CN112564538B - Method and device for determining converter parameters - Google Patents
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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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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
- H02M1/4208—Arrangements for improving power factor of AC input
- H02M1/4233—Arrangements for improving power factor of AC input using a bridge converter comprising active switches
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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
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
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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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses a method and a device for determining converter parameters. The method is applied to a direct-current traction power supply system, the direct-current traction power supply system at least comprises a converter, the converter comprises a plurality of sub-modules, each sub-module in the plurality of sub-modules comprises a switching device, and the method comprises the following steps: acquiring initial voltage and initial current of a switching device; adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition; and determining the proportion of full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the converter is a modular multilevel converter. The invention solves the technical problems that the existing bidirectional converter has insufficient peak power and cannot meet the requirements of a direct-current traction power supply system.
Description
Technical Field
The invention relates to the field of rail transit traction power supply, in particular to a method and a device for determining converter parameters.
Background
At present, domestic subways mostly adopt a 1500V or 750V direct current traction power supply mode, most traction substations adopt diode rectifying devices, braking energy cannot be fed back to an alternating current power grid, and direct current voltage of the traction power grid can be increased. The direct current traction power supply system for the urban rail transit is a low-voltage and high-current system, and the alternating current voltage grade is higher while the direct current voltage grade is lower.
At present, a bidirectional converter for a low-voltage direct-current system mostly adopts a two-level three-phase half-bridge topology, is limited by the through-current capacity of a fully-controlled switch device, has insufficient peak power and is difficult to meet the requirement of actual conditions. If the peak power is to be improved, the device, the bridge arm and the converter need to be connected in parallel and multiplexed in multiple levels, so that a series of problems of dynamic current sharing and steady-state current sharing can be caused. Meanwhile, the two-level converter has low switching frequency and high harmonic content, influences the electric energy quality of a public power grid, and needs a filter with a larger volume.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The embodiment of the invention provides a method and a device for determining converter parameters, which at least solve the technical problems that the existing bidirectional converter has insufficient peak power and cannot meet the requirements of a direct-current traction power supply system.
According to an aspect of an embodiment of the present invention, there is provided a method for determining a parameter of an inverter, which is applied to a dc traction power supply system, where the dc traction power supply system includes at least an inverter, the inverter includes a plurality of sub-modules, and each sub-module of the plurality of sub-modules includes a switching device, including: acquiring initial voltage and initial current of a switching device; adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition; and determining the proportion of full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the converter is a modular multilevel converter.
Further, the method for determining the converter parameter further comprises the following steps: acquiring rated direct current voltage of a traction network and rated direct current of the traction network corresponding to the direct current traction power supply system; determining an initial multiple relation between a rated direct current voltage of a traction network and an initial voltage of a switching device of each submodule to obtain an initial voltage grade; determining an initial voltage according to the initial voltage grade; determining an initial multiple relation between rated direct current of a traction network and initial current of a switching device of each submodule to obtain an initial current grade; an initial current is determined based on the initial current level.
Further, the method for determining the converter parameter further comprises the following steps: obtaining the rated capacity of the current converter before adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition; determining a current peak value of each bridge arm in the current converter according to the initial current; and determining the peak value of the current alternating-current component of each bridge arm according to the current peak value of each bridge arm, the rated direct-current voltage and the rated capacity of the converter.
Further, the method for determining the converter parameter further comprises the following steps: acquiring the power factor of the alternating current side of the converter; calculating the product of the rated direct current voltage of the traction network and the rated direct current of the traction network to obtain a first calculation result; calculating the product of the current alternating-current component peak value of each bridge arm and the alternating-current side power factor of the converter to obtain a second calculation result; calculating the ratio of the first calculation result to the second calculation result to obtain a phase voltage peak value; and calculating the ratio of the phase voltage peak value to the rated direct current of the traction network to obtain a voltage modulation ratio.
Further, the method for determining the converter parameter further comprises the following steps: adjusting the initial voltage grade to obtain an adjusted initial voltage grade; adjusting the initial current grade to obtain the adjusted initial current grade; and obtaining a target voltage modulation ratio according to the adjusted initial voltage and the adjusted initial current, wherein the product of the target voltage modulation ratio and the alternating-current side power factor of the converter is smaller than a preset value.
