Flexible direct current transmission frequency support control method and system, storage medium and equipment

Abstract

The invention discloses a flexible direct current transmission frequency support control method and system, a storage medium and equipment, and belongs to the field of safety and stability of alternating current and direct current series-parallel large power grids. The control method comprises the following steps: detecting the frequency, frequency change rate and DC voltage actual value of a power grid; determining a self-adaptive frequency droop coefficient of the flexible direct-current power transmission system according to the frequency, and determining a direct-current voltage self-adaptive droop coefficient according to the frequency and the frequency change rate; according to the self-adaptive frequency droop coefficient and the self-adaptive voltage droop coefficient, self-adaptive parameters of frequency droop and self-adaptive parameters of direct-current voltage droop are determined respectively, and an actual droop coefficient is obtained; according to the frequency, the direct current voltage actual value and the actual droop coefficient, a double-droop control strategy for the flexible direct current power transmission system is obtained, and the flexible direct current power transmission system is adjusted to send out active power; therefore, the frequency supporting force for a sending end system can be increased, the frequency change rate and the maximum frequency deviation are reduced, and the frequency safety of a power grid is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of safety and stability of large AC / DC hybrid power grids, and specifically relates to a flexible DC transmission frequency support control method, system, storage medium and equipment. Background Art

[0002] With the gradual development and maturity of power electronics technology, flexible direct current transmission has become a good solution due to its advantages such as active and reactive decoupling, strong controllability, no need for reactive compensation, and small footprint. However, the use of large-capacity new energy at the sending end will reduce the inertia level of the power grid, which will cause frequency fluctuations in the sending-end power grid when it is subject to power disturbances, affecting the frequency stability of the system. Therefore, studying the method of supporting frequency stability of flexible direct current transmission systems has important theoretical and application value for ensuring the safe and stable operation of the power grid.

[0003] At present, droop control is usually used to enable flexible DC transmission systems to participate in frequency support. However, with the gradual increase in DC transmission capacity and new energy penetration, the traditional fixed droop coefficient control is difficult to give full play to the frequency support capability of the flexible DC transmission system for frequency stability issues. There is also a lack of research on the inertial support capability of the flexible DC system. Although the existing double droop control takes into account the influence of inertia, it is still insufficient to explore the inertial support and primary frequency regulation capabilities of the flexible DC transmission system. Furthermore, there is still a lack of sufficient research on the influence of two key quantities, frequency deviation and frequency change rate, on the selection of frequency droop coefficient and DC voltage droop coefficient. Therefore, a flexible DC transmission frequency support control method is proposed. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a flexible direct current transmission frequency support control method, system, storage medium and device to solve the problems in the prior art.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a method for controlling frequency support of flexible direct current transmission, comprising the following steps:

[0007] Detect the frequency f, frequency change rate df / dt and actual value U of the DC voltage of the power grid dc ;

[0008] Determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ;

[0009] According to the adaptive frequency droop coefficient K fand adaptive voltage droop coefficient K v , respectively determining an adaptive parameter of the frequency droop and an adaptive parameter of the DC voltage droop, and obtaining an actual frequency droop coefficient and an actual voltage droop coefficient based on the adaptive parameter of the frequency droop and the adaptive parameter of the DC voltage droop;

[0010] According to the frequency f, the actual value of DC voltage U dc , actual frequency droop coefficient and actual voltage droop coefficient, and obtain the dual droop control strategy for the flexible DC transmission system to adjust the active power delivered by the flexible DC transmission system.

[0011] Furthermore, the frequency droop coefficient K f The expression is:

[0012]

[0013] Among them, K, N 0 , r, b are adaptive parameters of frequency droop, f 0 is the system frequency reference value, and Δf is the dead zone.

[0014] Furthermore, the DC voltage adaptive droop coefficient K v The expression is:

[0015]

[0016] Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dcref represents the DC voltage reference value, and P is the actual value of the active power delivered by the sending system.

[0017] Furthermore, H s The expression is:

[0018]

[0019] Among them, H 0 is the virtual inertia coefficient reference value, m and n are the adaptive parameters of DC voltage droop.

[0020] Furthermore, the determination expression of the adaptive parameter value of the frequency droop is:

[0021]

[0022] In the formula, K fmin is the minimum frequency droop coefficient, K fmax is the highest frequency droop coefficient, Δf minis the critical point of minimum frequency deviation, Δf max is the critical point of maximum frequency deviation.

