CN110601247A - Droop control method suitable for multi-end direct current sending of offshore wind power - Google Patents
Droop control method suitable for multi-end direct current sending of offshore wind power Download PDFInfo
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- CN110601247A CN110601247A CN201910811647.5A CN201910811647A CN110601247A CN 110601247 A CN110601247 A CN 110601247A CN 201910811647 A CN201910811647 A CN 201910811647A CN 110601247 A CN110601247 A CN 110601247A
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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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]
Abstract
The invention discloses a droop control method, which comprises the following steps: respectively acquiring electrical quantities of an offshore converter station and a onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station acquires a phase angle required by Park transformation through a phase-locked loop, and the offshore converter station acquires the phase angle required by Park transformation through a preset voltage frequency; respectively carrying out Park conversion on the electric quantity of the alternating current side of the offshore converter station and the onshore converter station, and acquiring the electric value of the electric quantity in a grid voltage synchronous rotation dq coordinate system; respectively acquiring inner ring controllers of the offshore converter station and the onshore converter station under a dq coordinate system; and respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station into the inner ring controller. By adopting the invention, the direct-current voltage reference value of the converter station can be maintained in the allowable range, so that the power transmission system is kept stable.
Description
Technical Field
The invention relates to the field of offshore wind power transmission, in particular to a droop control method suitable for multi-end direct current transmission of offshore wind power.
Background
The multi-terminal flexible direct current transmission system at least comprises three or more voltage source converter stations (VSC), receives power at multiple points, can flexibly, conveniently and reliably control power flow change, and is a mode which has the greatest advantage of realizing large-scale and distributed offshore and has the most potential in realizing multi-power supply and wind power grid connection. The multi-terminal direct current power transmission system mainly comprises two main modes of master-slave control and droop control. In the master-slave control strategy, one converter station is used as a master station for controlling the stability of the direct-current voltage and ensuring the balance of the active power of the system, and when the master station is forced to quit the operation due to a fault, the slave station receives signals through the communication system, so that the original master station is replaced by a conversion control mode for controlling the direct-current voltage. The control method has the following defects that only one VSC maintains constant voltage and keeps power balance at the same time, so that the response speed is slow; when the main controller is switched, the voltage can be suddenly deviated to cause system oscillation, and when the tidal current change is large, the voltage deviation is large; when the number of the converter stations is large, the voltage margin levels set by the converter stations are large, so that the complexity of design is increased, and the voltage deviation is increased.
In the multi-terminal direct current project which is actually put into operation at present, a multi-terminal flexible direct current transmission project in south and south China adopts master-slave direct current voltage control; the five-terminal flexible direct-current transmission project of Zhoshan mountain in Zhejiang province of China combines two modes of master-slave control and margin control backup. The direct current voltage droop control is mainly based on the variable relation between direct current voltage and power or current, when the system power changes, each converter station participates in power balance, and the direct current voltage of each converter station correspondingly changes along a droop curve. The direct-current voltage droop control method has the advantages of being convenient to operate, enabling direct-current voltage to be continuously adjusted, and avoiding the problem of electrical impact caused when modes are switched like voltage margin control. When the direct current system normally operates, the direct current voltage has a fluctuation range limit (for example, fluctuation within a range of +/-10% of rated direct current voltage). If the droop slope is large, the change of the direct-current voltage is large, and the direct-current voltage easily exceeds the fluctuation range of the direct-current voltage; and if the direct current voltage fluctuation is too small, the effect of frequency droop control cannot be achieved. Therefore, it is important to select a proper droop coefficient by using the dc voltage droop control.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a droop control method suitable for sending out offshore wind power through multi-terminal direct current, which can maintain a dc voltage reference value of a converter station within an allowable range, so that a power transmission system is stable.
Based on this, the embodiment of the invention provides a droop control method suitable for offshore wind power output through multi-terminal direct current, which comprises the following steps:
respectively acquiring electrical quantities of an offshore converter station and a onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station acquires a phase angle required by Park transformation through a phase-locked loop, and the offshore converter station acquires the phase angle required by Park transformation through a preset voltage frequency;
respectively carrying out Park conversion on the electric quantity of the alternating current side of the offshore converter station and the onshore converter station, and acquiring the electric value of the electric quantity in a grid voltage synchronous rotation dq coordinate system;
respectively acquiring inner ring controllers of the offshore converter station and the onshore converter station under a dq coordinate system;
and respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station into the inner ring controller.
