CN109921454B - Flexible direct current system starting method and device based on modular multilevel converter - Google Patents
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Abstract
The invention relates to a flexible direct current system starting method and a device based on a modular multilevel converter, wherein the method comprises the following steps: s1, after uncontrolled charging of the converter station is finished, a submodule for conducting the T2 tube is additionally arranged on each bridge arm at the same time, so that the number of submodules of a bypass is gradually increased, the remaining submodules are charged to the charging voltage threshold value through the voltage of the transformer valve side line, and dynamic voltage-sharing control of the submodules is executed under the condition that the total number of the submodules of the bypass of each bridge arm is kept unchanged; s2, when an unlocking instruction is received, stepping the direct-current voltage to a corresponding numerical value of a rated modulation ratio; and S3, after the direct current voltage is stabilized, the direct current voltage is ramped up to a direct current voltage instruction value, and the smooth starting of the flexible direct current system is realized. After the uncontrolled charging of the converter station is finished, the converter valve submodule can keep effective voltage sharing at any time interval, the moment of scheduling an unlocking instruction is not limited, and the problems of alternating current system impact and heavy harmonic caused by low direct current voltage at the initial stage of unlocking the converter station are effectively avoided.
Description
Technical Field
The invention relates to a flexible direct current system starting method and device based on a modular multilevel converter, and relates to the field of flexible direct current transmission.
Background
The flexible direct current system based on the modular multilevel converter is an important development direction of high-voltage large-capacity direct current transmission due to small harmonic distortion and low switching loss. The starting method of the flexible direct current system commonly used in engineering can be roughly divided into 4 steps: 1) alternating current incoming line breaker of fixed direct current voltage stationAnd switching on, and starting uncontrolled charging of the converter station through an alternating current side starting resistor. Taking the modular multilevel converter composed of the typical sub-modules shown in FIG. 1 as an example, when the voltage u on the valve side of the transformer isab>At 0, the uncontrolled charging loop of the inverter is shown in fig. 2; 2) the voltage at the valve side of the transformer is increased to be close to a rated value through gear shifting of the transformer, and the voltage of a direct current port of the converter station is continuously increased in the process; 3) if the voltage of the direct current port is larger than the uncontrolled charging ending threshold value, judging that uncontrolled charging is ended and bypassing the starting resistor; 4) according to the dispatching instruction, the station is unlocked in a constant direct-current voltage control mode, and the direct-current voltage set value is ramped up from the uncontrolled charging end threshold value to the direct-current voltage rated value; 5) and the fixed active power station completes the charging process by executing the steps 1) to 3), and is unlocked in a fixed active power control mode according to the scheduling instruction.
However, the above starting method has the following problems: 1) after uncontrolled charging of the converter station is finished, in the process of waiting for an unlocking instruction, the capacitance voltage of the sub-modules is easy to disperse, so that partial sub-modules are out of control due to overvoltage or undervoltage; 2) in the initial stage of unlocking of the converter station, the peak value of an alternating current bus of the converter station is low due to low direct-current voltage, so that the converter station absorbs a large amount of reactive power from an alternating current system to cause large disturbance to the alternating current system; 3) in the initial stage of unlocking of the converter station, the direct-current voltage is low, so that the voltage harmonic of the alternating-current bus of the converter station is heavy, and the oscillation of an alternating-current and direct-current system is easily caused.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method and an apparatus for starting a flexible dc system based on a modular multilevel converter, which can solve the problem of out-of-control caused by voltage divergence of sub-modules after the end of uncontrolled charging and the problem of ac system impact and heavy harmonic caused by low dc voltage at the initial stage of unlocking of a converter station.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for starting a flexible dc system based on a modular multilevel converter, where the method includes:
s1, after uncontrolled charging of the converter station is finished, simultaneously adding a new submodule for conducting the T2 tube for each bridge arm so as to gradually increase the number of the submodules of the bypass, enabling the remaining submodules to be charged to the charging voltage threshold value through the voltage of the transformer valve side line, and executing submodule dynamic voltage-sharing control under the condition of keeping the total number of the submodules of each bridge arm bypass unchanged, so that the voltages of all the submodules are kept at the charging voltage threshold value for a long time;
s2, when an unlocking instruction is received, stepping the direct-current voltage to a corresponding numerical value of a rated modulation ratio;
and S3, after the direct current voltage is stabilized, the direct current voltage is ramped up to a direct current voltage instruction value, and the smooth starting of the flexible direct current system is realized.
