CN116937999A - Converter bridge arm circuit, converter device and precharge control method - Google Patents

Converter bridge arm circuit, converter device and precharge control method Download PDF

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Publication number
CN116937999A
CN116937999A CN202311197340.3A CN202311197340A CN116937999A CN 116937999 A CN116937999 A CN 116937999A CN 202311197340 A CN202311197340 A CN 202311197340A CN 116937999 A CN116937999 A CN 116937999A
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China
Prior art keywords
converter
unit
sub
module
precharge
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Granted
Application number
CN202311197340.3A
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Chinese (zh)
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CN116937999B (en
Inventor
雷健华
马辉
郝传统
秦赓
张勇波
郭志华
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Shenzhen Delian Minghai New Energy Co ltd
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Shenzhen Delian Minghai New Energy Co ltd
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Priority to CN202311197340.3A priority Critical patent/CN116937999B/en
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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc 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
    • H02M7/217—Conversion of ac power input into dc 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
    • H02M7/219—Conversion of ac power input into dc 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 in a bridge configuration
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The application relates to a converter bridge arm circuit, a converter device and a precharge control method, comprising the following steps: each sub-converter module comprises an energy storage unit, a first full-bridge unit and a second full-bridge unit which are arranged in parallel, wherein the first full-bridge unit is configured with a first connecting end and a second connecting end, and the second full-bridge unit is configured with a third connecting end and a fourth connecting end; the switch control module is used for conducting connection between the first connecting end and the third connecting end of each sub-converter module and connection between the second connecting end and the fourth connecting end of each sub-converter module under the condition of precharge requirement, so that a plurality of energy storage units corresponding to the sub-converter modules are connected in parallel and are in a precharge state. The energy storage units of the plurality of sub-converter modules are connected in parallel to be equivalent to the equivalent energy storage unit with larger equivalent capacity value, so that the current limiting effect is greatly improved, and the energy storage units of the plurality of sub-converter modules are precharged under the condition that a large current limiting resistor is not used.

Description

Converter bridge arm circuit, converter device and precharge control method
Technical Field
The application relates to the technical field of electric power, in particular to a converter bridge arm circuit, a converter device and a precharge control method.
Background
The modularized multi-level converter (Modular Multilevel Converter, MMC) is a core device of the high-voltage direct-current transmission system, has the characteristics of high voltage, high power, low harmonic wave, modularization and the like, and can realize flexible change of voltage and power level by adjusting the serial number of the sub-modules. Before the converter is in a stable running state, the capacitor of the sub-converter module is required to be precharged to avoid current impact caused by directly unlocking the converter, in the precharge process, the current of the capacitor in the charging process is usually limited by putting in a resistor with large impedance, however, the resistor with large impedance is large in size and weight, and in addition, the working condition outside the precharge process is bypassed, so that the utilization efficiency of the device is low.
Disclosure of Invention
Based on this, it is necessary to provide a commutation bridge arm circuit, a commutation device and a precharge control method for the problem that the volume and weight of a large-impedance resistor for overcurrent protection provided in the precharge process of a neutron commutation module capacitor in the prior art are large.
In order to achieve the above object, the present application provides a bridge arm circuit for converting current, comprising:
each sub-converter module comprises an energy storage unit, a first full-bridge unit and a second full-bridge unit which are arranged in parallel, wherein the first full-bridge unit is provided with a first connecting end and a second connecting end, the second full-bridge unit is provided with a third connecting end and a fourth connecting end, in the adjacent two stages of sub-converter modules, the first connecting end of the next-stage sub-converter module is connected with the third connecting end of the last-stage sub-converter module, the second connecting end of the next-stage sub-converter module is connected with the fourth connecting end of the last-stage sub-converter module, and the first connecting end and the second connecting end of the first-stage sub-converter module are both used for receiving power supply voltage;
The switch control module is used for conducting connection between the first connecting end and the third connecting end of each sub-converter module and connection between the second connecting end and the fourth connecting end of each sub-converter module under the condition of precharge requirement, so that a plurality of energy storage units corresponding to the sub-converter modules are connected in parallel and are in a precharge state.
In one embodiment, the first full bridge unit comprises: the energy storage device comprises a first switch unit, a second switch unit, a third switch unit and a fourth switch unit, wherein the first switch unit and the second switch unit are connected in series to form a first branch, the third switch unit and the fourth switch unit are connected in series to form a second branch, and the first branch and the second branch are respectively connected in parallel with the energy storage unit;
the connection point between the first switch unit and the second switch unit is used as the first connection end, and the connection point between the third switch unit and the fourth switch unit is used as the second connection end.
In one embodiment, the second full bridge unit comprises: a fifth switching unit, a sixth switching unit, a seventh switching unit and an eighth switching unit, wherein the fifth switching unit and the sixth switching unit are connected in series to form a third branch, the seventh switching unit and the eighth switching unit are connected in series to form a fourth branch, and the third branch and the fourth branch are respectively connected in parallel with the energy storage unit;
The connection point of the fifth switch unit and the sixth switch unit is used as the fourth connection end, and the connection point of the seventh switch unit and the eighth switch unit is used as the third connection end.
In one embodiment, each switching unit comprises a switching tube and a diode which is antiparallel with the switching tube;
during the precharge process of the plurality of cascaded sub-converter modules, each switching tube is in an off state.
In one embodiment, the switch control module includes:
the plurality of first bypass switch units are in one-to-one correspondence with the plurality of sub-converter modules, one end of each first bypass switch unit is connected with the first connecting end, and the other end of each first bypass switch unit is connected with the third connecting end;
the plurality of second bypass switch units are in one-to-one correspondence with the plurality of sub-converter modules, one end of each second bypass switch unit is connected with the second connecting end, and the other end of each second bypass switch unit is connected with the fourth connecting end.
In one embodiment, a converter device is provided, comprising: a bridge arm circuit as described above.
In one embodiment, the method further comprises:
the charging module is used for providing the power supply voltage within a preset range for the plurality of cascaded sub-converter modules;
and the charging switch module is arranged between the charging module and the first-stage sub-converter module and is used for conducting connection between the charging module and the first-stage sub-converter module under the condition of precharge requirement.
