CN108471251B - starting method and device of half-bridge and full-bridge mixed modular multilevel converter - Google Patents
starting method and device of half-bridge and full-bridge mixed modular multilevel converter Download PDFInfo
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- CN108471251B CN108471251B CN201810395466.4A CN201810395466A CN108471251B CN 108471251 B CN108471251 B CN 108471251B CN 201810395466 A CN201810395466 A CN 201810395466A CN 108471251 B CN108471251 B CN 108471251B
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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
- H02M7/483—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
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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
- H02M7/493—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 the static converters being arranged for operation in parallel
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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]
Abstract
The invention relates to a starting method of a half-bridge and full-bridge mixed modular multilevel converter. The method comprises the following steps: controlling the plurality of half-bridge sub-modules and the plurality of full-bridge sub-modules to be locked so that all half-bridge sub-modules and all full-bridge sub-modules reach respective initial voltages; controlling the plurality of half-bridge sub-modules to keep locked, and reducing the total voltage increasing speed of all the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; and respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltages of all the half-bridge submodules and the voltages of all the full-bridge submodules to reach rated voltages. The invention also relates to a starting device of the half-bridge and full-bridge mixed modular multilevel converter. The method and the device can avoid larger impact current caused at the moment of unlocking the system, thereby improving the safety of the system.
Description
Technical Field
The invention relates to the technical field of power supply, in particular to a starting method and a starting device of a half-bridge and full-bridge mixed modular multilevel converter.
Background
The Modular Multilevel Converter (MMC for short) realizes high voltage output by cascading a plurality of Converter valve sub-module units. The MMC does not need direct cascade of switching devices, has low requirement on consistent triggering of the devices, and has the advantages of good expansibility, low switching frequency, low running loss, high output voltage waveform quality and the like.
However, when the ac power grid supplies power to the flexible dc power transmission network through the MMC, due to the low damping characteristic of the flexible dc power transmission network, when the MMC has a short-circuit fault, the current rise rate at the initial stage of the fault reaches the level of several kiloamperes per millisecond, and the ac circuit breaker has a breaking speed of only several tens of milliseconds, and these several tens of milliseconds can cause critical electrical stress to be borne by critical equipment such as the MMC in the dc power network, thereby reducing the safety of equipment operation in the power grid. Therefore, when the MMC has a short-circuit fault, the safety of the power grid system is not good.
disclosure of Invention
Therefore, it is necessary to provide a method and an apparatus for starting a half-bridge and full-bridge hybrid modular multilevel converter, aiming at the problem that the safety of a power grid system is not good when the MMC has a short-circuit fault at present.
a starting method of a half-bridge and full-bridge hybrid modular multilevel converter comprises a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules. The method comprises the following steps:
Controlling the plurality of half-bridge sub-modules and the plurality of full-bridge sub-modules to be locked so that all half-bridge sub-modules and all full-bridge sub-modules reach respective initial voltages;
controlling the plurality of half-bridge sub-modules to keep locked, and reducing the total voltage increasing speed of all the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; wherein the working state of the full-bridge submodule comprises one of blocking, half blocking or bypass;
respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all half-bridge submodules and the voltage of all full-bridge submodules to reach rated voltage; wherein the operating state of the half-bridge sub-module comprises bypass or latch-up.
In one embodiment, the modular multilevel converter is connected to an alternating current grid through a series charging resistor.
In one embodiment, the step of keeping all the half-bridge sub-modules locked and reducing the overall voltage increase speed of the full-bridge sub-modules by controlling the operating state of at least part of the full-bridge sub-modules comprises:
And when the current of the charging resistor is smaller than a preset current value, controlling the bypass of the charging resistor.
In one embodiment, the step of keeping all the half-bridge sub-modules locked and reducing the overall voltage increase speed of the full-bridge sub-modules by controlling the operating state of at least part of the full-bridge sub-modules comprises:
And when the voltage of the charging resistor is greater than a preset voltage value, controlling the bypass of the charging resistor.
in one embodiment, the step of keeping all the half-bridge sub-modules locked and reducing the total voltage increase speed of the full-bridge sub-modules by controlling the operation state of at least part of the full-bridge sub-modules comprises:
when the voltage of each full-bridge submodule reaches the working threshold value of the self-energy-taking power supply, controlling all the half-bridge submodules to keep locking;
A full-bridge sub-module bypass controlling the voltage to be not less than a first threshold voltage;
Half locking of the full-bridge submodule is achieved, wherein the control voltage is between a second threshold voltage and the first threshold voltage; wherein the second threshold voltage is less than the first threshold voltage;
and locking the full-bridge sub-modules with the control voltage smaller than the second threshold voltage.
