CN113922407A - Low-pressure pressurizing system of flexible direct current converting station and control method - Google Patents
Low-pressure pressurizing system of flexible direct current converting station and control method Download PDFInfo
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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
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
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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
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- 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 application aims to provide a low-pressure pressurization system of a flexible direct current converter station and a control method. The flexible-direct current converter station comprises a flexible-direct current converter valve and a valve controller, wherein the flexible-direct current converter valve comprises 3 parallel-connected phase bridge arms, the phase bridge arms are formed by connecting an upper bridge arm and a lower bridge arm in series, the positive end of the upper bridge arm is connected with a direct current positive electrode, the negative end of the upper bridge arm is connected with the positive end of the lower bridge arm, the negative end of the lower bridge arm is connected with a direct current negative electrode, the upper bridge arm and the lower bridge arm respectively comprise N sub-modules and bridge arm reactors, N is an integer greater than or equal to 2, each sub-module comprises a power semiconductor device, a direct current capacitor and a sub-module controller, and the sub-module controller controls the sub-modules to operate; the valve controller is communicated with the submodule controller, and is characterized in that: the low-voltage pressurization system comprises a low-voltage power supply and a diode valve string; according to the grounding mode of the flexible direct current converter valve, a low-voltage power supply is connected with the direct current capacitors of the submodules at the negative ends of any upper bridge arm, lower bridge arm or phase bridge arm in parallel, and the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
Description
Technical Field
The application relates to the technical field of high-power electronic converter, in particular to a low-voltage pressurization system of a flexible direct current converter station and a control method.
Background
With the application and development of power electronic technology in power systems, power electronic equipment develops towards high-voltage high-capacity modularization, and is particularly widely applied to the fields of flexible direct-current transmission systems, chain type static var generators and the like.
A flexible dc transmission system is generally composed of several sub-modules connected in series or in parallel. After troubleshooting or long-time shutdown of the flexible direct current transmission system, before formal operation, it is necessary to detect the insulation levels of direct current transmission equipment such as an alternating current converter, a converter transformer, a smoothing reactor and the like and a direct current line and whether a control system meets normal operation requirements, and a commonly adopted detection means is a no-load pressurization test.
The no-load pressurization test is a DC power transmission debugging test project with a charged system, and mainly aims to detect the on/off capacity and the voltage withstanding capacity of a converter valve, the insulation level of DC primary equipment and the correctness of the sequential control and protection system action of a secondary control system. The no-load pressurization test is carried out before the system is put into operation, so that the risk of formal unlocking operation can be reduced, and the method has great significance for safe operation of the flexible direct-current power transmission system.
The existing no-load pressurization test system and test method need to use a high-voltage alternating current power supply, as mentioned in patent "CN 107102224A a no-load pressurization test method of a power transmission system, and a performance detection method and device thereof".
However, in practical engineering applications, the field usually does not have the power supply condition of the high-voltage alternating-current power supply. Taking an offshore wind power flexible direct current system as an example, offshore wind power grid connection is an important application of flexible direct current transmission, and a flexible direct current offshore converter station needs to be built on an offshore platform.
Considering the limitation of offshore construction conditions, the installation and test of large equipment cannot be completed at sea, and the offshore platform is integrally conveyed to a designated sea area after the equipment is installed and debugged on a wharf. When the offshore flexible-direct current converter station arrives at a designated sea area, the quality defect and other problems of large equipment are found, the platform is required to be integrally transported to a test dock for treatment, and the cost and the time cost are very high.
For the application working conditions, a device test link needs to be carried out on the wharf. However, a dock generally can only provide a low-voltage power supply with a small capacity, and does not have the power supply condition of a high-voltage alternating-current power supply.
Therefore, a scheme for performing a low-voltage pressurization test on the soft-direct current converter only by using an external low-voltage power supply is needed, and the working condition of the high-voltage alternating-current power supply can be simulated; meanwhile, compared with a test mode of directly connecting a high-voltage alternating-current power supply, the low-voltage power supply with small capacity is safer, and test risks are reduced.
The above information disclosed in this background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The application aims to provide a low-voltage pressurizing system and a control method for a flexible direct current converter station, a low-voltage power supply with small capacity is used for carrying out equipment test, the system safety is guaranteed, and the test risk is reduced.
According to one aspect of the application, the low-voltage pressurization system of the flexible-direct current converter station comprises the flexible-direct current converter valve and a valve controller, wherein the flexible-direct current converter valve comprises 3 parallel-connected phase bridge arms, the phase bridge arms are formed by connecting an upper bridge arm and a lower bridge arm in series, the positive end of the upper bridge arm is connected with a direct current positive electrode, the negative end of the upper bridge arm is connected with the positive end of the lower bridge arm, the negative end of the lower bridge arm is connected with a direct current negative electrode, the upper bridge arm and the lower bridge arm respectively comprise N sub-modules and bridge arm reactors, N is an integer greater than or equal to 2, each sub-module comprises a power semiconductor device, a direct current capacitor and a sub-module controller, and the sub-module controller controls the sub-modules to operate; the valve controller is in communication with the sub-module controller:
the low-voltage pressurization system comprises a low-voltage power supply and a diode valve string;
according to the grounding mode of the flexible direct current converter valve, the low-voltage power supply is connected with the direct current capacitors of the submodules of any upper bridge arm, any lower bridge arm or any phase bridge arm negative end in parallel, and the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
According to some embodiments, if the absolute values of the voltages to ground of the dc positive electrode and the dc negative electrode of the soft-dc converter valve are equal or close, the low-voltage power supply is connected in parallel with the dc capacitor of the sub-module at the negative terminal of any upper bridge arm, and the diode valve string is sequentially connected to the dc capacitor positive electrodes of the other sub-modules of the bridge arm.