In one embodiment, the charging module includes:
a DC power supply unit for providing a DC input voltage;
the voltage conversion unit is connected with the direct current power supply unit, a positive power supply end of the voltage conversion unit is connected with a first connecting end of the first-stage sub-converter module, a negative power supply end of the voltage conversion unit is connected with a second connecting end of the first-stage sub-converter module, and the voltage conversion unit is used for providing precharge voltage for the plurality of cascaded sub-converter modules according to the direct current input voltage.
In one embodiment, the method further comprises:
and the control module is used for acquiring a predicted value of the pre-charging voltage according to the pre-charging voltage, the pre-charging current and the voltage of the energy storage unit which are output in the last cycle of the voltage conversion unit, so as to control the pre-charging voltage output in the next cycle of the voltage conversion unit according to the predicted value.
In one embodiment, the method further comprises:
the isolating switch module is connected with the first connecting end and the second connecting end of the first-stage sub-converter module and the third connecting end and the fourth connecting end of the last-stage sub-converter module, and is used for isolating the charging module from an external circuit under the condition that the plurality of cascaded sub-converter modules are precharged.
In one embodiment, a precharge control method is provided, which is applied to the converter device as described above, and includes:
under the condition of precharge requirement, the control switch control module conducts connection between the first connection end and the third connection end of each sub-converter module in the plurality of cascaded sub-converter modules and connection between the second connection end and the fourth connection end, so that a plurality of energy storage units corresponding to the plurality of sub-converter modules are connected in parallel and are in a precharge state.
In one embodiment, in case the converter device further includes a charging module and a charging switch module, the precharge control method further includes:
under the condition of precharge requirement, the control charging switch module conducts connection between the charging module and the first connection end of the first-stage sub-converter module and conducts connection between the charging module and the second connection end of the first-stage sub-converter module.
In one embodiment, in case the charging module includes a dc power supply unit and a voltage conversion unit, the precharge control method further includes:
acquiring a predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit which are output in a previous cycle of the voltage conversion unit;
and controlling the precharge voltage output by the next period of the voltage conversion unit according to the predicted value.
In one embodiment, the obtaining the predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit output in the last cycle of the voltage conversion unit includes:
according to the precharge voltage, precharge current and voltage of the energy storage unit which are output in a previous period of the voltage conversion unit, a state space equation of a converter bridge arm circuit is constructed;
discretizing the state space equation to obtain a precharge prediction model;
based on constraint conditions, carrying out optimization solution on an objective function to obtain a predicted value of the precharge voltage;
the objective function is set according to a preset voltage value and a pre-charging voltage at a predicted time, and the constraint condition comprises that the pre-charging current is smaller than or equal to a preset current value.
The bridge arm circuit, the switching device and the precharge control method comprise a plurality of cascading sub-switching modules and the switch control module, wherein the first full-bridge unit and the second full-bridge unit of each sub-switching module are respectively provided with double connection ends, so that the energy storage units of the adjacent two-stage sub-switching modules can form a parallel structure, under the condition of precharge requirement, the switch control module conducts the connection between the first connection end and the third connection end and the connection between the second connection end and the fourth connection end of each sub-switching module, so that all sub-switching modules are bypassed, and the energy storage units of all sub-switching modules form an equivalent energy storage unit with larger equivalent capacity value in a parallel structure, thereby greatly improving the current limiting effect, and realizing precharge on the energy storage units of the plurality of sub-switching modules under the condition of not using a large-size and heavy-weight current limiting resistor.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present application, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.
Fig. 1 is a schematic diagram of a bridge arm circuit for converting current provided in an embodiment;
FIG. 2 is a schematic diagram of a sub-converter module according to an embodiment;
FIG. 3 is a schematic diagram of a converter device according to an embodiment;
FIG. 4 is an equivalent circuit diagram of a bridge arm circuit in a pre-charge state according to an embodiment;
FIG. 5 is a schematic diagram of the operation control logic of the control module provided in one embodiment;
FIG. 6 is one of the operational simulation diagrams of the current converting apparatus provided in one embodiment;
fig. 7 is a second simulation diagram of the operation of the converter device according to an embodiment.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Embodiments of the application are illustrated in the accompanying drawings. This application 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.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Also, in this specification, the term "and/or" includes any and all combinations of the associated listed items.
IN one embodiment, referring to fig. 1 (fig. 1 illustrates three cascaded sub-converter modules as an example), a bridge arm circuit is provided, which includes a plurality of cascaded sub-converter modules 100 and a switch control module 200, each sub-converter module 100 includes an energy storage unit 130, a first full-bridge unit 110 and a second full-bridge unit 120 that are arranged IN parallel, the first full-bridge unit 110 is configured with a first connection terminal IN1 and a second connection terminal IN2, the second full-bridge unit 120 is configured with a third connection terminal OUT1 and a fourth connection terminal OUT2, IN adjacent two-stage sub-converter modules 100, the first connection terminal IN1 of the next-stage sub-converter module 100 is connected with the third connection terminal OUT1 of the previous-stage sub-converter module 100, the second connection terminal IN2 of the next-stage sub-converter module 100 is connected with the fourth connection terminal OUT2 of the previous-stage sub-converter module 100, and the first connection terminal IN1 and the second connection terminal IN2 of the first-stage sub-converter module 100 are both used for receiving a supply voltage. The switch control module 200 is configured to conduct connection between the first connection terminal IN1 and the third connection terminal OUT1 of each sub-converter module 100 and connection between the second connection terminal IN2 and the fourth connection terminal OUT2 of each sub-converter module 100 under the condition of the precharge requirement, so that the plurality of energy storage units 130 corresponding to the plurality of sub-converter modules 100 are connected IN parallel and are IN a precharge state.
The converter bridge arm circuit can be applied to a modular multilevel converter MMC, the topological structure can be composed of a plurality of phase units, each phase unit comprises two groups of bridge arms which are connected up and down, the upper bridge arm and the lower bridge arm have the same composition structure, and each bridge arm is composed of the converter bridge arm circuit and the reactor which are provided by the embodiment in series.
