CN104578129A - Control method for multi-end flexible direct-current power transmission system - Google Patents
Control method for multi-end flexible direct-current power transmission system Download PDFInfo
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- CN104578129A CN104578129A CN201510009329.9A CN201510009329A CN104578129A CN 104578129 A CN104578129 A CN 104578129A CN 201510009329 A CN201510009329 A CN 201510009329A CN 104578129 A CN104578129 A CN 104578129A
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- load
- generator unit
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
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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]
Abstract
The invention discloses a control method for a multi-end flexible direct-current power transmission system. When the multi-end flexible direct-current power transmission system runs, a converter station connected with a pure power generation unit works in a direct-current bus voltage control mode and has the main function of maintaining the set value of the direct current bus voltage. A distributed power generation unit and a converter station connected with an isolated load work in a constant-frequency and constant-voltage (V/F) mode; a power generation unit with a load works in a constant-power mode, and whether electricity is taken from a direct current bus or sent to the direct current bus is determined according to the distribution conditions of local loads and system load flow; when faults happen in the pure power generation unit or in the converter station connected with the pure power generation unit and consequently the voltage of the direct current bus cannot be maintained, the power generation unit with the load is converted to be in the direct-current bus voltage control mode, and therefore the flexible direct-current power transmission system can stably run continuously. According to the control method for the multi-end flexible direct-current power transmission system, load flow distribution of the multi-end flexible direct-current power transmission system can be conveniently achieved, and the flexibility and stability of running of the system are improved.
Description
Technical field
The invention belongs to field of power, relate to the flexible direct-current transmission field containing distributed power source more specifically, be applicable to the control of Multi-end flexible direct current transmission system.
Background technology
Ac transmission is because of kelvin effect, corona effect and this body structure, and when transmission distance exceedes certain distance, Transmission Cost obviously increases; Ac transmission power decision is in the phase difference of two sections, circuit, and this phase difference increases along with the increase of transmission distance, and ac transmission controls complicated, and needs to compensate, and cannot realize asynchronous networking; Direct current transportation has very large advantage by contrast: DC line electric current and power adjustments are rapidly, conveniently, short circuit current is little; Circuit does not have capacitance current when steady operation, and voltage's distribiuting along the line is steady; Each pole can be used as an independent loop and runs; Based on these advantages, HVDC Transmission Technology obtains to be greatly developed.
The biggest obstacle of the new forms of energy such as wind energy, solar power generation access electrical network is that it is intermittent and uncertain, and flexible DC power transmission is just as adding one " equivalent capacity " in the line, effectively can solve the power quality problem caused because of uncertain, be the best way of generally acknowledged new forms of energy access electrical network.Flexible DC power transmission is the commanding elevation of power electronic technology application, is also one of key technology of intelligent grid.Compared with transmitting electricity with customary DC, its system response speed is fast, controllability good, operational mode is flexible; Greatly can reduce system short-circuit than conventional AC and DC transmission of electricity, can also power to passive network, be the effective way solving large area region power failure, realize remote isolated power transmission.
How flexible DC power transmission many employings multiterminal power transmission mode, reasonably control the operational mode of each sending end, reasonably trend distribution and make one of key of performance flexible DC power transmission.
Summary of the invention
The present invention proposes a kind of control method of Multi-end flexible direct current transmission system, the trend that it can easily realize Multi-end flexible direct current transmission system is distributed, and improves flexibility and the stability of system cloud gray model.
Specific implementation of the present invention is as follows:
A control method for Multi-end flexible direct current transmission system, is characterized in that:
Described Multi-end flexible direct current transmission system comprises the sending end of 4 types: the generator unit of pure generator unit, on-load, distributed generation unit and island load, and the generator unit of described pure generator unit, on-load, distributed generation unit and island load are connected to DC bus respectively by current conversion station;
When Multi-end flexible direct current transmission system is normally run:
The current conversion station that pure generator unit connects is operated in control DC bus-bar voltage pattern, and maintenance DC bus-bar voltage is set-point;
The current conversion station that distributed generation unit is connected with island load is operated in constant frequency and constant voltage (V/F) pattern;
The generator unit of on-load is operated in invariable power pattern, determines from DC bus power taking or to DC bus power transmission according to local load and system load flow distribution situation;
When pure generator unit or the current conversion station that is attached thereto break down cause maintaining DC bus-bar voltage time:
The generator unit of on-load is transferred to control DC bus-bar voltage pattern, make flexible direct current power transmission system continue stable operation.