In some embodiments, the specific process of S1 is:
s11) switching on an alternating current incoming line breaker of the fixed direct current voltage control station, and starting uncontrolled charging through an alternating current side starting resistor in the converter station;
s12) shifting gears through the transformer to enable the voltage of the valve side of the transformer to rise to a set value, and meanwhile, the voltage of the direct current port of the converter station rises continuously;
s13) if the voltage of the direct current port is larger than or equal to the uncontrolled charging ending threshold, judging that uncontrolled charging is ended and issuing a closing instruction of a starting resistor bypass switch, and if the voltage of the direct current port is smaller than the uncontrolled charging ending threshold, executing S12);
s14) selecting k sub-modules with the highest voltage in each bridge arm every set time interval, and triggering T2 tubes of the corresponding sub-modules;
s15) total number of submodules k if each bridge arm triggers T2 tube<kmaxLet k be k +1, go to S14); otherwise go to S16);
s16) keeping the total number k of submodules of each bridge arm trigger T2 tubemaxKeeping the voltage of the T2 tube of the submodule with the lowest voltage, and triggering the T2 tube of the submodule with the highest voltage;
s17) performs steps S11) to S16) on the station to complete the charging process.
In some embodiments, the specific process of S2 is:
s21) after receiving the system unlocking instruction, setting the reference value U of the station fixed DC voltage controllerdcr＝MNReference value Q of the local station-fixed reactive power controllerrWhen equal to 0, then unlock the station, MNIs a rated modulation ratio;
s22) setting a reference value P for the standing active power controllerrReference value Q for standing reactive power controller2rAnd (5) unlocking the paired station, namely 0.
In some embodiments, the specific process of S3 is:
s31) is equal to U when the instantaneous value of the dc port voltage rises to meet the delta tdcrSetting a reference value U of the station-fixed DC voltage controllerdcrRamp up to a DC voltage command value UdcoThe voltage of the direct current port slowly rises, wherein delta t is a direct current voltage stabilization timing threshold;
s32) changing the control mode and reference value of the station and the opposite station according to the dispatching command.
In a second aspect, the present invention further provides a starting apparatus for a flexible dc system based on a modular multilevel converter, wherein the starting apparatus includes:
the collecting unit is used for collecting an effective value of the alternating current bus voltage of the converter station, an effective value of the transformer valve side voltage and an instantaneous value of the direct current port voltage;
the network side control unit is used for judging whether the effective value of the alternating current bus voltage of the converter station is in a steady-state voltage range or not, and issuing a switching-on instruction of an alternating current incoming line breaker and a 1-gear reduction instruction of a transformer on-load switch if the effective value of the alternating current bus voltage of the converter station is in the steady-state voltage range; then judging whether the effective value of the voltage on the valve side of the transformer reaches a set threshold value or not, if so, issuing a transformer gear adjustment finishing instruction, and if not, continuing issuing a 1-gear reduction instruction of the on-load switch of the transformer;
the valve side control unit is used for judging whether the voltage instantaneous value of the direct current port reaches a set threshold value or not according to the voltage instantaneous value of the direct current port, and issuing a switching-on instruction for starting the resistor bypass switch if the voltage instantaneous value of the direct current port reaches the set threshold value;
the charging control unit selects k sub-modules with the highest voltage in each bridge arm every set time interval, triggers the T2 tubes of the corresponding sub-modules, and then the counter executes k + 1;
a dynamic voltage-sharing control unit for judging whether the counter count reaches kmaxIf the voltage of the submodule reaches the preset voltage, the submodule with the highest voltage and the submodule with the lowest voltage are controlled, namely, a T2 tube of the submodule with the lowest voltage is sent with a locking signal, and then a T2 tube of the submodule with the highest voltage is sent with a triggering signal;
and the unlocking control unit is used for setting the instruction of the station controller after receiving the system unlocking instruction, so that the direct-current voltage, the active power and the reactive power smoothly rise to the instruction value.
