An inertial support method, system and medium for a high voltage direct current transmission interconnection area

Abstract

The present invention discloses an inertial support method, system and medium for a high-voltage direct current transmission interconnection area, and relates to the technical field of power system stability and control; an inertial support link that considers the frequency of the power grids at the sending and receiving ends is added to the high-voltage direct current transmission constant current control link, which includes the inertial power calculation of the sending-end power grid, the inertial power calculation of the receiving-end power grid and the conversion of the inertial power into direct current, and adjusts the power of direct current transmission by changing the frequency of the sending and receiving ends, simulates the inertial response of the synchronous generator, and realizes the inertial mutual support of the high-voltage direct current transmission interconnection area. This scheme does not introduce the differential term of frequency, and therefore does not introduce high-frequency noise of frequency into the high-voltage direct current transmission control system, effectively avoiding the risk of oscillation of direct current transmission power and alternating current frequency caused by the introduction of the differential term of frequency in the traditional inertial support, and improving the stability of system operation; it provides an effective reference for the design and optimized operation of the inertial support in the high-voltage direct current transmission interconnection area.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability and control, and in particular to an inertial support method, system and medium for a high-voltage direct current transmission interconnection area. Background Art

[0002] HVDC transmission has become the main mode of large-scale energy bases for long-distance transmission due to its advantages of large transmission capacity, long distance and high efficiency. In addition, DC transmission can asynchronously connect two power grids, which can solve stability problems such as power angle instability and voltage collapse caused by large-scale power flow transfer after AC / DC parallel power grid failure. Therefore, my country's Yunnan Power Grid and Southwest Power Grid both use DC transmission to asynchronously interconnect with load centers. However, this DC asynchronous interconnection method will weaken the inertia of the system, weaken the frequency regulation ability of the system, and bring severe challenges to the frequency stability and control of the system. The power transmitted by DC transmission is controllable, and the adjustment time scale is milliseconds. Technically, it is possible to achieve power mutual assistance and inertial support in the interconnected area. However, the inertial support of the existing HVDC interconnected area must be differentiated with respect to frequency (df / dt), which may introduce high-frequency noise of frequency. If the parameter setting is not total, it may cause power oscillation or even DC lockout. Therefore, it is of great engineering significance to study the inertial support method of the HVDC interconnected area without considering the frequency differential term. Summary of the invention

[0003] The technical problem to be solved by the present invention is that the inertial support of the existing high-voltage direct current transmission interconnection area must differentiate the frequency, which may introduce high-frequency noise of the frequency, and may cause power oscillation or even DC lockout; the purpose of the present invention is to provide an inertial support method, system and medium for the high-voltage direct current transmission interconnection area, add an inertial support link that considers the frequency of the power grid at the sending and receiving ends in the high-voltage direct current transmission constant current control link, adjust the power of direct current transmission by changing the frequency of the sending and receiving ends, simulate the inertial response of the synchronous generator, and realize the inertial mutual support of the high-voltage direct current transmission interconnection area; do not introduce the differential term of the frequency, and will not introduce high-frequency noise of the frequency in the high-voltage direct current transmission control system, effectively avoid the risk of direct current transmission power and alternating current frequency oscillation caused by the introduction of the differential term of the frequency in the traditional inertial support, and improve the stability of the system operation.

[0004] The present invention is achieved through the following technical solutions:

[0005] This solution provides an inertial support method for a high-voltage direct current transmission interconnection area, including:

[0006] Obtaining the sending-end power grid frequency and the estimated value of the sending-end frequency, subtracting the sending-end power grid frequency from the estimated value of the sending-end frequency to obtain the sending-end power grid frequency difference, and calculating the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference;

[0007] Obtaining the receiving-end power grid frequency and the receiving-end frequency estimation value, subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value to obtain the receiving-end power grid frequency difference, and calculating the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference;

[0008] The actual inertia support additional power is obtained by adding the inertia support additional power of the sending-end power grid and the inertia support additional power of the receiving-end power grid, and the actual inertia support additional power is converted into an inertia support additional current command output.