The inner ring controller of the land converter station under the dq coordinate system comprises:
wherein, K(·)A PI controller parameter representing the inner loop controller,for the inner loop dq current reference value,is an equivalent reactance on the alternating-current side,three-phase voltages and currents, respectively, at a common coupling node, toCarrying out Park change to obtain an electrical value under a grid voltage synchronous rotation dq coordinate system Obtaining phase angle required by Park transformation for the land converter station through a phase-locked loop, and output variable of an inner loop controllerObtaining the value under the abc coordinate system under the action of Park inverse transformationI.e. the converter station reference voltage value.
Wherein inputting the current reference value of the outer loop controller of the onshore converter station to the inner loop controller comprises:
the current reference value component of the voltage control station comprises:
wherein the content of the first and second substances,for the rated operating parameter design values of the multi-terminal system,for instruction values of upper control, k(·)For the parameters, k, of the DC voltage/reactive power PI controllerdc,i，For improved droop algorithm control parameters, p is the number of the land converter stations.
Wherein, k isdcThe value range is as follows:
wherein the inner ring controller of the offshore converter station in dq coordinate system comprises:
wherein, K(·)A PI controller parameter representing an inner loop controller,for the inner loop dq current reference value,is an equivalent reactance on the alternating-current side,three-phase voltages and currents, respectively, at a common coupling node, saidCarrying out Park change to obtain an electrical value under a grid voltage synchronous rotation dq coordinate system Obtaining a phase angle required by Park transformation for the offshore converter station through a preset voltage frequency, and outputting a variable of an inner ring controllerObtaining the value under the abc coordinate system under the action of Park inverse changeI.e. the inverter reference voltage value.
Wherein inputting the current of the outer ring controller of the offshore converter station to the inner ring controller comprises:
the current reference value component of the offshore converter station comprises:
wherein the content of the first and second substances,is a reference value of the voltage at the PCC point,
k(·)for the dc voltage/reactive power PI controller parameters,is the PCC point voltage amplitude.
Wherein the method further comprises, before:
selecting a plurality of land converter stations from the plurality of land converter stations as a voltage control station, wherein the voltage control station is used for ensuring that the direct current side voltage of the land converter stations is not greater than the maximum voltage value;
setting the land converter stations except the voltage control station into an active power/reactive power control mode;
and the control mode of the offshore converter station is set to be a constant alternating current voltage mode.
The embodiment of the invention also provides a droop control device, which comprises:
the acquisition module is used for respectively acquiring electrical quantities of the offshore converter station and the onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station acquires a phase angle required by Park conversion through a phase-locked loop, and the offshore converter station acquires a phase angle required by Park conversion through a preset voltage frequency;
the conversion module is used for respectively carrying out Park conversion on the electric quantity at the alternating current side of the offshore converter station and the onshore converter station, acquiring the electric value of the electric quantity under a dq coordinate system of synchronous rotation of the grid voltage, and respectively acquiring the inner ring controllers of the offshore converter station and the onshore converter station under the dq coordinate system;
and the input module is used for respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station to the inner ring controller.
The embodiment of the present invention further provides a droop control apparatus, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, the droop control method suitable for marine wind power to be sent out via multi-terminal direct current is implemented.
The embodiment of the present invention further provides a computer-readable storage medium, which is characterized in that the computer-readable storage medium includes a stored computer program, and when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the above droop control method suitable for sending out offshore wind power through multi-terminal direct current.
By adopting the method and the device, the voltage reference value of the converter station in the voltage control mode can be ensured to be changed within the allowable area range all the time, and the safe and stable operation of a multi-terminal system is ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a droop control method suitable for offshore wind power output via multi-terminal direct current according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a multi-terminal DC power grid including N offshore converter stations and M onshore converter stations according to an embodiment of the present invention;
fig. 3 is a schematic diagram of an ith land converter station provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a jth offshore converter station provided by an embodiment of the present invention;
fig. 5 is a schematic view of a droop control apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a flowchart of a droop control method suitable for marine wind power output through multi-terminal direct current according to an embodiment of the present invention, where the droop control method suitable for marine wind power output through multi-terminal direct current includes:
s101, respectively obtaining electrical quantities of an offshore converter station and a onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station obtains a phase angle required by Park conversion through a phase-locked loop, and the offshore converter station obtains the phase angle required by Park conversion through a preset voltage frequency;
firstly, the multi-terminal direct-current transmission system applicable to the method at least comprises 3 or more converter stations, and comprises an N-land power grid and M offshore wind farms, wherein the land power grid and the offshore wind farms are connected through the direct-current power grid. Each onshore power grid and offshore wind farm are connected to a dc power grid through a flexible dc converter station, fig. 2 is a schematic diagram of a multi-terminal dc power grid including N offshore converter stations and M onshore converter stations according to an embodiment of the present invention, please refer to fig. 2.
