Primary frequency modulation method and device for flexible direct-current power transmission system

Abstract

The invention provides a primary frequency modulation method and device for a flexible DC power transmission system, and relates to the technical field of electrical engineering. The method comprises the following steps: acquiring an alternating current side power grid frequency of a flexible direct current receiving end converter station, preprocessing the alternating current side power grid frequency, and sending the preprocessed alternating current side power grid frequency to a flexible direct current sending end converter station in an inter-station communication mode; the flexible direct current transmitting end converter station receives the preprocessed alternating current side power grid frequency and controls the alternating current voltage of the flexible direct current transmitting end according to the preprocessed alternating current side power grid frequency in a constant alternating current voltage control mode; and in response to a flexible direct transmitting end frequency variation sensed by a power supply connected with the flexible direct transmitting end converter station, adjusting a flexible direct transmitting end active power variation output by primary frequency modulation so as to respond to the flexible direct transmitting end frequency variation. According to the method and the device provided by the embodiment of the invention, the frequency stability of the receiving-end power grid can be effectively improved.

Description

A method and apparatus for primary frequency regulation of a flexible DC transmission system Technical Field

[0001] This invention relates to the field of electrical engineering technology, specifically to a primary frequency regulation method and apparatus for a flexible DC transmission system. Background Technology

[0002] The receiving-end converter station and the sending-end converter station are the core components of the flexible DC transmission system, respectively undertaking the key functions of power conversion and distribution.

[0003] Compared with traditional DC transmission technology, flexible DC transmission does not have reactive power compensation and commutation failure problems. It can independently adjust active and reactive power, provide power to passive networks, and provide strong support for the transmission of new energy to remote areas.

[0004] However, as the scale of new energy transmission via flexible DC continues to expand, the output and number of synchronous generator units in the receiving-end power grid gradually decrease, exhibiting problems such as low inertia, weak damping, and poor frequency regulation capability. Furthermore, the flexible DC transmission under the traditional control strategy decouples the sending-end power grid and the receiving-end power grid, further weakening the frequency support capability of the power grid, which in turn leads to a reduction in the frequency regulation capability of the receiving-end power grid. Summary of the Invention

[0005] To address the problems in the prior art, embodiments of the present invention provide a primary frequency regulation method and apparatus for a flexible DC transmission system, which can at least partially solve the problems existing in the prior art.

[0006] On one hand, this invention proposes a primary frequency regulation method for a flexible DC transmission system, which includes a flexible DC receiving-end converter station and a flexible DC sending-end converter station. The primary frequency regulation method for the flexible DC transmission system includes:

[0007] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0008] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0009] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0010] The preprocessing of the AC power grid frequency includes:

[0011] The sampling delay of the AC power grid frequency is calculated to obtain the measured value of the AC power grid frequency.

[0012] The AC-side grid frequency measurement value is low-pass filtered based on the transmission frequency of inter-station communication to obtain the pre-processed AC-side grid frequency.

[0013] The step of controlling the AC voltage at the flexible direct-transmission end based on the pre-processed AC grid frequency and using a constant AC voltage control method includes:

[0014] The pre-processed AC grid frequency is subjected to a dead-zone limiting process, and the processed AC grid frequency is input to the flexible DC converter; so that the flexible DC converter can control the AC voltage at the flexible DC transmission end using a constant AC voltage control method.

[0015] The method of controlling the AC voltage at the flexible direct-transmission terminal using a constant AC voltage control method includes:

[0016] The flexible DC converter obtains the active power reference value of the flexible DC transmission end converter station based on the processed AC side grid frequency. The active power reference value of the flexible DC transmission end converter station, the active power measurement value of the flexible DC transmission end, the change in active power output of the primary frequency regulation, the damping torque coefficient, the speed reference value, the speed measurement value and the inertia time constant, the AC voltage reference value of the flexible DC transmission end, the effective value of the AC voltage of the flexible DC transmission end, and the peak value of the reference voltage are used as control parameters for the constant AC voltage control mode to control the AC voltage of the flexible DC transmission end.

