Quantitative analysis method, device and equipment for voltage supporting capacity of wind power direct current delivery system and storage medium

Abstract

The invention provides a quantitative analysis method, device and equipment for the voltage supporting capacity of a wind power direct current delivery system and a storage medium. Relates to the technical field of new energy power system safety and stability control. The method comprises the following steps: based on transient response characteristics of a direct current system and a wind power system in a fault stage and a recovery stage, establishing a mapping relation among direct current system rectifier reactive power consumption, wind turbine generator output reactive power and bus transient voltage, and determining the two as transient voltage dominant factors; and according to the rectifier trigger angle constraint, the inverter turn-off angle constraint, the commutation angle constraint and the direct current constraint, determining the adjustable range of the direct current, and calculating the reactive power consumption extreme value of the rectifier in combination with a reactive power consumption formula. And dynamically calculating the maximum output reactive power and the maximum absorption reactive power of the fan through a stator side power equation and a grid-connected point voltage equation based on rotor current constraint. According to the invention, the transient voltage can be effectively suppressed while the space is adjusted by fully utilizing each regulation and control resource.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of safety and stability control of new energy power systems, and particularly relates to a wind power direct current outward transmission system voltage support capability quantitative analysis method and device, equipment and a storage medium. BACKGROUND

[0002] The strength of the sending end alternating current system containing new energy is reduced, and the voltage support capability is weakened. When the alternating current or direct current system fails, the voltage of the sending end alternating current system is prone to instability, which causes new energy to be off the grid and commutation failure, and other problems, thereby restricting large-scale development of new energy and safe and stable operation of the power grid.

[0003] In recent years, existing technologies have made some research progress in the transient voltage characteristics and suppression strategies of the sending end of the DC transmission system. In terms of transient voltage characteristic analysis, the literature "Gong Haoyue, Guo Jianbo, Guo Qiang, et al. Overvoltage calculation method of sending system under DC fault disturbance considering the influence of renewable energy [J]. CSEE Journal of Power and Energy Systems, 2024.", "Yan Jiaying, Liu Qihui, Li Kaixin, et al. DC commutation failure transient overvoltage suppression based on DFIG reactive power optimization control [J]. Electric Power Automation Equipment, 2024, 44 (10): 32-38." and "WANG Tong, PEI Lin, WANG Jiaming, et al. Overvoltage suppression under commutation failure based on improved voltage-dependent current order limiter control strategy [J]. IEEE Transactions on Industry Applications, 2022, 58(4): 4914-4922.》Research shows that commutation failure at the receiving end of HVDC transmission will cause transient voltage instability in the AC system at the sending end. A mathematical model of transient voltage of the AC system at the sending end considering the reactive dynamic response of the AC / DC system is constructed, and the influence of factors such as control mode and system parameters on the overvoltage amplitude is analyzed. However, only the overvoltage characteristics are analyzed, and the impact on low voltage has not been considered. The literature "Yin Chunya, Li Fengting. Analytical expression on transient overvoltage peak value of converter bus caused by DC faults [J]. IEEE Transactions on Power Systems, 2021, 36 (3): 2741-2744." and "Wang Feng, Liu Tianqi, Ding Yuanyuan, et al. Calculation method of transient overvoltage caused by DC blocking and analysis of influencing factors [J]. Power System Technology, 2016, 40 (10): 3059-3065." Based on the blocking scenario of high-voltage DC transmission converter stations, a method for calculating the peak overvoltage at the sending end under DC blocking faults is proposed, and the influence of factors such as DC system strength and blocking capacity on overvoltage is analyzed.The paper "Jia Junchuan, Jin Yiding, Zhao Bing, et al. Influence of wind turbine low voltage ride through control on system transient overvoltage and optimization [J]. Power System Technology, 2021, 45(02): 526-533." reveals the mechanism of wind farm low voltage ride through process exacerbating system transient overvoltage, and analyzes the differentiating influence of different low voltage ride through control strategies on wind turbine power output characteristics and system transient voltage, but the influence of wind turbine dynamic response on voltage amplitude during system overvoltage needs to be discussed. In the aspect of stability control strategy, the paper "Luo Xu-zhi, Zhang Jian, He Jing-bo, et al. Coordinated control of DC blocking protection and pole control considering transient overvoltage constraint [J]. Power System Technology, 2015, 39(09): 2526-2531." proposes a coordinated control strategy of protection and pole control based on the principle that improper timing of pole control filter and protection wind turbine action after DC blocking leads to sending end system overvoltage, which achieves the purpose of suppressing overvoltage. The papers "Qin Yan-hui, Yin Chun-ya, Duan Qing-xi, et al. Transient voltage characteristic analysis and support strategy research under DC near-zone system fault [J]. Power System Protection and Control, 2023, 51(17): 169-177." and "Liang Wei, Shen Chen, Sun Huadong, et al. Overvoltage mechanism and suppression method for LCC-HVDC rectifier station caused by sending end AC faults [J]. IEEE Transactions on Power Delivery, 2022, 39(2): 1299-1302." respectively propose a transient voltage control method that adjusts the rectifier reactive power consumption according to the severity of the fault, which reduces the voltage fluctuation amplitude, but the reactive power regulation capacity of each resource is not fully tapped. The paper "Xiao Ran, Guo Chun-yi, Zhao Dong-jun. Transient low / overvoltage characteristics and suppression methods of UHVDC transmission system with separate site construction [J / OL]. Proceedings of the Chinese Society of Electrical Engineering, 1-11." proposes to adjust the reactive power consumption of high and low voltage valve groups by regulating DC current, and then suppresses the transient voltage instability caused by commutation failure of UHVDC transmission system.The document "Jin Xiao, Nian Heng, Zhao Cheng, et al. Optimal power coordinated control strategy for DFIG-based wind farm to increase transmission capacity of the LCC-HVDC system considering commutation failure [J]. IEEE journal of emerging and selected topics in power electronics, 2021, 10(3):3129-3139." proposes an optimal power coordinated control strategy for the rotor converter and the grid-side converter of a doubly-fed wind turbine to suppress overvoltage in the sending-end AC system caused by commutation failure, thereby reducing the risk of overvoltage in the sending-end.

[0004] In summary, the existing technology focuses on the voltage characteristics of isolated phases during low voltage during faults or overvoltage during recovery, and only considers the single influence of part of the equipment, lacking comprehensive analysis of the whole process characteristics of the regulation resources. At the same time, the traditional design of DC current limit restricts the reactive power regulation capability of the rectifier, making it difficult to fully utilize the voltage regulation potential of the DC system. In addition, the fixed coefficient-based reactive power instruction calculation and switching threshold design of wind turbines easily lead to regulation mismatch and control overshoot, making it difficult to fully balance the reactive power of AC and DC systems, and there is a problem of insufficient utilization of voltage regulation resources. Therefore, it is necessary to clarify the transient voltage regulation capability of each regulation resource, fully tap its regulation potential, realize the coordinated cooperation of voltage regulation resources based on the flexible control of the DC system and the wind power system, and improve the transient voltage stability of the wind power DC transmission system. SUMMARY

[0005] The present application provides a wind power DC transmission system voltage support capability quantitative analysis method, device, equipment and storage medium, on the basis of analyzing the transient voltage response characteristics of wind power and DC, a calculation model of the transient voltage of the sending-end system is established, and the influence law of different factors and links on the transient voltage is revealed; considering the safe operation constraint of equipment, a quantitative analysis scheme of the transient voltage support capability of wind power and DC is proposed, and the reactive power regulation space of each resource under different disturbance conditions is clarified.

[0006] In a first aspect, the present application provides a wind power DC transmission system voltage support capability quantitative analysis method, comprising:

[0007] Based on dynamic response characteristics of the DC system and the wind power system, mapping relationships between relevant factors of the DC system and the wind power system and the bus transient voltage are respectively established, and based on the mapping relationships, a DC system transient voltage dominant factor and a wind power system transient voltage dominant factor are determined; wherein the dynamic response characteristics include bus transient voltage dynamic responses in a fault stage and a recovery stage, the DC system transient voltage dominant factor includes rectifier reactive power consumption, and the wind power system transient voltage dominant factor includes reactive power output by a wind turbine generator;

[0008] The rectifier reactive power consumption is used to quantify the DC system reactive power regulation capability, including: determining a DC current adjustable range according to rectifier trigger angle constraints, inverter shutdown angle constraints, commutation angle constraints and DC current constraints, and based on the DC current range and a rectifier reactive power consumption calculation formula, calculating a maximum value and a minimum value of the rectifier reactive power consumption;

[0009] The reactive power output by the wind turbine generator is used to quantify the wind power system reactive power regulation capability, including: based on rotor current constraints, combining a stator side power equation and a grid connection point voltage equation, calculating maximum output reactive power of the wind turbine and maximum absorbed reactive power of the wind turbine.