The invention relates to a land converter station which is set to be connected with a land strong alternating current system, and the relevant electrical quantity of the ith converter station and the direct current side thereof adopts a lower corner markRepresents, for exampleExpressing the active power injected into the direct current power grid by the ith converter station whenAnd the ith land converter station is used for rectifying operation and inputting power to the direct current power grid, and the ith land converter station is used for inverting operation and absorbing power from the direct current power grid. Because the wind power plant is a passive system, the offshore converter station can be considered to be connected with a weak alternating current system, and similarly, the relevant electrical quantities of the jth converter station and the called direct current side of the jth converter station adopt lower corner marksIt is indicated, for example, that Pwj expresses the active power injected into the dc network by the j-th converter station.
The direct-current power grid of the multi-terminal direct-current power transmission system applicable to the invention has certain universality and has the following characteristics:
1. a transmission line in the direct current power grid is only connected with the two converter stations;
2. one converter station can be connected with other converter stations through a plurality of transmission lines;
3. the converter station cannot be connected with the converter station, namely, the condition that two ends of one line are the same converter station does not exist;
4. the dc grid must be connected, i.e. for any two converter stations in the dc grid, there is a path made up of transmission lines connecting the two converter stations.
At present, common multi-end systems with direct-current topological structures such as star (radiation type), ring, wind field ring, power grid ring, mesh type and the like are all suitable for the invention.
P (P is more than or equal to 2 and less than or equal to N) converter stations are selected from N land converter stations as voltage control stations, and under the action of the voltage control stations, the direct-current voltage of the direct-current power transmission network is ensured to be within the feasible region range, namely the direct-current side voltage of each converter station meets uc(·)≤umax。
The remaining (N-P) converter stations are in active/reactive power control mode.
The wind field is a passive alternating current system, so the offshore converter station connected with the offshore wind farm is used for providing stable alternating current voltage for the wind farm at a public coupling point, so that the offshore wind power can be stably sent out, and the control mode of the offshore converter station is a constant alternating current voltage mode.
Land converter station: fig. 3 is a schematic diagram of an ith land converter station according to an embodiment of the present invention, please refer to fig. 3, wherein in fig. 3, symbols represent electrical quantities as follows:
three-phase voltages and currents, respectively, of a common coupling node (PCC),in order to output a voltage for the converter station,is the included angle between the PCC voltage and the output voltage of the converter station,in order to provide a system for utilizing a direct voltage,andin order to measure the equivalent reactance for alternating current,is the converter station dc side voltage.
Collecting and measuring alternating voltage v of an alternating current side of a land converter station in a multi-terminal flexible direct current transmission system at a common coupling points(·),abcAC current i at the AC side of the converter station(·),abcDC voltage u at DC side of converter stationc(·)And a direct current ic(·)And obtaining the phase angle theta required by the angle of the grid voltage synchronous rotation dq coordinate system through the phase-locked loop(·)I.e. the phase angle theta required for Park transformation(·)。
S102, carrying out Park conversion on the electric quantity of the alternating current side of the offshore converter station and the onshore converter station respectively, acquiring the electric value of the electric quantity under a dq coordinate system of synchronous rotation of the grid voltage, and acquiring the inner ring controllers of the offshore converter station and the onshore converter station under the dq coordinate system respectively;
carrying out Park change on each electrical quantity on the alternating current side of the onshore converter station to obtain the electrical value of each electrical quantity in the grid voltage synchronous rotation dq coordinate system
And designing an inner ring controller of the converter station under the dq coordinate system as follows:
in the above formula K(·)Represents the PI controller parameter of the inner loop controller. In the above formulaIs the inner loop dq current reference value. Output variable of inner ring controllerObtaining the value under the abc coordinate system under the action of Park inverse changeWhich is the inverter reference voltage value.
The outer ring controller of the converter provides input value for the inner ring control linkThe design is as follows:
for P land converter stations with voltage control, the current reference d component is designed as follows:
in the above formulaFor the rated operating parameter design values of the multi-terminal system,for higher level control of command values, these two types of values may be considered known to the control hierarchy of the present patent design.
K in the above expression(·)Are direct voltage/reactive power PI controller parameters.The parameters are controlled for an improved droop algorithm.