[0023] Furthermore, the adaptive parameter determination expression of the DC voltage droop is:

[0024]

[0025] In the formula, H min is the minimum value of virtual inertia coefficient, H max is the maximum value of the virtual inertia coefficient, a is the artificially set critical coefficient, df max is the critical frequency change rate.

[0026] Furthermore, the expression for adjusting the active power delivered by the flexible DC transmission system is:

[0027] P=P ref +ΔP VSC

[0028]

[0029] Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system.

[0030] In a second aspect, an embodiment of the present invention provides a flexible direct current transmission frequency support control system, including:

[0031] Parameter detection module: detects the frequency f of the power grid, the frequency change rate df / dt and the actual value of the DC voltage U dc ;

[0032] Droop coefficient determination module: Determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ;

[0033] Adaptive parameter calculation module: According to the adaptive frequency droop coefficient K f and adaptive voltage droop coefficient K v , respectively determining an adaptive parameter of the frequency droop and an adaptive parameter of the DC voltage droop, and obtaining an actual frequency droop coefficient and an actual voltage droop coefficient based on the adaptive parameter of the frequency droop and the adaptive parameter of the DC voltage droop;

[0034] And, the control module: according to the frequency f, the actual value of the DC voltage U dc, actual frequency droop coefficient and actual voltage droop coefficient, and obtain the dual droop control strategy for the flexible DC transmission system to adjust the active power delivered by the flexible DC transmission system.

[0035] Furthermore, the frequency droop coefficient K f The expression is:

[0036]

[0037] Among them, K, N 0 , r, b are adaptive parameters of frequency droop, f 0 is the system frequency reference value, and Δf is the dead zone.

[0038] Furthermore, the DC voltage adaptive droop coefficient K v The expression is:

[0039]

[0040] Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dcref represents the DC voltage reference value, and P is the actual value of the active power delivered by the sending system.

[0041] Furthermore, H s The expression is:

[0042]

[0043] Among them, H 0 is the virtual inertia coefficient reference value, m and n are the adaptive parameters of DC voltage droop.

[0044] Furthermore, the determination expression of the adaptive parameter value of the frequency droop is:

[0045]

[0046] In the formula, K fmin is the minimum frequency droop coefficient, K fmax is the highest frequency droop coefficient, Δf min is the critical point of minimum frequency deviation, Δf max is the critical point of maximum frequency deviation.

[0047] Furthermore, the adaptive parameter determination expression of the DC voltage droop is:

[0048]

[0049] In the formula, Hmin is the minimum value of virtual inertia coefficient, H max is the maximum value of the virtual inertia coefficient, a is the artificially set critical coefficient, df max is the critical frequency change rate.

[0050] Furthermore, the expression for adjusting the active power delivered by the flexible DC transmission system is:

[0051] P=P ref +ΔP VSC

[0052]

[0053] Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system.

[0054] In a third aspect, an embodiment of the present invention provides a computer storage medium storing a readable program, which can execute the above-mentioned flexible direct current transmission frequency support control method when the program is running.

[0055] In a fourth aspect, an embodiment of the present invention provides an electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0056] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the above-mentioned flexible direct current transmission frequency support control method.

[0057] Beneficial effects of the present invention:

[0058] The present invention proposes an improved frequency control strategy for the sending-end converter station of the flexible DC transmission system, which dynamically changes the frequency droop coefficient and the DC voltage droop coefficient by an adaptive method, thereby realizing reasonable adjustment of the active power sent by the flexible DC transmission system; thereby increasing the frequency support for the sending-end system, effectively reducing the frequency change rate and the maximum frequency deviation, and ensuring the frequency safety of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0060] Figure 1is a flow chart of the control method of the present invention;

[0061] Figure 2 It is a simulation structure diagram of the present invention;

[0062] Figure 3 is a control block diagram of the present invention;

[0063] Figure 4 A comparison diagram of the frequency change curves of the present invention and the traditional method after a sudden increase in active load;

[0064] Figure 5 A comparison diagram of the active power curve of direct current transmission of the present invention after a sudden increase in active load and that of the traditional method;

