Grid-forming control method and system applicable to flexible direct-current power transmission system

Abstract

The present application discloses a grid-forming control method and system applicable to a flexible direct-current power transmission system, and is applied in the technical field of power electronics. The method comprises: acquiring an active power control quantity and a reactive power control quantity of a flexible direct-current power transmission system, wherein the active power control quantity comprises an actual direct-current voltage value or an actual active power value, and the reactive power control quantity comprises an actual reactive power value or an alternating-current voltage amplitude reference value; on the basis of the active power control quantity, generating a valve voltage phase reference value; on the basis of the reactive power control quantity, generating a valve voltage amplitude reference value; on the basis of the valve voltage phase reference value and the valve voltage amplitude reference value, generating a three-phase valve voltage reference value; and on the basis of the three-phase valve voltage reference value, controlling a converter. A grid-forming control strategy provided in the present invention features a simple structure, a fast response speed and a good stability, and can exhibit voltage source characteristics under all operating conditions, thereby providing fast and reliable frequency and voltage support for a power grid under various complex operating conditions such as frequency variations and phase jumps.

Description

A grid-type control method and system applicable to flexible DC transmission systems

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 202410841686.0, filed on June 27, 2024, entitled “A Grid-Type Control Method and System Applicable to Flexible DC Transmission Systems”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of power electronics technology, specifically to a grid-type control method and system applicable to flexible DC transmission systems. Background Technology

[0004] Flexible direct current (DC) transmission technology (hereinafter referred to as "flexible DC") adopts fully controlled power electronic converters, possessing outstanding advantages such as flexible control and compatibility with both active and passive grids. It is a crucial solution for addressing challenges such as large-scale renewable energy transmission, grid interconnection, and passive grid power supply. Traditional flexible DC control employs a "grid-following" control strategy, which cannot provide active power support when grid disturbances occur. With the increasing cleanliness and power electronics of power systems, grid strength is decreasing. To improve the frequency and voltage stability of the system under disturbances, a "grid-forming" control strategy for flexible DC has been proposed in recent years.

[0005] Grid control enables power electronic equipment to exhibit voltage source characteristics similar to traditional synchronous generators, allowing flexible DC systems to provide inertial frequency and dynamic voltage support to the power grid. This is a crucial breakthrough for solving the stability and reliability problems of new power systems and improving the absorption of new energy sources.

[0006] The actual operating conditions of the power grid are complex and varied. Traditional grid-type control adopts a voltage and current dual-loop structure. Due to the existence of the current inner loop, it is impossible to maintain the voltage source characteristics under all operating conditions, making it difficult to balance the stable design of the controller and the system support performance requirements. Summary of the Invention

[0007] To overcome the shortcomings of traditional grid-type control systems, such as the inability to maintain full-condition voltage source characteristics due to the presence of an inner current loop, and the difficulty in balancing controller stability design with system support performance requirements, this invention provides a grid-type control method suitable for flexible DC transmission systems. The method includes:

[0008] The active and reactive control quantities of the flexible DC transmission system are obtained. The active control quantities include the actual DC voltage value or the actual active power value, and the reactive control quantities include the actual reactive power value or the AC voltage amplitude reference value.

[0009] Based on the active power control quantity, generate a valve voltage phase reference value;

[0010] Based on the reactive power control quantity, generate a reference value for the valve voltage amplitude;

[0011] Based on the valve voltage phase reference value and the threshold voltage amplitude reference value, a three-phase valve voltage reference value is generated;

[0012] The converter is controlled based on the three-phase valve voltage reference value.

[0013] Optionally, generating the valve voltage phase reference value based on the active power control quantity includes:

[0014] Based on the active power control quantity and the reference active power control quantity, generate an active power control quantity deviation value; based on the active power control quantity deviation value, generate a frequency deviation value;

[0015] Based on the frequency deviation value and the rated frequency value, determine the initial valve voltage phase reference value;

[0016] Based on the active control quantity deviation value, generate the phase feedforward compensation value;

[0017] The phase feedforward compensation value is superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value.