Based on the technical scheme, the invention at least has the following technical effects: 1. after the uncontrolled charging of the converter station is finished, the converter valve submodule can keep effective voltage sharing at any time interval, and the moment of scheduling an unlocking instruction is not limited; 2. the starting method of the flexible direct current converter station can effectively avoid the problems of impact and heavy harmonic waves on an alternating current system at the moment of unlocking the converter station.
Drawings
FIG. 1 is a typical topology of sub-modules in a bridge arm of a modular multilevel converter;
FIG. 2 is a schematic diagram of an uncontrolled charging circuit of a prior art flexible direct current converter station;
FIG. 3 is a schematic diagram of the control device of the present invention;
FIG. 4 is a logic block diagram of the control method of the present invention;
fig. 5 is a schematic wiring diagram of a typical flexible dc system.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
For clarity, the present invention explains the definitions of the parameters:
submodule: a typical structure of a submodule in the prior art is shown in figure 1, a T1 tube and a T2 tube are respectively an upper IGBT (insulated gate bipolar transistor) and a lower IGBT (insulated gate bipolar transistor) of a submodule, a D1 tube and a D2 tube are respectively an upper diode and a lower diode of the submodule, and C is a submodule capacitor, wherein the T1 tube is connected with the capacitor C in series, anti-parallel diodes are arranged at two ends of a T1 tube and two ends of a T2 tube, and the average working voltage of the submodule is defined as UsmThe sub-module charging voltage threshold value proportionality coefficient is p, and the sub-module charging voltage threshold value Usmr＝pUsmThe total number of the sub-modules in each bridge arm is N, and the uncontrolled charging ending threshold value is UdcsRated modulation ratio of MN(ii) a The total number of the submodules of each bridge arm trigger T2 tube is k, the initial value is set to be 1, and the maximum value kmax＝N-Udcs/UsmrRounding down, the direct voltage stabilization timing threshold is delta t.
Uncontrolled charging: the modularized multi-level converter is in a locked state, a sub-module capacitor charging circuit is formed by closing an alternating current incoming line breaker, and an uncontrolled charging circuit is shown in figure 2.
The control mode is as follows: the working targets of the flexible direct current converter station controller comprise active power type and reactive power type control modes, wherein the active power type control modes comprise fixed direct current voltage control, fixed active power control and the like; the reactive power control method includes constant reactive power control, constant ac voltage control, and the like.
D, fixing a direct-current voltage station: the current active power control mode of the controller is a converter station controlled by constant direct current voltage.
In some embodiments, as shown in fig. 3, a flexible dc system starting apparatus based on a modular multilevel converter is provided, including an acquisition unit, a grid-side control unit, a valve-side control unit, a charging control unit, a dynamic voltage-sharing control unit, and an unlocking control unit, wherein:
the collecting unit is used for collecting the effective value of the alternating current bus voltage of the converter station, the effective value of the transformer valve side voltage and the instantaneous value of the direct current port voltage.
The network side control unit is used for judging whether the effective value of the alternating current bus voltage of the converter station is in a steady-state voltage range or not, and issuing an alternating current incoming line breaker closing instruction and a transformer on-load switch 1-gear reduction instruction if the effective value of the alternating current bus voltage of the converter station is in the steady-state voltage range; and then judging whether the effective value of the voltage on the valve side of the transformer reaches a set threshold value, if so, issuing a gear adjustment finishing instruction of the transformer, and if not, continuing issuing a gear 1 reduction instruction of the on-load switch of the transformer.
