A method, device and medium for reducing energy consumption resistance-dependent fault ride-through control

Abstract

The application discloses a kind of fault ride-through control methods, equipment and medium for reducing energy consumption resistance dependence, belong to flexible direct current transmission system relay protection technical field, for solving the technical problems of higher cost of existing energy consumption resistance dependence mode, the flexibility of energy consumption resistance is insufficient, prone to over input energy consumption resistance, it will also affect the operation reliability of system.Method includes: the fluctuation degree estimation of voltage on DC side, obtain the surplus power of system under blocked export channel;For the fault location calculation of sending end MMC under the detection of high-frequency frequency component, obtain the AC fault section;The surplus power is divided into energy consumption resistance absorption type, determine the wind farm energy consumption resistance absorption power and AC energy consumption resistance absorption power;The first part of surplus power in surplus power is controlled to absorb power, to obtain the first energy consumption absorption strategy;The second part of surplus power in surplus power is controlled to absorb power, to obtain the second energy consumption absorption strategy.

Description

Technical Field

[0001] This application relates to the field of relay protection for flexible DC transmission systems, and in particular to a fault ride-through control method, device and medium for reducing energy consumption resistance dependence. Background Technology

[0002] After the faulty line is disconnected, the power transmission channel of the receiving-end MMC (Modular Multilevel Converter) will be interrupted due to the blocking, and the power transmitted from the DC grid will be reduced. Meanwhile, the power injected into the sending-end MMC connected to the new energy source will remain unchanged, resulting in a significant power imbalance in the DC grid.

[0003] Based on the above problems, existing projects mainly adopt the method of adding energy-consuming resistors, which utilize the heating of the resistors to consume the unbalanced active power of the system, effectively reducing the peak value of DC overvoltage. However, the large capacity requirement leads to high construction costs, and the energy-consuming resistors lack flexibility, resulting in the problem of over-installation of energy-consuming resistors. Furthermore, the switching of large-capacity energy-consuming resistors can seriously affect the operational reliability of the system. Therefore, there is an urgent need for a method that can reduce the dependence on energy-consuming resistors during fault ride-through. Summary of the Invention

[0004] This application provides a fault ride-through control method, device, and medium to reduce reliance on energy-consuming resistors, which addresses the following technical problems: existing energy-consuming resistor-dependent methods are costly, lack flexibility of energy-consuming resistors, are prone to over-investment of energy-consuming resistors, and can affect the operational reliability of the system.

[0005] The embodiments of this application adopt the following technical solutions:

[0006] On one hand, embodiments of this application provide a fault ride-through control method to reduce dependence on energy dissipation resistance, including: estimating the voltage fluctuation level on the DC side based on the fault state determined by the AC side of the receiving-end MMC to obtain the surplus power of the system under obstructed transmission channels; calculating the fault location of the sending-end MMC under high-frequency component detection based on the judgment result of whether there is power margin to participate in the adjustment to reduce the surplus power, to obtain the AC fault section; and classifying the surplus power according to the determined AC fault section by energy dissipation resistance absorption type to determine the wind farm energy dissipation resistance absorption type. The system absorbs power from the power source and the AC power-consuming resistor. Based on the reduced AC voltage state of the sending-end MMC and the power absorbed by the wind farm's power-consuming resistor, a first portion of the surplus power is controlled for power absorption, resulting in a first power absorption strategy. Based on the adaptive configuration rules of the AC power-consuming resistor on the sending-end MMC side and the power absorbed by the AC power-consuming resistor, a second portion of the surplus power is controlled for power absorption, resulting in a second power absorption strategy. The first portion of surplus power and the second portion of surplus power together constitute the surplus power.

[0007] This application's embodiments employ a fault ride-through control method that reduces dependence on AC power dissipation resistors, effectively decreasing reliance on these resistors and suppressing overvoltages caused by surplus power, thus enhancing system safety. By accurately estimating DC-side voltage fluctuations and determining fault conditions, a faster fault response can be achieved, reducing system instability and oscillations. Furthermore, by rationally allocating and adjusting the power absorbed by wind farm power dissipation resistors, reliance on traditional resistors can be reduced, thereby lowering system operating costs. Additionally, when an AC-side fault occurs, the system can continue operating by adjusting the DC-side voltage and power absorption strategy, improving fault ride-through capability. Simultaneously, the system can dynamically adjust the configuration of power dissipation resistors based on actual conditions, further enhancing system adaptability and flexibility. Moreover, fault location calculation using high-frequency component detection allows for rapid identification of fault sections, reducing fault detection time.

[0008] In one feasible implementation, based on the fault state determined by the AC side of the receiving-end MMC, the voltage fluctuation of the DC side is estimated to obtain the surplus power of the system under the condition of blocked transmission channel. Specifically, this includes: when the AC side of the receiving-end MMC is in a fault state, then based on... The voltage increment of MMC2 is obtained. ;in, For DC voltage fluctuations, This refers to the DC voltage of MMC2 in the DC system. MMCs include MMC1, MMC2, MMC3, and MMC4. MMC1 and MMC2 are both the sending end of the MMC-HVDC system and are VF controlled. MMC3 and MMC4 are both the receiving end of the MMC-HVDC system, with MMC3 controlled by a constant DC voltage and MMC4 controlled by a constant active power. According to... The absorbed energy of MMC2 is obtained. Where Ceq2 is the equivalent capacitance of converter station MMC2; according to The surplus power of the system under the condition that the MMC2 transmission channel is blocked is obtained. Among them, C eq1 C eq3 and C eq4 These are the equivalent capacitances of converter stations MMC1, MMC3, and MMC4, respectively; N1, N2, N3, and N4 are the number of sub-modules connected in series within converter stations MMC1, MMC2, MMC3, and MMC4, respectively. It is a time variable.

[0009] In one feasible implementation, based on the superposition result of harmonic components, the fault location is calculated for the sending-end MMC under high-frequency component detection to obtain the AC side fault of the constant power station MMC or the AC side fault of the constant voltage station MMC. Specifically, this includes: calculating the equivalent electrical distance between the constant power station MMC and the other MMCs to obtain a first fault transient frequency; calculating the equivalent electrical distance between the constant voltage station MMC and the other MMCs to obtain a second fault transient frequency; and performing fault location differentiation calculations for the first fault transient frequency and the second fault transient frequency under high-frequency component detection based on the frequency range, harmonic components, and square wave signal amplitude to determine the fault segment; wherein, the fault segment is the AC side fault of the constant power station MMC or the AC side fault of the constant voltage station MMC.

[0010] In one feasible implementation, based on the identified AC fault section, the surplus power is categorized by energy-consuming resistor absorption type to determine the wind farm energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power. Specifically, this includes: based on the identified AC fault section, obtaining the maximum transmission power and the transmission power before the fault in the corresponding MMC within the AC fault section; calculating the power difference between the maximum transmission power and the transmission power before the fault; performing a minimum value judgment process between the power difference and the surplus power to determine the adjustable resource power; correcting the difference between the surplus power and the adjustable resource power to obtain the total energy-consuming resistor absorption power; and based on the AC voltage of the sending-end MMC and the configuration of the AC energy-consuming resistor on the sending-end MMC side, dividing the total energy-consuming resistor absorption power into the wind farm energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power.

[0011] In one feasible implementation, by controlling the AC voltage reduction state of the sending-end MMC and absorbing power based on the power absorbed by the wind farm energy-consuming resistor, a first portion of the surplus power is subjected to power absorption control to obtain a first energy absorption strategy. Specifically, this includes: controlling the AC voltage reduction of the sending-end MMC to obtain the AC voltage reduction state; calculating the active power and reactive power transmitted in the wind farm based on the voltage and current components of the d-axis in the wind farm while the sending-end MMC is in the AC voltage reduction state; and based on the active power and reactive power transmitted in the wind farm, and by absorbing power through the wind farm energy-consuming resistor, controlling the absorption of the first portion of the surplus power through the wind farm energy-consuming resistor connected to the sending-end MMC1 and MMC2 sides to obtain the first energy absorption strategy.

[0012] In one feasible implementation, a second energy absorption strategy is obtained by using an adaptive configuration rule for the AC power dissipation resistor on the sending-end MMC side and by controlling the power absorption of the AC power dissipation resistor to absorb the second portion of the surplus power. Specifically, this includes: calculating the capacity of the second portion of the surplus power under multiple sets of equal capacity resistors to obtain the capacity of each set of AC power dissipation resistors; combining several sets of AC power dissipation resistors with different capacities based on the minimum power adjustment interval of the AC power dissipation resistors to obtain an adaptive configuration rule for the AC power dissipation resistor on the sending-end MMC side; and controlling the power absorption of the second portion of the surplus power according to the adaptive configuration rule for the AC power dissipation resistor on the sending-end MMC side, thereby obtaining the second energy absorption strategy.

[0013] In one feasible implementation, after performing power absorption control on the second portion of the surplus power to obtain a second energy absorption strategy, the method further includes: based on the first energy absorption strategy and the second energy absorption strategy, to complete the absorption control of surplus power during fault ride-through.

[0014] Secondly, embodiments of this application also provide a fault ride-through control device for reducing power consumption resistance dependence, the device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to execute a fault ride-through control method for reducing power consumption resistance dependence as described in any of the above embodiments.

