CN116191914A - Flexible direct current converter valve and control method thereof - Google Patents
Flexible direct current converter valve and control method thereof Download PDFInfo
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- CN116191914A CN116191914A CN202211738197.XA CN202211738197A CN116191914A CN 116191914 A CN116191914 A CN 116191914A CN 202211738197 A CN202211738197 A CN 202211738197A CN 116191914 A CN116191914 A CN 116191914A
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- 239000004065 semiconductor Substances 0.000 claims description 5
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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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
- 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]
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Abstract
The invention discloses a flexible direct current converter valve and a control method thereof, wherein the flexible direct current converter valve comprises: a three-phase bridge structure; each phase of bridge structure comprises an upper bridge arm and a lower bridge arm; the upper bridge arm and the lower bridge arm are formed by connecting a plurality of sub-modules in series; the submodule includes: the switching device comprises a first switching device, a second switching device, a bypass switch, a voltage stabilizing module and a storage capacitor; the first switching device and the second switching device are connected in series and then connected in parallel with the storage capacitor; the bypass switch is connected with the second switching device in parallel; the voltage stabilizing module is connected with the second switching device in parallel; the connection point between the first switching device and the second switching device is a first alternating current port of the sub-module; the connection point between the second switching device and the storage capacitor is a second alternating current port of the sub-module; the sub-module is connected in series with the upper bridge arm or the lower bridge arm through the first alternating current port and the second alternating current port in sequence. According to the technical scheme provided by the invention, the capacitor voltage of the failure submodule can be stabilized in a preset range, and the safe operation of the converter valve is ensured.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a flexible direct current converter valve and a control method thereof.
Background
As the demand for high-power electronics products progresses toward higher voltage and larger power capacity, two-level or three-level technologies have not met the increasing voltage and capacity demands, and more high-power electronics products adopt modular multi-level topologies, for example, flexible dc power transmission voltage source converters in the high-voltage high-power field mostly adopt modular multi-level topologies.
The flexible direct current converter valve of the modularized multi-level converter (Modular Multilevel Converter, MMC) is adopted to realize high voltage output through cascading of a plurality of sub-module units, and the sub-module alternating current ports are usually connected with bypass switches in parallel. Normally, when a flexible direct current converter valve submodule fails, a submodule bypass switch is switched on to bypass the submodule, so that stable operation of the modularized multi-level converter is ensured. However, when the bypass switch fails to switch on, the fault submodule cannot be bypassed, and current can continuously boost the fault submodule until overvoltage explosion occurs to the submodule, and even the MMC converter valve can be stopped.
Disclosure of Invention
The embodiment of the invention provides a flexible direct current converter valve and a control method thereof, which are used for stabilizing the capacitance voltage of a failure submodule in a preset range and ensuring the safe operation of the converter valve.
In a first aspect, an embodiment of the present invention provides a flexible dc converter valve, including: a three-phase bridge structure; each phase of bridge structure comprises an upper bridge arm and a lower bridge arm; the upper bridge arm and the lower bridge arm are formed by connecting a plurality of sub-modules in series; the first end of the upper bridge arm and the second end of the lower bridge arm of each phase of bridge structure are connected to the same alternating current power supply through inductance elements; the second end of the upper bridge arm of each phase of bridge structure is connected with the first pole of the direct current bus; the first end of the lower bridge arm of each phase of bridge structure is connected with the second pole of the direct current bus;
the submodule includes: the switching device comprises a first switching device, a second switching device, a bypass switch, a voltage stabilizing module and a storage capacitor; the first switching device and the second switching device are connected in series and then connected in parallel with the storage capacitor; the bypass switch is connected with the second switching device in parallel; the voltage stabilizing module is connected with the second switching device in parallel;
the connection point between the first switching device and the second switching device is a first alternating current port of the submodule; the connection point between the second switching device and the storage capacitor is a second alternating current port of the sub-module; the submodule is connected in series with the upper bridge arm or the lower bridge arm through the first alternating current port and the second alternating current port in sequence.
