CN109193731B - Power control method for flexible direct current power grid system receiving end fault - Google Patents
Power control method for flexible direct current power grid system receiving end fault Download PDFInfo
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- CN109193731B CN109193731B CN201810995763.2A CN201810995763A CN109193731B CN 109193731 B CN109193731 B CN 109193731B CN 201810995763 A CN201810995763 A CN 201810995763A CN 109193731 B CN109193731 B CN 109193731B
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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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Abstract
The invention relates to the field of flexible direct current power transmission, in particular to a power control method for a fault of a receiving end of a flexible direct current network system. The method comprises the steps of acquiring active power reference values and actual measurement values of all poles of a converter station and the operation modes of all converters, calculating to obtain the total redundant capacity of a receiving-end converter, judging the difference value between the total redundant capacity of the receiving-end converter and the capacity of a fault converter when the receiving-end converter fails, only carrying out control mode switching if the difference value is positive, and reducing the total power of a transmitting-end converter station of a fault pole layer to the maximum transportable capacity of the rest receiving-end converters of the fault pole layer if the difference value is negative. The invention realizes the complete or partial power transfer of the fault pole, reduces the active power loss, actively distributes the power of each healthy pole, ensures the power balance of the direct current system, further realizes the stable operation of the system, and can meet the requirement of the stable operation of the flexible direct current network system by means of actively regulating the power.
Description
Technical Field
The invention relates to the field of flexible direct current power transmission, in particular to a power control method for a fault of a receiving end of a flexible direct current network system.
Background
The flexible direct current transmission adopts a Voltage Source Converter (VSC), generally uses a fully-controlled power electronic device (insulated gate bipolar transistor IGBT), and can independently and rapidly control active power and reactive power. The flexible direct current transmission has the advantages that asynchronous system interconnection can be achieved, the stability problem of alternating current transmission does not exist, active power and reactive power can be controlled by a control system, and the like. In addition, based on two basic characteristics of the fully-controlled device (IGBT) and the high-frequency modulation technology, the flexible direct-current transmission has incomparable technical advantages compared with the conventional direct-current transmission which adopts a semi-controlled device (thyristor) and a low-frequency modulation technology.
Based on the advantages of the flexible direct current transmission technology, the multi-terminal flexible direct current system is developed rapidly, however, the multi-terminal direct current system is only a prototype of a direct current power grid, the multi-terminal direct current is not provided with grids and has no redundancy and low reliability, the direct current power grid is a power transmission system with meshes, a plurality of direct current lines are connected between the converter stations through direct current circuit breakers, and the whole system has redundancy. The technology is one of the most distinctive technologies for constructing the smart power grid and the global energy Internet, and brings important changes to power transmission modes and power grid architectures.
Since the stability of a dc grid system depends on variations in the system input and output power: when the active power is insufficient, the direct-current voltage of the system is reduced; otherwise, the system dc voltage rises. Therefore, when the receiving end converter fails, a control strategy is required to ensure the stable operation of the system.
Disclosure of Invention
The invention aims to provide a power control method for a flexible direct current network system at receiving end fault, which is used for solving the problem of unstable system caused by unbalanced input and output power at the receiving end fault in the prior art.
In order to achieve the purpose, the invention provides a power control method for a flexible direct current grid system when a receiving end fails, which comprises the following steps:
if the receiving end converters are detected to be in fault, calculating the total redundant capacity of all the receiving end converters and the capacity of the fault converters; and if the total redundant capacity of the receiving end converter is smaller than the capacity of the fault converter, reducing the transmitting power of the fault pole layer, and enabling the transmitting total power of the transmitting end converter of the fault pole layer to be equal to the maximum transportable capacity of the receiving end converter of the fault pole layer.
The invention has the beneficial effects that: the total redundant capacity of the current-receiving end converter is calculated by collecting the active power reference value and the actual measurement value of each pole of all the converter stations and the operation mode of each current converter, if the current-receiving end converter fails at the moment, the difference value between the total redundant capacity of the current-receiving end converter and the capacity of the fault current converter is judged, and if the difference value is negative, the total power of the current-transmitting end converter station of the fault pole layer is reduced to the maximum transportable capacity of the rest current-receiving end converters of the fault pole layer.
Further, the total redundant capacity of the receiver converters is equal to the sum of the redundant capacities of each receiver converter.
Further, the capacity of the faulty converter is equal to: the difference between the redundant capacity and the actual power of the faulty converter.
Further, the maximum deliverable capacity is equal to: and in the fault pole layer, the sum of the redundant capacity and the actual power difference of all the non-fault receiving end converters.
Further, if the total redundant capacity of the receiving end converter is not smaller than the capacity of the fault converter, switching the control modes of the corresponding converter, wherein the control modes comprise four control modes of direct current voltage, active power, reactive power and alternating current voltage.
The invention realizes the complete or partial power transfer of the fault pole, reduces the active power loss, actively distributes the power of each healthy pole, ensures the power balance of the direct current system, further realizes the stable operation of the system, and can meet the requirement of the stable operation of the flexible direct current network system by means of actively regulating the power.
