CN105939101A - MMC system soft-start grid-connected method for flexible direct-current transmission - Google Patents
MMC system soft-start grid-connected method for flexible direct-current transmission Download PDFInfo
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- CN105939101A CN105939101A CN201610141442.7A CN201610141442A CN105939101A CN 105939101 A CN105939101 A CN 105939101A CN 201610141442 A CN201610141442 A CN 201610141442A CN 105939101 A CN105939101 A CN 105939101A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses an MMC system soft-start grid-connected method for flexible direct-current transmission. The method comprises the following steps: setting an MMC converter valve control mode to be a direct-current voltage balance control mode; turning off an alternating-current side power supply switch, precharging a capacitor of an SM submodule, and enabling an MMC converter valve to be under a locking condition; issuing an unlocking command, and continuously charging the capacitor of the SM submodule; when the direct-current voltage of the SM submodule reaches a steady state, issuing a locking command, and then bypassing a charging resistor; issuing un unlocking command so that a soft-start control strategy starts, and slowly raising direct-current bus side voltage at a rated value, so that the whole start process of the single-ended MMC converter valve is completed; charging an MMC converter valve at the other end according to the above steps, wherein the steps can be performed at the same time. Through the adoption of start logic of the method, under the precondition that grid-connected impact current is maintained to be smaller than rated current, the charging resistance value can be greatly improved, the charging current can be greatly reduced, and the resistor power and size are greatly reduced.
Description
Technical field
The present invention relates to the MMC system soft start combination method of a kind of flexible DC power transmission.
Background technology
Modular multilevel converter valve MMC(modular multilevel conventer) as a kind of Novel electric potential source type converter valve VSC(voltage source conventer), it is successfully applied in flexible direct current power transmission system.
MMC topological structure sees 1, is made up of six brachium pontis, and the most each brachium pontis is connected with each other and submodule SM and a reactor L that structure is identical are in series by N number of, and upper and lower two brachium pontis of homophase constitute a facies unit.Six brachium pontis have symmetry, and parameter and each brachium pontis reactance value of the most each submodule are all identical.The structure of one of them submodule SM sees Fig. 2, and 1) blocking: V1, V2 are turned off, and electric current is flowed to A by B through D2, be equivalent to short circuit, or flowed to B by A through D1, C between A, B, and capacitor charges, and time properly functioning, does not allows this state occur；2) putting into state: V1 is open-minded, V2 ends.Electric current is flowed to A by B through C, V1, and module capacitors is discharged, or is flowed to B by A through D1, C, and capacitor charges, and now between A, B, voltage is condenser voltage；3) bypass condition: V2 is open-minded, V1 ends, and electric current is flowed to A by B through D2, or flowed to B by A through V2, and now between A, B, voltage is only the forward voltage drop of D2 or V2, and almost 0.By the switching of on off state, the control to SM output voltage can be realized.Quick side way switch KM, fault SM when quickly excision SM fault, so that converter valve can work in brownout operation state without causing power-off.IGCT V3, for when system generation dc-side short-circuit fault, shunts the electric current of IGBT module anti-paralleled diode before AC chopper disconnects, and reduces the probability that diode damages, and improves system reliability.
Fig. 3 is the flexible direct current power transmission system of a kind of two level topological structures, and its left and right side structure is identical, includes alternating current power supply, cable, transformator, charging resistor, inductance, current conversion station respectively, and described current conversion station uses MMC converter valve；Connect between its left and right side current conversion station and have dc bus.
In common engineering application, MMC charge initiation process is: band charging resistor carries out being pre-charged (SM is in blocking), then bypass resistance, owing to removing electric resistance partial pressure, MMC charging voltage can be further continued for rising a bit, directly opens pulse and lift vertical compression to rated voltage after reaching stable state.Dash current during for guaranteeing to bypass charging resistor can not be excessive must be requested that electric resistance partial pressure (resistance) is the smaller the better, and common engineering application chooses resistance for ensureing that charging current is close to rated current.The charging resistor power consumption under net side rated voltage so can be brought big, cause that resistance volume is excessive, cost increase and the problems such as installation floor space is excessive.