Further, the method for determining the converter parameter further comprises the following steps: determining a target multiple relation according to the adjusted initial voltage grade; determining the total number of sub-modules and the number of full-bridge sub-modules contained in the current converter according to the target multiple relation and the target voltage modulation ratio; and calculating the ratio of the number of the full-bridge submodules to the total number to obtain the proportion of the full-bridge submodules.
Further, the voltage modulation ratio is greater than 1.
According to another aspect of the embodiments of the present invention, there is also provided an apparatus for determining parameters of an inverter, which is applied to a dc traction power supply system, where the dc traction power supply system includes at least an inverter, the inverter includes a plurality of sub-modules, and each sub-module of the plurality of sub-modules includes a switching device, including: the acquisition module is used for acquiring the initial voltage and the initial current of the switching device; the adjusting module is used for adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition; and the determining module is used for determining the proportion of full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the converter is a modular multilevel converter.
According to another aspect of the embodiments of the present invention, there is also provided a non-volatile storage medium having a computer program stored therein, wherein the computer program is configured to perform the above-mentioned method for determining converter parameters when running.
According to another aspect of the embodiments of the present invention, there is also provided a processor for running a program, wherein the program is configured to perform the above method of determining converter parameters when running.
In the embodiment of the invention, after the initial voltage and the initial current of the switching device are obtained by adjusting the parameters of the modular multilevel converter, the voltage modulation ratio meeting the preset condition is obtained by adjusting the initial voltage and the initial current, and then the proportion of full-bridge sub-modules of the full-bridge sub-modules contained in the converter is determined according to the voltage modulation ratio, wherein the converter is the modular multilevel converter and comprises a plurality of sub-modules, and each sub-module in the plurality of sub-modules comprises the switching device.
In the process, the modular multilevel converter is applied to a direct-current traction power supply system, wherein the bridge arm voltage of the modular multilevel converter is high, the current of a switching device is small, parallel connection and multiplexing are not needed, and the problem that the peak power of the existing bidirectional converter is insufficient is solved. In addition, the equivalent switching frequency in the modular multilevel converter is high, the harmonic content is low, and when the number of the sub-modules in the modular multilevel converter is enough, a filter is not needed, so that the problem that the existing direct-current traction power supply system needs a filter with a larger volume is solved. Finally, this application is through adjusting switching device's initial voltage and initial current for the full-bridge submodule piece proportion of the full-bridge submodule piece that the transverter contains can draw power supply system's demand looks adaptation with current direct current, and then has promoted direct current and has drawn power supply system's power supply efficiency.
Therefore, the purpose of meeting the requirements of the direct-current traction power supply system is achieved by the scheme provided by the application, the technical effect of improving the power supply efficiency of the direct-current traction power supply system is achieved, and the technical problems that an existing bidirectional converter is insufficient in peak power and cannot meet the requirements of the direct-current traction power supply system are solved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is a flow chart of a method of determining converter parameters according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an alternative DC traction power supply system according to an embodiment of the present invention;
fig. 3 is a schematic diagram of an alternative modular multilevel converter according to an embodiment of the invention;
FIG. 4 is a schematic diagram of an alternative hybrid MMC bridge arm voltage according to an embodiment of the present invention;
fig. 5 is a flow chart of an alternative method of determining converter parameters according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an apparatus for determining converter parameters according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Example 1
In accordance with an embodiment of the present invention, there is provided an embodiment of a method for determining converter parameters, it is noted that the steps illustrated in the flowchart of the drawings may be performed in a computer system such as a set of computer executable instructions, and that while a logical order is illustrated in the flowchart, in some cases the steps illustrated or described may be performed in an order different than that presented herein.
Fig. 1 is a flowchart of a method for determining converter parameters according to an embodiment of the present invention, as shown in fig. 1, the method includes the following steps:
step S102, an initial voltage and an initial current of the switching device are obtained.
It should be noted that the method provided by this embodiment may be applied to a dc traction power supply system, where the dc traction power supply system includes at least an inverter, the inverter includes a plurality of sub-modules, and each sub-module of the plurality of sub-modules includes a switching device. Optionally, fig. 2 shows a schematic diagram of an optional dc traction power supply system, and as can be seen from fig. 2, in the dc traction power supply system, a 110kV urban power supply is subjected to voltage reduction processing to obtain a 35kV medium-voltage network, and then is connected with the dc traction network through a converter (i.e., a hybrid MMC in fig. 2) to implement power supply for the urban rail transit vehicle.