[0017] The primary frequency regulation method for the flexible DC transmission system, following the step of adjusting the change in active power at the flexible DC transmission end of the primary frequency regulation output in response to the change in frequency at the flexible DC transmission end, further includes:

[0018] The amount of power change transmitted to the receiving-end grid is determined based on the adjusted change in active power at the flexible direct transmission end, so as to support the frequency stability of the receiving-end grid through the power change in the receiving-end grid.

[0019] The primary frequency regulation method of the flexible DC transmission system further includes:

[0020] The frequency stability of the receiving-end power grid was verified based on the preset simulation model.

[0021] On one hand, this invention proposes a primary frequency regulation device for a flexible DC transmission system, the flexible DC transmission system including a flexible DC receiving-end converter station and a flexible DC sending-end converter station, the primary frequency regulation device of the flexible DC transmission system comprising:

[0022] The preprocessing unit is used to obtain the AC-side grid frequency of the flexible DC receiving-end converter station, preprocess the AC-side grid frequency, and send the preprocessed AC-side grid frequency to the flexible DC sending-end converter station using inter-station communication.

[0023] The control unit is used to receive the pre-processed AC grid frequency through the flexible direct transmission converter station, and control the AC voltage of the flexible direct transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0024] The adjustment unit is used to adjust the change in active power of the primary frequency modulation output of the flexible direct transmission terminal in response to the change in the frequency of the flexible direct transmission terminal sensed by the power supply connected to the flexible direct transmission terminal converter station.

[0025] In another aspect, embodiments of the present invention provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the following method:

[0026] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0027] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0028] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0029] This invention provides a computer-readable storage medium, comprising:

[0030] The computer-readable storage medium stores a computer program that, when executed by a processor, implements the following method:

[0031] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0032] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0033] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0034] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements the following method:

[0035] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0036] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0037] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0038] The primary frequency regulation method and apparatus for a flexible DC transmission system provided in this invention acquires the AC-side grid frequency of the receiving-end converter station, preprocesses the AC-side grid frequency, and transmits the preprocessed AC-side grid frequency to the sending-end converter station via inter-station communication. The sending-end converter station receives the preprocessed AC-side grid frequency and controls the AC voltage of the sending end based on the preprocessed AC-side grid frequency and using a constant AC voltage control method. In response to the frequency change of the sending end sensed by the power supply connected to the sending-end converter station, the active power change of the primary frequency regulation output of the sending end is adjusted to respond to the frequency change of the sending end, which can effectively improve the frequency stability of the receiving-end grid. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0040] Figure 1 is a flowchart illustrating a primary frequency regulation method for a flexible DC transmission system according to an embodiment of the present invention.

[0041] Figure 2 is a schematic diagram of the transmission process of power at the transmitting end, power at the receiving end, and frequency provided in an embodiment of the present invention.

[0042] Figure 3 is a schematic diagram illustrating the constant AC voltage control method provided in an embodiment of the present invention.

[0043] Figure 4 is a schematic diagram illustrating the frequency change curve of the simulation verification provided in the embodiment of the present invention.

[0044] Figure 5 is a schematic diagram of the structure of a primary frequency regulation device for a flexible DC transmission system provided in an embodiment of the present invention.

[0045] Figure 6 is a schematic diagram of the physical structure of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0047] Figure 1 is a flowchart illustrating a primary frequency regulation method for a flexible DC transmission system according to an embodiment of the present invention. As shown in Figure 1, the primary frequency regulation method for a flexible DC transmission system provided in this embodiment is applied to the flexible DC transmission system, which includes a flexible DC receiving-end converter station and a flexible DC sending-end converter station. The primary frequency regulation method for the flexible DC transmission system includes:

[0048] Step S1: Obtain the AC-side grid frequency of the flexible DC receiving-end converter station, preprocess the AC-side grid frequency, and send the preprocessed AC-side grid frequency to the flexible DC sending-end converter station using inter-station communication.