Summary of the invention
For overcoming the deficiencies in the prior art, it is an object of the invention to provide the MMC system soft start combination method of a kind of flexible DC power transmission, while charging resistor cost and volume can be greatly reduced, in the case of bigger pressure reduction grid-connected, dash current can be in tolerance range in system, even up to zero impact, there is the strongest adaptability.
The present invention solves that its technical problem the technical scheme is that
The MMC system soft start combination method of a kind of flexible DC power transmission, said method comprising the steps of:
A.MMC converter valve control model is set to voltage balance control pattern；
B. Guan Bi AC on and off switch, is pre-charged the electric capacity of SM submodule by charging resistor, and this stage MMC converter valve is in blocking；
C. issuing unblock instruction, the electric capacity of SM submodule continues charging；
When the DC voltage of d.SM submodule reaches stable state, issue blocking order, then bypass charging resistor；
E. issuing unblock instruction, soft start control strategy starts, and dc bus side voltage will slowly be raised to rated value, and the most single-ended whole start-up course of MMC converter valve is complete；
F. other end MMC converter valve is charged according to above-mentioned steps, it is possible to carry out simultaneously；
G., after MMC converter valve in two ends is incorporated into the power networks, it is switched to corresponding control model, then closes dc bus switch；
The most so far, whole MMC system start-up is complete.
Further, the resistance that described charging resistor uses resistance to be 500 ohm to 1000 ohm.
Further, in step d, between DC voltage and the rated voltage when DC voltage of SM submodule reaches stable state, also has gap.
Further, in step e, described soft start control strategy is specifically: the grid-connected moment after bypassing charging resistor, current inner loop and outer voltage control strategy function to, outer voltage be given as current DC voltage, then certain sequential is used to make voltage slowly be risen to rated value by outer shroud set-point, it is achieved whole soft start-up process is stablized controlled.
The invention has the beneficial effects as follows:
1. charging resistor resistance can choose bigger resistance according to actual condition, and resistance volume and cost can be greatly reduced；
2. use soft start control strategy, it is ensured that dash current can be in tolerance range in system when big pressure reduction is grid-connected；
3. MMC module zero is impacted by charge initiation process, is greatly prolonged the power electric component life-span.
Accompanying drawing explanation
Below in conjunction with accompanying drawing and example, the invention will be further described.
Fig. 1 is the topological structure of modularization multi-level converter MMC；
Fig. 2 is the topological structure of the submodule SM in modularization multi-level converter MMC；
Fig. 3 is the flexible direct current power transmission system of two level topological structures；
Fig. 4 is MMC flexible direct-current transmission system phantom structure chart based on PSIM；
Fig. 5 is the simulation result oscillogram of MMC flexible direct-current transmission system based on PSIM；
Fig. 6 is the oscillogram of RT-LAB dynamic analog test one；
Fig. 7 is the oscillogram of RT-LAB dynamic analog test two；
Fig. 8 is the oscillogram of RT-LAB dynamic analog test three.
Detailed description of the invention
The MMC system soft start combination method of a kind of flexible DC power transmission of the present invention, said method comprising the steps of:
A.MMC converter valve control model is set to voltage balance control pattern；
B. Guan Bi AC on and off switch, is pre-charged the electric capacity of SM submodule by charging resistor, and this stage MMC converter valve is in blocking；
C. issuing unblock instruction, the electric capacity of SM submodule continues charging；
When the DC voltage of d.SM submodule reaches stable state, also have gap between DC voltage and rated voltage, now issue blocking order, then bypass charging resistor；
E. issuing unblock instruction, soft start control strategy starts, and dc bus side voltage will slowly be raised to rated value, and the most single-ended whole start-up course of MMC converter valve is complete；
F. other end MMC converter valve is charged according to above-mentioned steps, it is possible to carry out simultaneously；
G., after MMC converter valve in two ends is incorporated into the power networks, it is switched to corresponding control model, then closes dc bus switch；
The most so far, whole MMC system start-up is complete.