The bridge arm circuit includes a plurality of sub-converter modules 100 in cascade connection, each sub-converter module 100 includes a power switch element and an energy storage unit 130, the output voltage of each sub-converter module 100 can be controlled by changing the on time of the power switch element and the charge-discharge time of the energy storage unit 130, and since the voltages of the energy storage units 130 of the sub-converter modules 100 can synthesize the voltage of the bridge arm circuit, each phase unit can generate a multi-level ac output close to a sine wave or a relatively stable dc voltage output based on the switching state of each power switch element of each sub-converter module 100, and can realize extremely low switching frequency and harmonic distortion. That is, the bridge arm circuit can control the output voltage of the bridge arm circuit through the switching of the sub-converter module 100, so that the voltage level of the converter device can be flexibly changed. It should be noted that the energy storage unit 130 includes an element having a storage function, such as an energy storage capacitor.
Since the bridge arm circuit includes a large number of energy storage units 130, during normal operation of the converter device, the voltage of the energy storage units 130 fluctuates around the rated value, but the energy storage units 130 have no initial voltage, if the energy storage units 130 cannot be smoothly charged to the rated value before entering the stable operation working condition, a great surge current can be generated, an overcurrent phenomenon is caused, and the conditions of the converter device and the whole high-voltage direct-current transmission system are threatened. In the precharge process, in order to limit the overcurrent in the starting stage, current limiting resistors are usually connected in series to play a role of overcurrent protection, and the resistor with large impedance has extremely large volume and weight and can be bypassed outside the starting process. Based on this, the present embodiment provides a bridge arm circuit for converting current to overcome the above-mentioned drawbacks.
Further, for the single sub-converter module 100, the sub-converter module 100 includes an energy storage unit 130, a first full-bridge unit 110 and a second full-bridge unit 120, which are arranged in parallel, and the first full-bridge unit 110 and the second full-bridge unit 120 are used as full-bridge circuits with the same structure, the first full-bridge unit 110 is connected in parallel to one side of the energy storage unit 130, and the second full-bridge unit 120 is connected in parallel to the other side of the energy storage unit 130, so that the sub-converter module 100 forms a topology structure obtained by symmetrically turning over the single full-bridge unit. Each full-bridge unit comprises four groups of power semiconductor devices, wherein the power semiconductor devices can be understood as being composed of power switching devices and anti-parallel unidirectional conduction devices, the power semiconductor devices which are connected in series in pairs form a serial branch, and a connecting point formed by serial connection is led out to serve as a connecting end. That is, connection points on two serial branches of the first full-bridge unit 110 are respectively led OUT as a first connection terminal IN1 and a second connection terminal IN2, and connection points on two serial branches of the second full-bridge unit 120 are respectively led OUT as a third connection terminal OUT1 and a fourth connection terminal OUT2, so that the entire topology of the sub-converter module 100 is IN an axisymmetric form.
For the cascaded multiple sub-converter modules 100, the first connection end IN1 and the second connection end IN2 of the nth sub-converter module 100 are respectively and correspondingly connected with the third connection end OUT1 and the fourth connection end OUT2 of the N-1 sub-converter module 100, the third connection end OUT1 and the fourth connection end OUT2 of the nth sub-converter module 100 are respectively and correspondingly connected with the first connection end IN1 and the second connection end IN2 of the n+1th sub-converter module 100, and the energy storage units 130 between two adjacent sub-converter modules 100 can form a parallel connection mode based on the symmetrical dual-port structure of the sub-converter modules 100.
Further, the switch control module 200 may control the on-off state between the first connection terminal IN1 and the third connection terminal OUT1 of each sub-converter module 100 and the on-off state between the second connection terminal IN2 and the fourth connection terminal OUT2 of each sub-converter module 100, and when the sub-converter modules 100 need to be precharged or fail, the switch control module 200 conducts the connection between the first connection terminal IN1 and the third connection terminal OUT1 and the connection between the second connection terminal IN2 and the fourth connection terminal OUT2, so that the sub-converter modules 100 are bypassed. After the voltage of the energy storage unit 130 of the sub-converter module 100 is charged to the rated value, the precharge operation is completed, and the switch control module 200 disconnects the first connection terminal IN1 from the third connection terminal OUT1 and disconnects the second connection terminal IN2 from the fourth connection terminal OUT2, so that the converter device formed by the sub-converter module 100 operates normally.
Based on this, under the condition of the precharge requirement, the switch control module 200 conducts the connection between the first connection terminal IN1 and the third connection terminal OUT1 and the connection between the second connection terminal IN2 and the fourth connection terminal OUT2 of all the sub-converter modules 100, so that each sub-converter module 100 enters the precharge state, and conducts the unidirectional conduction devices (such as freewheeling diodes) IN the partial power semiconductor devices of the first full-bridge unit 110 and the second full-bridge unit 120 IN each sub-converter module 100, so that the energy storage units 130 IN all the sub-converter modules 100 are connected IN parallel, and are equivalent to equivalent capacitors with larger capacitance values and unchanged rated voltage values, thereby not only generating better current limiting effect, but also avoiding the use of large-volume and heavy current limiting resistors, and saving the layout space and cost of the devices.
The bridge arm circuit for converting current includes a plurality of cascaded sub-converter modules 100 and a switch control module 200, where the first full-bridge unit 110 and the second full-bridge unit 120 of each sub-converter module 100 are configured with dual connection ends, so that the energy storage units 130 of two adjacent sub-converter modules 100 can form a parallel structure, and under the circumstance of precharge requirement, the switch control module 200 conducts the connection between the first connection end IN1 and the third connection end OUT1 and the connection between the second connection end IN2 and the fourth connection end OUT2 of each sub-converter module 100, so that all sub-converter modules 100 are bypassed, and the energy storage units 130 of all sub-converter modules 100 form a parallel structure to be equivalent to an equivalent energy storage unit 130 with a larger capacity value, thereby greatly improving the current limiting effect, and realizing precharge of the energy storage units 130 of the plurality of sub-converter modules 100 without using a large-volume and heavy-weight current limiting resistor.
In one embodiment, as shown in fig. 2, the first full bridge cell 110 includes: the energy storage device comprises a first switch unit, a second switch unit, a third switch unit and a fourth switch unit, wherein the first switch unit is connected with the second switch unit in series to form a first branch, the third switch unit is connected with the fourth switch unit in series to form a second branch, and the first branch and the second branch are respectively connected with an energy storage unit C in parallel. The connection point between the first switch unit and the second switch unit is used as a first connection end IN1, and the connection point between the third switch unit and the fourth switch unit is used as a second connection end IN2.