in one embodiment, the step of keeping all the half-bridge sub-modules locked and reducing the overall voltage increase speed of the full-bridge sub-modules by controlling the operation state of at least part of the full-bridge sub-modules comprises the following steps:
and when the ratio of the average voltage of all half-bridge sub-modules to the average voltage of all full-bridge sub-modules is greater than a preset multiple, controlling all full-bridge sub-modules to be half-locked and controlling all half-bridge sub-modules to be locked.
In one embodiment, the preset multiple is in the range of 0.6 to 1.4.
In one embodiment, the step of separately controlling the operating states of the full-bridge sub-modules and the half-bridge sub-modules to make the total voltage of all the half-bridge sub-modules and all the full-bridge sub-modules reach the rated voltage includes:
And the full-bridge sub-module bypass with the control voltage not less than the third threshold voltage, and the half-bridge sub-module bypass with the control voltage not less than the third threshold voltage.
a starting device of a half-bridge and full-bridge mixed modular multilevel converter comprises a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules, and the modular multilevel converter is connected to an alternating current power grid through series charging resistors. The device comprises:
The uncontrolled starting module is used for controlling all half-bridge sub-modules and all full-bridge sub-modules to be locked so as to enable all half-bridge sub-modules and all full-bridge sub-modules to reach initial voltage;
The half-control starting module is used for controlling all half-bridge sub-modules to keep locked and reducing the total voltage increasing speed of the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; wherein the working state of the full-bridge submodule comprises one of blocking, half blocking or bypass;
The full-control starting module is used for respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all the half-bridge submodules to reach the rated voltage and enable the voltage of all the full-bridge submodules to reach the rated voltage; wherein the operating state of the half-bridge sub-module comprises bypass or latch-up.
In one embodiment, the half-controlled starting module is used for controlling all half-bridge sub-modules to keep locked when the voltage of each full-bridge sub-module reaches an operating threshold of a self-energy-obtaining power supply;
the half-control starting module is also used for controlling a full-bridge sub-module bypass with the voltage not less than a first threshold voltage;
the half-control starting module is also used for controlling half locking of the full-bridge submodule, the voltage of which is between a second threshold voltage and the first threshold voltage; wherein the second threshold voltage is less than the first threshold voltage;
The half-control starting module is also used for controlling the locking of the full-bridge submodule of which the voltage is smaller than the second threshold voltage.
according to the starting method and the starting device of the half-bridge and full-bridge mixed modular multilevel converter, firstly, all half-bridge sub-modules and all full-bridge sub-modules are controlled to be locked, namely, all half-bridge sub-modules and all full-bridge sub-modules are charged, so that all half-bridge sub-modules and all full-bridge sub-modules reach initial voltage. Secondly, all the half-bridge sub-modules are controlled to be locked, and the total voltage increase speed of the full-bridge sub-modules is reduced by controlling the working state of at least part of the full-bridge sub-modules. In this way, the average voltage of all half-bridge sub-modules gradually increases, the average voltage of all full-bridge sub-modules gradually increases, and the two gradually approach, and the voltages of all sub-modules are equalized at this time. And then, respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all the half-bridge submodules to reach the rated voltage and enable the voltage of all the full-bridge submodules to reach the rated voltage. In this way, during the starting process of the modular multilevel converter, the voltages of all the full-bridge sub-modules and all the half-bridge sub-modules are slowly increased, and the voltages of all the sub-modules are kept in a more balanced state. Therefore, the output voltage of the modular multilevel converter is slowly increased to the rated voltage, so that larger impact current can be avoided at the moment of unlocking the system, and the safety factor of the power grid system is improved.