According to some embodiments, if the dc negative electrode of the soft-dc converter valve is grounded, the low-voltage power supply is connected in parallel to the dc capacitors of the submodules at any of the lower bridge arm or the negative terminal of the phase bridge arm, and the diode valve string is sequentially connected to the dc capacitor anodes of the other submodules of the bridge arm.
According to some embodiments, if the dc positive electrode of the soft-dc converter valve is grounded, the low-voltage power supply passes through an isolation transformer and then is connected in parallel with the dc capacitors of the sub-modules at any of the upper bridge arm, the lower bridge arm, or the negative end of the phase bridge arm, and the diode valve string is sequentially connected to the dc capacitor positive electrodes of the other sub-modules of the bridge arm.
According to some embodiments, if the soft-direct converter valve is not grounded or grounded via a grounding switch and the grounding switch is disconnected, the low-voltage power supply is connected in parallel with the dc capacitors of the sub-modules of any of the upper bridge arm, the lower bridge arm or the negative terminal of the phase bridge arm, and the diode valve string is sequentially connected to the dc capacitor anodes of the other sub-modules of the bridge arm.
According to some embodiments, the sub-modules are half-bridge circuits, full-bridge circuits, three-level circuits, or a combination thereof.
According to some embodiments, the diode valve string comprises at least N-1 or 2N-1 diode units, the diode units being connected in series in the same direction, the diode units comprising diode formation or diodes connected in series with a current limiting unit;
the anode ends of all the diode units and the cathode ends of the tail end diode units form lead-out points with the same number as the sub-modules, and the lead-out points are connected with the anodes of the direct current capacitors of the sub-modules in a one-to-one corresponding mode or connected with the anodes of the direct current capacitors of the sub-modules in a one-to-one corresponding mode after passing through the current limiting units;
the current limiting unit comprises a resistor and/or an inductor.
According to some embodiments, the low voltage power supply is a dc power supply, wherein the negative electrode is connected to ground.
According to some embodiments, the low voltage power supply comprises a diode, the diode anode being connected to the low voltage power supply anode.
According to some embodiments, the low voltage power supply output is connected in series with a first high voltage switch; and the insulation voltage level of the first high-voltage switch is not lower than the alternating-current side voltage of the flexible direct-current converter valve.
According to an aspect of the application, a method of controlling a low pressure pressurization system of a flexible direct current converter station according to any one of the preceding claims is proposed, comprising:
the low-voltage power supply charges the direct-current capacitors of the submodules in the upper bridge arm, the lower bridge arm or the phase bridge arm connected with the low-voltage power supply, and the upper bridge arm, the lower bridge arm or the phase bridge arm is called a charging bridge arm;
after the charging is finished, the charging bridge arm is started to operate, and controllable voltage is output to charge other bridge arms of the flexible-direct converter valve;
after the other bridge arms are charged, the upper bridge arm and the lower bridge arm of any phase are controlled voltage sources at the same time, and direct current voltages are equivalently applied to the direct current positive electrode and the direct current negative electrode.
According to some embodiments, the low voltage power supply charges the dc capacitors of the submodules in the upper leg, the lower leg or the phase leg connected thereto, including:
the low-voltage power supply of the low-voltage pressurization system is started to charge the direct-current capacitor of the submodule connected with the low-voltage power supply in the charging bridge arm, and the submodule controller is electrified and operated;
the submodule controller controls the submodules to output zero level, a charging loop is established for the direct current capacitors of the adjacent submodules in the charging bridge arm by combining the diode valve string, the direct current capacitor voltage of the adjacent submodules reaches a starting value, and the submodule controller is electrified;
and sequentially completing the charging of the direct current capacitors of all the submodules, wherein the submodule controllers of the charging bridge arms are all electrified.
According to some embodiments, the charging bridge arm starts to operate, and outputs a controllable voltage to charge other bridge arms of the flexible-direct converter valve, including:
if the charging bridge arm is the upper bridge arm or the lower bridge arm, the other bridge arm in the same phase is marked as a charging in-phase bridge arm;
if the charging bridge arm is the phase bridge arm, the charging in-phase bridge arm is equivalently short-circuited;
the submodule of the charging bridge arm is subjected to circulating bypass voltage-sharing charging, so that the direct-current capacitor voltage of the submodule reaches a first rated voltage, and the valve controller controls the charging bridge arm to output a first controlled voltage source;
the first controlled voltage source is connected in series with a charging in-phase bridge arm to charge the direct-current capacitors of the submodules of the other two-phase bridge arm;
the submodules of the other two phases of bridge arms respectively or simultaneously carry out the circulating bypass voltage-sharing charging so that the direct-current capacitor voltage of the submodules reaches the first rated voltage;
if the charging bridge arm is the phase bridge arm, the step is finished;
the valve controller controls any one phase of upper and lower bridge arms different from the charging bridge arm to respectively output a second controlled voltage source and a third controlled voltage source;
the first controlled voltage source, the second controlled voltage source, the third controlled voltage source and the charging in-phase bridge arm form a loop to charge the charging in-phase bridge arm;
and the circulation bypass of the submodule of the charging in-phase bridge arm is charged in a voltage-sharing manner, so that the direct-current capacitor voltage of the submodule reaches the first rated voltage.
