Starting control method and device for new energy hybrid direct current transmission system

Abstract

The application relates to the technical field of new energy, and discloses a starting control method and device for a new energy hybrid DC transmission system. The method comprises the following steps: after the sending end flexible DC converter valve is unlocked, the sending end flexible DC converter valve is controlled to establish the sending end AC bus voltage in the form of zero step-up voltage amplitude and frequency control, so as to start the wind power plant; meanwhile, the active power output of the diesel generator-converter group is controlled, so that the DC voltage value of the sending end flexible DC converter valve or the average voltage value of all sub-modules in the sending end flexible DC converter valve is kept at the rated value. Then, the sending end flexible DC converter valve is controlled to slowly increase the amplitude value of the sending end bus AC voltage, to smoothly conduct the first diode valve and the second diode valve in the sending end converter station, and to complete the starting of the new energy hybrid DC transmission system. Through the application, the required equipment cost in the starting process is reduced, and a simplified and reliable starting control strategy is provided.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a startup control method and device for a new energy transmission system via hybrid DC power transmission. Background Technology

[0002] In flexible DC transmission systems for new energy, the sending-end flexible DC converter platform suffers from large size, heavy weight, and high cost. To achieve compactness, lightweight design, and cost reduction, while remaining compatible with both grid-connected and grid-connected wind turbines, a hybrid approach is adopted: diodes and flexible DC converter valves are connected in parallel on the AC side and in series on the DC side, or simply diodes and flexible DC converter valves are connected in parallel on the AC side. However, this introduces the black start problem. Existing technologies can achieve black start using thyristor converter valves, full-bridge submodules, or diesel generator-converter sets. However, thyristor converter valves carry the risk of commutation failure, full-bridge submodule configurations increase the cost of onshore flexible DC converter valves, and diesel generator-converter set solutions suffer from complex grid control function transition processes, difficulty in balancing filter switching timing during black start, and potential disturbances to the system. Therefore, there is an urgent need to research a low-cost, simple, and more reliable start control strategy. Summary of the Invention

[0003] In view of this, the present invention provides a startup control method and apparatus for a new energy transmission system via a hybrid DC power transmission system, in order to solve problems such as complex and unreliable startup control strategies.

[0004] In a first aspect, the present invention provides a startup control method for a new energy transmission system via a hybrid DC power transmission system. The system includes: a receiving-end power grid, a receiving-end converter station, a sending-end converter station, and sending-end new energy; the receiving-end power grid is connected to the receiving-end converter station; the receiving-end converter station is connected to the sending-end converter station; the sending-end converter station includes a first diode valve, a sending-end flexible DC converter valve, a second diode valve, a diesel generator-converter unit, and a sending-end AC bus; the first diode valve, the sending-end flexible DC converter valve, the second diode valve, and the diesel generator-converter unit are respectively connected to the sending-end AC bus.

[0005] The method includes:

[0006] After the sending-end flexible DC converter valve in the sending-end converter station is unlocked, the sending-end flexible DC converter valve is controlled to establish the sending-end AC bus voltage in a zero-start voltage rise manner through AC voltage amplitude and frequency control to start the wind farm; at the same time, the active power output of the diesel generator-converter set is controlled so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value.

[0007] The first and second diode valves in the converter station are turned on to start the new energy transmission system via hybrid DC transmission.

[0008] The method provided in this embodiment addresses the issue that, after the sending-end flexible DC converter valve in the sending-end converter station is unlocked, the DC side of the valve lacks energy support if AC voltage amplitude and frequency control is used, causing the DC voltage to drop rapidly and leading to system failure. Therefore, the diesel generator-converter unit provides energy to the sending-end flexible DC converter valve. However, the energy required by the sending-end flexible DC converter valve is dynamically changing. Thus, in this embodiment, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, reflects the change in the energy required by the sending-end flexible DC converter valve. By controlling the active power output of the diesel generator-converter unit, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value, thereby providing energy to the DC side of the sending-end flexible DC converter valve and achieving reliable system startup.

[0009] In one optional implementation, controlling the active power output of the diesel generator-converter unit such that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all submodules in the sending-end flexible DC converter valve, is maintained at a corresponding rated value includes:

[0010] When the DC voltage value of the feed-end flexible DC converter valve, or the average voltage value of all sub-modules in the feed-end flexible DC converter valve, changes, the feed-end flexible DC converter valve is controlled to change the angular frequency of the feed-end AC bus voltage.

[0011] When the angular frequency of the AC bus voltage at the sending end changes, the active power output of the diesel generator-converter unit is adjusted so that the DC voltage value of the sending end flexible DC converter valve, or the average voltage value of all sub-modules in the sending end flexible DC converter valve, remains at the corresponding rated value.

[0012] Through the above implementation method, the change in energy required by the sending-end flexible DC converter valve is reflected by the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve. Specifically, when the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, changes are detected, indicating a change in the energy required by the sending-end flexible DC converter valve. The angular frequency of the sending-end AC bus voltage is changed by controlling the sending-end flexible DC converter valve, which serves as a signal to adjust the active power output of the diesel generator-converter unit. This ensures that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value. In other words, when the energy required by the sending-end flexible DC converter valve changes, the diesel generator-converter unit can adjust the output active power in a timely manner to ensure the reliable operation of the sending-end flexible DC converter valve.

[0013] In one optional implementation, when the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all submodules in the sending-end flexible DC converter valve, changes, controlling the sending-end flexible DC converter valve to change the angular frequency of the sending-end AC bus voltage includes:

[0014] Based on the current DC voltage value and DC voltage reference value of the feed-end flexible DC converter valve, determine the change in DC voltage value of the feed-end flexible DC converter valve;

[0015] Based on the change in DC voltage value of the sending-end flexible DC converter valve, determine the change in the first angular frequency corresponding to the AC bus voltage at the sending end.

[0016] or,

[0017] Based on the average voltage value of all sub-modules in the feed-end flexible DC converter valve at the current moment and the average voltage reference value, determine the change in the average voltage value of all sub-modules in the feed-end flexible DC converter valve;

[0018] The second angular frequency change corresponding to the AC bus voltage at the sending end is determined based on the average voltage change of all sub-modules in the sending-end flexible DC converter valve.

[0019] Based on the change in the first or second angular frequency, the angular frequency of the AC bus voltage at the sending end is changed by controlling the flexible DC converter valve at the sending end.

[0020] In one optional implementation, determining the first angular frequency change corresponding to the AC bus voltage at the sending end based on the change in the DC voltage value of the sending-end flexible DC converter valve includes:

[0021] The first angular frequency change is determined by the change in DC voltage at the sending end of the flexible DC converter valve and the preset mapping relationship between the change in DC voltage and the change in angular frequency.

[0022] Through the above implementation method, by establishing a precise mapping relationship between the DC voltage change and the angular frequency change of the sending-end flexible DC converter valve, accurate closed-loop control of the voltage of the sending-end flexible DC converter valve is achieved. When the DC voltage or the average voltage of the submodule deviates from the reference value, the corresponding angular frequency change of the AC bus voltage can be quickly calculated, so that the angular frequency of the sending-end AC bus voltage responds, thereby flexibly adjusting the active power output of the diesel generator-converter set, ensuring the energy supply of the sending-end flexible DC converter valve, and providing a foundation for the reliable operation of the sending-end flexible DC converter valve.

[0023] In one optional implementation, when the angular frequency of the AC bus voltage at the sending end changes, the active power output of the diesel generator-converter unit is adjusted so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value, including:

[0024] When the angular frequency of the phase-locked loop output in the diesel generator-converter unit changes, it is determined that the angular frequency of the AC bus voltage at the sending end has changed.

[0025] Determine the target active power based on the angular frequency of the phase-locked loop output at the current moment;

[0026] Based on the target active power, control the diesel generator-converter unit so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value.

[0027] Through the above implementation method, the change in the angular frequency of the AC bus voltage at the sending end is sensed by the change in the angular frequency output of the phase-locked loop in the diesel generator-converter group, and the target active power is determined based on the angular frequency output of the phase-locked loop. This realizes the dynamic correlation between the angular frequency of the AC bus voltage at the sending end and the diesel generator-converter group, thereby realizing the correlation between the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, and the active power output of the diesel generator-converter group. In other words, it is the correlation between the energy required by the sending-end flexible DC converter valve and the active power output of the diesel generator-converter group, so that the diesel generator-converter group can provide a reliable energy supply to the sending-end flexible DC converter valve in a timely manner.

[0028] In one optional implementation, the target active power is determined based on the angular frequency output by the phase-locked loop at the current moment, including:

[0029] Determine the difference between the current angular frequency of the phase-locked loop output and the rated angular frequency;

[0030] The target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency.

[0031] In one optional implementation, the target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, including:

[0032] The target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, as well as the preset mapping relationship between the angular frequency difference and the active power.

[0033] Through the above implementation method, by establishing a mapping relationship between the angular frequency difference of the phase-locked loop output and the active power output of the diesel generator-converter group, precise control of the active power output of the diesel generator-converter group is achieved. Using the difference between the phase-locked loop output angular frequency and the rated angular frequency as the control basis, the energy change required by the sending-end flexible DC converter valve can be detected in a timely manner. Based on the preset mapping relationship, the active power of the diesel generator-converter group can be quickly determined, so that the active power output of the diesel generator-converter group can respond in a timely manner to the energy fluctuations required by the sending-end flexible DC converter valve, effectively maintaining the stable operation of the sending-end flexible DC converter valve.

[0034] In an alternative implementation, before the feed-end flexible-DC converter valve is unlocked, the method further includes:

[0035] The diesel generator-converter unit is controlled to charge the sending-end flexible DC converter valve by controlling the AC voltage amplitude and frequency to raise the voltage from zero.

[0036] After the sending-end flexible DC converter valve is fully charged, the control diesel generator-converter unit reduces the sending-end AC bus voltage to 0.

[0037] In one optional embodiment, the sending-end converter station further includes a first rectifier transformer, a sending-end flexible DC-DC converter, a second rectifier transformer, and a filter; a first diode valve is connected to the sending-end AC bus via the first rectifier transformer and a first circuit breaker in sequence; a sending-end flexible DC-DC converter valve is connected to the sending-end AC bus via the sending-end flexible DC-DC converter; a second diode valve is connected to the sending-end AC bus via the second rectifier transformer and a second circuit breaker in sequence; and a filter is connected to the sending-end AC bus via a third circuit breaker.

[0038] After the sending-end flexible DC converter valve is charged, and after the diesel generator-converter unit reduces the sending-end AC bus voltage to 0, before the sending-end flexible DC converter valve establishes the sending-end AC bus voltage through zero-start boost via AC voltage amplitude and frequency control, the method also includes:

[0039] Close the first circuit breaker, the second circuit breaker, and the third circuit breaker;

[0040] Unlock the feed end flexible DC converter valve.

[0041] Through the above implementation method, charging the converter valve using a zero-start voltage boost method via the diesel generator-converter set avoids the surge current impact of direct charging, ensuring the safety of components such as the capacitors in the converter valve's submodules and ensuring a stable and controllable charging process. Furthermore, after the sending-end flexible DC converter valve is fully charged, the diesel generator-converter set is controlled to reduce the sending-end AC bus voltage to 0, preventing inrush current when closing the switches of equipment connected to the sending-end AC bus voltage, effectively protecting equipment safety and improving system stability during startup.

[0042] Secondly, the present invention provides a start-up control device for a new energy transmission system via hybrid DC power transmission, used in a new energy transmission system via hybrid DC power transmission, the system comprising: a receiving-end power grid, a receiving-end converter station, a sending-end converter station, and sending-end new energy; the receiving-end power grid is connected to the receiving-end converter station; the receiving-end converter station is connected to the sending-end converter station, the sending-end converter station comprising a first diode valve, a sending-end flexible DC converter valve, a second diode valve, a diesel generator-converter unit, and a sending-end AC bus; the first diode valve, the sending-end flexible DC converter valve, the second diode valve, and the diesel generator-converter unit are respectively connected to the sending-end AC bus;

[0043] The device includes:

[0044] The control module is used to control the sending-end flexible DC converter valve in the sending-end converter station to establish the sending-end AC bus voltage in a zero-start manner after the sending-end flexible DC converter valve is unlocked, so as to start the wind farm; at the same time, it controls the active power output of the diesel generator-converter set so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value.

[0045] The conduction module is used to activate the first and second diode valves in the sending-end converter station, thereby enabling the startup of the new energy transmission system via hybrid DC power transmission.

[0046] With the device provided in this embodiment, after the sending-end flexible DC converter valve in the sending-end converter station is unlocked, considering that if the sending-end flexible DC converter valve adopts AC voltage amplitude and frequency control, its DC side lacks energy source support, and the DC voltage will drop rapidly, leading to system collapse, the diesel generator-converter group provides energy to the sending-end flexible DC converter valve. However, the energy required by the sending-end flexible DC converter valve is dynamically changing. Therefore, in this embodiment, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, reflects the change in the energy required by the sending-end flexible DC converter valve. By controlling the active power output of the diesel generator-converter group, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is kept at the corresponding rated value, thereby providing energy to the DC side of the sending-end flexible DC converter valve and realizing reliable system startup.

[0047] Thirdly, the present invention provides a computer device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the startup control method of the new energy transmission system via hybrid DC power transmission described in the first aspect or any corresponding embodiment.

[0048] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the startup control method of the new energy transmission system via hybrid DC transmission according to the first aspect or any corresponding embodiment described above.

[0049] Fifthly, the present invention provides a computer program product, including computer instructions, which are used to cause a computer to execute the startup control method of the new energy transmission system via hybrid DC power transmission according to the first aspect or any corresponding embodiment described above. Attached Figure Description

[0050] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 This is a circuit diagram of a new energy transmission system via hybrid DC power transmission according to an embodiment of the present invention;

[0052] Figure 2 This is a circuit diagram of another new energy transmission system via hybrid DC power transmission according to an embodiment of the present invention;

[0053] Figure 3 This is a flowchart of a startup control method for a new energy transmission system via a hybrid DC power transmission according to an embodiment of the present invention;

[0054] Figure 4 This is a schematic diagram illustrating the determination of angular frequency variation based on the DC voltage value of the feed-end flexible DC converter valve according to an embodiment of the present invention;

[0055] Figure 5 This is a schematic diagram illustrating the determination of angular frequency variation based on the average voltage value of all sub-modules of the feed-end flexible DC converter valve according to an embodiment of the present invention.

[0056] Figure 6This is a V / F control schematic diagram of how the angular frequency of the AC bus voltage at the sending end changes due to the control of the flexible DC converter valve at the sending end according to an embodiment of the present invention.

[0057] Figure 7 This is a schematic diagram illustrating the determination of target active power based on the angular frequency output by a phase-locked loop according to an embodiment of the present invention.

[0058] Figure 8 This is a schematic diagram of a diesel generator-converter unit based on target active power control according to an embodiment of the present invention;

[0059] Figure 9 This is a flowchart of a startup control method for a new energy transmission system via a hybrid DC power transmission system according to an embodiment of the present invention;

[0060] Figure 10 This is a schematic diagram of the start-up control device of a new energy transmission system via hybrid DC power transmission according to an embodiment of the present invention;

[0061] Figure 11 This is a schematic diagram of the structure of a computer device according to an embodiment of the present invention; Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] First, the application scenarios of the embodiments of this application will be introduced by way of example.

[0064] Currently, in flexible DC transmission systems for new energy, the sending-end flexible DC converter platform suffers from excessive size, weight, and cost. To achieve a compact and lightweight sending-end converter platform, reduce the cost of the sending-end converter valve, and ensure compatibility with both grid-connected and grid-connected wind turbines, related technologies involve connecting a diode in series with the Modular Multilevel Converter (MMC) on the DC side. This reduces the size, weight, and cost of the sending-end circulating platform. However, using MMC in series with the diode on the DC side requires overcoming a technical challenge: the black-start problem. This is because the unidirectional conduction characteristic of the diode makes it difficult for the hybrid valve to reverse power supply from the receiving end to the sending end to provide starting power for the converter platform and electric field, as is the case in a pure flexible DC system.

[0065] To achieve the return of starting power from the receiving end to the sending end, the first related technology uses a thyristor-controlled line commutated converter (LCC) valve at the onshore station. However, LCCs are prone to commutation failure, reducing power supply reliability. The second related technology uses flexible DC-DC converter valves with highly adjustable DC voltage at the onshore converter station, requiring a large number of full-bridge submodules, significantly increasing the cost of onshore flexible DC-DC converter valves. The third related technology utilizes existing small-capacity diesel generators on the offshore converter platform, configuring converter units into diesel-generator-converter groups. These diesel-generator-converter groups use grid control to charge the offshore auxiliary MMC and provide starting power for a small number of wind turbines. After the offshore auxiliary MMC is fully charged and the small number of wind turbines begin outputting power, the grid control function of the diesel-generator-converter group is transferred back to the offshore auxiliary MMC. While this startup method significantly reduces the additional costs associated with black starts, it presents two problems. First, the process of transferring the grid-connection control function of the diesel generator converter unit to the offshore auxiliary MMC is complex. Before the grid-connection function transfer, the diesel generator converter unit uses grid-connection control while the offshore auxiliary MMC uses grid-following control. Then, the offshore auxiliary MMC switches from grid-following control to grid-connection control. At this point, the diesel generator converter unit and the offshore auxiliary MMC jointly establish a grid, requiring a special joint grid-connection strategy to avoid conflicts between control variables. After both units have stably established a grid, the diesel generator converter unit is then switched back to grid-following control. This entire process involves the interplay of two types of equipment... Line switching and joint network construction are extremely complex. The second problem is the presence of large-capacity filters on the offshore AC bus. If the filters are engaged during the black start phase of the diesel generator-converter unit's voltage rise from zero, the converter unit needs to compensate for the filter's reactive power, resulting in an excessively high apparent power configuration for the converter, far exceeding the diesel generator's capacity. If the filters are engaged after the MMC (Mechanical Management Center) charging is complete, although the MMC can compensate for the filter's capacity, the system has already established a near-rated AC voltage. Engaging the filters at this point will inevitably cause a momentary drop in AC bus voltage, causing significant disturbance to the system, potentially leading to overvoltage, overcurrent, or even instability. Therefore, it is necessary to research low-cost, simple, and more reliable start-up control strategies.

[0066] In view of this, embodiments of this application provide a startup control method for a new energy transmission system via a hybrid DC power transmission system to solve problems such as complex and unreliable startup control strategies.

[0067] It should be noted that the method for starting control of a new energy transmission system via a hybrid DC power transmission system provided in this embodiment of the invention can be executed by a device for starting control of the new energy transmission system via a hybrid DC power transmission system. This device can be implemented as part or all of an electronic device through software, hardware, or a combination of both. The electronic device can be a server or a terminal. In this embodiment, the server can be a single server or a server cluster composed of multiple servers. The terminal in this embodiment can be a smartphone, personal computer, tablet computer, wearable device, or other intelligent hardware device such as an intelligent robot. The following method embodiments will use an electronic device as an example for explanation.

[0068] According to an embodiment of the present invention, a startup control method for a new energy transmission system via a hybrid DC power transmission system is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0069] Figure 1 This is a circuit diagram of a new energy source transmission system via hybrid DC transmission, according to an exemplary embodiment. The system includes: a receiving-end power grid 1, a receiving-end converter station 2, a sending-end converter station 3, and a sending-end new energy source (sending-end new energy power plant) 4; the receiving-end power grid 1 is connected to the receiving-end converter station 2; the receiving-end converter station 2 is connected to the sending-end converter station 3, and the sending-end converter station 3 includes a first diode valve 31, a sending-end Modular Multilevel Converter (MMC) valve 32, a second diode valve 33, a diesel generator-converter assembly 34, and a sending-end AC bus 35; the first diode valve 31, the sending-end Modular Multilevel Converter 32, the second diode valve 33, and the diesel generator-converter assembly 34 are respectively connected to the sending-end AC bus 35.

[0070] Specifically, receiving-end grid 1 refers to the target power grid that receives and consumes renewable energy power. Receiving-end grid 1 includes, but is not limited to, substations, transmission lines, load equipment, etc.

[0071] Sending-end new energy 4 refers to new energy power plants on the sending-end side, such as offshore wind farms and photovoltaic power plants. This application does not make specific limitations on sending-end new energy 4.

[0072] The receiving-end converter station 2 is used to convert DC power into AC power and connect it to the receiving-end power grid 1. For example, the receiving-end converter station 2 includes, but is not limited to, LCCs, flexible DC converter valves, etc.

[0073] The sending-end converter station 3 is a converter device that connects the sending-end renewable energy 4 to the DC transmission line. Taking offshore wind power as an example, the sending-end converter station 3 is an offshore converter station, which is connected to the sending-end converter station 3 via a DC submarine cable.

[0074] The diesel generator-converter unit 34 is a device consisting of a diesel generator and a converter connected in series, used for voltage / power support during the startup phase.

[0075] exist Figure 1 In this configuration, the first diode valve 31, the sending-end flexible DC converter valve 32, and the second diode valve 33 are connected in series on the DC side. The diesel generator-converter unit 34 includes a diesel generator (Generator) 341, a machine-side converter (MSC) 342, and a grid-side converter (GSC) 343. The diesel generator 341 is connected to the sending-end AC bus 35 in sequence through the machine-side converter 342, the grid-side converter 343, the transformer 42, and the fourth circuit breaker 43.

[0076] In addition, Figure 1 In the sending-end converter station 3, a first rectifier transformer 36, a sending-end flexible DC-DC converter 37, a second rectifier transformer 38, and a filter 39 are also included. A first diode valve 31 is connected to the sending-end AC bus 35 via the first rectifier transformer 36 and a first circuit breaker 40; a sending-end flexible DC-DC converter valve 32 is connected to the sending-end AC bus 35 via the sending-end flexible DC-DC converter 37; a second diode valve 33 is connected to the sending-end AC bus 35 via the second rectifier transformer 38 and the second circuit breaker 41; and a filter 39 is connected to the sending-end AC bus 35 via a third circuit breaker 44. Here, the filter 39 is used to filter out harmonic components on the AC side.

[0077] In the receiving-end converter station 2, the receiving-end converter station 2 includes a receiving-end flexible DC converter valve 21, which is connected to the receiving-end power grid 1 via a fifth circuit breaker 22, a receiving-end flexible DC connecting transformer 23, and a sixth circuit breaker 24 in sequence.

[0078] Of course, in addition to the above Figure 1 The first diode valve 31, the sending-end flexible DC converter valve 32, and the second diode valve 33 are connected in series on the DC side. The startup control method of the new energy transmission system via hybrid DC transmission provided in this application embodiment is also applicable to the mode in which the diode valve and the sending-end flexible DC converter valve are not connected on the DC side, that is, the first diode valve 31, the sending-end flexible DC converter valve 32, and the second diode valve 33 are connected in parallel only on the AC side, and are not connected on the DC side.

[0079] Figure 2 This is a circuit diagram of another new energy source transmission system via hybrid DC power transmission, based on an exemplary embodiment. Figure 2In addition to the connection method between the two diode valves and the feed-end flexible DC converter valve, Figure 1 Besides parallel connection on the AC side and series connection on the DC side, it can also be parallel connection only on the AC side, with no connection on the DC side. In addition, the receiving-end power grid, receiving-end converter station, sending-end converter station, and sending-end renewable energy units are connected to... Figure 1 The specific structure is similar, so it will not be described in detail here.

[0080] The startup control method for the new energy transmission system via hybrid DC power transmission provided in this application is applicable to the case where the sending-end diode valve and the sending-end flexible DC converter valve are connected in parallel on the AC side. The connection method of the sending-end diode valve and the sending-end flexible DC converter valve 32 on the DC side is not specifically limited.

[0081] Figure 3 This is a flowchart of a startup control method for a new energy transmission system via hybrid DC power transmission according to an embodiment of the present invention. The method is used in the above-mentioned... Figure 1 The new energy sources are transmitted through a hybrid DC transmission system. For example... Figure 3 As shown, the process includes the following steps:

[0082] S101: After the sending-end flexible DC converter valve 32 in the sending-end converter station 3 is unlocked, the sending-end flexible DC converter valve 32 is controlled to establish the sending-end AC bus voltage in a zero-start voltage boost manner through AC voltage amplitude and frequency control (V / F control) to start the wind farm; at the same time, the active power output of the diesel generator-converter group is controlled so that the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, is maintained at the corresponding rated value.

[0083] Specifically, AC voltage amplitude and frequency control refers to achieving precise control of the AC bus voltage at the sending end by adjusting the magnitude and frequency of the AC voltage output from the converter valve. Zero-start voltage boost refers to gradually increasing the AC voltage from 0 to the rated value to avoid inrush current.

[0084] Starting a wind farm means that at least some of the wind turbines in the wind farm are switched from a shutdown state to a power generation state.

[0085] The DC voltage value of the feed-end flexible DC converter valve 32 refers to the voltage across the DC side of the valve, reflecting the power balance state of the converter valve. The average voltage value of all sub-modules in the feed-end flexible DC converter valve 32 refers to the average value of the capacitor voltages of all sub-modules within the converter valve, used to measure the voltage balance of the sub-modules. The sub-modules in the feed-end flexible DC converter valve 32 can be either full-bridge or half-bridge sub-modules.

[0086] In one possible implementation, in S101 above, the diesel generator-converter unit adopts constant active power and constant reactive power control (P / Q control) to provide energy for transformer no-load loss, wind farm startup, etc.

[0087] S102: Turn on the first diode valve 31 and the second diode valve 33 in the sending-end converter station 3 to complete the startup of the new energy transmission system via hybrid DC power transmission.

[0088] In one possible implementation, in S102 above, the voltage of the sending-end flexible DC converter valve 32 is raised to the sending-end AC bus 35 until the second diode valve 33 is turned on, and the diesel generator-converter set 34 is taken out of operation.

[0089] According to the method provided in this embodiment, after the sending-end flexible DC converter valve 32 in the sending-end converter station 3 is unlocked, considering that if the sending-end flexible DC converter valve 32 adopts AC voltage amplitude and frequency control, its DC side lacks energy source support, and the DC voltage will drop rapidly, causing the system to collapse, it is necessary for the diesel generator-converter group to provide energy to the sending-end flexible DC converter valve 32. However, the energy required by the sending-end flexible DC converter valve 32 is dynamically changing. Therefore, in this embodiment, the change in the energy required by the sending-end flexible DC converter valve 32 is reflected by the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32. By controlling the active power output of the diesel generator-converter group, the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, is kept at the corresponding rated value, thereby providing energy to the DC side of the sending-end flexible DC converter valve 32 and realizing reliable system startup.

[0090] In some embodiments, in S101 above, the active power output of the diesel generator-converter group is controlled in such a way that the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, is maintained at the corresponding rated value:

[0091] a1: When the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, changes, the sending-end flexible DC converter valve 32 is controlled to change the angular frequency of the sending-end AC bus voltage.

[0092] In one possible implementation, in a1 above, when the DC voltage value of the sending-end flexible DC converter valve 32 changes, the sending-end flexible DC converter valve 32 is controlled to change the angular frequency of the sending-end AC bus voltage.

[0093] In another possible implementation, in a1 above, when the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32 changes, the sending-end flexible DC converter valve 32 is controlled to change the angular frequency of the sending-end AC bus voltage.

[0094] a2: When the angular frequency of the AC bus voltage at the sending end changes, adjust the active power output of the diesel generator-converter set so that the DC voltage value of the sending end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending end flexible DC converter valve 32, remains at the corresponding rated value.

[0095] In this embodiment, the change in energy required by the sending-end flexible DC converter valve 32 is reflected by the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32. Specifically, when the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, changes occur, it is determined that the energy required by the sending-end flexible DC converter valve 32 has changed. The angular frequency of the sending-end AC bus voltage is changed by controlling the sending-end flexible DC converter valve 32 as a signal to adjust the active power output of the diesel generator-converter set. This ensures that the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, remains at the corresponding rated value. That is, when the energy required by the sending-end flexible DC converter valve 32 changes, the diesel generator-converter set can adjust the output active power in a timely manner to ensure the reliable operation of the sending-end flexible DC converter valve 32.

[0096] In one possible implementation, in a1 above, the angular frequency of the AC bus voltage at the sending end is changed by controlling the sending-end flexible DC converter valve 32 as follows: b1-b2

[0097] b1: Determine the change in DC voltage value of the sending-end flexible DC converter valve 32 based on the current DC voltage value and DC voltage reference value of the sending-end flexible DC converter valve 32, or determine the change in average voltage value of all sub-modules in the sending-end flexible DC converter valve 32 based on the current average voltage value and average voltage reference value of all sub-modules in the sending-end flexible DC converter valve 32.

[0098] For example, the difference between the DC voltage value of the feed-end flexible DC converter valve 32 and the DC voltage reference value is used to obtain the change in the DC voltage value of the feed-end flexible DC converter valve 32.

[0099] For example, the average voltage value of all submodules in the sending-end flexible DC converter valve 32 at the current moment is subtracted from the average voltage reference value to obtain the change in the average voltage value of the sending-end flexible DC converter valve 32.

[0100] b2: Determine the first angular frequency change corresponding to the AC bus voltage at the sending end based on the change in the DC voltage value of the sending end flexible DC converter valve 32, or determine the second angular frequency change corresponding to the AC bus voltage at the sending end based on the average voltage value change of all sub-modules in the sending end flexible DC converter valve 32.

[0101] Optionally, the first angular frequency change can be determined by the change in DC voltage of the sending-end flexible DC converter valve 32 and the preset mapping relationship between the change in DC voltage and the change in angular frequency.

[0102] For example, based on the change in DC voltage value of the sending-end flexible DC converter valve 32 and the preset mapping relationship between the change in DC voltage value and the change in angular frequency, the first angular frequency change is determined by a proportional-integral controller.

[0103] Optionally, the second angular frequency change can be determined by the average voltage change of all sub-modules in the sending-end flexible DC converter valve 32 and the preset mapping relationship between the average voltage change and the angular frequency change.

[0104] b3: Based on the change in the first angular frequency or the change in the second angular frequency, control the sending end flexible DC converter valve 32 to change the angular frequency of the sending end AC bus voltage.

[0105] Figure 4 This is a schematic diagram illustrating the determination of angular frequency variation based on the DC voltage value of the feed-end flexible DC converter valve. Figure 4 middle, U dcref This is the reference value for the DC voltage of the feed-end flexible DC converter valve. U dc The DC voltage value of the feed-end flexible DC converter valve is 1 / (1+ sT um ) is a low-pass filter, PI is a proportional-integral controller, Δ ω This represents the angular frequency change of the AC bus voltage at the sending end. For example... Figure 4 As shown, the sending-end flexible DC converter valve 32 further determines the Park transition angle of the fundamental frequency to be controlled based on the angular frequency change of the sending-end AC bus voltage. Among them, ω N The rated angular frequency, ω PCC The angular frequency value of the AC bus voltage at the sending end that needs to be controlled by the sending-end flexible DC converter valve 32 is 1 / s For the integration module, θ g Park transformation angle for the fundamental frequency electrical quantities on the transformer grid side controlled by the sending-end flexible DC converter valve 32. θ T The phase angle difference between the valve-side winding and the grid-side winding of transformer 37 is the result of the flexible direct connection at the sending end. θ v The Park conversion angle is the fundamental frequency electrical quantity on the transformer valve side controlled by the sending-end flexible DC converter valve 32.

[0106] Figure 5 A schematic diagram for determining the angular frequency change based on the average voltage value of all submodules of the feed-end flexible DC converter valve. U SMref This is the average voltage reference value for all submodules of the feed-end flexible DC converter valve. U SM_av The average voltage value across all submodules; PI is a proportional-integral controller; Δ ω This represents the change in angular frequency of the AC bus voltage at the sending end. ω N Rated angular frequency, ω PCC The angular frequency value of the AC bus voltage at the sending end that needs to be controlled by the sending-end flexible DC converter valve 32 is 1 / s For the integration module, θ g Park transformation angle for the fundamental frequency electrical quantities on the transformer grid side controlled by the sending-end flexible DC converter valve 32. θ T The phase angle difference between the valve-side winding and the grid-side winding of transformer 37 is the result of the flexible direct connection at the sending end. θ v The Park conversion angle is the fundamental frequency electrical quantity on the transformer valve side controlled by the sending-end flexible DC converter valve 32.

[0107] exist Figure 6 In China, based on Figure 4 or Figure 5 Determined transformation angle θ v The angular frequency of the AC bus voltage at the sending end is changed by controlling the flexible DC converter valve at the sending end. V dref , V qref These are the reference values ​​for the d-axis and q-axis components of the AC bus voltage at the sending end, respectively. V gd , V gq These are the measured values ​​of the d-axis and q-axis components of the AC bus voltage at the sending end, respectively. I dref , I qref These are the reference values ​​for the d-axis and q-axis components of the AC side current of the feed-end flexible DC converter valve 32, respectively. e cd , e cq They are respectively I dref , Iqref The d-axis and q-axis components of the AC voltage reference value output by the grid-side converter are used as the input current of the control command input loop control circuit. e aref , e bref , e cref These are the reference values ​​for the three-phase AC voltage output from the sending-end MMC; e cira , e cirb , e circ It is the reference value of the three-phase double-frequency AC voltage of the MMC output terminal after circulating current suppression control; P 1 represents the Park transformation; N ap , N an , N bp , N bn , N cp , N cn These are reference values ​​for the number of submodules required to be put into operation for the 32 three-phase 6-arm flexible DC converter valve at the sending end, which is output by Nearest Level Modulation (NLM); PI are all proportional-integral controllers.

[0108] In this embodiment, by establishing a precise mapping relationship between the voltage change and angular frequency change of the sending-end flexible DC converter valve 32, accurate closed-loop control of the voltage of the sending-end flexible DC converter valve 32 is achieved. When the DC voltage or the average voltage of the submodule deviates from the reference value, the corresponding angular frequency change of the AC bus voltage can be quickly calculated, so that the angular frequency of the sending-end AC bus voltage responds, thereby flexibly adjusting the active power output of the diesel generator-converter set, ensuring the energy supply of the sending-end flexible DC converter valve, and providing a foundation for the reliable operation of the sending-end flexible DC converter valve.

[0109] In one possible implementation, in a2 above, the active power output of the diesel generator-converter unit is adjusted by c1-c3 as follows:

[0110] c1: When the angular frequency of the phase-locked loop output in the diesel generator-converter unit 34 changes, it is determined that the angular frequency of the AC bus voltage at the sending end has changed.

[0111] c2: Determine the target active power based on the angular frequency output by the phase-locked loop at the current moment.

[0112] Optionally, in c2 above, the target active power is determined by the following:

[0113] First, determine the difference between the current angular frequency output by the phase-locked loop and the rated angular frequency.

[0114] Then, the target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency.

[0115] For example, the target active power can be determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, as well as the preset mapping relationship between the angular frequency difference and the active power.

[0116] For example, the target active power is determined by a proportional-integral controller based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, as well as the preset mapping relationship between the angular frequency difference and the active power.

[0117] Figure 7 This is a schematic diagram of determining the target active power based on the angular frequency of the phase-locked loop output. ω N The rated angular frequency, ω PLL The angular frequency of the phase-locked loop output is 1 / (1+ sT um () is a low-pass filter, and PI is a proportional-integral controller. P ref The target active power. Figure 7 In this process, the target active power of the diesel generator-converter unit is determined by the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, as well as the preset mapping relationship between the angular frequency difference and the active power in the proportional-integral controller.