[0018] Optionally, the active power control quantity includes the actual DC voltage value, and the reference active power control quantity includes a DC voltage reference value;

[0019] The step of generating an active power control deviation value based on the active power control quantity and the reference active power control quantity; and generating a frequency deviation value based on the active power control deviation value, includes:

[0020] The DC voltage deviation value is determined based on the actual DC voltage value and the DC voltage reference value;

[0021] The frequency deviation value is generated based on the DC voltage deviation value.

[0022] Optionally, the active power control quantity includes the actual active power value, and the reference active power control quantity includes the active power reference value;

[0023] The step of generating an active power control deviation value based on the active power control quantity and the reference active power control quantity; and generating a frequency deviation value based on the active power control deviation value, includes:

[0024] The active power deviation value is determined based on the actual active power value and the active power reference value.

[0025] The frequency deviation value is generated based on the active power deviation value.

[0026] Optionally, the step of superimposing the phase feedforward compensation value onto the initial valve voltage phase reference value to generate the valve voltage phase reference value includes:

[0027] Subtracting the AC side voltage phase from the initial valve voltage phase reference value yields the AC voltage phase deviation value; the AC side voltage phase includes the AC side grid connection point voltage phase or the transformer valve side voltage phase.

[0028] If the AC voltage phase deviation value exceeds the set phase deviation value, then based on the difference between the AC voltage phase deviation value and the set phase deviation value, active power control quantity compensation value, frequency compensation value and phase compensation value are generated.

[0029] Compensation is performed based on the phase feedforward compensation value, the active power control quantity compensation value, the frequency compensation value, and the phase compensation value to generate a valve voltage phase reference value.

[0030] Optionally, generating a valve voltage amplitude reference value based on the reactive power control quantity includes:

[0031] Based on the actual reactive power value and the reactive power reference value, a reactive power deviation value is generated; based on the reactive power deviation value and the rated AC voltage amplitude, a valve voltage amplitude reference value is generated.

[0032] Alternatively, a valve voltage amplitude reference value can be generated based on the AC voltage amplitude reference value.

[0033] Optionally, controlling the converter based on the three-phase valve voltage reference value includes:

[0034] The three-phase valve voltage reference value is used as the voltage reference value of the modulator, and a drive signal for controlling the converter is generated based on the modulator.

[0035] The converter is controlled using the drive signal.

[0036] On the other hand, the present invention also provides a grid-type control system suitable for flexible DC transmission systems, comprising:

[0037] The acquisition module is configured to acquire active control quantities and reactive control quantities of the flexible DC transmission system. The active control quantities include actual DC voltage values ​​or actual active power values, and the reactive control quantities include actual reactive power values ​​or AC voltage amplitude reference values.

[0038] The generation module is configured to generate valve voltage phase reference values ​​based on the active power control quantities; generate valve voltage amplitude reference values ​​based on the reactive power control quantities; and generate three-phase valve voltage reference values ​​based on the valve voltage phase reference values ​​and the valve voltage amplitude reference values.

[0039] The control module is configured to control the converter based on the reference value of the three-phase valve voltage.

[0040] On the other hand, the present invention also provides a computer device, characterized in that it includes: one or more processors;

[0041] The processor is configured to store one or more programs;

[0042] When the one or more programs are executed by the one or more processors, the grid-type control method applicable to flexible DC transmission systems described above is implemented.