According to some embodiments, the upper bridge arm and the lower bridge arm of any phase are controlled voltage sources at the same time, and the equivalent application of the direct current voltage to the direct current positive electrode and the direct current negative electrode includes:
and adjusting any one phase or multi-phase bridge arm to output the controlled voltage source, so that the integral output direct-current voltage of the phase bridge arm is twice of the second rated voltage.
According to some embodiments, the controlled voltage sources each output a direct voltage.
According to some embodiments, further comprising adjusting the magnitude of the second nominal voltage by:
adjusting the number of the sub-modules outputting the first rated voltage in the upper bridge arm or/and the lower bridge arm; and/or
Adjusting the first rated voltage of the DC capacitor of each of the submodules in the upper bridge arm or/and the lower bridge arm,
and the Udc is the second rated voltage, the Vc2 is the first rated voltage, and the P is the number of the sub-modules.
According to some embodiments, the second and third controlled voltage sources are a composite voltage Uac1 and Uac2, the composite voltage being superimposed by an alternating voltage Uac and a direct voltage Udc, wherein:
Uac1＝Udc+Uac，Uac2＝Udc-Uac，Uac1+Uac2＝2Udc。
according to some embodiments, the method further comprises switching off the first high-voltage switch after the three-phase bridge arm is charged, the three-phase bridge arm is unlocked, the direct-current positive electrode and the direct-current negative electrode present direct-current voltages, and the midpoint of the three-phase bridge arm presents three-phase alternating-current voltages.
According to some embodiments, further comprising:
carrying out voltage withstand test and/or sampling calibration on direct current and alternating current accessory equipment or an alternating current and direct current line in the pressurizing process;
insulation breakdown faults occur in the pressurizing process, and the safety of equipment is guaranteed by utilizing fast overcurrent protection of a bridge arm and/or short-circuit protection of a power semiconductor device.
Technical solutions according to some embodiments of the present application may have one or more of the following benefits:
1. the application provides a low pressure pressurization system comprises low voltage power supply and diode valve cluster, under the different ground mode of gentle straight converter valve, adopts different connected mode, can realize charging step by step of submodule piece direct current electric capacity, solves the power supply problem of numerous submodule pieces through low voltage power supply, reduces experimental condition and experimental demand, need not to connect high voltage alternating voltage source among the experimentation.
2. After the charging process of the low-voltage power supply is completed, the bridge arm active voltage-sharing method provided by the application starts the charging bridge arm to operate, and charges other bridge arms of the converter valve by utilizing the characteristic that the charging bridge arm can output controllable voltage; the sub-modules in all bridge arms are electrified, and the direct current capacitor charging efficiency of the whole converter valve sub-module is greatly improved.
3. After the step of active voltage sharing of the bridge arms is completed, the submodule can be unlocked after energy taking is completed, any phase of upper and lower bridge arms are controlled voltage sources at the same time, and direct-current voltage is generated and applied to a direct-current positive electrode and a direct-current negative electrode; the direct-current pressurizing process of the converter valve can be simulated.
4. The method and the device can also enable the direct current positive electrode and the direct current negative electrode to present direct current voltage and enable the middle point of the three-phase bridge arm to present three-phase alternating current voltage by unlocking the flexible direct current converter valve and applying a control target of alternating current voltage and direct current voltage, and simulate the working condition that the converter valve applies a high-voltage alternating current power supply.
5. The present application may also provide ancillary functions: carrying out voltage withstand test and sampling calibration on direct current and alternating current accessory equipment in the pressurizing process; if insulation breakdown fault occurs in the pressurizing process, the safety of equipment is guaranteed by utilizing fast overcurrent protection of a bridge arm and/or short-circuit protection of a power semiconductor device.
6. The method can also be popularized to all topologies adopting modularization multi-level, for example, a low-voltage power supply is realized in the STATCOM equipment to charge a single bridge arm or a module of the whole equipment, then the passive inversion is unlocked, and the insulation performance and the basic function of the equipment are checked.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are for illustrative purposes only of certain embodiments of the present application and are not intended to limit the present application.
FIG. 1 illustrates a schematic diagram of a flexible direct current station low pressure pressurization system of an exemplary embodiment;
FIG. 2 illustrates a schematic representation of yet another embodiment of an exemplary flexible direct current station low pressure pressurization system;
FIG. 3 illustrates a schematic representation of yet another embodiment of an exemplary flexible direct current station low pressure pressurization system;
FIG. 4 illustrates a schematic representation of yet another embodiment of an exemplary flexible direct current station low pressure pressurization system;
FIG. 5a shows a schematic diagram of a low voltage power supply of an exemplary embodiment;
FIG. 5b illustrates yet another embodiment of a schematic diagram of an exemplary low voltage power supply;
FIG. 5c shows yet another embodiment of a schematic diagram of an exemplary low voltage power supply;
FIG. 6 illustrates a flow chart of a low voltage power supply charge control method of an exemplary embodiment;
FIG. 7 illustrates a flow diagram of a bridge arm active voltage grading control method of an exemplary embodiment;
FIG. 8 illustrates a flow chart of a split phase DC boost control method of an exemplary embodiment;
fig. 9 illustrates a flow chart of a limp-to-dc converter station low pressure pressurization control method of an exemplary embodiment.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals denote the same or similar parts in the drawings, and thus, a repetitive description thereof will be omitted.
