Direct current frequency coordination control method, system and equipment considering frequency modulation capability

Abstract

The invention discloses a frequency modulation capability-considered DC frequency coordination control method, system and device, and the method comprises the steps: calculating the frequency modulation capability coefficient of each DC power transmission system participating in the frequency modulation of a sending-end AC system based on the operation state of each DC power transmission system and the equivalent parameter of a DC receiving-end AC system; based on the frequency modulation capability coefficient and the frequency of the sending end AC system, calculating the frequency modulation auxiliary power of each DC power transmission system of which the sending end is commonly connected to the same sending end AC system; adding the frequency modulation auxiliary power and each initial power to obtain alternative power of each direct current power transmission system; and determining the actual power of each direct-current power transmission system according to the comparison result of the alternative power of each direct-current power transmission system and the minimum operation power limit value and the maximum operation power limit value of each direct-current power transmission system. According to the technical scheme, the problems that the frequency modulation capability of multiple direct-current power transmission systems is not fully played and a certain direct-current receiving end alternating-current system excessively participates in frequency modulation in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current power transmission systems, and in particular to a direct current frequency coordinated control method, system and device taking frequency modulation capability into consideration. Background Art

[0002] In order to achieve the dual carbon goals of "carbon peak and carbon neutrality", in recent years, my country's new energy power generation represented by wind power and solar energy has been vigorously developed, and the installed capacity and proportion of new energy have continued to rise. Since my country's new energy is mainly concentrated in the "Three Norths" region, new energy needs to rely on high-voltage, large-capacity, and long-distance high-voltage / ultra-high-voltage direct current transmission. With the continuous increase in the scale of new energy installed capacity, in some areas where new energy power generation bases are concentrated, there are multiple direct current transmission systems. Since the new energy power generation system is mainly connected to the grid through converters, when the conventional maximum power tracking control mode is adopted, the contribution of the new energy power generation system to the frequency regulation of the power grid is almost zero. With the increase in the penetration rate of new energy power generation, it will bring huge challenges to the frequency stability of the power grid.

[0003] At present, by introducing frequency control in renewable energy power generation systems, renewable energy can participate in the frequency regulation of the power grid to a certain extent, thus improving the frequency regulation capability of the system. However, since the frequency regulation capability of renewable energy power generation systems is easily affected by weather factors, in actual projects, they can only provide transient frequency regulation support for the power grid, and their ability to improve the frequency characteristics of the system is limited. High-voltage and ultra-high-voltage DC transmission systems have the characteristics of large transmission capacity, fast regulation speed, and the ability to provide power support to the sending-end power grid based on the DC receiving-end AC system. Therefore, relying on the receiving-end AC system, studying the control technology of DC participating in the frequency regulation of the DC sending-end AC system is of great significance to improving the frequency stability of the DC sending-end AC system.

[0004] At present, conventional high-voltage and ultra-high-voltage DC transmission systems mainly participate in the primary frequency regulation and inertial response of the AC power system through droop control and inertia control. However, when there are multiple DC lines simultaneously sent out or fed into the same regional power grid, the adjustable capacity is different due to the different operating conditions of different DC lines and the frequency regulation capabilities of the DC receiving AC system. When a large power disturbance occurs in the system, if each DC transmission system still independently participates in the grid frequency regulation control, it is easy for some DC transmission systems to reach the power limit and cannot continue to regulate, while the other DC has not fully exerted its regulation capacity. Therefore, how to achieve the coordination between different DC transmission systems, give full play to the frequency regulation capabilities of all DC transmission systems, thereby improving the frequency stability of the AC power system, and avoiding excessive impact on a certain receiving AC system, is worthy of further study. Summary of the invention

[0005] The purpose of the present invention is to provide a DC frequency coordination control method, system and equipment taking into account the frequency regulation capability, so as to solve the problem that the prior art does not fully utilize the frequency regulation capability of multiple DC transmission systems and a certain DC receiving AC system excessively participates in frequency regulation.

