CN113067362B - Control method for improving cascade type mixed direct current single-pole operation power limit - Google Patents
Control method for improving cascade type mixed direct current single-pole operation power limit Download PDFInfo
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- 238000011217 control strategy Methods 0.000 claims description 6
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- 230000005540 biological transmission Effects 0.000 description 5
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- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/10—Flexible AC transmission systems [FACTS]
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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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Abstract
The invention discloses a control method for improving cascade type mixed direct current single-pole operation power limit, which comprises the steps of normally unlocking a cascade type mixed direct current pole I, starting the cascade type mixed direct current pole I to a rated operation state, stopping an LCC converter station of a pole II, unlocking an MMC converter station of the pole II, working in a STATCOM mode, increasing reactive power through the MMC converter station of the pole II, and meeting reactive power requirements of LCC direct current after the power of the pole I is improved. The invention can meet the reactive power requirement of LCC direct current after the power of the mixed direct current single pole is increased on the premise of not increasing an additional reactive power compensation device, so that the mixed direct current single pole system can normally and stably operate; the LCC direct current commutation failure risk after the unipolar power is boosted can be reduced, the control is simple, and no additional equipment is needed.
Description
Technical Field
The invention relates to the technical field of hybrid direct-current power transmission, in particular to a control method for improving the limit of the cascade hybrid direct-current single-pole operation power.
Background
Hybrid direct current transmission has become an important development direction of direct current transmission technology in recent years due to the combination of the respective advantages of conventional direct current (LCC-HVDC) and flexible direct current (VSC-HVDC). A rectifying station of receiving-end cascade hybrid direct-current transmission (as shown in figure 1) is formed by connecting 2 groups of 12-pulse LCCs in series, an inverter station is formed by connecting 1 group of 12-pulse commutation converters (LCCs) and Voltage Source Converters (VSCs) in parallel in series, the low-end VSCs are expanded into a plurality of VSCs which are connected in parallel and are located in different regional power grids, and when the transmission power of a hybrid direct-current system is increased, a multi-drop structure is also beneficial to the staged construction of engineering (the MMC in figure 1 is a modular multilevel converter and belongs to one type of VSC). And because the receiving end converter station is cascaded with the LCC converter station after the plurality of VSC converter stations are connected in parallel, a multi-end system is actually formed, and the plurality of VSC converter stations are endowed with the power distribution capability.
If only the cascade type mixed direct current single-pole operation power is increased, the increase of the direct current power of the LCC inevitably causes the increase of reactive power consumed by the direct current of the LCC, the increase of the direct current reactive power demand of the LCC can cause the LCC to absorb a large amount of reactive power from an adjacent alternating current system, the voltage of an alternating current bus is reduced to a certain extent, and the risk of phase commutation failure of the direct current of the LCC is increased; on the other hand, the increase of the direct current reactive demand of the LCC can cause the action of a reactive power compensation device of an alternating current system, thereby bringing additional control problems.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a control method for increasing the power limit of a cascade-type hybrid dc single-pole operation, which can meet the reactive requirement of the LCC dc after the power of the hybrid dc single-pole operation is increased by the self-condition of the hybrid dc without adding an additional reactive power compensation device, so that the hybrid dc single-pole system after the power is increased can operate normally and stably. The technical scheme is as follows:
a control method for improving the power limit of a cascade type hybrid direct current single-pole operation comprises the following steps:
step 1: in a multi-drop-point receiving-end cascade hybrid direct-current system, unlocking a cascade hybrid direct-current pole I in a given alternating-current system operation mode;
step 2: unlocking the MMC converter station of the cascade type mixed direct current pole II and keeping the LCC converter station of the cascade type mixed direct current pole II in an off-state;
and step 3: gradually increasing the direct current instruction value to a desired value so as to promote the power of the cascade type mixed direct current electrode I to a rated operation state and stably operate;
and 4, step 4: setting an MMC converter station of a cascade type mixed direct current pole II as a STATCOM operation mode, wherein an active control strategy adopts constant direct current voltage control, and a reactive control strategy adopts constant alternating current voltage control, so that the MMC converter station only carries out reactive regulation and does not carry out active output;
and 5: under the steady state condition, the power of the cascade type mixed direct current pole I is continuously increased to 1.1 times of rated power for long-term operation, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends out partial reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased;
step 6: and under the transient condition, the power of the cascade type mixed direct current pole I is increased to 1.4 times of rated power for a short time, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends more reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased.
Further, the specific manner of unlocking the cascade type hybrid dc pole is as follows: the method comprises the steps of firstly unlocking a receiving end low-end MMC converter station in a constant direct current voltage mode, then unlocking a transmitting end LCC converter station and a receiving end LCC converter station simultaneously, and establishing direct current.
The invention has the beneficial effects that: according to the invention, the other pole of MMC converter station works in the STATCOM mode, so that a certain reactive power can be increased through the other pole of MMC converter station without adding an additional reactive power compensation device, the reactive power requirement of LCC direct current after the mixed direct current single-pole power is increased is met, and the mixed direct current single-pole system can normally and stably run; the LCC direct current commutation failure risk after the unipolar power is boosted can be reduced, the control is simple, and no additional equipment is needed.
Drawings
Fig. 1 is a multi-drop receiving-end cascade hybrid dc system (unipolar).
Fig. 2 shows the hybrid dc pole I power boost by 1.4 times.
Fig. 3 shows the increase of reactive power consumed by the LCC dc when the pole I active is raised.
FIG. 4 shows that the MMC of pole II generates a large amount of reactive power for supporting.
Fig. 5 shows the hybrid dc pole I power boost by 1.1 times.