The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the embodiments of the disclosure can be practiced without one or more of the specific details, or with other means, components, materials, devices, or the like. In such cases, well-known structures, methods, devices, implementations, materials, or operations are not shown or described in detail.
The flow charts shown in the drawings are merely illustrative and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.
The terms "first," "second," and the like in the description and claims of the present application and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
It will be appreciated by those skilled in the art that the drawings are merely schematic representations of exemplary embodiments, and that the blocks or processes shown in the drawings are not necessarily required to practice the present application and are, therefore, not intended to limit the scope of the present application.
Embodiments of apparatus of the present application are described below that may be used to perform embodiments of the methods of the present application. For details not disclosed in the embodiments of the apparatus of the present application, reference is made to the embodiments of the method of the present application.
Fig. 1 shows a schematic diagram of a low pressure pressurization system of a flexible direct current converter station in an exemplary embodiment.
The embodiment provides a low-pressure pressurizing system of a flexible direct current converter station, and the flexible direct current converter station comprises a flexible direct current converter valve and a valve controller. As shown in fig. 1, the soft-straight converter valve includes 3 parallel-connected phase leg phases a, B, and C. The phase bridge arms are connected in series by an upper bridge arm and a lower bridge arm, the positive end of the upper bridge arm is electrically connected with a direct current positive electrode, the negative end of the upper bridge arm is electrically connected with the positive end of the lower bridge arm, and the negative end of the lower bridge arm is electrically connected with a direct current negative electrode.
According to some embodiments, the low voltage of the low voltage pressurization system is 300V-1500V.
As shown in fig. 1, taking phase a as an example, the upper arm and the lower arm have similar structures, and therefore, the specific structure of the lower arm is not shown. The upper bridge arm comprises N sub-modules 1 and a bridge arm reactor 2, wherein N is an integer greater than or equal to 2. The submodule 1 comprises 2 power semiconductor devices and 1 capacitor, and the first power semiconductor device and the second power semiconductor device are connected in series in the same direction and then connected with the capacitor in parallel. The direct current positive electrode is electrically connected with a bridge arm reactor 2, the other end of the bridge arm reactor 2 is electrically connected with the series connection midpoints of 2 power semiconductor devices of the sub-module 1, the other end of the second power semiconductor device is connected with the series connection midpoints of 2 power semiconductor devices of the next sub-module, the sub-modules are sequentially connected in series, one end of the second power semiconductor device of the Nth sub-module is connected with the series connection midpoints of 2 power semiconductor devices of the sub-module of the lower bridge arm, and one end of the second power semiconductor device of the Nth sub-module of the lower bridge arm is electrically connected with the bridge arm reactor and then is electrically connected with the direct current negative electrode.
According to an example embodiment, the a-phase, B-phase, and C-phase circuit structures are similar.
According to some embodiments, the sub-module 1 may be a half-bridge circuit, a full-bridge circuit, a three-level circuit, or a combination thereof; the submodule 1 also comprises a submodule controller which can control the submodule to operate.
According to an exemplary embodiment, the valve controller communicates with the sub-module controller to control operation of the flexible direct current station low pressure pressurization system.
As shown in fig. 1, the low voltage pressurization system 3 includes a low voltage power source 4 and a diode valve string 5. The anode of the low-voltage power supply 4 is electrically connected with the anode of the diode valve string 5.
According to some embodiments, the diode valve string 5 comprises at least N-1 or 2N-1 diode units.
As shown in fig. 1, in the present embodiment, the diode valve string 5 is connected to a of the upper arm, and includes N-1 diode units.
According to some embodiments, diode valve string 5, when connected to the phase leg, comprises 2N-1 diode units.
According to some embodiments, the diode unit comprises a diode or a diode is connected in series with the current limiting unit 6.
As shown in fig. 1, in this embodiment, the diode unit is connected to the sub-module through the current limiting unit.
According to an exemplary embodiment, the diode cells are connected in series in the same direction, and the diode anode port is defined as an anode terminal and the diode cathode port is defined as a cathode terminal of the diode cells.
According to some embodiments, the anode terminals of all the diode units and the cathode terminals of the terminal diode units form the same number of leading-out points as the number of the submodules, and the leading-out points are connected with the anodes of the direct current capacitors of the submodules in a one-to-one correspondence manner or connected with the anodes of the direct current capacitors of the submodules in a one-to-one correspondence manner after passing through the current limiting unit 6.
As shown in fig. 1, in this embodiment, the anode terminals of all the diode units and the cathode terminals of the terminal diode units form the same number of leading-out points as the number of the submodules, and the leading-out points are connected with the anodes of the direct-current capacitors of the submodules in a one-to-one correspondence manner after passing through the current limiting unit 6.
According to some embodiments, the current limiting unit 6 is constituted by a resistor and/or an inductor.
According to an example embodiment, when the absolute values of the voltages to ground of the direct current positive electrode and the negative electrode of the flexible direct current converter valve are equal or close, the low-voltage power supply 4 is connected in parallel with the direct current capacitor of the submodule at the negative end of any upper bridge arm; the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
Fig. 2 illustrates a schematic representation of yet another embodiment of an exemplary limp-to-dc converter station low pressure pressurization system.