[0049] Step S2: The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0050] Step S3: In response to the change in the frequency of the flexible direct transmission terminal sensed by the power supply connected to the flexible direct transmission terminal converter station, adjust the change in the active power of the primary frequency modulation output of the flexible direct transmission terminal to respond to the change in the frequency of the flexible direct transmission terminal.

[0051] In step S1 above, the device acquires the AC-side grid frequency of the flexible DC receiving-end converter station, preprocesses the AC-side grid frequency, and transmits the preprocessed AC-side grid frequency to the flexible DC sending-end converter station via inter-station communication. The device can be a computer device executing this method. The acquisition, storage, use, and processing of data in this application's technical solution all comply with relevant regulations. The preprocessing of the AC-side grid frequency includes:

[0052] The sampling delay of the AC power grid frequency is calculated to obtain the measured value of the AC power grid frequency.

[0053] The AC-side power grid frequency measurement is low-pass filtered based on the inter-station communication transmission frequency to obtain the preprocessed AC-side power grid frequency. The AC-side power grid frequency fr is a continuous function of time, and its measured value, namely the AC-side power grid frequency measurement value frm, is discrete information calculated after sampling delay.

[0054] According to the Nyquist sampling theorem, the AC power grid frequency frmh needs to be preprocessed by low-pass filtering frm based on the inter-station communication transmission frequency Fs. The filter cutoff frequency should be lower than Fs / 2 to avoid frequency aliasing during communication.

[0055] Inter-station communication methods include, but are not limited to, optical fiber and power line carrier.

[0056] In step S2 above, the flexible direct-transmission converter station receives the pre-processed AC-side grid frequency and controls the flexible direct-transmission AC voltage according to the pre-processed AC-side grid frequency using a constant AC voltage control method. The step of controlling the flexible direct-transmission AC voltage according to the pre-processed AC-side grid frequency using a constant AC voltage control method includes:

[0057] The pre-processed AC grid frequency is subjected to a dead-zone limiting process, and the processed AC grid frequency is then input to the flexible DC converter. This allows the flexible DC converter to control the AC voltage at the flexible DC transmission end using a constant AC voltage control method. As shown in Figure 2, after the dead-zone limiting process, constant AC voltage control can be achieved through the flexible DC converter.

[0058] The method of controlling the AC voltage at the flexible direct-transmission terminal using a constant AC voltage control method includes:

[0059] The flexible DC converter obtains the active power reference value of the flexible DC-DC transmission terminal converter station based on the processed AC-side grid frequency. The active power reference value of the flexible DC-DC transmission terminal converter station, the measured active power value of the flexible DC-DC transmission terminal, the change in active power output from the primary frequency regulation, the damping torque coefficient, the speed reference value, the measured speed value and inertia time constant, the AC voltage reference value of the flexible DC-DC transmission terminal, the effective value of the AC voltage of the flexible DC-DC transmission terminal, and the peak value of the reference voltage are used as control parameters for the constant AC voltage control mode to control the AC voltage of the flexible DC-DC transmission terminal. The control mode is shown in Figure 3, and is explained below with reference to the following formula:

[0060]

[0061] Among them, P refThe active power reference value for the flexible direct-transmission converter station is the change in active power output from the primary frequency regulation. K is the frequency modulation coefficient. Ps represents the deviation of the receiving-end grid frequency from 50Hz, Ps is the measured active power value of the primary frequency regulation output at the flexible direct transmission end, and D is the damping torque coefficient. This is a reference value for rotational speed. For speed measurement value f is the power frequency, T j Uref is the inertial time constant, Usrms is the AC voltage reference value of the flexible direct transmission terminal, and E0 is the peak value of the reference voltage.

[0062] The delay between the sending-end grid frequency fs and the receiving-end grid frequency fr is in the hundreds of milliseconds.