[0118] In this way, by establishing a mapping relationship between the angular frequency difference of the phase-locked loop output and the active power output of the diesel generator-converter unit, precise control of the active power output of the diesel generator-converter unit is achieved. Using the difference between the phase-locked loop output angular frequency and the rated angular frequency as the control basis, the energy change required by the sending-end flexible DC converter valve can be detected in a timely manner. Based on the preset mapping relationship, the active power of the diesel generator-converter unit can be quickly determined, so that the active power output of the diesel generator-converter unit can respond in a timely manner to the energy fluctuations required by the sending-end flexible DC converter valve, effectively maintaining the stable operation of the sending-end flexible DC converter valve.

[0119] c3: Based on the target active power, control the diesel generator-converter group 34 so that the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, is maintained at the corresponding rated value.

[0120] Figure 8This is a schematic diagram of a diesel generator-converter unit controlled based on a target active power output. Figure 8 In China, based on such Figure 7 The target active power is determined by the method, and the diesel generator-converter unit is controlled. Among them, P ref , Q ref These are the reference values ​​for the active and reactive power outputs of the grid-side converter, respectively. P , Q These are the measured values ​​of active and reactive power output from the grid-side converter, respectively. I dref , I qref These are the reference commands for the d-axis and q-axis components of the AC side current of the grid-side converter, respectively. e cd , e cq They are respectively I dref , I qref The d-axis and q-axis components of the AC voltage reference value output by the grid-side converter are used as the input current of the control command input loop control circuit. e aref , e bref e cref These are the reference values ​​for the three-phase AC voltage output from the grid-side converter; G 1. G 2. G 3. G 4. G 5. G 6 are the trigger pulse signals of the three-phase 6-arm bridge of the grid-side converter, which are output by pulse width modulation (PWM). P 1 is the Park transformation; 1 / (1+ sT um ) represents a filter; U gq These are the measured values ​​of the q-axis component of the AC side voltage at the grid connection point of the grid-side converter; all PI controllers are proportional-integral controllers. ω N It is the rated angular frequency; ω PLL The angular frequency of the phase-locked loop output; 1 / s For integration modules; θ The Park transformation angle is the base frequency electrical quantity of the converter on the grid side of the diesel generator-converter network.

[0121] In this embodiment, the change in the angular frequency of the AC bus voltage at the sending end is sensed by the change in the angular frequency output of the phase-locked loop in the diesel generator-converter group, and the target active power is determined based on the angular frequency output of the phase-locked loop. This realizes the dynamic correlation between the angular frequency of the AC bus voltage at the sending end and the diesel generator-converter group, thereby realizing the correlation between the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, and the active power output of the diesel generator-converter group. That is, the correlation between the energy required by the sending-end flexible DC converter valve and the active power output of the diesel generator-converter group, so that the diesel generator-converter group can provide a reliable energy supply to the sending-end flexible DC converter valve in a timely manner.

[0122] In some embodiments, before the feed-end flexible-DC converter valve 32 is unlocked, the start-up control method provided in this application embodiment further includes the following:

[0123] First, the diesel generator-converter unit 34 is controlled to charge the sending-end flexible DC converter valve 32 by controlling the AC voltage amplitude and frequency in a zero-start voltage boost manner.

[0124] Specifically, the diesel generator-converter unit 34 uses V / F control to boost voltage from zero, charging the submodule capacitor in the sending-end flexible DC converter valve 32.

[0125] Then, after the sending-end flexible DC converter valve 32 has finished charging, the control diesel generator-converter unit 34 reduces the sending-end AC bus voltage to 0.

[0126] In some embodiments, after the sending-end flexible DC converter valve 32 has finished charging, and after the diesel generator-converter group 34 controls the sending-end AC bus voltage to drop to 0, before controlling the sending-end flexible DC converter valve 32 to establish the sending-end AC bus voltage in a zero-start boost manner through AC voltage amplitude and frequency control, the method provided in this application embodiment further includes the following:

[0127] First, close the first circuit breaker 40, the second circuit breaker 41, and the third circuit breaker 44.

[0128] Then, unlock the feed end flexible DC converter valve 32.

[0129] Through the above implementation method, charging the converter valve using a zero-start voltage boost method via the diesel generator-converter set avoids the surge current impact of direct charging, ensuring the safety of components such as the capacitors in the converter valve's submodules and ensuring a stable and controllable charging process. Furthermore, after the sending-end flexible DC converter valve is fully charged, the diesel generator-converter set is controlled to reduce the sending-end AC bus voltage to 0, preventing inrush current when closing the switches of equipment connected to the sending-end AC bus voltage, effectively protecting equipment safety and improving system stability during startup.

[0130] Figure 9 This is a flowchart of a startup control method for a new energy source transmission system via a hybrid DC power transmission line. (For example...) Figure 9 As shown, the method includes the following:

[0131] S901: Controls the diesel generator-converter unit 34 to charge the sending-end flexible DC converter valve 32 in a zero-start voltage boost manner through AC voltage amplitude and frequency control.

[0132] S902: After the sending-end flexible DC converter valve 32 has finished charging, control the diesel generator-converter group 34 to reduce the sending-end AC bus voltage to 0.

[0133] S903: Close the first circuit breaker 40, the second circuit breaker 41, and the third circuit breaker 44, and unlock the sending-end flexible DC converter valve 32 in the sending-end converter station.

[0134] S904: The sending-end flexible DC converter valve 32 maps and transmits the DC voltage value of the sending-end flexible DC converter valve 32, or the change in the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, by controlling the change in the angular frequency of the sending-end AC bus voltage. Further, the grid-side converter in the diesel generator-converter group 34 is controlled to adjust the active power output based on the change in the angular frequency of the phase-locked loop output, until the DC voltage value of the sending-end flexible DC converter valve 32, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve 32, recovers and remains at the rated value.

[0135] S905: Turns on the first diode valve 31 and the second diode valve 33 in the sending-end converter station to complete the startup of the new energy transmission system via hybrid DC power transmission.

[0136] In this application embodiment, a dynamic coordination control strategy for energy between the sending-end flexible DC converter valve and the diesel generator-converter group is proposed, which significantly reduces the cost of additional equipment required for black start. The control strategy is simple and easy to implement, and has high reliability and stability during black start.

[0137] The above mainly describes the solution provided by the embodiments of this application from a methodological perspective.

[0138] This application also provides a startup control device for a new energy transmission system via a hybrid DC power transmission line. This device is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0139] This invention provides a start-up control device for a new energy transmission system via hybrid DC power transmission. The system includes: a receiving-end power grid, a receiving-end converter station, a sending-end converter station, and sending-end new energy. The receiving-end power grid is connected to the receiving-end converter station. The receiving-end converter station is connected to the sending-end converter station. The sending-end converter station includes a first diode valve, a sending-end flexible DC converter valve, a second diode valve, a diesel generator-converter unit, and a sending-end AC bus. The first diode valve, the sending-end flexible DC converter valve, the second diode valve, and the diesel generator-converter unit are respectively connected to the sending-end AC bus. Figure 10 As shown, the device includes:

[0140] The control module 1001 is used to control the sending-end flexible DC converter valve to establish the sending-end AC bus voltage in a zero-start-up manner after the sending-end flexible DC converter valve in the sending-end converter station is unlocked, so as to start the wind farm; at the same time, it controls the active power output of the diesel generator-converter set so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value.