[0009] Working principle of this scheme: the existing inertial supports in the interconnected areas of high-voltage direct current transmission all need to differentiate the frequency, which may introduce high-frequency noise of the frequency, and may cause power oscillation or even DC lockout; the present invention adds an inertial support link that considers the frequency of the power grids at the sending and receiving ends in the constant current control link of high-voltage direct current transmission, which includes the calculation of the inertial power of the sending and receiving power grids, the calculation of the inertial power of the receiving power grids, and the conversion of the inertial power into direct current, and adjusts the power of direct current transmission by changing the frequency of the sending and receiving ends, simulating the inertial response of the synchronous generator, and realizing the mutual inertial support of the interconnected areas of high-voltage direct current transmission. This scheme does not introduce the differential term of frequency, so it will not introduce high-frequency noise of frequency into the control system of high-voltage direct current transmission, effectively avoiding the risk of oscillation of direct current transmission power and alternating current frequency caused by the introduction of the differential term of frequency in the traditional inertial support, and improving the stability of system operation; it provides an effective reference for the design and optimized operation of the inertial support in the interconnected areas of high-voltage direct current transmission.

[0010] A further optimization scheme is that the additional power ΔP1 of the inertial support of the sending-end power grid is calculated according to the following formula:

[0011]

[0012] Where, ω0 represents the rated angular frequency, D1 is the damping coefficient at the sending end, X1 is the virtual impedance at the sending end, f1 is the grid frequency at the sending end, and f vir1 is the estimated value of the sending frequency.

[0013] A further optimization scheme is to estimate the sending frequency f vir1 Satisfy the following formula:

[0014]

[0015] Where H1 is the time constant of the inertial support at the sending end, f0 is the rated frequency of the power grid; ΔP1 represents the additional power of the inertial support of the power grid at the sending end.

[0016] A further optimization scheme is that the additional power ΔP2 supported by the inertial support of the receiving-end power grid is calculated according to the following formula:

[0017]

[0018] Where, ω0 represents the rated angular frequency, D2 is the receiving end damping coefficient, X2 is the receiving end virtual impedance, f2 is the receiving end grid frequency, and f vir2 is the estimated value of the receiving frequency.

[0019] A further optimization scheme is that the receiving end frequency estimation value f vir2 satisfy:

[0020]

[0021] Where H2 is the time constant of the receiving-end inertial support, f0 is the rated frequency of the power grid; ΔP2 represents the additional power of the receiving-end power grid inertial support.

[0022] A further optimization scheme is that the actual inertial support additional power is obtained by adding the inertial support additional power of the sending-end power grid and the inertial support additional power of the receiving-end power grid, including a method: the actual inertial support additional power ΔP is calculated according to the following formula: vir :

[0023] ΔP vir =ΔP1+(-ΔP2)=ΔP1-ΔP2;

[0024] Among them, ΔP1 represents the additional power supported by the inertia of the sending-end power grid, and ΔP2 represents the additional power supported by the inertia of the receiving-end power grid.

[0025] A further optimization scheme is that the actual inertial support additional power is converted into an inertial support additional current command output, including the method:

[0026] The inertial support additional current ΔI is calculated according to the following formula vir :

[0027]

[0028] Where V dc Indicates the DC voltage at the sending end;

[0029] Use inertia to support additional current ΔI vir To correct the actual current reference value of DC transmission.

[0030] A further optimization scheme is that the additional current ΔI is supported by inertia vir To correct the actual current reference value of direct current transmission, including methods:

[0031] The original current reference value I of high-voltage direct current transmission is ord With inertial support additional current ΔI vir Add together to get the actual current reference value I of the DC current ref .

[0032] This solution provides an inertial support system for a high-voltage direct current transmission interconnection area, which is used to implement the above-mentioned inertial support method for a high-voltage direct current transmission interconnection area. The system includes:

[0033] A first calculation module is used to obtain a sending-end power grid frequency and a sending-end frequency estimation value, to obtain a sending-end power grid frequency difference by subtracting the sending-end power grid frequency from the sending-end frequency estimation value, and to calculate the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference;

[0034] The second calculation module is used to obtain the receiving-end power grid frequency and the receiving-end frequency estimation value, to obtain the receiving-end power grid frequency difference by subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value, and to calculate the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference;

[0035] The output module is used to obtain the actual inertia support additional power based on the addition of the inertia support additional power of the sending-end power grid and the inertia support additional power of the receiving-end power grid, and convert the actual inertia support additional power into an inertia support additional current command output.

[0036] The present solution also provides a computer-readable medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement an inertial support method for a high-voltage direct current transmission interconnection area as described above.

[0037] When the system operates normally, the sending-end frequency estimate tracks the sending-end grid frequency, and the receiving-end frequency estimate tracks the receiving-end grid frequency. At this time, the inertial support additional power at the sending and receiving ends is zero, and the inertial support additional current command is also zero, that is, the high-voltage direct current transmission interconnection area does not provide inertial support during normal operation.

[0038] When the system is disturbed, the frequency difference deviates. Due to the hysteresis of the control, the frequency estimation value lags behind the grid frequency. At this time, the frequency difference of the sending-end grid or the receiving-end grid is not zero. The frequency difference obtains the required inertial support additional power through the inertial support link of the sending-end grid or the receiving-end grid, and then adjusts the power transmitted by the high-voltage direct current transmission to realize the inertial support of the high-voltage direct current transmission interconnection area; the frequency estimation link calculates the new sending-end frequency estimation value based on the obtained sending-end inertial support power, and calculates the new receiving-end frequency estimation value based on the obtained receiving-end inertial support power. When the system enters a new steady state, the sending-end frequency estimation value will be equal to the sending-end grid frequency again, the receiving-end frequency estimation value will be equal to the receiving-end grid frequency again, the inertial support additional power is zero, and the inertial support of the high-voltage direct current transmission interconnection area ends.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] The present invention provides an inertial support method for a high-voltage direct current transmission interconnection area; an inertial support link that considers the frequency of the power grids at the sending and receiving ends is added to the high-voltage direct current transmission constant current control link, which includes the inertial power calculation of the sending-end power grid, the inertial power calculation of the receiving-end power grid, and the conversion of the inertial power into direct current, and adjusts the power of direct current transmission by changing the frequency of the sending and receiving ends, simulating the inertial response of the synchronous generator, and realizing the inertial mutual support of the high-voltage direct current transmission interconnection area. This scheme does not introduce the differential term of frequency, and therefore does not introduce high-frequency noise of frequency into the high-voltage direct current transmission control system, effectively avoiding the risk of oscillation of direct current transmission power and alternating current frequency caused by the introduction of the differential term of frequency in the traditional inertial support, and improving the stability of the system operation; it provides an effective reference for the design and optimized operation of the inertial support in the high-voltage direct current transmission interconnection area. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0042] Figure 1 It is a flow chart of the inertial support method for the HVDC interconnection area;

[0043] Figure 2 This is a schematic diagram of the inertial support control system principle;

[0044] Figure 3 Schematic diagram of a four-machine and two-region transmission system interconnected by high-voltage direct current transmission;

[0045] Figure 4 It is a schematic diagram of the sending-end power grid frequency when the sending-end frequency is reduced;

[0046] Figure 5 It is a schematic diagram of the frequency change rate of the sending-end power grid when the sending-end frequency decreases;

[0047] Figure 6 This is a schematic diagram of the receiving-end power grid frequency when the sending-end frequency is reduced;

[0048] Figure 7 It is a schematic diagram of the frequency change rate of the receiving-end power grid when the sending-end frequency decreases;

[0049] Figure 8 It is a schematic diagram of HVDC transmission power when the sending end frequency is reduced;

[0050] Fig. 9 This is a schematic diagram of the power grid frequency at the sending end when the frequency at the receiving end increases;

[0051] Fig.10 This is a schematic diagram of the network frequency change rate when the receiving end frequency increases;

[0052] Fig.11 This is a schematic diagram of the receiving-end power grid frequency when the receiving-end frequency increases;

[0053] Fig.12 It is a schematic diagram of the frequency change rate of the receiving-end power grid when the receiving-end frequency increases;

[0054] Fig.13 Schematic diagram of power transmission of high-voltage DC power when the frequency at the receiving end increases. DETAILED DESCRIPTION

[0055] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0056] Example 1

[0057] This embodiment provides an inertial support method for a high-voltage direct current transmission interconnection area, such as Figure 1 As shown, including:

[0058] Obtaining the sending-end power grid frequency and the estimated value of the sending-end frequency, subtracting the sending-end power grid frequency from the estimated value of the sending-end frequency to obtain the sending-end power grid frequency difference, and calculating the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference;

[0059] The additional power ΔP1 of the inertial support of the sending-end power grid is calculated according to the following formula:

[0060]

[0061] Where, ω0 represents the rated angular frequency, D1 is the damping coefficient at the sending end, X1 is the virtual impedance at the sending end, f1 is the grid frequency at the sending end, and f vir1 is the estimated value of the sending frequency.

[0062] Estimated value of sending frequency f vir1 Satisfy the following formula:

[0063]

[0064] Where H1 is the time constant of the inertial support at the sending end, f0 is the rated frequency of the power grid; ΔP1 represents the additional power of the inertial support of the power grid at the sending end.

[0065] Obtaining the receiving-end power grid frequency and the receiving-end frequency estimation value, subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value to obtain the receiving-end power grid frequency difference, and calculating the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference;

[0066] The additional power ΔP2 supported by the receiving-end grid inertia is calculated according to the following formula:

[0067]

[0068] Where, ω0 represents the rated angular frequency, D2 is the receiving end damping coefficient, X2 is the receiving end virtual impedance, f2 is the receiving end grid frequency, and f vir2 is the estimated value of the receiving frequency.

[0069] Estimated value of receiving frequency f vir2 satisfy:

[0070]

[0071] Where H2 is the time constant of the receiving-end inertial support, f0 is the rated frequency of the power grid; ΔP2 represents the additional power of the receiving-end power grid inertial support.

[0072] The actual inertia support additional power is obtained by adding the inertia support additional power of the sending-end power grid and the inertia support additional power of the receiving-end power grid, and the actual inertia support additional power is converted into an inertia support additional current command output.

[0073] The method of obtaining the actual inertial support additional power by adding the inertial support additional power of the sending-end power grid and the inertial support additional power of the receiving-end power grid includes: calculating the actual inertial support additional power ΔP according to the following formula: vir :

[0074] ΔP vir =ΔP1+(-ΔP2)=ΔP1-ΔP2;

[0075] Among them, ΔP1 represents the additional power supported by the inertia of the sending-end power grid, and ΔP2 represents the additional power supported by the inertia of the receiving-end power grid.

[0076] The method of converting the actual inertial support additional power into the inertial support additional current command output includes:

[0077] The inertial support additional current ΔI is calculated according to the following formula vir :

[0078]

[0079] Where V dc Indicates the DC voltage at the sending end;

[0080] Use inertia to support additional current ΔI vir To correct the actual current reference value of DC transmission.

[0081] The additional current ΔI is supported by inertia vir To correct the actual current reference value of direct current transmission, including methods:

[0082] The original current reference value I of high-voltage direct current transmission is ord With inertial support additional current ΔI vir Add together to get the actual current reference value I of the DC current ref . Figure 2 Where β is the trigger angle advance angle, and α is the trigger angle.

[0083] Example 2

[0084] This solution provides an inertial support system for a high-voltage direct current transmission interconnection area, which is used to implement an inertial support method for a high-voltage direct current transmission interconnection area in Example 1. The system includes:

[0085] A first calculation module is used to obtain a sending-end power grid frequency and a sending-end frequency estimation value, to obtain a sending-end power grid frequency difference by subtracting the sending-end power grid frequency from the sending-end frequency estimation value, and to calculate the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference;

[0086] The second calculation module is used to obtain the receiving-end power grid frequency and the receiving-end frequency estimation value, to obtain the receiving-end power grid frequency difference by subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value, and to calculate the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference;

[0087] The output module is used to obtain the actual inertia support additional power based on the addition of the inertia support additional power of the sending-end power grid and the inertia support additional power of the receiving-end power grid, and convert the actual inertia support additional power into an inertia support additional current command output.

[0088] like Figure 2 As shown, the inertial support control system consists of three parts: (1) the inertial support link of the sending-end power grid; (2) the inertial support link of the receiving-end power grid; (3) the power-to-current command link;

[0089] The inertial support link of the sending-end power grid includes two parts: inertial power calculation and frequency estimation.

[0090] The purpose of inertia power calculation is to obtain the frequency difference of the sending-end grid by subtracting the measured sending-end grid frequency from the estimated value of the sending-end frequency obtained in the frequency estimation link, and then calculate the additional power supported by the inertia of the sending-end grid based on the sending-end grid frequency difference.

[0091] The function of the frequency estimation link is to calculate the estimated value of the sending-end frequency based on the additional power supported by the inertia of the sending-end power grid.

[0092] The inertial response of the generator is used to resist the frequency change rate in the initial stage of the disturbance, and the additional power it outputs is proportional to the frequency change rate:

[0093]

[0094] Where ΔP g Inertial support power provided for generator inertia, H g is the inertia time constant of the generator, f is the frequency of the power grid, and f0 is the rated frequency of the power grid.

[0095] Analogous to the inertial response of the generator, the additional power of HVDC transmission to provide inertial support for the sending-end power grid by adjusting the DC transmission power is:

[0096]

[0097] Transforming the above formula can obtain the estimated value of the sending-end power grid frequency:

[0098]

[0099] Similar to the inertial support link of the sending-end power grid, the inertial support link of the receiving-end power grid also includes two parts: inertial power calculation and frequency estimation.

[0100] The purpose of inertia power calculation is to obtain the frequency difference of the receiving-end power grid by subtracting the measured receiving-end power grid frequency from the receiving-end frequency estimation value, and then calculate the additional power supported by the receiving-end power grid inertia based on the receiving-end power grid frequency difference.

[0101] The power-to-current command link adds the inertial support additional power of the sending-end power grid and the inertial support additional power of the receiving-end power grid to obtain the actual inertial support additional power, which is expressed as:

[0102] ΔP vir =ΔP1+(-ΔP2)=ΔP1-ΔP2

[0103] The actual inertial support additional power is divided by the DC voltage at the sending end to obtain the inertial support additional current command, which is expressed as:

[0104]

[0105] When the system is operating normally, the estimated value of the sending-end frequency tracks the sending-end grid frequency, and the estimated value of the receiving-end frequency tracks the receiving-end grid frequency. At this time, the inertial support additional power of the sending and receiving ends is zero, and the inertial support additional current command is also zero. The high-voltage direct current transmission transmits power according to the command value, that is, the high-voltage direct current transmission interconnection area does not provide inertial support during normal operation. When the system is disturbed, the frequency difference deviates. Due to the lag of control, the frequency estimate lags behind the grid frequency. At this time, the sending-end grid frequency difference or the receiving-end grid frequency difference is not zero. The frequency difference obtains the required inertial support additional power through the sending-end grid inertial support link or the receiving-end grid inertial support link, and then adjusts the power transmitted by the high-voltage direct current transmission to realize the inertial support of the high-voltage direct current transmission interconnection area; the frequency estimation link calculates the new sending-end frequency estimate value based on the obtained sending-end inertial support power, and calculates the new receiving-end frequency estimate value based on the obtained receiving-end inertial support power. When the system enters a new steady state, the estimated value of the sending-end frequency will be equal to the sending-end grid frequency again, the estimated value of the receiving-end frequency will be equal to the receiving-end grid frequency again, the inertial support additional power will be zero, and the inertial support of the high-voltage direct current transmission interconnection area will end.

[0106] Example 3

[0107] This embodiment provides a computer-readable medium having a computer program stored thereon. The computer program is executed by a processor to implement an inertial support method for a high-voltage direct current transmission interconnection area as described in Example 1.

[0108] In order to verify the accuracy of the inertial support method of the high-voltage direct current transmission interconnection area of ​​the embodiment, this embodiment builds the following Figure 3 The four-machine and two-region transmission system with HVDC interconnection is shown.

[0109] The sending-end power grid consists of two synchronous generators G1 and G2 and load PL1, and the receiving-end power grid consists of two synchronous generators G3 and G4 and load PL2, as shown in Table 1. The parameters of the four synchronous generators are the same; the main parameters of high-voltage direct current transmission are shown in Table 2; among which the control parameters are: H1 = H2 = 8s, ω0 = 1p.u., X1 = X2 = 0.02pu, D1 = D2 = 100p.u. The virtual inertia time constant of traditional virtual inertia is 8s.

[0110] Table 1 Main parameters of synchronous generator

[0111]

[0112] Table 2 Main parameters of HVDC transmission

[0113]

[0114] When the frequency at the sending end is reduced, the load of the sending end grid is 300MW, the load of the receiving end grid is 1200MW, and after 10 seconds, the sending end grid is put into 90MW load. Figure 4-Figure 8 As shown, the comparative simulation diagram of no inertial support, traditional inertial support and inertial support of this scheme when the sending-end power grid is put into 90MW load.

[0115] from Figure 4-Figure 8 It can be seen that under the control of HVDC transmission without inertial support, the power transmitted by HVDC transmission remains unchanged, does not respond to the frequency of the sending-end power grid, and the receiving-end power grid does not provide inertial support. The frequency deviation and frequency change rate of the sending end are both the largest; after HVDC transmission adopts traditional inertial support control, the power transmitted by HVDC transmission can respond to frequency changes, and the lowest point of the frequency and frequency change rate of the sending-end power grid are improved. However, due to the introduction of the differential term of frequency (df / dt), the control system of HVDC transmission introduces high-frequency noise of frequency, and the power transmitted by HVDC transmission oscillates, resulting in oscillations in the frequency and frequency change rate of the sending-end and receiving-end power grids; after HVDC transmission adopts the proposed inertial support, the power transmitted by HVDC transmission can also respond to frequency changes, and the lowest point of the frequency and frequency change rate of the sending-end power grid are also improved. Compared with the traditional inertial support control, the change trends of AC frequency and HVDC transmission power are basically the same, which shows that inertial support can provide inertial support between regions like traditional inertial support, and will not cause oscillation of HVDC transmission power and system frequency.

[0116] When the frequency at the receiving end increases: the load on the sending-end grid is 300MW, and the load on the receiving-end grid is 1290MW. After 10s, the receiving-end grid cuts off 90MW of load. Figure 9-13 It is a comparative simulation diagram of the inertial support without inertial support, the traditional inertial support and the inertial support of the present invention when the receiving-end power grid cuts off 90MW load.

[0117] from Figure 9-13 It can be seen that, similar to the load input at the sending end, the power transmitted by the HVDC transmission remains unchanged under the control of the HVDC transmission without inertial support, and does not respond to the frequency of the receiving end grid. The sending end grid does not provide inertial support, and the frequency deviation and frequency change rate of the receiving end are both the largest; after the HVDC transmission adopts the traditional inertial support control, although the sending end grid can provide inertial support to the receiving end grid, due to the introduction of the differential term of frequency (df / dt), the control system of the HVDC transmission introduces high-frequency noise of frequency, and the power transmission of the HVDC transmission oscillates, resulting in oscillations in the frequency and frequency change rate of the sending and receiving end grids; after the HVDC transmission adopts the proposed inertial support, the sending end grid can provide inertial support to the receiving end grid, and will not cause power oscillation and oscillation of the HVDC transmission external power.

[0118] It can be seen that the proposed inertial support method does not introduce the differential term of frequency, and will not introduce high-frequency noise of frequency into the HVDC transmission control system. It can realize the mutual inertial support of the interconnected area and improve the stability of system operation, which is of great significance to the frequency control of the HVDC interconnected power grid.

