2 is connected to the drain of the third transistor IGBT3 and the drain of the fifth transistor IGBT5, respectively, and a second end of the second capacitor E2 is connected to the source of the fourth transistor IGBT4 and the source of the sixth transistor IGBT6, respectively.
Referring to fig. 5, fig. 5 is a flowchart of a flexible dc current control method according to an embodiment of the present invention; the flexible direct current control method comprises the following steps:
s1, when the overhead line in the flexible direct current transmission system has a direct current ground fault, collecting the direct current of the flexible direct current transmission system;
s2, inputting the direct current and a preset target value into a PI controller to generate a target voltage;
s3, adding the target voltages into bridge arm modulation wave reference voltages of the modular multilevel converter respectively;
and S4, generating a trigger signal of each power module in the modular multilevel converter according to the bridge arm modulation wave reference voltage so as to control the direct-current voltage output of the modular multilevel converter.
Specifically, in step S1, when a dc ground fault occurs in an overhead line in the flexible dc power transmission system, a dc current of the flexible dc power transmission system is collected. For example, the direct current may be collected by a current collecting device, such as a current sensor.
Specifically, in step S2, the dc current and a preset target value are input to the PI controller, and a target voltage is generated. As shown in fig. 6, the target value is 0, and the target value is used to control the dc current to be equal to the target value, i.e. to control the dc current to decrease to 0; the target value and the direct current IdcInput into PI controller to output target voltage Δ U, Δ Umin≤ΔU≤ΔUmax. The direct current fault current is reduced to zero within hundreds of milliseconds after the fault occurs, so that the purpose of clearing the direct current fault is achieved; the converter valve does not need to be locked in the whole process, the direct current system can be restarted immediately after the direct current is reduced to zero, and the direct current voltage and the power of the fault pole can be quickly recovered to the rated value.
Specifically, in step S3, the bridge arm modulated wave reference voltages include an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcThe rated value of the direct-current voltage of the flexible direct-current power transmission system is a fixed value; u shapeacThe effective value of the outlet voltage at the alternating current side of the modular multilevel converter is a measured value and can be obtained by real-time measurement; u shapecirFor the voltage drop generated on the bridge arm by the double-frequency circulating current of the bridge arm of the modular multilevel converter, a circulating current restraining function is required to be configured for a general MMC, and the function is a conventional function; Δ U is the target voltage.
Specifically, in step S4, after generating the reference voltage of the modulated waves of the upper and lower bridge arms of the MMC, the reference voltage is used as an input value of the modulation technique (currently, more modulation techniques are adopted in the engineering as the nearest level approximation method), and a trigger on/off signal of each power module in the upper and lower bridge arms of the MMC is generated through a modulation link, so as to output the dc voltage of the MMC current converter.
Further, the output current i of the outer-loop active controller is needed during the fault periodsdrefWhen the current reaches 0, the control process of the steps S1 to S4 in the embodiment of the invention is switched to be adopted, and the control process is switched to the active control before the fault again after the fault is recovered (after the direct current is reduced to 0).
Compared with the prior art, the flexible direct current control method disclosed by the embodiment of the invention can reduce the direct current fault current to zero within hundreds of milliseconds after the fault occurs, so as to achieve the purpose of clearing the direct current fault; the converter valve does not need to be locked in the whole process, the direct current system can be restarted immediately after the direct current is reduced to zero, and the direct current voltage and the power of the fault pole can be quickly recovered to the rated value; the non-fault pole can continuously keep rated stable operation in the whole process of fault occurrence and fault pole recovery, and the operation state is basically not influenced.
Referring to fig. 7, fig. 7 is a schematic structural diagram of a flexible dc current control device according to an embodiment of the present invention. The flexible direct current control device comprises:
the direct current acquisition module 11 is configured to acquire a direct current of the flexible direct current power transmission system when a direct current ground fault occurs in an overhead line in the flexible direct current power transmission system;