[0043] On the other hand, the present invention also provides a computer-readable storage medium, characterized in that it stores a computer program thereon, which, when executed, implements the grid-type control method applicable to flexible DC transmission systems as described in any one of the above.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] This invention provides a grid-based control method applicable to flexible DC transmission systems, comprising: acquiring active and reactive power control quantities of the flexible DC transmission system, wherein the active power control quantities include actual DC voltage values ​​or actual active power values, and the reactive power control quantities include actual reactive power values ​​or AC voltage amplitude reference values; generating valve voltage phase reference values ​​based on the active power control quantities; generating valve voltage amplitude reference values ​​based on the reactive power control quantities; generating three-phase valve voltage reference values ​​based on the valve voltage phase reference values ​​and valve voltage amplitude reference values; and controlling the converter based on the three-phase valve voltage reference values. The grid-based control strategy proposed in this invention has a simple structure, fast response speed, and good stability, and can exhibit full-condition voltage source characteristics, providing fast and reliable frequency and voltage support for the power grid under various complex operating conditions such as frequency changes and phase jumps. Attached Figure Description

[0046] Figure 1 is a schematic flowchart of the grid-type control method applicable to flexible DC transmission systems of the present invention;

[0047] Figure 2 is a schematic diagram of the grid-type control structure of the new energy flexible DC power transmission system of the present invention;

[0048] Figure 3 is a schematic diagram of the control principle of the present invention based on generating compensation values ​​by phase deviation;

[0049] Figure 4 is a schematic diagram of the grid-type flexible DC control effect under power grid frequency changes according to the present invention;

[0050] Figure 5 is a schematic diagram of the grid-type flexible DC control effect under power grid frequency changes according to the present invention;

[0051] Figure 6 is a schematic diagram of the grid-type flexible DC control effect under the change of grid phase angle according to the present invention;

[0052] Figure 7 is a schematic diagram of the grid-type flexible DC control effect under the change of power grid phase angle according to the present invention;

[0053] Figure 8 is a schematic diagram of the grid-type flexible DC control effect under the change of grid voltage amplitude according to the present invention;

[0054] Figure 9 is a schematic diagram of the grid-type flexible DC control effect under the change of grid voltage amplitude according to the present invention;

[0055] Figure 10 is a schematic diagram of the structure of the regional refined risk prediction system for power grids under extreme weather conditions according to the present invention. Detailed Implementation

[0056] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0057] Example 1:

[0058] This invention provides a grid-type control method suitable for flexible DC transmission systems, the flowchart of which is shown in Figure 1, including:

[0059] Step 101: Obtain the active and reactive control quantities of the flexible DC transmission system. The active control quantities include the actual DC voltage value or the actual active power value, and the reactive control quantities include the actual reactive power value or the AC voltage amplitude reference value.

[0060] Step 102: Generate valve voltage phase reference values ​​based on active control variables.

[0061] Step 103: Generate reference values ​​for valve voltage amplitude based on reactive power control quantities.

[0062] Step 104: Generate three-phase valve voltage reference values ​​based on valve voltage phase reference values ​​and valve voltage amplitude reference values.

[0063] Step 105: Control the converter according to the three-phase valve voltage reference value.

[0064] Compared to the traditional grid-type voltage and current dual-loop control strategy, the embodiments of this invention adopt a single-loop control structure based on active and reactive power control quantities. It features simple structure, fast response speed, and good stability, and can present voltage source characteristics under all operating conditions. It has good adaptability to various complex operating conditions of the power grid and provides fast and reliable frequency and voltage support for the power grid under various complex operating conditions such as frequency changes and phase jumps. This helps to improve the new energy carrying capacity and grid stability of the new power system.

[0065] The active power control quantities of the flexible DC transmission system in step 101 above include the actual DC voltage value or the actual active power value, which are used to generate the valve voltage phase reference value. The reactive power control quantities of the DC transmission system include the actual reactive power value or the actual voltage amplitude reference value, which are used to generate the valve voltage amplitude reference value.

[0066] In one implementation, in step 102 above, an active power control quantity deviation value is generated based on the active power control quantity and a reference active power control quantity; a frequency deviation value is generated based on the active power control quantity deviation value; an initial valve voltage phase reference value is determined based on the frequency deviation value and the rated frequency value; a phase feedforward compensation value is generated based on the active power control quantity deviation value; and the phase feedforward compensation value is superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value. This implementation generates phase feedforward compensation based on the active power control quantity deviation value, which can improve the tracking response speed of the active power control quantity.