[0006] In order to achieve the above object, the solution of the present invention is:

[0007] In a first aspect, a DC frequency coordinated control method considering frequency modulation capability is provided, comprising:

[0008] Based on the operating status of each DC transmission system, the frequency regulation margin coefficient of each DC transmission system is calculated; based on the equivalent parameters of each DC receiving AC system, the frequency regulation coefficient of each DC receiving AC system is calculated;

[0009] Based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving-end AC system, the frequency regulation capacity coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system is calculated;

[0010] Based on the frequency regulation capability coefficient of each DC transmission system and the frequency of the sending-end AC system, the frequency regulation auxiliary power of each DC transmission system connected to the same sending-end AC system at the sending end is calculated;

[0011] Adding the frequency modulation auxiliary power of each of the DC power transmission systems to the initial power of each of the DC power transmission systems to obtain the alternative power of each of the DC power transmission systems;

[0012] The actual power of each of the DC power transmission systems is determined according to a comparison result between the alternative power of each of the DC power transmission systems and the minimum operating power limit and the maximum operating power limit of each of the DC power transmission systems.

[0013] Among them, the frequency regulation margin coefficient of each DC transmission system is calculated, including the calculation of the upward power margin coefficient and the downward power margin coefficient of each DC receiving AC system, including;

[0014] Based on the operating status of each DC transmission system, the upward power margin of each DC transmission system is calculated; based on the upward power margin of each DC transmission system, the upward power margin coefficient of each DC transmission system is calculated;

[0015] Based on the operating status of each DC transmission system, the downward power margin of each DC transmission system is calculated; based on the downward power margin of each DC transmission system, the downward power margin coefficient of each DC transmission system is calculated.

[0016] Among them, the calculation of the upward power margin of each DC transmission system includes:

[0017] The initial upward power margin of each DC transmission system is obtained by subtracting the current power command of each DC transmission system from the maximum operating power limit of each DC transmission system. Then, the initial upward power margin of each DC transmission system is compared with the upward power limit, and the minimum value is obtained to obtain the upward power margin of each DC transmission system.

[0018] Calculate the upward power margin factor of each DC transmission system, including,

[0019] The upward power margins of each DC transmission system are summed to obtain the total upward power margin of all DC transmission systems, and then the total upward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average upward power margin of all DC transmission systems; the upward power margin of each DC transmission system is divided by the average upward power margin of all DC transmission systems to obtain the upward power margin coefficient of each DC transmission system;

[0020] Among them, the calculation of the downward power margin of each DC transmission system includes:

[0021] The initial downward power margin of each DC transmission system is obtained by subtracting the minimum operating power limit of each DC transmission system from the current power command of each DC transmission system, and then the initial downward power margin of each DC transmission system is compared with the downward power limit to obtain the minimum value, thereby obtaining the downward power margin of each DC transmission system;

[0022] Calculate the down regulation power margin factor of each DC transmission system, including,

[0023] The downward power margins of each DC transmission system are summed to obtain the total downward power margin of all DC transmission systems, and then the total downward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average downward power margin of all DC transmission systems; the downward power margin of each DC transmission system is divided by the average downward power margin of all DC transmission systems to obtain the downward power margin coefficient of each DC transmission system.

[0024] The frequency adjustment coefficient of each DC receiving AC system is calculated, including the frequency deviation adjustment coefficient and the frequency change rate adjustment coefficient of each DC transmission system, including:

[0025] The equivalent capacity of the DC receiving-end AC system is divided by the equivalent droop coefficient of the DC receiving-end AC system to obtain the unit regulation power of the DC receiving-end AC system; the unit regulation powers of each DC receiving-end AC system are summed to obtain the total unit regulation power of all DC receiving-end AC systems, and then the total unit regulation power of all DC receiving-end AC systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average unit regulation power of all DC receiving-end AC systems; the unit regulation power of each DC receiving-end AC system is divided by the average unit regulation power of all DC receiving-end AC systems to obtain the frequency deviation regulation coefficient of each DC receiving-end AC system;

[0026] The rotational kinetic energy of the DC receiving AC system is obtained by multiplying the equivalent capacity of the DC receiving AC system by the equivalent inertia time constant of the DC receiving AC system. The rotational kinetic energy of each DC receiving AC system is summed to obtain the total rotational kinetic energy of all DC receiving AC systems. The total rotational kinetic energy of all DC receiving AC systems is then divided by the number of DC transmission systems participating in frequency coordination control to obtain the average rotational kinetic energy of all DC receiving AC systems. The frequency change rate adjustment coefficient of each DC receiving AC system is obtained by dividing the rotational kinetic energy of each DC receiving AC system by the average rotational kinetic energy of all DC receiving AC systems.

