CN111463821A - Equal-load-rate master-slave control method suitable for direct-current power distribution network - Google Patents

Equal-load-rate master-slave control method suitable for direct-current power distribution network Download PDF

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Publication number
CN111463821A
CN111463821A CN202010430217.1A CN202010430217A CN111463821A CN 111463821 A CN111463821 A CN 111463821A CN 202010430217 A CN202010430217 A CN 202010430217A CN 111463821 A CN111463821 A CN 111463821A
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direct
distribution network
power distribution
station
current power
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Inventor
王秀茹
邱冬
韩少华
刘刚
王一振
朱琳
邱逢良
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State Grid Jiangsu Electric Power Co ltd Suqian Power Supply Branch
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State Grid Jiangsu Electric Power Co ltd Suqian Power Supply Branch
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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
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • 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]

Abstract

The invention relates to an equal-load-rate master-slave control method suitable for a direct-current power distribution network, belonging to the field of flexible direct-current power distribution systems, and comprising the following steps: the direct-current power distribution network adopts a master-slave control method, and the direct-current voltage is controlled by the master station, so that the voltage stability of the direct-current power distribution network is guaranteed; and the power instruction of the slave station changes in real time according to the running state of each converter station of the direct-current power distribution network so as to achieve the state that the load rates of the converter stations are equal. The control principle of the invention is simple and easy to operate, and the voltage control of the direct current distribution network has good rigidity and can ensure that the power of the direct current distribution network can be reasonably distributed.