The converter is a bidirectional converter, wherein the bidirectional converter has the characteristics of stable and adjustable direct-current voltage, bidirectional energy flow, active and reactive power decoupling control and the like. Preferably, in the present application, the Converter is a Modular Multilevel Converter (MMC), wherein the Modular Multilevel Converter is a bidirectional Converter topology that is most widely applied in the field of high-voltage flexible direct-current power transmission, and compared with a conventional two-level or three-level Converter, the MMC has the advantages of small harmonic content, high upper limit of capacity, no need of parallel multiplexing, and the like.
In an alternative embodiment, fig. 3 shows a schematic diagram of an alternative modular multilevel converter, and in fig. 3, a bridge arm of a hybrid MMC is formed by mixing a full-bridge submodule and a half-bridge submodule, and has a high voltage modulation ratio. The full-bridge submodule outputs a negative level, so that the bridge arm voltage can be increased, the alternating current of the bridge arm is reduced, and the peak current in the switch device is reduced. Thus. When the switching devices with the same current level are selected, the peak power of the MMC is larger than that of an existing two-level or three-level converter, and the MMC also has direct-current fault clearing capacity, so that a traction network and a public power grid can be isolated, and the use of a direct-current breaker is reduced.
In addition, it should be noted that the above-mentioned switching device may be the transistors S1-S6 in fig. 3, and the initial voltage and the initial current of the switching device may be determined by determining the initial voltage level and the initial current level of the switching device.
And step S104, adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition.
It should be noted that the full-bridge sub-module ratio of the hybrid MMC is the most basic and important parameter in the main loop parameters, and directly affects the economy of the topology. After the proportion of the full-bridge submodule is determined, parameters such as submodule capacitor, bridge arm inductance and the like can be calculated and selected.
Optionally, the initial voltage and the initial current may be subjected to related processing to obtain a voltage modulation ratio, and then the initial voltage level and the initial current level are adjusted to obtain an adjusted initial voltage and an adjusted initial current, so that the voltage modulation ratio calculated by the adjusted initial voltage and the adjusted initial current meets the preset condition.
And S106, determining the proportion of the full-bridge submodules contained in the converter according to the voltage modulation ratio.
It should be noted that, in the prior art, the hybrid MMC is not applied to the dc traction power supply system, and in other fields, the full-bridge submodule proportion selection method of the hybrid MMC is mostly based on the working condition that the voltage modulation ratio is smaller than 1, and the hybrid MMC is applied to the dc traction power supply system in this application, and the dc voltage output by the hybrid MMC is equal to the traction voltage, in order to reduce the ac current in the bridge arm, the ac voltage needs to be increased, so that the voltage modulation ratio m is greater than 1, and the full-bridge submodule is in the negative level output state for a long time, that is, in this application, the voltage modulation ratio is greater than 1. In case each leg consists of N sub-modules, the MMC may comprise F full-bridge sub-modules and H half-bridge sub-modules, wherein N, F and H satisfy N ═ F + H. After the total number of the submodules contained in the MMC and the number of the full-bridge submodules are obtained through calculation, the proportion of the full-bridge submodules can be determined according to the N-F + H, and then parameters such as the capacitor of the submodules, the inductance of a bridge arm and the like are calculated and type-selected according to the proportion of the full-bridge submodules.
Based on the solutions defined in steps S102 to S106, it can be known that, in the embodiment of the present invention, after the initial voltage and the initial current of the switching device are obtained by adjusting the parameters of the modular multilevel converter, the voltage modulation ratio meeting the preset condition is obtained by adjusting the initial voltage and the initial current, and then the full-bridge submodule proportion of the full-bridge submodule included in the converter is determined according to the voltage modulation ratio, where the converter is the modular multilevel converter, the converter includes a plurality of submodules, and each of the plurality of submodules includes a switching device.