[0027] Among them, the frequency regulation capacity coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system is calculated, including the frequency deviation regulation capacity coefficient and the frequency change rate regulation capacity coefficient of each DC transmission system, including,

[0028] When a power shortage disturbance occurs in the AC system at the DC sending end, the frequency deviation adjustment capability coefficient of each DC transmission system is the product of the downward adjustment power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the AC system at the DC receiving end, and the frequency change rate adjustment capability coefficient of each DC transmission system is the product of the downward adjustment power margin coefficient of each DC transmission system and the frequency change rate adjustment coefficient of the AC system at the DC receiving end;

[0029] When a power surplus disturbance occurs in the AC system at the DC sending end, the frequency deviation adjustment capability coefficient of each DC transmission system is the product of the upward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the AC system at the DC receiving end, and the frequency change rate adjustment capability coefficient of each DC transmission system is the product of the upward power margin coefficient of each DC transmission system and the frequency change rate adjustment coefficient of the AC system at the DC receiving end.

[0030] The calculation of the frequency modulation auxiliary power of each of the DC transmission systems connected to the same AC system at the sending end includes:

[0031] Acquire the frequency of the sending-end AC system in real time, and use the frequency of the sending-end AC system to calculate the frequency deviation value and frequency change rate of the sending-end AC system;

[0032] The first frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency deviation adjustment capacity coefficient, the proportional coefficient and the frequency deviation value of each DC power transmission system;

[0033] The second frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency change rate regulation capability coefficient, the differential coefficient and the frequency change rate of each DC power transmission system;

[0034] The frequency modulation auxiliary power of each of the direct current power transmission systems is obtained by the sum of the first frequency modulation auxiliary power and the second frequency modulation auxiliary power.

[0035] Wherein, the proportionality coefficient is the ratio of the rated operating power of each of the DC power transmission systems under the current operating mode to the equivalent droop coefficient of each of the DC power transmission systems;

[0036] The differential coefficient is twice the product of the rated operating power of each of the DC power transmission systems in the current operating mode and the equivalent inertia time constant of each of the DC power transmission systems.

[0037] Wherein, determining the actual power of each of the DC transmission systems comprises:

[0038] For each of the DC power transmission systems, if the alternative power of the DC power transmission system is less than the minimum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the minimum operating power limit of the DC power transmission system;

[0039] For each of the DC power transmission systems, if the standby power of the DC power transmission system is greater than the maximum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the maximum operating power limit of the DC power transmission system;

[0040] For each of the above-mentioned DC transmission systems, if the alternative power of the DC transmission system is not less than the minimum operating power limit of the DC transmission system and not greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the alternative power of the DC transmission system.

[0041] The frequency deviation value of the DC sending-end AC system is equal to the difference obtained by subtracting the frequency rated value of the sending-end AC system from the frequency of the sending-end AC system;

[0042] The rate of change of the frequency of the sending-end AC system is equal to the differential of the frequency of the sending-end AC system with respect to time.

[0043] In a second aspect, a DC frequency coordinated control system considering frequency modulation capability is provided, comprising:

[0044] A frequency regulation margin coefficient calculation module is configured to calculate the frequency regulation margin coefficient of each DC power transmission system based on the operating status of each DC power transmission system;

[0045] A frequency regulation coefficient calculation module is configured to calculate the frequency regulation coefficient of each DC receiving end AC system based on equivalent parameters of each DC receiving end AC system;

[0046] The frequency regulation capability coefficient calculation module is configured to calculate the frequency regulation capability coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving-end AC system;

[0047] A frequency modulation auxiliary frequency calculation module is configured to calculate the frequency modulation auxiliary power of each DC power transmission system connected to the same sending-end AC system at the sending end based on the frequency modulation capability coefficient of each DC power transmission system and the frequency of the sending-end AC system;

[0048] a candidate power calculation module configured to add the frequency modulation auxiliary power of each of the DC power transmission systems to the initial power of each of the DC power transmission systems to obtain the candidate power of each of the DC power transmission systems; and

[0049] The system actual power determination module is configured to determine the actual power of each of the DC power transmission systems according to a comparison result of the alternative power of each of the DC power transmission systems with the minimum operating power limit and the maximum operating power limit of each of the DC power transmission systems.

[0050] The frequency regulation margin coefficient calculation module includes an upward power margin coefficient calculation module and a downward power margin coefficient calculation module.

[0051] Among them, the upward power margin coefficient calculation module includes:

[0052] A first calculation module is configured to calculate the upward power margin of each DC power transmission system based on the operating status of each DC power transmission system; and

[0053] A second calculation module is configured to calculate an upward power margin coefficient of each DC power transmission system based on the upward power margin of each DC power transmission system;

[0054] Among them, the downward adjustment power margin coefficient calculation module includes:

[0055] A third calculation module is configured to calculate the downward power margin of each DC power transmission system based on the operating status of each DC power transmission system; and

[0056] The fourth calculation module is configured to calculate a downward power margin coefficient of each DC power transmission system based on the downward power margin of each DC power transmission system.

[0057] The first calculation module calculates the upward power margin of each DC transmission system, including:

[0058] The initial upward power margin of each DC transmission system is obtained by subtracting the current power command of each DC transmission system from the maximum operating power limit of each DC transmission system. Then, the initial upward power margin of each DC transmission system is compared with the upward power limit, and the minimum value is obtained to obtain the upward power margin of each DC transmission system.

[0059] The second calculation module calculates the upward power margin coefficient of each DC transmission system, including:

[0060] The upward power margins of each DC transmission system are summed to obtain the total upward power margin of all DC transmission systems, and then the total upward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average upward power margin of all DC transmission systems; the upward power margin of each DC transmission system is divided by the average upward power margin of all DC transmission systems to obtain the upward power margin coefficient of each DC transmission system;

[0061] The third calculation module calculates the downward power margin of each DC transmission system, including:

[0062] The initial downward power margin of each DC transmission system is obtained by subtracting the minimum operating power limit of each DC transmission system from the current power command of each DC transmission system, and then the initial downward power margin of each DC transmission system is compared with the downward power limit to obtain the minimum value, thereby obtaining the downward power margin of each DC transmission system;

[0063] The fourth calculation module calculates the downward power margin coefficient of each DC transmission system, including:

[0064] The downward power margins of each DC transmission system are summed to obtain the total downward power margin of all DC transmission systems, and then the total downward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average downward power margin of all DC transmission systems; the downward power margin of each DC transmission system is divided by the average downward power margin of all DC transmission systems to obtain the downward power margin coefficient of each DC transmission system.

[0065] Wherein, the frequency adjustment coefficient calculation module includes a frequency deviation adjustment coefficient calculation module and a frequency change rate adjustment coefficient;

[0066] The frequency deviation adjustment coefficient calculation module is configured to calculate the frequency deviation adjustment coefficient of each DC power transmission system, including:

[0067] The equivalent capacity of the DC receiving-end AC system is divided by the equivalent droop coefficient of the DC receiving-end AC system to obtain the unit regulation power of the DC receiving-end AC system; the unit regulation powers of each DC receiving-end AC system are summed to obtain the total unit regulation power of all DC receiving-end AC systems, and then the total unit regulation power of all DC receiving-end AC systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average unit regulation power of all DC receiving-end AC systems; the unit regulation power of each DC receiving-end AC system is divided by the average unit regulation power of all DC receiving-end AC systems to obtain the frequency deviation regulation coefficient of each DC receiving-end AC system;

[0068] The frequency change rate adjustment coefficient is configured to calculate the frequency change rate adjustment coefficient of each DC transmission system, including:

[0069] The rotational kinetic energy of the DC receiving AC system is obtained by multiplying the equivalent capacity of the DC receiving AC system by the equivalent inertia time constant of the DC receiving AC system. The rotational kinetic energy of each DC receiving AC system is summed to obtain the total rotational kinetic energy of all DC receiving AC systems. The total rotational kinetic energy of all DC receiving AC systems is then divided by the number of DC transmission systems participating in frequency coordination control to obtain the average rotational kinetic energy of all DC receiving AC systems. The frequency change rate adjustment coefficient of each DC receiving AC system is obtained by dividing the rotational kinetic energy of each DC receiving AC system by the average rotational kinetic energy of all DC receiving AC systems.

[0070] Wherein, the frequency regulation capability coefficient calculation module includes a frequency deviation adjustment capability coefficient calculation module and a frequency change rate adjustment capability coefficient calculation module;

[0071] The frequency deviation adjustment capacity coefficient calculation module is configured to calculate the product of the downward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the DC receiving-end AC system to obtain the frequency deviation adjustment capacity coefficient of each DC transmission system when a power shortage disturbance occurs in the DC sending-end AC system; when a power surplus disturbance occurs in the DC sending-end AC system, calculate the product of the upward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the DC receiving-end AC system to obtain the frequency deviation adjustment capacity coefficient of each DC transmission system;

[0072] Among them, the frequency change rate regulation capability coefficient calculation module is configured to, when a power shortage disturbance occurs in the AC system at the DC sending end, calculate the product of the downward power margin coefficient of each DC transmission system and the frequency change rate regulation coefficient of the AC system at the DC receiving end to obtain the frequency change rate regulation capability coefficient of each DC transmission system; when a power surplus disturbance occurs in the AC system at the DC sending end, calculate the product of the upward power margin coefficient of each DC transmission system and the frequency change rate regulation coefficient of the AC system at the DC receiving end to obtain the frequency change rate regulation capability coefficient of each DC transmission system.

[0073] The frequency modulation auxiliary frequency calculation module calculates the frequency modulation auxiliary power of each of the DC power transmission systems connected to the same AC system at the sending end, including:

[0074] Acquire the frequency of the sending-end AC system in real time, and use the frequency of the sending-end AC system to calculate the frequency deviation value and frequency change rate of the sending-end AC system;

[0075] The first frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency deviation adjustment capacity coefficient, the proportional coefficient and the frequency deviation value of each DC power transmission system;

[0076] The second frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency change rate regulation capability coefficient, the differential coefficient and the frequency change rate of each DC power transmission system;

[0077] The frequency modulation auxiliary power of each of the direct current power transmission systems is obtained by the sum of the first frequency modulation auxiliary power and the second frequency modulation auxiliary power.

[0078] Wherein, the proportionality coefficient is the ratio of the rated operating power of each of the DC power transmission systems under the current operating mode to the equivalent droop coefficient of each of the DC power transmission systems;

[0079] The differential coefficient is twice the product of the rated operating power of each of the DC power transmission systems in the current operating mode and the equivalent inertia time constant of each of the DC power transmission systems.

[0080] The system actual power determination module determines the actual power of each of the DC power transmission systems, including:

[0081] For each of the DC power transmission systems, if the alternative power of the DC power transmission system is less than the minimum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the minimum operating power limit of the DC power transmission system;

[0082] For each of the DC power transmission systems, if the standby power of the DC power transmission system is greater than the maximum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the maximum operating power limit of the DC power transmission system;

[0083] For each of the above-mentioned DC transmission systems, if the alternative power of the DC transmission system is not less than the minimum operating power limit of the DC transmission system and not greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the alternative power of the DC transmission system.

[0084] The frequency deviation value of the DC sending-end AC system is equal to the difference obtained by subtracting the frequency rated value of the sending-end AC system from the frequency of the sending-end AC system;

[0085] The rate of change of the frequency of the sending-end AC system is equal to the differential of the frequency of the sending-end AC system with respect to time.

[0086] In a third aspect, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the DC frequency coordination control method considering the frequency modulation capability as described above are implemented.

[0087] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored; when the computer program is executed by a processor, the steps of the DC frequency coordination control method considering the frequency modulation capability as described above are implemented.