a target voltage generation module 12, configured to input the direct current and a preset target value into a PI controller, and generate a target voltage; preferably, the target value is 0;
the reference voltage calculation module 13 is configured to add the target voltages to bridge arm modulation wave reference voltages of the modular multilevel converter respectively;
and the trigger signal generating module 14 is configured to generate a trigger signal of each power module in the modular multilevel converter according to the bridge arm modulation wave reference voltage, so as to control a dc voltage output of the modular multilevel converter.
Preferably, the bridge arm modulated wave reference voltage comprises an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcA DC voltage rating of the flexible DC power transmission system; u shapeacThe effective value of the outlet voltage of the alternating current side of the modular multilevel converter is obtained; u shapecirVoltage drop generated on a bridge arm for double frequency circulation of a bridge arm of the modular multilevel converter; Δ U is the target voltage.
Preferably, each bridge arm in the modular multilevel converter comprises a plurality of half-bridge type power modules and full-bridge type power modules. The half-bridge power module and the full-bridge power module are connected in series.
The half-bridge type power module includes: the half-bridge circuit comprises a half-bridge input end, a half-bridge output end, a first transistor, a second transistor, a first capacitor, a first diode and a second diode; wherein the content of the first and second substances,
the half-bridge input end is respectively connected with the source electrode of the first transistor and the drain electrode of the second transistor, and the half-bridge output end is connected with the source electrode of the second transistor; the anode of the first diode is connected with the source electrode of the first transistor, and the cathode of the first diode is connected with the drain electrode of the first transistor; the anode of the second diode is connected with the source electrode of the second transistor, and the cathode of the second diode is connected with the drain electrode of the second transistor; the first end of the first capacitor is connected with the drain electrode of the first transistor, and the second end of the first capacitor is connected with the source electrode of the second transistor.
The full bridge type power module includes: the full-bridge circuit comprises a full-bridge input end, a full-bridge output end, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a second capacitor, a third diode, a fourth diode, a fifth diode and a sixth diode; wherein the content of the first and second substances,
the full-bridge input end is respectively connected with the source electrode of the third transistor and the drain electrode of the fourth transistor, and the full-bridge output end is respectively connected with the source electrode of the fifth transistor and the drain electrode of the sixth transistor; the anode of the third diode is connected with the source electrode of the third transistor, and the cathode of the third diode is connected with the drain electrode of the third transistor; the anode of the fourth diode is connected with the source electrode of the fourth transistor, and the cathode of the fourth diode is connected with the drain electrode of the fourth transistor; the anode of the fifth diode is connected with the source electrode of the fifth transistor, and the cathode of the fifth diode is connected with the drain electrode of the fifth transistor; the anode of the sixth diode is connected with the source electrode of the sixth transistor, and the cathode of the sixth diode is connected with the drain electrode of the sixth transistor; a first end of the second capacitor is connected to the drain of the third transistor and the drain of the fifth transistor respectively, and a second end of the second capacitor is connected to the source of the fourth transistor and the source of the sixth transistor respectively.
Compared with the prior art, the flexible direct current control device disclosed by the embodiment of the invention can reduce the direct current fault current to zero within hundreds of milliseconds after the fault occurs, so as to achieve the purpose of clearing the direct current fault; the converter valve does not need to be locked in the whole process, the direct current system can be restarted immediately after the direct current is reduced to zero, and the direct current voltage and the power of the fault pole can be quickly recovered to the rated value; the non-fault pole can continuously keep rated stable operation in the whole process of fault occurrence and fault pole recovery, and the operation state is basically not influenced.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (8)