It is easy to notice that, in the above process, the modular multilevel converter is applied to the dc traction power supply system, wherein the bridge arm voltage of the modular multilevel converter is high, the current of the switching device is small, and the parallel connection and multiplexing are not needed, so that the problem of insufficient peak power of the existing bidirectional converter is overcome. In addition, the equivalent switching frequency in the modular multilevel converter is high, the harmonic content is low, and when the number of the sub-modules in the modular multilevel converter is enough, a filter is not needed, so that the problem that the existing direct-current traction power supply system needs a filter with a larger volume is solved. Finally, this application is through adjusting switching device's initial voltage and initial current for the full-bridge submodule piece proportion of the full-bridge submodule piece that the transverter contains can draw power supply system's demand looks adaptation with current direct current, and then has promoted direct current and has drawn power supply system's power supply efficiency.
Therefore, the purpose of meeting the requirements of the direct-current traction power supply system is achieved by the scheme provided by the application, the technical effect of improving the power supply efficiency of the direct-current traction power supply system is achieved, and the technical problems that an existing bidirectional converter is insufficient in peak power and cannot meet the requirements of the direct-current traction power supply system are solved.
In an alternative embodiment, the initial voltage and the initial current of the switching device need to be obtained before the voltage modulation ratio is calculated. Specifically, firstly, rated direct current voltage of a traction network and rated direct current of the traction network corresponding to the direct current traction power supply system are obtained, then, an initial multiple relation between the rated direct current voltage of the traction network and initial voltage of a switching device of each submodule is determined, an initial voltage grade is obtained, and the initial voltage is determined according to the initial voltage grade. And determining an initial multiple relation between the rated direct current of the traction network and the initial current of the switching device of each submodule to obtain an initial current grade, and determining the initial current according to the initial current grade.
Alternatively, the converter package may be determined based on the voltage level (i.e., initial voltage level) of the commonly used switching devicesThe capacitor voltage U of each sub-moduleCWherein the capacitor voltage of the submodule is half of the rated voltage of the switching device, in this application, U is selectedCSo that the rated DC voltage U of the traction networkdcIs UCInteger multiple K (i.e., the initial multiple relationship). Likewise, the initial current can also be determined by the method described above, wherein the multiple between the rated direct current of the traction network and the initial current of the switching element of each submodule is also K.
In an optional embodiment, before the initial voltage and the initial current are adjusted to obtain a voltage modulation ratio meeting a preset condition, the rated capacity of the converter is obtained, the current peak value of each bridge arm in the converter is determined according to the initial current, and then the current alternating-current component peak value of each bridge arm is determined according to the current peak value of each bridge arm, the rated direct-current voltage and the rated capacity of the converter.
Optionally, determining a current peak value I of the bridge arm according to the initial current levelarm-peakAnd the current peak value of the bridge arm is half of the direct current of the switching device. Then, the peak value I of the AC component of the current is calculated according to the following formulam：
In the above equation, S is the rated capacity of the inverter.
Further, after the current alternating current component peak value is obtained, the alternating current side power factor of the converter is obtained, then, the product between the rated direct current voltage of the traction network and the rated direct current of the traction network is calculated to obtain a first calculation result, the product between the current alternating current component peak value of each bridge arm and the alternating current side power factor of the converter is calculated to obtain a second calculation result, then, the ratio between the first calculation result and the second calculation result is calculated to obtain a phase voltage peak value, and finally, the ratio between the phase voltage peak value and the rated direct current of the traction network is calculated to obtain a voltage modulation ratio.
Alternatively, it can be calculated from the conservation of powerPeak value of phase voltage U to converterm：
In the above formula, IdcRated direct current for the traction network, UdcIdcIs a first calculation result;
is the ac side power factor of the inverter,
is the second calculation result.
It should be noted that, in order to keep the capacitance voltage balance of the half-bridge sub-modules, the bridge arm current must be bipolar, and needs to be satisfied
The AC side power factor of the converter satisfies the following conditions:
in addition, after the phase voltage peak value is obtained, the voltage modulation ratio m is calculated according to the following formula:
in addition, it should be noted that the voltage modulation ratio needs to satisfy the bipolar condition of the bridge arm current, that is, the voltage modulation ratio needs to satisfy:
if the voltage modulation ratio does not meet the preset condition, the voltage grade and the current grade of the switching device need to be reselected, namely, the initial voltage and the initial current are adjusted to obtain the voltage modulation ratio meeting the preset condition. Specifically, the initial voltage level is adjusted to obtain the adjusted initial voltage level, and the initial voltage level is adjusted at the same timeAnd obtaining an adjusted initial current level according to the current level, and obtaining a target voltage modulation ratio according to the adjusted initial voltage and the adjusted initial current, wherein the product of the target voltage modulation ratio and the alternating-current side power factor of the converter is smaller than a preset value, and optionally, the preset value can be 2.