According to an example embodiment, the circuit shown in fig. 2 is substantially the same as the circuit shown in fig. 1, except that: when the direct current negative electrode of the flexible direct current converter valve is grounded, the low-voltage power supply is connected with the direct current capacitor of the submodule at the negative end of any lower bridge arm or phase bridge arm in parallel; the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
Fig. 3 illustrates a schematic representation of yet another embodiment of an exemplary limp-to-dc converter station low pressure pressurization system.
According to an example embodiment, the circuit shown in fig. 3 is substantially the same as the circuit shown in fig. 1, except that: when the direct current positive electrode of the flexible direct current converter valve is grounded, the low-voltage power supply passes through the isolation transformer 7 and then is connected in parallel with the direct current capacitor of the submodule at the negative end of any upper bridge arm, lower bridge arm or phase bridge arm; the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
Fig. 4 illustrates a schematic representation of yet another embodiment of an exemplary limp-to-dc converter station low pressure pressurization system.
According to an example embodiment, the circuit shown in fig. 4 is substantially the same as the circuit shown in fig. 1, except that: when the flexible direct current converter valve is not grounded or is grounded through the grounding switch and the grounding switch 8 is disconnected, the low-voltage power supply is connected with the direct current capacitor of the submodule at any upper bridge arm, lower bridge arm or negative end of the phase bridge arm in parallel; the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
Fig. 5a shows a schematic diagram of a low voltage power supply of an exemplary embodiment.
As shown in fig. 5a, the low voltage power supply is a dc power supply, wherein the negative electrode is grounded.
Fig. 5b shows yet another embodiment of a schematic diagram of an exemplary low voltage power supply.
As shown in fig. 5b, the low voltage power supply comprises a diode 9 and a dc power supply, and the anode of the diode 9 is connected to the anode of the dc power supply.
Fig. 5c shows yet another embodiment of a schematic diagram of an exemplary low voltage power supply.
As shown in fig. 5c, the low voltage power output is connected in series with the first high voltage switch 10, and the insulation voltage level of the first high voltage switch 10 is not lower than the ac side voltage of the vdc converter valve.
Fig. 6 shows a flowchart of a low-voltage power supply charging control method of an exemplary embodiment.
In S610, the low-voltage power supply is started to charge the dc capacitor of the sub-module connected to the low-voltage power supply in the charging bridge arm, and the sub-module controller is powered on to operate.
According to an example embodiment, a low-voltage power supply is used for charging the phase a upper bridge arm, the low-voltage power supply is started to charge the direct-current capacitor of the nth sub-module of the phase a upper bridge arm, and the nth sub-module controller of the phase a upper bridge arm is powered on and operates to control the second power semiconductor of the nth sub-module to be conducted.
In S630, the sub-module is controlled to output a zero level, a charging loop is established for the dc capacitor of the adjacent sub-module, and the voltage of the dc capacitor of the adjacent sub-module reaches a starting value Vc 1.
According to an exemplary embodiment, the submodule controller of the upper bridge arm of the phase a controls the submodule to output a zero level, a charging loop is established for the direct current capacitance of the adjacent submodule, that is, the second power semiconductor device of the nth submodule of the upper bridge arm of the phase a is turned on, so that the direct current capacitance voltage of the nth-1 submodule of the upper bridge arm of the phase a reaches a starting value Vc1, and the nth-1 submodule controller is powered on to operate, and controls the second power semiconductor device of the nth-1 submodule to be turned on.
And S650, sequentially completing the direct current capacitor charging of all the submodules, wherein the submodule controllers of the charging bridge arm are all electrified.
According to the exemplary embodiment, the upper bridge arm of the phase a sequentially completes the dc capacitor charging of all the submodules, the dc capacitor voltage of the submodules of the upper bridge arm of the phase a reaches the starting value Vc1, and the submodules of the charging bridge arm are all charged.
Fig. 7 shows a flowchart of a bridge arm active voltage-sharing control method according to an exemplary embodiment.
In S710, if the charging bridge arm is an upper bridge arm or a lower bridge arm, the other bridge arm with the same phase is marked as a charging in-phase bridge arm; and if the charging bridge arm is a phase bridge arm, the charging phase bridge arm is equivalently short-circuited.
According to an exemplary embodiment, taking a low-voltage power supply as an example to charge the upper arm of the a phase, the lower arm of the a phase is denoted as a charging in-phase arm.
In S720, the charging bridge arm submodule circularly bypasses the voltage-sharing charging circuit to enable the direct-current capacitor voltage of the submodule to reach a rated value Vc2, and the valve controller controls the charging bridge arm to output a first controlled voltage source.
According to the exemplary embodiment, after the direct-current capacitor voltage of the upper bridge arm of the phase a reaches Vc1, the second power semiconductor devices of the sub-modules of the upper bridge arm of the phase a are controlled to be turned on in turn, so that the direct-current capacitor voltage of the sub-modules reaches a rated value Vc2, and the direct-current capacitor of the upper bridge arm of the phase a is the output voltage of the first controlled voltage source.
At S730, the first controlled voltage source is connected in series to charge the in-phase bridge arm, and charges the dc capacitor of the other two-phase bridge arm sub-module.
According to the exemplary embodiment, after the upper bridge arm and the lower bridge arm of the phase a are connected in series, the direct current capacitors of the sub-modules of the upper and lower bridge arms of the phase B and the phase C are charged, so that the direct current capacitor voltages of the sub-modules of the upper and lower bridge arms of the phase B and the phase C reach the starting value Vc 1.
In S740, the other two-phase bridge arm submodules are respectively or simultaneously charged with voltage sharing by the bypass circuit, so that the dc capacitor voltage of the submodules reaches the rated value Vc 2.