[0065] Figure 6 A comparison diagram of frequency change curves of the present invention and the traditional method after a sudden drop in active load;

[0066] Figure 7 The figure is a comparison diagram of the active power curve of direct current transmission of the present invention after a sudden drop in active load and that of the traditional method. DETAILED DESCRIPTION

[0067] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] Example 1

[0069] like Figure 1 As shown, a flexible direct current transmission frequency support control method comprises the following steps:

[0070] S1, detect the frequency f, frequency change rate df / dt and actual value of DC voltage U of the power grid dc ;

[0071] Use a collection unit or measuring instrument to measure the frequency f and the actual value U of the DC voltage in the power grid dc , differentiate the frequency and get the frequency change rate df / dt.

[0072] S2, determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ;

[0073] Frequency droop coefficient K f The expression is as follows:

[0074]

[0075] Among them, K, N 0 , r, b are adaptive parameters of frequency droop, f 0 is the system frequency reference value, and Δf is the dead zone.

[0076] DC voltage droop coefficient K v The expression is as follows:

[0077]

[0078] Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dcref represents the DC voltage reference value, P is the actual value of the active power sent by the sending end system, H s The expression is as follows

[0079]

[0080] Among them, H 0 represents the reference value of the virtual inertia coefficient, m and n are the adaptive parameters of the DC voltage droop, and df / dt is the frequency change rate of the power grid.

[0081] S3, according to the adaptive frequency droop coefficient K in S2 f Determine the adaptive parameters of frequency droop, according to the adaptive voltage droop coefficient K v Determine the adaptive parameters of DC voltage droop, and obtain the actual frequency droop coefficient and the actual voltage droop coefficient;

[0082] The method for determining the adaptive parameter value of frequency droop is as follows:

[0083] According to the normal allowable frequency deviation of the power system and the national standard GB / T 40595-2021, the coefficient b is taken as Δf. The value of frequency K is determined according to the actual system to ensure that the frequency deviation is less than Δf. min When the droop coefficient is less than K fmin , the frequency deviation is greater than Δf max When the droop coefficient is greater than K fmax , respectively set Δf min , K fmin , Δf max , K fmax , the relationship is as follows:

[0084]

[0085] In the formula, Kfmin is the minimum frequency droop coefficient, K fmax is the highest frequency droop coefficient, Δf min is the critical point of minimum frequency deviation, Δf max is the critical point of maximum frequency deviation; wherein, b can be set voluntarily, and in this embodiment, b takes the dead zone Δf.

[0086] The adaptive parameter value of DC voltage droop is determined as follows:

[0087] The minimum virtual inertia coefficient H when α is not considered min =H 0 -n, maximum virtual inertia coefficient H max =H 0 , df / dt=df max When H s >aH max , respectively set H max , H min 、df max , a, we can get the following formula:

[0088]

[0089] In the formula, H 0 is the virtual inertia coefficient reference value, m and n are the adaptive parameters of DC voltage droop, H min is the minimum value of virtual inertia coefficient, H max is the maximum value of the virtual inertia coefficient, a is the artificially set critical coefficient, df max is the critical frequency change rate.

[0090] S4, according to the frequency deviation, the DC voltage deviation, the actual frequency droop coefficient and the actual voltage droop coefficient, a dual droop control strategy for the flexible DC transmission system is obtained to adjust the active power delivered by the flexible DC transmission system.

[0091] The expression for adjusting the active power delivered by the flexible DC transmission system is:

[0092] P=P ref +ΔP VSC

[0093] Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system. When the frequency rises, the active power transmitted is reduced to provide support. When the frequency rises, the active power transmitted is increased to provide support. ΔP VSC The expression is as follows:

[0094]

[0095] Among them, U dc is the actual value of DC voltage, U dcref is the DC voltage reference value.

[0096] Based on similar inventive concepts, an embodiment of the present invention further provides a computer storage medium storing a readable program, which can execute any of the above-mentioned flexible direct current transmission frequency support control methods when the program is running.

[0097] Based on similar inventive concepts, an embodiment of the present invention provides an electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0098] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to any of the above-mentioned flexible direct current transmission frequency support control methods.

[0099] Example 2

[0100] In order to fully tap the frequency regulation capability of the flexible DC transmission system and give full play to the flexible regulation of the converter station of the sending end system, the VSC converter station can adaptively adjust the frequency droop coefficient and DC voltage droop coefficient according to the frequency deviation and frequency change rate, thereby increasing the frequency support for the power grid. This embodiment provides a flexible DC transmission frequency response control method and system.

[0101] like Figure 2 As shown, this embodiment is based on the new energy transmission system through the flexible DC transmission system at both ends, AC1 and AC2 represent the sending end AC system and the receiving end AC system respectively, VSC1 and VSC2 represent the sending end converter station and the receiving end converter station respectively, P 1 and P 2 They represent the active power injected into the flexible DC system at both ends, L 1 and L 2 Respectively represent the active power load at both ends, SG represents the synchronous generator, DFIG represents the wind turbine generator, and GRID represents the receiving end system grid. The main parameters of this embodiment are set as follows: the capacity of the synchronous generator is 600MW, the capacity of the wind turbine generator is 500MW, the active power of the flexible DC transmission system is 900MW, the rated DC voltage is ±320kV, K=10, b=0.1, N 0 =20, r=16, H 0 =3, n=1, m=1.

[0102] like Figure 3 As shown, in the control block diagram of this embodiment, u s and i srepresents AC voltage and AC current, R and L represent the equivalent impedance of the converter station, Q and Q ref are the actual value and reference value of reactive power respectively, θ represents the phase-locked loop angle, and the quantity with * represents the reference value. The signal is sampled from the PCC end, and the d-axis and q-axis components of the current and voltage are obtained after dq transformation. After passing through the current inner loop, the d-axis and q-axis voltage reference values ​​are output, and then the signal control of PWM is carried out after dq inverse transformation.

[0103] The method adopted in this embodiment includes the following steps:

[0104] Step 1: Detect the frequency, frequency change rate and DC voltage of the power grid;

[0105] Step 2: Determine the adaptive frequency droop coefficient K of the flexible DC transmission system based on the frequency and frequency change rate f And DC voltage adaptive droop coefficient K v ;

[0106] Frequency droop coefficient K f The expression is as follows:

[0107]

[0108] Among them, K, N 0 , r, b are the adaptive parameters of frequency droop, f is the actual value of system frequency, f 0 is the system frequency reference value, usually 50, and Δf is 0.1.

[0109] DC voltage adaptive droop coefficient K v The expression is as follows:

[0110]

[0111] Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dc0 represents the rated operating voltage in the converter station of the flexible DC transmission system, P is the actual value of the active power sent by the sending end system, and H s The expression is as follows

[0112]

[0113] Among them, H 0 is the virtual inertia coefficient reference value, m and n are the adaptive parameters of DC voltage droop, and df / dt is the frequency change rate of the power grid.

[0114] Step 3: Determine the adaptive parameters according to the adaptive frequency droop coefficient and the DC voltage adaptive droop coefficient expressions in step 2 to obtain the actual droop coefficient;

[0115] The adaptive parameters of the adaptive frequency droop coefficient of the flexible DC transmission system are determined as follows: according to the normal allowable frequency deviation of the power system and relevant national standards, the coefficient b is taken as 0.1, and the value of K is determined according to the actual system. When the frequency deviation is less than 0.1Hz, the droop coefficient is less than 0.5, and when the frequency deviation is greater than 0.4Hz, the droop coefficient is greater than 9.5. The relationship is as follows:

[0116]

[0117] The adaptive parameters of the adaptive DC voltage droop coefficient are determined as follows: When α is not considered, the minimum virtual inertia coefficient H min =H 0 -n, maximum virtual inertia coefficient H max =H 0 , df / dt=1, H s >0.8H max , H max =3,H min =1, we can get the following formula:

[0118]

[0119] Step 4: According to the frequency f, the actual value of DC voltage U dc The dual droop control strategy for the flexible DC transmission system is obtained by using the actual droop coefficient to adjust the transmission power.

[0120] Specifically, the following expression is used to adjust the active power delivered by the flexible DC transmission system:

[0121] P=P ref +ΔP VSC

[0122] Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system. When the frequency rises, the active power transmitted is reduced to provide support. When the frequency rises, the active power transmitted is increased to provide support. ΔP VSC The expression is as follows:

[0123]

[0124] Among them, U dc is the actual value of DC voltage, U dcref is the DC voltage reference value.

[0125] It is set that a load surge of 50MW occurs at t=5s. Figure 4 and Figure 5 The results of the AC system frequency and the active power transmission of the flexible DC transmission system are shown respectively. It can be seen that when the AC system frequency drops, the flexible DC transmission system provides frequency support according to the adaptive double droop method proposed in the present invention. At the moment of frequency drop, the flexible DC transmission system immediately reduces the transmission of active power to support the grid frequency. Subsequently, the active power of the flexible DC transmission system recovers as the frequency deviation and frequency change rate decrease.

[0126] At the same time, a load sudden drop of 50MW is set to occur at t=5s. Figure 6 and Figure 7 The results of the AC system frequency and the active power transmission of the flexible DC transmission system are shown respectively. It can be seen that when the AC system frequency rises, the flexible DC transmission system provides frequency support according to the adaptive double droop method proposed in the present invention. At the moment of frequency rise, the flexible DC transmission system immediately increases the transmission of active power to support the grid frequency. Subsequently, the active power of the flexible DC transmission system recovers as the frequency deviation and frequency change rate decrease.

[0127] In summary, the flexible direct current transmission frequency response control method proposed in the present invention can improve the frequency support strength of the flexible direct current transmission system to the power grid and improve the frequency stability of the system. Specifically, an adaptive dual droop control method is proposed. First, the frequency adaptive droop and DC voltage adaptive droop coefficients are determined according to the frequency deviation and the frequency change rate. Then, the adaptive parameters are determined according to the expressions of the adaptive frequency droop coefficient and the DC voltage adaptive droop coefficient, and the adaptive dual droop coefficient is obtained. It increases with the increase of the frequency deviation and the frequency change rate, and approaches the maximum droop coefficient. Finally, the flexible direct current transmission system adjusts the transmitted active power according to the adaptive dual droop control, increases the frequency support strength to the power grid, reduces the frequency deviation and the frequency change rate, and improves the frequency stability of the power grid.

[0128] Example 3

[0129] In this embodiment, a flexible direct current transmission frequency support control system is provided, including:

[0130] Parameter detection module: detects the frequency f of the power grid, the frequency change rate df / dt and the actual value of the DC voltage U dc ;

[0131] Droop coefficient determination module: Determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ;

[0132] Adaptive parameter calculation module: According to the adaptive frequency droop coefficient K f and adaptive voltage droop coefficient K v , respectively determine the adaptive parameters of the frequency droop and the adaptive parameters of the DC voltage droop, and obtain the actual frequency droop coefficient and the actual voltage droop coefficient;

[0133] And, the control module: according to the frequency f, the actual value of the DC voltage U dc , actual frequency droop coefficient and actual voltage droop coefficient, and obtain the dual droop control strategy for the flexible DC transmission system to adjust the active power delivered by the flexible DC transmission system.

[0134] The frequency droop coefficient K f The expression is:

[0135]

[0136] Among them, K, N 0 , r, b are adaptive parameters of frequency droop, f 0 is the system frequency reference value, and Δf is the dead zone.

[0137] The DC voltage adaptive droop coefficient K v The expression is:

[0138]

[0139] Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dcref represents the DC voltage reference value, and P is the actual value of the active power delivered by the sending system.

[0140] H s The expression is:

[0141]

[0142] Among them, H 0 is the virtual inertia coefficient reference value, m and n are the adaptive parameters of DC voltage droop.

[0143] The determination expression of the adaptive parameter value of the frequency droop is:

[0144]

[0145] In the formula, K fmin is the minimum frequency droop coefficient, K fmax is the highest frequency droop coefficient, Δf minis the critical point of minimum frequency deviation, Δf max is the critical point of maximum frequency deviation.

[0146] The adaptive parameter determination expression of the DC voltage droop is:

[0147]

[0148] In the formula, H min is the minimum value of virtual inertia coefficient, H max is the maximum value of the virtual inertia coefficient, a is the artificially set critical coefficient, df max is the critical frequency change rate.

[0149] The expression for adjusting the active power delivered by the flexible DC transmission system is:

[0150] P=P ref +ΔP VSC

[0151]

[0152] Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system.

[0153] The method of the present invention may be implemented in hardware, firmware, or as software or computer code that may be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code that is originally stored in a remote recording medium or a non-temporary machine-readable medium downloaded over a network and will be stored in a local recording medium, so that the method described herein may be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that a computer, processor, microprocessor controller, or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code, and when the software or computer code is accessed and executed by a computer, processor, or hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0154] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for controlling frequency support of flexible direct current transmission, characterized in that: The following steps are involved: Detect the frequency f, frequency change rate df / dt and actual value of DC voltage U of the power grid dc ; Determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ; According to the adaptive frequency droop coefficient K f and adaptive voltage droop coefficient K v , respectively determining an adaptive parameter of the frequency droop and an adaptive parameter of the DC voltage droop, and obtaining an actual frequency droop coefficient and an actual voltage droop coefficient based on the adaptive parameter of the frequency droop and the adaptive parameter of the DC voltage droop; According to the frequency f, the actual value of DC voltage U dc , actual frequency droop coefficient and actual voltage droop coefficient, and obtain the dual droop control strategy for the flexible DC transmission system to adjust the active power delivered by the flexible DC transmission system.

2. The method for controlling frequency support of flexible direct current transmission according to claim 1, characterized in that: The frequency droop coefficient K f The expression is: Among them, K, N0, r, and b are adaptive parameters of frequency droop, f0 is the system frequency reference value, and Δf is the dead zone.

3. The method for controlling frequency support of flexible direct current transmission according to claim 2, characterized in that: The DC voltage adaptive droop coefficient K v The expression is: Among them, H s represents the virtual inertia coefficient of the converter station of the flexible DC transmission system, S VSC is the rated capacity of the converter station of the flexible DC transmission system, C is the equivalent DC capacitance value, U dcref represents the DC voltage reference value, and P is the actual value of the active power delivered by the sending system.

4. The method for controlling frequency support of flexible direct current transmission according to claim 3, characterized in that: H s The expression is: Among them, H0 is the virtual inertia coefficient reference value, and m and n are the adaptive parameters of DC voltage droop.

5. A flexible direct current transmission frequency support control method according to claim 4, characterized in that: The determination expression of the adaptive parameter of the frequency droop is: In the formula, K fmin is the minimum frequency droop coefficient, K fmax is the highest frequency droop coefficient, Δf min is the critical point of minimum frequency deviation, Δf max is the critical point of maximum frequency deviation.

6. The method for controlling frequency support of flexible direct current transmission according to claim 5, characterized in that: The adaptive parameter determination expression of the DC voltage droop is: In the formula, H min is the minimum value of the virtual inertia coefficient, H max is the maximum value of the virtual inertia coefficient, a is the artificially set critical coefficient, df max is the critical frequency change rate.

7. The method for controlling frequency support of flexible direct current transmission according to claim 3, characterized in that: The expression for adjusting the active power delivered by the flexible DC transmission system is: P=P ref +ΔP VSC Among them, P is the actual value of active power sent by the sending system, P ref is the actual active power reference value, ΔP VSC The change in active power that provides frequency support for the flexible DC transmission system.

8. A flexible direct current transmission frequency support control system, characterized in that: include: Parameter detection module: detects the frequency f of the power grid, the frequency change rate df / dt and the actual value of the DC voltage U dc ; Droop coefficient determination module: Determine the adaptive frequency droop coefficient K of the flexible DC transmission system according to the frequency f f , determine the DC voltage adaptive droop coefficient K according to the frequency f and the frequency change rate df / dt v ; Adaptive parameter calculation module: According to the adaptive frequency droop coefficient K f and adaptive voltage droop coefficient K v , respectively determining an adaptive parameter of the frequency droop and an adaptive parameter of the DC voltage droop, and obtaining an actual frequency droop coefficient and an actual voltage droop coefficient based on the adaptive parameter of the frequency droop and the adaptive parameter of the DC voltage droop; And, the control module: according to the frequency f, the actual value of the DC voltage U dc , actual frequency droop coefficient and actual voltage droop coefficient, and obtain the dual droop control strategy for the flexible DC transmission system to adjust the active power delivered by the flexible DC transmission system.

9. A computer storage medium storing a readable program, characterized in that: When the program is running, it can execute the flexible direct current transmission frequency support control method described in any one of claims 1 to 7.

10. An electronic device, characterized in that: include: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the flexible direct current transmission frequency support control method according to any one of claims 1 to 7.

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