From the analysis of mathematics angle voltage droop control based on Logistic, have following characteristics:
1、is PiIs a monotonically decreasing function of the argument;
2. when P is presentiThe time is → -infinity,
3. when P is presentiThe time → + ∞ times,
after the strategy is adopted, the change range of the direct-current voltage reference value meets the following requirements:
for a DC voltage, the maximum feasible value is umaxThus for kdcThe following were selected:
from the above formula, the improved droop control algorithm can ensure that the outer ring voltage reference value is maintained in the allowable feasible region class, and has a great improvement over the conventional droop control method which is specifically applicable to offshore wind power through multi-terminal direct current output.
For the remaining (N-P) converter stations in the active/reactive power control mode, the algorithm of the outer loop controller is as follows:
an offshore converter station: fig. 4 is a schematic diagram of a j-th offshore converter station according to an embodiment of the present invention, where in fig. 4, symbols represent electrical quantities as follows:three-phase voltages and currents, respectively, of a common coupling node (PCC),in order to output a voltage for the converter station,is the included angle between the PCC voltage and the output voltage of the converter station,in order to provide a system for utilizing a direct voltage,andin order to measure the equivalent reactance for alternating current,is a controllable current source of an equivalent wind farm,the equivalent capacitance of the PCC point high frequency filter and the current flowing through the filter,is the converter station dc side voltage.
Collecting and measuring alternating voltage of AC side of offshore converter station at public coupling point in multi-terminal flexible DC transmission systemAlternating current i at the alternating side of the converter station(·),abcDC voltage u at DC side of converter stationc(·)And a direct current ic(·)Since the voltage of the offshore converter station is generated directly by the converter station without synchronization with the grid voltage, the required theta for Park change can be given directly for a given ac grid frequency(·)。
Carrying out Park change on each electrical quantity on the alternating current side of the offshore converter station to obtain the electrical value of each electrical quantity in the grid voltage synchronous rotation dq coordinate system
And designing an inner ring controller of the converter station under the dq coordinate system as follows:
in the above formula K(·)Representing inner ring controlPI controller parameters of the controller. In the above formulaIs the inner loop dq current reference value. Output variable of inner ring controllerObtaining the value under the abc coordinate system under the action of Park inverse changeWhich is the inverter reference voltage value.
The outer ring controller of the converter provides input value for the inner ring control linkThe design is as follows:
for the offshore converter station, the main role is to maintain the stability of the PCC voltage, i.e. the PCC voltage, and therefore, the current reference value d component can be designed as follows:
in the above formulaFor PCC point voltage reference value, the invention sets
K in the above expression(·)Are direct voltage/reactive power PI controller parameters.Is the PCC point voltage amplitude.
And S103, respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station into the inner ring controller.
By adopting the method and the device, the voltage reference value of the converter station in the voltage control mode can be ensured to be changed within the allowable area range all the time, and the safe and stable operation of a multi-terminal system is ensured.
Fig. 5 is a schematic diagram of a droop control apparatus provided in an embodiment of the present invention, the apparatus including:
the obtaining module 501 is configured to obtain electrical quantities of an offshore converter station and a onshore converter station, where the electrical quantities include an ac voltage at a common coupling point on an ac side, an ac current on the ac side, a dc voltage and a dc current on a dc side, the onshore converter station obtains a phase angle required by Park conversion through a phase-locked loop, and the offshore converter station obtains a phase angle required by Park conversion through a preset voltage frequency;
a conversion module 502, configured to perform Park conversion on the electrical quantities at the ac sides of the offshore converter station and the onshore converter station, respectively, obtain electrical values of the electrical quantities in a dq coordinate system of grid voltage synchronous rotation, and obtain inner ring controllers of the offshore converter station and the onshore converter station in the dq coordinate system, respectively;
an input module 503, configured to input the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station to the inner ring controller, respectively.
Embodiments of the present invention also propose a storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the above-mentioned method.
Furthermore, an embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the program.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (10)
1. A droop control method suitable for offshore wind power output through multi-end direct current is characterized by comprising the following steps:
respectively acquiring electrical quantities of an offshore converter station and a onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station acquires a phase angle required by Park transformation through a phase-locked loop, and the offshore converter station acquires the phase angle required by Park transformation through a preset voltage frequency;
respectively carrying out Park conversion on the electric quantity of the alternating current side of the offshore converter station and the onshore converter station, and acquiring the electric value of the electric quantity in a grid voltage synchronous rotation dq coordinate system;
respectively acquiring inner ring controllers of the offshore converter station and the onshore converter station under a dq coordinate system;
and respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station into the inner ring controller.