The four switching units of the first full-bridge unit 110 are the power semiconductor devices described above, each switching unit includes a switching tube, and a diode connected in anti-parallel with the switching tube, where the switching tube may be understood as the power switching device described above, and the diode may be understood as the unidirectional conduction device described above, where the diode is used as a freewheeling diode, so that breakdown of the switching tube due to high voltage generated by abrupt turn-off may be avoided, and the switching tube may include elements with switching functions such as an IGBT and a MOSFET.
That is, the first switching unit includes a first switching tube Q1 and a first diode D1, the second switching unit includes a second switching tube Q2 and a second diode D2, the third switching unit includes a third switching tube Q3 and a third diode D3, and the fourth switching unit includes a fourth switching tube Q4 and a fourth diode D4. The collector of the first switching tube Q1 is respectively connected with the collector of the third switching tube Q3, one end of the energy storage unit C, and the cathode of the first diode D1, the emitter of the first switching tube Q1 is respectively connected with the collector of the second switching tube Q2 and the anode of the first diode D1, the connection point between the emitter of the first switching tube Q1 and the collector of the second switching tube Q2 is led out as the first connection end IN1, the emitter of the second switching tube Q2 is respectively connected with the emitter of the fourth switching tube Q4, the anode of the second diode D2, and the other end of the energy storage unit C, the emitter of the third switching tube Q3 is respectively connected with the anode of the third diode D3 and the collector of the fourth switching tube Q4, and the connection point between the emitter of the third switching tube Q3 and the collector of the fourth switching tube Q4 is led out as the second connection end IN2, and the collector of the third switching tube Q3 is connected with the cathode of the third diode D3.
In one embodiment, with continued reference to fig. 2, the second full bridge unit 120 includes: the fifth switching unit, the sixth switching unit, the seventh switching unit and the eighth switching unit are connected in series to form a third branch, the seventh switching unit is connected in series to the eighth switching unit to form a fourth branch, and the third branch and the fourth branch are respectively connected in parallel with the energy storage unit C. The connection point of the fifth switch unit and the sixth switch unit is used as a fourth connection end OUT2, and the connection point of the seventh switch unit and the eighth switch unit is used as a third connection end OUT1.
The fifth switching unit comprises a fifth switching tube Q5 and a fifth diode D5, the sixth switching unit comprises a sixth switching tube Q6 and a sixth diode D6, the seventh switching unit comprises a seventh switching tube Q7 and a seventh diode D7, and the eighth switching unit comprises an eighth switching tube Q8 and an eighth diode D8. The collector of the fifth switching tube Q5 is respectively connected with the collector of the third switching tube Q3, one end of the energy storage unit C and the negative electrode of the fifth diode D5, the emitter of the fifth switching tube Q5 is respectively connected with the collector of the sixth switching tube Q6 and the positive electrode of the fifth diode D5, a connection point between the emitter of the fifth switching tube Q5 and the collector of the sixth switching tube Q6 is led OUT to serve as a fourth connection end OUT2, the emitter of the sixth switching tube Q6 is respectively connected with the emitter of the fourth switching tube Q4, the positive electrode of the sixth diode D6, the emitter of the eighth switching tube Q8 and the other end of the energy storage unit C, the emitter of the seventh switching tube Q7 is respectively connected with the positive electrode of the seventh diode D7 and the collector of the eighth switching tube Q8, and a connection point between the emitter of the seventh switching tube Q7 and the collector of the eighth switching tube Q8 is led OUT to serve as a third connection end OUT1, and the collector of the eighth switching tube Q8 is connected with the negative electrode of the eighth diode D8.
Further, the bases of the first switching tube Q1 to the eighth switching tube Q8 can be connected with control signals, the control signals are used for controlling the on-off time of each switching tube, and then the voltages at the two ends of the energy storage unit C are controlled to realize the charge and discharge of the energy storage unit C. IN the precharge phase, each switching tube is controlled to be IN an off state, and the first diode D1, the seventh diode D7, the fourth diode D4 and the sixth diode D6 of each sub-converter module are turned on, if the first connection terminal IN1 of the first-stage sub-converter module is connected to the positive pole of the power supply voltage and the second connection terminal IN2 of the first-stage sub-converter module is connected to the negative pole of the power supply voltage, for the first-stage sub-converter module, current flows IN from the first connection terminal IN1 and sequentially passes through the first diode D1, the positive pole of the energy storage unit C, the negative pole of the energy storage unit C, the fourth diode D4 and the second connection terminal IN2, thereby realizing charging of the energy storage unit C of the first-stage sub-converter module.
For the first-stage sub-converter module and the next-stage sub-converter module, current flows IN from the first connection end IN1 of the first-stage sub-converter module, sequentially passes through the first diode D1, the seventh diode D7 and the third connection end OUT1 of the first-stage sub-converter module, then flows into the first connection end IN1, the first diode D1, the positive electrode of the energy storage unit C, the negative electrode of the energy storage unit C, the fourth diode D4 and the second connection end IN2 of the energy storage unit C, and current continues to flow into the fourth connection end OUT2 of the first-stage sub-converter module from the second connection end IN2 of the second-stage sub-converter module, and then flows through the sixth diode D6, the fourth diode D4 and the second connection end IN2 of the first-stage sub-converter module, so that the energy storage units C of the sub-converter modules can be connected together IN parallel for pre-charging based on two current loops of each sub-converter module.
In one embodiment, as shown in FIG. 2, the switch control module includes: the plurality of first bypass switch units 210 and the plurality of second bypass switch units 220, the plurality of first bypass switch units 210 are IN one-to-one correspondence with the plurality of sub-converter modules, one end of the first bypass switch unit 210 is connected to the first connection terminal IN1, and the other end of the first bypass switch unit 210 is connected to the third connection terminal OUT1. The plurality of second bypass switch units 220 are IN one-to-one correspondence with the plurality of sub-converter modules, one end of each second bypass switch unit 220 is connected to the second connection terminal IN2, and the other end of each second bypass switch unit 220 is connected to the fourth connection terminal OUT2.