[0063] In step S3 above, the device responds to the change in the frequency of the flexible direct-transmission power supply sensed by the power source connected to the flexible direct-transmission converter station, and adjusts the change in the active power output of the primary frequency regulation of the flexible direct-transmission power supply to respond to the change in the frequency of the flexible direct-transmission power supply. When the frequency of the receiving-end grid decreases, the sending-end power supply increases the output of active power; when the frequency of the receiving-end grid increases, the sending-end power supply decreases the output of active power.

[0064] After the step of adjusting the change in active power at the flexible DC transmission end of the primary frequency regulation output in response to the change in frequency at the flexible DC transmission end, the primary frequency regulation method of the flexible DC transmission system further includes:

[0065] The amount of power change transmitted to the receiving-end grid is determined based on the adjusted change in active power at the flexible direct transmission end, so as to support the frequency stability of the receiving-end grid through the power change in the receiving-end grid.

[0066] The power supply at the sending end adjusts its output power in response to frequency changes. Since the sending end adopts a "constant AC voltage" control method, the power changes of the power supply are fully absorbed by the converter station at the flexible direct-transmission end and sent to the receiving end grid through the DC line, thereby supporting the frequency stability of the receiving end grid.

[0067] The following is a further explanation in conjunction with Figure 2:

[0068] The deviation of the receiving-end power grid frequency from 50Hz, For the frequency deviation of the flexible direct transmission system, This refers to the change in active power output when the power supply participates in primary frequency regulation. This refers to the change in power transmitted to the receiving-end power grid.

[0069] Existing communication methods directly transmit the frequency of the flexible direct current transmission station to the new energy power generation unit via communication. However, the new energy power generation unit is large in scale, with a large number of communications and long distances, requiring additional communication devices and making control complex. The method proposed in this invention utilizes the communication device within the flexible direct current transmission station to transmit the frequency of the receiving end grid to the flexible direct current transmission end grid. After the sending end frequency changes, the power supply with primary frequency regulation function can adjust the power output power.

[0070] The primary frequency regulation method of the flexible DC transmission system also includes:

[0071] The frequency stability of the receiving-end power grid was verified based on a pre-set simulation model. The explanation is as follows:

[0072] The communication frequency between the flexible DC converter stations is 100Hz, the total delay for measurement and communication is set to 200ms, the frequency modulation dead zone is set to ±0.02Hz, and the AC voltage frequency limit at the flexible DC transmission end is 49 to 51Hz. The base power is set to 500MW, the frequency characteristic of the receiving-end grid is set to 200MW / Hz, and the time constant is set to 1s. At t=1s, the load of the receiving-end grid increases by 40MW, and the frequency change curve is shown in Figure 4. Without frequency modulation measures, the grid frequency drops and then stabilizes at 49.8Hz; after one frequency modulation using the proposed method, the grid frequency drops to a minimum of 49.91Hz and then gradually stabilizes around 49.94Hz. Simulation results show that the proposed method enables the power supply at the flexible DC transmission end to respond to the frequency changes of the receiving-end grid and adjust its output power to support the receiving-end grid.

[0073] The primary frequency regulation method for flexible DC transmission systems provided in this invention has the following beneficial technical effects:

[0074] By transmitting the frequency information of the receiving-end power grid to the sending-end converter station, the AC voltage frequency of the sending-end power grid is controlled, thereby enabling the sending-end power supply to respond to load changes in the receiving-end power grid and improving the frequency stability level.

[0075] The primary frequency regulation method for a flexible DC transmission system provided in this invention obtains the AC-side grid frequency of the receiving-end converter station, preprocesses the AC-side grid frequency, and transmits the preprocessed AC-side grid frequency to the sending-end converter station via inter-station communication. The sending-end converter station receives the preprocessed AC-side grid frequency and controls the AC voltage of the sending end based on the preprocessed AC-side grid frequency and using a constant AC voltage control method. In response to the frequency change of the sending end sensed by the power supply connected to the sending-end converter station, the active power change of the primary frequency regulation output of the sending end is adjusted to respond to the frequency change of the sending end, which can effectively improve the frequency stability of the receiving-end grid.