In a second aspect, an embodiment of the present invention further provides a control method of a flexible dc converter valve, which is applicable to the flexible dc converter valve provided in any embodiment of the present invention, where the control method of the flexible dc converter valve includes:
when the valve control device of the flexible direct current converter valve is in a put-in state, the first switching device is controlled to be turned on, and the second switching device is controlled to be turned off; when the submodule is in a cut-out state, the first switching device is controlled to be turned off, and the second switching device is controlled to be turned on;
when the submodule fails, the valve control device controls the bypass switch to be closed;
when the bypass switch fails, the voltage stabilizing module of the flexible direct current converter valve performs current discharging when a first voltage difference between the first alternating current port and the second alternating current port exceeds a set voltage so as to stabilize the first voltage difference at the set voltage.
In the invention, for the flexible direct current converter valve with a three-phase bridge structure, each phase bridge structure comprises an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of sub-modules connected in series, and each sub-module comprises a first switching device, a second switching device, a bypass switch, a storage capacitor and a voltage stabilizing module. The first switching device and the second switching device are connected in series and then connected with the storage capacitor in parallel, the bypass switch is connected with the second switching device in parallel, and the voltage stabilizing module is connected with the second switching device in parallel. If a sub-module of the flexible direct current converter valve fails, a bypass switch of the sub-module needs to be switched on, so that the sub-module bypasses, and the stable operation of the modularized multi-level converter is ensured. However, when the bypass switch fails to switch on, the voltage stabilizing module in the faulty sub-module can stabilize the first voltage difference at two ends of the faulty sub-module at a set voltage, so that the faulty sub-module is effectively prevented from continuously boosting, overvoltage explosion of the faulty sub-module is prevented, and stable operation of the flexible direct current converter valve is maintained.
Drawings
Fig. 1 is a schematic structural diagram of a flexible dc converter valve according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a sub-module of the flexible DC converter valve of FIG. 1;
FIG. 3 is a schematic diagram of a prior art sub-module;
fig. 4 is a schematic flow chart of a control method of a flexible dc converter according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
Flexible direct current transmission based on modularized multi-level converter (MMC) is the latest generation of high-voltage direct current transmission technology, and has many excellent characteristics and wide application prospects. Aiming at the problems that overvoltage explosion occurs on a submodule and even the current converter is shut down due to the refusal of a bypass switch, the method which is commonly adopted at present is that an overvoltage breakdown bypass thyristor is connected in parallel with an alternating current port of the submodule, the bridge arm current can cause the overvoltage breakdown to occur when the voltage of the alternating current port of the submodule rises to the breakdown voltage of the bypass thyristor, the thyristor forms a short-circuit through-current state after being passively broken down, and the flexible direct current converter valve is not shut down. However, the inventor finds that the existing method for connecting the bypass thyristors capable of breakdown by overvoltage in parallel with the alternating-current ports of the submodules has certain defects, namely when overvoltage breakdown explosion occurs when the voltage of the alternating-current ports of the submodules rises to the breakdown voltage of the bypass thyristors due to bridge arm current, the probability of short-circuit failure of the upper tubes of the submodules is relatively high, the capacitors of the submodules form a through discharge loop through the short-circuit upper tubes and the broken thyristors, the whole structure stability and waterway safety of the submodules can be damaged, the shell of the switching device can drop and splash, and the like, and great risks are generated for the stable operation of the MMC.
In order to solve the above-mentioned problems, an embodiment of the present invention provides a flexible dc converter valve, as shown in fig. 1, fig. 1 is a schematic structural diagram of the flexible dc converter valve provided in the embodiment of the present invention, and fig. 2 is a schematic structural diagram of a submodule of the flexible dc converter valve in fig. 1. The flexible direct current converter valve includes:
a three-phase bridge structure 1; each phase of bridge structure 11 comprises an upper bridge arm 111 and a lower bridge arm 112; the upper bridge arm 111 and the lower bridge arm 112 are each formed by connecting a plurality of sub-modules 113 in series; the first end of the upper leg 111 and the second end of the lower leg 112 of each phase bridge structure 11 are connected to the same ac power source (e.g., a-phase ac power source, B-phase ac power source, and C-phase ac power source) through an inductive element 114; the second end of the upper bridge arm 111 of each phase of bridge structure 11 is connected with the first pole P1 of the direct current bus; the first end of the lower bridge arm 112 of each phase of bridge structure 11 is connected with the second pole P2 of the direct current bus;
the sub-module 113 includes: a first switching device T1, a second switching device T2, a bypass switch K, a voltage stabilizing module 114, and a storage capacitor C; the first switching device T1 and the second switching device T2 are connected in series and then connected in parallel with the storage capacitor C; the bypass switch K is connected with the second switching device T2 in parallel; the voltage stabilizing module 114 is connected in parallel with the second switching device T2;
the connection point between the first switching device T1 and the second switching device T2 is the first ac port P3 of the submodule 113; the connection point between the second switching device T2 and the storage capacitor C is a second ac port P4 of the sub-module 113; the sub-module 113 is serially connected to the upper arm 111 or the lower arm 112 through the first ac port P3 and the second ac port P4.