The sub-converter modules are provided with a first bypass switch unit 210 and a second bypass switch unit 220, the first bypass switch unit 210 and the second bypass switch unit 220 are normally closed bypass switches, one end of the first bypass switch unit 210 is connected between an emitter of the first switch tube Q1 and a collector of the second switch tube Q2, the other end of the first bypass switch unit 210 is connected between an emitter of the seventh switch tube Q7 and a collector of the eighth switch tube Q8, one end of the second bypass switch unit 220 is connected between an emitter of the third switch tube Q3 and a collector of the fourth switch tube Q4, and the other end of the second bypass switch unit 220 is connected between an emitter of the fifth switch tube Q5 and a collector of the sixth switch tube Q6. Based on the above, in the pre-charging stage, the bypass switch units of each sub-converter module are not controlled to maintain a normally closed state, so that the sub-converter module is bypassed to enter a charging state, and when the sub-converter module fails, the bypass switch units of the sub-converter module are closed to remove the failed sub-converter module, thereby avoiding influencing the normal operation of the rest sub-converter modules of the bridge arm circuit, enabling the sub-converter module to enter the pre-charging state, and isolating the failed sub-converter module.
In one embodiment, a commutation apparatus is provided comprising a commutation bridge arm circuit as described above.
The converter device can be a modularized multi-level converter MMC, and can comprise a plurality of phase units, each phase unit is composed of an upper group of converter bridge arm circuits and a lower group of converter bridge arm circuits, and each converter bridge arm circuit can be connected with a reactor with small inductance in series, wherein the reactor is used for limiting interphase circulation and preventing current from rising when the converter device has a short circuit fault, so that the electronic device of the converter device is protected. By adjusting the serial number of the sub-converter modules in the bridge arm circuit, the flexible change of the output voltage and the power level of the converter device can be realized, and the extremely low switching frequency and the low harmonic content can be realized.
In one embodiment, as shown in fig. 3, the converter device further includes: the charging module 300 and the charging switch module 400, the charging module 300 is configured to provide a power supply voltage within a preset range to the plurality of cascaded sub-converter modules 100. The charging switch module 400 is disposed between the charging module 300 and the first-stage sub-converter module 100, and is configured to conduct connection between the charging module 300 and the first-stage sub-converter module 100 in case of a precharge requirement.
It will be appreciated that conventional current commutators typically draw power from an ac or dc side high voltage power grid at start-up, with a significant safety risk before steady state process is reached. Based on this, in this embodiment, the charging module 300 is configured to provide a low-voltage power supply to the bridge arm circuit of the converter, so as to ensure the safety of the converter during the precharge starting process. A corresponding charging module 300 may be disposed in each bridge arm circuit, and for a single bridge arm circuit, a charging switch module 400 is disposed between the charging module 300 and the first-stage sub-bridge module 100 to control the on-off states of the first connection end and the second connection end of the first-stage sub-bridge module 100 to the charging module 300. Therefore, in the precharge phase, the charge switch module 400 conducts the connection between the two connection ports of the first-stage sub-converter module 100 and the charge module 300, so that the charge module 300 provides the low-voltage supply voltage in the preset range to the converter bridge arm circuit, and the low-voltage precharge can be performed on each energy storage unit without using a high-voltage source, thereby ensuring the safety of the circuit operation.
In one embodiment, the charging module 300 includes: the direct current power supply unit 310 and the voltage conversion unit 320, the direct current power supply unit 310 is used for providing direct current input voltage, the voltage conversion unit 320 is connected with the direct current power supply unit 310, the positive power supply end of the voltage conversion unit 320 is connected with the first connection end of the first-stage sub-converter module 100, the negative power supply end of the voltage conversion unit 320 is connected with the second connection end of the first-stage sub-converter module 100, and the voltage conversion unit 320 is used for providing pre-charging voltage to the plurality of cascaded sub-converter modules 100 according to the direct current input voltage.
The charging switch module 400 may include two charging switches, where one end of the first charging switch is connected to the positive power supply end of the voltage conversion unit 320, the other end of the first charging switch is connected to the first connection end of the first stage sub-converter module 100, one end of the second charging switch is connected to the negative power supply end of the voltage conversion unit 320, and the other end of the second charging switch is connected to the second connection end of the first stage sub-converter module 100. The voltage conversion unit 320 may include a DC/DC converter for converting a fixed DC voltage output from the DC power supply unit 310 into an adjustable pre-charge voltage for outputting to the plurality of cascaded sub-converter modules 100 of the subsequent stage, where the DC/DC converter also has the characteristics of voltage stabilization, current stabilization, power control and DC line protection.
Further, please refer to fig. 3 and fig. 4 in combination, fig. 4 shows an equivalent circuit diagram of the bridge arm circuit in the precharge state. Since the impedance of the first bypass switch cell and the second bypass switch cell in the sub-converter module when closed is sufficiently small, the precharge equivalent circuit of the plurality of cascaded sub-converter modules 100 may ignore the impedance of the bypass switch cells. Therefore, when two charging switches in the charging switch module 400 are simultaneously closed and the first and second bypass switch units of each sub-converter module 100 are kept in the closed state, the first connection end and the third connection end in all the sub-converter modules 100 are equivalent to being directly connected to the positive power supply end of the voltage converting unit 320, and the second connection end and the fourth connection end in all the sub-converter modules 100 are equivalent to being directly connected to the negative power supply end of the voltage converting unit 320, so that current flows from the positive power supply end of the voltage converting unit 320 and passes through the first diode and the seventh diode, the fourth diode and the sixth diode of each sub-converter module 100, and the positive electrode and the negative electrode of the energy storing unit.
Taking the example of charging the energy storage unit in the second-stage sub-converter module 100, the current flows out from the positive power supply end of the voltage conversion unit 320, passes through the first diode and the seventh diode in the first-stage sub-converter module 100, and flows into the first connection end of the second-stage sub-converter module 100 from the third connection end of the first-stage sub-converter module 100, further passes through the first diode in the second-stage sub-converter module 100, the positive electrode and the negative electrode of the energy storage unit, and the fourth diode, then flows back to the fourth connection end of the first-stage sub-converter module 100 from the fourth diode of the second-stage sub-converter module 100, and finally flows into the negative power supply end of the voltage conversion unit from the second connection end of the first-stage sub-converter module 100, and at the same time, the energy storage unit of the first-stage sub-converter module 100 acquires the current flowing in from the first diode to charge, and then flows out from the energy storage unit to the fourth connection end, and then flows into the negative power supply end. Based on the current flow direction, the energy storage units of each sub-converter module 100 form a parallel structure in the precharge stage to form an equivalent energy storage device with a larger capacitance value, thereby greatly improving the current limiting effect of the converter bridge arm circuit. It should be noted that, the voltage drop when the diode is turned on is negligible compared with the rated voltage of the energy storage unit, so that the equivalent charging circuit may not be embodied.