[0076] In the above optional embodiments, the preprocessing of the AC-side power grid frequency includes:

[0077] The sampling delay of the AC power grid frequency is calculated to obtain the measured value of the AC power grid frequency; this can be referred to the above embodiment for explanation, and will not be repeated here.

[0078] The AC-side grid frequency measurement value is low-pass filtered based on the inter-station communication transmission frequency to obtain the pre-processed AC-side grid frequency. This can be referred to the above embodiment for further explanation and will not be repeated here.

[0079] In the above optional embodiments, the step of controlling the AC voltage at the flexible direct transmission end based on the preprocessed AC grid frequency and using a constant AC voltage control method includes:

[0080] The pre-processed AC grid frequency is subjected to a dead-zone limiting process, and the processed AC grid frequency is then input to the flexible DC converter. This allows the flexible DC converter to control the AC voltage at the flexible DC transmission end using a constant AC voltage control method. The above embodiments can be referred to for further explanation, and will not be repeated here.

[0081] In the above optional embodiments, the control of the AC voltage at the flexible direct-transmission terminal using a constant AC voltage control method includes:

[0082] The flexible DC converter obtains the active power reference value of the flexible DC-DC transmission terminal converter station based on the processed AC-side grid frequency. The active power reference value of the flexible DC-DC transmission terminal converter station, the measured active power value of the flexible DC-DC transmission terminal, the change in active power output from the primary frequency regulation, the damping torque coefficient, the speed reference value, the measured speed value and the inertia time constant, the AC voltage reference value of the flexible DC-DC transmission terminal, the effective value of the AC voltage of the flexible DC-DC transmission terminal, and the peak value of the reference voltage are used as control parameters for the constant AC voltage control mode to control the AC voltage of the flexible DC-DC transmission terminal. This can be referred to the above embodiment for explanation, and will not be repeated here.

[0083] In the above optional embodiments, after the step of adjusting the change in active power at the flexible DC transmission end of the primary frequency regulation output in response to the change in frequency at the flexible DC transmission end, the primary frequency regulation method of the flexible DC transmission system further includes:

[0084] The power change transmitted to the receiving-end grid is determined based on the adjusted change in active power at the flexible direct transmission end, so as to support the frequency stability of the receiving-end grid through the power change in the receiving-end grid. This can be referred to the above embodiments for explanation, and will not be repeated here.

[0085] In the above optional embodiments, the primary frequency regulation method of the flexible DC transmission system further includes:

[0086] The frequency stability of the receiving-end power grid was verified using a preset simulation model. This can be referred to the above embodiments for explanation, and will not be repeated here.

[0087] Figure 5 is a structural schematic diagram of a primary frequency regulation device for a flexible DC transmission system according to an embodiment of the present invention. As shown in Figure 5, the primary frequency regulation device for a flexible DC transmission system provided in this embodiment is applied to the flexible DC transmission system, which includes a flexible DC receiving-end converter station and a flexible DC sending-end converter station. The primary frequency regulation device for the flexible DC transmission system includes a preprocessing unit 501, a control unit 502, and an adjustment unit 503, wherein:

[0088] The preprocessing unit 501 is used to acquire the AC-side grid frequency of the flexible DC receiving-end converter station, preprocess the AC-side grid frequency, and send the preprocessed AC-side grid frequency to the flexible DC sending-end converter station using inter-station communication; the control unit 502 is used to receive the preprocessed AC-side grid frequency through the flexible DC sending-end converter station, and control the AC voltage of the flexible DC sending end according to the preprocessed AC-side grid frequency and using a constant AC voltage control method; the adjustment unit 503 is used to adjust the change in the active power of the flexible DC sending end output by the primary frequency modulation in response to the change in the frequency of the flexible DC sending end sensed by the power supply connected to the flexible DC sending-end converter station.