In the embodiment of the invention, for the flexible direct current converter valve with a three-phase bridge structure, each phase bridge structure comprises an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of sub-modules connected in series, and each sub-module comprises a first switching device, a second switching device, a bypass switch, a storage capacitor and a voltage stabilizing module. The first switching device and the second switching device are connected in series and then connected with the storage capacitor in parallel, the bypass switch is connected with the second switching device in parallel, and the voltage stabilizing module is connected with the second switching device in parallel. If a sub-module of the flexible direct current converter valve fails, a bypass switch of the sub-module needs to be switched on, so that the sub-module bypasses, and the stable operation of the modularized multi-level converter is ensured. However, when the bypass switch fails to switch on, the voltage stabilizing module in the faulty sub-module can stabilize the first voltage difference at two ends of the faulty sub-module at a set voltage, so that the faulty sub-module is effectively prevented from continuously boosting, overvoltage explosion of the faulty sub-module is prevented, and stable operation of the flexible direct current converter valve is maintained.
The foregoing is the core idea of the present invention, and the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without making any inventive effort are intended to fall within the scope of the present invention.
Fig. 1 shows a general topology of a flexible dc converter valve 1, i.e. a modular multilevel converter, three-phase bridge structure 11; each bridge structure 11 comprises an upper leg 111 and a lower leg 112; the upper bridge arm 111 and the lower bridge arm 112 respectively comprise a plurality of cascaded sub-modules 113; the flexible direct current converter valve 1 comprises an alternating current side and a direct current side; the first end of the upper bridge arm 111 and the second end of the lower bridge arm 112 of the bridge structure 11 of the flexible direct current converter valve 1 are connected, and serve as an alternating current terminal (an alternating current terminal a, an alternating current terminal B or an alternating current terminal C) of an alternating current side to be connected with a corresponding alternating current power supply (an alternating current power supply a, an alternating current power supply B or an alternating current power supply C); the second ends of the upper bridge arms 111 of the bridge structures 11 of the flexible dc converter valve 1 intersect as a first terminal on the dc side and are electrically connected to the first pole P1 of the dc bus, and the first ends of the lower bridge arms 112 of the bridge structures 11 of the flexible dc converter valve 1 intersect as a second terminal on the dc side and are electrically connected to the second pole P2 of the dc bus. The flexible dc converter valve in this embodiment is used to convert the supply voltage between three-phase ac and dc.
As shown in fig. 2, the submodule 113 includes two switching devices (a first switching device T1 and a second switching device T2), an energy storage capacitor C, a bypass switch K, and a voltage stabilizing module 114 capable of stabilizing voltage, where the two switching devices are connected in series and then connected in parallel with the energy storage capacitor C, a connection point of the two switching devices is a positive pole P3 of the submodule 113, one end of the energy storage capacitor C is a negative pole P4 of the submodule 113, and the bypass switch K, the voltage stabilizing module 114 capable of stabilizing voltage, and the energy storage capacitor C are connected in parallel. The sub-modules 113 may be placed into each bridge structure 11 under the control of the controller or may be cut out of the bridge structures 11 under the control of the controller. Optionally, in this embodiment, the upper bridge arm 111 and the lower bridge arm 112 of each bridge structure 11 may include N sub-modules 113 with identical structures to be switched in a matched manner.