In one embodiment, as shown in fig. 3, the converter device further includes an isolating switch module 500, where the isolating switch module 500 is connected to the first connection end and the second connection end of the first-stage sub-converter module 100, and to the third connection end and the fourth connection end of the last-stage sub-converter module 100, and the isolating switch module 500 is used to isolate the charging module 300 from an external circuit in the case where the plurality of cascaded sub-converter modules 100 are precharged.
Optionally, the isolation switch module 500 may include two sets of isolation switches to ensure that the bridge arm circuit is isolated from the external main power circuit when the commutation device is pre-charged. One group of isolating switches is connected to the first connection end and the second connection end of the first-stage sub-converter module 100, and the other group of isolating switches is connected to the third connection end and the fourth connection end of the last-stage sub-converter module 100. During the precharge phase, both sets of isolation switches of the isolation switch module 500 remain open, isolating the charge module 300 from the external power circuit.
In one embodiment, the converter device further includes a control module, as shown in fig. 5, where the control module is configured to obtain a predicted value of the precharge voltage according to the precharge voltage and the precharge current output by the last cycle of the voltage conversion unit and the equivalent capacitances of the plurality of cascaded sub-converter modules, so as to control the precharge voltage output by the next cycle of the voltage conversion unit according to the predicted value, where the equivalent capacitances are the sum of the capacitance values of the energy storage units of the plurality of sub-converter modules.
Wherein the control module is a model predictive control (Model Predictive Control, MPC) based controller, which is a mathematical model based advanced control method that translates control problemsTo optimize the problem, the behavior of the system in a future period of time is predicted by using a mathematical model of the system, and the optimization is performed according to the prediction result. Wherein, FIG. 5 showsAs the state quantity, the current state quantity,yin order to output the output of the device,ufor input, a prediction error is calculated by comparing the system output y with a reference value r, and the prediction model is corrected using the prediction error.
Further, the predictive control of the control module includes three parts of predictive model, feedback correction and rolling optimization, wherein in the derivation of the pre-charge model, please consider the output voltage of the voltage converting unit in combination with the pre-charge equivalent circuit diagram shown with reference to fig. 4u B (precharge voltage), precharge currenti L And the voltage of the energy storage unitu C Assume that the bridge arm circuit to be charged comprises N sub-converter modules, and the rated capacitance value of the energy storage unit is recorded asC 0 The equivalent capacitance value of the energy storage units of all the sub-converter modules connected in parallel is:Ceq=N*C 0 the differential equations expressed by the equivalent circuit are therefore respectively:u B =L*+u C ，i L = Ceq* substituting the two differential equations into the state space equation of the linear time-invariant system shown in fig. 5, so as to obtain the state space equation shown in the formula (1), and simplifying the problem of precharge control of the converter bridge arm circuit into the problem of voltage output control of the voltage conversion unit. +. >Representative ofu C Derivative of>Representative ofi L Is a derivative of (a).
- - -（1）
Further, on the basis of the above state space equation, a forward Euler method is applied to approximate differential element dx= [ x (k+1) -x (k)]/T S Deducing a discrete state space model directly used for MPC solving, and discretizing the result of the formula (1) as shown in the formula (2), wherein T S For the sampling period, the prediction model becomes:
- - -（2）
note that, L in the formula (2) represents an inductance value,u C (k)andi L (k)a measurement value representing the current sampling time, a corresponding value for the next sampling timeu C (k+1)Andi L (k+1)by selectingu B (k)Is predicted from the different values of (c).
Further, the method comprises the steps of,u B (k)since the control objective of the entire pre-charging process is to smoothly charge the energy storage cells of the sub-converter modules to their nominal values while avoiding that the pre-charging current is greater than a preset current value, the selection of (a) requires minimizing the objective function. Let the rated voltage of the energy storage unit of the sub-converter module beu Crated Taking tracking performance of a control module into consideration when designing an objective function, and integrating the objective functionJ y Defined as formula (3):
- - -（3）
wherein, the liquid crystal display device comprises a liquid crystal display device,pthe predicted length is indicated as such,kthe current point in time is indicated and,w i represent the firstiThe weights of the individual prediction steps are chosen,u C (k+i|k)represent the firstiPre-prediction of individual prediction stepsAnd measuring the voltage of the energy storage unit. The problem of controlling the voltage output by the voltage converting unit is rewritten into a typical form of the optimization problem: minimize Jy and enable i L < I max The expression is as follows:
min Jy
so thati L < I max
Wherein the method comprises the steps ofI max Is the maximum charging current threshold value (i.e. the preset current value as described above), and finally obtainedu B (k)The output of the control module is a PWM modulation signal as the output of the controller, and the PWM modulation signal is compared with a triangular carrier wave to directly generate a switching signal of the voltage conversion unit.
Therefore, the control module predicts the precharge current of one sampling time in the future and the voltage of the energy storage unit by selecting different precharge voltages output by the voltage conversion unit in a prediction model mode, minimizes the objective function by continuously selecting the precharge voltages output by the voltage conversion unit, namely, enables the precharge current to be smaller than or equal to a preset current value, and controls the energy storage unit to be smoothly charged to a rated voltage value, so that smooth black start precharge is realized, and compared with the traditional sub-module precharge strategy that the charge current is regulated by utilizing complex current control, the control logic of the black start precharge method based on model prediction control is simpler and more effective.