[0067] For example, referring to Figure 2, active power control quantities include the actual DC voltage value (U in Figure 2). dc The reference active power control quantities include the DC voltage reference value (U in Figure 2). dcref The above process generates active power control deviation values ​​based on active power control quantities and reference active power control quantities. When generating frequency deviation values ​​based on these deviations, the DC voltage deviation value can be determined using the actual DC voltage value and a DC voltage reference value. The frequency deviation value is then generated based on the DC voltage deviation value. For example, as shown in Figure 2, the DC voltage reference value U... dcref Subtract the actual DC voltage U dc The deviation of the DC voltage is obtained, and a frequency deviation value Δω is generated based on the deviation of the DC voltage using a controller (e.g., a PI proportional-integral controller).

[0068] Another example, referring to Figure 2, is that active power control variables include the actual active power value (P in Figure 2). ac The reference active power control quantities include the active power reference value (P in Figure 2). acrefThe above process generates active power control deviation values ​​based on active power control quantities and reference active power control quantities. When generating frequency deviation values ​​based on these deviations, the active power deviation value can be determined using the actual active power value and the active power reference value. The frequency deviation value is then generated based on the active power deviation value. For example, as shown in Figure 2, the active power reference value P... acref Subtract the actual active power P ac The active power deviation is obtained, and a controller (e.g., a PI proportional-integral controller) is used to generate a frequency deviation value Δω based on the power deviation.

[0069] In this implementation, after determining the frequency deviation value Δω through the two examples above, and referring to Figure 2, when determining the initial valve voltage phase reference value based on the frequency deviation value and the rated frequency value, the frequency deviation value Δω can be compared with the rated frequency value ω. rated The values ​​are added together, and the valve voltage phase reference value θ is obtained by integration. v_ref .

[0070] For example, as shown in Figure 2, when generating phase feedforward compensation values ​​based on active power control quantity deviation values, the DC voltage deviation value (such as U) can be used. dcref -U dc ) or active power deviation (e.g., P) acref -P ac The phase feedforward compensation θ is generated using a controller (e.g., a proportional controller). comp_fw .

[0071] In this implementation, when the phase feedforward compensation value is superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value, the AC side voltage phase can be subtracted from the initial valve voltage phase reference value to obtain the AC voltage phase deviation value. The AC side voltage phase includes the AC side grid connection point voltage phase or the transformer valve side voltage phase. If the AC voltage phase deviation value exceeds the set phase deviation value, active power control quantity compensation value, frequency compensation value, and phase compensation value are generated based on the difference between the AC voltage phase deviation value and the set phase deviation value. Compensation is performed based on the phase feedforward compensation value, active power control quantity compensation value, frequency compensation value, and phase compensation value to generate the valve voltage phase reference value. Here, when the grid voltage phase deviates significantly, active power control quantity and frequency and phase compensation values ​​are generated based on the phase deviation, enabling large-range grid phase tracking.

[0072] The aforementioned AC side voltage phase may include the AC side grid connection point voltage phase (θ in Figure 3) or the transformer valve side voltage phase.

[0073] Setting the phase deviation value can include setting an upper limit for the phase deviation (e.g., via θ). lim_max (represented) and setting the lower limit of phase deviation (e.g., via -θ) lim_min(This indicates that) the upper and lower limits of phase deviation can be the same or different; when different, they are equivalent to setting a phase deviation range. Different upper and lower limits of phase deviation can be set for different phase positions. An AC voltage phase deviation value exceeding the set phase deviation value can be understood to include being greater than the set upper limit and / or less than the set lower limit.

[0074] The process of generating active power control compensation values, frequency compensation values, and phase compensation values ​​based on the difference between the AC voltage phase deviation value and the set phase deviation value can be seen in Figure 3 below. When the AC voltage phase deviation exceeds the upper and lower limits, the controller (e.g., a proportional controller) generates a DC voltage compensation value U based on the portion of the phase deviation that exceeds the upper and lower limits. dc_comp Active power compensation value P ac_comp Frequency compensation value ω comp and phase compensation value θ comp .