Drawings
fig. 1 is a schematic diagram of a modular multilevel converter according to an embodiment;
FIG. 2 is a schematic diagram of a half bridge sub-module of an embodiment;
FIG. 3 is a schematic diagram of a half bridge sub-module bypass of an embodiment;
FIG. 4 is a schematic diagram of a full bridge sub-module of an embodiment;
FIG. 5 is a schematic diagram of a full bridge submodule half latch according to an embodiment;
FIG. 6 is a schematic diagram of a full bridge sub-module bypass of an embodiment;
Fig. 7 is a schematic diagram of a connection of the modular multilevel converter to an ac power grid according to an embodiment;
Fig. 8 is a flowchart illustrating a starting method of a half-bridge and full-bridge hybrid modular multilevel converter according to a first embodiment;
Fig. 9 is a flow chart illustrating a starting method of a half-bridge and full-bridge hybrid modular multilevel converter according to a second embodiment;
fig. 10 is a flow chart illustrating a starting method of a half-bridge and full-bridge hybrid modular multilevel converter according to a third embodiment;
Fig. 11 is a block diagram of a starting apparatus of a half-bridge and full-bridge hybrid modular multilevel converter according to an embodiment.
Detailed Description
in order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 1 is a schematic diagram of a modular multilevel converter according to an embodiment. As shown in fig. 1, the modular multilevel converter includes a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules. The half-bridge sub-module and the full-bridge sub-module are called sub-modules together. A modular multilevel converter (shortly referred to as converter) with a hybrid half-bridge and full-bridge comprises at least one phase cell. In this embodiment, the inverter includes three phase units, which are an a-phase unit, a B-phase unit, and a C-phase unit. Each phase unit includes an upper leg and a lower leg. The upper bridge arm and the lower bridge arm have the same structure. The upper bridge arm and the lower bridge arm respectively comprise at least one half-bridge submodule, at least one full-bridge submodule and a reactor which are mutually connected in series. In this embodiment, the upper bridge arm and the lower bridge arm each include a half-bridge submodule, a full-bridge submodule, and a reactor, which are connected in series. In this embodiment, the converter further comprises a control device (not shown).
The half-bridge and full-bridge sub-modules are described in detail below.
fig. 2 is a schematic diagram of a half-bridge sub-module of an embodiment. The half-bridge submodule comprises a capacitor and a first switch unit connected with the capacitor in parallel. In this embodiment, the first switching unit includes a first turn-off device and a second turn-off device. The negative electrode of the first turn-off device and the positive electrode of the second turn-off device are connected in series to form a first switch unit. The anode of the first turn-off device serves as the anode of the first switching unit, and the cathode of the second turn-off device serves as the cathode of the first switching unit. The connection point of the first and second turn-off devices is used as a first end point, and the cathode of the first switch unit is used as a second end point. The half-bridge sub-modules are connected to the corresponding circuits through the first terminal and the second terminal. The operating state of the half-bridge sub-module includes bypass or latch-up.
the operation state of the half-bridge submodule latch can refer to fig. 2. The half-bridge sub-module latching refers to that a first turn-off device of the half-bridge sub-module is turned off, and a second turn-off device of the half-bridge sub-module is turned off.
Fig. 3 is a schematic diagram of a half-bridge sub-module bypass of an embodiment. As shown in fig. 3, a half-bridge sub-module bypass refers to a first turn-off device of the half-bridge sub-module being turned off and a second turn-on device being turned on.
fig. 4 is a schematic diagram of a full bridge sub-module according to an embodiment. The full-bridge submodule comprises a capacitor, and a second switching unit and a third switching unit which are connected with the capacitor in parallel. The second switching unit includes a third turn-off device and a fourth turn-off device. The negative electrode of the third turn-off device is connected with the positive electrode of the fourth turn-off device in series. The positive pole of the third turn-off device serves as the positive pole of the second switching unit, and the negative pole of the fourth turn-off device serves as the negative pole of the second switching unit. The connection point of the third and fourth turn-off capable devices serves as a third endpoint. The third switching unit includes a fifth turn-off device and a sixth turn-off device. The cathode of the fifth turn-off device is connected in series with the anode of the sixth turn-off device. An anode of the fifth turn-off device serves as an anode of the third switching unit, and a cathode of the sixth turn-off device serves as a cathode of the third switching unit. The connection point of the fifth turn-off capable device and the sixth turn-off capable device serves as a fourth endpoint. The full-bridge sub-modules are connected to the corresponding circuits through the third end point and the fourth end point. The working state of the full-bridge submodule comprises one of blocking, half blocking or bypass.