A control method for Multi-end flexible direct current transmission system, is characterized in that, said method comprising the steps of:
(1) first start pure generator unit and set up ac bus voltage; Then start corresponding current conversion station, make current conversion station be operated in control DC bus-bar voltage pattern, DC bus-bar voltage is expected can on-line tuning;
(2) DC bus-bar voltage stable after, start the current conversion station at island load place, make current conversion station be operated in constant frequency and constant voltage V/F Model Establishment and play ac bus voltage and power to island load, alternating current voltage frequency is determined according to load rated frequency; Now electric energy needed for load is provided by pure generator unit;
(3) start the current conversion station at distributed power source place, make current conversion station be operated in constant frequency and constant voltage V/F Model Establishment and play ac bus voltage, alternating current voltage frequency is determined according to the rated frequency of distributed generation unit; After ac bus voltage stabilization, start distributed generation system to DC bus power transmission;
(4) relation of island load power demand and distributed power source and pure generator unit generated output is judged, when island load power demand is greater than distributed power source and pure generator unit generated output sum, enter step (5), when island load power demand is less than or equal to distributed power source generated output, enter step (6), when island load power demand is greater than distributed power source generated output, but when being less than or equal to distributed power source and pure generator unit generated output sum, enter step (7);
(5) if the reserve capacity of on-load generator unit is sufficient, then start the current conversion station at on-load generator unit place, make the current conversion station at on-load generator unit place be operated in invariable power pattern, to DC bus power transmission, power is expected to determine according to power shortage; If the reserve capacity of on-load generator unit is not enough, after needing cut-out island load, restart the current conversion station at on-load generator unit place;
(6) start the current conversion station at on-load generator unit place, make it to be operated in invariable power pattern, power to local load from DC bus power taking, make the power of Multi-end flexible direct current transmission system reach dynamic equilibrium;
(7) if start corresponding current conversion station when the power output of the generator unit of on-load is greater than 95% of its rated power, the converter at the generator unit place of on-load is made to be operated in invariable power pattern, from DC bus power taking;
(8) when the current conversion station of pure generator unit or correspondence break down can not maintain DC bus-bar voltage time, the current conversion station at on-load generator unit place is converted to control DC bus-bar voltage pattern; Can not transship after will guaranteeing the generator unit conversion of on-load before conversion; If the generator unit of on-load can be in overlond running after conversion, then need the power output or the cut-out island load that increase distributed power source.
Beneficial effect of the present invention
The present invention proposes a kind of control method of Multi-end flexible direct current transmission system, by reasonably arranging the mode of operation of each current conversion station, achieving the reasonable distribution of system load flow, improve the reliability of system cloud gray model.
Present invention achieves close friend's access of distributed power source, improve the utilance of distributed power source.
The present invention distributes the power output that can effectively reduce generator unit by rational trend, improve economy.
Present invention achieves the remote power transmission to island load.
Accompanying drawing explanation
Fig. 1 is Multi-end flexible direct current transmission system connection diagram of the present invention;
Fig. 2 is the control flow schematic diagram of the control method of a kind of Multi-end flexible direct current transmission system of the present invention.
Embodiment
Technical scheme of the present invention to be stated further in detail in conjunction with concrete case study on implementation according to Figure of description below.