Optionally, the controller may be a valve control device, and specifically, the flexible dc converter valve may further include: a valve control device; the valve control device is used for controlling the first switching device T1 to be turned on and controlling the second switching device T2 to be turned off when the submodule 113 is put into a put-in state; the valve control device is further used for controlling the first switching device T1 to be turned off and controlling the second switching device T2 to be turned on when the submodule 113 is in the cut-out state.
With continued reference to fig. 2, the input states of all the submodules 113 in the bridge arm are controlled by the valve control device, when the submodules 113 are required to be input during normal operation, that is, when the submodules are connected in series into the bridge arm, the first switching device T1 is turned on, the second switching device T2 is turned off, and then the first voltage difference between the first ac port P3 and the second ac port P4 is the voltage difference between two ends of the energy storage capacitor C. When the current direction is from the first ac port P3 to the second ac port P4, the current passes through the freewheeling diode D1 of the first switching device T1 and the energy storage capacitor C to form a loop, which is a charging state of the energy storage capacitor C, and when the current direction is from the second ac port P4 to the first ac port P3, the current passes through the energy storage capacitor C and the first switching device T1 to form a loop, which is a discharging state of the energy storage capacitor C. When the sub-module is required to be cut out, namely, the sub-module is not connected into the bridge arm in series, the energy storage capacitor C is not charged and discharged. The first voltage difference between the first ac port P3 and the second ac port P4 is zero. And when the current direction is from the first ac port P3 to the second ac port P4, the current forms a loop through the second switching device T2, and when the current direction is from the second ac port P4 to the first ac port P3, the current forms a loop through the freewheeling diode D1 of the second switching device T2.
Alternatively, both the first switching device T1 and the second switching device T2 may be turn-off semiconductor switching devices. The voltage of the control end of the turn-off semiconductor switching device is controlled by the valve control device, so that the turn-on and turn-off of the turn-off semiconductor switching device is controlled, the control is convenient, and the switching device is rapid and flexible in response.
When the bridge arm neutron module fails and the bypass switch K fails to switch on, the voltage stabilizing module 114 in this embodiment can stabilize the first voltage difference between the first ac port P3 and the second ac port P4 at a certain voltage. Specifically, when the faulty sub-module 113 cannot be bypassed, when the current is directed from the first ac port P3 to the second ac port P4, the energy storage capacitor C continues to boost, and the voltage stabilizing module 114 can perform current leakage to stabilize the voltage of the energy storage capacitor C of the faulty sub-module 113 within a certain range, so as to ensure the stability of the whole structure of the sub-module and the safety of the waterway, avoid the direct explosion of the faulty sub-module, and effectively avoid the falling and splashing of the switch device housing.
In this embodiment, the submodule can be compared with the submodule in fig. 3, as shown in fig. 3, and fig. 3 is a schematic structural diagram of the submodule in the prior art. The flexible direct current converter valve is cascaded through a plurality of submodules, the existing submodule comprises a first switching device T1', a second switching device T2', an energy storage capacitor C ', a bypass switch K' and a breakdown bypass thyristor SCR, the two switching devices are connected in parallel with the energy storage capacitor C 'after being connected in series, the connection point of the two switching devices is the positive electrode of the submodule, one end of the energy storage capacitor C' is the negative electrode of the submodule, and the bypass switch K 'is connected in parallel with the breakdown bypass thyristor SCR and the second switching device T2'. When the flexible direct current converter valve submodule fails, the submodule bypass switch K' is switched on, so that the submodule bypasses, and the stable operation of the modularized multi-level converter is ensured. However, when the bypass switch K 'fails to switch on, the failed submodule cannot be bypassed, current can continuously boost the voltage of the failed submodule, in order to prevent the submodule from overvoltage explosion and even cause the problem of shutdown of the converter, in the prior art, a breakdown bypass thyristor SCR connected in parallel with the bypass switch K' is arranged in the submodule, bridge arm current can cause overvoltage breakdown when a first voltage difference between two ports of the submodule rises to the breakdown voltage of the bypass thyristor SCR, and a short-circuit through-current state is formed after the breakdown bypass thyristor SCR is passively broken down, so that the flexible direct-current converter valve is not shutdown. However, when the breakdown bypass thyristor SCR is subjected to overvoltage breakdown explosion, the probability of short circuit failure of the first switch device T1' of the sub-module is relatively high, and the energy storage capacitor C ' of the sub-module forms a through discharge loop through the first switch device T1' of the short circuit and the breakdown bypass thyristor SCR after breakdown, so that the whole structure of the sub-module is damaged, the waterway is safe, the shell of the IGBT device falls and splashes, and the like, and great risks are generated for the stable operation of the MMC. In this embodiment, the current breakdown bypass thyristors SCR connected in parallel to the ports of the submodules are replaced by the voltage stabilizing module 114 capable of stabilizing voltage, and when the failed submodule continuously boosts, the voltage stabilizing module 114 can stabilize the energy storage capacitor C of the failed submodule within a certain range, so that the flexible direct current converter valve can safely operate, and direct explosion of the failed submodule due to overvoltage can be effectively avoided.