2. The droop control method for offshore wind power via multi-terminal direct current transmission according to claim 1, wherein the inner ring controller of the onshore converter station in the dq coordinate system comprises:
wherein, K(·)A PI controller parameter representing the inner loop controller,for the inner loop dq current reference value,is an equivalent reactance on the alternating-current side,three-phase voltages and currents, respectively, at a common coupling node, toCarrying out Park change to obtain an electrical value under a grid voltage synchronous rotation dq coordinate systemObtaining phase angle required by Park transformation for the land converter station through a phase-locked loop, and output variable of an inner loop controllerObtaining the value under the abc coordinate system under the action of Park inverse transformationI.e. the converter station reference voltage value.
3. The droop control method for offshore wind power via multi-terminal dc output according to claim 2, wherein inputting the current reference value of the outer ring controller of the onshore converter station to the inner ring controller comprises:
the current reference value component of the voltage control station comprises:
wherein the content of the first and second substances,for the rated operating parameter design values of the multi-terminal system,for instruction values of upper control, k(·)For the parameters, k, of the DC voltage/reactive power PI controllerdc,i，For improved droop algorithm control parameters, p is the number of the land converter stations.
4. The method for controlling the droop of offshore wind energy by means of multi-terminal DC output according to claim 3, wherein said method comprisesK isdcThe value range is as follows:
5. the droop control method for offshore wind power through multi-terminal direct current output according to claim 1, wherein the inner ring controller of the offshore converter station in dq coordinate system comprises:
wherein, K(·)A PI controller parameter representing an inner loop controller,for the inner loop dq current reference value,is an equivalent reactance on the alternating-current side,three-phase voltages and currents, respectively, at a common coupling node, saidCarrying out Park change to obtain an electrical value under a grid voltage synchronous rotation dq coordinate systemObtaining a phase angle required by Park transformation for the offshore converter station through a preset voltage frequency, and outputting a variable of an inner ring controllerObtaining the value under the abc coordinate system under the action of Park inverse changeI.e. the inverter reference voltage value.
6. The droop control method for offshore wind power via multi-terminal direct current output according to claim 5, wherein the inputting of the current of the outer ring controller of the offshore converter station to the inner ring controller comprises:
the current reference value component of the offshore converter station comprises:
wherein the content of the first and second substances,is a reference value of the voltage at the PCC point,
k(·)for the dc voltage/reactive power PI controller parameters,is the PCC point voltage amplitude.
7. The droop control method suitable for offshore wind power through multi-terminal direct current output according to claim 1, wherein the method further comprises the following steps:
selecting a plurality of land converter stations from the plurality of land converter stations as a voltage control station, wherein the voltage control station is used for ensuring that the direct current side voltage of the land converter stations is not greater than the maximum voltage value;
setting the land converter stations except the voltage control station into an active power/reactive power control mode;
and the control mode of the offshore converter station is set to be a constant alternating current voltage mode.
8. A droop control apparatus, comprising:
the acquisition module is used for respectively acquiring electrical quantities of the offshore converter station and the onshore converter station, wherein the electrical quantities comprise alternating current voltage at a public coupling point on an alternating current side, alternating current on the alternating current side, direct current voltage and direct current on the direct current side, the onshore converter station acquires a phase angle required by Park conversion through a phase-locked loop, and the offshore converter station acquires a phase angle required by Park conversion through a preset voltage frequency;
the conversion module is used for respectively carrying out Park conversion on the electric quantity at the alternating current side of the offshore converter station and the onshore converter station, acquiring the electric value of the electric quantity under a dq coordinate system of synchronous rotation of the grid voltage, and respectively acquiring the inner ring controllers of the offshore converter station and the onshore converter station under the dq coordinate system;
and the input module is used for respectively inputting the current reference values of the outer ring controllers of the offshore converter station and the onshore converter station to the inner ring controller.
9. A droop control apparatus comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing the droop control method adapted for multi-terminal dc shedding of offshore wind power of any one of claims 1 to 7 when executing the computer program.
10. A computer-readable storage medium, comprising a stored computer program, wherein when the computer program runs, the computer-readable storage medium controls an apparatus to execute the droop control method for marine wind power output through multi-terminal direct current according to any one of claims 1 to 7.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910811647.5A CN110601247A (en) | 2019-08-30 | 2019-08-30 | Droop control method suitable for multi-end direct current sending of offshore wind power |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910811647.5A CN110601247A (en) | 2019-08-30 | 2019-08-30 | Droop control method suitable for multi-end direct current sending of offshore wind power |
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