The valve side control unit is used for judging whether the voltage instantaneous value of the direct current port reaches a set threshold value or not according to the voltage instantaneous value of the direct current port, and issuing a switching-on instruction for starting the resistor bypass switch if the voltage instantaneous value of the direct current port reaches the set threshold value;
and the charging control unit selects k (the initial value is 1) sub-modules with the highest voltage in each bridge arm every set time interval, triggers the T2 tubes of the corresponding sub-modules, and then the counter executes k + 1.
The dynamic voltage-sharing control unit is used for judging whether the counting of the counter reaches kmaxAnd if the voltage of the submodule reaches the preset voltage, controlling the submodule with the highest voltage and the submodule with the lowest voltage, namely firstly sending a locking signal to a T2 tube of the submodule with the lowest voltage and then sending a trigger signal to a T2 tube of the submodule with the highest voltage.
And the unlocking control unit is used for setting the instruction of the station controller after receiving the system unlocking instruction, so that the direct-current voltage, the active power and the reactive power smoothly rise to the instruction value.
In some embodiments, as shown in fig. 4, a method for starting a flexible dc system based on a modular multilevel converter is further provided, where the method includes:
1. after uncontrolled charging of the converter station is finished, newly adding a submodule for conducting the T2 tube for each bridge arm so as to gradually increase the number of the submodules of the bypass, and charging the rest submodules to the charging voltage threshold value of the submodules through the voltage of the transformer valve side line; the submodule dynamic voltage-sharing control is executed under the condition that the total number of submodules of each bridge arm bypass is kept unchanged, so that the voltages of all submodules are kept at the charging voltage threshold value for a long time, and the specific process is as follows:
11) switching on an alternating current incoming line breaker of a constant direct current voltage control station, and starting uncontrolled charging by a converter station through an alternating current side starting resistor;
12) the voltage at the valve side of the transformer is increased to a set value through gear shifting of the transformer, and the voltage at a direct current port of the converter station is continuously increased in the process, wherein the set value is usually near the rated value of the voltage at the valve side of the transformer; and judging whether the voltage of the valve side of the transformer reaches a set threshold value or not according to the effective value of the voltage of the valve side of the transformer, issuing a gear adjustment ending instruction of the transformer if the voltage reaches the set threshold value, and continuing issuing a 1-gear reduction instruction of the on-load switch of the transformer if the voltage does not reach the set threshold value.
13) If the voltage of the direct current port is larger than or equal to the uncontrolled charging ending threshold value, judging that uncontrolled charging is ended and issuing a switching-on instruction for starting a resistor bypass switch, otherwise, if the voltage of the direct current port is smaller than the uncontrolled charging ending threshold value, executing 12);
14) sequencing the voltage of the submodules, selecting k submodules with the highest voltage in each bridge arm every set time interval, and triggering T2 tubes of the corresponding submodules;
15) if each bridge arm triggers the total number k of submodules of the T2 tube<kmaxLet k be k +1, execute 14); otherwise 16) is performed, where k is passedmaxThe setting of (2) ensures that the remaining sub-modules are charged to their charging voltage threshold;
16) keep the total number of submodules k of each bridge arm trigger T2 tubemaxKeeping the voltage of the T2 tube of the submodule with the lowest voltage, and triggering the T2 tube of the submodule with the highest voltage;
17) similarly, the charging process is completed by carrying out steps 11) to 16) again on the station;
2. when receiving the unblock instruction, with direct current voltage step to rated modulation ratio corresponding numerical value for through the undistorted high voltage of transverter output ac system impact and heavy harmonic problem have been avoided, specific process is:
21) after receiving a system unlocking instruction, setting a reference value U of the fixed direct current voltage controller of the stationdcr＝MNReference value Q of the local station-fixed reactive power controllerrWhen the station is not changed to 0, then unlocking the station;
22) setting a reference value P for a standing active power controllerrReference value Q for standing reactive power controller2rThe docking station is then unlocked 0.
3. And ramping the direct-current voltage to a direct-current voltage instruction value to realize smooth starting of the flexible direct-current system.
31) Equal to U when the instantaneous value step of the DC port voltage rises to meet the time period of delta tdcrSetting a reference value U of the station-fixed DC voltage controllerdcrRamp up to a DC voltage command value UdcoThe dc port voltage rises slowly.