Fig. 6 shows the increase in reactive power consumed by the LCC dc when the pole I active is increasing.
FIG. 7 is a graph of the small amount of reactive power generated by the pole II MMC for regulation.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The invention provides a control method for improving cascade type mixed direct current single-pole operation power limit, which comprises the steps of normally unlocking a cascade type mixed direct current pole I, starting the cascade type mixed direct current pole I to a rated operation state, stopping an LCC converter station of the pole II, unlocking an MMC converter station of the pole II, working in a STATCOM (Static Synchronous Compensator) mode, increasing reactive power through the MMC converter station of the pole II, and meeting reactive power requirements of LCC direct current after the power of the pole I is improved. The method comprises the following specific steps:
step 1: in a multi-drop-point receiving-end cascade hybrid direct-current system, unlocking a cascade hybrid direct-current pole I in a given alternating-current system operation mode; the concrete mode is as follows: firstly, unlocking a receiving end low-end MMC converter station in a constant direct current voltage mode, then unlocking a transmitting end LCC converter station and a receiving end LCC converter station simultaneously, and establishing direct current;
step 2: unlocking the MMC converter station of the cascade type mixed direct current pole II and keeping the LCC converter station of the cascade type mixed direct current pole II in an off-state;
and step 3: gradually increasing the direct current instruction value to a desired value so as to promote the power of the cascade type mixed direct current electrode I to a rated operation state and stably operate;
and 4, step 4: setting an MMC converter station of a cascade type mixed direct current pole II as an STATCOM operation mode, wherein an active control strategy adopts constant direct current voltage control, and a reactive control strategy adopts constant alternating current voltage control, so that the MMC only performs reactive regulation and does not perform active output;
and 5: under the steady state condition, the power of the cascade type mixed direct current pole I is continuously increased to 1.1 times of rated power for long-term operation, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends out partial reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased;
step 6: and under the transient condition, the power of the cascade type mixed direct current pole I is increased to 1.4 times of rated power for a short time, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends more reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased.
Calculation and verification were performed using a cascade type mixed direct current as an example as shown in fig. 1.
A first verification scheme:
when t =3s is set, the power I is increased to 1.4 times of rated power, during which the MMC converter station adjusting the pole II generates a large amount of reactive power to support the reactive demand of the pole I after the LCC power is increased, and the simulation results are respectively shown in fig. 2 to 4. As can be seen from fig. 2 and fig. 3, after the power of the hybrid dc electrode I is increased by 1.4 times, the dc consumption reactive power of the LCC converter station increases to 1200Mvar, and the LCC dc reactive demand is large, which affects the normal and stable operation of the hybrid dc. As can be seen from fig. 4, since the MMC converter station with the hybrid dc pole II operates in the STATCOM mode, the constant ac voltage control of the MMC converter station will play a role in maintaining the ac bus voltage, and automatically increase a large amount of reactive power, thereby meeting the LCC dc reactive power requirement.
Therefore, under the proposed strategy, the MMC of the pole II can send a large amount of reactive power to support, and the pole I can stably run after active power is promoted, so that the proposed strategy is proved to be effective.
And a second verification scheme:
and when t =3s is set, the power I is increased to 1.1 times of rated power, a small amount of reactive power is sent by the MMC converter station of the regulating pole II during the period to support the reactive power requirement after the LCC power of the pole I is increased, and simulation results are respectively shown in fig. 5 to 7. As can be seen from fig. 5 and 6, after the hybrid dc electrode I is boosted by 1.1 times, the reactive power consumed by the LCC dc power increases to about 730 Mvar.
Fig. 7 shows that the MMC converter station in stage II works in STATCOM mode to increase the reactive power by a suitable amount.
Therefore, under the proposed strategy, the MMC of the pole II can send out a proper amount of reactive power to adjust, and the pole I can stably run after active power is promoted, so that the proposed strategy is proved to be effective.
Claims (2)
1. A control method for increasing the power limit of a cascade type hybrid direct current single-pole operation is characterized by comprising the following steps:
step 1: in a multi-drop receiving-end cascade type hybrid direct current system, unlocking a cascade type hybrid direct current pole I in a given alternating current system operation mode;
step 2: unlocking the MMC converter station of the cascade type mixed direct current pole II and keeping the LCC converter station of the cascade type mixed direct current pole II in an off-state;
and step 3: gradually increasing the direct current instruction value to a desired value so as to promote the power of the cascade type mixed direct current electrode I to a rated operation state and stably operate;
and 4, step 4: setting an MMC converter station of a cascade type mixed direct current pole II as a STATCOM operation mode, wherein an active control strategy adopts constant direct current voltage control, and a reactive control strategy adopts constant alternating current voltage control, so that the MMC converter station only carries out reactive regulation and does not carry out active output;
and 5: under the steady state condition, the power of the cascade type mixed direct current pole I is continuously increased to 1.1 times of rated power for long-term operation, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends out partial reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased;
step 6: and under the transient condition, the power of the cascade type mixed direct current pole I is increased to 1.4 times of rated power for a short time, so that the MMC converter station of the cascade type mixed direct current pole II automatically sends more reactive power to support the reactive power requirement after the LCC power of the cascade type mixed direct current pole I is increased.
2. The control method for increasing the power limit of the cascade type hybrid direct current unipolar operation according to claim 1, wherein the specific manner for unlocking the cascade type hybrid direct current poles is as follows: the method comprises the steps of firstly unlocking a receiving end low-end MMC converter station in a constant direct current voltage mode, then unlocking a transmitting end LCC converter station and a receiving end LCC converter station simultaneously, and establishing direct current.
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