[0075] Referring to Figure 2, when the phase feedforward compensation value, active power control quantity compensation value, frequency compensation value, and phase compensation value are superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value, the generated phase feedforward compensation value θ can be... comp_fw DC voltage compensation value U dc_comp Active power compensation value P ac_comp Frequency compensation value ω comp and phase compensation value θ comp Superimposed on relevant components (e.g., DC voltage compensation value U) dc_comp It can be superimposed on the DC voltage reference value, the active power compensation value P ac_comp It can be superimposed on the active power reference value and the frequency compensation value ω. comp It can be superimposed on the rated frequency value ω rated Generate valve voltage phase reference value θ v_ref It can be envisioned that each compensation step is optional; that is, they can exist simultaneously, or only one or more can exist.

[0076] In one implementation, in step 103 above, a reactive power deviation value can be generated based on the actual reactive power value and a reactive power reference value; a valve voltage amplitude reference value can be generated based on the reactive power deviation value and the rated AC voltage amplitude; or, a valve voltage amplitude reference value can be generated based on the AC voltage amplitude reference value. For example, as shown in Figure 2, the reactive power reference value θ... acref Subtract the actual reactive power value θ ac Using a controller (e.g., a PI proportional-integral controller) based on the reactive power deviation value and the rated AC voltage amplitude U ac_rated Reference value U of the summation generation valve voltage amplitude vm_refAlternatively, the AC voltage amplitude reference value U can be used. dcref Use a controller (e.g., a proportional controller) to generate a valve voltage reference value U. vm_ref .

[0077] For example, as shown in Figure 2, in step 104 above, the valve voltage phase reference value θ can be used. v_ref and voltage amplitude reference value U vm_ref The three-phase voltage valve reference value u is generated using the conversion stage. vabc_ref .

[0078] In one implementation, in step 105 above, the three-phase valve voltage reference value can be used as the voltage reference value of the modulator. Based on the modulator, a drive signal for controlling the converter is generated; the drive signal is used to control the converter. In this implementation, the sending and receiving end converter stations can choose to use DC voltage control mode at both ends, or DC voltage control at one end and active power control at the other end, depending on the needs of different application scenarios. For example, if it is determined that DC voltage control mode is used, the drive signal can include a DC voltage control signal, which is input to both ends of the converter. Alternatively, if it is determined that DC voltage combined with active power control is used, the drive signal can include both DC voltage control signal and active power control signal, which are input to both ends of the converter respectively.

[0079] The grid-based control strategy proposed in this invention is applicable to typical application scenarios of flexible DC transmission in new power systems, such as large-scale new energy transmission via flexible DC and high-proportion new energy grid interconnection via flexible DC. The control structure is simple and the response speed is fast, which is of great significance for improving the frequency and voltage stability of the system.

[0080] Referring to Figures 4 and 5, which illustrate the effect of grid-type flexible DC control under grid frequency changes, Figure 4 shows the decrease in grid frequency. The horizontal axis represents time in seconds (s), and the vertical axis represents frequency (FREQ) in Hertz (Hz). Figure 5 shows the active power response under the grid-type control strategy proposed in this embodiment of the invention. The horizontal axis represents time in seconds (s), and the vertical axis represents active current (PU) (a numerical notation used in power system analysis and engineering calculations to represent the relative values ​​of various physical quantities and parameters). Combining Figures 4 and 5, when the grid frequency decreases from 50Hz to 47.5Hz at a rate of 1Hz / s, the grid-type control strategy proposed in this embodiment of the invention achieves no abrupt change in internal potential phase angle and frequency, spontaneously providing active power support to the grid. The support capacity can be adaptively adjusted, depending on the flexible DC energy storage and the inertia of the opposite AC system.