32) And changing the control modes and reference values of the local station and the opposite station according to the scheduling instruction.
In some embodiments, the detailed description will further explain a starting method of the flexible dc system based on the modular multilevel converter by taking the terminal-terminal flexible dc system as shown in fig. 5 as an example: the flexible direct current system adopts symmetrical single-pole wiring. The station 1 adopts constant direct-current voltage and constant reactive power control, and the station 2 adopts constant active power and constant reactive power control. Rated direct current port voltage of +/-420 kV and rated modulation ratio MN0.85. The transformer transformation ratio was 525(+ 11/-2). times.1.25% kV/437.23 kV. Mean operating voltage U of submodulesm1.68kV, submodule charging voltage threshold Usmr1.65kV, the total number N of the submodules in each bridge arm is 540 (including redundancy), and an uncontrolled charging end threshold value U is adopteddcsThe dc voltage stabilization timing threshold is set to 420kV and Δ t is set to 100 ms. Before the flexible direct current system is started, the voltage of alternating current buses of two stations is 540kV, the initial gears of transformers of the two stations are 11 gears, and a direct current voltage instruction value U is dispatched and issueddco1.0 pu. The total number of the submodules of each bridge arm trigger T2 tube is k, an initial value is set to be 1, and k is obtained through calculationmax285, the starting method of the flexible direct current system based on the setting comprises the following steps:
1) the station 1 alternating current incoming line breaker is switched on, the two stations start uncontrolled charging through the starting resistor at the alternating current side of the station 1, and the gear of the transformer of the station 1 is gradually reduced from 11.
2) When the gear of the transformer in the station 1 is adjusted to the gear 2, the voltage on the valve side of the transformer rises to 435kV, and the gear shifting is finished; the dc port voltage rises continuously in this process.
3) And when the voltage of the direct-current port of the station 1 is greater than the uncontrolled charging end threshold value 420kV, the switch-on station 1 starts a resistance bypass switch.
4) And selecting the k sub-modules with the highest voltage in each bridge arm every fixed time interval by the station 1, and triggering the T2 tubes of the sub-modules.
5) If the total number k of submodules of each bridge arm of the station 1 triggering the T2 tube is less than 285, making k equal to k +1, and executing 4); otherwise 6) is executed;
6) keeping the total number k of submodules of the T2 triggering tubes of each bridge arm unchanged, and executing submodule dynamic voltage-sharing control in each control period of each bridge arm, namely selecting the submodule with the highest voltage and the submodule with the lowest voltage, firstly locking the T2 tube of the submodule with the lowest voltage, and then triggering the T2 tube of the submodule with the highest voltage.
7) Similarly, the station 2 completes the charging process by performing steps 1) to 6).
8) After receiving a system unlocking instruction, setting a reference value U of a fixed direct-current voltage controller of the station 1dcr0.85, reference value Q of the constant reactive power controllerr0; the station 1 is then unlocked and the dc port voltage rapidly steps up.
9) Setting station 2 decides reference value P of active power controllerrDetermining the reference value Q of the reactive power controller as 02r0; and then unlock station 2.
10) When the instantaneous voltage value of the DC port of the station 1 rises to 100ms continuously, the voltage value is equal to UdcrThen, the station 1 is used for determining the reference value U of the DC voltage controllerdcrFrom 0.85 to U with a slope of 1pu/mindcrWhen the dc port voltage is 1.0, the dc port voltage rises slowly.
11) And changing the control mode and the reference value according to the scheduling instruction.
The above-described embodiments are merely illustrative of the present invention, and various steps may be varied, as will be apparent to those skilled in the art, and embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the scope of protection thereof, and although the present application is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: numerous variations, modifications, and equivalents will occur to those skilled in the art upon reading the present application and are within the scope of the claims appended hereto.