With continued reference to fig. 2, the voltage regulation module 114 may optionally include: a zener diode D; the cathode of the zener diode D is connected with the first alternating current port P3; the positive electrode of the zener diode D is connected to the second ac port P4. The voltage stabilizing module 114 may be composed of a voltage stabilizing diode D with a voltage stabilizing function, or may be composed of an electronic circuit with a corresponding voltage stabilizing function. The voltage stabilizing module is mainly used for carrying out current discharge, stabilizing the voltage at two ends of the voltage stabilizing module 114 within a certain range and preventing overvoltage.
Alternatively, the valve control device may be further configured to control the bypass switch K to close when the submodule 113 fails. Optionally, the voltage stabilizing module may be configured to perform current leakage when the first voltage difference between the first ac port P3 and the second ac port P4 exceeds the set voltage when the bypass switch K fails, so as to stabilize the first voltage difference at the set voltage.
Alternatively, the valve control device may also be used to: after the first voltage difference is stabilized at the set voltage, if the current direction is from the first ac port P3 to the second ac port P4, setting the sub-module 113 to be in the on state, and setting the number of sub-modules 113 to be input to be reduced by one; if the current direction is from the second ac port P4 to the first ac port P3, the sub-module 113 is set to be in the cut-out state, and the number of sub-modules 113 to be put in is set to be unchanged.
When the sub-module 113 fails, the bypass switch K fails to switch on, the failed sub-module 113 cannot be bypassed, the bridge arm current is in the charging direction, the failed sub-module 113 is continuously boosted, and when the set voltage is reached, the voltage stabilizing device discharges, so that the capacitor voltage of the storage capacitor of the failed sub-module 113 is stabilized at the set voltage.
When the capacitance voltage of the storage capacitor of the faulty sub-module 113 is stabilized at the set voltage, and when the current direction is the charging direction, the storage capacitor of the sub-module 113 is passively connected in series in the bridge arm, setting the sub-module 113 in the valve control device to be in an input state, and setting the number of sub-modules 113 to be input in the valve control device to be changed from N to N-1; when the current direction is the discharging direction, the storage capacitor of the submodule 113 is passively cut off, and is not in series connection in the bridge arm, the submodule 113 is set to be in a cut-off state in the valve control device, and the number of the submodules to be put into the valve control device is set to be unchanged from N. In this way, the number of the sub-modules 113 to be put into the bridge arm reaches the same number as the sub-modules 113 in normal operation, so that the converter valve works normally until the next time of overhauling and shutdown of the converter valve.
According to the control process of the valve control device on the faulty sub-module, when the sub-module fails and the bypass switch fails to be switched on, the faulty sub-module cannot be bypassed, when the bridge arm current is in the charging direction, the faulty sub-module is continuously boosted, and when the bridge arm current exceeds the set voltage, the voltage stabilizing device discharges the current, so that the capacitance voltage of the storage capacitor of the faulty sub-module is stabilized at the set voltage.