According to the exemplary embodiment, after the direct-current capacitor voltages of the upper and lower bridge arms of the B-phase and the C-phase reach Vc1, the second power semiconductor devices of the sub-modules of the upper and lower bridge arms of the B-phase and the C-phase are controlled to be conducted in turn, so that the direct-current capacitor voltages of the sub-modules reach a rated value Vc 2.
In S750, it is determined whether the charging arm is a phase arm.
If the charging bridge arm is a phase bridge arm, the step is finished; and if the charging bridge arm is not the phase bridge arm, continuing to execute the following steps.
In S760, the upper and lower bridge arms of any phase different from the charging bridge arm output the second controlled voltage source and the third controlled voltage source, respectively.
According to an example embodiment, the valve controller controls any one of the upper and lower phase bridge arms different from the charging bridge arm to output the second controlled voltage source and the third controlled voltage source, respectively. Namely, the upper and lower bridge arms of the B phase and the C phase respectively output a second controlled voltage source and a third controlled voltage source.
At S770, the charging non-inverting arm is charged.
According to an exemplary embodiment, the first controlled voltage source, the second controlled voltage source and the third controlled voltage source form a loop with the charging in-phase bridge arm, and the charging in-phase bridge arm is charged. Namely, the upper arm of the phase A, and the upper and lower arms of the phases B and C charge the lower arm of the phase A, so that the direct-current capacitor voltage of the sub-module of the lower arm of the phase A reaches Vc 1.
In S780, the charging in-phase bridge arm submodule is charged in a circulating bypass voltage-sharing manner, so that the direct-current capacitor voltage of the submodule reaches a rated value Vc 2.
According to the exemplary embodiment, after the direct-current capacitor voltage of the lower bridge arm of the phase a reaches Vc1, the second power semiconductor devices of the sub-modules of the lower bridge arm of the phase a are controlled to be turned on in turn, so that the direct-current capacitor voltage of the sub-modules reaches a rated value Vc 2.
At S790, it ends.
According to the example embodiment, the bridge arm active voltage-sharing control is completed, and the process is ended.
FIG. 8 illustrates a flow chart of a split phase DC boost control method of an exemplary embodiment.
And S810, finishing the step of bridge arm active voltage-sharing control.
The bridge arm active voltage-sharing control steps are shown in fig. 7.
In S830, any phase or multi-phase bridge arm is adjusted to output the controlled voltage source, so that the phase bridge arm outputs the dc voltage 2Udc as a whole.
According to an example embodiment, the first controlled voltage source, the second controlled voltage source and the third controlled voltage source may each output a direct current voltage, such that the phase leg as a whole outputs a direct current voltage 2 Udc.
According to an example embodiment, the magnitude of the direct voltage Udc may be adjusted, including the following two methods: adjusting the number of sub-modules of the output voltage Vc2 in the upper or/and lower bridge arm; or regulating the rated voltage value Vc2 of the direct current capacitor of each submodule in the upper bridge arm or/and the lower bridge arm.
And the Udc is Vc 2P, and P is the number of sub-modules of the output voltage Vc2 in the upper bridge arm or the lower bridge arm. P finally stabilizes at N/2.
According to an example embodiment, a rising rate of the controlled voltage source to output the dc voltage may be adjusted to control the discharging current to be less than a preset value. In this state, the controlled voltage source charges other bridge arms on the dc bus, and the dc power source in the sub-module of the controlled voltage source is in a discharging state, so that if the rate of adjusting the output dc voltage is too fast, the discharging current is too large, the rising rate needs to be selected reasonably, and the discharging current is controlled to be smaller than the preset value.
According to an example embodiment, the actual operating conditions are simulated, the second controlled voltage source and the third controlled voltage source are respectively a composite voltage Uac1 and Uac2, the composite voltage is superimposed by an alternating voltage Uac and a direct voltage Udc, wherein Uac1 ═ Udc + Uac, Uac2 ═ Udc-Uac, Uac1+ Uac2 ═ 2 Udc.
According to the embodiment, the split-phase direct-current pressurization control method is used for judging whether the sub-modules work normally or not by inputting different phases or switching different sub-modules, observing output voltage and waveforms.
Fig. 9 illustrates a flow chart of a limp-to-dc converter station low pressure pressurization control method of an exemplary embodiment.
In S910, the step of actively equalizing the voltage of the bridge arm is completed.
According to an example embodiment, the step of active bridge arm voltage equalization is completed, as shown in fig. 7; if there is a first high voltage switch 10 in the low voltage power supply, the first high voltage switch 10 is switched off.
And S930, unlocking the flexible direct current converter valve, wherein the direct current positive pole and the direct current negative pole present direct current voltage, and the middle point of the three-phase bridge arm presents three-phase alternating current voltage.
And in S950, after the voltage of the capacitor of the submodule drops to a threshold value, the flexible direct current converter valve is locked, and the test is stopped.
According to the embodiment, electric energy is consumed in the operation process of the sub-modules, so that the capacitor voltage of the sub-modules is reduced to a certain threshold value, the flexible direct current converter valve is locked, and the test is stopped.
According to example embodiments, the present application also has one or more of the following ancillary functional benefits:
1. and carrying out voltage withstand test and sampling calibration on the direct current and alternating current accessory equipment in the pressurizing process.