The full-bridge sub-module locking means that the third, fourth, fifth and sixth turn-off devices of the full-bridge sub-module are all turned off. The schematic diagram of the full-bridge submodule locking can be referred to fig. 4.
fig. 5 is a schematic diagram of half latch of a full-bridge submodule according to an embodiment. As shown in fig. 5, the half-latch of the full-bridge sub-module means that the third turn-off device of the full-bridge sub-module is turned on, and the fourth, fifth and sixth turn-off devices are turned off. In other embodiments, the third, fourth, and fifth turn-off devices may be turned off, and the sixth turn-off device may be turned on.
FIG. 6 is a schematic diagram of a full bridge sub-module bypass of an embodiment. As shown in fig. 6, the full-bridge sub-module bypass means that the third and fifth turn-off devices of the full-bridge sub-module are turned off, and the fourth and sixth turn-off devices are turned on. Or in other embodiments, the third and fifth turn-off devices are on and the fourth and sixth turn-off devices are off.
fig. 7 is a schematic diagram of a connection between the modular multilevel converter and an ac power grid according to an embodiment. The modular multilevel converter is connected to the alternating current grid through a series charging resistor. In this embodiment, the converter is connected to the ac power grid through the charging resistor R, the bypass switch QA thereof, and the incoming line switch QF. The charging resistor R is connected with the incoming line switch QF in series. The charging resistor R is connected in parallel with the bypass switch QA.
Fig. 8 is a flowchart illustrating a starting method of the half-bridge and full-bridge hybrid modular multilevel converter according to the first embodiment. The method comprises the following steps:
And step S120, controlling all half-bridge sub-modules and all full-bridge sub-modules to be locked so that all half-bridge sub-modules and all full-bridge sub-modules reach initial voltage.
In particular, this step is an uncontrolled start-up phase. That is, at this stage, the control device controls all the submodules to be locked, the incoming line switch QF is closed, and all the submodules are charged, so that all the submodules have the initial voltage capable of working. In this way, the submodules can be put into preparation. The charging resistor R can avoid the damage of system elements caused by overcurrent in the initial stage of charging the alternating current system. And when the current of the charging resistor is smaller than the preset current value, the control equipment controls the bypass of the charging resistor. Or when the voltage of the charging resistor is larger than the preset voltage value, the control device controls the bypass of the charging resistor. Since one full-bridge sub-module can be charged continuously during one cycle of the alternating current, one half-bridge sub-module can be charged only during one half cycle. Thus, over the same charging time, a full-bridge sub-module voltage is approximately twice the voltage of a half-bridge sub-module, and both voltages are lower. In this way the converter is ready for the next working phase. Further, the preset current value may be 0.1 pu. The preset voltage value may be 0.
And step S140, controlling all the half-bridge sub-modules to keep locked, and reducing the total voltage increasing speed of the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules.
In particular, this phase is a half-controlled start-up phase, i.e. the control device only controls the full-bridge sub-module and not the half-bridge sub-module. The control device may control the partial full-bridge sub-modules to half latch so that the full-bridge sub-modules charge during a half cycle of the alternating current. Or the control device controls parts of the full-bridge sub-modules to bypass, so that the full-bridge sub-modules stop charging. Therefore, on one hand, the charging speed of all the full-bridge submodules can be reduced, so that the total voltage rising speed is reduced; on the other hand, the charging speed of all half-bridge sub-modules can be increased, so that the voltage rising speed is increased. Thus, the average voltage of all half-bridge sub-modules gradually increases, and the average voltage of all full-bridge sub-modules gradually increases, but the two gradually approach each other. And finally, equalizing the voltages of all the sub-modules. Therefore, the output voltage of the converter rises smoothly, and the probability of the surge current is reduced.
And step S160, respectively controlling the working states of each full-bridge sub-module and each half-bridge sub-module so as to enable the voltage of all the half-bridge sub-modules to reach the rated voltage and enable the voltage of all the full-bridge sub-modules to reach the rated voltage.
in particular, this phase is a fully controlled start-up phase, i.e. the control device may control the full-bridge and half-bridge sub-modules simultaneously. The working states of all the full-bridge submodules and all the half-bridge submodules can be dynamically controlled so as to slowly regulate the voltages of all the submodules to the rated voltage and finish the starting process.