[0081] Referring to Figures 6 and 7, which illustrate the effect of grid-based flexible DC control under changes in grid phase angle, Figure 6 shows a backward jump in grid phase angle, with the horizontal axis representing time and the vertical axis representing phase angle (PHASE), in degrees (Deg). Figure 7 shows the active power response under the grid-based control strategy proposed in this embodiment, with the horizontal axis representing time and the vertical axis representing active power response. Combining Figures 6 and 7, when the grid phase changes by -10 degrees, the grid-based control strategy proposed in this embodiment achieves no sudden changes in internal potential phase angle and frequency, spontaneously providing active power support to the grid.

[0082] Referring to Figures 8 and 9, which illustrate the effect of grid-type flexible DC control under grid voltage changes, Figure 6 shows the decrease in grid voltage amplitude, with the horizontal axis representing time and the vertical axis representing grid voltage (kV). Figure 9 shows the reactive power response under the grid-type control strategy proposed in this embodiment, with the horizontal axis representing time and the vertical axis representing reactive power response (Pu). Combining Figures 8 and 9, when the grid voltage amplitude decreases by 10%, the proposed grid-type control maintains the internal potential amplitude without abrupt changes, spontaneously providing rapid reactive power support to the grid.

[0083] As can be seen from Figures 4 to 9, the single-loop grid control method for new energy flexible DC transmission systems based on active control quantities of DC voltage or active power and reactive control quantities of reactive power or AC voltage amplitude has the advantages of simple control structure, fast response speed, and internal potential phase amplitude resolution compared with the traditional voltage and current dual-loop control structure. Furthermore, the phase feedforward compensation value generated based on DC voltage deviation or active power deviation is superimposed on the valve voltage phase reference value, which is beneficial to improving the tracking response speed of DC voltage or active power and enhancing system stability. In addition, the DC voltage, active power, frequency, and phase compensation values ​​generated based on AC voltage phase deviation are superimposed on the corresponding reference values, which can realize reliable tracking of the grid phase over a wide range and improve system stability under phase angle jump scenarios.

[0084] Example 2:

[0085] Based on the same inventive concept, this invention also provides a grid-type control system suitable for flexible DC transmission systems, the structural schematic diagram of which is shown in Figure 10, including:

[0086] The acquisition module is configured to acquire active control quantities and reactive control quantities of the flexible DC transmission system. The active control quantities include actual DC voltage values ​​or actual active power values, and the reactive control quantities include actual reactive power values ​​or AC voltage amplitude reference values.

[0087] The generation module is configured to generate valve voltage phase reference values ​​based on the active power control quantities; generate valve voltage amplitude reference values ​​based on the reactive power control quantities; and generate three-phase valve voltage reference values ​​based on the valve voltage phase reference values ​​and the valve voltage amplitude reference values.

[0088] The control module is configured to control the converter based on the reference value of the three-phase valve voltage.

[0089] In one possible implementation, the generation module is specifically configured as follows:

[0090] Based on the active power control quantity and the reference active power control quantity, generate an active power control quantity deviation value; based on the active power control quantity deviation value, generate a frequency deviation value;

[0091] Based on the frequency deviation value and the rated frequency value, determine the initial valve voltage phase reference value;

[0092] Based on the active control quantity deviation value, generate the phase feedforward compensation value;

[0093] The phase feedforward compensation value is superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value.

[0094] In one possible implementation, the active power control quantity includes the actual DC voltage value, and the reference active power control quantity includes a DC voltage reference value; the generation module is specifically configured as follows:

[0095] Based on the actual DC voltage value and the DC voltage reference value, a DC voltage deviation value is determined; based on the DC voltage deviation value, a frequency deviation value is generated.

[0096] In one possible implementation, the active power control quantity includes the actual active power value, and the reference active power control quantity includes an active power reference value; the generation module is specifically configured as follows:

[0097] Based on the actual active power value and the active power reference value, the active power deviation value is determined; based on the active power deviation value, the frequency deviation value is generated.