1. A flexible direct current control method is applicable to a flexible direct current transmission system, and comprises the following steps:
when an overhead line in the flexible direct current transmission system has a direct current ground fault, acquiring direct current of the flexible direct current transmission system;
inputting the direct current and a preset target value into a PI controller to generate a target voltage;
adding the target voltages into bridge arm modulation wave reference voltages of the modular multilevel converter respectively; the bridge arm modulated wave reference voltage comprises an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcA DC voltage rating of the flexible DC power transmission system; u shapeacThe effective value of the outlet voltage of the alternating current side of the modular multilevel converter is obtained; u shapecirVoltage drop generated on a bridge arm for double frequency circulation of a bridge arm of the modular multilevel converter; Δ U is the target voltage;
and generating a trigger signal of each power module in the modular multilevel converter according to the reference voltage of the bridge arm modulation wave so as to control the direct-current voltage output of the modular multilevel converter.
2. The flexible direct current control method of claim 1, wherein each leg of the modular multilevel converter comprises a number of half-bridge type power modules and full-bridge type power modules.
3. The flexible direct current control method of claim 2, wherein the half-bridge type power module and the full-bridge type power module are connected in series.
4. The flexible direct current control method of claim 1, wherein the target value is 0.
5. The flexible direct current control method of claim 4, further comprising:
when an overhead line in the flexible direct current transmission system has a direct current ground fault, the outer ring active controller outputs current to 0;
and after the fault is recovered, switching to active control before the fault again.
6. The flexible direct current control method of claim 2, wherein the half-bridge type power module comprises: the half-bridge circuit comprises a half-bridge input end, a half-bridge output end, a first transistor, a second transistor, a first capacitor, a first diode and a second diode; wherein the content of the first and second substances,
the half-bridge input end is respectively connected with the source electrode of the first transistor and the drain electrode of the second transistor, and the half-bridge output end is connected with the source electrode of the second transistor; the anode of the first diode is connected with the source electrode of the first transistor, and the cathode of the first diode is connected with the drain electrode of the first transistor; the anode of the second diode is connected with the source electrode of the second transistor, and the cathode of the second diode is connected with the drain electrode of the second transistor; the first end of the first capacitor is connected with the drain electrode of the first transistor, and the second end of the first capacitor is connected with the source electrode of the second transistor.
7. The flexible direct current control method of claim 2, wherein the full-bridge power module comprises: the full-bridge circuit comprises a full-bridge input end, a full-bridge output end, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a second capacitor, a third diode, a fourth diode, a fifth diode and a sixth diode; wherein the content of the first and second substances,
the full-bridge input end is respectively connected with the source electrode of the third transistor and the drain electrode of the fourth transistor, and the full-bridge output end is respectively connected with the source electrode of the fifth transistor and the drain electrode of the sixth transistor; the anode of the third diode is connected with the source electrode of the third transistor, and the cathode of the third diode is connected with the drain electrode of the third transistor; the anode of the fourth diode is connected with the source electrode of the fourth transistor, and the cathode of the fourth diode is connected with the drain electrode of the fourth transistor; the anode of the fifth diode is connected with the source electrode of the fifth transistor, and the cathode of the fifth diode is connected with the drain electrode of the fifth transistor; the anode of the sixth diode is connected with the source electrode of the sixth transistor, and the cathode of the sixth diode is connected with the drain electrode of the sixth transistor; a first end of the second capacitor is connected to the drain of the third transistor and the drain of the fifth transistor respectively, and a second end of the second capacitor is connected to the source of the fourth transistor and the source of the sixth transistor respectively.
8. A flexible dc current control apparatus adapted for use in a flexible dc power transmission system, the apparatus comprising:
the direct current acquisition module is used for acquiring direct current of the flexible direct current transmission system when an overhead line in the flexible direct current transmission system has a direct current ground fault;
the target voltage generation module is used for inputting the direct current and a preset target value into the PI controller to generate a target voltage;
the reference voltage calculation module is used for respectively adding the target voltage into bridge arm modulation wave reference voltages of the modular multilevel converter; the bridge arm modulated wave reference voltage comprises an upper bridge arm modulated wave reference voltage and a lower bridge arm modulated wave reference voltage; then, the adding the target voltages to the bridge arm modulation wave reference voltages of the modular multilevel converter respectively satisfies the following formulas:
Urefp＝1/2Udc-Uac-Ucir+ Δ U formula (1);
Urefn＝1/2Udc+Uac-Ucir+ Δ U equation (2);
wherein, UrefpModulating a wave reference voltage for the upper bridge arm; u shaperefnModulating a wave reference voltage for the lower bridge arm; u shapedcA DC voltage rating of the flexible DC power transmission system; u shapeacThe effective value of the outlet voltage of the alternating current side of the modular multilevel converter is obtained; u shapecirVoltage drop generated on a bridge arm for double frequency circulation of a bridge arm of the modular multilevel converter; Δ U is the target voltage;
and the trigger signal generation module is used for generating a trigger signal of each power module in the modular multilevel converter according to the bridge arm modulation wave reference voltage so as to control the direct-current voltage output of the modular multilevel converter.
CN201910988256.0A 2019-10-17 2019-10-17 Flexible direct current control method and device Active CN110752764B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910988256.0A CN110752764B (en) 2019-10-17 2019-10-17 Flexible direct current control method and device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910988256.0A CN110752764B (en) 2019-10-17 2019-10-17 Flexible direct current control method and device