According to the starting method of the half-bridge and full-bridge mixed modular multilevel converter, firstly, all half-bridge sub-modules and all full-bridge sub-modules are controlled to be locked, namely, all half-bridge sub-modules and all full-bridge sub-modules are charged, so that all half-bridge sub-modules and all full-bridge sub-modules reach initial voltage. Secondly, all the half-bridge sub-modules are controlled to be locked, and the total voltage increase speed of the full-bridge sub-modules is reduced by controlling the working state of at least part of the full-bridge sub-modules. In this way, the average voltage of all half-bridge sub-modules gradually increases, the average voltage of all full-bridge sub-modules gradually increases, and the two gradually approach, and the voltages of all sub-modules are equalized at this time. And then, respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all the half-bridge submodules to reach the rated voltage and enable the voltage of all the full-bridge submodules to reach the rated voltage. In this way, during the starting process of the modular multilevel converter, the voltages of all the full-bridge sub-modules and all the half-bridge sub-modules are slowly increased, and the voltages of all the sub-modules are kept in a more balanced state. Therefore, the output voltage of the modular multilevel converter is slowly increased to the rated voltage, so that larger impact current can be avoided at the moment of unlocking the system, and the safety factor of the power grid system is improved.
fig. 9 is a flowchart illustrating a starting method of a half-bridge and full-bridge hybrid modular multilevel converter according to a second embodiment. Controlling all half-bridge sub-modules to be locked, and controlling the working state of at least part of the full-bridge sub-modules to reduce the increasing speed of the total voltage of the full-bridge sub-modules, namely before the step S140, the method comprises the following steps:
And step S130, detecting whether the voltage of each full-bridge submodule reaches the working threshold of the self-energy-taking power supply. If the voltage of each full-bridge sub-module reaches the operation threshold of the self-powered power supply, step S140 is executed. If the voltage of each full-bridge sub-module does not reach the operation threshold of the self-powered power supply, the step S130 is continuously executed.
specifically, whether the voltage of each full-bridge sub-module reaches the operation threshold of the self-powered power supply means whether each full-bridge sub-module can operate normally. When the voltage of each full-bridge submodule reaches the working threshold of the self-powered power supply, the voltage means that each full-bridge submodule can be triggered to work by itself. Otherwise, the full-bridge sub-modules with the voltage not reaching the working threshold value need to be continuously charged.
before the step of controlling all the half-bridge sub-modules to remain locked and decreasing the overall voltage increase speed of the full-bridge sub-modules by controlling the operating state of at least part of the full-bridge sub-modules, step S140 includes:
When the voltage of each full-bridge sub-module reaches the working threshold of the self-powered power supply, step S141 is executed to control all the half-bridge sub-modules to keep locked.
Specifically, at this time, the voltage of each half-bridge sub-module is less than the voltage of any full-bridge sub-module. This step controls the device so that the half-bridge sub-modules continue to charge.
And S142, controlling the bypass of the full-bridge sub-module with the voltage not less than the first threshold voltage.
In particular, the control device controlling the bypass of the full-bridge sub-modules with a voltage not less than the first threshold voltage may be such that these full-bridge sub-modules are neither charged nor discharged. Therefore, under the same alternating current power grid, the number of the full-bridge sub-modules which are charged simultaneously can be reduced, and the number of the half-bridge sub-modules which are charged is not changed, so that the voltage rising speed of each half-bridge sub-module is accelerated, namely the charging speed of each half-bridge sub-module is accelerated.
And step S143, half locking the full-bridge submodule of which the control voltage is between the second threshold voltage and the first threshold voltage.
Specifically, the second threshold voltage is less than the first threshold voltage. The full-bridge submodule is half-locked when the control device controls the voltage of the full-bridge submodule between the second threshold voltage and the first threshold voltage, so that the full-bridge submodule is equal to the half-bridge submodule, on one hand, the voltage of the full-bridge submodule is small, the charging can be continued, but the charging speed is reduced. On the other hand, the charging speed of each half bridge module can be further increased.
And step S144, locking the full-bridge submodule of which the control voltage is smaller than the second threshold voltage.
Specifically, the control device controls the voltage of the full-bridge sub-modules having the voltage smaller than the second threshold voltage to be small, so that the full-bridge sub-modules are locked even though the full-bridge sub-modules continue to be charged at the normal speed.
