Valve control method for a direct current energy consuming device

Abstract

The application discloses a valve control method of a direct current energy consumption device, and relates to the technical field of direct current transmission control. The direct current energy consumption device comprises at least one energy consumption valve and at least one energy consumption resistor, and the at least one energy consumption valve and the at least one energy consumption resistor are arranged in series between positive and negative electrode lines. The valve control method of the direct current energy consumption device comprises the following steps: obtaining an initial direct current voltage signal between the positive and negative electrode lines, and obtaining a corresponding target direct current voltage signal based on the initial direct current voltage signal; comparing the target direct current voltage signal with an input action voltage threshold value of the direct current energy consumption device, and controlling the at least one energy consumption valve to be turned on in the case that the target direct current voltage signal is higher than the input action voltage threshold value; and comparing the target direct current voltage signal with a removal action voltage threshold value of the direct current energy consumption device, and controlling the at least one energy consumption valve to be turned off in the case that the target direct current voltage signal is lower than the removal action voltage threshold value. According to the embodiment of the application, the reliability of the valve control action of the direct current energy consumption device can be improved.

Description

Technical Field

[0001] This application belongs to the field of DC power transmission control technology, and in particular relates to a valve control method for a DC energy consumption device. Background Technology

[0002] High voltage direct current (HVDC) transmission based on modular multilevel converters (MMC-HVDC) features independent regulation of active and reactive power, passive power supply capability, and ease of DC grid construction. It has been widely used for long-distance transmission of large-scale offshore wind power, and large-capacity long-distance offshore wind power DC grid connection will become the main trend for the future development of offshore wind power.

[0003] For offshore wind farm MMC-HVDC grid-connected systems, when a fault in the receiving-end grid AC system causes a drop in AC voltage, the active power transferred from the grid-side converter to the grid decreases accordingly. If the wind turbine's wind energy capture and generated active power remain unchanged, and the active power transferred from the wind farm to the wind farm-side converter remains unchanged, the entire system will generate unbalanced power, which will charge the MMC submodule capacitors, causing the DC voltage to rise rapidly and affecting the safe and stable operation of the MMC-HVDC. In severe cases, it can lead to the wind turbine disconnecting from the grid. To improve the continuous operation capability of offshore wind farms and avoid frequent disconnections of offshore wind turbines, it is usually necessary for the wind turbines to remain connected to the grid during transient short-circuit faults in the onshore AC system. How to improve the fault ride-through capability under onshore AC system fault conditions has become a hot research issue in the field of offshore wind farm MMC-HVDC grid connection.

[0004] At present, DC power dissipation devices are an important technical means to solve the above problems. Existing DC power dissipation devices mainly employ a linear switching control method, which adjusts the number of power modules in operation linearly according to the DC voltage. However, the conventional linear switching method has many shortcomings, such as poor reliability of the DC power dissipation devices. Summary of the Invention

[0005] This application provides a valve control method for a DC power consumption device, which can improve the reliability of the valve control action of the DC power consumption device.

[0006] In a first aspect, embodiments of this application provide a valve control method for a DC power-consuming device, the DC power-consuming device including at least one power-consuming valve and at least one power-consuming resistor, the at least one power-consuming valve and at least one power-consuming resistor being connected in series between positive and negative lines; the valve control method for the DC power-consuming device includes: Acquire the initial DC voltage signal between the positive and negative poles, and obtain the corresponding target DC voltage signal based on the initial DC voltage signal; Compare the target DC voltage signal with the activation voltage threshold of the DC energy-consuming device. If the target DC voltage signal is higher than the activation voltage threshold, control at least one energy-consuming valve to open. The target DC voltage signal is compared with the cut-off action voltage threshold of the DC energy-consuming device. If the target DC voltage signal is lower than the cut-off action voltage threshold, at least one energy-consuming valve is controlled to shut off.

[0007] In some possible implementations, the valve control method for the DC power consumption device further includes, before comparing the target DC voltage signal with the activation voltage threshold of the DC power consumption device and before comparing the target DC voltage signal with the deactivation voltage threshold of the DC power consumption device: Compare the target DC voltage signal with the unlocking voltage threshold of the DC power consumption device. If the target DC voltage signal is higher than the unlocking voltage threshold, control the DC power consumption device to unlock. Compare the target DC voltage signal with the operating voltage threshold of the DC power-consuming device, including: When the DC power consumption device is unlocked, compare the target DC voltage signal with the threshold voltage for activation. Compare the target DC voltage signal with the cut-off voltage threshold of the DC power consumption device, including: When the DC power consumption device is unlocked, compare the target DC voltage signal with the cut-off action voltage threshold.

[0008] In some possible implementations, the valve control method for the DC power consumption device further includes, after the control device is unlocked: Record the duration of a single unlocking of the DC power-consuming device; If the duration of a single unlock reaches the longest continuous energy consumption time for a single unlock, the DC energy consumption device will be locked. If the duration of a single unlock does not reach the longest continuous energy consumption time for a single unlock, and if at least one energy consumption valve is detected to be in a closed state, and the continuous closed duration of at least one energy consumption valve is greater than the lockout time threshold, the DC energy consumption device is controlled to lock out.

[0009] In some possible implementations, the valve control method for the DC power consumption device further includes, after comparing the target DC voltage signal with the unlocking voltage threshold of the DC power consumption device: When the target DC voltage signal is lower than or equal to the unlocking voltage threshold, the DC power consumption device is kept in a locked state.

[0010] In some possible implementations, the unlocking voltage threshold is greater than or equal to the activation voltage threshold, and the activation voltage threshold is greater than the deactivation voltage threshold.

[0011] In some possible implementations, at least one energy-consuming valve includes N power submodules, where N is a positive integer greater than 1; controlling at least one energy-consuming valve to open or close includes: The N power submodules are divided into multiple groups, and the multiple groups include at least the first group and the second group; In the first stage of the switching action triggering process of the energy-consuming valve opening or closing, the power submodule in the first group is put into or cut off at each first set time interval until the switching action of the first group is completed. In the second stage of the switching action triggering process, a power submodule in the second group is put into operation or cut off at a second set time interval, and a power submodule in the first group is cut off or put into operation at a second set time interval, so as to restore the state of the first group before the start of the first stage. In the third stage of the switching action triggering process, the power submodule in the first group is put into or cut off at a first set time interval until the switching action of the first group is completed.

[0012] In some possible implementations, the speed of the switch action in the first stage is a first speed, and the speed of the switch action in the second stage is a second speed, which is greater than the first speed.

[0013] In some possible implementations, the second speed is twice the first speed; The first set time is TSW / (N-1), and the second set time is TSW / 2(N-1), where TSW is the preset switching action time and N is the number of power sub-modules included in at least one energy-consuming valve.

[0014] In some possible implementations, the N power submodules are divided into multiple groups, including: Collect the capacitor voltage of the DC capacitors in N power submodules; The N power submodules are divided into multiple groups according to the order of capacitor voltage from high to low when they are engaged and from low to high when they are disengaged.

[0015] In some possible implementations, the power submodule includes a DC capacitor; During the switching action of opening or closing the energy dissipation valve, the switching action of the power submodule is triggered in the order of the capacitor voltage of the DC capacitor from high to low when the action is turned on, and from low to high when the action is turned off.

[0016] In some possible implementations, at least one energy-consuming valve includes a first energy-consuming valve and a second energy-consuming valve, and at least one energy-consuming resistor includes a first energy-consuming resistor and a second energy-consuming resistor. The first energy-consuming valve and the second energy-consuming valve each include at least one power sub-module. The first energy-consuming valve and the first energy-consuming resistor are connected in series between the positive line and the midpoint, and the second energy-consuming valve and the second energy-consuming resistor are connected in series between the negative line and the midpoint.

[0017] In some possible implementations, the power submodule includes: a main switching device, a first diode, a DC capacitor, a first resistor, a second diode, and a second resistor; The first terminal of the main switching device is electrically connected to the first terminal of the power submodule, and the second terminal of the main switching device is electrically connected to the second terminal of the power submodule. The anode of the first diode is electrically connected to the second terminal of the power submodule, and the cathode of the first diode is electrically connected to the first terminal of the power submodule. The first resistor is connected in parallel with the first diode. The second resistor and the DC capacitor are connected in series and then in parallel with the first resistor. The second diode is connected in parallel with the second resistor.

[0018] Based on the same inventive concept, in a second aspect, embodiments of this application provide a valve control device for a DC power consumption device. The DC power consumption device includes at least one power consumption valve and at least one power consumption resistor, wherein the at least one power consumption valve and at least one power consumption resistor are connected in series between the positive and negative terminals. The valve control device for the DC power consumption device includes: The first acquisition module is used to acquire the initial DC voltage signal between the positive and negative lines, and to obtain the corresponding target DC voltage signal based on the initial DC voltage signal; The first control module is used to compare the target DC voltage signal with the input action voltage threshold of the DC energy-consuming device, and control at least one energy-consuming valve to open when the target DC voltage signal is higher than the input action voltage threshold. The second control module is used to compare the target DC voltage signal with the cut-off action voltage threshold of the DC energy-consuming device, and control at least one energy-consuming valve to shut off when the target DC voltage signal is lower than the cut-off action voltage threshold.

[0019] Thirdly, embodiments of this application provide a valve control device for a DC power consumption device, the valve control device for the DC power consumption device comprising: Processor and memory storing computer program instructions; When the processor executes the computer program instructions, it implements the valve control method for the DC power consumption device provided in any of the embodiments of this application described above.

[0020] Fourthly, embodiments of this application provide a computer storage medium storing computer program instructions, which, when executed by a processor, implement the valve control method for a DC power consumption device as provided in any of the embodiments of this application described above.

[0021] Fifthly, embodiments of this application provide a computer program product in which instructions, when executed by a processor of an electronic device, cause the electronic device to perform a valve control method for a DC power consumption device as provided in any of the embodiments of this application described above.

[0022] This application provides a valve control method for a DC power-consuming device. The DC power-consuming device includes at least one power-consuming valve and at least one power-consuming resistor, which are connected in series between positive and negative lines. An initial DC voltage signal between the positive and negative lines is acquired, and a corresponding target DC voltage signal is obtained based on the initial DC voltage signal. Then, the target DC voltage signal is compared with an activation voltage threshold of the DC power-consuming device. If the target DC voltage signal is higher than the activation voltage threshold, at least one power-consuming valve is controlled to open. The target DC voltage signal is compared with a deactivation voltage threshold of the DC power-consuming device. If the target DC voltage signal is lower than the deactivation voltage threshold, at least one power-consuming valve is controlled to close.

[0023] As described above, the valve control method for a DC energy-consuming device according to an embodiment of this application employs a start-stop control strategy. The energy-consuming valve fully opens when the input threshold is reached and fully closes when the cut-off threshold is reached, rather than linearly adjusting the number of conducting modules. This start-stop control method significantly reduces the current change rate and achieves safe power dissipation without the need for a reactor, thus helping to reduce the device cost and size of the DC energy-consuming valve. Furthermore, by setting the aforementioned input and cut-off voltage thresholds, the DC voltage can be controlled within a certain range, reducing power fluctuations caused by linear regulation, reducing switching disturbances, and helping to maintain a low DC voltage ripple level, thereby improving the reliability of valve control operation. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic flowchart of a valve control method for a DC power consumption device provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a DC power consumption device provided in an embodiment of this application; Figure 3 This is a schematic diagram of the electrical topology for power submodule conduction according to an embodiment of this application; Figure 4 This is a schematic diagram of the electrical topology for power submodule shutdown provided in an embodiment of this application; Figure 5 This is a schematic diagram of the control architecture of the valve control method for a DC power consumption device provided in an embodiment of this application; Figure 6 This is a schematic diagram of the control block of a valve control method for a DC power consumption device provided in an embodiment of this application; Figure 7 This is a schematic flowchart of a valve control method for a DC power consumption device provided in another embodiment of this application; Figure 8 This is a simulation waveform diagram of the power submodule voltage of a conventional linear switching strategy provided in an embodiment of this application; Figure 9 This is a simulation waveform diagram of the power submodule voltage of the valve control method of the DC energy consumption device provided in an embodiment of this application; Figure 10 This is a simulation waveform diagram of the system DC voltage and power submodule voltage of the valve control method of the DC energy consumption device provided in an embodiment of this application; Figure 11 This is a simulation waveform diagram of the system DC voltage and power submodule voltage of the valve control method for a DC power consumption device provided in another embodiment of this application; Figure 12 This is a simulation waveform diagram of the system DC voltage and power submodule voltage of the valve control method of the DC energy consumption device provided in another embodiment of this application; Figure 13 This is a simulation waveform diagram of the system DC voltage and power submodule voltage of the valve control method of the DC energy consumption device provided in another embodiment of this application; Figure 14 This is a simulation waveform diagram of the system DC voltage and power submodule voltage of the valve control method of the DC energy consumption device provided in another embodiment of this application; Figure 15 This is a schematic diagram of the valve control device of a DC power consumption device provided in an embodiment of this application; Figure 16 This is a schematic diagram of the valve control device of a DC power consumption device provided in an embodiment of this application. Detailed Implementation

[0026] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0027] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0028] As described in the background section, currently, the valve control strategy for DC power consumption devices mainly adopts a linear switching control method, that is, adjusting the number of power modules in operation linearly according to the DC voltage. However, the conventional linear switching method has many shortcomings. Specifically, this control method has the following drawbacks: First, it requires a large reactor to limit the rate of current change, increasing the cost and size of the device; second, the voltage balance of the power modules is poor, with some modules bearing greater voltage stress, affecting the reliability of the device; and third, the DC voltage ripple is large, which is not conducive to the stable operation of the system.

[0029] In view of the above, in order to solve the problems of the prior art, this application provides a valve control method for a DC power consumption device. It should be noted that the embodiments provided in this application are not intended to limit the scope of this application.

[0030] The valve control method for the DC power consumption device provided in the embodiments of this application will be introduced first below.

[0031] Figure 1 A schematic flowchart of a valve control method for a DC power-consuming device according to an embodiment of this application is shown. This valve control method for a DC power-consuming device can be applied to a DC power-consuming control system. Figure 1 As shown, the valve control method for this DC power consumption device includes the following steps: S110, acquire the initial DC voltage signal between the positive and negative lines, and obtain the corresponding target DC voltage signal based on the initial DC voltage signal; S120: Compare the target DC voltage signal with the operating voltage threshold of the DC energy-consuming device. If the target DC voltage signal is higher than the operating voltage threshold, control at least one energy-consuming valve to open. S130: Compare the target DC voltage signal with the cut-off action voltage threshold of the DC energy-consuming device. If the target DC voltage signal is lower than the cut-off action voltage threshold, control at least one energy-consuming valve to shut off.

[0032] This application provides a valve control method for a DC power-consuming device. The DC power-consuming device includes at least one power-consuming valve and at least one power-consuming resistor, which are connected in series between positive and negative lines. An initial DC voltage signal between the positive and negative lines is acquired, and a corresponding target DC voltage signal is obtained based on the initial DC voltage signal. Then, the target DC voltage signal is compared with an activation voltage threshold of the DC power-consuming device. If the target DC voltage signal is higher than the activation voltage threshold, at least one power-consuming valve is controlled to open. The target DC voltage signal is compared with a deactivation voltage threshold of the DC power-consuming device. If the target DC voltage signal is lower than the deactivation voltage threshold, at least one power-consuming valve is controlled to close.

[0033] As described above, the valve control method for a DC energy-consuming device according to an embodiment of this application employs a start-stop control strategy. The energy-consuming valve fully opens when the input threshold is reached and fully closes when the cut-off threshold is reached, rather than linearly adjusting the number of conducting modules. This start-stop control method significantly reduces the current change rate and achieves safe power dissipation without the need for a reactor, thus helping to reduce the device cost and size of the DC energy-consuming valve. Furthermore, by setting the aforementioned input and cut-off voltage thresholds, the DC voltage can be controlled within a certain range, reducing power fluctuations caused by linear regulation, reducing switching disturbances, and helping to maintain a low DC voltage ripple level, thereby improving the reliability of valve control operation.

[0034] The specific implementation methods of steps 110 to 130 above are described in detail below.

[0035] To facilitate understanding of the valve control method for the DC energy-consuming device provided in this application, the DC energy-consuming device in the embodiments of this application will be briefly introduced below. Figure 2 This is a schematic diagram of the structure of a DC power consumption device 100 provided in an embodiment of this application. Figure 3 This is a schematic diagram of the electrical topology for power submodule conduction according to an embodiment of this application; Figure 4 This is a schematic diagram of the electrical topology for power submodule shutdown provided in an embodiment of this application.

[0036] like Figure 2 As shown, the DC power consumption device 100 includes at least one power consumption valve and at least one power consumption resistor, which are connected in series between the positive and negative poles.

[0037] Optionally, according to some embodiments of this application, at least one energy-consuming valve includes a first energy-consuming valve 101 and a second energy-consuming valve 102, and at least one energy-consuming resistor includes a first energy-consuming resistor Rm1 and a second energy-consuming resistor Rm2; the first energy-consuming valve 101 and the second energy-consuming valve 102 each include at least one power submodule 10, the first energy-consuming valve 101 and the first energy-consuming resistor Rm1 are connected in series between the positive line and the midpoint, and the second energy-consuming valve 102 and the second energy-consuming resistor Rm2 are connected in series between the negative line and the midpoint.

[0038] like Figure 2 As shown, the DC power dissipation device 100 mainly consists of a power dissipation valve and a power dissipation resistor. The first power dissipation valve 101 and the second power dissipation valve 102 are respectively connected to the positive and negative lines. The first power dissipation resistor Rm1 and the second power dissipation resistor Rm2 can be centrally arranged outdoors, and the first power dissipation resistor Rm1 and the second power dissipation resistor Rm2 are connected in series with the first power dissipation valve 101 and the second power dissipation valve 102.

[0039] It should be added that, in practical applications, the first energy-consuming valve 101 and the second energy-consuming valve 102 can be arranged symmetrically. This symmetrical arrangement can keep the potentials at both ends equal and maintain the midpoint at zero voltage, which is beneficial to the voltage balance and stable operation of the DC system.

[0040] Optionally, according to some embodiments of this application, such as Figure 3 and Figure 4 As shown, the power submodule 10 includes: a main switching device Km, a first diode Dr, a DC capacitor Ca, a first resistor Rd, a second diode Df, and a second resistor Ra; The first terminal of the main switching device Km is electrically connected to the first terminal of the power submodule 10, and the second terminal of the main switching device Km is electrically connected to the second terminal of the power submodule 10. The anode of the first diode Dr is electrically connected to the second terminal of the power submodule 10, and the cathode of the first diode Dr is electrically connected to the first terminal of the power submodule 10. The first resistor Rd is connected in parallel with the first diode Dr. The second resistor Ra and the DC capacitor Ca are connected in series and then connected in parallel with the first resistor Rd. The second diode Df is connected in parallel with the second resistor Ra.

[0041] In this embodiment, the first energy dissipation valve 101 and the second energy dissipation valve 102 may include multiple power sub-modules 10. The multiple power sub-modules 10 are connected in series. The first terminal of the main switching device Km is electrically connected to the first terminal of the power sub-module 10, and the second terminal of the main switching device Km is electrically connected to the second terminal of the power sub-module 10. The power sub-module 10 is switched on and off by controlling the switching on and off of the main switching device Km. The main switching device Km may be, for example, an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or an integrated gate-commutated thyristor (IGCT). This embodiment does not strictly limit the specific type of device.

[0042] The first diode Dr, as an anti-parallel diode of the main switching device Km, is used to provide a freewheeling path in the off state. The first resistor Rd is connected in parallel with the first diode Dr, serving as a static voltage equalizing resistor to release energy; the second resistor Ra and the DC capacitor Ca are connected in series and then in parallel with the first resistor Rd, with the second resistor Ra serving as a current-limiting resistor to limit the charging and discharging current of the capacitor; the second diode Df is connected in parallel with the second resistor Ra, serving as a fast recovery diode to provide a fast charging path for the capacitor during the switching process.

[0043] In specific operation, when the main switching device Km is turned on, the power submodule 10 is put into operation, and the DC capacitor Ca is slowly discharged through the second resistor Ra; when the main switching device Km is turned off, the power submodule 10 is switched off, and the DC capacitor Ca is quickly charged to near the rated voltage through the first resistor Rd and the second diode Df, in preparation for the next operation.

[0044] Optionally, in this application, the first energy-consuming valve 101 and the second energy-consuming valve 102 adopt a symmetrical control strategy, and regardless of the value of the power command value duty (duty cycle, i.e., the ratio of the number of power modules put into operation in the energy-consuming valve to the total number of modules), the number of power sub-modules 10 put into each energy-consuming valve is the same.

[0045] Optionally, the DC power consumption device 100 has a hot standby state and a power consumption operation state. In the hot standby state, the main switching device Km in all power submodules 10 is disconnected, and the DC pole voltage is uniformly distributed across each power submodule 10. Therefore, the voltage U of each power submodule 10 is... IGCT =U dc / N T (U) dc N is the DC pole line voltage. T(This refers to the total number of power sub-modules 10 connected in series in a single power-consuming valve), at which point the DC power-consuming device 100 consumes no power. This uniform distribution characteristic ensures balanced voltage stress in each power sub-module 10, improving the overall reliability of the DC power-consuming device 100.

[0046] When the main switching devices Km of all power submodules 10 are closed, the DC line voltage is directly applied across the energy-consuming resistor. Optionally, the power absorbed by the energy-consuming resistor is not less than the rated transmission power of the DC system to fully guarantee the power consumption capacity of the energy-consuming resistor. In this case, the DC energy-consuming device 100 is in full operation to consume the surplus power of the DC system to the maximum extent.

[0047] In this embodiment, the transmission power on the DC system is between 0 and P. N The range fluctuates between 0 and P. When a fault occurs on the power grid side of the onshore station, its surplus power also ranges from 0 to P. N Therefore, in the event of a fault, when the DC power dissipation device 100 is in the off state, the DC voltage of the DC system will rise; while when the DC power dissipation device 100 is in the on state, since the power absorbed by the power dissipation resistor is not less than P... N The system DC voltage will drop. This embodiment achieves the control of the system DC voltage within a certain range by setting the DC power consumption device 100 to be activated when the system DC voltage is higher than a certain value and deactivated when it is lower than a certain value.

[0048] The following is combined Figure 2 The DC power dissipation device 100 shown below will be described in detail below in terms of the specific implementation of steps 110-130. It should be noted that in some other embodiments, the DC power dissipation device in this application may also be implemented using other topologies, which are not strictly limited here.

[0049] In S110, in specific implementation, the initial DC voltage signal can be the real-time DC voltage measurement value between the positive and negative lines. Since voltage measurement noise and instantaneous fluctuations may exist in the DC system, directly using the real-time measurement value for control judgment can easily lead to malfunctions. Therefore, the initial DC voltage signal can be processed to obtain the target DC voltage signal. Alternatively, the initial DC voltage signal can be directly used as the target DC voltage signal to quickly proceed to subsequent processing steps and accelerate the overall valve control process.

[0050] Optionally, in some examples, obtaining the corresponding target DC voltage signal based on the initial DC voltage signal can be achieved by filtering the initial DC voltage signal. The filtering process can employ a low-pass filter, a moving average filter, or other appropriate digital filtering algorithms to remove high-frequency noise and transient disturbances, obtaining a smooth and stable DC voltage signal as the basis for control decisions. Through filtering, frequent malfunctions of the energy-consuming valve caused by transient voltage fluctuations can be effectively avoided, improving the reliability and stability of the control. Furthermore, the target DC voltage signal can also be obtained by standardizing the voltage signal.

[0051] In S120, in a specific implementation, optionally, the activation voltage threshold is a preset upper voltage threshold, used to determine whether the DC system has a power surplus leading to excessively high DC voltage. When a fault or power imbalance occurs in the receiving-end AC grid, the MMC submodule capacitor is charged, the DC voltage rises, causing the target DC voltage signal to rise.

[0052] In this way, when the target DC voltage signal is higher than the input action voltage threshold, it indicates that the system's surplus power has reached the level that requires the energy-consuming device to be activated. At this time, an opening command is issued through the energy-consuming valve to control the main switching devices of all power submodules 10 to close, and the energy-consuming resistor is connected to the DC system to start consuming the surplus power, causing the DC voltage to drop.

[0053] When selecting the actual activation voltage threshold, it can be higher than the highest DC voltage during normal operation of the DC system to avoid accidental activation during normal operation. Furthermore, the activation voltage threshold can also be lower than the overvoltage protection setting of the DC system to ensure timely activation of energy-consuming devices before protection operation.

[0054] In S130, in specific implementation, the cut-off action voltage threshold is a preset lower voltage threshold, used to determine whether the surplus power of the DC system has been fully consumed and whether the DC voltage has returned to a safe range. When the DC energy-consuming device is put into operation, the energy-consuming resistor continuously consumes power, and the DC voltage continuously decreases, causing the acquired target DC voltage signal to decrease.

[0055] In this way, when the target DC voltage signal is lower than the above-mentioned cut-off action voltage threshold, it indicates that the DC system power has been restored to balance or the surplus power has been eliminated. At this time, by issuing a shut-off command to the energy dissipation valve, the main switching devices of all power modules are controlled to disconnect, and the energy dissipation resistor is cut off from the DC system, thereby stopping power consumption.

[0056] When selecting the actual cut-off voltage threshold, it can be set to be lower than the activation voltage threshold, thus creating a voltage hysteresis control characteristic. This avoids the frequent activation and deactivation problems caused by a single threshold near the cut-off voltage threshold, improving the reliability of valve control action.

[0057] Therefore, by adopting a start-stop control strategy, the energy-consuming valve is fully opened when the input threshold is reached and fully closed when the cut-off threshold is reached, rather than linearly adjusting the number of conducting modules. This start-stop control method significantly reduces the current change rate and achieves safe power dissipation without the need for a reactor, helping to reduce the device cost and size of the DC energy-consuming valve. Furthermore, by setting the aforementioned input and cut-off operating voltage thresholds, the DC voltage can be controlled within a certain range in this embodiment, reducing power fluctuations caused by linear regulation, reducing switching disturbances, helping to maintain a low DC voltage ripple level, and improving the reliability of valve control operation.

[0058] Optionally, according to some embodiments of this application, before comparing the target DC voltage signal with the activation voltage threshold of the DC power-consuming device and before comparing the target DC voltage signal with the deactivation voltage threshold of the DC power-consuming device, the valve control method for the DC power-consuming device further includes: Compare the target DC voltage signal with the unlocking voltage threshold of the DC power consumption device. If the target DC voltage signal is higher than the unlocking voltage threshold, control the DC power consumption device to unlock. Compare the target DC voltage signal with the operating voltage threshold of the DC power-consuming device, including: When the DC power consumption device is unlocked, compare the target DC voltage signal with the threshold voltage for activation. Compare the target DC voltage signal with the cut-off voltage threshold of the DC power consumption device, including: When the DC power consumption device is unlocked, compare the target DC voltage signal with the cut-off action voltage threshold.

[0059] In this embodiment, when the target DC voltage signal exceeds the unlocking voltage threshold, an unlocking command is sent to the power module controller of the energy-consuming valve to release the pulse blocking state. A start-stop control is employed when the DC energy-consuming device is unlocked to improve system safety and reliability. Simultaneously, the unlocking threshold is used for fault confirmation to prevent accidental activation.

[0060] Thus, once it is confirmed that the DC power dissipation device is unlocked, the DC voltage monitoring program is initiated, and the target DC voltage signal is compared with the activation / deactivation voltage threshold in real time. When the DC voltage is higher than the activation voltage threshold, the power dissipation valve is opened, activating the power dissipation resistor, causing the system DC voltage to drop; when the DC voltage is lower than the deactivation voltage threshold, the power dissipation valve is closed, deactivating the power dissipation resistor, causing the system DC voltage to rise.

[0061] In one instance, combined Figure 5 As shown, when a fault occurs in the receiving-end AC system, the power output of the offshore wind farm and the power output capacity of the receiving-end AC system are mismatched, and the DC line voltage will rise due to the power surplus. When the target DC voltage signal obtained from the DC voltage measurement based on the DC line voltage exceeds the unlocking voltage threshold set by the DC energy dissipation device, the DC energy dissipation device, according to the unlocking command sent by the DC control and protection system or the energy dissipation device valve control system, collects electrical quantities such as system voltage and current to determine and implement the energy dissipation device switching strategy. In the unlocked state, the energy dissipation valve adopts start-stop control during operation. When the system DC voltage drops to the cut-off action voltage threshold, the entire energy dissipation valve begins to cut off the energy dissipation resistor; when the system DC voltage rises to the activation action voltage threshold, the entire energy dissipation valve begins to activate the energy dissipation resistor.

[0062] After triggering the activation / deactivation of the energy-consuming valve, a trigger pulse is sent to the control signal generator of the energy-consuming valve power submodule 10. Once triggered, the control signal generator of the energy-consuming valve power submodule 10 sequentially triggers the logic generation submodule control signals of all submodules according to a specific strategy. For example, it sorts the collected capacitor voltages of the power submodules 10 in each energy-consuming valve and activates or deactivates them in sequence. The specific decision-making process and signal triggering strategy will be described in detail later.

[0063] Optionally, according to some embodiments of this application, after the DC power-consuming device is unlocked, the valve control method for the DC power-consuming device further includes: Record the duration of a single unlocking of the DC power-consuming device; If the duration of a single unlock reaches the longest continuous energy consumption time for a single unlock, the DC energy consumption device will be locked. If the duration of a single unlock does not reach the longest continuous energy consumption time for a single unlock, and if at least one energy consumption valve is detected to be in a closed state, and the continuous closed duration of at least one energy consumption valve is greater than the lockout time threshold, the DC energy consumption device is controlled to lock out.

[0064] In this embodiment, after the DC power consumption device is unlocked, the duration of a single unlocking of the DC power consumption device is also recorded. This duration is counted from the moment the device is unlocked and is used to record the length of time the DC power consumption device is continuously in the unlocked state.

[0065] If the duration of a single unlock reaches the maximum continuous power consumption time for a single unlock, the DC power consumption device will be locked. The maximum continuous power consumption time for a single unlock is a preset maximum allowable unlock duration. The setting of this parameter can take into account the safety protection of the components in the DC power consumption device, and is not strictly limited here.

[0066] When the duration of a single unlock reaches the maximum continuous energy consumption time for that single unlock, the DC energy dissipation device is locked, forcibly shutting down the main switching devices of all power modules, ceasing the comparison between DC voltage and the switching threshold, and exiting the start-stop control logic. If the duration of a single unlock does not reach the maximum continuous energy consumption time for a single unlock, and at least one energy dissipation valve is detected to be in a closed state, and the continuous closed duration of at least one energy dissipation valve exceeds the lockout time threshold, the DC energy dissipation device is locked. This allows for timely locking of the DC energy dissipation device after the fault is cleared, reducing unnecessary losses.

[0067] Therefore, by comparing the aforementioned pre-set interlocking time with the longest continuous energy consumption time for a single unlocking, it helps to prevent the energy-consuming resistor from overheating and being damaged due to prolonged high-power operation, limits the voltage and current stress of the main switching device of the power module, and ensures that the device can be controlled to exit after the fault is cleared.

[0068] Optionally, according to some embodiments of this application, after comparing the target DC voltage signal with the unlocking voltage threshold of the DC power-consuming device, the valve control method for the DC power-consuming device further includes: When the target DC voltage signal is lower than or equal to the unlocking voltage threshold, the DC power consumption device is kept in a locked state.

[0069] Specifically, when the target DC voltage signal is lower than or equal to the unlocking voltage threshold, it indicates that the system is in normal operating condition, without a serious power surplus fault, or the fault is minor and does not require the activation of the DC power-consuming device. In this case, the DC power-consuming device is kept in a locked state to reduce its losses. Thus, by using the aforementioned unlocking voltage threshold, voltage fluctuations and minor disturbances during normal operation can be filtered out, allowing for a response only to serious faults requiring intervention.

[0070] Optionally, according to some embodiments of this application, the unlocking voltage threshold is greater than or equal to the input action voltage threshold, and the input action voltage threshold is greater than the cut-off action voltage threshold.

[0071] In this way, during normal operation of the DC system or minor voltage fluctuations, even if the voltage momentarily exceeds the activation voltage threshold, the DC power dissipation device can remain locked if it does not reach the unlocking voltage threshold, thus avoiding unnecessary activation and preventing malfunctions. Only when the DC voltage continuously rises above the unlocking threshold is a serious power surplus fault confirmed in the system, allowing the DC power dissipation device to enter the unlocked state, thereby improving the safety and reliability of the system.

[0072] To facilitate understanding of the practical application of the above embodiments of this application, please refer to the following: Figure 6 Combining Figure 6 As shown, the DC control and protection system (or the control and protection system for DC energy-consuming devices) determines whether to enable the DC energy-consuming device based on information such as the system operating mode and the status of the DC energy-consuming device, and simultaneously issues enable or disable commands to the DC energy-consuming device. During the enabling period, the DC energy-consuming device filters and standardizes the initial DC voltage signal to obtain the target DC voltage signal. Using the target DC voltage signal as the basis for judgment, when the DC voltage is greater than the unlocking threshold, the DC energy-consuming device is unlocked; when the energy-consuming valve is in the off state for a continuous period of time or the operation time exceeds the upper limit, the DC energy-consuming device is locked. During the unlocking period of the DC energy-consuming device, a start-stop control is adopted. The relationship between the real-time target DC voltage signal and the activation / deactivation action voltage threshold determines whether to execute the activation / deactivation action: when the system's target DC voltage signal is higher than the activation action threshold, the energy-consuming valve begins to activate the energy-consuming resistor; when the system's DC voltage is lower than the deactivation action threshold, the energy-consuming valve begins to deactivate the energy-consuming resistor. By reasonably selecting the activation / deactivation action voltage threshold, the actual value of the DC voltage can always be kept within an appropriate range, thereby realizing the energy consumption function.

[0073] The control block diagram of the DC power consumption device is as follows: Figure 6 As shown, the initial DC voltage signal is U, and the target DC voltage signal is... U PU The threshold voltage for DC power consumption device activation / deactivation is: U On / U Off The unlocking voltage threshold is U Eab The latching time threshold is T DEab The longest continuous energy consumption time for a single unlock is... T max .

[0074] The principles of each control element are explained below.

[0075] (I) Signal Acquisition and Processing This control strategy uses DC pole line voltage as the input signal for control. The acquired initial DC voltage U is filtered to eliminate the influence of the converter operating frequency and the operating frequency of the energy-consuming device on the voltage control, thus obtaining the target DC voltage signal for subsequent control systems. U PU .

[0076] (ii) Unlock / Lock Control Set the voltage threshold for the DC power consumption device to be switched on / off. U On / U Off The unlocking voltage threshold is U Eab The latching time threshold is T DEab The longest continuous energy consumption time for a single unlock is... T max .

[0077] When there is no fault in the AC power grid at the receiving end, the system operates normally, and the target DC voltage signal... U PU < U Eab The DC energy dissipation device remains in a locked state. At this time, the energy dissipation valve can withstand DC voltage, and the loss caused by static leakage current is extremely low.

[0078] After a fault occurs in the AC power grid at the receiving end, the DC voltage gradually increases until the target DC voltage signal is detected. U PU > U Eab The DC power dissipation device is unlocked, and the comparison and detection between the target DC voltage signal and the activation / deactivation action voltage threshold is activated. Simultaneously, the power dissipation device valve-controlled start timing is initiated, recording the cumulative unlocking time T, and the opening time of the power dissipation valve is recorded according to its current state. T On Or shutdown duration T Off After the DC power dissipation device is unlocked, the DC voltage decreases under the action of the DC power dissipation device and continuously switches between the power dissipation valve open (SW=1) state and the power dissipation valve closed (SW=0) state, while the DC power dissipation device remains unlocked.

[0079] Longest continuous energy consumption time for a single unlock T max If the AC grid fault at the receiving end disappears, the target DC voltage signal will gradually recover to its pre-fault value under the control of the receiving-end converter. During the recovery process, when the energy dissipation valve is detected to be in the off state and T Off >T DEab The DC power consumption device is locked, and the controller stops comparing the target DC voltage signal with the activation / deactivation voltage threshold. The system returns to its state before the fault occurred.

[0080] If the duration of the AC power grid fault at the receiving end exceeds the longest continuous energy consumption time for a single unlocking operation. T max The DC energy-consuming device is forcibly locked, and the controller stops sending switching pulse signals to the energy-consuming valve. At this time, the DC system voltage is transferred to other energy-consuming measures, voltage control measures, or wind farm orderly withdrawal measures for control.

[0081] (III) DC voltage control Once the unlocking condition of the DC energy-consuming device is met, the device is unlocked, and the comparison detection between the DC voltage and the activation / deactivation voltage threshold is activated. This control strategy employs start-stop control, the basic principle of which is to determine whether to execute an activation / deactivation action based on the relationship between the real-time DC voltage value and the activation / deactivation voltage threshold: When the system's target DC voltage signal is higher than the activation voltage threshold, the energy-consuming valve begins to open, activating the energy-consuming resistor (SW=1). Since the power consumed by the energy-consuming resistor is greater than the system's surplus power, the system's target DC voltage signal will gradually decrease. When the system's target DC voltage signal is lower than the deactivation voltage threshold, the energy-consuming valve begins to close, deactivating the energy-consuming resistor (SW=0). At this time, under the influence of surplus power, the system DC voltage will gradually rise again. By reasonably selecting the activation / deactivation voltage threshold, the DC energy-consuming device can control the system DC voltage fluctuation within the target range during operation.

[0082] In addition, for the purposes of protecting submodule devices, maintaining the operation of the power supply, and responding to upper-level valve control commands, the control system also includes detection conditions such as minimum turn-on time, minimum turn-off time, and minimum conduction voltage, as well as mandatory execution functions. Specifically, the minimum turn-off time refers to the shortest shutdown duration that the energy-consuming valve must maintain after switching from the active state to the deactivated state. When the main switching device of the power submodule 10 is turned off, the electrical energy stored in the DC capacitor of the power submodule 10 needs to be released and cleared through parallel resistors and other circuits. If the turn-off time is too short before restarting, the residual charge in the capacitor will be superimposed on the recharging process, resulting in a violent current surge at the moment of turn-on, which may damage devices such as anti-parallel diodes. Therefore, the minimum turn-off time ensures that the submodule's electrical energy is fully released, meeting the safe operation requirements of the switching devices in the power submodule 10.

[0083] The minimum turn-on voltage refers to the minimum submodule capacitor voltage threshold that allows the main switching device to conduct. The control circuit of power submodule 10 typically uses a self-powered power supply, drawing power from the submodule's DC capacitor to supply power to the driver board and controller. If the capacitor voltage is lower than this threshold, the control circuit cannot obtain sufficient energy, leading to abnormal drive signals or insufficient conduction of the switching device, potentially causing device damage or module failure. Therefore, before executing the activation action, the controller needs to check whether the submodule voltage is higher than the minimum turn-on voltage, and only allow the activation command to take effect when the condition is met, ensuring stable operation of the power supply.

[0084] Minimum turn-on time refers to the shortest conduction duration that a power dissipation valve must maintain after switching from the off state to the on state. The minimum turn-on time can be set to be longer than the dead time of the main switching device. This parameter is based on the inherent dead-time characteristics of the main switching device: after power devices are turned on, they need a certain amount of time to complete physical processes such as carrier establishment and junction capacitance charging and discharging. If turn-off is performed immediately, the device has not yet entered a stable conduction state, resulting in a sharp increase in turn-off losses and the potential for abnormal voltage and current stress. The minimum turn-on time ensures that the switching device transcends the dead time and enters the safe conduction region.

[0085] Please refer to the following: Figure 7 Optionally, according to some embodiments of this application, such as Figure 7 As shown, at least one energy-consuming valve includes N power submodules 10, where N is a positive integer greater than 1; controlling at least one energy-consuming valve to open or close includes the following steps: S710 divides N power submodules into multiple groups, and the multiple groups include at least the first group and the second group; S720, in the first stage of the switching action triggering process of the energy dissipation valve opening or closing, performs an input or cut-off action on a power submodule in the first group at first set time intervals until the switching action of the first group is completed. S730, in the second stage of the switching action triggering process, a power submodule in the second group is put into or cut off at a second set time interval, and a power submodule in the first group is cut off or put into operation at a second set time interval, so as to restore the state of the first group before the start of the first stage. S740, in the third stage of the switching action triggering process, performs an on or off action on a power submodule in the first group at first set time intervals until the switching action of the first group is completed.

[0086] In specific implementation, the ratio of the number of submodules in the first group to the second group is adjustable. For example, the ratio of the first group to the second group is 1:2, meaning the first group contains N / 3 power submodules 10 and the second group contains 2N / 3 power submodules 10. Alternatively, the ratio of the first group to the second group can be 1:3, 2:1, etc., and is not limited here. In the first stage of the switching action triggering process of the energy dissipation valve opening or closing, one power submodule 10 in the first group is activated or deactivated at first set time intervals until the switching action of the first group is completed. Furthermore, in order to achieve stable changes in DC voltage, during the activation process, each submodule in the first group is activated sequentially according to the submodule voltage from high to low; during the deactivation process, each submodule in the first group is deactivated sequentially according to the submodule voltage from low to high.

[0087] In the second stage of the switching action triggering process, at second set time intervals, one power submodule 10 in the second group is switched on or off, and at second set time intervals, one power submodule 10 in the first group is switched off or switched on, to restore the state of the first group before the start of the first stage. Through this symmetrical "one forward, one backward" operation, the number of submodules that are turned on by the energy dissipation valve as a whole remains stable, and the DC pole voltage is evenly distributed on the turned-on submodules, achieving external characteristics consistent with conventional linear switching strategies, while keeping voltage fluctuations to a minimum.

[0088] In the third stage of the switching action triggering process, at first set time intervals, one power submodule 10 in the first group is put on or taken off until the switching action of the first group is completed. This stage is similar to the first stage but the action direction is reversed. The first group completes the remaining state switching according to the voltage sequence, and finally makes the entire energy dissipation valve reach the target on or off state. This helps to balance the voltage stress of each power submodule 10 and extend the service life of the power submodule 10.

[0089] In this embodiment, when the three-stage triggering strategy is executed, the DC voltage external characteristics of the energy-consuming valve remain consistent with the conventional linear switching strategy, achieving minimal switching disturbance of the DC energy-consuming device, while improving the voltage equalization characteristics of the energy-consuming valve submodule.

[0090] Optionally, according to some embodiments of this application, the speed of the switch action in the first stage is a first speed, and the speed of the switch action in the second stage is a second speed, the second speed being greater than the first speed.

[0091] Therefore, by adjusting the speed difference of the sub-module actions to control the switching rate of different stages, it helps to ensure a smooth voltage transition while optimizing the overall action time.

[0092] Optionally, according to some embodiments of this application, the second speed is twice the first speed; the first set time is TSW / (N-1), the second set time is TSW / 2(N-1), TSW is the preset switching action time, and N is the number of power sub-modules 10 included in at least one energy-consuming valve.

[0093] Furthermore, optionally, the ratio of the number of the first group to the number of the second group is 1:2, that is, the first group contains N / 3 sub-modules and the second group contains 2N / 3 sub-modules. The purpose of this ratio setting is to achieve a dynamic balance in the total number of conducting modules of the energy-consuming valve during the activation or deactivation process through the coordinated action of the two groups of sub-modules, thereby maintaining a stable change in DC voltage.

[0094] In this way, in the second stage, due to the adoption of an alternating control strategy, the actions of two sub-modules are completed within each set time interval (one for the second group and one for the first group). Therefore, the 2N / 3 sub-modules of the second group and the N / 3 sub-modules of the first group can be rolled back in the same time, achieving a dynamic balance in the total number of energy-consuming valves in operation or deactivation.

[0095] Optionally, according to some embodiments of this application, the N power submodules 10 are divided into multiple groups, including: Collect the capacitor voltage of the DC capacitors in N power submodules 10; The N power submodules 10 are divided into multiple groups according to the order of capacitor voltage from high to low when they are engaged and from low to high when they are disengaged.

[0096] In this embodiment, the capacitor voltages of the DC capacitors in the N power submodules 10 are collected to monitor the energy state of each submodule in real time. The N power submodules 10 are divided into multiple groups according to the order of capacitor voltage from high to low during activation and from low to high during deactivation. This allows for priority selection of submodules with higher voltages during activation, enabling them to discharge through energy-consuming resistors to lower their voltage; and priority selection of submodules with lower voltages during deactivation, thereby reducing voltage differences between submodules and achieving dynamic voltage equalization.

[0097] Optionally, according to some embodiments of this application, the power submodule 10 includes a DC capacitor; During the switching action triggering process of the energy dissipation valve opening or closing, the switching action of the power submodule 10 is triggered in the order of the capacitor voltage of the DC capacitor from high to low when the action is turned on, and from low to high when the action is turned off.

[0098] Specifically, during the activation action, the controller sorts the N sub-modules according to their current capacitor voltage from highest to lowest, with the sub-module with the highest voltage being activated first, and so on down. During the deactivation action, the controller sorts the N sub-modules according to their current capacitor voltage from lowest to highest, with the sub-module with the lowest voltage being deactivated first, and so on up. This mechanism effectively improves voltage equalization performance and reduces disturbances.

[0099] In a complete embodiment, exemplarily, when the DC power consumption device control system switches from SW=0 to SW=1 or vice versa, it sends a trigger pulse to the control signal generator of the power submodule 10. The generator samples and sorts the capacitor voltages of the DC capacitors in all power consumption valve submodules, dividing the submodules into two groups according to the order of voltage from high to low when the action is activated and from low to high when the action is deactivated. The ratio of the number of submodules in each group is adjustable. Here, an example scheme is given with a ratio of 1:2 between the group with a generally higher voltage when the action is activated and a group with a generally lower voltage when the action is deactivated, and the remaining modules forming the other group; the former is referred to as group 1 and the latter as group 2.

[0100] According to the switching action time T set by the controller SW And the number N of energy-consuming valve submodules, arranged in order of voltage from high to low when activated and from low to high when deactivated, at each time interval. T SW / (N-1) Perform an enable / disable action on the first-level submodule. Therefore, during the enable process, the voltage between the energy-consuming valve terminals will be reduced from... U DC The voltage drops in a stepwise manner to 0; conversely, during the resection process, the voltage between the energy-consuming valve terminals rises in a stepwise manner from 0 to... U DC Because there are enough sub-modules, and considering the buffering effect of the sub-module capacitors and the filtering effect of the current-limiting reactors, the unloading power of the DC power dissipation device can change smoothly, thereby suppressing the fluctuation of the system DC voltage.

[0101] Based on this, this embodiment proposes to divide the generated energy-consuming switch action submodule triggering process (the switching action triggering process of energy-consuming valve opening or closing) into three stages. The first stage is the normal switch group 1 (i.e., every interval time). T SW / (N-1) Perform the engagement / disengagement action on the first-level sub-modules in group 1); after all sub-modules in group 1 have completed the engagement / disengagement action, the second stage switches group 2 at twice the speed (i.e., every interval). T SW / 2(N-1) performs the input / output action on the first-level sub-modules in the second group), while simultaneously reversing the first group one by one (i.e., at each interval). T SW / 2(N-1) Perform cut-off / input actions on the first-level sub-modules in the first group, restoring them to their state before the start of the first phase); in the third phase, repeat the actions of the first phase, switching the first group on and off one by one.

[0102] Please see Figure 8 or Figure 9 , Figure 8 This is a simulation waveform diagram of the voltage of the power submodule 10 of a conventional linear switching strategy provided in an embodiment of this application; Figure 9 This is a simulated waveform of the voltage of the power submodule 10 of the valve control method for a DC power consumption device provided in an embodiment of this application. When this strategy is executed, the DC voltage external characteristics of the power consumption valve are basically consistent with the conventional linear switching strategy, achieving minimal switching disturbance of the DC power consumption device, while improving the voltage equalization characteristics of the power consumption valve submodule.

[0103] To facilitate understanding of the technical effects achieved by the valve control method for the DC energy-consuming device provided in the above embodiments, please refer to the following: Figures 10-14 , Figures 10-14 This is a simulation waveform diagram of the system DC voltage and power submodule 10 voltage of the valve control method of the DC energy dissipation device provided in this application. Taking an offshore wind power DC grid-connected project as an example, a simulation model of the DC energy dissipation device is established. The system DC voltage is ±500kV, the rated transmission power is 1500MW, the number of power submodules 10 in series in the energy dissipation valve is 456 (excluding redundancy), and the rated operating voltage of the power module is 2.2kV. The activation / deactivation voltage threshold of the DC energy dissipation device is set to 1020kV / 980kV. Under the fault condition of a three-phase metallic short circuit to ground, when the system transmission power takes different values ​​of 0.2 pu, 0.4 pu, 0.6 pu, 0.8 pu, and 1.0 pu, the system DC voltage U DBR and the voltage U of the energy-consuming valve submodule SM like Figures 10-14 As shown.

[0104] Simulation results show that: (1) With the control strategy of this embodiment, the DC energy consumption device can be put into operation in time after the fault occurs, and the peak value of the DC voltage between the poles does not exceed 1.10 times the set voltage, effectively suppressing the fault overvoltage and ensuring that the capacitor voltage of the MMC converter submodule is within the safe range; (2) With the control strategy of this scheme, before the fault is cleared, under the action of the DC energy consumption device, the fluctuation range of the DC voltage between the poles after entering the steady state is controlled within 0.97 times the reference voltage to 1.03 times the reference voltage, the voltage ripple level is low, and the system operation stability is high; (3) With the submodule triggering strategy of this scheme, during the energy consumption operation of the energy consumption device, the voltage dispersion of the submodule does not exceed 0.25 times the rated voltage (550V), that is, the voltage dispersion of the power submodule does not exceed one-quarter of the rated voltage, the voltage stress of each power submodule is balanced, and there is no overvoltage module; (4) With the low frequency control strategy, the DC energy consumption device can be quickly and reliably shut down after the fault is cleared, and there is no situation where it cannot be shut down or repeatedly put into operation after the fault is cleared.

[0105] Therefore, the above simulation results fully verify that the valve control method for DC energy consumption devices provided in this application has improved voltage control accuracy, sub-module voltage equalization characteristics and fault ride-through reliability, and has good application value.

[0106] Based on the valve control method for the DC power consumption device provided in the above embodiments, and with the same inventive concept, this application also provides a valve control device for a DC power consumption device corresponding to the above-described valve control method. The following describes... Figure 15 A detailed introduction to the valve control device of DC power consumption devices is provided.

[0107] Figure 15 A schematic diagram of the valve control device of a DC power dissipation device according to an embodiment of this application is shown. The DC power dissipation device includes at least one power dissipation valve and at least one power dissipation resistor, which are connected in series between the positive and negative lines. Figure 15 The valve control device 1500 of the DC power consumption device shown includes: The first acquisition module 1510 is used to acquire the initial DC voltage signal between the positive and negative lines, and to obtain the corresponding target DC voltage signal based on the initial DC voltage signal. The first control module 1520 is used to compare the target DC voltage signal with the input action voltage threshold of the DC energy-consuming device, and control at least one energy-consuming valve to open when the target DC voltage signal is higher than the input action voltage threshold. The second control module 1530 is used to compare the target DC voltage signal with the cut-off action voltage threshold of the DC energy-consuming device, and control at least one energy-consuming valve to shut off when the target DC voltage signal is lower than the cut-off action voltage threshold. The third control module 1540 is used to control the DC energy consumption device to lock out when it is detected that at least one energy consumption valve is in the off state and the continuous off-time of at least one energy consumption valve is greater than the lockout time threshold.

[0108] This application provides a valve control device for a DC power dissipation device. The DC power dissipation device includes at least one power dissipation valve and at least one power dissipation resistor, which are connected in series between the positive and negative lines. An initial DC voltage signal between the positive and negative lines is acquired, and a corresponding target DC voltage signal is obtained based on the initial DC voltage signal. Then, the target DC voltage signal is compared with an activation voltage threshold of the DC power dissipation device. If the target DC voltage signal is higher than the activation voltage threshold, at least one power dissipation valve is controlled to open. The target DC voltage signal is compared with a deactivation voltage threshold of the DC power dissipation device. If the target DC voltage signal is lower than the deactivation voltage threshold, at least one power dissipation valve is controlled to close.

[0109] As described above, the valve control device for a DC energy-consuming device according to an embodiment of this application employs a start-stop control strategy. The energy-consuming valve fully opens when the input threshold is reached and fully closes when the cut-off threshold is reached, rather than linearly adjusting the number of conducting modules. This start-stop control method significantly reduces the current change rate, achieving safe power dissipation without the need for a reactor, thus helping to reduce the device cost and size of the DC energy-consuming valve. Furthermore, by setting the aforementioned input and cut-off voltage thresholds, the DC voltage can be controlled within a certain range, reducing power fluctuations caused by linear regulation, reducing switching disturbances, and helping to maintain a low DC voltage ripple level, thereby improving the reliability of valve control operation.

[0110] Based on the valve control method for DC energy-consuming devices provided in the above embodiments, and with the same inventive concept, this application also provides a valve control device for a DC energy-consuming device corresponding to the above-described valve control method. The following describes... Figure 16 A detailed introduction to the valve control equipment of DC power consumption devices is provided.

[0111] Please see below. Figure 16 , Figure 16 This is a schematic diagram of the valve control device of a DC power consumption device provided in an embodiment of this application.

[0112] The valve control device for a DC power consumption device may include a processor 1601 and a memory 1602 storing computer program instructions.

[0113] Specifically, the processor 1601 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0114] Memory 1602 may include mass storage for data or instructions. For example, and not limitingly, memory 1602 may include a hard disk drive (HDD), floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 1602 may include removable or non-removable (or fixed) media. Where appropriate, memory 1602 may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, memory 1602 is non-volatile solid-state memory.

[0115] Memory may include read-only memory (ROM), random access memory (RAM), disk storage media devices, optical storage media devices, flash memory devices, and electrical, optical, or other physical / tangible memory storage devices. Therefore, typically, memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the methods according to one aspect of this disclosure.

[0116] The processor 1601 reads and executes computer program instructions stored in the memory 1602 to implement the valve control method of any DC power consumption device in the above embodiments.

[0117] In one example, the valve control device of the data DC power consumption device may further include a communication interface 1603 and a bus 1610. For example, Figure 16 As shown, the processor 1601, memory 1602, and communication interface 1603 are connected through bus 1610 and complete communication with each other.

[0118] The communication interface 1603 is mainly used to realize communication between various modules, devices, units and / or equipment in the embodiments of this application.

[0119] Bus 1610 includes hardware, software, or both, that couples components of a valve-controlled device of a DC power-consuming device together. For example, and not limitingly, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a Microchannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses, or combinations of two or more of these. Where appropriate, bus 1610 may include one or more buses. Although specific buses are described and illustrated in embodiments of this application, any suitable bus or interconnect is contemplated herein.

[0120] The valve control device of the DC energy-consuming device executes the valve control method of the DC energy-consuming device in the embodiments of this application, thereby realizing the valve control method of the DC energy-consuming device described in the embodiments of this application.

[0121] Furthermore, in conjunction with the valve control method for the DC power consumption device in the above embodiments, this application embodiment can provide a computer storage medium for implementation. The computer storage medium stores computer program instructions; when these computer program instructions are executed by a processor, they implement any of the valve control methods for the DC power consumption device in the above embodiments.

[0122] Based on the valve control method for DC power consumption devices in the above embodiments, this application provides a computer program product. When the instructions in the computer program product are executed by the processor of an electronic device, the electronic device performs the valve control method for DC power consumption devices provided in any of the above embodiments of this application.

[0123] It should be clarified that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this application.

[0124] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0125] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0126] The aspects of this disclosure have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can also be implemented by special-purpose hardware performing the specified functions or actions, or can be implemented by a combination of special-purpose hardware and computer instructions.

[0127] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A valve control method for a DC energy-consuming device, characterized in that, The DC power consumption device includes at least one power consumption valve and at least one power consumption resistor, wherein the at least one power consumption valve and the at least one power consumption resistor are connected in series between the positive and negative lines; the valve control method of the DC power consumption device includes: Acquire the initial DC voltage signal between the positive and negative lines, and obtain the corresponding target DC voltage signal based on the initial DC voltage signal; The target DC voltage signal is compared with the activation voltage threshold of the DC energy-consuming device. If the target DC voltage signal is higher than the activation voltage threshold, the at least one energy-consuming valve is controlled to open. The target DC voltage signal is compared with the cut-off action voltage threshold of the DC energy-consuming device. If the target DC voltage signal is lower than the cut-off action voltage threshold, the at least one energy-consuming valve is controlled to shut off.

2. The valve control method for the DC energy-consuming device according to claim 1, characterized in that, Before comparing the target DC voltage signal with the activation voltage threshold of the DC power-consuming device, and before comparing the target DC voltage signal with the deactivation voltage threshold of the DC power-consuming device, the method further includes: The target DC voltage signal is compared with the unlocking voltage threshold of the DC power consumption device. If the target DC voltage signal is higher than the unlocking voltage threshold, the DC power consumption device is unlocked. The comparison of the target DC voltage signal with the operating voltage threshold of the DC power consumption device includes: When the DC power consumption device is unlocked, the target DC voltage signal is compared with the activation voltage threshold. The comparison of the target DC voltage signal with the cut-off action voltage threshold of the DC power consumption device includes: When the DC power-consuming device is unlocked, the target DC voltage signal is compared with the cut-off action voltage threshold.

3. The valve control method for the DC energy-consuming device according to claim 2, characterized in that, After the control device for DC power consumption is unlocked, the method further includes: Record the duration of a single unlocking of the DC power-consuming device; If the duration of a single unlock reaches the longest continuous energy consumption time for a single unlock, the DC energy consumption device is locked. If the duration of a single unlock does not reach the maximum continuous energy consumption time for a single unlock, and if at least one energy-consuming valve is detected to be in a closed state, and the continuous closed duration of the at least one energy-consuming valve is greater than the lockout time threshold, the DC energy-consuming device is controlled to lock out.

4. The valve control method for the DC energy-consuming device according to claim 2, characterized in that, After comparing the target DC voltage signal with the unlocking voltage threshold of the DC power consumption device, the method further includes: When the target DC voltage signal is lower than or equal to the unlocking voltage threshold, the DC power consumption device is controlled to remain in a locked state.

5. The valve control method for the DC energy-consuming device according to claim 2, characterized in that, The unlocking voltage threshold is greater than or equal to the input action voltage threshold, and the input action voltage threshold is greater than the cut-off action voltage threshold.

6. The valve control method for the DC energy-consuming device according to claim 1, characterized in that, The at least one energy-consuming valve includes N power sub-modules, where N is a positive integer greater than 1; controlling the at least one energy-consuming valve to open or to close includes: The N power submodules are divided into multiple groups, and the multiple groups include at least a first group and a second group; In the first stage of the switching action triggering process of the energy-consuming valve opening or closing, the power submodule in the first group is put into or cut off at a first set time interval until the switching action of the first group is completed. In the second stage of the switching action triggering process, a power submodule in the second group is put into operation or cut off at a second set time interval, and a power submodule in the first group is cut off or put into operation at a second set time interval, so as to restore the state of the first group before the start of the first stage. In the third stage of the switching action triggering process, at each first set time interval, a power submodule in the first group is put on or cut off until the switching action of the first group is completed.

7. The valve control method for the DC energy-consuming device according to claim 6, characterized in that, The speed of the switch action in the first stage is the first speed, and the speed of the switch action in the second stage is the second speed, which is greater than the first speed.

8. The valve control method for the DC energy-consuming device according to claim 7, characterized in that, The second speed is twice the first speed; The first set time is T SW / (N-1), the second set time is T SW / 2(N-1), T SW The preset switching action time is N, where N is the number of power submodules included in the at least one energy-consuming valve.

9. The valve control method for the DC energy-consuming device according to claim 6, characterized in that, The division of the N power submodules into multiple groups includes: Collect the capacitor voltage of the DC capacitors in the N power submodules; The N power submodules are divided into the multiple groups according to the order of capacitor voltage from high to low during the activation action and from low to high during the deactivation action.

10. The valve control method for the DC energy-consuming device according to claim 6, characterized in that, The power submodule includes a DC capacitor; During the switching action of the energy-consuming valve opening or closing, the switching action of the power submodule is triggered in the order of the capacitor voltage of the DC capacitor from high to low when the action is turned on, and from low to high when the action is turned off.

11. The valve control method for the DC energy-consuming device according to any one of claims 1-10, characterized in that, The at least one energy-consuming valve includes a first energy-consuming valve and a second energy-consuming valve, and the at least one energy-consuming resistor includes a first energy-consuming resistor and a second energy-consuming resistor; The first energy-consuming valve and the second energy-consuming valve each include at least one power sub-module. The first energy-consuming valve and the first energy-consuming resistor are connected in series between the positive line and the midpoint. The second energy-consuming valve and the second energy-consuming resistor are connected in series between the negative line and the midpoint.

12. The valve control method for the DC energy-consuming device according to claim 11, characterized in that, The power submodule includes: a main switching device, a first diode, a DC capacitor, a first resistor, a second diode, and a second resistor; The first terminal of the main switching device is electrically connected to the first terminal of the power submodule, and the second terminal of the main switching device is electrically connected to the second terminal of the power submodule; The anode of the first diode is electrically connected to the second terminal of the power submodule, and the cathode of the first diode is electrically connected to the first terminal of the power submodule. The first resistor is connected in parallel with the first diode, the second resistor and the DC capacitor are connected in series and then in parallel with the first resistor, and the second diode is connected in parallel with the second resistor.

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