2. Insulation breakdown faults occur in the pressurizing process, and the safety of equipment is guaranteed by utilizing fast overcurrent protection of a bridge arm and/or short-circuit protection of a power semiconductor device. The fast overcurrent protection of the bridge arm detects the current of the bridge arm through a valve controller, and when the current exceeds an action threshold value, the flexible and straight converter valve is locked to stop the test; the short-circuit protection of the power semiconductor device is realized by immediately locking and bypassing the submodules after the submodules controller detects that the power device has a short-circuit fault, reporting the fault to the valve controller, and locking the flexible-straight converter valve and stopping the test when the submodules which have faults simultaneously exceed a certain number.
It should be clearly understood that this application describes how to make and use particular examples, but the application is not limited to any details of these examples. Rather, these principles can be applied to many other embodiments based on the teachings of the present disclosure.
Furthermore, it should be noted that the above-mentioned figures are only schematic illustrations of the processes involved in the method according to exemplary embodiments of the present application, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, e.g., in multiple modules.
Exemplary embodiments of the present application are specifically illustrated and described above. It is to be understood that the application is not limited to the details of construction, arrangement, or method of implementation described herein; on the contrary, the intention is to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (19)
1. A low-voltage pressurization system of a flexible direct current converter station comprises the flexible direct current converter valve and a valve controller, wherein the flexible direct current converter valve comprises 3 parallel-connected phase bridge arms, the phase bridge arms are formed by connecting an upper bridge arm and a lower bridge arm in series, the positive end of the upper bridge arm is connected with a direct current positive electrode, the negative end of the upper bridge arm is connected with the positive end of the lower bridge arm, the negative end of the lower bridge arm is connected with a direct current negative electrode, the upper bridge arm and the lower bridge arm respectively comprise N sub-modules and bridge arm reactors, N is an integer greater than or equal to 2, the sub-modules comprise power semiconductor devices, direct current capacitors and sub-module controllers, and the sub-module controllers control the sub-modules to run; the valve controller is in communication with the sub-module controller, characterized by:
the low-voltage pressurization system comprises a low-voltage power supply and a diode valve string;
according to the grounding mode of the flexible direct current converter valve, the low-voltage power supply is connected with the direct current capacitors of the submodules of any upper bridge arm, any lower bridge arm or any phase bridge arm negative end in parallel, and the diode valve string is sequentially connected with the direct current capacitor anodes of other submodules of the bridge arm.
2. The system according to claim 1, wherein if the absolute values of the voltages to ground of the dc positive and dc negative poles of the flexible dc converter valve are equal or close, the low voltage power supply is connected in parallel with the dc capacitors of the submodules of any of the negative terminals of the upper bridge arm, and the diode valve string is in turn connected to the dc capacitor positive poles of the other submodules of the bridge arm.
3. The system according to claim 1, wherein if said dc negative terminal of said flexibile dc converter valve is grounded, said low voltage power supply is connected in parallel with said dc capacitors of said sub-modules of any of said lower bridge arm or said negative terminal of said phase bridge arm, and said diode valve string is in turn connected with said dc capacitor positive terminals of other said sub-modules of that bridge arm.
4. The system according to claim 1, wherein if the dc positive terminal of the compliance converter valve is grounded, the low voltage power source is connected in parallel to the dc capacitors of the sub-modules at the negative terminal of any of the upper bridge arm, the lower bridge arm, or the phase bridge arm after passing through an isolation transformer, and the diode string is connected in series to the dc capacitor positive terminals of the other sub-modules of the bridge arm.
5. The system according to claim 1, wherein if said converter valve is not grounded or is grounded via a grounding switch and the grounding switch is off, said low voltage power source is connected in parallel with said dc capacitors of said sub-modules of any of said upper bridge arm, said lower bridge arm or said negative terminal of said phase bridge arm, and said diode string is in turn connected to said dc capacitor anodes of other said sub-modules of that bridge arm.
6. The low voltage pressurization system of claim 1, wherein the sub-module is a half bridge circuit, a full bridge circuit, a three level circuit, or a combination thereof.
7. The system according to claim 1, characterized in that said diode valve string comprises at least N-1 or 2N-1 diode units, connected in series in the same direction, said diode units comprising diode formation or diodes connected in series with a current limiting unit;
the anode ends of all the diode units and the cathode ends of the tail end diode units form lead-out points with the same number as the sub-modules, and the lead-out points are connected with the anodes of the direct current capacitors of the sub-modules in a one-to-one corresponding mode or connected with the anodes of the direct current capacitors of the sub-modules in a one-to-one corresponding mode after passing through the current limiting units;
the current limiting unit comprises a resistor and/or an inductor.
8. The low voltage pressurization system according to claim 1, wherein said low voltage power source is a direct current power source, wherein the negative electrode is grounded.
9. The low-voltage pressurization system according to claim 1, wherein said low-voltage power source comprises a diode, and said diode anode is connected to said low-voltage power source anode.
10. The low voltage pressurization system of claim 9, wherein said low voltage power supply output is connected in series with a first high voltage switch; and the insulation voltage level of the first high-voltage switch is not lower than the alternating-current side voltage of the flexible direct-current converter valve.