[0015] Thirdly, embodiments of this application also provide a non-volatile computer storage medium, wherein the storage medium is a non-volatile computer-readable storage medium, the non-volatile computer-readable storage medium stores at least one program, each program including instructions, and the instructions, when executed by a terminal, cause the terminal to perform a fault ride-through control method for reducing power consumption resistance dependence as described in any of the above embodiments.

[0016] This application provides a fault ride-through control method, device, and medium for reducing energy consumption resistance dependence. Compared with the prior art, the embodiments of this application have the following beneficial technical effects:

[0017] 1. By accurately estimating the degree of DC-side voltage fluctuation and judging the fault status, fault response can be faster, reducing system instability and oscillation.

[0018] 2. By rationally allocating and adjusting the power absorbed by the energy-consuming resistors in wind farms, the dependence on traditional energy-consuming resistors can be reduced, thereby lowering the system's operating costs.

[0019] 3. When a fault occurs on the AC side, the system can continue to operate by adjusting the voltage and power absorption strategy on the DC side, thereby improving the system's fault ride-through capability.

[0020] 4. By distinguishing between different types of energy-consuming resistors that absorb power, power distribution can be optimized more effectively, thereby improving the overall system operating efficiency.

[0021] 5. Through adaptive configuration rules, the system can dynamically adjust the configuration of energy-consuming resistors according to actual conditions, further improving the system's adaptability and flexibility.

[0022] 6. By calculating the fault location through high-frequency component detection, the fault section can be quickly determined, reducing fault detection time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0024] Figure 1 A flowchart of a fault ride-through control method for reducing energy dissipation resistor dependence provided in an embodiment of this application;

[0025] Figure 2 A schematic diagram of the topology and control structure of a multi-terminal flexible DC power grid provided in this application embodiment;

[0026] Figure 3 A graph showing the relationship between surplus power and DC voltage is provided for an embodiment of this application;

[0027] Figure 4 An energy-time relationship diagram of MMC2 provided in an embodiment of this application;

[0028] Figure 5 A schematic diagram illustrating the principle of active fault area determination in a constant voltage control station, as provided in this application embodiment;

[0029] Figure 6 The DC voltage frequency spectrum-frequency relationship diagram provided in the embodiments of this application;

[0030] Figure 7 A schematic diagram of an AC energy-consuming resistor for a wind farm controlled by MMC at the sending end, provided in an embodiment of this application;

[0031] Figure 8 A power-time relationship diagram of a wind farm provided for an embodiment of this application;

[0032] Figure 9 This is a schematic diagram of a fault ride-through control device for reducing energy consumption resistance dependence, provided as an embodiment of this application. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0034] It's important to note that in the power system field, MMC stands for Modular Multilevel Converter. It's an advanced voltage source converter topology widely used in flexible DC transmission systems. An MMC consists of numerous basic sub-modules (such as half-bridge, full-bridge, or self-resisting sub-modules) connected in series. By precisely controlling the on / off states of these sub-modules, the output voltage level can be flexibly adjusted, achieving efficient and high-quality power conversion. Its main advantages include low output voltage harmonic content, low switching frequency, low losses, high modularity for easy expansion and maintenance, and flexible control. In the field of high-voltage DC transmission, MMC can effectively reduce harmonic interference to the power grid, improve power quality, and quickly regulate reactive power, enhancing the stability and reliability of the power grid.

[0035] This application focuses on multi-terminal MMC-HVDC systems. Figure 2 This application provides a schematic diagram of the topology and control structure of a multi-terminal flexible DC power grid, as shown in the following diagram. Figure 2 As shown in the figure. The submodules in the MMC converter station adopt an equivalent model. To provide stable AC voltage and frequency support to the wind farm, MMC1 and MMC2 use voltage-frequency control as equivalent voltage sources, while the power output of the wind farm is independently regulated by its own control system. The receiving-end converter station outputs active power, with MMC4 using constant power control to absorb active power. To balance the active power in the DC grid, MMC3 is set as the balancing node, therefore constant DC voltage control is used. The DC system parameters are shown in Table 1.

[0036] Table 1 System parameters of MMC-HVDC

[0037]

[0038] This application provides a fault ride-through control method that reduces dependence on energy dissipation resistance, such as... Figure 1 As shown, the fault ride-through control method for reducing energy consumption resistance dependence specifically includes steps S101-S105:

[0039] S101. Based on the fault status determined by the AC side of the receiving end MMC, estimate the voltage fluctuation of the DC side to obtain the surplus power of the system under the condition that the external transmission channel is blocked.

[0040] Specifically, when a fault occurs on the AC side of the receiving-end MMC, the resulting obstruction of the transmission channel and the resulting surplus power ΔP are the main sources of the initial voltage rise in the MMC capacitor. Taking MMC2 as an example, the DC side voltage change is detected as follows: Figure 2 As shown, the voltage increment ΔU = ΔU is obtained. MMC2 In other words, when the AC side of the receiving-end MMC is in a fault state, then according to... The voltage increment of MMC2 is obtained. .in, For DC voltage fluctuations, This refers to the DC voltage of MMC2 in the DC system. MMC includes MMC1, MMC2, MMC3, and MMC4. MMC1 and MMC2 are both the sending end of the MMC-HVDC system and are VF controlled. MMC3 and MMC4 are both the receiving end of the MMC-HVDC system. MMC3 is controlled by constant DC voltage, and MMC4 is controlled by constant active power.

[0041] In one embodiment, the voltage increment for MMC2 Considering that the DC voltage fluctuation is less than 0.05 pu during steady-state operation of the system, let U SET =1.05 pu, before the DC voltage reaches U SET The main source of energy injected into submodules is surplus power.

[0042] Furthermore, taking the period after the fault as the starting point, select T0~T SET The DC voltage on the MMC side of the transmission end of the interval, and then according to The absorbed energy of MMC2 is obtained. Among them, C eq2 It is the equivalent capacitance of converter station MMC2.

[0043] Furthermore, assuming that the DC-side voltage increase of each converter is consistent, the system surplus power can be estimated using local information from the MMC2 side, i.e.: based on The surplus power of the system under the condition that the MMC2 transmission channel is blocked is obtained. Among them, C eq1 C eq3 and C eq4 These are the equivalent capacitances of converter stations MMC1, MMC3, and MMC4, respectively; N1, N2, N3, and N4 are the number of sub-modules connected in series within converter stations MMC1, MMC2, MMC3, and MMC4, respectively. It is a time variable.

[0044] S102. Based on the judgment result of whether there is power margin to participate in the regulation to reduce surplus power, the fault location is calculated for the sending end MMC under the detection of relevant high frequency components to obtain the AC fault section.

[0045] It should be noted that since the sending-end MMC of the flexible DC power grid needs to provide stable voltage and frequency information to the wind farm, it mainly uses voltage-frequency control. However, constant DC voltage control needs to be set in the receiving-end MMC to maintain DC system voltage stability, and constant power control needs to be set in the other receiving-end MMCs. If a fault occurs on the AC side of the constant power station MMC, the constant power station fails, and the constant voltage station MMC3 rises to its upper limit as the power changes. Conversely, if a fault occurs on the AC side of the constant voltage station MMC, the constant voltage station fails, and the constant power station maintains the active power before the fault. Further analysis is needed to determine whether the constant power station MMC has a power margin to participate in regulation to reduce surplus power ΔP.

[0046] Specifically, in order to accurately distinguish AC fault sections, when a fault occurs on the constant voltage MMC3 side, active injection control is introduced in the fault station MMC3 to superimpose the harmonic components onto the DC common mode components, so as to distinguish the faults on the AC side of the constant power station MMC and the AC side of the constant voltage station MMC. Figure 3 A graph showing the relationship between surplus power and DC voltage is provided in an embodiment of this application. Figure 4 An energy-time relationship diagram of MMC2 is provided for embodiments of this application, such as... Figure 3 as well as Figure 4 As shown, in a constant-power station MMC, a power margin is involved in regulation to reduce surplus power. Therefore, the faulty station MMC is subject to active injection control, and harmonic components are superimposed on the DC operating mode components. The faulty station MMC is a constant-voltage station.

[0047] Furthermore, based on the superposition results of harmonic components, it is also necessary to calculate the fault location of the sending-end MMC under the detection of relevant high-frequency components to obtain the AC side fault of the constant power station MMC or the AC side fault of the constant voltage station MMC.

[0048] As a feasible implementation method, the equivalent electrical distance between the constant power station MMC and the other MMCs is calculated to obtain the first fault transient frequency. Then, the equivalent electrical distance between the constant voltage station MMC and the other MMCs is calculated to obtain the second fault transient frequency. Finally, based on the frequency range, harmonic components, and square wave signal amplitude, the fault location is determined by high-frequency component detection for both the first and second fault transient frequencies to identify the fault segment. The fault segment is either an AC-side fault in the constant power station MMC or an AC-side fault in the constant voltage station MMC.

[0049] In one embodiment, Figure 5 This application provides a schematic diagram of a constant voltage control station actively injecting fault area determination. Figure 6 The DC voltage frequency spectrum-frequency relationship diagram provided in the embodiments of this application is as follows: Figure 5 , 6and combination Figure 2 As shown, when a fault occurs on the AC side of the MMC in a constant power station, the equivalent electrical distances from the faulty MMC4 to MMC1 and MMC2 are L1=L 12 +L 24 and L2=L 24 The calculation method for the equivalent electrical distance of faults on the AC side of the MMC in a constant voltage substation is similar. Then, substituting the transmission line parameters, the calculated frequency range is 125-50Hz, and the determined harmonic component is 400Hz with an amplitude U. F1 A square wave signal of 0.0025 pu is used to detect harmonic components on the MMC2 side to determine the fault section, as shown in the following formula: , where k F1 The reliability coefficient is set to 1.2.

[0050] Furthermore, based on the fault location corresponding to the AC side fault of the MMC at a constant power station or the AC side fault of the MMC at a constant voltage station, the AC fault section is determined.

[0051] S103. Based on the identified AC fault sections, the surplus power is classified according to the energy-consuming resistor absorption type to determine the wind farm energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power.

[0052] Specifically, based on the identified AC fault section, the maximum transmission power of the corresponding MMC in the AC fault section and the transmission power before the fault are obtained.

[0053] Furthermore, the power difference between the maximum transmission power and the transmission power before the fault is calculated. Then, the minimum value between the power difference and the surplus power is determined to identify the adjustable resource power.

[0054] Furthermore, the difference between the surplus power and the adjustable resource power is corrected to obtain the total energy-consuming resistor absorbed power. Finally, based on the AC voltage of the sending-end MMC and the configuration of the AC energy-consuming resistor on the sending-end MMC side, the total energy-consuming resistor absorbed power is divided into the wind farm energy-consuming resistor absorbed power and the AC energy-consuming resistor absorbed power.

[0055] In one embodiment, when the fault segment is determined by detecting harmonic components on the MMC2 side... Then, it is necessary to further evaluate whether the MMC4 has sufficient power margin and correct for excess power within the system. That is, according to , where P max This is the maximum transmission power of MMC4, P 40 It is the transmission power before the fault, ΔP 4refIt is an MMC4 adjustable power resource. The corrected surplus power ΔP is divided into the power absorbed by the wind farm's energy-consuming resistor ΔP1 and the power absorbed by the AC energy-consuming resistor ΔP2.

[0056] S104. By reducing the AC voltage state of the sending-end MMC and absorbing power based on the energy-consuming resistor of the wind farm, the first part of the surplus power is subjected to power absorption control to obtain the first energy absorption strategy.

[0057] Specifically, the sending-end MMC first needs to be controlled to reduce AC voltage to achieve an AC voltage reduction state. Then, with the sending-end MMC in the AC voltage reduction state, the active and reactive power transmitted in the wind farm needs to be calculated based on the voltage and current components along the d-axis of the wind farm.

[0058] Furthermore, based on the active and reactive power transmitted in the wind farm, and by absorbing power through the wind farm energy-consuming resistors, the first part of the surplus power is absorbed and controlled by the wind farm energy-consuming resistors connected to the sending end MMC1 and MMC2 sides, thus generating the first energy absorption strategy.

[0059] In one embodiment, by slightly reducing the AC voltage of multiple sending-end MMCs, some of the surplus power is absorbed by the wind farm's energy-dissipating resistors. For example... Figure 2 As shown, the sending-end converter stations MMC1 and MMC2 provide stable voltage and frequency for the wind farm. The phase-locked loop of the wind farm always follows the phase of the grid connection point voltage and satisfies the requirement that the AC voltage component U on the wind farm side in the q-axis (quadrature axis) is constant. WFq =0, reactive power is zero. According to instantaneous power theory, the active and reactive power transmitted by the wind farm are then calculated, that is: Among them, U WFd It is the voltage component along the d-axis in the wind farm, i WFd This is the d-axis current component in the wind farm. Line impedance can be ignored, and U... WFd =U acref Reduce the AC voltage setting values ​​of the sending end MMC1 and MMC2. Figure 7 A schematic diagram of an AC energy-consuming resistor for a wind farm controlled by MMC at the sending end, provided in an embodiment of this application. Figure 8 The wind farm power-time relationship diagram provided in the embodiments of this application is as follows: Figure 7 as well as Figure 8 As shown, to prevent the wind farm from entering the low voltage ride-through region, ΔU acref The upper limit is set to 0.1 pu, and then according to , where k ac It is the AC voltage coefficient, with a value of 1.5, in U acrefAfter the value decreases, ΔP1 (the first part of the surplus power) will be absorbed by the wind farm energy-consuming resistors connected to the sending end MMC1 and MMC2, thereby generating the first energy-consuming absorption strategy.

[0060] S105. By using the adaptive configuration rules of the AC power dissipation resistor on the sending end MMC side, and based on the power absorbed by the AC power dissipation resistor, the second part of the surplus power is subjected to power absorption control to obtain the second power absorption strategy. The first part of the surplus power and the second part of the surplus power together constitute the surplus power.

[0061] Specifically, the second part of the surplus power is first calculated using multiple sets of equal-capacity resistors to obtain the capacity of each set of AC dissipation resistors.

[0062] Furthermore, based on the minimum power adjustment interval of the AC power dissipation resistor, several AC power dissipation resistor groups with different capacities are combined to obtain the adaptive configuration rule of the AC power dissipation resistor on the sending end MMC side.

[0063] Furthermore, based on the adaptive configuration rules of the AC power consumption resistor on the sending end MMC side, and by absorbing power through the AC power consumption resistor, the second part of the surplus power is subjected to power absorption control, thus obtaining the second power absorption strategy.

[0064] In one embodiment, the remaining surplus power (the second part of the surplus power) is absorbed by the AC energy-dissipating resistor on the sending-end MMC side. By optimizing the configuration of the AC energy-dissipating resistor on the sending-end MMC side, the appropriate energy-dissipating resistor is accurately connected, reducing the expansion of surplus power due to excessive connection. The remaining surplus power ΔP2 = (ΔP - ΔP1) needs to be absorbed by the AC energy-dissipating resistor on the MMC2 side. In engineering, the AC energy-dissipating device uses n sets of resistors with equal capacity connected in parallel. Considering the complexity of AC energy-dissipating resistor control, the value of n cannot be too large, so the value of n is taken as 4; that is: , where P DBRi This is the capacitance of each AC dissipation resistor group. When ΔP DBR When the value is high, the AC power dissipation resistor has low flexibility and is easily affected by voltage and power fluctuations caused by excessive AC power dissipation resistor input.

[0065] In one embodiment, this application also designs a non-equal AC energy-consuming resistor group based on the bisection method. Utilizing the calculated capacity ΔPDBR of each AC energy-consuming resistor group, multiple AC energy-consuming resistor groups with different capacities are combined to match different ΔP2 values, thereby achieving flexible and accurate input. That is: according to... and To obtain the adaptive configuration rules for the AC power dissipation resistor on the sending end MMC side, that is, to determine the appropriate power dissipation resistor; at this time, the minimum power adjustment interval of the AC power dissipation resistor is: Ultimately, the AC power-absorbing resistor can be used to absorb power, and the second part of the surplus power can be controlled to obtain the second power absorption strategy.

[0066] Furthermore, based on the first and second energy absorption strategies mentioned above, the absorption and control of surplus power during fault ride-through can be completed.

[0067] As a feasible implementation method, compared with the fault ride-through control method for reducing dependence on energy dissipation resistors proposed in this application, the minimum power regulation relationship between the AC energy dissipation resistors of the two methods is represented by k: As n increases, the value of k decreases. When n equals 4, the value of k is 0.27. Based on the above minimum power regulation relationship, it can be shown that the power regulation of the AC power consumption resistor of the fault ride-through control method with reduced power consumption resistor dependence proposed in this application is only 0.27 times that of the traditional method, and can more accurately match ΔP2 (second part of surplus power).

[0068] In one embodiment, such as Figure 2 As shown, it is assumed that the fault duration in the multi-terminal MMC-HVDC system of this application is 200 milliseconds; and two methods are set up: the fault ride-through control proposed in this application and the traditional method. When a fault occurs on the AC side of the constant power MMC, assuming U fault =0.19pu. Under the processing of the method proposed in this application, the AC voltage of the sending end MMC1 and MMC2 is slightly reduced, and the wind farm no longer needs to inject reactive power. The active power absorbed by the wind farm's energy-consuming resistor is ΔP1=210MW. Using the improved non-equivalent AC energy-consuming resistor, ΔP2=900MW is absorbed; compared with the traditional method, the energy absorbed by the proposed method is reduced by 51.0%. Similarly, when a fault occurs on the AC side of the constant voltage MMC, assuming U fault =0.19pu, under the proposed method, the active power absorbed by the wind farm's energy-consuming resistor is ΔP1=210MW. Using the improved non-equivalent AC energy-consuming resistor, ΔP2=200MW is absorbed. Compared with the traditional method, the proposed method reduces the absorbed energy by 36.8%. In other words, the technical solution provided by the above embodiments of this application can improve the safety of the system by mitigating the safety hazards caused by overvoltage risks resulting from the interruption of surplus power after an AC fault.

[0069] In addition, embodiments of this application also provide a fault ride-through control device that reduces dependence on power dissipation resistance, such as... Figure 9 As shown, the fault ride-through control device 900, which reduces energy consumption resistance dependence, specifically includes:

[0070] At least one processor 901; and a memory 902 communicatively connected to the at least one processor 901; wherein the memory 902 stores instructions executable by the at least one processor 901 to enable the at least one processor 901 to execute:

[0071] Based on the fault status determined by the AC side of the receiving end MMC, the voltage fluctuation of the DC side is estimated to obtain the surplus power of the system under the condition that the external transmission channel is blocked.

[0072] Based on the judgment result of whether there is power margin to participate in the regulation to reduce surplus power, the fault location of the sending end MMC is calculated under the detection of relevant high frequency components to obtain the AC fault section.

[0073] Based on the identified AC fault sections, the surplus power is classified according to the energy-consuming resistor absorption type to determine the wind farm's energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power.

[0074] By reducing the AC voltage state of the sending-end MMC and absorbing power based on the energy-consuming resistor of the wind farm, the first part of the surplus power is subjected to power absorption control to obtain the first energy absorption strategy.

[0075] By using the adaptive configuration rules of the AC power dissipation resistor on the sending end MMC side, and based on the power absorption of the AC power dissipation resistor, the second part of the surplus power is subjected to power absorption control to obtain the second power absorption strategy; wherein, the first part of the surplus power and the second part of the surplus power together constitute the surplus power.

[0076] This application's embodiments employ a fault ride-through control method that reduces dependence on AC power dissipation resistors, effectively decreasing reliance on these resistors and suppressing overvoltages caused by surplus power, thus enhancing system safety. By accurately estimating DC-side voltage fluctuations and determining fault conditions, a faster fault response can be achieved, reducing system instability and oscillations. Furthermore, by rationally allocating and adjusting the power absorbed by wind farm power dissipation resistors, reliance on traditional resistors can be reduced, thereby lowering system operating costs. Additionally, when an AC-side fault occurs, the system can continue operating by adjusting the DC-side voltage and power absorption strategy, improving fault ride-through capability. Simultaneously, the system can dynamically adjust the configuration of power dissipation resistors based on actual conditions, further enhancing system adaptability and flexibility. Moreover, fault location calculation using high-frequency component detection allows for rapid identification of fault sections, reducing fault detection time.

[0077] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device and medium embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the description of the method embodiments.

[0078] The devices and media provided in this application are one-to-one with the methods. Therefore, the devices and media also have similar beneficial technical effects as their corresponding methods. Since the beneficial technical effects of the methods have been described in detail above, the beneficial technical effects of the devices and media will not be repeated here.

[0079] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0080] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0081] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0082] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0083] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0084] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0085] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0086] It should also be noted that 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 limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0087] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of this specification.

Claims

1. A fault ride-through control method for reducing energy consumption resistance dependence, characterized in that, The method includes: Based on the fault status determined by the AC side of the receiving end MMC, the voltage fluctuation of the DC side is estimated to obtain the surplus power of the system under the condition that the external transmission channel is blocked. Based on the determination of whether there is power margin involved in adjusting and reducing the surplus power, the fault location is calculated for the sending-end MMC under high-frequency component detection to obtain the AC fault section, specifically including: If the constant power station MMC has a power margin involved in adjusting and reducing the surplus power, then the fault station MMC will be actively injected with the introduction control, and the harmonic components will be superimposed on the DC power mode components; wherein, the fault station MMC is a constant voltage station; Based on the superposition results of harmonic components, the fault location of the sending-end MMC is calculated under the detection of relevant high-frequency components, so as to obtain the AC side fault of the constant power station MMC or the AC side fault of the constant voltage station MMC. Based on the identified fault locations corresponding to the AC side faults of the constant power station MMC or the constant voltage station MMC, the AC fault section is determined. Based on the identified AC fault sections, the surplus power is classified according to the energy-consuming resistor absorption type to determine the wind farm energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power. By reducing the AC voltage state of the MMC at the sending end and absorbing power based on the energy-consuming resistor of the wind farm, the first part of the surplus power is subjected to power absorption control to obtain the first energy absorption strategy. By using the adaptive configuration rules of the AC power dissipation resistor on the sending end MMC side, and based on the power absorbed by the AC power dissipation resistor, the second part of the surplus power is subjected to power absorption control to obtain the second power absorption strategy; wherein, the first part of the surplus power and the second part of the surplus power together constitute the surplus power. Among them, MMC includes: MMC1, MMC2, MMC3 and MMC4, and MMC1 and MMC2 are both the sending end of the MMC-HVDC system, while MMC3 and MMC4 are both the receiving end of the MMC-HVDC system.

2. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, Based on the fault status determined by the AC side of the receiving-end MMC, the voltage fluctuation on the DC side is estimated to obtain the surplus power of the system under the condition of blocked transmission channel, specifically including: When the AC side of the receiving-end MMC is in a fault state, then according to The voltage increment of MMC2 is obtained. ;in, For DC voltage fluctuations, This refers to the DC voltage of MMC2 in the DC system. MMC includes MMC1, MMC2, MMC3, and MMC4. MMC1 and MMC2 are both the sending end of the MMC-HVDC system and are VF controlled. MMC3 and MMC4 are both the receiving end of the MMC-HVDC system. MMC3 is controlled by constant DC voltage, and MMC4 is controlled by constant active power. according to The absorbed energy of MMC2 is obtained. Among them, C eq2 It is the equivalent capacitance of converter station MMC2; according to The surplus power of the system under the condition that the MMC2 transmission channel is blocked is obtained. Among them, C eq1 C eq3 and C eq4 These are the equivalent capacitances of converter stations MMC1, MMC3, and MMC4, respectively; N1, N2, N3, and N4 are the number of sub-modules connected in series within converter stations MMC1, MMC2, MMC3, and MMC4, respectively. It is a time variable.

3. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, Based on the superposition of harmonic components, the fault location of the sending-end MMC is calculated under the detection of relevant high-frequency components, resulting in AC side faults of the MMC in constant power stations or constant voltage stations. Specifically, this includes: For the constant power station MMC, the fault equivalent electrical distance between the other MMCs is calculated to obtain the first fault transient frequency; The equivalent electrical distance between the faults of the MMCs of the constant voltage substation and the other MMCs is calculated to obtain the second fault transient frequency. Based on the frequency range, harmonic components, and square wave signal amplitude, the fault location is determined by detecting the relevant high-frequency components of the first fault transient frequency and the second fault transient frequency, respectively, to identify the fault section; wherein, the fault section is the AC side fault of the constant power station MMC or the AC side fault of the constant voltage station MMC.

4. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, Based on the identified AC fault sections, the surplus power is categorized by energy-consuming resistor absorption type to determine the wind farm's energy-consuming resistor absorption power and the AC energy-consuming resistor absorption power, specifically including: Based on the identified AC fault section, the maximum transmission power of the corresponding MMC in the AC fault section and the transmission power before the fault are obtained. Calculate the power difference between the maximum transmission power and the transmission power before the fault; The adjustable resource power is determined by comparing the power difference with the surplus power to find the minimum value. The difference between the surplus power and the adjustable resource power is corrected to obtain the total energy-consuming resistor absorption power. Based on the AC voltage of the sending-end MMC and the configuration of the AC energy-consuming resistor on the sending-end MMC side, the total energy-consuming resistor absorbed power is divided into the wind farm energy-consuming resistor absorbed power and the AC energy-consuming resistor absorbed power.

5. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, By reducing the AC voltage state of the MMC at the sending end and absorbing power based on the energy-consuming resistor of the wind farm, the first portion of the surplus power is subjected to power absorption control to obtain the first energy absorption strategy, which specifically includes: The AC voltage reduction control is applied to the MMC at the sending end to obtain the AC voltage reduction state; With the MMC at the sending end in the state of reduced AC voltage, the active power and reactive power transmitted in the wind farm are calculated based on the voltage and current components of the d-axis in the wind farm. Based on the active and reactive power transmitted in the wind farm, and by absorbing power through the wind farm energy-consuming resistor, the first part of the surplus power is absorbed and controlled by the wind farm energy-consuming resistor connected to the sending end MMC1 and MMC2, thus obtaining the first energy absorption strategy.

6. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, By using the adaptive configuration rules of the AC power dissipation resistor on the sending-end MMC side, and based on the power absorbed by the AC power dissipation resistor, the second portion of the surplus power is subjected to power absorption control to obtain a second power absorption strategy, which specifically includes: The second part of the surplus power is used to calculate the resistance capacity under multiple sets of equal capacity to obtain the capacity of each set of AC dissipation resistors. Based on the minimum power adjustment interval of the AC power dissipation resistor, several AC power dissipation resistor groups with different capacities are combined to obtain the adaptive configuration rule of the AC power dissipation resistor on the sending end MMC side. Based on the adaptive configuration rules of the AC power dissipation resistor on the sending end MMC side, and by absorbing power through the AC power dissipation resistor, the second part of the surplus power is subjected to power absorption control to obtain the second power absorption strategy.

7. The fault ride-through control method for reducing energy consumption resistance dependence according to claim 1, characterized in that, After applying power absorption control to the second portion of the surplus power to obtain a second energy absorption strategy, the method further includes: Based on the first energy absorption strategy and the second energy absorption strategy, the absorption and control of surplus power during fault ride-through is completed.

8. A fault ride-through control device for reducing energy consumption resistance dependence, characterized in that, The device includes: At least one processor; and, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor to enable the at least one processor to perform a fault ride-through control method for reducing power consumption resistance dependence according to any one of claims 1-7.

9. A non-volatile computer storage medium, characterized in that, The storage medium is a non-volatile computer-readable storage medium that stores at least one program, each program including instructions that, when executed by a terminal, cause the terminal to perform a fault ride-through control method for reducing power consumption resistor dependence according to any one of claims 1-7.

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