Furthermore, after the voltage modulation ratio is obtained, the full-bridge submodule proportion of the full-bridge submodule included in the converter can be determined according to the voltage modulation ratio. Specifically, firstly, a target multiple relation is determined according to the adjusted initial voltage level, then, the total number of the sub-modules contained in the current converter and the number of the full-bridge sub-modules are determined according to the target multiple relation and the target voltage modulation ratio, and finally, the ratio of the number of the full-bridge sub-modules to the total number is calculated to obtain the proportion of the full-bridge sub-modules.
Optionally, as shown in a schematic diagram of a hybrid MMC bridge arm voltage shown in fig. 4, when an ac-side voltage reaches a positive peak, an upper bridge arm needs to output a maximum negative voltage, and a lower bridge arm needs to output a maximum positive voltage, that is, the number of modules in the bridge arm needs to satisfy the output capacities of the maximum negative voltage and the maximum positive voltage:
the method is simplified and can be obtained:
wherein K is the rated direct current voltage U of the traction networkdcIs UCThe integer multiple of the number of the submodules in the bridge arm of the converter and the minimum value of the number of the full-bridge submodules can be obtained through calculation according to the formula.
Optionally, fig. 5 shows a flow chart of an optional method for determining converter parameters, and as can be seen from fig. 5, the method for determining converter parameters provided in the present application is integrated into a calculation model, and then a user may input MMC capacity, rated dc voltage of a traction network, and commutation voltage into the calculation modelAc side power factor of the device. At the moment, the calculation model selects the voltage grade of the switching device and the capacitance voltage of the sub-module contained in the converter, selects the current grade of the switching device and the bridge arm current peak value, calculates the bridge arm current alternating current component peak value, calculates the phase voltage peak value according to the bridge arm current alternating current component peak value, and calculates the voltage modulation ratio according to the phase voltage peak value. Finally, whether the voltage modulation ratio is satisfied is detected
If not, continuing to repeat the operation; and if so, outputting the minimum value of the number of the bridge arm sub-modules and the minimum value of the number of the bridge arm full-bridge sub-modules.
According to the content, the mixed MMC of the full-bridge submodule and the half-bridge submodule is applied to a direct-current traction power supply system, wherein the bridge arm voltage of the mixed MMC is high, the current of a switching device is small, and parallel connection and multiplexing are not needed; the equivalent switching frequency is high, the harmonic content is small, the filter volume is small, and when the number of modules is large enough, the filter is not even needed; and, mixed type MMC modular design, expansibility is good, can adapt to a plurality of voltage classes, and the capacity upper limit of single converter is high. Finally, the hybrid MMC also has direct current fault clearing capacity, isolates a traction network and a public power grid, and reduces the use of a direct current breaker.
Example 2
According to an embodiment of the present invention, there is also provided an apparatus for determining converter parameters, which is applied to a dc traction power supply system, where the dc traction power supply system includes at least a converter, the converter includes a plurality of sub-modules, and each sub-module of the plurality of sub-modules includes a switching device, where fig. 6 is a schematic diagram of an apparatus for determining converter parameters according to an embodiment of the present invention, and as shown in fig. 6, the apparatus includes: an acquisition module 601, an adjustment module 603, and a determination module 605.
The obtaining module 601 is configured to obtain an initial voltage and an initial current of the switching device; an adjusting module 603, configured to adjust the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition; the determining module 605 is configured to determine a full-bridge submodule proportion of a full-bridge submodule included in the converter according to the voltage modulation ratio, where the converter is a modular multilevel converter.
It should be noted that the acquiring module 601, the adjusting module 603, and the determining module 605 correspond to steps S102 to S106 in the foregoing embodiment, and the three modules are the same as the examples and application scenarios realized by the corresponding steps, but are not limited to the disclosure in embodiment 1.