Fig. 1 is Multi-end flexible direct current transmission system connection diagram of the present invention.System comprises the sending end of 4 types: the generator unit of pure generator unit, on-load, distributed generation unit and island load; The current conversion station that when Multi-end flexible direct current transmission system is run, pure generator unit connects is operated in control DC bus-bar voltage pattern, and major function is maintenance DC bus-bar voltage is set-point; The current conversion station that distributed generation unit is connected with island load is operated in constant frequency and constant voltage (V/F) pattern; The generator unit of on-load is operated in invariable power pattern, determines from DC bus power taking or to DC bus power transmission according to local load and system load flow distribution situation; When pure generator unit or the current conversion station that is attached thereto break down cause maintaining DC bus-bar voltage time, the generator unit of on-load is transferred to control DC bus-bar voltage pattern, makes flexible direct current power transmission system continue stable operation.
Fig. 2 is the control flow schematic diagram of the control method of a kind of Multi-end flexible direct current transmission system of the present invention.Described control method comprises the steps:
(1) start pure generator unit with V/F pattern and set up ac bus voltage; After alternating-voltage stabilization, start current conversion station 1, make current conversion station 1 be operated in control DC bus-bar voltage pattern, provide stable DC bus-bar voltage to other current conversion stations in system; DC bus-bar voltage can according to expectation on-line tuning;
(2), after DC bus-bar voltage is stablized, the preliminary filling loop of current conversion station 4 is started; Start current conversion station 4 with V/F pattern after preliminary filling completes, set up ac bus voltage and power to island load.Alternating voltage sets up speed and the time can be arranged, and prevents from causing that transformer magnetizing current is excessive causes protection act due to Voltage Establishment excessive velocities; Alternating current voltage frequency needs to determine according to the rated frequency of load; Electric energy needed for testing load is provided by pure generator unit;
(3) current conversion station 4 starts and after system run all right, starts the preliminary filling loop of current conversion station 3; Start current conversion station 3 with constant frequency and constant voltage pattern after current conversion station 3 preliminary filling completes, set up ac bus voltage and start use to distributed power source.Alternating voltage sets up speed and the time can be arranged, and prevents from causing that transformer magnetizing current is excessive causes protection act due to Voltage Establishment excessive velocities; Alternating current voltage frequency is determined according to the rated frequency of distributed generation unit.After ac bus voltage stabilization, start distributed generation system to DC bus power transmission, reduce pure generator unit and exert oneself; Now electric energy needed for island load is provided jointly by pure generator unit and distributed power source;
(4) relation of island load power demand and distributed power source and pure generator unit generated output is judged, when island load power demand is greater than distributed power source and pure generator unit generated output sum, enter step (5), when island load power demand is less than or equal to distributed power source generated output, enter step (6), when island load power demand is greater than distributed power source generated output, but when being less than or equal to distributed power source and pure generator unit generated output sum, enter step (7);
(5) if the reserve capacity of on-load generator unit is sufficient, then automatic current conversion station 2, make current conversion station 2 be operated in invariable power pattern, to DC bus power transmission, power transmission power is determined according to power shortage; If the reserve capacity of on-load generator unit is not enough, then cut-out island load is needed to start current conversion station 2 with invariable power pattern again;
(6) start current conversion station 2, make current conversion station 2 be operated in invariable power pattern, power to local load from DC bus power taking, power taking power is the difference of generation of electricity by new energy unit generated output and island load power demand; Not only can reduce the power output of generator unit, the utilance of generation of electricity by new energy can also be improved;
(7) if start current conversion station 2 when on-load generator unit is in overload or heavy duty, make current conversion station 2 be operated in invariable power pattern from DC bus power taking, power taking power is determined according to DC bus power margin; If DC bus power margin is not enough to make on-load generator unit depart from heavy duty or overload situations, generated output or the cut-out island load of distributed power source can be increased;
(8) when the current conversion station (current conversion station 1) of pure generator unit or correspondence break down can not maintain DC bus-bar voltage time, current conversion station 2 is transferred to control DC bus-bar voltage pattern, continuing to maintain DC bus-bar voltage is set-point; Overload and inverse probability situation is there will not be after needing to guarantee the conversion of on-load generator unit before conversion; If on-load generator unit can be in overlond running after conversion, then need the power output or the cut-out island load that increase distributed generation unit; If there will be inverse probability situation after conversion, need the power output reducing distributed generation unit.