Drawings
FIG. 1 is a schematic diagram of a flexible DC power grid system of the present invention;
fig. 2 is a schematic diagram of a system with four converter stations according to an embodiment of the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
When a receiving end of a flexible direct current grid system fails, power needs to be coordinated and controlled, the flexible direct current grid system at least comprises three-end flexible direct current converter stations, each end converter station adopts a bipolar structure, each pole is provided with a converter (for example, a converter is arranged), each pole has control modes such as direct current voltage, active power, reactive power and alternating current voltage, each converter station is connected with other converter stations through a mesh-shaped direct current line, as shown in fig. 1, the flexible direct current grid system comprises N transmitting end stations and N receiving end stations, in the figure, PI _ rc11 is the redundant capacity of a pole 1 of a transmitting end station 1, and PI _ re11 is the actual power of the pole 1 of the transmitting end station 1; PI _ rcN1 is the redundancy capacity of the N pole 1 of the transmitting station, and PI _ reN1 is the actual power of the N pole 1 of the transmitting station; PR _ rc11 is the redundant capacity of the receiving station 1 pole 1, PR _ re11 is the actual power of the receiving station 1 pole 1; PR _ rcN1 is the redundant capacity of the receiving station N pole 1, and PR _ reN1 is the actual power of the receiving station N pole 1. The method of the invention comprises the following steps:
1) monitoring the running state of each converter in real time, and if the converter at the receiving end has a fault, executing the step 2);
2) judging the difference value between the total redundant capacity of the receiving end converter station and the capacity of the fault converter, if the difference value is positive and the fault converter is a power station, switching the bipolar operation mode into a unipolar operation mode, and if the difference value is positive and the fault converter is a voltage station, converting one power station corresponding to the pole layer into the voltage station; if the difference is negative, the total power of the current converter at the transmitting end of the fault pole layer is reduced to the maximum transportable capacity of the current converter at the receiving end of the fault pole layer without faults; taking the fault of the pole 1 of the receiving end converter station as an example:
the total redundant capacity of the receiving end converter is PR _ rc11+ PR _ rc12+ … … + PR _ rcN1+ PR _ rcN 2;
fault converter capacity is PR _ rc11-PR _ re 11;
the maximum transportable capacity of the receiving end converter without the fault on the fault pole layer is PR _ rc21-PR _ re21+ PR _ rc31-PR _ re31+ … … + PR _ rcN1-PR _ reN 1;
3) and returning to the step 1) after the step 2) is executed.
A specific embodiment is given below, a basic structure of the flexible dc power grid system according to this embodiment is shown in fig. 1, taking two receiving stations as two sending end stations, for example, as shown in fig. 2, in this embodiment, a station a and a station D are receiving end converter stations, a station B and a station C are sending end converter stations, and steady-state operation conditions of the system are as follows: d station determines DC voltage, the actual power of each pole is-500 MW, the active power of A station is-1200 MW respectively, the active power of B station is 1200MW respectively, the active power of C station is 500MW respectively, the redundant capacity of each pole of A station is 300MW, and the redundant capacity of each pole of D station is 250 MW.
In this embodiment, when the station pole 1 has a fault, the total redundant capacity of the receiving-end converter is 1100MW, the capacity of the fault converter is 1500MW, the maximum transferable power of the receiving-end converter of the fault pole layer is 750MW, and the difference between the total redundant capacity of the receiving-end converter station and the capacity of the fault converter is 400 MW; since the difference between the total redundant capacity of the receiving end converter station and the capacity of the fault converter is less than 0, the total power transmitted by the poles 1 of the power transmitting end station B and the power transmitting end station C is reduced to 750MW, and the system can be kept stable.
The present invention is not limited to the described embodiments, for example, different calculation manners when comparing capacities, or equivalent transformation of calculation manners when calculating capacity or power, and the technical solution formed by performing fine adjustment on the above embodiments still falls within the protection scope of the present invention.
Claims (3)
1. A power control method for flexible direct current grid system receiving end fault is characterized by comprising the following steps:
if the receiving end converters are detected to be in fault, calculating the total redundant capacity of all the receiving end converters and the capacity of the fault converters; if the total redundant capacity of the receiving end converters is smaller than the capacity of the fault converters, reducing the transmitting power of the fault pole layer to enable the transmitting total power of the transmitting end converters of the fault pole layer to be equal to the maximum transportable capacity of the receiving end converters of the fault pole layer, wherein the total redundant capacity of the receiving end converters is equal to the sum of the redundant capacities of each receiving end converter, and the capacity of the fault converters is equal to: the difference between the redundant capacity and the actual power of the faulty converter.
2. The power control method for the flexible direct current grid system in the case of receiving end fault according to claim 1, characterized in that: the maximum deliverable capacity is equal to: and in the fault pole layer, the sum of the redundant capacity and the actual power difference of all the non-fault receiving end converters.
3. The power control method for the flexible direct current grid system in the case of receiving end fault according to claim 1, characterized in that: and if the total redundant capacity of the receiving end converter is not less than the capacity of the fault converter, switching the control modes of the corresponding converter, wherein the control modes comprise four control modes of direct current voltage, active power, reactive power and alternating current voltage.
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| CN110365036B (en) * | 2019-07-23 | 2020-12-18 | 许继电气股份有限公司 | Power coordination control method and device for LCC-VSC direct current transmission system |
| CN110365037B (en) * | 2019-07-23 | 2020-12-18 | 许继电气股份有限公司 | Power coordination control method and device for LCC-VSC direct current transmission system |
| CN111313456B (en) * | 2020-03-25 | 2023-05-30 | 中国南方电网有限责任公司 | Safety and stability control method and system for multi-terminal direct current transmission system faults |
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| CN103219739B (en) * | 2013-04-26 | 2015-04-15 | 华北电力大学 | Emergent power supporting control method |
| CN105656070B (en) * | 2016-03-11 | 2018-06-26 | 特变电工新疆新能源股份有限公司 | Method for controlling fault ride-through of power grid of flexible direct-current transmission system |
| CN105978014B (en) * | 2016-06-08 | 2018-09-28 | 南京南瑞继保电气有限公司 | Parallel inverter direct current transportation interior communication descends failure locking method extremely |
| CN107039993B (en) * | 2017-04-20 | 2019-12-27 | 国网福建省电力有限公司 | Power band-turning control method for symmetrical bipolar flexible direct-current transmission converter |
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