Description

Equal-load-rate master-slave control method suitable for direct-current power distribution network
Technical Field
The invention belongs to the field of flexible direct-current power distribution networks, and particularly relates to an equal-load-rate master-slave control method suitable for a direct-current power distribution network.
Background
With the development of distributed power supplies, electric vehicles, energy storage, power electronic technologies and urban power distribution systems, direct-current power distribution networks have become a research hotspot, and have wide development prospects particularly in areas with high proportion of distributed power supplies and direct-current loads.
Firstly, a direct-current power distribution network based on a Voltage Source Converter (VSC) can realize interconnection and mutual supply of different alternating-current power distribution networks, active control of power flow can be realized, problems of reactive compensation, commutation failure and the like do not exist, power supply quality of a system can be improved, and reliability and controllability of the power distribution network are improved.
Secondly, the direct-current power distribution network can be used as a buffer link to reduce negative effects caused by random load power fluctuation of a fan, a photovoltaic distributed power supply and the like and an electric vehicle and the like, and the requirements of flexible distributed power supply access, high permeability access and plug-and-play of direct-current loads of the electric vehicle and the like are met.
Therefore, the direct-current power distribution network has great application prospect. However, the dc power distribution network includes a plurality of flexible dc converter stations, and how to coordinate the plurality of converter stations to achieve stable operation of the dc power distribution network is a difficult problem.
The direct-current power distribution network is widely connected with an intermittent distributed power source and a random load, the power disturbance is large, and at present, a direct-current power distribution network control method mainly comprises a master-slave control method and a direct-current voltage droop control method. If the traditional master-slave control is adopted, the power instruction of the slave station needs to be changed all the time, and once large disturbance occurs, the problem of unbalanced power distribution can occur, and even the stability of direct-current voltage is influenced. On the other hand, if the droop control method is adopted, the dc voltage deviation cannot be guaranteed within a reasonable range, and further improvement on droop control is required.
In summary, in order to achieve a rigid voltage distribution and a reasonable power distribution of a dc power distribution network under power disturbance, a control method suitable for the dc power distribution network needs to be provided urgently.
Disclosure of Invention
The invention aims to realize rigid voltage distribution and reasonable power distribution of a direct-current power distribution network under power disturbance, and provides a constant-load-rate master-slave control method suitable for the direct-current power distribution network.
The invention is realized by adopting the following technical scheme:
the equal-load-rate master-slave control method is suitable for the direct-current power distribution network, wherein direct-current voltage is controlled by a master station, and power instructions of slave stations change in real time according to the running state of each converter station of the direct-current power distribution network so as to achieve the state that the load rates of the converter stations are equal.
The method comprises the following specific steps:
1) the direct-current power distribution network adopts a master-slave control method, and direct-current voltage is controlled by a master station;
2) measuring the power of each converter station, wherein the power direction is positive from the ac system to the dc system,
Figure 100002_DEST_PATH_IMAGE001
the measured power of the ith converter station is referred, i is a natural number greater than 0;
3) calculating the integral load rate of the DC distribution network
Figure 454030DEST_PATH_IMAGE002
Wherein
Figure 100002_DEST_PATH_IMAGE003
Is as followsiThe rated capacity of the individual converter stations,nthe number of flexible dc converter stations included for the dc distribution network,nis a natural number greater than 0;
Figure 624112DEST_PATH_IMAGE002
the calculation formula of (a) is as follows,
Figure 349753DEST_PATH_IMAGE004
；
4) calculate the firstiPower instruction of slave station
Figure 100002_DEST_PATH_IMAGE005
The calculation formula is as follows,
Figure 972496DEST_PATH_IMAGE006
。
the master station for controlling is generally borne by the converter station with the largest capacity;
the flexible direct current converter stations of the direct current power distribution network have rapid communication capacity;
in said invention, once the first stepkWhen the slave station breaks down and stops running, the rest direct-current power distribution network still runs according to the equal load rate master-slave control method, and only the load rate changes as follows:
Figure DEST_PATH_IMAGE007
。
in the invention, once the main station fails and quits operation, the converter station with the second capacity replaces the direct-current voltage control task, namely the converter station with the second capacity is switched from the power control mode to the voltage control mode, and the control methods of the converter stations of the other slave stations are not changed.
The invention has the technical characteristics that: on the basis of fully considering that the direct-current power distribution network is small in area and has good communication, the invention provides an equal-load-rate master-slave control method suitable for the direct-current power distribution network. According to the method, the load rate of the direct current distribution network is obtained by measuring the power of each converter station, and the power instruction of the slave station is adjusted in real time by utilizing the load rate, so that the voltage control of the direct current distribution network has good rigidity, and the power of the direct current distribution network can be reasonably distributed.
The invention has the beneficial effects that: the invention changes the slave station power instruction in real time by using the running state information in the master-slave control method, has simple and easily realized working principle and is suitable for controlling the direct current distribution network. When power disturbance occurs to the direct current distribution network and unbalanced power is distributed among the converter stations, the voltage control of the direct current distribution network can be realized to have good rigidity through the method and the device, and the power of the direct current distribution network can be reasonably distributed.
Drawings
The invention will be further explained with reference to the drawings, in which:
FIG. 1 is a schematic diagram of a three-terminal flexible DC distribution network;
FIG. 2 is a schematic diagram of an equal duty master-slave control scheme according to the present invention;
FIG. 3 shows a simulation result of load ratios of the converter stations according to an embodiment of the present invention;
fig. 4 is a simulation result of the dc voltage in the embodiment of the present invention.
Detailed Description
The following describes a method for equalizing load rate of a dc power distribution network according to the present invention in detail with reference to fig. 1 to 4.
FIG. 1 is a schematic diagram of a three-terminal flexible DC distribution network with DC voltage ratings of
Figure 979635DEST_PATH_IMAGE008
kV. The VSCs 1-3 in the figure represent flexible dc converter stations, i.e. voltage source converter systems, where the VSC1 has a maximum capacity of 15MVA, so the VSC1 is the controlling master station and the controlling dc voltage is the controlling dc voltage
Figure 863277DEST_PATH_IMAGE008
kV. The VSC2 has a rated capacity of 10MVA, the VSC3 has a rated capacity of 8MVA, and the VSC2 and the VSC3 operate in a power control mode.
The control schematic block diagram of the equal load rate method applicable to the direct current distribution network provided by the invention is shown in fig. 2, wherein n =3 is shown in the diagram, and the specific implementation mode is as follows:
1) the direct current distribution network adopts a master-slave control method, the direct current voltage is controlled by a master station VSC1, namely:
Figure DEST_PATH_IMAGE009
kV；
2) measuring power of individual converter stations
Figure 712152DEST_PATH_IMAGE010
，
Figure DEST_PATH_IMAGE011
，
Figure 743562DEST_PATH_IMAGE012
(ii) a Wherein the power direction is positive from the ac system to the dc system;
3) calculating the integral load rate of the DC distribution network
Figure 852594DEST_PATH_IMAGE002
Wherein
Figure 262847DEST_PATH_IMAGE003
Is as followsiRated capacity of the individual converter stations;
Figure 641876DEST_PATH_IMAGE002
the calculation formula is as follows:
Figure DEST_PATH_IMAGE013
；
4) calculating power instructions of the VSC1 and the VSC 2;
Figure 754057DEST_PATH_IMAGE014
；
Figure DEST_PATH_IMAGE015
；
the disturbance situation is set as follows:
1) when t =1s, the total load increases from 2.2MW to 4.4 MW;
2) at t =2s, the total load increased from 4.4MW to 13.2 MW;
3) at t =3s, the total load increased from 13.2MW to 22 MW;
4) when t =3s, the VSC3 is disconnected without failure;
and t is simulation time.
The simulation results of this example are shown in fig. 3 and 4. Due to the adoption of the equal-load-rate master-slave control method suitable for the direct-current power distribution network, the three-end flexible direct-current power distribution network can always ensure that the direct-current voltage is stabilized at 20kV in the face of various disturbances, and has good rigidity control. Moreover, the load ratio of each converter station is the same, and the reasonable power distribution capability is realized.
In conclusion, the simulation result of the three-terminal flexible direct-current power distribution network under disturbance verifies the correctness and the effectiveness of the proposed equal-load-rate master-slave control method suitable for the direct-current power distribution network.
Therefore, the tasks of the equal-load-rate master-slave control method suitable for the direct-current power distribution network are completely finished.