[0089] Specifically, the preprocessing unit 501 in the device is used to acquire the AC-side grid frequency of the flexible DC receiving-end converter station, preprocess the AC-side grid frequency, and send the preprocessed AC-side grid frequency to the flexible DC sending-end converter station using inter-station communication; the control unit 502 is used to receive the preprocessed AC-side grid frequency through the flexible DC sending-end converter station, and control the AC voltage of the flexible DC sending end according to the preprocessed AC-side grid frequency and using a constant AC voltage control method; the adjustment unit 503 is used to adjust the change in the active power of the flexible DC sending end in the primary frequency modulation output in response to the change in the frequency of the flexible DC sending end sensed by the power supply connected to the flexible DC sending-end converter station.

[0090] The primary frequency regulation device for a flexible DC transmission system provided in this invention acquires the AC-side grid frequency of the receiving-end converter station, preprocesses the AC-side grid frequency, and transmits the preprocessed AC-side grid frequency to the sending-end converter station via inter-station communication. The sending-end converter station receives the preprocessed AC-side grid frequency and controls the AC voltage of the sending end based on the preprocessed AC-side grid frequency and using a constant AC voltage control method. In response to the frequency change of the sending end sensed by the power supply connected to the sending-end converter station, the device adjusts the change in active power output of the primary frequency regulation device to respond to the frequency change, thereby effectively improving the frequency stability of the receiving-end grid.

[0091] The embodiments of the present invention provide a primary frequency regulation device for a flexible DC transmission system, which can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0092] Figure 6 is a schematic diagram of the physical structure of a computer device provided in an embodiment of the present invention. As shown in Figure 6, the computer device includes: a memory 601, a processor 602, and a computer program stored in the memory 601 and executable on the processor 602. When the processor 602 executes the computer program, it implements the following method:

[0093] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0094] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0095] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0096] This embodiment discloses a computer program product, which includes a computer program that, when executed by a processor, implements the following method:

[0097] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0098] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0099] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0100] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the following method:

[0101] The AC-side grid frequency of the flexible DC receiving-end converter station is obtained, the AC-side grid frequency is preprocessed, and the preprocessed AC-side grid frequency is sent to the flexible DC sending-end converter station using inter-station communication.

[0102] The flexible direct-transmission converter station receives the pre-processed AC grid frequency and controls the AC voltage of the flexible direct-transmission station according to the pre-processed AC grid frequency and using a constant AC voltage control method.

[0103] In response to the frequency change of the flexible direct-transmission terminal sensed by the power supply connected to the flexible direct-transmission terminal converter station, the active power change of the primary frequency modulation output of the flexible direct-transmission terminal is adjusted to respond to the frequency change of the flexible direct-transmission terminal.

[0104] Compared with existing technologies, the primary frequency regulation method for flexible DC transmission systems provided in this invention obtains the AC-side grid frequency of the receiving-end converter station, preprocesses the AC-side grid frequency, and transmits the preprocessed AC-side grid frequency to the sending-end converter station via inter-station communication. The sending-end converter station receives the preprocessed AC-side grid frequency and controls the AC voltage of the sending end based on the preprocessed AC-side grid frequency using a constant AC voltage control method. In response to the frequency change of the sending end sensed by the power supply connected to the sending-end converter station, the active power change of the primary frequency regulation output of the sending end is adjusted to respond to the frequency change, thereby effectively improving the frequency stability of the receiving-end grid.