Publications (2)

Publication Number Publication Date
CN110752764A CN110752764A (en) 2020-02-04
CN110752764B true CN110752764B (en) 2021-02-09

Family

ID=69278790

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910988256.0A Active CN110752764B (en) 2019-10-17 2019-10-17 Flexible direct current control method and device

Country Status (1)

Country Link
CN (1) CN110752764B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113890395A (en) * 2021-09-03 2022-01-04 广东电网有限责任公司广州供电局 Flexible direct current converter, no-load pressurization test method and storage medium

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105048488A (en) * 2015-09-01 2015-11-11 华中科技大学 Flexible DC network DC short-circuit fault ride through method
CN108539796A (en) * 2018-05-31 2018-09-14 华中科技大学 A kind of fault traversing and energy dissipation control method of the bipolar soft straight power grid of wind-powered electricity generation

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104600997B (en) * 2015-02-04 2017-02-22 国家电网公司 Self coupled modular multilevel high-voltage DC-DC transformer and control method thereof
CN106655237B (en) * 2016-12-31 2019-05-14 华中科技大学 The fault ride-through method of multiterminal flexible high pressure DC transmission system DC monopole ground connection
CN107404245B (en) * 2017-07-14 2019-06-28 中国科学院电工研究所 Mixed type module multilevel converter submodule capacitor voltage fluctuates suppressing method
CN107994613B (en) * 2017-12-22 2019-08-30 华中科技大学 A kind of the alternating current-direct current fault traversing and energy dissipation method of the soft direct join net of wind-powered electricity generation
CN208738855U (en) * 2018-05-31 2019-04-12 华中科技大学 A kind of bipolar soft straight network system of wind-powered electricity generation
CN109245582A (en) * 2018-10-24 2019-01-18 南方电网科学研究院有限责任公司 The direct-current short circuit fault current sweep-out method of mixing module multilevel converter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105048488A (en) * 2015-09-01 2015-11-11 华中科技大学 Flexible DC network DC short-circuit fault ride through method
CN108539796A (en) * 2018-05-31 2018-09-14 华中科技大学 A kind of fault traversing and energy dissipation control method of the bipolar soft straight power grid of wind-powered electricity generation

Also Published As

Publication number Publication date
CN110752764A (en) 2020-02-04

Similar Documents

Publication Publication Date Title
Jacobson et al. VSC-HVDC transmission with cascaded two-level converters
CN108880311B (en) Clamping modulation method and device of multi-level inverter and inverter
CN106849148B (en) Alternating current fault ride-through control method for rectifying station of hybrid direct current transmission system
US20160336751A1 (en) Tripolar vsc-hvdc transmission system and method
CN105656071A (en) Flexible direct-current transmission low-voltage ride-through control method suitable for occasions without communication between double ends
CN112653171B (en) Hybrid converter topology suitable for offshore wind power transmission and control strategy thereof
CN105429165B (en) A kind of multiterminal Hybrid HVDC system topological and control method to the power supply of more drop point passive networks
WO2021218227A1 (en) Modular capacitor commutated converter and method
CN110048626A (en) Inverter ac combined floodgate common mode dash current suppressing method and its application apparatus
WO2014004575A1 (en) Circuits and methods for photovoltaic inverters
CN104104101A (en) Quick tidal current reversal control method of hybrid direct current transmission
CN106911260A (en) A kind of control method of multi-electrical level inverter, device and inverter
CN110752764B (en) Flexible direct current control method and device
CN101860249B (en) Three-level inverter and zero-crossing switching logic control method thereof
CN112271746A (en) Electrolytic capacitor-free MMC (modular multilevel converter) topological structure and control strategy for high-frequency chain interconnection
CN111478353A (en) Control method and device for flexible direct current transmission system
CN116760303B (en) High-voltage direct-current transformer and fault redundancy control method thereof
CN113285626A (en) Modularized multi-level converter loss optimization control method under fault-tolerant control
CN110323774B (en) Direct-current line fault restarting method, VSC control method and device
CN110224622B (en) Sub-module capacitor voltage fluctuation suppression method for full-bridge modular multilevel converter
CN116454958B (en) Inverter grid-connection and presynchronization control method, inverter system and photovoltaic power supply system
CN109039126B (en) Control method for reducing loss of full-bridge MMC sub-module
CN108599228B (en) Flexible direct current transmission converter and bipolar flexible direct current transmission system
CN114337335B (en) Hybrid modular multilevel converter, control method and control device
CN114784845A (en) M3C low-frequency converter and fault ride-through method and system thereof

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant