Frequency support method, electronic equipment and storage medium for new energy grid-connected system

Abstract

The present invention provides a frequency support method, electronic device and storage medium for a new energy grid-connected system. The method includes: determining the actual frequency of the power grid of the new energy grid-connected system, and determining the frequency deviation and frequency change rate of the new energy grid-connected system based on the actual frequency of the power grid; when the frequency change rate does not reach a preset peak value, determining the first adjustment energy of the receiving-end MMC in the new energy grid-connected system based on the frequency deviation, and determining the DC voltage deviation of the HVDC in the new energy grid-connected system based on the first adjustment energy; determining the first voltage of the sending-end MMC in the new energy grid-connected system based on the DC voltage deviation, and determining the second adjustment energy of the sending-end MMC based on the first voltage and the DC current of the HVDC; and adjusting and supporting the frequency of the new energy grid-connected system based on the first adjustment energy and the second adjustment energy. The present invention can provide timely and reliable frequency support for the new energy grid-connected system based on the capacitance energy of the two MMC converter stations at the sending and receiving ends.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current grid-connected new energy, and in particular to a frequency support method, electronic equipment and storage medium for a new energy grid-connected system. Background Art

[0002] my country's power system is currently undergoing an accelerated transformation from a traditional system dominated by conventional synchronous generators to a new one dominated by renewable energy sources such as wind and solar. By 2030, China's total installed wind and solar capacity is projected to reach 200 GW, exceeding 50% of installed capacity. By 2050, wind and solar power generation will account for 68% of installed capacity and 48% of electricity generation. To meet the long-distance "west-to-east power transmission" demand, my country's power grid has been developing ultra-high voltage AC and DC transmission since 2010, achieving a total inter-regional AC and DC transmission capacity exceeding 200 GW. However, because renewable energy generation and DC transmission rely on power electronic converters for grid connection, the traditional synchronous generation and transmission model of the power system is gradually transforming into a new asynchronous model characterized by "power electronics." This situation is causing the power system's inertia to decrease, potentially posing a significant threat to its safe and stable operation.

[0003] Currently, modular multilevel technology offers significant advantages in the field of large-scale renewable energy grid integration. Connecting large-scale renewable energy to the grid via a modular multilevel converter-high voltage direct current (MMC-HVDC) system reduces the overall grid inertia and can typically provide frequency support through the energy stored in the MMC capacitors. However, existing technologies rely heavily on communication equipment for coordinated control between the sending and receiving MMC converter stations, impacting both real-time performance and reliability.

[0004] Therefore, how to explore an energy collaborative control scheme for the sending-end MMC converter station and the receiving-end MMC converter station without the need for communication, so as to maximize the utilization of MMC capacitor energy in real time and thus provide reliable frequency support for the power grid, is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] An embodiment of the present invention provides a frequency support method, electronic device and storage medium for a new energy grid-connected system to solve the problem in the prior art that the communication-based coordinated control scheme between the sending-end MMC converter station and the receiving-end MMC converter station is heavily dependent on communication equipment, and thus cannot provide timely and reliable frequency support for the new energy grid-connected system in real time.

[0006] In a first aspect, an embodiment of the present invention provides a frequency support method for a new energy grid-connected system, comprising:

[0007] Determining the actual frequency of the power grid of the new energy grid-connected system based on the bus voltage at the grid connection point of the new energy grid-connected system, and determining the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual frequency of the power grid;

[0008] When the frequency change rate does not reach a preset peak value, determining a first regulation energy for charging and discharging a capacitor in a receiving-end MMC in the new energy grid-connected system based on the frequency deviation, and determining a DC voltage deviation of an HVDC in the new energy grid-connected system based on the first regulation energy;

[0009] Determine a first voltage of a sending-end MMC in a new energy grid-connected system based on the DC voltage deviation, and determine a second regulating energy for charging and discharging a capacitor in the sending-end MMC based on the first voltage and the HVDC DC current;

[0010] The frequency of the new energy grid-connected system is regulated and supported based on the first regulation energy and the second regulation energy.

[0011] In a possible implementation, after determining the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual frequency of the power grid, the method further includes:

[0012] When the frequency change rate reaches a preset peak value, a first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on a preset energy release curve.

[0013] In a possible implementation, determining the first regulation energy for charging and discharging a capacitor in a receiving-end MMC in a new energy grid-connected system based on the frequency deviation includes:

[0014] based on Determine the first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system;

[0015] Where ΔW MMC represents the first adjustment energy, H MMC It represents the simulated inertia time constant of the receiving MMC at rated capacity, S0 represents the rated capacity of the receiving MMC, W0 represents the rated energy of the receiving MMC, k wf represents the energy-frequency droop control coefficient, and Δf represents the frequency deviation.

[0016] In a possible implementation, determining a DC voltage deviation of an HVDC in the new energy grid-connected system based on the first regulation energy includes:

[0017] Based on ΔV dc =k vw ΔWMMC , determine the DC voltage deviation of HVDC in the renewable energy grid-connected system;

[0018] Where, ΔV dc represents the DC voltage deviation, k vw Indicates the DC voltage-energy droop control coefficient corresponding to the receiving-end MMC.

[0019] In a possible implementation, determining the second regulation energy for charging and discharging a capacitor in the sending-end MMC based on the first voltage and the HVDC direct current includes:

[0020] Determine a second voltage of the receiving-end MMC based on the first voltage and the DC current;

[0021] A second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the second voltage.

[0022] In a possible implementation, determining the second voltage of the receiving-end MMC based on the first voltage and the DC current includes:

[0023] based on Determining a second voltage of the receiving-end MMC;

[0024] Among them, V dc1_E represents the second voltage, V dc2 represents the first voltage, R dc The equivalent resistance of the MMC-HVDC DC line, I dc Represents the DC current, L dc represents the equivalent reactance of the MMC-HVDC DC line, d represents the derivative sign, and t represents time.

[0025] In a possible implementation, determining a second regulating energy for charging and discharging a capacitor in the sending-end MMC based on the second voltage includes:

[0026] based on Determine the second regulating energy for charging and discharging the capacitor in the sending-end MMC;

[0027] Where ΔW E represents the second adjustment energy, k vw ' represents the DC voltage-energy droop control coefficient corresponding to the sending-end MMC, ΔV dcE Indicates the voltage deviation of the receiving MMC, V dc0 Indicates the DC voltage rating of the receiving-end MMC.

[0028] In a possible implementation, after the frequency of the new energy grid-connected system is regulated based on the first regulated energy and the second regulated energy, the method further includes:

[0029] Based on ΔW=k w ΔW MMC , adjusting the total energy utilization rate of the receiving-end MMC to a preset value so that the capacitor voltage of the receiving-end MMC returns to the initial value;

[0030] Wherein, ΔW represents the total energy utilization rate, k w Indicates the variable energy recovery factor; ΔW MMC represents the first adjustment energy.

[0031] In a second aspect, an embodiment of the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method described in the first aspect or any possible implementation of the first aspect are implemented.

[0032] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the method described in the first aspect or any possible implementation of the first aspect.

[0033] The embodiment of the present invention provides a frequency support method, electronic device and storage medium for a new energy grid-connected system, which determines the actual frequency of the power grid of the current new energy grid-connected system based on the bus voltage of the grid connection point of the new energy grid-connected system, and then determines the frequency deviation and frequency change rate of the current new energy grid-connected system based on the actual frequency of the power grid. When the frequency change rate does not reach a preset peak value, the first regulation energy of the charging and discharging of the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on the frequency deviation, thereby realizing real-time tracking of the frequency change of the power system; then, the DC voltage deviation of the HVDC in the new energy grid-connected system is determined based on the first regulation energy, thereby reflecting the utilization of the capacitor energy in the receiving-end MMC in real time and accurately to the DC voltage electrical quantity, laying the foundation for realizing energy synchronization between the two converter stations; then, based on the DC The voltage deviation determines the first voltage of the sending-end MMC in the renewable energy grid-connected system, and the second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the first voltage and the direct current of the HVDC. The energy change of the receiving-end MMC is estimated in the sending-end MMC through the first voltage containing the capacitor energy change information in the receiving-end MMC, thereby achieving real-time synchronization of energy between the two converter stations of the sending-end MMC and the receiving-end MMC on the basis of avoiding the construction of a remote communication system, which not only reduces the construction cost but also improves the reliability of the renewable energy grid-connected system via MMC-HVDC. Then, the frequency of the renewable energy grid-connected system is regulated and supported based on the first regulating energy and the second regulating energy, thereby achieving timely and reliable frequency support for the renewable energy grid-connected system based on the capacitor energy of the two MMC converter stations of the sending and receiving ends. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a flow chart of an implementation method of a frequency support method for a new energy grid-connected system provided by an embodiment of the present invention;

[0036] Figure 2 1 is a topological diagram of a frequency support method for a new energy grid-connected system provided by an embodiment of the present invention;

[0037] Figure 3 2. It is a structural diagram of an energy optimization utilization curve of a frequency support method for a new energy grid-connected system provided by an embodiment of the present invention;

[0038] Figure 4 1 is a schematic structural diagram of a frequency support device for a new energy grid-connected system provided by an embodiment of the present invention;

[0039] Figure 5 is a schematic diagram of an electronic device provided by an embodiment of the present invention;

[0040] Figure 6 It is a structural schematic diagram of an energy recovery coefficient curve of a frequency support method for a new energy grid-connected system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below with reference to the accompanying drawings.

[0043] Figure 1 This is a flow chart of the frequency support method for the new energy grid-connected system provided by the embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a frequency support method for a new energy grid-connected system, including:

[0044] Step 101: Determine the actual grid frequency of the new energy grid-connected system based on the bus voltage at the grid connection point of the new energy grid-connected system, and determine the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual grid frequency.

[0045] In step 101, Figure 2 Please refer to the topological structure diagram of the frequency support method of the new energy grid-connected system provided in the embodiment of the present invention. Figure 1 and Figure 2 When the frequency of the AC grid in the new energy grid-connected system fluctuates, the bus voltage u of the grid-connected point of the new energy grid-connected system can be collected in real time. abc ,u abc The actual frequency f of the AC grid in the current renewable energy grid-connected system can be obtained through the phase-locked loop (PLL). Then, the frequency deviation and frequency change rate of the current renewable energy grid-connected system can be further determined based on the actual grid frequency f. For example, the actual grid frequency f and the rated frequency reference value f of the AC grid can be used to determine the frequency deviation and frequency change rate of the current renewable energy grid-connected system. ref Determine the frequency deviation. In this way, after accurately determining the frequency deviation and frequency change rate of the renewable energy grid-connected system, it is beneficial for the two converter stations in the renewable energy grid-connected system to subsequently determine the energy support for regulating the AC grid frequency fluctuation based on the frequency deviation and / or frequency change rate.

[0046] Optionally, in order to ensure that the frequency support provided by the capacitor energy in the MMC converter station to the new energy grid-connected system is not affected by the DC voltage deviation of the HVDC, and thus to achieve independent regulation of the MMC capacitor energy at the receiving end, the DC modulation ratio can be used to achieve decoupling of the DC voltage of the HVDC in the new energy grid-connected system and the voltage of the MMC capacitor at the receiving end.

[0047] For example, it can be based on V dc ≈(N pj +N nj )V Cavg =M dc V dcN Decouple the HVDC DC voltage and the receiving-end MMC capacitor voltage in the new energy grid-connected system.

[0048] Among them, V dc Indicates the DC voltage of HVDC, N pj Indicates the number of upper bridge arm submodules in the receiving end MMC, N nj Indicates the number of lower bridge arm submodules in the receiving MMC, V Cavg Represents the capacitor voltage of the MMC neutron module at the receiving end, M dc Indicates the DC modulation ratio, V dcN Indicates the DC voltage rating of HVDC.

[0049] Step 102: When the frequency change rate does not reach a preset peak value, a first regulation energy for charging and discharging a capacitor in a receiving-end MMC in the new energy grid-connected system is determined based on the frequency deviation, and a DC voltage deviation of an HVDC in the new energy grid-connected system is determined based on the first regulation energy.

[0050] In step 102, when the frequency change rate does not reach the preset peak value, Figure 2 As shown, it can be based on Figure 2 The energy-frequency droop control module in the system establishes a real-time connection between the real-time frequency information of the AC grid and the capacitor energy of the receiving MMC, thereby facilitating the provision of certain frequency support for the AC grid based on the capacitor energy of the receiving MMC.

[0051] Optionally, when the frequency change rate does not reach a preset peak value, the first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the current new energy grid-connected system can be determined based on the frequency deviation of the current AC power grid, thereby realizing real-time perception of the frequency change of the AC power grid and providing real-time frequency support for the AC power grid based on the capacitor energy in the receiving-end MMC.

[0052] Then, based on the first regulated energy, the change in the DC voltage of the receiving-end MMC in the current renewable energy grid-connected system can be further determined after the energy of its own capacitor charge and discharge is regulated based on the first regulated energy. That is, based on the first regulated energy, the DC voltage deviation of the HVDC in the current renewable energy grid-connected system can be further determined, thereby accurately reflecting the energy utilization of the receiving-end MMC converter station in real time on the DC voltage electrical quantity, thereby laying the foundation for achieving communication-free energy synchronization between the receiving-end MMC and the sending-end MMC converter stations.

[0053] In one possible implementation, determining a first regulation energy for charging and discharging a capacitor in a receiving-end MMC in a new energy grid-connected system based on a frequency deviation may include:

[0054] based on Determine the first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system.

[0055] Where ΔW MMC represents the first adjustment energy, H MMC It represents the simulated inertia time constant of the receiving MMC at rated capacity, S0 represents the rated capacity of the receiving MMC, W0 represents the rated energy of the receiving MMC, k wf represents the energy-frequency droop control coefficient, and Δf represents the frequency deviation.

[0056] In this embodiment, the first adjustment energy for charging and discharging the capacitor in the receiving-end MMC is further determined based on the real-time frequency deviation of the AC power grid in the new energy grid-connected system, thereby effectively realizing real-time perception of the frequency change of the AC power grid and providing real-time frequency support for the AC power grid based on the capacitor energy in the receiving-end MMC.

[0057] In a possible implementation, determining a DC voltage deviation of an HVDC in a new energy grid-connected system based on the first adjustment energy may include:

[0058] Based on ΔV dc =k vw ΔW MMC , determine the DC voltage deviation of HVDC in the new energy grid-connected system.

[0059] Where, ΔV dc Indicates the DC voltage deviation, k vw Indicates the DC voltage-energy droop control coefficient corresponding to the receiving-end MMC.

[0060] In this embodiment, when the AC grid within the new energy grid-connected system experiences certain frequency fluctuations, a certain frequency support can be provided to the AC grid based on the capacitor energy in the receiving end and / or the receiving end MMC converter station to ensure the safe and stable operation of the new energy grid-connected system. Optionally, after the receiving end MMC provides a certain frequency support for the AC grid, its internal capacitor energy will change, and then the DC voltage deviation of the receiving end MMC will be further determined based on the change in its internal capacitor energy. At this time, the receiving end MMC will adjust its DC voltage to adapt to the change in capacitor energy, thereby forming a new DC voltage reference value to achieve its own constant DC voltage control. At this time, the dynamic change in the capacitor energy of the receiving end MMC can be dynamically reflected in the DC voltage change of the HVDC, that is, a linear correlation is established between the DC voltage of the HVDC and the capacitor energy change of the receiving end MMC, thereby laying the foundation for achieving energy synchronization between the two converter stations of the receiving end MMC and the sending end MMC.

[0061] In a possible implementation, after determining the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual frequency of the power grid, the method further includes:

[0062] When the frequency change rate reaches a preset peak value, a first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on a preset energy release curve.

[0063] In this embodiment, Figure 3 This is a structural diagram of the energy optimization utilization curve of the frequency support method for the new energy grid-connected system provided by the embodiment of the present invention. Please refer to Figures 1 to 3. When the frequency change rate of the AC power grid in the new energy grid-connected system reaches a preset peak value, for example, the preset peak value can be the frequency change rate corresponding to when the operating frequency of the AC power grid drops to the lowest frequency point during operation. At this time, it can be considered that the current AC power grid has been subjected to a large frequency disturbance. Therefore, the first adjustment energy of the capacitor charging and discharging in the receiving-end MMC under the current frequency change rate can be directly determined based on the preset energy release curve, thereby timely providing a certain frequency support for the current AC power grid based on the adjustment of the capacitor charging and discharging energy in the receiving-end MMC, which is conducive to achieving the safe and stable operation of the AC power grid, and further ensures the safe and stable operation of the new energy grid-connected system.

[0064] Optional, can be based on Figure 2 Energy release optimization control module combined Figure 3 The energy optimization utilization curve (i.e., the preset energy release curve) in the receiving end MMC is used to determine the first adjustment energy of the capacitor charge and discharge under the current frequency change rate, thereby adjusting the actual frequency of the current AC power grid based on the first adjustment energy. For example, Figure 3 The utilization schemes of various energy optimization utilization curves are shown. After model simulation and experimental verification, it can be based on Figure 3 The energy optimization utilization scheme corresponding to the quadratic curve shown adjusts the first regulation energy of the capacitor charging and discharging in the receiving-end MMC, thereby achieving real-time regulation support for the frequency change of the AC power grid.

[0065] Optionally, a preset energy release curve can be designed based on the process of the frequency change rate (RoCoF) of the AC power grid in the new energy grid-connected system changing from its initial value RoCoF0 to 0. Considering the energy utilization limit ΔW in MMC lim Therefore, when designing the preset energy release curve, the first adjustment energy and frequency change rate can satisfy: In this way, the capacitance energy of the MMC can be maximized, and the energy utilization process can be continued until the frequency change rate of the AC power grid changes from its initial value RoCoF0 to 0, avoiding the rapid interruption of the frequency support of the AC power grid, thereby providing real-time frequency support for the AC power grid in the new energy grid-connected system.

[0066] Step 103: determining a first voltage of the sending-end MMC in the new energy grid-connected system based on the DC voltage deviation, and determining a second regulating energy for charging and discharging the capacitor in the sending-end MMC based on the first voltage and the HVDC DC current.

[0067] In step 103, if Figure 2As shown, when the DC voltage of the receiving-end MMC changes, causing a DC voltage deviation in the HVDC, a first voltage of the sending-end MMC in the renewable energy grid-connected system can be determined based on this DC voltage deviation. In this case, this first voltage is a DC voltage that includes information about the energy change in the receiving-end MMC capacitor. Then, based on this first voltage and the DC current of the HVDC, a second regulating energy for charging and discharging the capacitor in the sending-end MMC is further determined.

[0068] In this embodiment, based on the first voltage including the energy change information of the receiving-end MMC, the change of the receiving-end MMC capacitor energy is estimated in the sending-end MMC, thereby achieving energy synchronization without communication between the sending-end MMC and the receiving-end MMC converter stations.

[0069] In one possible implementation, determining a second regulation energy for charging and discharging a capacitor in a sending-end MMC based on the first voltage and the direct current of the HVDC includes:

[0070] A second voltage of the receiving-end MMC is determined based on the first voltage and the DC current.

[0071] A second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the second voltage.

[0072] In this embodiment, optionally, after determining the first voltage at the sending-end MMC port, the HVDC line loss can be further considered, thereby deriving the second voltage at the receiving-end MMC port based on the first voltage and line loss. That is, the DC current of the HVDC line and the first voltage at the sending-end MMC port can be collected, and then the second voltage at the receiving-end MMC can be determined based on the first voltage and DC current. Subsequently, the second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the second voltage. In this way, communication-free energy synchronization is achieved between the two converter stations, the sending-end MMC and the receiving-end MMC. At the same time, the capacitor energy within the two converter stations, the receiving-end MMC and the sending-end MMC, provides a certain frequency support for the AC power grid experiencing frequency disturbances, thereby effectively ensuring the safe and stable operation of the new energy grid-connected system.

[0073] In a possible implementation, determining the second voltage of the receiving-end MMC based on the first voltage and the DC current may include:

[0074] based on A second voltage of the receiving-end MMC is determined.

[0075] Among them, V dc1_E Represents the second voltage, V dc2 Represents the first voltage, R dc The equivalent resistance of the MMC-HVDC DC line, I dc Indicates DC current, L dcrepresents the equivalent reactance of the MMC-HVDC DC line, d represents the derivative sign, and t represents time.

[0076] In this embodiment, by taking into account MMC-HVDC line losses and combining the first voltage detected at the sending-end MMC port, a second voltage at the receiving-end MMC port can be derived. This facilitates subsequent estimation of the energy change at the receiving-end MMC based on this second voltage in the sending-end MMC, thereby achieving communication-free energy synchronization between the sending and receiving MMC converter stations.

[0077] In a possible implementation, determining the second regulation energy for charging and discharging the capacitor in the sending-end MMC based on the second voltage may include:

[0078] based on Determine the second regulation energy for charging and discharging the capacitor in the sending-end MMC.

[0079] Where ΔW E represents the second adjustment energy, k vw ' represents the DC voltage-energy droop control coefficient corresponding to the sending-end MMC, ΔV dcE Indicates the voltage deviation of the receiving MMC, V dc0 Indicates the DC voltage rating of the receiving-end MMC.

[0080] In this embodiment, Figure 2 As shown, after obtaining the second voltage at the receiving-end MMC port, the voltage deviation at the receiving-end MMC port can be further estimated based on this second voltage. Then, based on this voltage deviation, a second adjustment energy for charging and discharging the capacitor in the sending-end MMC is determined. In this way, the capacitor energy at both the receiving-end MMC and the sending-end MMC converter stations provides frequency support for AC power grids experiencing frequency disturbances, thereby ensuring the safe and stable operation of the new energy grid-connected system.

[0081] Step 104: Regulate and support the frequency of the new energy grid-connected system based on the first regulated energy and the second regulated energy.

[0082] In step 104, the receiving-end MMC and the sending-end MMC converter stations respectively provide frequency support for the AC power grid with frequency disturbance using the first regulating energy and the second regulating energy, thereby achieving frequency support for the new energy grid-connected system.

[0083] In a possible implementation, after the frequency of the new energy grid-connected system is regulated based on the first regulated energy and the second regulated energy, the method further includes:

[0084] Based on ΔW=k w ΔW MMC, adjusting the total energy utilization rate of the receiving-end MMC to a preset value so that the capacitor voltage of the receiving-end MMC returns to the initial value;

[0085] Among them, ΔW represents the total energy utilization rate, k w Indicates the variable energy recovery factor; ΔW MMC Indicates the first adjustment energy.

[0086] In this embodiment, Figure 6 A schematic diagram of the structure of the energy recovery coefficient curve of the frequency support method of the new energy grid-connected system provided by the embodiment of the present invention is shown as follows: Figure 6 As shown, after the frequency of the renewable energy grid-connected system is regulated and supported, the voltage of the capacitor in the MMC can be restored to its initial value. For example, a variable energy recovery coefficient k w , the total energy utilization rate ΔW of the capacitor of the receiving-end MMC sub-module is adjusted to 0, thereby restoring the capacitor voltage of the receiving-end MMC to its initial value. Then, based on the energy coordinated control between the two converter stations (that is, the communication-free energy synchronization process between the two converter stations), the capacitor voltage of the sending-end MMC will also be restored to its corresponding initial value, so that the next time, based on the capacitor energy in the receiving-end MMC and the sending-end MMC, frequency support can be provided for the AC power grid in the new energy grid-connected system when frequency disturbance occurs again.

[0087] An embodiment of the present invention provides a frequency support method for a new energy grid-connected system, which determines the actual frequency of the power grid of the current new energy grid-connected system based on the bus voltage of the grid-connected point of the new energy grid-connected system, and then determines the frequency deviation and frequency change rate of the current new energy grid-connected system based on the actual frequency of the power grid. When the frequency change rate does not reach a preset peak value, the first regulating energy of the charging and discharging of the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on the frequency deviation, thereby realizing real-time tracking of the frequency change of the power system; then, the DC voltage deviation of the HVDC in the new energy grid-connected system is determined based on the first regulating energy, thereby accurately reflecting the utilization of the capacitor energy in the receiving-end MMC to the DC voltage electrical quantity in real time, laying the foundation for realizing energy synchronization between the two converter stations; then, the DC voltage deviation is determined based on the A first voltage of a sending-end MMC in a renewable energy grid-connected system is determined, and a second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the first voltage and the direct current of the HVDC. The energy change of the receiving-end MMC is estimated in the sending-end MMC through the first voltage containing the capacitor energy change information in the receiving-end MMC, thereby achieving real-time synchronization of energy between the two converter stations of the sending-end MMC and the receiving-end MMC on the basis of avoiding the construction of a remote communication system, which not only reduces the construction cost but also improves the reliability of the renewable energy grid-connected system via MMC-HVDC. Then, the frequency of the renewable energy grid-connected system is regulated and supported based on the first regulating energy and the second regulating energy, thereby achieving timely and reliable frequency support for the renewable energy grid-connected system based on the capacitor energy of the two MMC converter stations of the sending and receiving ends.

[0088] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0089] The following are device embodiments of the present invention. For details not fully described therein, reference may be made to the corresponding method embodiments described above.

[0090] Figure 4 A schematic diagram of the structure of a frequency support device for a new energy grid-connected system according to an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0091] like Figure 4 As shown, the frequency support device 4 of the new energy grid-connected system includes:

[0092] The frequency data acquisition module 401 is used to determine the actual grid frequency of the new energy grid-connected system based on the bus voltage at the grid connection point of the new energy grid-connected system, and determine the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual grid frequency.

[0093] The first energy determination module 402 is used to determine a first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system based on the frequency deviation when the frequency change rate does not reach a preset peak value, and to determine a DC voltage deviation of the HVDC in the new energy grid-connected system based on the first regulation energy.

[0094] The second energy determination module 403 is used to determine the first voltage of the sending-end MMC in the new energy grid-connected system based on the DC voltage deviation, and determine the second regulation energy for charging and discharging the capacitor in the sending-end MMC based on the first voltage and the DC current of the HVDC.

[0095] The system frequency adjustment module 404 is configured to adjust the frequency of the new energy grid-connected system based on the first adjustment energy and the second adjustment energy.

[0096] The embodiment of the present invention provides a frequency support device for a new energy grid-connected system, including: a frequency data acquisition module 401, a first energy determination module 402, a second energy determination module 403 and a system frequency adjustment module 404. The actual frequency of the power grid of the current new energy grid-connected system is determined based on the bus voltage of the grid connection point of the new energy grid-connected system, and then the frequency deviation and frequency change rate of the current new energy grid-connected system are determined based on the actual frequency of the power grid. When the frequency change rate does not reach a preset peak value, the first adjustment energy of the capacitor charging and discharging in the receiving-end MMC in the new energy grid-connected system is determined based on the frequency deviation, thereby achieving real-time tracking of the frequency change of the power system; then, the DC voltage deviation of the HVDC in the new energy grid-connected system is determined based on the first adjustment energy, thereby accurately reflecting the utilization of the capacitor energy in the receiving-end MMC to the DC voltage electrical quantity in real time, laying the foundation for achieving energy synchronization between the two converter stations; then, the sending-end MMC in the new energy grid-connected system is determined based on the DC voltage deviation. The first voltage of the MC is determined, and the second regulating energy of the capacitor charging and discharging in the sending-end MMC is determined based on the first voltage and the direct current of the HVDC. The energy change of the receiving-end MMC is estimated in the sending-end MMC through the first voltage containing the capacitor energy change information in the receiving-end MMC, thereby achieving real-time synchronization of energy between the two converter stations of the sending-end MMC and the receiving-end MMC on the basis of avoiding the construction of a remote communication system, which not only reduces the construction cost but also improves the reliability of the new energy grid-connected system via MMC-HVDC; then, the frequency of the new energy grid-connected system is regulated and supported based on the first regulating energy and the second regulating energy, thereby achieving timely and reliable frequency support for the new energy grid-connected system based on the capacitor energy of the two MMC converter stations at the sending and receiving ends.

[0097] In a possible implementation, the first energy determination module 402 is specifically configured to:

[0098] based on Determine the first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system.

[0099] Where ΔW MMC represents the first adjustment energy, H MMC It represents the simulated inertia time constant of the receiving MMC at rated capacity, S0 represents the rated capacity of the receiving MMC, W0 represents the rated energy of the receiving MMC, k wf represents the energy-frequency droop control coefficient, and Δf represents the frequency deviation.

[0100] In a possible implementation, the first energy determining module 402 is further specifically configured to:

[0101] Based on ΔV dc =k vw ΔW MMC , determine the DC voltage deviation of HVDC in the new energy grid-connected system.

[0102] Where, ΔV dc Indicates the DC voltage deviation, k vw Indicates the DC voltage-energy droop control coefficient corresponding to the receiving-end MMC.

[0103] In a possible implementation, the first energy determining module 402 is further specifically configured to:

[0104] When the frequency change rate reaches a preset peak value, a first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on a preset energy release curve.

[0105] In a possible implementation, the second energy determination module 403 is specifically configured to:

[0106] A second voltage of the receiving-end MMC is determined based on the first voltage and the DC current.

[0107] A second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the second voltage.

[0108] In a possible implementation, the second energy determination module 403 is further specifically configured to:

[0109] based on A second voltage of the receiving-end MMC is determined.

[0110] Among them, V dc1_E Represents the second voltage, V dc2 Represents the first voltage, R dc The equivalent resistance of the MMC-HVDC DC line, I dc Indicates DC current, L dcrepresents the equivalent reactance of the MMC-HVDC DC line, d represents the derivative sign, and t represents time.

[0111] In a possible implementation, the second energy determination module 403 is further specifically configured to:

[0112] based on Determine the second regulation energy for charging and discharging the capacitor in the sending-end MMC.

[0113] Where ΔW E represents the second adjustment energy, k vw ' represents the DC voltage-energy droop control coefficient corresponding to the sending-end MMC, ΔV dcE Indicates the voltage deviation of the receiving MMC, V dc0 Indicates the DC voltage rating of the receiving-end MMC.

[0114] In a possible implementation, the system frequency adjustment module 404 is specifically configured to:

[0115] Based on ΔW=k w ΔW MMC , adjusting the total energy utilization rate of the receiving-end MMC to a preset value so that the capacitor voltage of the receiving-end MMC returns to the initial value;

[0116] Among them, ΔW represents the total energy utilization rate, k w Indicates the variable energy recovery factor; ΔW MMC Indicates the first adjustment energy.

[0117] Figure 5 Schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 5 As shown, the electronic device 5 of this embodiment includes: a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, the steps in the frequency support method embodiments of each of the above-mentioned new energy grid-connected systems are implemented, such as Figure 1 Alternatively, when the processor 50 executes the computer program 52, the functions of the modules in the above-mentioned device embodiments are realized, for example, Figure 4 Functions of modules 401 to 404 are shown.

[0118] Exemplarily, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 52 in the electronic device 5. For example, the computer program 52 may be divided into Figure 4 Modules 401 to 404 are shown.

[0119] The electronic device 5 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The electronic device 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will understand that Figure 5 It is only an example of the electronic device 5 and does not constitute a limitation of the electronic device 5. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the electronic device may also include input and output devices, network access devices, buses, etc.

[0120] The processor 50 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0121] The memory 51 can be an internal storage unit of the electronic device 5, such as a hard disk or memory of the electronic device 5. The memory 51 can also be an external storage device of the electronic device 5, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 5. Furthermore, the memory 51 can also include both an internal storage unit of the electronic device 5 and an external storage device. The memory 51 is used to store the computer program and other programs and data required by the electronic device. The memory 51 can also be used to temporarily store data that has been output or is about to be output.

[0122] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0123] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0124] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0125] In the embodiments provided by the present invention, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are merely schematic. For example, the division of the modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0126] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0127] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0128] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the frequency support method embodiment of each new energy grid-connected system. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable media does not include electrical carrier signals and telecommunication signals.

[0129] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A frequency support method for a new energy grid-connected system, characterized in that: include: Determining the actual frequency of the power grid of the new energy grid-connected system based on the bus voltage at the grid connection point of the new energy grid-connected system, and determining the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual frequency of the power grid; When the frequency change rate does not reach a preset peak value, determining a first regulation energy for charging and discharging a capacitor in a receiving-end MMC in the new energy grid-connected system based on the frequency deviation, and determining a DC voltage deviation of an HVDC in the new energy grid-connected system based on the first regulation energy; Determine a first voltage of a sending-end MMC in a new energy grid-connected system based on the DC voltage deviation, and determine a second regulating energy for charging and discharging a capacitor in the sending-end MMC based on the first voltage and the HVDC DC current; The frequency of the new energy grid-connected system is regulated and supported based on the first regulation energy and the second regulation energy.

2. The frequency support method of the new energy grid-connected system according to claim 1, characterized in that: After determining the frequency deviation and frequency change rate of the new energy grid-connected system according to the actual frequency of the power grid, the method further includes: When the frequency change rate reaches a preset peak value, a first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system is determined based on a preset energy release curve.

3. The frequency support method for a new energy grid-connected system according to claim 1, characterized in that: The determining, based on the frequency deviation, a first regulating energy for charging and discharging a capacitor in a receiving-end MMC in the new energy grid-connected system includes: based on Determine the first regulation energy for charging and discharging the capacitor in the receiving-end MMC in the new energy grid-connected system; Where ΔW MMC represents the first adjustment energy, H MMC It represents the simulated inertia time constant of the receiving MMC at rated capacity, S0 represents the rated capacity of the receiving MMC, W0 represents the rated energy of the receiving MMC, k wf represents the energy-frequency droop control coefficient, and Δf represents the frequency deviation.

4. The frequency support method for the new energy grid-connected system according to claim 3, characterized in that: The determining of a direct current voltage deviation of an HVDC in a new energy grid-connected system based on the first regulation energy includes: Based on ΔV dc =k vw ΔW MMC , determine the DC voltage deviation of HVDC in the renewable energy grid-connected system; Where, ΔV dc represents the DC voltage deviation, k vw Indicates the DC voltage-energy droop control coefficient corresponding to the receiving-end MMC.

5. The frequency support method for the new energy grid-connected system according to claim 1, characterized in that: The determining of the second regulating energy for charging and discharging the capacitor in the sending-end MMC based on the first voltage and the HVDC direct current includes: Determine a second voltage of the receiving-end MMC based on the first voltage and the DC current; A second regulating energy for charging and discharging the capacitor in the sending-end MMC is determined based on the second voltage.

6. The frequency support method for the new energy grid-connected system according to claim 5, characterized in that: The determining the second voltage of the receiving-end MMC based on the first voltage and the DC current includes: based on Determining a second voltage of the receiving-end MMC; Among them, V dc1_E represents the second voltage, V dc2 represents the first voltage, R dc The equivalent resistance of the MMC-HVDC DC line, I dc Represents the DC current, L dc represents the equivalent reactance of the MMC-HVDC DC line, d represents the derivative sign, and t represents time.

7. The frequency support method for the new energy grid-connected system according to claim 6, characterized in that: The determining, based on the second voltage, a second regulating energy for charging and discharging the capacitor in the sending-end MMC includes: based on Determine the second regulating energy for charging and discharging the capacitor in the sending-end MMC; Where ΔW E represents the second adjustment energy, k vw ' represents the DC voltage-energy droop control coefficient corresponding to the sending-end MMC, ΔV dcE Indicates the voltage deviation of the receiving MMC, V dc0 Indicates the DC voltage rating of the receiving-end MMC.

8. The frequency support method for a new energy grid-connected system according to claim 1, characterized in that: After the frequency of the new energy grid-connected system is regulated based on the first regulated energy and the second regulated energy, the method further includes: Based on ΔW=k w ΔW MMC , adjusting the total energy utilization rate of the receiving-end MMC to a preset value so that the capacitor voltage of the receiving-end MMC returns to the initial value; Wherein, ΔW represents the total energy utilization rate, k w Indicates the variable energy recovery factor; ΔW MMC represents the first adjustment energy.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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