[0141] The conduction module 1002 is used to conduct the first diode valve and the second diode valve in the sending-end converter station to complete the startup of the new energy transmission system via hybrid DC transmission.

[0142] With the device provided in this embodiment, after the sending-end flexible DC converter valve in the sending-end converter station is unlocked, considering that if the sending-end flexible DC converter valve adopts AC voltage amplitude and frequency control, its DC side lacks energy source support, and the DC voltage will drop rapidly, leading to system collapse, the diesel generator-converter group provides energy to the sending-end flexible DC converter valve. However, the energy required by the sending-end flexible DC converter valve is dynamically changing. Therefore, in this embodiment, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, reflects the change in the energy required by the sending-end flexible DC converter valve. By controlling the active power output of the diesel generator-converter group, the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is kept at the corresponding rated value, thereby providing energy to the DC side of the sending-end flexible DC converter valve and realizing reliable system startup.

[0143] In some optional implementations, the control module 1001 is specifically used to control the sending-end flexible DC converter valve to change the angular frequency of the sending-end AC bus voltage when the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, changes.

[0144] When the angular frequency of the AC bus voltage at the sending end changes, the active power output of the diesel generator-converter unit is adjusted so that the DC voltage value of the sending end flexible DC converter valve, or the average voltage value of all sub-modules in the sending end flexible DC converter valve, remains at the corresponding rated value.

[0145] In some optional implementations, the control module 1001 is specifically used to determine the change in the DC voltage value of the sending-end flexible DC converter valve based on the DC voltage value of the sending-end flexible DC converter valve at the current moment and the DC voltage reference value.

[0146] Based on the change in DC voltage value of the sending-end flexible DC converter valve, determine the change in the first angular frequency corresponding to the AC bus voltage at the sending end.

[0147] or,

[0148] Based on the average voltage value of all sub-modules in the feed-end flexible DC converter valve at the current moment and the average voltage reference value, determine the change in the average voltage value of all sub-modules in the feed-end flexible DC converter valve;

[0149] The second angular frequency change corresponding to the AC bus voltage at the sending end is determined based on the average voltage change of all sub-modules in the sending-end flexible DC converter valve.

[0150] Based on the change in the first or second angular frequency, the angular frequency of the AC bus voltage at the sending end is changed by controlling the flexible DC converter valve at the sending end.

[0151] In some optional implementations, the control module 1001 is specifically used to determine the first angular frequency change by means of the change in DC voltage value of the sending-end flexible DC converter valve and a preset mapping relationship between the change in DC voltage value and the change in angular frequency.

[0152] In some alternative implementations, the control module 1001 is specifically used to determine that the angular frequency of the AC bus voltage at the sending end changes when the angular frequency of the phase-locked loop output in the diesel generator-converter unit changes.

[0153] Determine the target active power based on the angular frequency of the phase-locked loop output at the current moment;

[0154] Based on the target active power, control the diesel generator-converter unit so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value.

[0155] In some alternative implementations, the control module 1001 is specifically used to determine the difference between the current angular frequency output by the phase-locked loop and the rated angular frequency.

[0156] The target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency.

[0157] In some optional implementations, the control module 1001 is specifically used to determine the target active power based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, and a preset mapping relationship between the angular frequency difference and the active power.

[0158] In some alternative implementations, the control module 1001 is also configured to control the diesel generator-converter unit to charge the sending-end flexible DC converter valve in a zero-start boost manner by controlling the AC voltage amplitude and frequency before the sending-end flexible DC converter valve is unlocked.

[0159] After the sending-end flexible DC converter valve is fully charged, the control diesel generator-converter unit reduces the sending-end AC bus voltage to 0.

[0160] In some optional embodiments, the sending-end converter station further includes a first rectifier transformer, a sending-end flexible DC-DC converter, a second rectifier transformer, and a filter; a first diode valve is connected to the sending-end AC bus via the first rectifier transformer and a first circuit breaker in sequence; the sending-end flexible DC-DC converter valve is connected to the sending-end AC bus via the sending-end flexible DC-DC converter; a second diode valve is connected to the sending-end AC bus via the second rectifier transformer and a second circuit breaker in sequence; the filter is connected to the sending-end AC bus via a third circuit breaker; the control module 1001 is further configured to, after the sending-end flexible DC-DC converter valve has been charged and the diesel generator-converter group has reduced the sending-end AC bus voltage to 0, and before the sending-end flexible DC-DC converter valve establishes the sending-end AC bus voltage by zero-start voltage boost through AC voltage amplitude and frequency control, close the first circuit breaker, the second circuit breaker, and the third circuit breaker; and unlock the sending-end flexible DC-DC converter valve.

[0161] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0162] In this embodiment, the start-up control device of the new energy transmission system via hybrid DC power transmission is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0163] This invention also provides a computer device having the above-described features. Figure 10 The shown is the start-up control device for the new energy transmission system via hybrid DC power transmission.

[0164] Please see Figure 11 , Figure 11This is a schematic diagram of the structure of a computer device provided in an optional embodiment of the present invention, such as... Figure 11 As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 11 Take a processor 10 as an example.

[0165] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0166] The memory 20 stores instructions executable by at least one processor 10 to cause at least one processor 10 to perform the method shown in the above embodiments.

[0167] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0168] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0169] The computer device also includes a communication interface 30 for communicating with other devices or communication networks.

[0170] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0171] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0172] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A startup control method for a new energy transmission system via hybrid DC power transmission, characterized in that, This system is used for transmitting new energy via a hybrid DC power transmission system. The system includes: a receiving-end power grid, a receiving-end converter station, a sending-end converter station, and sending-end new energy. The receiving-end power grid is connected to the receiving-end converter station. The receiving-end converter station is connected to the sending-end converter station. The sending-end converter station includes a first diode valve, a sending-end flexible DC converter valve, a second diode valve, a diesel generator-converter unit, and a sending-end AC bus. The first diode valve, the sending-end flexible DC converter valve, the second diode valve, and the diesel generator-converter unit are respectively connected to the sending-end AC bus. The method includes: After the sending-end flexible DC converter valve in the sending-end converter station is unlocked, the sending-end flexible DC converter valve is controlled to establish the sending-end AC bus voltage in a zero-start voltage rise manner through AC voltage amplitude and frequency control to start the wind farm; at the same time, the active power output of the diesel generator-converter set is controlled so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value; By turning on the first diode valve and the second diode valve in the sending-end converter station, the startup of the new energy transmission system via hybrid DC power transmission is completed. The control of the active power output of the diesel generator-converter set ensures that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value, including: When the DC voltage value of the feed-end flexible DC converter valve, or the average voltage value of all sub-modules in the feed-end flexible DC converter valve, changes, the feed-end flexible DC converter valve is controlled to change the angular frequency of the feed-end AC bus voltage. When the angular frequency of the AC bus voltage at the sending end changes, the active power output of the diesel generator-converter set is adjusted so that the DC voltage value of the sending end flexible DC converter valve, or the average voltage value of all sub-modules in the sending end flexible DC converter valve, remains at the corresponding rated value. When the DC voltage value of the feed-end flexible DC converter valve, or the average voltage value of all sub-modules in the feed-end flexible DC converter valve, changes, controlling the feed-end flexible DC converter valve to change the angular frequency of the feed-end AC bus voltage includes: Based on the current DC voltage value and DC voltage reference value of the feed-end flexible DC converter valve, determine the change in DC voltage value of the feed-end flexible DC converter valve; Based on the change in DC voltage value of the sending-end flexible DC converter valve, determine the change in the first angular frequency corresponding to the AC bus voltage at the sending end. or, Based on the average voltage value and average voltage reference value of all sub-modules in the feed-end flexible DC converter valve at the current moment, determine the change in the average voltage value of all sub-modules in the feed-end flexible DC converter valve; The second angular frequency change corresponding to the AC bus voltage at the sending end is determined based on the average voltage change of all sub-modules in the sending-end flexible DC converter valve. Based on the first angular frequency change or the second angular frequency change, the sending-end flexible DC converter valve is controlled to change the angular frequency of the sending-end AC bus voltage.