[0105] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0107] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0108] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0109] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0110] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A primary frequency regulation method for a flexible DC transmission system, wherein the primary frequency regulation method for the flexible DC transmission system is applied to the flexible DC transmission system, the flexible DC transmission system comprising a flexible DC receiving-end converter station and a flexible DC sending-end converter station, characterized in that, include: The AC grid frequency of the receiving-end converter station is acquired, preprocessed, and transmitted to the sending-end converter station via inter-station communication. The sending-end converter station receives the preprocessed AC grid frequency and controls the AC voltage of the sending end based on the preprocessed AC grid frequency and a constant AC voltage control method. In response to the frequency change of the sending end sensed by the power supply connected to the sending-end converter station, the active power change of the primary frequency modulation output of the sending end is adjusted to respond to the frequency change.

2. The primary frequency regulation method for a flexible DC transmission system according to claim 1, characterized in that, The preprocessing of the AC-side power grid frequency includes: calculating the sampling delay of the AC-side power grid frequency to obtain a measured value of the AC-side power grid frequency; and performing low-pass filtering on the measured value of the AC-side power grid frequency based on the transmission frequency of inter-station communication to obtain a preprocessed AC-side power grid frequency.

3. The primary frequency regulation method for a flexible DC transmission system according to claim 1, characterized in that, The step of controlling the AC voltage at the flexible DC-DC converter based on the pre-processed AC grid frequency and using a constant AC voltage control method includes: performing dead-zone limiting processing on the pre-processed AC grid frequency and inputting the processed AC grid frequency to the flexible DC-DC converter; so that the flexible DC-DC converter can control the AC voltage at the flexible DC-DC converter using a constant AC voltage control method.

4. The primary frequency regulation method for a flexible DC transmission system according to claim 3, characterized in that, The method of controlling the AC voltage of the flexible direct-transmission terminal using a constant AC voltage control mode includes: the flexible direct-transmission converter obtaining the active power reference value of the flexible direct-transmission terminal converter station based on the processed AC side grid frequency, and using the active power reference value of the flexible direct-transmission terminal converter station, the active power measurement value of the flexible direct-transmission terminal, the change in active power output of the primary frequency regulation, the damping torque coefficient, the speed reference value, the speed measurement value and the inertia time constant, the AC voltage reference value of the flexible direct-transmission terminal, the effective value of the AC voltage of the flexible direct-transmission terminal, and the peak value of the reference voltage as control parameters of the constant AC voltage control mode to control the AC voltage of the flexible direct-transmission terminal.

5. The primary frequency regulation method for a flexible DC transmission system according to any one of claims 1 to 4, characterized in that, After the step of adjusting the change in active power at the flexible DC transmission end of the primary frequency regulation output in response to the change in frequency at the flexible DC transmission end, the primary frequency regulation method of the flexible DC transmission system further includes: determining the change in power transmitted to the receiving-end grid based on the adjusted change in active power at the flexible DC transmission end, so as to support the frequency stability of the receiving-end grid through the change in power at the receiving-end grid.

6. The primary frequency regulation method for a flexible DC transmission system according to claim 5, characterized in that, The primary frequency regulation method of the flexible DC transmission system also includes: verifying the frequency stability of the receiving-end power grid according to a preset simulation model.

7. A primary frequency regulation device for a flexible DC transmission system, wherein the primary frequency regulation device is applied to the flexible DC transmission system, the flexible DC transmission system comprising a flexible DC receiving-end converter station and a flexible DC sending-end converter station, characterized in that, include: The preprocessing unit is used to acquire the AC-side grid frequency of the flexible DC receiving-end converter station, preprocess the AC-side grid frequency, and send the preprocessed AC-side grid frequency to the flexible DC sending-end converter station via inter-station communication; the control unit is used to receive the preprocessed AC-side grid frequency through the flexible DC sending-end converter station, and control the AC voltage of the flexible DC sending end based on the preprocessed AC-side grid frequency and using a constant AC voltage control method; the adjustment unit is used to adjust the change in the active power of the flexible DC sending end output at the primary frequency modulation stage in response to the change in the frequency of the flexible DC sending end sensed by the power supply connected to the flexible DC sending-end converter station.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method of any one of claims 1 to 6.

10. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method of any one of claims 1 to 6.

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