[0098] In one possible implementation, the generation module is specifically configured as follows:

[0099] Subtracting the AC side voltage phase from the initial valve voltage phase reference value yields the AC voltage phase deviation value; the AC side voltage phase includes the AC side grid connection point voltage phase or the transformer valve side voltage phase.

[0100] If the AC voltage phase deviation value exceeds the set phase deviation value, then based on the difference between the AC voltage phase deviation value and the set phase deviation value, active power control quantity compensation value, frequency compensation value and phase compensation value are generated.

[0101] Compensation is performed based on the phase feedforward compensation value, the active power control quantity compensation value, the frequency compensation value, and the phase compensation value to generate a valve voltage phase reference value.

[0102] In one possible implementation, the generation module is specifically configured as follows:

[0103] Based on the actual reactive power value and the reactive power reference value, a reactive power deviation value is generated; based on the reactive power deviation value and the rated AC voltage amplitude, a valve voltage amplitude reference value is generated.

[0104] Alternatively, a valve voltage amplitude reference value can be generated based on the AC voltage amplitude reference value.

[0105] In one possible implementation, the control module is specifically configured as follows:

[0106] The three-phase valve voltage reference value is used as the voltage reference value of the modulator, and a drive signal for controlling the converter is generated based on the modulator.

[0107] The converter is controlled using the drive signal.

[0108] Example 3:

[0109] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory is configured to store a computer program, which includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to realize the corresponding method flow or corresponding function, so as to realize the steps of the grid-type control method applicable to flexible DC transmission systems in the above embodiments.

[0110] Example 4:

[0111] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory). A computer-readable storage medium is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a grid-type control method applicable to a flexible DC transmission system in the above embodiments.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval. Industrial applicability

[0117] This application provides a grid-based control method applicable to flexible DC transmission systems, comprising: acquiring active and reactive power control quantities of the flexible DC transmission system, wherein the active power control quantities include actual DC voltage values ​​or actual active power values, and the reactive power control quantities include actual reactive power values ​​or AC voltage amplitude reference values; generating valve voltage phase reference values ​​based on the active power control quantities; generating valve voltage amplitude reference values ​​based on the reactive power control quantities; generating three-phase valve voltage reference values ​​based on the valve voltage phase reference values ​​and valve voltage amplitude reference values; and controlling the converter based on the three-phase valve voltage reference values. The grid-based control strategy proposed in this invention has a simple structure, fast response speed, and good stability, and can exhibit full-condition voltage source characteristics, providing fast and reliable frequency and voltage support for the power grid under various complex operating conditions such as frequency changes and phase jumps.

Claims

1. A grid-type control method applicable to flexible DC transmission systems, comprising: The active and reactive control quantities of the flexible DC transmission system are obtained. The active control quantities include the actual DC voltage value or the actual active power value, and the reactive control quantities include the actual reactive power value or the AC voltage amplitude reference value. Based on the active power control quantity, generate a valve voltage phase reference value; Based on the reactive power control quantity, generate a reference value for the valve voltage amplitude; Based on the valve voltage phase reference value and the valve voltage amplitude reference value, a three-phase valve voltage reference value is generated; The converter is controlled based on the three-phase valve voltage reference value.

2. The method as described in claim 1, wherein, The step of generating the valve voltage phase reference value based on the active power control quantity includes: Based on the active power control quantity and the reference active power control quantity, generate an active power control quantity deviation value; based on the active power control quantity deviation value, generate a frequency deviation value; Based on the frequency deviation value and the rated frequency value, determine the initial valve voltage phase reference value; Based on the active control quantity deviation value, generate the phase feedforward compensation value; The phase feedforward compensation value is superimposed on the initial valve voltage phase reference value to generate the valve voltage phase reference value.