Owing to the resistance of charging resistor is bigger, bypass charging resistor after grid-connected time pressure reduction bigger, it is very easy to cause heavy current impact, so a kind of effective control strategy must be used to avoid impact, this patent have employed soft start control strategy, it is possible to grid-connected in the case of bigger pressure reduction reaches the least dash current.The grid-connected moment after bypassing charging resistor, current inner loop and outer voltage control strategy function to, outer voltage be given as current DC voltage, then use certain sequential to make voltage slowly be risen to rated value by outer shroud set-point, it is achieved whole soft start-up process is stablized controlled.
Use the startup logic of this method, on the premise of keeping grid-connected dash current less than rated current, be greatly improved charging resistor resistance, reduce charging current, significantly reduce resistor power and volume.Whole start-up course smooths controlled.Wherein, described charging resistor preferably employs the resistance that resistance is 500 ohm to 1000 ohm.
With reference to Fig. 4, we build MMC flexible direct-current transmission of electricity analogue system on PSIM simulation system software, as a example by 10kV, and have done a series of emulation for big resistance charge initiation.Oversize owing to reaching steady state time when big resistance charges, for accelerating simulation time, choosing charging resistor is 600 ohm.From simulation result, MMC starts grid-connected employing this patent and also is able to reach the grid-connected dash current effect of little charging resistor.
With reference to Fig. 5, simulation parameter is: net side rated voltage is 10kV, and charging resistor is 600 ohm, 10 submodule SM of single brachium pontis, and system nominal capacity is 2MW, and the specified vertical compression of dc bus is 20kVDC.Simulation process is: be precharged to 0.8s, issues unlocking signal lifting vertical compression, to 1.5s locking.1.6s bypasses charging resistor, and 1.7s issues unlocking signal, and now dash current peak value reaches about 250A, opens soft start logic strategy, and 2.5s soft start policy terminates, and the grid-connected flow process of whole startup completes, and dc bus vertical compression is stable at 20000VDC.
We have also built a set of flexible DC power transmission MMC switch board and have done RT-LAB dynamic analog test, 10 submodule SM of the single brachium pontis of converter valve, submodule SM rated voltage is 2000V, the total vertical compression of dc bus is 20000V, voltage on line side is 10kv, demonstrates 30 Europe resistance and 1000 Europe resistance use soft mode of this patent and several startups using direct grid-connected mode network process.
With reference to Fig. 6, test one employing this method soft starting mode, 1K Ω charging resistor, dash current is 200A；With reference to Fig. 7, test two employing direct join net mode, 1K Ω charging resistor, dash current is 900A；With reference to Fig. 8, test three employing direct join net mode, 30 Ω charging resistors, dash current is 400A.Three result of the tests show, use this method Starting mode that dash current also can be greatly reduced during big resistance.
The above, simply presently preferred embodiments of the present invention, the invention is not limited in above-mentioned embodiment, as long as it reaches the technique effect of the present invention with identical means, all should belong to protection scope of the present invention.
Claims (4)
1. the MMC system soft start combination method of a flexible DC power transmission, it is characterised in that said method comprising the steps of:
MMC converter valve control model is set to voltage balance control pattern；
Guan Bi AC on and off switch, is pre-charged the electric capacity of SM submodule by charging resistor, and this stage MMC converter valve is in blocking；
Issuing unblock instruction, the electric capacity of SM submodule continues charging；
When the DC voltage of SM submodule reaches stable state, issue blocking order, then bypass charging resistor；
Issuing unblock instruction, soft start control strategy starts, and dc bus side voltage will slowly be raised to rated value, and the most single-ended whole start-up course of MMC converter valve is complete；
Other end MMC converter valve is charged according to above-mentioned steps, it is possible to carry out simultaneously；
After two ends MMC converter valve is incorporated into the power networks, it is switched to corresponding control model, then closes dc bus switch；
So far, whole MMC system start-up is complete.
The MMC system soft start combination method of a kind of flexible DC power transmission the most according to claim 1, it is characterised in that the resistance that described charging resistor uses resistance to be 500 ohm to 1000 ohm.