Through the steps, the control equipment can reduce the overall charging speed of all the full-bridge sub-modules, so that the overall charging speed of all the half-bridge sub-modules is improved. The average voltage of all half-bridge sub-modules gradually increases. The average voltage of all full-bridge sub-modules also gradually increases. But the average voltage of all half-bridge sub-modules increases more rapidly than the average voltage of all full-bridge sub-modules. Finally, the average voltage of the half-bridge sub-modules and the average voltage of the full-bridge sub-modules tend to be consistent, that is, the average voltage of the half-bridge sub-modules and the average voltage of the full-bridge sub-modules can be equal or approximately equal. Therefore, the voltages of all the submodules in the converter gradually reach an equilibrium state, and finally the voltages of all the submodules reach the working threshold of the self-powered power supply, so that the design difficulty of the self-powered power supply of each submodule is reduced. In addition, the voltage of the converter rises slowly, so that the impact current can be effectively avoided.
Fig. 10 is a flowchart illustrating a starting method of a half-bridge and full-bridge hybrid modular multilevel converter according to a third embodiment. In this embodiment, after the step of controlling all the half-bridge sub-modules to remain locked and decreasing the total voltage increase speed of the full-bridge sub-modules by controlling the operating states of at least some of the full-bridge sub-modules, that is, after step S140, the method includes:
step S151, determining whether a ratio of the average voltage of all half-bridge sub-modules to the average voltage of all full-bridge sub-modules is greater than a preset multiple.
and step S153, when the ratio of the average voltage of all half-bridge sub-modules to the average voltage of all full-bridge sub-modules is greater than a preset multiple, controlling all full-bridge sub-modules to be half-locked and controlling all half-bridge sub-modules to be locked.
in this way, the control device may make all full-bridge submodules equal to half-bridge submodules, i.e. all submodules in the converter are half-bridge submodules. At this moment, the sub-module type in the current converter can be single, and control of control equipment is facilitated. Specifically, the preset multiple may be in the range of 0.6 to 1.4. In this way, the average voltage of all half-bridge sub-modules is approximately equal to the average voltage of all full-bridge sub-modules. I.e. the voltage of the converter reaches a balanced state and the voltage of the converter is always kept in a balanced increase.
in this embodiment, the step of respectively controlling the operating states of each full-bridge sub-module and each half-bridge sub-module to make the total voltage of all half-bridge sub-modules and all full-bridge sub-modules reach the rated voltage, that is, the step S160 includes:
step S161, controlling the full-bridge sub-module bypass whose voltage is not less than the third threshold voltage, and controlling the half-bridge sub-module bypass whose voltage is not less than the third threshold voltage.
specifically, when the voltage of the converter is close to the rated voltage, the control device controls the partial full-bridge sub-module with higher voltage to stop charging, namely to be in a bypass state. The control device controls the half-bridge sub-module with higher voltage to stop charging, namely to be in a bypass state. In this way, the voltage rise speed of all the sub-modules is continuously reduced so that the total voltage of all the sub-modules slowly approaches the rated voltage. So as to avoid the current converter from causing larger impact current at the moment of unlocking.
fig. 11 is a block diagram of a starting apparatus of a half-bridge and full-bridge hybrid modular multilevel converter according to an embodiment. A starting device of a half-bridge and full-bridge mixed modular multilevel converter comprises a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules, wherein the modular multilevel converter is connected to an alternating current power grid through series charging resistors. The device includes:
an uncontrolled start module 120, configured to control all half-bridge sub-modules and all full-bridge sub-modules to be locked, so that all half-bridge sub-modules and all full-bridge sub-modules reach an initial voltage;
The half-control starting module 140 is used for controlling all half-bridge sub-modules to keep locked and reducing the total voltage increasing speed of the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; the working state of the full-bridge submodule comprises one of blocking, semi-blocking or bypass;
The full-control starting module 160 is used for respectively controlling the working states of each full-bridge sub-module and each half-bridge sub-module so as to enable the voltages of all the half-bridge sub-modules to reach the rated voltage and enable the voltages of all the full-bridge sub-modules to reach the rated voltage; wherein, the working state of the half-bridge submodule comprises bypass or latch-up.