11. A method of controlling a flexible direct current converter station low pressure pressurisation system according to any of claims 1-10, characterised in that it comprises:
the low-voltage power supply charges the direct-current capacitors of the submodules in the upper bridge arm, the lower bridge arm or the phase bridge arm connected with the low-voltage power supply, and the upper bridge arm, the lower bridge arm or the phase bridge arm is called a charging bridge arm;
after the charging is finished, the charging bridge arm is started to operate, and controllable voltage is output to charge other bridge arms of the flexible-direct converter valve;
after the other bridge arms are charged, the upper bridge arm and the lower bridge arm of any phase are controlled voltage sources at the same time, and direct current voltages are equivalently applied to the direct current positive electrode and the direct current negative electrode.
12. The control method of claim 11, wherein the low voltage power supply charges the dc capacitors of the submodules in the upper leg, the lower leg, or the phase leg connected thereto, and comprises:
the low-voltage power supply of the low-voltage pressurization system is started to charge the direct-current capacitor of the submodule connected with the low-voltage power supply in the charging bridge arm, and the submodule controller is electrified and operated;
the submodule controller controls the submodules to output zero level, a charging loop is established for the direct current capacitors of the adjacent submodules in the charging bridge arm by combining the diode valve string, the direct current capacitor voltage of the adjacent submodules reaches a starting value, and the submodule controller is electrified;
and sequentially completing the charging of the direct current capacitors of all the submodules, wherein the submodule controllers of the charging bridge arms are all electrified.
13. The control method according to claim 11, wherein the charging bridge arm starts to operate and outputs a controllable voltage to charge other bridge arms of the soft-direct converter valve, and the method comprises the following steps:
if the charging bridge arm is the upper bridge arm or the lower bridge arm, the other bridge arm in the same phase is marked as a charging in-phase bridge arm;
if the charging bridge arm is the phase bridge arm, the charging in-phase bridge arm is equivalently short-circuited;
the submodule of the charging bridge arm is subjected to circulating bypass voltage-sharing charging, so that the direct-current capacitor voltage of the submodule reaches a first rated voltage, and the valve controller controls the charging bridge arm to output a first controlled voltage source;
the first controlled voltage source is connected in series with a charging in-phase bridge arm to charge the direct-current capacitors of the submodules of the other two-phase bridge arm;
the submodules of the other two phases of bridge arms respectively or simultaneously carry out the circulating bypass voltage-sharing charging so that the direct-current capacitor voltage of the submodules reaches the first rated voltage;
if the charging bridge arm is the phase bridge arm, the step is finished;
the valve controller controls any one phase of upper and lower bridge arms different from the charging bridge arm to respectively output a second controlled voltage source and a third controlled voltage source;
the first controlled voltage source, the second controlled voltage source, the third controlled voltage source and the charging in-phase bridge arm form a loop to charge the charging in-phase bridge arm;
and the circulation bypass of the submodule of the charging in-phase bridge arm is charged in a voltage-sharing manner, so that the direct-current capacitor voltage of the submodule reaches the first rated voltage.
14. The control method according to claim 13, wherein the upper bridge arm and the lower bridge arm of any phase are controlled voltage sources at the same time, and the equivalent application of the direct-current voltage to the direct-current positive electrode and the direct-current negative electrode comprises:
and adjusting any one phase or multi-phase bridge arm to output the controlled voltage source, so that the integral output direct-current voltage of the phase bridge arm is twice of the second rated voltage.
15. The control method of claim 14, wherein the controlled voltage sources each output a dc voltage.
16. The control method of claim 13, further comprising adjusting the magnitude of the second nominal voltage by:
adjusting the number of the sub-modules outputting the first rated voltage in the upper bridge arm or/and the lower bridge arm; and/or
Adjusting the first rated voltage of the DC capacitor of each of the submodules in the upper bridge arm or/and the lower bridge arm,
and the Udc is the second rated voltage, the Vc2 is the first rated voltage, and the P is the number of the sub-modules.
17. Control method according to claim 13, characterized in that the second controlled voltage source, the third controlled voltage source are a composite voltage Uac1 and Uac2, which composite voltage is superimposed by an alternating voltage Uac and a direct voltage Udc, wherein:
Uac1＝Udc+Uac，Uac2＝Udc-Uac，Uac1+Uac2＝2Udc。
18. the control method according to claim 11, further comprising switching off a first high-voltage switch after the three-phase bridge arm is charged, the three-phase bridge arm is unlocked, the direct-current positive electrode and the direct-current negative electrode present direct-current voltages, and a midpoint of the three-phase bridge arm presents a three-phase alternating-current voltage.
19. The control method according to claim 11, characterized by further comprising:
carrying out voltage withstand test and/or sampling calibration on direct current and alternating current auxiliary equipment or an alternating current and direct current line in the pressurizing process;
when insulation breakdown fault occurs in the pressurizing process, the safety of equipment is guaranteed by utilizing fast overcurrent protection of a bridge arm and/or short-circuit protection of a power semiconductor device.
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| CN202111056378.XA CN113922407B (en) | 2021-09-09 | 2021-09-09 | Low-voltage pressurizing system of flexible direct-current converter station and control method |
| EP22739003.6A EP4227692A4 (en) | 2021-01-13 | 2022-01-11 | Modular batch energy acquisition and commutation circuit and control method |
| PCT/CN2022/071342 WO2022152124A1 (en) | 2021-01-13 | 2022-01-11 | Modular batch energy acquisition and commutation circuit and control method |
| JP2023531533A JP2023550783A (en) | 2021-01-13 | 2022-01-11 | Modular batch energy acquisition commutation circuit and control method |
| KR1020237019681A KR20230107312A (en) | 2021-01-13 | 2022-01-11 | Modular arrangement energy acquisition current circuit and control method |
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