Optionally, the obtaining module includes: the device comprises a first obtaining module, a first determining module, a second determining module, a third determining module and a fourth determining module. The first acquisition module is used for acquiring rated direct-current voltage of a traction network and rated direct current of the traction network corresponding to the direct-current traction power supply system; the first determining module is used for determining the initial multiple relation between the rated direct-current voltage of the traction network and the initial voltage of the switching device of each submodule to obtain an initial voltage grade; the second determining module is used for determining the initial voltage according to the initial voltage level; the third determining module is used for determining the initial multiple relation between the rated direct current of the traction network and the initial current of the switching device of each submodule to obtain an initial current grade; and the fourth determining module is used for determining the initial current according to the initial current level.
Optionally, the apparatus for determining converter parameters further includes: the device comprises a second obtaining module, a fifth determining module and a sixth determining module. The second obtaining module is used for obtaining the rated capacity of the current converter before the initial voltage and the initial current are adjusted to obtain the voltage modulation ratio meeting the preset condition; the fifth determining module is used for determining the current peak value of each bridge arm in the current converter according to the initial current; and the sixth determining module is used for determining the peak value of the current alternating-current component of each bridge arm according to the current peak value of each bridge arm, the rated direct-current voltage and the rated capacity of the converter.
Optionally, the apparatus for determining converter parameters further includes: the device comprises a third acquisition module, a first calculation module, a second calculation module, a third calculation module and a fourth calculation module. The third obtaining module is used for obtaining the power factor of the alternating current side of the converter; the first calculation module is used for calculating the product of the rated direct-current voltage of the traction network and the rated direct-current of the traction network to obtain a first calculation result; the second calculation module is used for calculating the product of the current alternating-current component peak value of each bridge arm and the alternating-current side power factor of the converter to obtain a second calculation result; the third calculation module is used for calculating the ratio of the first calculation result to the second calculation result to obtain a phase voltage peak value; and the fourth calculation module is used for calculating the ratio of the phase voltage peak value to the rated direct current of the traction network to obtain the voltage modulation ratio.
Optionally, the adjusting module includes: the device comprises a first adjusting module, a second adjusting module and a processing module. The first adjusting module is used for adjusting the initial voltage grade to obtain an adjusted initial voltage grade; the second adjusting module is used for adjusting the initial current grade to obtain the adjusted initial current grade; and the processing module is used for obtaining a target voltage modulation ratio according to the adjusted initial voltage and the adjusted initial current, wherein the product of the target voltage modulation ratio and the alternating-current side power factor of the converter is smaller than a preset value.
Optionally, the determining module includes: a seventh determination module, an eighth determination module, and a ninth determination module. The seventh determining module is used for determining a target multiple relation according to the adjusted initial voltage level; the eighth determining module is used for determining the total number of the submodules contained in the current converter and the number of the full-bridge submodules according to the target multiple relation and the target voltage modulation ratio; and the ninth determining module is used for calculating the ratio of the number of the full-bridge submodules to the total number to obtain the proportion of the full-bridge submodules.
Optionally, the voltage modulation ratio is greater than 1.
Example 3
According to another aspect of the embodiments of the present invention, there is also provided a non-volatile storage medium having a computer program stored therein, wherein the computer program is configured to execute the method for determining the inverter parameter in the above embodiment 1 when running.
Example 4
According to another aspect of the embodiments of the present invention, there is also provided a processor for executing a program, wherein the program is configured to execute the method for determining converter parameters in embodiment 1 when running.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
In the embodiments provided in the present application, it should be understood that the disclosed technology can be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units may be a logical division, and in actual implementation, there may be another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, units or modules, and may be in an electrical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A method of determining converter parameters for use in a dc traction power supply system including at least a converter, the converter including a plurality of sub-modules, each of the sub-modules including a switching device, the method comprising:
acquiring an initial voltage and an initial current of the switching device;
adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition;
determining the proportion of full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the converter is a modular multilevel converter;
wherein, adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition comprises: adjusting an initial voltage level to obtain an adjusted initial voltage level, wherein the initial voltage level is used for determining an initial voltage of the switching device; adjusting an initial current level to obtain an adjusted initial current level, wherein the initial current level is used for determining an initial current of the switching device; obtaining a target voltage modulation ratio according to the adjusted initial voltage and the adjusted initial current, wherein the product of the target voltage modulation ratio and the alternating-current side power factor of the converter is smaller than a preset value;
determining the proportion of full-bridge submodules of the full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the method comprises the following steps: determining a target multiple relation according to the adjusted initial voltage grade; determining the total number of sub-modules contained in the converter and the number of full-bridge sub-modules according to the target multiple relation and the target voltage modulation ratio; and calculating the ratio of the number of the full-bridge submodules to the total number to obtain the proportion of the full-bridge submodules.