2. The method according to claim 1, characterized in that, The step of determining the change in the first angular frequency corresponding to the AC bus voltage at the sending end based on the change in the DC voltage value of the sending-end flexible DC converter valve includes: The first angular frequency change is determined by the change in DC voltage of the sending-end flexible DC converter valve and the preset mapping relationship between the change in DC voltage and the change in angular frequency.

3. The method according to claim 1, characterized in that, When the angular frequency of the AC bus voltage at the sending end changes, adjusting the active power output of the diesel generator-converter unit so that the DC voltage value of the sending end flexible DC converter valve, or the average voltage value of all sub-modules in the sending end flexible DC converter valve, remains at the corresponding rated value, includes: If the angular frequency of the phase-locked loop output in the diesel generator-converter unit changes, it is determined that the angular frequency of the AC bus voltage at the sending end has changed. Determine the target active power based on the angular frequency output by the phase-locked loop at the current moment; Based on the target active power, the diesel generator-converter group is controlled so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value.

4. The method according to claim 3, characterized in that, Determining the target active power based on the angular frequency output by the phase-locked loop at the current moment includes: Determine the difference between the current angular frequency output by the phase-locked loop and the rated angular frequency; The target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency.

5. The method according to claim 4, characterized in that, Determining the target active power based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency includes: The target active power is determined based on the difference between the angular frequency output by the phase-locked loop and the rated angular frequency, and the preset mapping relationship between the angular frequency difference and the active power.

6. The method according to any one of claims 1-5, characterized in that, Before the feed-end flexible DC converter valve is unlocked, the method further includes: The diesel generator-converter unit is controlled to charge the sending-end flexible DC converter valve in a zero-start voltage boost manner through AC voltage amplitude and frequency control. After the sending-end flexible DC converter valve is charged, the diesel generator-converter set is controlled to reduce the sending-end AC bus voltage to 0.

7. The method according to claim 6, characterized in that, The sending-end converter station further includes a first rectifier transformer, a sending-end flexible DC-DC converter, a second rectifier transformer, and a filter; the first diode valve is connected to the sending-end AC bus via the first rectifier transformer and a first circuit breaker in sequence; the sending-end flexible DC-DC converter valve is connected to the sending-end AC bus via the sending-end flexible DC-DC converter; the second diode valve is connected to the sending-end AC bus via the second rectifier transformer and a second circuit breaker in sequence; and the filter is connected to the sending-end AC bus via a third circuit breaker. After the sending-end flexible DC converter valve has been charged and the diesel generator-converter unit has reduced the sending-end AC bus voltage to 0, and before the sending-end flexible DC converter valve has been controlled to establish the sending-end AC bus voltage by zero-start boost through AC voltage amplitude and frequency control, the method further includes: Close the first circuit breaker, the second circuit breaker, and the third circuit breaker; Unlock the feed end flexible DC converter valve.

8. A start-up control device for a new energy transmission system via hybrid DC power transmission, characterized in that, This system is used for transmitting new energy via a hybrid DC power transmission system. The system includes: a receiving-end power grid, a receiving-end converter station, a sending-end converter station, and sending-end new energy. The receiving-end power grid is connected to the receiving-end converter station. The receiving-end converter station is connected to the sending-end converter station. The sending-end converter station includes a first diode valve, a sending-end flexible DC converter valve, a second diode valve, a diesel generator-converter unit, and a sending-end AC bus. The first diode valve, the sending-end flexible DC converter valve, the second diode valve, and the diesel generator-converter unit are respectively connected to the sending-end AC bus. The device includes: The control module is used to control the sending-end flexible DC converter valve in the sending-end converter station to establish the sending-end AC bus voltage in a zero-start manner after the sending-end flexible DC converter valve is unlocked, so as to start the wind farm; at the same time, it controls the active power output of the diesel generator-converter set so that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, is maintained at the corresponding rated value. The conduction module is used to activate the first diode valve and the second diode valve in the sending-end converter station to complete the startup of the new energy transmission system via hybrid DC power transmission. The control of the active power output of the diesel generator-converter set ensures that the DC voltage value of the sending-end flexible DC converter valve, or the average voltage value of all sub-modules in the sending-end flexible DC converter valve, remains at the corresponding rated value, including: When the DC voltage value of the feed-end flexible DC converter valve, or the average voltage value of all sub-modules in the feed-end flexible DC converter valve, changes, the feed-end flexible DC converter valve is controlled to change the angular frequency of the feed-end AC bus voltage. When the angular frequency of the AC bus voltage at the sending end changes, the active power output of the diesel generator-converter set is adjusted so that the DC voltage value of the sending end flexible DC converter valve, or the average voltage value of all sub-modules in the sending end flexible DC converter valve, remains at the corresponding rated value. When the DC voltage value of the feed-end flexible DC converter valve, or the average voltage value of all sub-modules in the feed-end flexible DC converter valve, changes, controlling the feed-end flexible DC converter valve to change the angular frequency of the feed-end AC bus voltage includes: Based on the current DC voltage value and DC voltage reference value of the feed-end flexible DC converter valve, determine the change in DC voltage value of the feed-end flexible DC converter valve; Based on the change in DC voltage value of the sending-end flexible DC converter valve, determine the change in the first angular frequency corresponding to the AC bus voltage at the sending end. or, Based on the average voltage value and average voltage reference value of all sub-modules in the feed-end flexible DC converter valve at the current moment, determine the change in the average voltage value of all sub-modules in the feed-end flexible DC converter valve; The second angular frequency change corresponding to the AC bus voltage at the sending end is determined based on the average voltage change of all sub-modules in the sending-end flexible DC converter valve. Based on the first angular frequency change or the second angular frequency change, the sending-end flexible DC converter valve is controlled to change the angular frequency of the sending-end AC bus voltage.

9. A computer device, characterized in that, The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the steps of the startup control method for the new energy transmission system via hybrid DC power transmission as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the startup control method for the new energy transmission system via hybrid DC power transmission as described in any one of claims 1-7.

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