The method overcomes the defects of the traditional method for connecting the bypass thyristors which can be broken down by overvoltage in parallel with the input and output ports of the submodule, namely, when the bridge arm current enables the voltage of the input and output ports of the submodule to rise to the breakdown voltage of the bypass thyristors, overvoltage breakdown explosion occurs, the probability of short-circuit failure of the first switching device of the submodule is relatively high, the storage capacitor of the submodule forms a through discharge loop through the short-circuit first switching device and the broken thyristors, and the whole structure stability, the waterway safety, the falling and splashing of the shell of the semiconductor device and the like of the submodule can be damaged.
Through the voltage stabilizing control method of the voltage stabilizing module, after a certain submodule fails and when the bypass switch fails, the number of the submodules which are required to be input by the bridge arm reaches the same number as that of the submodules in normal operation, so that the flexible direct current converter valve works normally until the next time of overhauling and shutdown of the converter valve, the safe operation of the converter valve is ensured, and the direct explosion of the overvoltage of the failed submodule is avoided.
Based on the same conception, the embodiment of the invention also provides a control method of the flexible direct current converter valve. Fig. 4 is a schematic flow chart of a control method of a flexible dc converter valve according to an embodiment of the present invention, as shown in fig. 4, the method of the embodiment includes the following steps:
step S110, when the valve control device of the flexible direct current converter valve is in a put-in state, the first switching device is controlled to be turned on, and the second switching device is controlled to be turned off; and when the sub-module is in a cut-out state, the first switching device is controlled to be turned off, and the second switching device is controlled to be turned on.
And step S120, when the submodule fails, the valve control device controls the bypass switch to be closed.
And step 130, when the bypass switch fails, the voltage stabilizing module of the flexible direct current converter valve performs current discharging when the first voltage difference between the first alternating current port and the second alternating current port exceeds the set voltage so as to stabilize the first voltage difference at the set voltage.
In the embodiment of the invention, for the flexible direct current converter valve with a three-phase bridge structure, each phase bridge structure comprises an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of sub-modules connected in series, and each sub-module comprises a first switching device, a second switching device, a bypass switch, a storage capacitor and a voltage stabilizing module. The first switching device and the second switching device are connected in series and then connected with the storage capacitor in parallel, the bypass switch is connected with the second switching device in parallel, and the voltage stabilizing module is connected with the second switching device in parallel. If a sub-module of the flexible direct current converter valve fails, a bypass switch of the sub-module needs to be switched on, so that the sub-module bypasses, and the stable operation of the modularized multi-level converter is ensured. However, when the bypass switch fails to switch on, the voltage stabilizing module in the faulty sub-module can stabilize the first voltage difference at two ends of the faulty sub-module at a set voltage, so that the faulty sub-module is effectively prevented from continuously boosting, overvoltage explosion of the faulty sub-module is prevented, and stable operation of the flexible direct current converter valve is maintained.
On the basis of the foregoing embodiment, optionally, the control method of the flexible dc converter valve further includes: after the first voltage difference is stabilized at the set voltage, if the current direction is from the first alternating current port to the second alternating current port, setting the submodule to be in an input state, and setting the number of the submodules to be input to be reduced by one; if the current direction is from the second alternating current port to the first alternating current port, setting the submodule to be in a cut-out state, and setting the number of the submodules to be put in to be unchanged.
The flexible direct current converter valve in the control method of the flexible direct current converter valve provided by the embodiment of the invention comprises the technical characteristics of the flexible direct current converter valve provided by any embodiment of the invention, and has the beneficial effects of ensuring that after a certain submodule fails and a bypass switch is refused, the number of the submodules which are required to be put into by a bridge arm reaches the same number as that when the submodule works normally, so that the flexible direct current converter valve works normally until the next time of overhauling and stopping the converter valve, ensuring the safe operation of the converter valve and avoiding the direct explosion caused by overvoltage of the failed submodule.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
Claims (9)
1. A flexible dc converter valve, comprising: a three-phase bridge structure; each phase of bridge structure comprises an upper bridge arm and a lower bridge arm; the upper bridge arm and the lower bridge arm are formed by connecting a plurality of sub-modules in series; the first end of the upper bridge arm and the second end of the lower bridge arm of each phase of bridge structure are connected to the same alternating current power supply through inductance elements; the second end of the upper bridge arm of each phase of bridge structure is connected with the first pole of the direct current bus; the first end of the lower bridge arm of each phase of bridge structure is connected with the second pole of the direct current bus;
the submodule includes: the switching device comprises a first switching device, a second switching device, a bypass switch, a voltage stabilizing module and a storage capacitor; the first switching device and the second switching device are connected in series and then connected in parallel with the storage capacitor; the bypass switch is connected with the second switching device in parallel; the voltage stabilizing module is connected with the second switching device in parallel;
the connection point between the first switching device and the second switching device is a first alternating current port of the submodule; the connection point between the second switching device and the storage capacitor is a second alternating current port of the sub-module; the submodule is connected in series with the upper bridge arm or the lower bridge arm through the first alternating current port and the second alternating current port in sequence.