Claims (6)

1. A constant-load-rate master-slave control method suitable for a direct-current power distribution network is characterized in that a power instruction of a slave station changes in real time according to the running state of each converter station of the direct-current power distribution network so as to achieve the state that the load rates of the converter stations are equal, and the method comprises the following steps:
(1) the direct-current power distribution network adopts a master-slave control method, and direct-current voltage is controlled by a master station;
(2) measuring the power of each converter station, wherein the power direction is positive from the ac system to the dc system,
Figure DEST_PATH_IMAGE002
refers to the power measured by the ith converter station;
(3) calculating the integral load rate of the DC distribution network
Figure DEST_PATH_IMAGE001
Wherein
Figure 252146DEST_PATH_IMAGE002
Is as followsiThe rated capacity of the individual converter stations,nthe number of flexible direct current converter stations included in the direct current power distribution network;
Figure DEST_PATH_IMAGE003
；
(4) calculate the firstiPower command of slave station converter station
Figure 887265DEST_PATH_IMAGE004
；
Figure DEST_PATH_IMAGE005
。
2. The equal-load-rate master-slave control method suitable for the direct current power distribution network according to claim 1, wherein each flexible direct current converter station of the direct current power distribution network has a rapid communication capability.
3. The equal-load-ratio master-slave control method suitable for the direct current power distribution network according to claim 1, wherein in the step (1), the converter station with the largest capacity is selected as the master station for controlling the direct current voltage.
4. The method as claimed in claim 1, wherein the first time of the first time is the first timekWhen the slave station breaks down and stops running, the rest direct-current power distribution network still runs according to the equal load rate master-slave control method, and only the load rate changes as follows:
Figure 493827DEST_PATH_IMAGE006
。
5. the method as claimed in claim 1, wherein the slave station is configured to take over the dc voltage control task by the next-to-capacity converter station when the master station fails and exits from operation, that is, the next-to-capacity converter station is switched from the power control mode to the voltage control mode, and the control methods of the remaining slave station converter stations are not changed.
6. The equal-load-rate master-slave control method suitable for the direct-current power distribution network, according to claim 1, is applied to a multi-terminal flexible direct-current transmission network, even a future direct-current power network, under the condition of good communication.
CN202010430217.1A 2020-05-20 2020-05-20 Equal-load-rate master-slave control method suitable for direct-current power distribution network Pending CN111463821A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113991757A (en) * 2021-10-29 2022-01-28 国电南瑞科技股份有限公司 Method, system and device for controlling low-voltage direct-current flexible interconnection power of cell under non-communication condition and storage medium

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104505853A (en) * 2015-01-08 2015-04-08 南方电网科学研究院有限责任公司 Power distribution method for multiple constant direct current voltage stations in multi-terminal flexible direct current power transmission system
CN108390389A (en) * 2018-03-19 2018-08-10 华北电力大学 Current transformer Poewr control method is interconnected in a kind of master ＆ slave control mixing micro-capacitance sensor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104505853A (en) * 2015-01-08 2015-04-08 南方电网科学研究院有限责任公司 Power distribution method for multiple constant direct current voltage stations in multi-terminal flexible direct current power transmission system
CN108390389A (en) * 2018-03-19 2018-08-10 华北电力大学 Current transformer Poewr control method is interconnected in a kind of master ＆ slave control mixing micro-capacitance sensor

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* Cited by examiner, † Cited by third party
Title
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113991757A (en) * 2021-10-29 2022-01-28 国电南瑞科技股份有限公司 Method, system and device for controlling low-voltage direct-current flexible interconnection power of cell under non-communication condition and storage medium
CN113991757B (en) * 2021-10-29 2024-03-26 国电南瑞科技股份有限公司 Low-voltage direct-current flexible interconnection power control method, system and device for communication-free lower station area and storage medium

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Application publication date: 20200728