2. The method of claim 1, wherein obtaining an initial voltage and an initial current of the switching device comprises:
acquiring rated direct current voltage of a traction network corresponding to the direct current traction power supply system and rated direct current of the traction network;
determining an initial multiple relation between the rated direct-current voltage of the traction network and the initial voltage of the switching device of each submodule to obtain an initial voltage grade;
determining the initial voltage according to the initial voltage level;
determining an initial multiple relation between rated direct current of the traction network and initial current of a switching device of each submodule to obtain an initial current grade;
determining the initial current according to the initial current level.
3. The method of claim 2, wherein before the initial voltage and the initial current are adjusted to obtain a voltage modulation ratio satisfying a preset condition, the method further comprises:
obtaining rated capacity of the converter;
determining a current peak value of each bridge arm in the converter according to the initial current;
and determining the peak value of the current alternating current component of each bridge arm according to the current peak value of each bridge arm, the rated direct current voltage and the rated capacity of the converter.
4. The method of claim 3, further comprising:
acquiring the power factor of the alternating current side of the converter;
calculating the product of the rated direct current voltage of the traction network and the rated direct current of the traction network to obtain a first calculation result;
calculating the product of the current alternating-current component peak value of each bridge arm and the alternating-current side power factor of the converter to obtain a second calculation result;
calculating the ratio of the first calculation result to the second calculation result to obtain a phase voltage peak value;
and calculating the ratio of the phase voltage peak value to the rated direct current of the traction network to obtain the voltage modulation ratio.
5. The method of claim 1, wherein the voltage modulation ratio is greater than 1.
6. An apparatus for determining converter parameters for use in a dc traction power supply system including at least a converter, the converter including a plurality of sub-modules, each of the plurality of sub-modules including a switching device, the apparatus comprising:
the acquisition module is used for acquiring initial voltage and initial current of the switching device;
the adjusting module is used for adjusting the initial voltage and the initial current to obtain a voltage modulation ratio meeting a preset condition;
the determining module is used for determining the proportion of full-bridge submodules contained in the converter according to the voltage modulation ratio, wherein the converter is a modular multilevel converter;
wherein the adjustment module comprises: the first adjusting module is used for adjusting an initial voltage level to obtain an adjusted initial voltage level, wherein the initial voltage level is used for determining an initial voltage of the switching device; the second adjusting module is used for adjusting the initial current level to obtain the adjusted initial current level, wherein the initial current level is used for determining the initial current of the switching device; the processing module is used for obtaining a target voltage modulation ratio according to the adjusted initial voltage and the adjusted initial current, wherein the product of the target voltage modulation ratio and the alternating-current side power factor of the converter is smaller than a preset value;
the determining module comprises: a seventh determining module, configured to determine a target multiple relationship according to the adjusted initial voltage level; an eighth determining module, configured to determine, according to the target multiple relation and the target voltage modulation ratio, the total number of sub-modules included in the converter and the number of full-bridge sub-modules; and the ninth determining module is used for calculating the ratio of the number of the full-bridge sub-modules to the total number to obtain the proportion of the full-bridge sub-modules.
7. A non-volatile storage medium, having a computer program stored thereon, wherein the computer program is arranged to perform the method of determining converter parameters according to any of claims 1 to 5 when executed.
8. A processor for running a program, wherein the program is arranged to perform the method of determining converter parameters of any of claims 1 to 5 when running.
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| CN103904927B (en) * | 2014-04-17 | 2017-02-01 | 华北电力大学 | Additional direct-current voltage control method for modular multi-level current converter |
| US9806633B2 (en) * | 2015-02-06 | 2017-10-31 | Indian Institute Of Technology Bombay | Modular multilevel current source and voltage source converters to increase number of output current levels and output voltage levels |
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