Claims (4)
1. A flexible direct current system starting method based on a modular multilevel converter is characterized by comprising the following steps:
s1, after uncontrolled charging of the converter station is finished, simultaneously adding a new submodule for conducting the T2 tube for each bridge arm so as to gradually increase the number of submodules of the bypass, enabling the remaining submodules to be charged to the charging voltage threshold value through the voltage of the transformer valve side line, executing submodule dynamic voltage-sharing control under the condition of keeping the total number of the submodules of each bridge arm bypass unchanged, and enabling all the submodule voltages to be kept at the charging voltage threshold value for a long time, wherein the specific process is as follows:
s11) switching on an alternating current incoming line breaker of the fixed direct current voltage control station, and starting uncontrolled charging through an alternating current side starting resistor in the converter station;
s12) shifting gears through the transformer to enable the voltage of the valve side of the transformer to rise to a set value, and meanwhile, the voltage of the direct current port of the converter station rises continuously;
s13) if the voltage of the direct current port is larger than or equal to the uncontrolled charging ending threshold, judging that uncontrolled charging is ended and issuing a closing instruction of a starting resistor bypass switch, and if the voltage of the direct current port is smaller than the uncontrolled charging ending threshold, executing S12);
s14) selecting k sub-modules with the highest voltage in each bridge arm every set time interval, and triggering T2 tubes of the corresponding sub-modules;
s15) total number of submodules k if each bridge arm triggers T2 tube<kmaxLet k be k +1, go to S14); otherwise go to S16);
s16) keeping the total number k of submodules of each bridge arm trigger T2 tubemaxKeeping the voltage of the T2 tube of the submodule with the lowest voltage, and triggering the T2 tube of the submodule with the highest voltage;
s17) executing steps S11) to S16) to complete the charging process; s2, when an unlocking instruction is received, stepping the direct-current voltage to a corresponding numerical value of a rated modulation ratio;
s3, after the direct current voltage is stabilized, the direct current voltage is ramped up to a direct current voltage instruction value, and smooth starting of the flexible direct current system is achieved;
the T2 tube is a lower insulated gate bipolar transistor of a submodule of a modular multilevel converter bridge arm.
2. The method according to claim 1, wherein the specific process of S2 is as follows:
s21) after receiving the system unlocking instruction, setting the reference value U of the station fixed DC voltage controllerdcr＝MNReference value Q of the local station-fixed reactive power controllerrWhen equal to 0, then unlock the station, MNIs a rated modulation ratio;
s22) setting a reference value P for the standing active power controllerrReference value Q for standing reactive power controller2rAnd (5) unlocking the paired station, namely 0.
3. The method according to claim 1 or 2, wherein the specific process of S3 is:
s31) is equal to U when the instantaneous value of the dc port voltage rises to meet the delta tdcrSetting a reference value U of the station-fixed DC voltage controllerdcrRamp up toCurrent voltage command value UdcoThe voltage of the direct current port slowly rises, wherein delta t is a direct current voltage stabilization timing threshold;
s32) changing the control mode and reference value of the station and the opposite station according to the dispatching command.
4. A flexible direct current system starting device based on a modular multilevel converter is characterized by comprising:
the collecting unit is used for collecting an effective value of the alternating current bus voltage of the converter station, an effective value of the transformer valve side voltage and an instantaneous value of the direct current port voltage;
the network side control unit is used for judging whether the effective value of the alternating current bus voltage of the converter station is in a steady-state voltage range or not, and issuing a switching-on instruction of an alternating current incoming line breaker and a 1-gear reduction instruction of a transformer on-load switch if the effective value of the alternating current bus voltage of the converter station is in the steady-state voltage range; then judging whether the effective value of the voltage on the valve side of the transformer reaches a set threshold value or not, if so, issuing a transformer gear adjustment finishing instruction, and if not, continuing issuing a 1-gear reduction instruction of the on-load switch of the transformer;
the valve side control unit is used for judging whether the voltage instantaneous value of the direct current port reaches a set threshold value or not according to the voltage instantaneous value of the direct current port, and issuing a switching-on instruction for starting the resistor bypass switch if the voltage instantaneous value of the direct current port reaches the set threshold value;
the charging control unit selects k sub-modules with the highest voltage in each bridge arm every set time interval, triggers the T2 tubes of the corresponding sub-modules, and then the counter executes k + 1;
a dynamic voltage-sharing control unit for judging whether the counter count reaches kmaxIf the voltage of the submodule reaches the preset voltage, the submodule with the highest voltage and the submodule with the lowest voltage are controlled, namely, a T2 tube of the submodule with the lowest voltage is sent with a locking signal, and then a T2 tube of the submodule with the highest voltage is sent with a triggering signal;
the unlocking control unit is used for setting a controller command of the controller after receiving a system unlocking command, so that the direct-current voltage, the active power and the reactive power smoothly rise to a command value;
the T2 tube is a lower insulated gate bipolar transistor of a submodule of a modular multilevel converter bridge arm.