Above-mentioned starting drive of modularization multilevel converter that half-bridge and full-bridge mix, at first, control all half-bridge submodule pieces and all full-bridge submodule pieces and all keep shutting, all half-bridge submodule pieces and all full-bridge submodule pieces are all in the process of charging promptly to make all half-bridge submodule pieces and all full-bridge submodule pieces all reach initial voltage. Secondly, all the half-bridge sub-modules are controlled to be locked, and the total voltage increase speed of the full-bridge sub-modules is reduced by controlling the working state of at least part of the full-bridge sub-modules. In this way, the average voltage of all half-bridge sub-modules gradually increases, the average voltage of all full-bridge sub-modules gradually increases, and the two gradually approach, and the voltages of all sub-modules are equalized at this time. And then, respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all the half-bridge submodules to reach the rated voltage and enable the voltage of all the full-bridge submodules to reach the rated voltage. In this way, during the starting process of the modular multilevel converter, the voltages of all the full-bridge sub-modules and all the half-bridge sub-modules are slowly increased, and the voltages of all the sub-modules are kept in a more balanced state. Therefore, the output voltage of the modular multilevel converter is slowly increased to the rated voltage, so that larger impact current can be avoided at the moment of unlocking the system, and the safety factor of the power grid system is improved.
In one embodiment, the half-controlled start module 140 is configured to control all half-bridge sub-modules to keep locked when the voltage of each full-bridge sub-module reaches an operating threshold of the self-powered power supply;
the half-control starting module 140 is also used for controlling the full-bridge sub-module bypass with the voltage not less than the first threshold voltage;
the half-control starting module 140 is further configured to control half locking of the full-bridge sub-module when the voltage is between the second threshold voltage and the first threshold voltage; wherein the second threshold voltage is less than the first threshold voltage;
the half-controlled start module 140 is also used for controlling the locking of the full-bridge sub-module with the voltage smaller than the second threshold voltage.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
the above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. a method of starting a half-bridge and full-bridge hybrid modular multilevel converter, the modular multilevel converter comprising a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules, the method comprising:
controlling the plurality of half-bridge sub-modules and the plurality of full-bridge sub-modules to be locked so that all half-bridge sub-modules and all full-bridge sub-modules reach respective initial voltages;
Controlling the plurality of half-bridge sub-modules to keep locked, and reducing the total voltage increasing speed of all the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; wherein the working state of the full-bridge submodule comprises one of blocking, half blocking or bypass;
Respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all half-bridge submodules and the voltage of all full-bridge submodules to reach rated voltage; wherein the operating state of the half-bridge sub-module comprises bypass or latch-up.
2. The method according to claim 1, characterized in that the modular multilevel converter is connected to an alternating current grid through a series charging resistor.
3. the method of claim 2, wherein the step of keeping all the half-bridge sub-modules locked and reducing the overall voltage increase speed of the full-bridge sub-modules by controlling the operating state of at least some of the full-bridge sub-modules is preceded by the steps of:
And when the current of the charging resistor is smaller than a preset current value, controlling the bypass of the charging resistor.
4. The method of claim 2, wherein the step of keeping all the half-bridge sub-modules locked and reducing the overall voltage increase speed of the full-bridge sub-modules by controlling the operating state of at least some of the full-bridge sub-modules is preceded by the steps of:
And when the voltage of the charging resistor is greater than a preset voltage value, controlling the bypass of the charging resistor.
5. the method of claim 1, wherein the step of keeping all half-bridge sub-modules locked and the step of reducing the overall voltage increase rate of the full-bridge sub-modules by controlling the operating state of at least some of the full-bridge sub-modules comprises:
When the voltage of each full-bridge submodule reaches the working threshold value of the self-energy-taking power supply, controlling all the half-bridge submodules to keep locking;
A full-bridge sub-module bypass controlling the voltage to be not less than a first threshold voltage;
half locking of the full-bridge submodule is achieved, wherein the control voltage is between a second threshold voltage and the first threshold voltage; wherein the second threshold voltage is less than the first threshold voltage;
and locking the full-bridge sub-modules with the control voltage smaller than the second threshold voltage.
6. The method of claim 1, wherein the step of keeping all half-bridge sub-modules latched and reducing the overall voltage increase rate of the full-bridge sub-modules by controlling the operating state of at least some of the full-bridge sub-modules is followed by the steps of:
and when the ratio of the average voltage of all half-bridge sub-modules to the average voltage of all full-bridge sub-modules is greater than a preset multiple, controlling all full-bridge sub-modules to be half-locked and controlling all half-bridge sub-modules to be locked.