For example, let the simulation prediction length and the control length be 10 and 2, respectively, the energy storage unit is recorded as a capacitor in the example, the precharge control target is to charge the capacitor voltage to 2000V, meanwhile, the charging current is limited below 1500A, the optimal controller is solved by using the simulink model prediction control tool box, the simulation result is shown in fig. 6, fig. 6 shows dynamic changes of the capacitor voltage and the charging current in the precharge process, the starting procedure starts from t=0.01 s, the voltage of the capacitor stably rises, and no overshoot is generated after reaching the target value of 2000V. In addition, the charging current slightly fluctuates near the maximum value and then drops to zero after the start-up is completed, which means that the black start pre-charging is performed in a prediction model mode, so that the energy storage unit of the sub-converter module can be effectively and smoothly charged to the rated voltage, and the pre-charging current can be prevented from being larger than the preset current value in the charging process.
Further, referring to fig. 7, fig. 7 shows a change situation of a capacitor voltage in a transient process when the converter device is switched from a pre-charge state to a normal operation state, and the converter device enters the normal operation state at t=1s, which proves that the capacitor voltage can realize a smooth transition when the pre-charge is performed in a mode based on a prediction model.
In one embodiment, a precharge control method is provided, which is applied to a converter apparatus as described above, and includes the steps of: under the condition of precharge requirement, the control switch control module conducts connection between the first connection end and the third connection end of each sub-converter module in the plurality of cascaded sub-converter modules and connection between the second connection end and the fourth connection end so that a plurality of energy storage units corresponding to the plurality of sub-converter modules are connected in parallel and are in a precharge state.
In one embodiment, in case the converter device further comprises a charging module and a charging switch module, the precharge control method further comprises the steps of: under the condition of precharge requirement, the control charging switch module conducts connection between the charging module and the first connection end of the first-stage sub-converter module and conducts connection between the charging module and the second connection end of the first-stage sub-converter module.
In one embodiment, in the case that the charging module includes a dc power supply unit and a voltage conversion unit, the precharge control method further includes step S102 to step S104.
Step S102: and obtaining a predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit which are output by the last cycle of the voltage conversion unit.
Step S104: and controlling the precharge voltage output by the next period of the voltage conversion unit according to the predicted value.
In one embodiment, step S102 obtains a predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit output by the last cycle of the voltage conversion unit, and includes steps S202 to S206.
Step S202: and constructing a state space equation of the converter bridge arm circuit according to the precharge voltage, the precharge current and the voltage of the energy storage unit which are output in the last cycle of the voltage conversion unit.
Step S204: discretizing the state space equation to obtain a precharge prediction model.
Step S206: and carrying out optimization solving on the objective function based on the constraint condition to obtain a predicted value of the precharge voltage. The objective function is set according to a preset voltage value and a pre-charging voltage at a prediction time, and the constraint condition comprises that the pre-charging current is smaller than or equal to the preset current value.
In the embodiments of the precharge control method, reference is made to the related descriptions in the above embodiments, and the description is omitted herein.
Therefore, in the first aspect of the precharge control method, based on the condition of precharge requirement, the control switch control module is controlled to conduct the connection between the first connection end and the third connection end and the connection between the second connection end and the fourth connection end of each sub-converter module, so that all the sub-converter modules are bypassed, and the energy storage units of all the sub-converter modules form a parallel structure to be equivalent to equivalent energy storage units with larger capacity, so that the current limiting effect is greatly improved, and the precharge of the energy storage units of a plurality of sub-converter modules is realized without using a large-size and heavy-weight current limiting resistor. In the second aspect, in the precharge stage, the charge switch module is controlled to conduct connection between the two connection ports of the first-stage sub-converter module and the charge module, so that the charge module provides a low-voltage supply voltage in a preset range for the converter bridge arm circuit, and each energy storage unit can be precharged at a low voltage without using a high-voltage source, so that the operation safety of the circuit is ensured. In the third aspect, the converter device can adjust the charging current without using a complex current control method, smoothly charge the energy storage unit of the sub-converter module to the rated voltage based on a prediction model mode, and simultaneously can control the pre-charging current to be less than or equal to a preset current value, thereby realizing smooth black start pre-charging.
In one embodiment, a precharge control apparatus is provided, applied to a converter apparatus as described above, the precharge control method apparatus being for: under the condition of precharge requirement, the control switch control module conducts connection between the first connection end and the third connection end of each sub-converter module in the plurality of cascaded sub-converter modules and connection between the second connection end and the fourth connection end so that a plurality of energy storage units corresponding to the plurality of sub-converter modules are connected in parallel and are in a precharge state.
In one embodiment, in case the converter device further comprises a charging module and a charging switch module, the precharge control device is further configured to: under the condition of precharge requirement, the control charging switch module conducts connection between the charging module and the first connection end of the first-stage sub-converter module and conducts connection between the charging module and the second connection end of the first-stage sub-converter module.
In one embodiment, in case the charging module comprises a dc power supply unit and a voltage converting unit, the precharge control means is for: and obtaining a predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit which are output by the last cycle of the voltage conversion unit. And controlling the precharge voltage output by the next period of the voltage conversion unit according to the predicted value.
The embodiments of the precharge control apparatus provided above refer to the related descriptions in the above embodiments, and are not repeated here.
In one embodiment, a computer device is provided, including a memory having a computer program stored therein and a processor, which when executing the computer program performs the steps of the method embodiments described above.
In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, implements the steps of the method as described in the above embodiments.
In one embodiment, there is also provided a computer program product containing instructions which, when run on a computer, cause the computer to perform the steps of the method described in the above embodiments.
Any reference to memory, storage, database, or other medium used in the present application may include non-volatile and/or volatile memory. Suitable nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RM), which acts as external cache memory. By way of illustration and not limitation, RMs are available in a variety of forms, such as Static RMs (SRMs), dynamic RMs (DRMs), synchronous DRMs (SDRMs), double data rates SDRM (DDR SDRM), enhanced SDRMs (ESDRMs), synchronous link (synchronous) DRMs (SLDRMs), memory bus (Rmbus) direct RMs (RDRMs), direct memory bus dynamic RMs (DRDRMs), and memory bus dynamic RMs (RDRMs).
In the description of the present specification, reference to the terms "some embodiments," "other embodiments," "desired embodiments," and the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.