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| CN112165245A (en) * | 2020-07-31 | 2021-01-01 | 国电南瑞科技股份有限公司 | MMC converter starting method and system |
| CN112086989B (en) * | 2020-08-26 | 2022-07-01 | 东南大学 | Power electronic equipment control initialization method |
| CN112769119B (en) * | 2021-02-26 | 2022-08-23 | 国网江苏省电力有限公司电力科学研究院 | Interconnection operation control method and system for true and false bipolar direct current conversion equipment |
| CN114167278B (en) * | 2022-02-11 | 2022-05-17 | 华北电力科学研究院有限责任公司 | Flexible direct-current transmission voltage source converter valve test method and power supply device |
| CN115603434B (en) * | 2022-09-26 | 2023-05-16 | 国网河南省电力公司济源供电公司 | Non-inductive charging system of electric automobile |
| CN115514019B (en) * | 2022-10-13 | 2023-05-16 | 国家电网有限公司 | Large-load test control method and system for new energy sent out by flexible direct current |
| CN115940243B (en) * | 2022-11-29 | 2024-04-02 | 中国南方电网有限责任公司超高压输电公司广州局 | Charging sequence control method and device for extra-high voltage flexible direct current converter station |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102170140A (en) * | 2011-04-21 | 2011-08-31 | 中国电力科学研究院 | Method for starting flexible high-voltage direct-current (HVDC) system of modularized multi-level converter |
| CN104242333A (en) * | 2014-09-19 | 2014-12-24 | 华南理工大学 | Self-excited starting method for modular multilevel inverter flexible direct current transmission system |
| CN105680681A (en) * | 2016-02-16 | 2016-06-15 | 南方电网科学研究院有限责任公司 | Clamping type single submodule-based starting method of modular multilevel converter |
| CN106786910A (en) * | 2016-12-27 | 2017-05-31 | 中国西电电气股份有限公司 | It is a kind of at the same suitable for MMC converter valve submodules alternating current-direct current charge method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108988631B (en) * | 2017-05-30 | 2024-05-14 | 日立能源有限公司 | Converter cell with integrated photovoltaic cells |
| ES2717345A1 (en) * | 2017-12-20 | 2019-06-20 | Power Electronics Espana S L | POWER CONVERTER WITH STARTING IN COLD AND METHOD OF STARTING IN COLD FOR THE POWER CONVERTER (Machine-translation by Google Translate, not legally binding) |
-
2019
- 2019-04-17 CN CN201910307782.6A patent/CN109921454B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102170140A (en) * | 2011-04-21 | 2011-08-31 | 中国电力科学研究院 | Method for starting flexible high-voltage direct-current (HVDC) system of modularized multi-level converter |
| CN104242333A (en) * | 2014-09-19 | 2014-12-24 | 华南理工大学 | Self-excited starting method for modular multilevel inverter flexible direct current transmission system |
| CN105680681A (en) * | 2016-02-16 | 2016-06-15 | 南方电网科学研究院有限责任公司 | Clamping type single submodule-based starting method of modular multilevel converter |
| CN106786910A (en) * | 2016-12-27 | 2017-05-31 | 中国西电电气股份有限公司 | It is a kind of at the same suitable for MMC converter valve submodules alternating current-direct current charge method |
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