3. The method as described in claim 2, wherein, The step of superimposing the phase feedforward compensation value onto the initial valve voltage phase reference value to generate the valve voltage phase reference value includes: Subtracting the AC side voltage phase from the initial valve voltage phase reference value yields the AC voltage phase deviation value; the AC side voltage phase includes the AC side grid connection point voltage phase or the transformer valve side voltage phase. If the AC voltage phase deviation value exceeds the set phase deviation value, then based on the difference between the AC voltage phase deviation value and the set phase deviation value, active power control quantity compensation value, frequency compensation value and phase compensation value are generated. Compensation is performed based on the phase feedforward compensation value, the active power control quantity compensation value, the frequency compensation value, and the phase compensation value to generate a valve voltage phase reference value.

4. The method as described in claim 2 or 3, wherein, The active power control quantity includes the actual DC voltage value, and the reference active power control quantity includes the DC voltage reference value. The active power control quantity deviation value is generated based on the active power control quantity and the reference active power control quantity. Based on the active power control quantity deviation value, the frequency deviation value is generated including: The DC voltage deviation value is determined based on the actual DC voltage value and the DC voltage reference value; The frequency deviation value is generated based on the DC voltage deviation value.

5. The method as described in claim 2 or 3, wherein, The active power control quantity includes the actual active power value, and the reference active power control quantity includes the active power reference value. The active power control quantity deviation value is generated based on the active power control quantity and the reference active power control quantity. Based on the active power control quantity deviation value, the frequency deviation value is generated including: The active power deviation value is determined based on the actual active power value and the active power reference value. The frequency deviation value is generated based on the active power deviation value.

6. The method of claim 1, wherein, The step of generating a valve voltage amplitude reference value based on the reactive power control quantity includes: Based on the actual reactive power value and the reactive power reference value, a reactive power deviation value is generated; based on the reactive power deviation value and the rated AC voltage amplitude, a valve voltage amplitude reference value is generated. Alternatively, a valve voltage amplitude reference value can be generated based on the AC voltage amplitude reference value.

7. The method of claim 1, wherein, The control of the converter based on the three-phase valve voltage reference value includes: The three-phase valve voltage reference value is used as the voltage reference value of the modulator, and a drive signal for controlling the converter is generated based on the modulator. The converter is controlled using the drive signal.

8. A grid-type control system suitable for flexible DC transmission systems, comprising: The acquisition module is configured to acquire active control quantities and reactive control quantities of the flexible DC transmission system. The active control quantities include actual DC voltage values ​​or actual active power values, and the reactive control quantities include actual reactive power values ​​or AC voltage amplitude reference values. The generation module is configured to generate valve voltage phase reference values ​​based on the active power control variables. Based on the reactive power control quantity, generate a valve voltage amplitude reference value; based on the valve voltage phase reference value and the valve voltage amplitude reference value, generate a three-phase valve voltage reference value; The control module is configured to control the converter based on the reference value of the three-phase valve voltage.

9. The system of claim 8, wherein, The generation module is specifically configured as follows: Based on the active power control variables, generate active power control variable deviation values; based on the active power control variable deviation values, generate frequency deviation values. Based on the frequency deviation value and the rated frequency value, determine the initial threshold voltage phase reference value; Based on the active control quantity deviation value, generate the phase feedforward compensation value; The phase feedforward compensation value is superimposed on the initial threshold voltage phase reference value to generate the domain voltage phase reference value.

10. The system of claim 8, wherein, The generation module is specifically configured as follows: Based on the actual reactive power value and the reactive power reference value, a reactive power deviation value is generated; based on the reactive power deviation value and the rated AC voltage amplitude, a threshold voltage amplitude reference value is generated. Alternatively, a threshold voltage amplitude reference value can be generated based on the AC voltage amplitude reference value.

11. A computer device, comprising: One or more processors; The processor is configured to store one or more programs; When the one or more programs are executed by the one or more processors, the grid-type control method for flexible DC transmission systems as described in any one of claims 1 to 7 is implemented.

12. A computer-readable storage medium having a computer program thereon, which, when executed, implements the grid-type control method for flexible DC transmission systems as described in any one of claims 1 to 7.

Images