[0010] In a possible design, based on dynamic response characteristics of the DC system, a mapping relationship between relevant factors of the DC system and the bus transient voltage is established in the following manner:

[0011] A basic expression of the bus transient voltage U p is determined as follows:

[0012]

[0013] In the expression, U s represents an equivalent source voltage of a sending end AC system, X s represents an equivalent reactance from the sending end AC system to a grid connection point, P s and Q s respectively represent active power and reactive power output by the system;

[0014] Taking total differentials of P s and Q s yields:

[0015]

[0016] In the expression, U p0 represents an initial value of the bus transient voltage, P s0 and Q s0 respectively represent initial values of active power and reactive power output by the system;

[0017] U sSubstitute equation (3) into equation (2) as a constant value, and the bus transient voltage variation is obtained as:

[0018]

[0019] ΔQ s = ΔQ dr + Q cr0 - Q cr (5)

[0020]

[0021] In equation (5), ΔU p represents the AC bus voltage variation, ΔQ s represents the system output reactive power variation, Q cr represents the reactive power transmitted by the rectifier side reactive power compensation device, Q cr0 represents the initial value of the reactive power transmitted by the rectifier side reactive power compensation device, ΔQ dr represents the DC reactive power variation;

[0022] The bus transient voltage in the fault stage and the recovery stage is determined by the following equation:

[0023]

[0024] In equation (6), t n represents the time when the fault starts, t f represents the time when the fault ends, ΔU p1 represents the free component generated by ΔQ s in the fault stage, ΔU p2 represents the free component generated by ΔQ s in the recovery stage, U f represents the forced component of the voltage caused by the equivalent impedance at the fault point, t represents the time variable, and U pN represents the rated voltage of the sending-end bus;

[0025] The sending-end system short circuit capacity is determined by the following equation:

[0026]

[0027] In equation (7), S ac represents the sending-end system short circuit capacity, U sN represents the rated voltage of the DC system, S cr represents the short circuit ratio, and P dN represents the rated power of the DC system;

[0028] Substitute equation (5) into equation (4) to obtain the equation about ΔU p , and further solve the equation combined with equation (8) to obtain ΔUp The expression is as follows:

[0029]

[0030] In the formula, Q c0 represents the rated reactive capacity of the parallel reactive compensation device before failure or in steady state operation;

[0031] Substituting formula (9) into formula (7), the mapping relationship between the correlation factor of the DC system and the bus transient voltage is obtained:

[0032]

[0033] In a possible design, based on the dynamic response characteristics of the wind power system, the mapping relationship between the correlation factor of the wind power system and the bus transient voltage is established in the following manner:

[0034] The relationship between the fan power and the bus transient voltage of the wind power system during operation is determined and expressed as:

[0035]

[0036]

[0037] In the formula, A represents a first calculation coefficient, B represents a second calculation coefficient, C represents a third calculation coefficient, D represents a fourth calculation coefficient, U pN represents the rated voltage of the sending-end bus, X m represents the equivalent reactance between the AC system and the bus, U m represents the equivalent voltage of the equivalent synchronous unit, R m represents the equivalent resistance between the AC system and the bus, P w represents the active power output by the wind turbine, Q dc represents the reactive power of the DC system, P dc represents the active power of the DC system, Q w represents the reactive power output by the wind turbine;

[0038] After ignoring the active component of the fan, the mapping relationship between the correlation factor of the wind power system and the bus transient voltage is obtained:

[0039]

[0040] In the formula, C' represents a fifth calculation coefficient.

[0041] In a possible design, the formula for calculating the reactive power consumption of the rectifier is:

[0042]

[0043] In the formula, Q drrepresents the rectifier reactive power consumption, I dc represents the DC current, N represents the number of converters, U p represents the bus transient voltage, T1 represents the rectifier-side converter transformer ratio, α1 represents the rectifier firing angle, X c1 represents the rectifier commutation reactance.

[0044] In one possible design, the DC current adjustable range is determined according to the rectifier firing angle constraint, the inverter turn-off angle constraint, the commutation angle constraint and the DC current constraint, including:

[0045] The rectifier firing angle constraint is used to constrain the lower limit of the rectifier firing angle, where the rectifier firing angle is represented by:

[0046]

[0047] where α represents the rectifier firing angle, U dr represents the rectifier-side DC voltage;

[0048] The minimum turn-off angle γ is taken as the minimum turn-off angle to ensure that the reverse voltage acting on the thyristor for the shortest recovery blocking capability time min , where the inverter turn-off angle is calculated by: min

[0049]

[0050] where X c2 represents the inverter-side commutation reactance, U i represents the inverter-side commutation bus voltage, U di represents the inverter-side DC voltage, T2 represents the inverter-side converter transformer ratio;

[0051] The commutation angle constraint is taken as the commutation angle constraint that the rectifier and inverter commutation angles do not exceed the set commutation angle, where the rectifier and inverter commutation angles are determined by:

[0052]

[0053] where μ1 and μ2 represent the rectifier and inverter commutation angles, respectively;

[0054] The maximum and minimum limits of the DC current are determined according to the rated DC current, and the DC current is located between the maximum and minimum limits as the DC current constraint;

[0055] The determined DC current adjustable range is represented by:

[0056]

[0057] where I​dcN Indicates the rated DC current, γ N Indicates the rated turn-off angle.

[0058] In one possible design, based on the rotor current constraint, combined with the stator-side power equation and the grid-connected voltage equation, the maximum wind turbine output reactive power and the maximum wind turbine absorbed reactive power are calculated, including:

[0059] Determine the stator side power equation, which is expressed as:

[0060]

[0061] Where U w Indicates the voltage at the wind power grid connection point, P G , Q G Indicates the active and reactive power output on the stator side, s indicates the slip rate, I sd , I sq Indicates the d and q axis components of the stator current, Q w Indicates the reactive power of the wind turbine;

[0062] Based on the stator side power equation, combined with the wind turbine grid connection point voltage equation and stator flux equation, the rotor current component expression is determined as:

[0063]

[0064] Where, P w Indicates the active power of the wind turbine, I rd , I rq Indicates the d-axis and q-axis components of the rotor current, Q s Indicates the reactive power output by the system, L m Indicates the magnetizing inductance of the fan, L s represents the stator inductance of the wind turbine, ω s Indicates the fan stator angular frequency.

[0065] according to Determine the rotor current constraint, expressed as:

[0066]

[0067] Where, I r Represents the rotor current, I rmax Indicates the maximum value of the rotor current;

[0068] Calculate the maximum value of stator reactive current under low voltage and overvoltage conditions based on rotor current constraints:

[0069]

[0070] Where, I sqomaxI sqimax represents the maximum value of the stator reactive current under over-voltage working condition;

[0071] Substituting formula (23) into formula (21) to obtain the maximum value expression of the fan output and absorption reactive power:

[0072]

[0073] In the formula, Q womax represents the maximum output reactive power of the fan, Q wimax represents the maximum absorption reactive power of the fan.

[0074] In a possible design, the method further comprises:

[0075] Based on the DC system reactive power regulation capability and the wind power system reactive power regulation capability, an adaptive reactive power cooperative control strategy is determined; wherein the adaptive reactive power cooperative control strategy comprises:

[0076] Real-time monitored AC bus voltage U p is obtained.

[0077] When U p is lower than the set voltage threshold, it is determined to be a low-voltage working condition, in which the fan reactive power output is increased and the rectifier reactive power consumption is reduced; wherein the adjusted fan reactive power output does not exceed the maximum output reactive power of the fan, and the adjusted rectifier reactive power consumption is between the maximum value and the minimum value of the rectifier reactive power consumption.