[0119] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An inertial support method for a high voltage direct current transmission interconnection area, characterized in that: include: Obtaining the sending-end power grid frequency and the estimated value of the sending-end frequency, subtracting the sending-end power grid frequency from the estimated value of the sending-end frequency to obtain the sending-end power grid frequency difference, and calculating the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference; Obtaining the receiving-end power grid frequency and the receiving-end frequency estimation value, subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value to obtain the receiving-end power grid frequency difference, and calculating the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference; Based on the addition of the inertial support additional power of the sending-end power grid and the negative inertial support additional power of the receiving-end power grid, the actual inertial support additional power is obtained, and the actual inertial support additional power is converted into an inertial support additional current command output; The additional power ΔP1 of the inertial support of the sending-end power grid is calculated according to the following formula: Where, ω0 represents the rated angular frequency, D1 is the damping coefficient at the sending end, X1 is the virtual impedance at the sending end, f1 is the grid frequency at the sending end, and f vir1 is the estimated value of the sending end frequency; Estimated value of sending frequency f vir1 Satisfy the following formula: Where H1 is the time constant of the inertial support at the sending end, f0 is the rated frequency of the power grid; ΔP1 represents the additional power of the inertial support of the power grid at the sending end; The additional power ΔP2 supported by the receiving-end power grid inertia is calculated according to the following formula: Where, ω0 represents the rated angular frequency, D2 is the receiving end damping coefficient, X2 is the receiving end virtual impedance, f2 is the receiving end grid frequency, and f vir2 is the estimated value of the receiving frequency; Estimated value of receiving frequency f vir2 satisfy: Where H2 is the time constant of the receiving-end inertial support, f0 is the rated frequency of the power grid; ΔP2 represents the additional power of the receiving-end power grid inertial support.

2. The inertial support method for a high-voltage direct current transmission interconnection area according to claim 1, characterized in that: The method of obtaining the actual inertial support additional power by adding the inertial support additional power of the sending-end power grid and the inertial support additional power of the receiving-end power grid includes: calculating the actual inertial support additional power ΔP according to the following formula: vir : ΔP vir =ΔP1+(-ΔP2)=ΔP1-ΔP2; Among them, ΔP1 represents the additional power supported by the inertia of the sending-end power grid, and ΔP2 represents the additional power supported by the inertia of the receiving-end power grid.

3. The inertial support method for a high-voltage direct current transmission interconnection area according to claim 2, characterized in that: The method of converting the actual inertial support additional power into the inertial support additional current command output includes: The inertial support additional current ΔI is calculated according to the following formula vir : Where V dc Indicates the DC voltage at the sending end; Use inertia to support additional current ΔI vir Correct the actual current reference value of DC transmission.

4. The inertial support method for a high-voltage direct current transmission interconnection area according to claim 3, characterized in that: The additional current ΔI is supported by inertia vir Correction of actual current reference value of direct current transmission, including method: The original current reference value I of high voltage direct current transmission is ord With inertial support additional current ΔI vir Add the actual current reference value I of the DC current ref .

5. An inertial support system for a high voltage direct current transmission interconnection area, characterized in that: A method for inertial support of a high-voltage direct current transmission interconnection area for realizing any one of requirements 1-4, the system comprising: A first calculation module is used to obtain a sending-end power grid frequency and a sending-end frequency estimation value, to obtain a sending-end power grid frequency difference by subtracting the sending-end power grid frequency from the sending-end frequency estimation value, and to calculate the sending-end power grid inertial support additional power based on the sending-end power grid frequency difference; The second calculation module is used to obtain the receiving-end power grid frequency and the receiving-end frequency estimation value, to obtain the receiving-end power grid frequency difference by subtracting the receiving-end power grid frequency from the receiving-end frequency estimation value, and to calculate the receiving-end power grid inertial support additional power based on the receiving-end power grid frequency difference; The output module is used to obtain the actual inertia support additional power based on the addition of the inertia support additional power of the sending-end power grid and the negative inertia support additional power of the receiving-end power grid, and convert the actual inertia support additional power into an inertia support additional current command output.

6. A computer readable medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement an inertial support method for a high-voltage direct current transmission interconnection area as described in any one of claims 1 to 4.

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