7. The method of claim 6, wherein the preset multiple is in the range of 0.6 to 1.4.
8. the method of claim 1, wherein the step of separately controlling the operating states of each full-bridge sub-module and each half-bridge sub-module such that the voltages of all half-bridge sub-modules and the voltages of all full-bridge sub-modules reach the rated voltages comprises:
and the full-bridge sub-module bypass with the control voltage not less than the third threshold voltage, and the half-bridge sub-module bypass with the control voltage not less than the third threshold voltage.
9. a starting device for a half-bridge and full-bridge hybrid modular multilevel converter, the modular multilevel converter comprising a plurality of half-bridge sub-modules and a plurality of full-bridge sub-modules, the modular multilevel converter being connected to an AC power grid through series charging resistors, the device comprising:
the uncontrolled starting module is used for controlling all half-bridge sub-modules and all full-bridge sub-modules to be locked so as to enable all half-bridge sub-modules and all full-bridge sub-modules to reach initial voltage;
The half-control starting module is used for controlling all half-bridge sub-modules to keep locked and reducing the total voltage increasing speed of the full-bridge sub-modules by controlling the working state of at least part of the full-bridge sub-modules; wherein the working state of the full-bridge submodule comprises one of blocking, half blocking or bypass;
The full-control starting module is used for respectively controlling the working states of each full-bridge submodule and each half-bridge submodule so as to enable the voltage of all the half-bridge submodules to reach the rated voltage and enable the voltage of all the full-bridge submodules to reach the rated voltage; wherein the operating state of the half-bridge sub-module comprises bypass or latch-up.
10. The apparatus of claim 9, wherein the half-controlled start module is configured to control all half-bridge sub-modules to remain locked when the voltage of each full-bridge sub-module reaches an operating threshold of the self-powered power supply;
The half-control starting module is also used for controlling a full-bridge sub-module bypass with the voltage not less than a first threshold voltage;
the half-control starting module is also used for controlling half locking of the full-bridge submodule, the voltage of which is between a second threshold voltage and the first threshold voltage; wherein the second threshold voltage is less than the first threshold voltage;
the half-control starting module is also used for controlling the locking of the full-bridge submodule of which the voltage is smaller than the second threshold voltage.
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| CN201810395466.4A CN108471251B (en) | 2018-04-27 | 2018-04-27 | starting method and device of half-bridge and full-bridge mixed modular multilevel converter |
| JP2020551422A JP7125504B2 (en) | 2018-04-27 | 2018-08-23 | Start-up method and apparatus for modular multi-level converter in which half-bridge and full-bridge coexist |
| PCT/CN2018/101987 WO2019205368A1 (en) | 2018-04-27 | 2018-08-23 | Method and device for starting half bridge-full bridge hybrid modular multilevel converter |
| KR1020207028332A KR102440726B1 (en) | 2018-04-27 | 2018-08-23 | Method and apparatus for starting a modular multilevel converter in which half-bridge and full-bridge are mixed |
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| CN201810395466.4A CN108471251B (en) | 2018-04-27 | 2018-04-27 | starting method and device of half-bridge and full-bridge mixed modular multilevel converter |
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| CN111103486B (en) * | 2019-12-23 | 2022-05-20 | 国家电网有限公司 | Flexible direct current converter valve submodule type identification method and valve base controller |
| EP4162599A1 (en) * | 2020-07-24 | 2023-04-12 | Siemens Energy Global GmbH & Co. KG | Assembly and method for operating same |
| EP4162598A1 (en) * | 2020-07-24 | 2023-04-12 | Siemens Energy Global GmbH & Co. KG | Converter and method for operating same |
| CN114070107B (en) * | 2020-07-31 | 2023-08-08 | 南京南瑞继保电气有限公司 | Charging control method and device for hybrid converter |
| JP7143548B1 (en) * | 2021-10-20 | 2022-09-28 | 東芝三菱電機産業システム株式会社 | power converter |
| WO2024091083A1 (en) * | 2022-10-27 | 2024-05-02 | 에이치디한국조선해양 주식회사 | Modular multilevel converter and power system using same |
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| JP7125504B2 (en) | 2022-08-24 |
| WO2019205368A1 (en) | 2019-10-31 |
| KR102440726B1 (en) | 2022-09-06 |
| KR20200125988A (en) | 2020-11-05 |
| JP2021516946A (en) | 2021-07-08 |
| CN108471251A (en) | 2018-08-31 |
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