[0078] When U p is not lower than the set voltage threshold, it is determined to be an over-voltage working condition, in which the fan reactive power absorption is increased and the rectifier reactive power consumption is increased; wherein the adjusted fan reactive power absorption does not exceed the maximum absorption reactive power of the fan, and the adjusted rectifier reactive power consumption is between the maximum value and the minimum value of the rectifier reactive power consumption.

[0079] In a second aspect, the application provides a wind power DC transmission system voltage support capability quantitative analysis device, the device comprises:

[0080] A dominant factor determination module is configured to establish a mapping relationship between relevant factors of the DC system and the wind power system and the bus transient voltage based on the dynamic response characteristics of the DC system and the wind power system, and to determine the DC system transient voltage dominant factor and the wind power system transient voltage dominant factor based on the mapping relationship; wherein the dynamic response characteristics include the bus transient voltage dynamic response in the fault stage and the recovery stage, the DC system transient voltage dominant factor includes the rectifier reactive power consumption, and the wind power system transient voltage dominant factor includes the reactive power output of the wind turbine generator set.

[0081] The direct current reactive power quantification module is configured to quantify the direct current system reactive power regulation capability based on the rectifier reactive power consumption, and includes determining a direct current current adjustable range according to rectifier trigger angle constraints, inverter shutdown angle constraints, commutation angle constraints and direct current current constraints, and calculating a maximum value and a minimum value of the rectifier reactive power consumption based on the direct current current range and a rectifier reactive power consumption calculation formula.

[0082] The wind power reactive power quantification module is configured to quantify the wind power system reactive power regulation capability based on the wind turbine output reactive power, and includes calculating the maximum wind turbine output reactive power and the maximum wind turbine absorbed reactive power based on rotor current constraints, combining a stator side power equation and a grid connection point voltage equation.

[0083] In a third aspect, an electronic device is provided, including at least one processor and a memory, the memory storing computer execution instructions, and the at least one processor executing the computer execution instructions stored in the memory, so that the at least one processor executes the wind power direct current transmission system voltage support capability quantification analysis method as described in the first aspect and various possible designs of the first aspect.

[0084] In a fourth aspect, a computer readable storage medium is provided, and the computer readable storage medium stores computer execution instructions, and when a processor executes the computer execution instructions, the wind power direct current transmission system voltage support capability quantification analysis method as described in the first aspect and various possible designs of the first aspect is implemented.

[0085] In a fifth aspect, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the wind power direct current transmission system voltage support capability quantification analysis method as described in the first aspect and various possible designs of the first aspect is implemented.

[0086] The wind power direct current transmission system voltage support capability quantification analysis method, device, equipment and storage medium provided by the present application have at least the following beneficial effects:

[0087] 1) Based on the analysis of the wind power and direct current transient voltage response characteristics, the present application establishes a calculation model of the sending end system transient voltage, and reveals the influence law of different factors and links on the transient voltage.

[0088] 2) The present application quantitatively analyzes the rectifier reactive power regulation capability considering the direct current current constraint, and quantitatively characterizes the reactive power regulation capability of the doubly-fed wind turbine considering the rotor current limitation.

[0089] 3) The application considers the reactive power regulation space constraints of each resource to propose an adaptive reactive power coordinated control strategy for different disturbance conditions, realizes real-time generation and dynamic distribution of control instructions based on voltage tracking, effectively alleviates the control overshoot caused by response delay, and improves the system recovery performance.

[0090] 4) The application builds a simulation model in MATLAB / SIMULINK, verifies the accuracy of the influence law of different factors and links on voltage, and the effectiveness and superiority of the proposed coordinated control strategy for transient voltage suppression. BRIEF DESCRIPTION OF DRAWINGS

[0091] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0092] Figure 1 A flowchart of a wind power direct current outward transmission system voltage support capability quantitative analysis method provided for the embodiments of the application;

[0093] Figure 2 A large-scale wind power through high-voltage direct current outward transmission system control structure diagram provided for the embodiments of the application;

[0094] Figure 3 A fault period direct current system transient response characteristic diagram provided for the embodiments of the application;

[0095] Figure 4 A recovery period direct current system transient response characteristic diagram provided for the embodiments of the application;

[0096] Figure 5 A system simplified equivalent circuit model diagram provided for the embodiments of the application;

[0097] Figure 6 A U-I-Q characteristic curve diagram provided for the embodiments of the application under different active power conditions; p -Q dc characteristic curve diagram;

[0098] Figure 7 A U-I-Q dynamic characteristic diagram provided for the embodiments of the application under different trigger angles; p -I dc -Q dr characteristic curve diagram;

[0099] Figure 8 A rectifier side direct current adjustable range diagram provided for the embodiments of the application;

[0100] Figure 9 A rectifier reactive power consumption adjustable range diagram provided for the embodiments of the application;

[0101] Figure 10 A I-U characteristic curve diagram provided for the embodiments of the application under different trigger angles;sqomax 、I sqimax -P w -U w dynamic characteristic diagram of fan output and maximum value of absorbed reactive power;

[0102] Figure 11 a dynamic characteristic diagram of fan output and maximum value of absorbed reactive power provided for the embodiment of the present application;

[0103] Figure 12 a dynamic characteristic diagram of U f and ΔQ dr on U p ;

[0104] Figure 13 a dynamic characteristic diagram of U p -ΔQ dr sensitivity coefficient;

[0105] Figure 14 a dynamic characteristic diagram of U p -U f sensitivity coefficient;

[0106] Figure 15 a dynamic characteristic diagram of U p -P w , U p -Q w characteristic curve varying with S cr ;

[0107] Figure 16 a diagram of relationship between bus transient voltage and fan reactive power under different working conditions provided for the embodiment of the present application;

[0108] Figure 17 a structural diagram of a voltage support capability quantification analysis device of a wind power direct current outward transmission system provided for the embodiment of the present application.

[0109] The specific embodiments of the present application have been shown through the above-mentioned diagrams, and will be described in more detail hereinafter. These diagrams and textual descriptions are not intended to limit the scope of the concept of the present application by any means, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0110] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The following description is only one of the embodiments in accordance with the present application, and is not intended to limit the scope of the present application. Rather, they are merely examples of devices and methods in accordance with some aspects of the present application, as detailed in the appended claims.

[0111] In the technical solution of this application, the collection, storage, use, processing, transmission, provision and disclosure of information such as financial data or user data involved comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0112] It should be noted that in the embodiments of the present application, certain software, components, models and other existing solutions in the industry may be mentioned. They should be regarded as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of the present application, but it does not mean that the applicant has or will necessarily use the solution.

[0113] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0114] The weak support characteristics of large-scale wind power transmission via high-voltage direct current (HVDC) are prominent, and AC faults at the sending end can easily cause transient voltage instability, posing severe challenges to the safe and efficient transmission of wind power. Based on this, the embodiment of the present application proposes a quantitative analysis method for the voltage support capacity of a wind power DC transmission system. On the basis of analyzing the transient voltage response characteristics of wind power and DC, a calculation model for the transient voltage of the sending-end system is established, revealing the influence of different factors and links on transient voltage; considering the constraints on equipment safe operation, a quantitative analysis method for the transient voltage support capacity of wind power and DC is proposed, clarifying the reactive regulation space of each resource under different disturbance conditions. Relying on the MATLAB / SIMULINK platform, a simulation model of a large-scale wind power transmission via high-voltage direct current (HVDC) system was built to verify the influence of different factors and links on voltage and the effectiveness and advantages of the proposed collaborative control strategy on transient voltage suppression.

[0115] like Figure 1 As shown, it is a specific flow chart of the voltage support capability quantitative analysis method of the wind power DC transmission system provided in an embodiment of the present application. The voltage support capability quantitative analysis method of the wind power DC transmission system includes the following steps S100-S300.

[0116] S100: Based on the dynamic response characteristics of the DC system and the wind power system, a mapping relationship between the relevant factors of the DC system and the wind power system and the bus transient voltage is established respectively, and the dominant factors of the DC system transient voltage and the wind power system transient voltage are determined based on the mapping relationship; wherein the dynamic response characteristics include the dynamic response of the bus transient voltage in the fault stage and the recovery stage, the dominant factor of the DC system transient voltage includes the rectifier reactive power consumption, and the dominant factor of the wind power system transient voltage includes the reactive power output of the wind turbine.

[0117] The structure of the wind power DC transmission system is shown in Figure 2 The transient voltage characteristics of the system are analyzed considering the typical operating mode of the wind turbine and the sending-end converter station. The doubly-fed wind turbine adopts constant power control; the sending-end converter station adopts constant current (CC) control, voltage dependent current order limiter (VDCOL) and minimum firing angle control, and the receiving-end converter station adopts constant extinction angle (CEA) control, current error controller (CEC), CC and VDCOL. p U w and U m are the grid-connected point voltage and the equivalent voltage of the equivalent synchronous unit, respectively, w , m are the equivalent reactance between the wind turbine, the AC system and the bus; P w / Q w , P m / Q m are the active power / reactive power output by the wind turbine and the equivalent synchronous unit, respectively; Q cr is the reactive power transmitted by the reactive power compensation device on the rectifier side; P dr , Q dr are the DC active power and reactive power.

[0118] The dynamic response characteristics of the DC system and the factors affecting the transient voltage are analyzed as follows:

[0119] During the fault-to-recovery process of the sending-end AC system, the transient voltage presents a change rule of first falling and then rising, which stimulates the dynamic response of the wind power system and the DC system, and further affects the transient low voltage and overvoltage evolution characteristics of the system. The transient response characteristics of the DC system and the wind power system and the influence mechanism on the voltage will be analyzed respectively.

[0120] The dynamic response of the DC system in the fault stage is shown in Figure 3 The drop or interruption of the DC power is caused by the voltage drop on the rectifier side, and the sudden drop of the DC current is caused by the initial response delay of the inverter station. The rectifier maintains the current stable by gradually reducing the firing angle, and finally enters the minimum firing angle control mode; the inverter side adopts the strategy of increasing the extinction angle to reduce the DC voltage and increase the current. In this process, the reduction of the reactive power consumption of the rectifier may be lower than the local compensation capacity, at which time the remaining reactive power will support the bus voltage. When the firing angle instruction β i of the inverter constant current control exceeds the extinction angle instruction β γ of the constant extinction angle control, the DC voltage will be reduced to the minimum extinction angle control mode.At this stage, the system switches to constant current control mode. Its higher current reference command accelerates the trigger angle adjustment, causing the DC voltage to quickly track the reference value. During this stage, the rectifier's reactive power demand increases significantly. If the rectifier's reactive power exceeds its compensation capacity, it must absorb reactive power from the AC system, causing the voltage to drop further.

[0121] The dynamic response of the DC system during the recovery phase is as follows: Figure 4 As shown. After the fault is cleared, the AC voltage recovery prompts the rectifier to switch to constant current control, but the VDCOL limit delays the current recovery, suppresses the reactive power growth of the rectifier, and causes the filter to have excess reactive power, which triggers system overvoltage. The inverter side suppresses the current rise by reducing the turn-off angle. However, the double-end constant current control causes the turn-off angle adjustment to fail, increasing the risk of commutation failure. When the overvoltage peak falls back to the steady state, the rectifier side adjusts the current to the VDCOL limit, and the inverter side adjusts the voltage to stabilize the DC current. In this process, the frequent action of the current deviation control causes β γ Sudden increase, when β γ >β i When the inverter returns to fixed turn-off angle control, and β γ A sudden increase raises the lower limit of the shutdown angle. This increased shutdown angle increases reactive power consumption, potentially causing a voltage drop on the inverter side and increasing the risk of commutation failure. The system ultimately recovers steady-state operation through dynamic regulation.

[0122] The voltage level of the large-scale centralized wind power transmission system is high, and the system impedance is large, so the influence of resistance can be ignored. Figure 5 Shown is the simplified equivalent circuit model of the system.

[0123] According to this equivalent model, the bus transient voltage U p Expressed as:

[0124]

[0125] Where U s Represents the equivalent power supply voltage of the sending-end AC system, X s P represents the equivalent reactance from the sending end AC system to the grid connection point. s and Q s They represent the active power and reactive power output by the system respectively.

[0126] Assume that the initial value of bus transient voltage is U p0 The initial values ​​of the system output active and reactive power are P s0 , Q s0 , for P s , Q s Find the total differential:

[0127]

[0128]

[0129] where U p0 represents the initial value of bus transient voltage, P s0 and Q s0 represent the initial values of system output active and reactive power, respectively.

[0130] Since the branch voltage horizontal component of active power has little effect on U p , the influence mechanism of system reactive power on U p is mainly studied. In formula (3), U p0 = U pN = 1, and U s is regarded as a constant value U s = U s0 = 1 because the duration from fault to recovery is very short. Substituting formula (3) into formula (2) and rearranging, the bus transient voltage variation is obtained as follows:

[0131]

[0132] ΔQ s = ΔQ dr + Q cr0 - Q cr (5)

[0133]

[0134] where ΔU p represents the AC bus voltage variation, ΔQ s represents the system output reactive power variation, Q cr represents the reactive power transmitted by the rectifier side reactive power compensation device, Q cr0 represents the initial value of reactive power transmitted by the rectifier side reactive power compensation device, and ΔQ dr represents the DC reactive power variation.

[0135] In the fault stage, the dynamic change of bus voltage is the superposition of the forced component U f caused by the equivalent impedance at the fault point and the free component ΔU s caused by the action of ΔQ p1 , where the smaller U f is, the more serious the fault is. In the recovery stage, the dynamic change of bus voltage is only embodied in the free component ΔU p2 , and the bus transient voltage in different stages is shown as follows:

[0136]

[0137] where t n represents the time when the fault starts, t f represents the time when the fault ends, and ΔU p1The fault stage is represented by ΔQ s The free component of the action, ΔU p2 The recovery phase is represented by ΔQ s The free component generated by the action, U f represents the forced component of the voltage caused by the equivalent impedance of the fault point, t represents the time variable, U pN Indicates the rated voltage of the sending-end bus.

[0138] Under ideal steady-state operating conditions, the reactive exchange quantity Q between AC and DC systems is s0 Approaches zero. In addition, the short-circuit capacity of the sending-end system can be approximately expressed as:

[0139]

[0140] Where S ac Indicates the short-circuit capacity of the sending end system, U sN Indicates the rated voltage of the DC system, S cr Indicates short-circuit ratio, P dN Indicates the rated power of the DC system.

[0141] Substituting Equation (5) into Equation (4) yields the following equation about ΔU: p After further solving the equation and combining it with formula (8), we can get ΔU p The expression is as follows:

[0142]

[0143] Where Q c0 Indicates the rated reactive capacity of the parallel reactive compensation device before a fault or during steady-state operation.

[0144] Substituting formula (9) into formula (7), we can get U p The expression, that is, the mapping relationship between the relevant factors of the DC system and the bus transient voltage is expressed as:

[0145]

[0146] Formula (10) shows that the magnitude of transient voltage during fault period is mainly related to the change of reactive power consumption of rectifier ΔQ dr , the voltage force component U that characterizes the severity of the fault f and the short-circuit ratio S, which characterizes the system strength cr Among them, U p with U f There is a positive correlation, and U f U p The influence of U decreases as its amplitude decreases; p and ΔQ dr There is a negative correlation, and ΔQ dr The increase in amplitude will enhance its effect on Up In addition, the greater the short-circuit ratio, the stronger the system and the smaller the voltage drop. The magnitude of the transient voltage during the recovery period is mainly related to ΔQ dr and S cr About U p Similarly, with ΔQ dr There is a negative correlation, and S cr The larger the value, the smaller the overvoltage amplitude.

[0147] The dynamic response characteristics of the wind power system and the factors affecting transient voltage are analyzed as follows:

[0148] When an AC system fault causes a drop in the sending bus voltage, the turbine-side voltage also drops. When the voltage falls below the threshold, the rotor converter switches to reactive power priority control mode, dynamically adjusting the rotor current to suppress overcurrent while simultaneously increasing the stator current to generate additional reactive power to support the wind turbine. If the voltage drops significantly, the rotor converter may shut down due to overcurrent, causing the wind turbine to lose its reactive power support capability or even disconnect from the grid.

[0149] During the voltage recovery phase, the wind turbine-side voltage rises synchronously with the bus voltage, and reactive injection gradually decreases. At this point, the system may experience transient overvoltages due to reactive overcompensation. This is primarily due to reduced reactive losses caused by reduced active power during low voltage ride-through, as well as excessive reactive output caused by control switching delays. When the overvoltage at the turbine-side exceeds the threshold, the rotor converter switches to reactive absorption mode to suppress the overvoltage. If the overvoltage persists above the protection threshold, insufficient high voltage ride-through capability may cause the wind turbine to disconnect from the grid.

[0150] Depend on Figure 2 It can be seen that during the operation of the wind power system, the wind turbine power and bus voltage have the following relationship:

[0151]

[0152]

[0153] In the formula, A represents the first calculation coefficient, B represents the second calculation coefficient, C represents the third calculation coefficient, D represents the fourth calculation coefficient, and U pN Indicates the rated voltage of the sending end bus, X m Indicates the equivalent reactance between the AC system and the busbar, U m Indicates the equivalent voltage of the equivalent synchronous unit, R m Indicates the equivalent resistance between the AC system and the busbar, P w Indicates the active power output by the wind turbine, Q dc Represents the reactive power of the DC system, P dc Indicates the active power of the DC system, Q w Indicates the reactive power output by the wind turbine.

[0154] Formula (11) shows that the active and reactive power output by the wind turbine can regulate the bus voltage: P w U p The supporting effect of Q is weak and further weakened with the increase of short-circuit ratio; w with U p It is positively correlated with U p The effect of φ also decreases with the increase of short-circuit ratio.

[0155] Based on the above analysis, the influence of DC power can be ignored when calculating bus transient voltage. Combined with the characteristics of wind power system power on voltage, and further ignoring the active component of wind turbine, the simplified U p With Q w The analytical relationship between the relevant factors of the wind power system and the bus transient voltage is obtained as follows:

[0156]

[0157] Wherein, C′ represents the fifth calculation coefficient.

[0158] According to formula (13) Figure 6 The U shown p -Q dc Characteristic curves, where curve a (standard curve) takes into account the influence of DC power and wind turbine active power; curve b ignores DC power; and curve c ignores all active components of the system. Comparative analysis shows that the maximum errors of curves b and c with the standard curve are 2.657% and 4.473%, respectively. Since DC power transmission must follow the voltage-current balance relationship and is constrained by DC current and system impedance, ignoring the active component will reduce the system power flow, resulting in U p The amplitude is higher than the standard curve, but the overall difference is small. This result shows that Q w U p dominant regulatory role.

[0159] In summary, the reactive parameters of the DC system and the wind power system are key factors affecting transient voltage. Therefore, it is necessary to quantify the reactive regulation boundaries between the two and coordinately utilize the reactive regulation potential of wind power and DC power within their safe operating ranges to effectively reduce the risk of transient voltage instability while ensuring equipment safety.

[0160] S200: Quantifying the reactive power regulation capability of the DC system based on the reactive power consumption of the rectifier, including: determining the adjustable range of the DC current according to the rectifier trigger angle constraint, the inverter turn-off angle constraint, the commutation angle constraint and the DC current constraint, and calculating the maximum and minimum values ​​of the rectifier reactive power consumption based on the DC current range and the rectifier reactive power consumption calculation formula.

[0161] Specifically, in combination with the above detailed analysis of step S100, it can be determined that the rectifier reactive power consumption Q dr is a key factor affecting the bus transient voltage U p Q dr The expression is shown in equation (15):

[0162]

[0163] In the formula, Q dr represents the rectifier reactive power consumption, I dc represents the DC current, N represents the number of converters, U p represents the bus transient voltage, T1 represents the rectifier side converter transformer ratio, α1 represents the rectifier trigger angle, X c1 represents the rectifier commutation reactance.

[0164] Equation (15) shows that Q dr is positively correlated with U p , I dc and α1. And from Figure 7 It can be seen that I dc and U p under different α1 have a synergistic effect, and the increase of any parameter will enhance the adjustment sensitivity of the other parameter to Q dr .

[0165] The sudden change of the sending end bus transient voltage is the result of both the fault itself and the reactive imbalance of the AC / DC system. Therefore, the DC current needs to be adjusted to fully utilize the reactive power regulation capability of the rectifier, but at the same time, attention needs to be paid to the risk of current interruption and commutation failure caused by current amplitude out-of-limit. The key system constraints such as rectifier trigger angle and inverter turn-off angle must be considered.

[0166] 1) Rectifier trigger angle constraint

[0167] In engineering practice, a lower limit of the trigger angle needs to be set to ensure reliable commutation of the system during the fault transient process. Therefore, it is generally required that α≥5°. The analytical expression of the trigger angle α is shown in equation (16):

[0168]

[0169] In the formula, α represents the rectifier trigger angle, U dr represents the DC voltage on the rectifier side.

[0170] 2) Inverter turn-off angle constraint

[0171] Generally, the minimum turn-off angle is taken as the minimum turn-off angle corresponding to the shortest action time of the reverse voltage that ensures the recovery blocking capability of the thyristor, and whether the minimum turn-off angle is out-of-limit is used to judge commutation failure. Generally, γ min= 7°-9°. The analytical expression of the turn-off angle γ is shown in equation (17):

[0172]

[0173] where X c2 represents the commutation reactance on the inverter side, U i represents the commutation bus voltage on the inverter side, U di represents the DC voltage on the inverter side, and T2 represents the transformer ratio on the inverter side.

[0174] When considering the turn-off angle constraint, the calculation of the DC current extreme value should take the rated turn-off angle γ N as the minimum limit condition to ensure a safety margin to cope with uncertain factors such as AC voltage drop.

[0175] 3) Commutation angle constraint of rectifier / inverter

[0176] During the operation of the 12-pulse converter, each 6-pulse bridge exhibits a periodic conduction characteristic under normal operating conditions: 5 valves and 4 valves are kept on during commutation and non-commutation periods, respectively. When the commutation angle μ > 30°, the converter will have a transient 6-valve parallel conduction. This inter-bridge coupling effect will cause significant voltage waveform distortion, so the critical value of the commutation angle is set to 30°. The expressions of the commutation angles of the rectifier and the inverter are shown in equation (18):

[0177]

[0178] where μ1 and μ2 represent the commutation angles of the rectifier and the inverter, respectively.

[0179] 4) DC current constraint

[0180] The setting of the maximum limit of the DC current mainly considers the tolerance of each device. Excessive DC current can cause device overheating damage and commutation failure, etc. The typical value of 1.4I dcN is usually used in engineering. When the DC current is too small, it can trigger resonance, and in severe cases, it can cause current discontinuity. The value of 0.1I dcN is usually taken as the minimum limit of the DC current, where I dcN represents the rated DC current.

[0181] Based on the above multi-factor constraints, by analyzing the correlation characteristics of each factor and the DC current, the operating range of the DC current can be determined as follows:

[0182]

[0183] where I dcN represents the rated DC current, γ N represents the rated turn-off angle.

[0184] Based on the literature "Zhang T, Yao J, Sun P, et al. Improved continuous fault ridethrough control strategy of DFIG-based wind turbine during commutationfailure in the LCC-HVDC transmission system [J]. IEEE Transactions on PowerElectronics, 2020, 36(1): 459-473." method, Figure 8 Display I dcmax with U p Positively correlated: U p When >0.947pu, the rectifier maintains constant current control, U p <0.947pu switches to minimum firing angle control, I dcmax The rate of change decreases. Figure 9 It shows that the maximum reactive power consumption of the rectifier is Q drmax Changing trends and I dcmax With consistency, the minimum value of rectifier reactive power consumption Q drmin The change is not obvious during the voltage drop. Under low voltage conditions, the system needs to reduce the reactive power consumption of the rectifier, but Q dr Received dc Constraints, its adjustable range is limited; and under overvoltage conditions, the system needs to increase the reactive power consumption of the rectifier, Q dr Follow U p Increase synchronously, and Q drmax The regulation range and speed are significantly improved, making the DC system more capable of regulating under overvoltage conditions. Furthermore, while the constraints limit the DC reactive power regulation range, they also reduce the risk of problems such as commutation failure.

[0185] S300: Quantify the reactive power regulation capability of the wind power system based on the reactive power output of the wind turbine, including: calculating the maximum output reactive power and the maximum absorbed reactive power of the wind turbine based on the rotor current constraint, combined with the stator side power equation and the grid connection point voltage equation.

[0186] Specifically, the reactive power regulation capability of the wind turbine is mainly constrained by the rotor current. Based on this constraint, a quantitative analysis of the reactive power regulation capability of the wind turbine is carried out below.

[0187] The power expression of the stator side output is as follows:

[0188]

[0189] Where UV w represents the wind farm grid point voltage, P G , Q G represents the stator side output active and reactive power, s represents the slip, I sd , I sq represents the stator current d, q axis component, Q w represents the wind turbine reactive power.

[0190] Combining the wind farm grid point voltage equation and the stator flux linkage equation, the rotor current component expression can be obtained according to equation (20):

[0191]

[0192] In the equation, P w represents the wind turbine active power, I rd , I rq represents the rotor current d, q axis component, Q s represents the system output reactive power, L m represents the wind farm magnetizing inductance, L s represents the wind farm stator inductance, ω s represents the wind farm stator angular frequency.

[0193] According to the rotor current expression can be obtained:

[0194]

[0195] In the equation, I r represents the rotor current, I rmax represents the maximum value of the rotor current.

[0196] According to the rotor current constraint, the maximum value of the stator reactive current under low and over voltage conditions can be calculated:

[0197]

[0198] In the equation, I sqomax represents the maximum value of the stator reactive current under low voltage condition, I sqimax represents the maximum value of the stator reactive current under over voltage condition.

[0199] Substituting equation (23) into equation (21), the wind farm output and absorption reactive maximum value expression can be obtained:

[0200]

[0201] In the equation, Q womax represents the wind farm maximum output reactive, Q wimax represents the wind farm maximum absorption reactive.

[0202] Formula (23) shows that the maximum reactive current on the stator side I sqomax , I sqimax Depends on the active power P of the wind turbine w , grid connection point voltage U w And slip rate s. Under low voltage conditions, I sqomax With P w 、U w are negatively correlated; and under overvoltage conditions, I sqimax With P w Negatively correlated with U w Positive correlation, specific influence rules are as follows Figure 10 As shown. Further according to formula (24) and Figure 11 (a) and (c) show that the maximum output reactive power Q under low voltage conditions is womax With P w Negatively correlated with U w Positive correlation; maximum absorbed reactive power Q under overvoltage conditions wimax With P w Negatively correlated with U w The overvoltage amplitude is positively correlated. Figure 11 (b) and (d) show that compared with Q womax , Q wimax For the terminal voltage U w More sensitive to changes in P w Running on a weakened U w Q womax and Q wimax While affecting, limiting Q womax and Q wimax The amplitude of the voltage is affected, thereby restricting the wind turbine's ability to regulate voltage.

[0203] From the above analysis, it can be seen that doubly fed wind turbines face the contradiction between increased reactive output demand and limited output capacity under low voltage conditions, resulting in a gradual decline in their reactive regulation capability; while the increased reactive absorption demand and improved absorption capacity under overvoltage conditions promote each other, making the wind turbine's ability to suppress overvoltage better than its ability to support low voltage.

[0204] In some embodiments, the method further comprises: determining an adaptive reactive coordinated control strategy based on the reactive regulation capability of the DC system and the reactive regulation capability of the wind power system; wherein the adaptive reactive coordinated control strategy comprises: obtaining the real-time monitored AC bus voltage U p ; when U p When the voltage is lower than the set voltage threshold, it is determined to be a low voltage operating condition. Under the low voltage operating condition, the fan reactive output is increased and the rectifier reactive consumption is reduced; wherein the adjusted fan reactive output does not exceed the maximum output reactive power of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values ​​of the rectifier reactive consumption; when Up When the voltage is not lower than the set voltage threshold, it is determined to be an overvoltage condition. Under the overvoltage condition, the fan reactive absorption is increased and the rectifier reactive consumption is increased; wherein, the adjusted fan reactive absorption does not exceed the maximum reactive absorption of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values ​​of the rectifier reactive consumption.

[0205] The following examples of this application will be combined with specific simulation experiments to verify the feasibility and progress of the method proposed in this application.

[0206] Table 1 Simulation parameters

[0207]

[0208]

[0209] The following will verify the influence of transient characteristics of DC and wind power systems on bus voltage.

[0210] Based on the simulation data of a large-scale wind power DC transmission system, the influence of the transient characteristics of the DC system and wind power system on the bus voltage mentioned above is verified.

[0211] 1) Verification of the influence of transient characteristics of DC system on bus voltage.

[0212] Figures 12 to 14 Revealed U f and ΔQ dr with U p The association law: U p with U f Positively correlated with ΔQ dr The results are consistent with the theoretical analysis conclusions above. In addition, the simulation analysis shows that ΔQ dr U p The influence of U increases with the increase of its amplitude and the decrease of short-circuit ratio, and presents similar characteristics in the low voltage and overvoltage stages; f U p The influence of U f The decrease and increase of short-circuit ratio gradually weaken and finally stabilize. cr =4.5, U f =0.2pu when the sensitivity coefficient is 1.32, U f When ≥0.4pu, it is stable at 1.246.

[0213] 2) Verification of the influence of transient characteristics of wind power system on bus voltage.

[0214] like Figure 15 , where (ad) system presents bus voltage U under different voltage conditions pDynamic correlation characteristics with fan power. Figure 15 The simulation results of (a) and (b) are under low voltage conditions: P w The support of U p is weak and decreases with the increase of short-circuit ratio; while Q w is positively correlated with U p , and when Q w exceeds the critical value, overvoltage may be caused, and the influence degree of Q w is negatively correlated with short-circuit ratio. Figure 15 The simulation results of (c) and (d) are under overvoltage conditions: P w has similar influence on U p as under low voltage conditions, and will not be described again. With the change of the fan from outputting reactive power to absorbing reactive power, U p shows an accelerated downward trend, and the downward rate and amplitude are also negatively correlated with short-circuit ratio. Both conditions show that, compared with P w , Q w has more significant influence on U p .

[0215] Figure 16 (a) and (b) show the U p -Q w characteristic curves under low / overvoltage conditions when the active component is ignored. By comparing (b) and (d) of Figure 15 , it can be seen that this simplification will moderately enhance the influence of Q w on U p , which shows that appropriately reducing the active power output of wind power can improve the reactive power regulation capability to a certain extent.

[0216] From the above analysis, it can be seen that both the active and reactive power output by the fan can regulate the bus voltage, but the influence degree of both decreases with the increase of short-circuit ratio, and Q w plays a leading role. The simulation results are consistent with the theoretical analysis in the foregoing.

[0217] The embodiments of the present application aim at the problem of transient voltage instability of the sending end system caused by AC faults, consider different conditions, analyze the transient response characteristics of the DC and wind power systems and the influence law of related factors on transient voltage, quantitatively evaluate the reactive power regulation capability of the system, and propose an adaptive reactive power coordinated control strategy based on regulation space constraints. The following conclusions are drawn through simulation analysis:

[0218] 1) In terms of transient response characteristics and influence law on voltage, the mapping relationship between the related factors of the DC and wind power systems and the transient voltage of the sending end system is constructed, the influence law of each factor on transient low / overvoltage is revealed, and then it is determined that the reactive power consumed by the rectifier of the DC system and the reactive power output by the wind power system are the leading factors affecting the transient voltage.

[0219] 2) Regarding the quantification of reactive power regulation capabilities of DC and wind power systems, a method for calculating the extreme value of rectifier reactive power consumption was proposed, based on the dominant influence of DC current on rectifier reactive power consumption and taking into account its constraints. Furthermore, a method for calculating the extreme values ​​of wind turbine output and absorption reactive power was established, taking into account the risk of wind turbine overcurrent. Comparative analysis shows that the reactive power regulation capabilities of both DC and wind power systems are significantly stronger under overvoltage conditions than under low voltage conditions.

[0220] The embodiment of the present application also provides a device for quantitatively analyzing the voltage support capability of a wind power DC transmission system, such as Figure 17 As shown, the voltage support capability quantitative analysis device of the wind power DC transmission system includes:

[0221] The dominant factor determination module 1701 is configured to establish mapping relationships between relevant factors of the DC system and the wind power system and bus transient voltages, respectively, based on the dynamic response characteristics of the DC system and the wind power system, and determine the dominant factors of the DC system transient voltage and the wind power system transient voltage based on the mapping relationships; wherein the dynamic response characteristics include the dynamic response of the bus transient voltage during the fault phase and the recovery phase, the dominant factors of the DC system transient voltage include the reactive power consumption of the rectifier, and the dominant factors of the wind power system transient voltage include the reactive power output by the wind turbine generator.

[0222] The DC reactive power quantification module 1702 is configured to quantify the reactive power regulation capability of the DC system based on the rectifier reactive power consumption, including: determining a DC current adjustable range according to the rectifier firing angle constraint, the inverter turn-off angle constraint, the commutation angle constraint, and the DC current constraint, and calculating the maximum and minimum values ​​of the rectifier reactive power consumption based on the DC current range and the rectifier reactive power consumption calculation formula;

[0223] The wind power reactive power quantification module 1703 is configured to quantify the reactive power regulation capability of the wind power system based on the reactive power output by the wind turbine, including: calculating the maximum output reactive power and the maximum absorbed reactive power of the wind turbine based on the rotor current constraint, combined with the stator side power equation and the grid connection point voltage equation.

[0224] In some embodiments, the device further includes a collaborative control module, which is configured to determine an adaptive reactive collaborative control strategy based on the reactive regulation capability of the DC system and the reactive regulation capability of the wind power system; wherein the adaptive reactive collaborative control strategy includes: obtaining the real-time monitored AC bus voltage U p ; when U pWhen the voltage is lower than the set voltage threshold, it is determined as a low-voltage working condition, in which the fan reactive output is increased and the rectifier reactive consumption is reduced; wherein the adjusted fan reactive output does not exceed the maximum output reactive of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values of the rectifier reactive consumption; when U p When the voltage is not lower than the set voltage threshold, it is determined as an over-voltage working condition, in which the fan reactive absorption is increased and the rectifier reactive consumption is increased; wherein the adjusted fan reactive absorption does not exceed the maximum absorption reactive of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values of the rectifier reactive consumption.

[0225] Embodiments of the present application provide an electronic device. The electronic device can include a processor, a memory, wherein the processor and the memory can communicate; for example, the processor and the memory communicate through a communication bus.

[0226] The processor executes computer execution instructions stored in the memory, so that the processor executes the scheme in the above embodiments. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component.

[0227] The communication bus can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The system bus can be divided into an address bus, a data bus, a control bus, etc. The transceiver is used to realize the communication between the database access device and other computers (such as clients, read-write libraries and read-only libraries). The memory can include random access memory (RAM), and can also include non-volatile memory.

[0228] The electronic device provided by the embodiments of the present application can be a terminal device of the above embodiments.

[0229] The embodiment of the present application further provides a computer readable storage medium, which stores computer instructions, and when the computer instructions are executed on a computer, the computer executes the technical solution of the wind power DC outward transmission system voltage support capability quantitative analysis method.

[0230] The embodiment of the present application further provides a computer program product, which comprises a computer program stored in a computer readable storage medium, and at least one processor can read the computer program from the computer readable storage medium, and when the at least one processor executes the computer program, the technical solution of the wind power DC outward transmission system voltage support capability quantitative analysis method in the above embodiment can be implemented.

[0231] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other manners. For example, the above-described device embodiments are merely illustrative, and the division of modules can be different, for example, a plurality of modules can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the modules shown or discussed can be indirect coupling or communication connection through some interfaces, devices or modules, and can be electrical, mechanical or other forms.

[0232] The modules illustrated as separated components can or can not be physically separated, and the components illustrated as modules can or can not be physical units, that is, can be located in one place, or can be distributed on a plurality of network units. Part or all of the modules can be selected according to actual needs to implement the present embodiment scheme.

[0233] In addition, each functional module in each embodiment of the present application can be integrated in one processing unit, or each module can be physically present alone, or two or more modules can be integrated in one unit. The unit formed by the above modules can be realized in the form of hardware, or in the form of hardware plus software functional unit.

[0234] The integrated module realized in the form of software functional module can be stored in a computer readable storage medium. The software functional module stored in a storage medium comprises a plurality of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute part of the steps of the method of each embodiment of the present application.

[0235] It should be appreciated that the above processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in combination with the application can be directly embodied as hardware processor execution, or executed by a combination of hardware and software modules in the processor.

[0236] The memory can include a high-speed RAM memory, and can also include a non-volatile storage NVM, such as at least one disk memory, and can also be a U disk, a mobile hard disk, a read-only memory, a magnetic disk or an optical disk, etc.

[0237] The bus can be an industry standard architecture (ISA) bus, a peripheral component interconnect (PCI) bus, or an extended industry standard architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc.

[0238] The above storage medium can be realized by any type of volatile or non-volatile storage device or their combination, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk or optical disk. The storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0239] An exemplary storage medium is coupled to the processor, so that the processor can read information from the storage medium and can write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in an electronic control unit or a host device.

[0240] Those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by program instruction related hardware. The foregoing program can be stored in a computer readable storage medium. The program executes to perform the steps of the above-mentioned method embodiments; and the foregoing storage medium includes various storage media that can store program codes, such as ROM, RAM, magnetic disk or optical disk.

[0241] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for quantitatively analyzing the voltage support capability of a wind power DC transmission system, characterized in that: The method comprises: Based on the dynamic response characteristics of the DC system and the wind power system, mapping relationships between relevant factors of the DC system and the wind power system and bus transient voltage are established respectively, and based on the mapping relationships, the dominant factors of the DC system transient voltage and the dominant factors of the wind power system transient voltage are determined; wherein the dynamic response characteristics include the dynamic response of the bus transient voltage in the fault phase and the recovery phase, the dominant factor of the DC system transient voltage includes the reactive power consumption of the rectifier, and the dominant factor of the wind power system transient voltage includes the reactive power output by the wind turbine; quantifying the reactive power regulation capability of the DC system based on the reactive power consumption of the rectifier, including: determining a DC current adjustable range according to a rectifier trigger angle constraint, an inverter turn-off angle constraint, a commutation angle constraint, and a DC current constraint, and calculating a maximum value and a minimum value of the rectifier reactive power consumption based on the DC current range and a rectifier reactive power consumption calculation formula; The reactive power regulation capability of the wind power system is quantified based on the reactive power output by the wind turbine, including: calculating the maximum output reactive power and the maximum absorbed reactive power of the wind turbine based on the rotor current constraint, combined with the stator side power equation and the grid connection point voltage equation.

2. The method for quantitative analysis of voltage support capability of a wind power DC transmission system according to claim 1 is characterized in that: Based on the dynamic response characteristics of the DC system, the mapping relationship between the relevant factors of the DC system and the bus transient voltage is established in the following way: Determine the busbar transient voltage U p The basic expression is: Where U s Represents the equivalent power supply voltage of the sending-end AC system, X s P represents the equivalent reactance from the sending end AC system to the grid connection point. s and Q s Respectively represent the active power and reactive power output by the system; P s , Q s Finding the total differential yields: Where U p0 Indicates the initial value of bus transient voltage, P s0 , Q s0 Respectively represent the initial values ​​of the system output active and reactive power; Will U s Considered as a constant value, substituting formula (3) into formula (2), the bus transient voltage change is obtained as: ΔQ s =ΔQ dr +Q cr0 -Q cr (5) Where, ΔU p Indicates the change in AC bus voltage, ΔQ s Indicates the change in reactive power output by the system, Q cr Indicates the reactive power transmitted by the reactive compensation device on the rectifier side, Q cr0 Indicates the initial value of reactive power transmitted by the reactive compensation device on the rectifier side, ΔQ dr Indicates the change in DC reactive power; The bus transient voltage during the fault and recovery phases is determined by the following formula: Where, t n Indicates the fault start time, t f Indicates the fault end time, ΔU p1 The fault stage is represented by ΔQ s The free component of the action, ΔU p2 The recovery phase is represented by ΔQ s The free component generated by the action, U f represents the forced component of the voltage caused by the equivalent impedance of the fault point, t represents the time variable, U pN Indicates the rated voltage of the sending end bus; The short-circuit capacity of the sending-end system is determined by the following formula: Where S ac Indicates the short-circuit capacity of the sending end system, U sN Indicates the rated voltage of the DC system, S cr Indicates short-circuit ratio, P dN Indicates the rated power of the DC system; Substituting Equation (5) into Equation (4) yields the following equation about ΔU: p The equation of ΔU is obtained by further solving the equation and combining it with equation (8). p The expression is as follows: Where Q c0 Indicates the rated reactive capacity of the parallel reactive compensation device before a fault or during steady-state operation; Substituting equation (9) into equation (7), we can obtain the mapping relationship between the relevant factors of the DC system and the bus transient voltage:

3. The method for quantitative analysis of voltage support capability of a wind power DC transmission system according to claim 1, characterized in that: Based on the dynamic response characteristics of the wind power system, the mapping relationship between the relevant factors of the wind power system and the bus transient voltage is established in the following way: The relationship between wind turbine power and bus transient voltage during the operation of the wind power system is expressed as: In the formula, A represents the first calculation coefficient, B represents the second calculation coefficient, C represents the third calculation coefficient, D represents the fourth calculation coefficient, and U pN Indicates the rated voltage of the sending end bus, X m Indicates the equivalent reactance between the AC system and the busbar, U m Indicates the equivalent voltage of the equivalent synchronous unit, R m Indicates the equivalent resistance between the AC system and the busbar, P w Indicates the active power output by the wind turbine, Q dc Represents the reactive power of the DC system, P dc Indicates the active power of the DC system, Q w Indicates the reactive power output by the wind turbine; After ignoring the active power component of the wind turbine, the mapping relationship between the relevant factors of the wind power system and the bus transient voltage is obtained: Wherein, C′ represents the fifth calculation coefficient.

4. The method for quantitative analysis of voltage support capability of a wind power DC transmission system according to claim 1, characterized in that: The calculation formula for the rectifier reactive power consumption is: Where Q dr Represents the rectifier reactive power consumption, I dc Indicates DC current, N indicates the number of converters, U p represents the bus transient voltage, T1 represents the commutation ratio on the rectifier side, α1 represents the rectifier trigger angle, and X c1 Represents the rectifier commutating reactance.

5. The method for quantitative analysis of voltage support capability of a wind power DC transmission system according to claim 4 is characterized in that: The DC current adjustable range is determined based on the rectifier trigger angle constraint, inverter turn-off angle constraint, commutation angle constraint, and DC current constraint, including: The rectifier trigger angle constraint is used to constrain the lower limit of the rectifier trigger angle, wherein the expression of the rectifier trigger angle is: Where α represents the rectifier trigger angle, U dr Indicates the DC voltage on the rectifier side; The turn-off angle corresponding to the shortest reverse voltage action time to ensure the thyristor's recovery blocking ability is taken as the minimum turn-off angle γ min , with γ≥γ min As the inverter turn-off angle constraint, the calculation formula of the inverter turn-off angle is: Where, X c2 Indicates the inverter side commutation reactance, U i Indicates the inverter side commutation bus voltage, U di represents the DC voltage on the inverter side, and T2 represents the transformer ratio on the inverter side; The commutation angle constraint is that the commutation angle of the rectifier and inverter does not exceed the set commutation angle. The commutation angle of the rectifier and inverter is determined by the following formula: Where μ1 and μ2 represent the commutation angles of the rectifier and inverter respectively; Determine a maximum limit value and a minimum limit value of the DC current according to the rated DC current, and take the DC current being between the maximum limit value and the minimum limit value as a DC current constraint; The determined DC current adjustable range is expressed as: Where, I dcN Indicates the rated DC current, γ N Indicates the rated turn-off angle.

6. The method for quantitative analysis of voltage support capability of a wind power DC transmission system according to claim 1, characterized in that: Based on the rotor current constraint, combined with the stator-side power equation and the grid-connected voltage equation, the maximum output reactive power and the maximum absorbed reactive power of the wind turbine are calculated, including: Determine the stator side power equation, which is expressed as: Where U w Indicates the voltage at the wind power grid connection point, P G , Q G Indicates the active and reactive power output on the stator side, s indicates the slip rate, I sd , I sq Indicates the d and q axis components of the stator current, Q w Indicates the reactive power of the wind turbine; Based on the stator side power equation, combined with the wind turbine grid connection point voltage equation and stator flux equation, the rotor current component expression is determined as: Where, P w Indicates the active power of the wind turbine, I rd , I rq Indicates the d-axis and q-axis components of the rotor current, Q s Indicates the reactive power output by the system, L m Indicates the magnetizing inductance of the fan, L s represents the stator inductance of the wind turbine, ω s Indicates the fan stator angular frequency; according to Determine the rotor current constraint, expressed as: Where, I r Represents the rotor current, I rmax Indicates the maximum value of the rotor current; The maximum value of the stator reactive current under low voltage and overvoltage conditions is calculated based on the rotor current constraint: Where, I sqomax Indicates the maximum value of stator reactive current under low voltage conditions, I sqimax Indicates the maximum value of stator reactive current under overvoltage conditions; Substituting equation (23) into equation (21) yields the maximum expression of wind turbine output and absorbed reactive power: Where Q womax Indicates the maximum reactive power output of the fan, Q wimax Indicates the maximum reactive power absorbed by the fan.

7. The method for quantitatively analyzing the voltage support capability of a wind power direct current transmission system according to any one of claims 1 to 6, characterized in that: The method further comprises: Based on the reactive power regulation capability of the DC system and the reactive power regulation capability of the wind power system, an adaptive reactive power coordinated control strategy is determined; wherein the adaptive reactive power coordinated control strategy includes: Get the real-time monitored AC bus voltage U p ; When U p When the voltage is lower than the set voltage threshold, it is determined to be a low voltage operating condition. Under the low voltage operating condition, the fan reactive output is increased and the rectifier reactive consumption is reduced; wherein the adjusted fan reactive output does not exceed the maximum output reactive power of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values ​​of the rectifier reactive consumption; When U p When the voltage is not lower than the set voltage threshold, it is determined to be an overvoltage condition. Under the overvoltage condition, the fan reactive absorption is increased and the rectifier reactive consumption is increased; wherein, the adjusted fan reactive absorption does not exceed the maximum reactive absorption of the fan, and the adjusted rectifier reactive consumption is between the maximum and minimum values ​​of the rectifier reactive consumption.

8. A device for quantitatively analyzing the voltage support capability of a wind power DC transmission system, characterized in that: The device comprises: a dominant factor determination module configured to establish mapping relationships between relevant factors of the DC system and the wind power system and bus transient voltages, respectively, based on the dynamic response characteristics of the DC system and the wind power system, and determine dominant factors of the DC system transient voltage and dominant factors of the wind power system transient voltage based on the mapping relationships; wherein the dynamic response characteristics include the dynamic response of the bus transient voltage during the fault phase and the recovery phase, the dominant factor of the DC system transient voltage includes the reactive power consumption of the rectifier, and the dominant factor of the wind power system transient voltage includes the reactive power output by the wind turbine; a DC reactive power quantification module configured to quantify the reactive power regulation capability of the DC system based on the reactive power consumption of the rectifier, including: determining a DC current adjustable range according to the rectifier trigger angle constraint, the inverter turn-off angle constraint, the commutation angle constraint, and the DC current constraint, and calculating the maximum and minimum values ​​of the rectifier reactive power consumption based on the DC current range and the rectifier reactive power consumption calculation formula; The wind power reactive power quantification module is configured to quantify the reactive power regulation capability of the wind power system based on the reactive power output by the wind turbine, including: calculating the maximum output reactive power and the maximum absorbed reactive power of the wind turbine based on the rotor current constraint, combined with the stator side power equation and the grid connection point voltage equation.

9. An electronic device, characterized in that: include: a processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method for quantitatively analyzing the voltage support capability of a wind power direct current transmission system according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method for quantitatively analyzing the voltage support capability of a wind power direct current transmission system according to any one of claims 1 to 7.

Images