Claims (2)
1. a control method for Multi-end flexible direct current transmission system, is characterized in that:
Described Multi-end flexible direct current transmission system comprises the sending end of 4 types: the generator unit of pure generator unit, on-load, distributed generation unit and island load, and the generator unit of described pure generator unit, on-load, distributed generation unit and island load are connected to DC bus respectively by current conversion station;
When Multi-end flexible direct current transmission system is normally run:
The current conversion station that pure generator unit connects is operated in control DC bus-bar voltage pattern, and maintenance DC bus-bar voltage is set-point;
The current conversion station that distributed generation unit is connected with island load is operated in constant frequency and constant voltage (V/F) pattern;
The generator unit of on-load is operated in invariable power pattern, determines from DC bus power taking or to DC bus power transmission according to local load and system load flow distribution situation.
When pure generator unit or the current conversion station that is attached thereto break down cause maintaining DC bus-bar voltage time:
The generator unit of on-load is transferred to control DC bus-bar voltage pattern, make flexible direct current power transmission system continue stable operation.
2. a control method for Multi-end flexible direct current transmission system, is characterized in that, said method comprising the steps of:
(1) first start pure generator unit and set up ac bus voltage; Then start corresponding current conversion station, make current conversion station be operated in control DC bus-bar voltage pattern, DC bus-bar voltage is expected can on-line tuning;
(2) DC bus-bar voltage stable after, start the current conversion station at island load place, make current conversion station be operated in constant frequency and constant voltage V/F Model Establishment and play ac bus voltage and power to island load, alternating current voltage frequency is determined according to load rated frequency; Now electric energy needed for load is provided by pure generator unit;
(3) start the current conversion station at distributed power source place, make current conversion station be operated in constant frequency and constant voltage V/F Model Establishment and play ac bus voltage, alternating current voltage frequency is determined according to the rated frequency of distributed generation unit; After ac bus voltage stabilization, start distributed generation system to DC bus power transmission;
(4) judge the relation of island load power demand and distributed power source and pure generator unit generated output, when island load power demand is greater than distributed power source and pure generator unit generated output sum, enter step (5); When island load power demand is less than or equal to distributed power source generated output, enter step (6); When island load power demand is greater than distributed power source generated output, but when being less than or equal to distributed power source and pure generator unit generated output sum, enter step (7);
(5) if the reserve capacity of the generator unit of on-load is sufficient, then start the current conversion station at the generator unit place of on-load, make the current conversion station at the generator unit place of on-load be operated in invariable power pattern, to DC bus power transmission, power is expected to determine according to power shortage; If the reserve capacity of on-load generator unit is not enough, after needing cut-out island load, restart the current conversion station at on-load generator unit place;
(6) start the current conversion station at on-load generator unit place, make it to be operated in invariable power pattern, power to local load from DC bus power taking, make the power of Multi-end flexible direct current transmission system reach dynamic equilibrium;
(7) if start corresponding current conversion station when the power output of the generator unit of on-load is greater than 95% of its rated power, the current conversion station at the generator unit place of on-load is made to be operated in invariable power pattern, from DC bus power taking;
(8) when the current conversion station of pure generator unit or correspondence break down can not maintain DC bus-bar voltage time, the current conversion station at the generator unit place of on-load is converted to control DC bus-bar voltage pattern; Can not transship after will guaranteeing the generator unit conversion of on-load before conversion; If the generator unit of on-load can be in overlond running after conversion, then need the power output or the cut-out island load that increase distributed power source.
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Cited By (2)
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| CN110620375A (en) * | 2019-08-23 | 2019-12-27 | 广东电网有限责任公司珠海供电局 | High-reliability shutdown method for direct-current power distribution system |
| CN116526482A (en) * | 2023-06-19 | 2023-08-01 | 国网上海能源互联网研究院有限公司 | Grid-connected self-adaptive coordination control method and device for multi-low-voltage flexible interconnection device |
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