The technical features of the above embodiments may be arbitrarily combined, and for brevity, all of the possible combinations of the technical features of the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims (14)

1. A bridge converter circuit, comprising:
each sub-converter module comprises an energy storage unit, a first full-bridge unit and a second full-bridge unit which are arranged in parallel, wherein the first full-bridge unit is provided with a first connecting end and a second connecting end, the second full-bridge unit is provided with a third connecting end and a fourth connecting end, in the adjacent two stages of sub-converter modules, the first connecting end of the next-stage sub-converter module is connected with the third connecting end of the last-stage sub-converter module, the second connecting end of the next-stage sub-converter module is connected with the fourth connecting end of the last-stage sub-converter module, and the first connecting end and the second connecting end of the first-stage sub-converter module are both used for receiving power supply voltage;
the switch control module is used for conducting connection between the first connecting end and the third connecting end of each sub-converter module and connection between the second connecting end and the fourth connecting end of each sub-converter module under the condition of precharge requirement, so that a plurality of energy storage units corresponding to the sub-converter modules are connected in parallel and are in a precharge state.
2. The bridge leg circuit of claim 1, wherein the first full-bridge cell comprises: the energy storage device comprises a first switch unit, a second switch unit, a third switch unit and a fourth switch unit, wherein the first switch unit and the second switch unit are connected in series to form a first branch, the third switch unit and the fourth switch unit are connected in series to form a second branch, and the first branch and the second branch are respectively connected in parallel with the energy storage unit;
The connection point between the first switch unit and the second switch unit is used as the first connection end, and the connection point between the third switch unit and the fourth switch unit is used as the second connection end.
3. The bridge leg circuit of claim 2, wherein the second full-bridge cell comprises: a fifth switching unit, a sixth switching unit, a seventh switching unit and an eighth switching unit, wherein the fifth switching unit and the sixth switching unit are connected in series to form a third branch, the seventh switching unit and the eighth switching unit are connected in series to form a fourth branch, and the third branch and the fourth branch are respectively connected in parallel with the energy storage unit;
the connection point of the fifth switch unit and the sixth switch unit is used as the fourth connection end, and the connection point of the seventh switch unit and the eighth switch unit is used as the third connection end.
4. The bridge leg circuit of claim 3, wherein each switching unit comprises a switching tube, a diode antiparallel to the switching tube;
during the precharge process of the plurality of cascaded sub-converter modules, each switching tube is in an off state.
5. The bridge leg circuit of claim 1, wherein the switch control module comprises:
the plurality of first bypass switch units are in one-to-one correspondence with the plurality of sub-converter modules, one end of each first bypass switch unit is connected with the first connecting end, and the other end of each first bypass switch unit is connected with the third connecting end;
the plurality of second bypass switch units are in one-to-one correspondence with the plurality of sub-converter modules, one end of each second bypass switch unit is connected with the second connecting end, and the other end of each second bypass switch unit is connected with the fourth connecting end.
6. A converter device, comprising:
the bridge leg circuit of any one of claims 1 to 5.
7. The converter according to claim 6, further comprising:
the charging module is used for providing the power supply voltage within a preset range for the plurality of cascaded sub-converter modules;
and the charging switch module is arranged between the charging module and the first-stage sub-converter module and is used for conducting connection between the charging module and the first-stage sub-converter module under the condition of precharge requirement.
8. The converter of claim 7, wherein the charging module comprises:
a DC power supply unit for providing a DC input voltage;
the voltage conversion unit is connected with the direct current power supply unit, a positive power supply end of the voltage conversion unit is connected with a first connecting end of the first-stage sub-converter module, a negative power supply end of the voltage conversion unit is connected with a second connecting end of the first-stage sub-converter module, and the voltage conversion unit is used for providing precharge voltage for the plurality of cascaded sub-converter modules according to the direct current input voltage.
9. The converter according to claim 8, further comprising:
and the control module is used for acquiring a predicted value of the pre-charging voltage according to the pre-charging voltage, the pre-charging current and the voltage of the energy storage unit which are output in the last cycle of the voltage conversion unit, so as to control the pre-charging voltage output in the next cycle of the voltage conversion unit according to the predicted value.
10. The converter according to claim 7, further comprising:
the isolating switch module is connected with the first connecting end and the second connecting end of the first-stage sub-converter module and the third connecting end and the fourth connecting end of the last-stage sub-converter module, and is used for isolating the charging module from an external circuit under the condition that the plurality of cascaded sub-converter modules are precharged.
11. A precharge control method, applied to a converter apparatus according to any one of claims 6 to 10, comprising:
under the condition of precharge requirement, the control switch control module conducts connection between the first connection end and the third connection end of each sub-converter module in the plurality of cascaded sub-converter modules and connection between the second connection end and the fourth connection end, so that a plurality of energy storage units corresponding to the plurality of sub-converter modules are connected in parallel and are in a precharge state.
12. The precharge control method according to claim 11, wherein in the case where the converter apparatus further includes a charging module and a charging switch module, the precharge control method further includes:
under the condition of precharge requirement, the control charging switch module conducts connection between the charging module and the first connection end of the first-stage sub-converter module and conducts connection between the charging module and the second connection end of the first-stage sub-converter module.
13. The precharge control method according to claim 11, wherein in the case where the charging module includes a dc power supply unit and a voltage converting unit, the precharge control method further comprises:
Acquiring a predicted value of the precharge voltage according to the precharge voltage, the precharge current and the voltage of the energy storage unit which are output in a previous cycle of the voltage conversion unit;
and controlling the precharge voltage output by the next period of the voltage conversion unit according to the predicted value.
14. The precharge control method according to claim 13, wherein the obtaining of the predicted value of the precharge voltage based on the precharge voltage, the precharge current, and the voltage of the energy storage unit output at the previous cycle of the voltage conversion unit includes:
according to the precharge voltage, precharge current and voltage of the energy storage unit which are output in a previous period of the voltage conversion unit, a state space equation of a converter bridge arm circuit is constructed;
discretizing the state space equation to obtain a precharge prediction model;
based on constraint conditions, carrying out optimization solution on an objective function to obtain a predicted value of the precharge voltage;
the objective function is set according to a preset voltage value and a pre-charging voltage at a predicted time, and the constraint condition comprises that the pre-charging current is smaller than or equal to a preset current value.
CN202311197340.3A 2023-09-18 2023-09-18 Converter bridge arm circuit, converter device and precharge control method Active CN116937999B (en)

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