2. The flexible dc converter valve of claim 1, wherein said voltage regulation module comprises: a zener diode;
the cathode of the voltage stabilizing diode is connected with the first alternating current port; the positive pole of the voltage stabilizing diode is connected with the second alternating current port.
3. The flexible dc converter valve of claim 1, further comprising: a valve control device;
the valve control device is used for controlling the first switching device to be conducted and controlling the second switching device to be turned off when the submodule is in a put-in state; the valve control device is also used for controlling the first switching device to be switched off and controlling the second switching device to be switched on when the submodule is in a cut-out state.
4. A flexible dc converter valve according to claim 3, wherein the valve control means is further adapted to control the bypass switch to close when the sub-module fails.
5. The flexible dc converter valve of claim 4, wherein the voltage regulator module is configured to perform current bleeding when a first voltage difference between the first ac port and the second ac port exceeds a set voltage to stabilize the first voltage difference at the set voltage when the bypass switch fails.
6. The flexible dc converter valve of claim 5, wherein said valve control means is further adapted to: after the first voltage difference is stabilized at the set voltage, if the current direction is from the first alternating current port to the second alternating current port, setting the submodule to be in an on state, and setting the number of the submodules to be input to be reduced by one; if the current direction is from the second alternating current port to the first alternating current port, setting the submodule to be in a cut-out state, and setting the number of the submodules to be put in to be unchanged.
7. The flexible dc converter valve of claim 1, wherein the first switching device and the second switching device are both turn-off semiconductor switching devices.
8. A control method of a flexible direct current converter valve, characterized in that it is applied to a flexible direct current converter valve according to any one of claims 1 to 7, and the control method of the flexible direct current converter valve comprises:
when the valve control device of the flexible direct current converter valve is in a put-in state, the first switching device is controlled to be turned on, and the second switching device is controlled to be turned off; when the submodule is in a cut-out state, the first switching device is controlled to be turned off, and the second switching device is controlled to be turned on;
when the submodule fails, the valve control device controls the bypass switch to be closed;
when the bypass switch fails, the voltage stabilizing module of the flexible direct current converter valve performs current discharging when a first voltage difference between the first alternating current port and the second alternating current port exceeds a set voltage so as to stabilize the first voltage difference at the set voltage.
9. The method of controlling a flexible dc converter valve according to claim 8, further comprising: after the first voltage difference is stabilized at the set voltage, if the current direction is from the first alternating current port to the second alternating current port, setting the submodule to be in an on state, and setting the number of the submodules to be input to be reduced by one; if the current direction is from the second alternating current port to the first alternating current port, setting the submodule to be in a cut-out state, and setting the number of the submodules to be put in to be unchanged.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211738197.XA CN116191914A (en) | 2022-12-30 | 2022-12-30 | Flexible direct current converter valve and control method thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211738197.XA CN116191914A (en) | 2022-12-30 | 2022-12-30 | Flexible direct current converter valve and control method thereof |
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| Publication Number | Publication Date |
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| CN116191914A true CN116191914A (en) | 2023-05-30 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202211738197.XA Pending CN116191914A (en) | 2022-12-30 | 2022-12-30 | Flexible direct current converter valve and control method thereof |
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| Country | Link |
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| CN (1) | CN116191914A (en) |
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2022
- 2022-12-30 CN CN202211738197.XA patent/CN116191914A/en active Pending
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