The MMC system soft start combination method of a kind of flexible DC power transmission the most according to claim 1, it is characterised in that in step d, also has gap between DC voltage and the rated voltage when DC voltage of SM submodule reaches stable state.
The MMC system soft start combination method of a kind of flexible DC power transmission the most according to claim 1, it is characterized in that, in step e, described soft start control strategy is specifically: the grid-connected moment after bypassing charging resistor, current inner loop and outer voltage control strategy function to, outer voltage be given as current DC voltage, then use certain sequential to make voltage slowly be risen to rated value by outer shroud set-point, it is achieved whole soft start-up process is stablized controlled.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610141442.7A CN105939101A (en) | 2016-03-11 | 2016-03-11 | MMC system soft-start grid-connected method for flexible direct-current transmission |
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| CN201610141442.7A CN105939101A (en) | 2016-03-11 | 2016-03-11 | MMC system soft-start grid-connected method for flexible direct-current transmission |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN108279378A (en) * | 2017-12-29 | 2018-07-13 | 中电普瑞电力工程有限公司 | A kind of steady state test device and method of modular multilevel converter valve |
| CN111211677A (en) * | 2020-02-19 | 2020-05-29 | 南京工程学院 | Direct-current fault quick restart method of MMC type multi-port solid-state transformer |
| CN112583244A (en) * | 2019-09-29 | 2021-03-30 | 国创新能源汽车能源与信息创新中心(江苏)有限公司 | Voltage-sharing control device and method for direct-current bus capacitor of power electronic transformer system |
| CN115047333A (en) * | 2022-08-11 | 2022-09-13 | 国网经济技术研究院有限公司 | Passive unlocking test method and system for offshore platform converter valve wharf |
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| CN102769289A (en) * | 2012-07-17 | 2012-11-07 | 华北电力大学 | Three-phase unified power quality conditioner (UPQC) topological circuit based on modular multilevel converter (MMC) and pre-charging method of three-phase UPQC topological circuit |
| CN104734484A (en) * | 2014-11-24 | 2015-06-24 | 许继电气股份有限公司 | Simple starting method for clamp double sub-module modular multilevel converter |
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2016
- 2016-03-11 CN CN201610141442.7A patent/CN105939101A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102769289A (en) * | 2012-07-17 | 2012-11-07 | 华北电力大学 | Three-phase unified power quality conditioner (UPQC) topological circuit based on modular multilevel converter (MMC) and pre-charging method of three-phase UPQC topological circuit |
| CN104734484A (en) * | 2014-11-24 | 2015-06-24 | 许继电气股份有限公司 | Simple starting method for clamp double sub-module modular multilevel converter |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN106786910B (en) * | 2016-12-27 | 2019-12-27 | 中国西电电气股份有限公司 | Method simultaneously suitable for AC/DC charging of submodule of MMC converter valve |
| CN108279378A (en) * | 2017-12-29 | 2018-07-13 | 中电普瑞电力工程有限公司 | A kind of steady state test device and method of modular multilevel converter valve |
| CN108279378B (en) * | 2017-12-29 | 2022-03-18 | 中电普瑞电力工程有限公司 | Steady-state test device and method for modular multi-level converter valve |
| CN112583244A (en) * | 2019-09-29 | 2021-03-30 | 国创新能源汽车能源与信息创新中心(江苏)有限公司 | Voltage-sharing control device and method for direct-current bus capacitor of power electronic transformer system |
| CN112583244B (en) * | 2019-09-29 | 2021-11-09 | 国创移动能源创新中心(江苏)有限公司 | Voltage-sharing control device and method for direct-current bus capacitor of power electronic transformer system |
| CN111211677A (en) * | 2020-02-19 | 2020-05-29 | 南京工程学院 | Direct-current fault quick restart method of MMC type multi-port solid-state transformer |
| CN111211677B (en) * | 2020-02-19 | 2021-06-01 | 南京工程学院 | Direct-current fault quick restart method of MMC type multi-port solid-state transformer |
| CN115047333A (en) * | 2022-08-11 | 2022-09-13 | 国网经济技术研究院有限公司 | Passive unlocking test method and system for offshore platform converter valve wharf |
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