[0088] After adopting the above scheme, the present invention takes into account the frequency regulation capabilities of the DC transmission system and the DC receiving AC system. When a large load disturbance occurs in the AC power system, the active power transmitted by each DC transmission system is adjusted through frequency coordination control, the frequency regulation capability of the AC power system is improved, the system frequency fluctuation rate and amplitude are reduced, and the frequency stability of the AC power system is improved. At the same time, excessive participation of a certain DC and excessive influence on a certain receiving AC system are avoided, and coordinated sharing between different DCs is achieved, thereby improving the frequency stability of the AC power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 is a flow chart of a DC frequency coordinated control method considering frequency modulation capability according to an embodiment of the present invention;

[0090] Figure 2 is a principle structure diagram of a high voltage direct current transmission system according to an embodiment of the present invention;

[0091] Figure 3 is a principle structure diagram of an ultra-high voltage direct current transmission system according to an embodiment of the present invention;

[0092] Figure 4 is a principle block diagram of a DC frequency coordinated control method considering frequency modulation capability according to an embodiment of the present invention;

[0093] Figure 5 It is a structural block diagram of a DC frequency coordinated control system with frequency modulation capability according to an embodiment of the present invention. DETAILED DESCRIPTION

[0094] 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 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.

[0095] The embodiment of the present invention discloses a DC frequency coordinated control method considering frequency modulation capability. The method is applicable to high voltage and ultra-high voltage DC transmission systems, especially conventional high voltage and ultra-high voltage DC transmission systems using grid phase-changing converter valves. The principle structures of conventional high voltage and ultra-high voltage DC transmission systems are as follows: Figure 2 and Figure 3 As shown, each high-voltage and ultra-high-voltage DC transmission system includes the following structure: a sending-end AC grid 11, a sending-end pole I system 12, a pole I DC transmission line 13, a receiving-end pole I system 14, a grounding pole lead 15, a grounding pole 16, a sending-end pole II system 17, a pole II DC transmission line 18, a receiving-end pole II system 19 and a receiving-end AC grid 20. The main difference between each high-voltage and ultra-high-voltage DC transmission system is that each high-voltage DC transmission system includes only one converter per pole, while each ultra-high-voltage DC transmission system includes two converters, a high-end converter and a low-end converter, per pole. In actual projects, the frequency coordination control function of each DC transmission system is usually implemented in a bipolar layer control system, which ensures the rapidity of its response by detecting the frequency of the AC power system and directly controlling the transmission power of each DC transmission system.

[0096] Based on this, Figure 1 and Figure 4 As shown, the DC frequency coordinated control method considering the frequency modulation capability of the embodiment of the present invention includes the following steps:

[0097] Step 1, realizing multi-DC frequency coordinated control, including step S101;

[0098] Step S101: based on the operating status of each DC power transmission system, the frequency regulation margin coefficient of each DC power transmission system is calculated; based on the equivalent parameters of each DC receiving-end AC system, the frequency regulation coefficient of each DC power transmission system is calculated.

[0099] Specifically, the frequency adjustment margin coefficient includes an upward power margin coefficient and a downward power margin coefficient, and the frequency adjustment coefficient includes a frequency deviation adjustment coefficient and a frequency change rate adjustment coefficient; this step includes the following process:

[0100] 1. Based on the operating status of each DC transmission system, calculate the upward power margin and downward power margin of each DC transmission system.

[0101] Specifically, this step includes the following process:

[0102] (1) The maximum operating power limit P of each DC transmission system max_dc_i Subtract the current power command P of each DC transmission system ref0_dc_i , and the initial upward power margin ΔP of each DC transmission system is obtained INC_dc_0_i , then, the initial upward power margin ΔP of each DC transmission system INC_dc_0_i With the increase of power limit ΔP INC_dc_limt_i After comparing and finding the minimum value, the upward power margin ΔP of each DC transmission system is obtained. INC_dc_i ; Wherein, the subscript i represents the i-th DC transmission system, i = 1, 2, ..., m, m is the number of DC transmission systems, the same below, no further description is given. The upward power margin ΔP of each DC transmission system INC_dc_i The specific calculation formula is:

[0103] ΔP INC_dc_i =min((P max_dc_i -P ref0_dc_i ), ΔP INC_dc_limt_i )

[0104] In the above formula, the power limit is increased by ΔP INC_dc_limt_i The value ranges from 0.02pu to 0.8pu.

[0105] (2) The current power command P of each DC transmission system ref0_dc_i Subtract the minimum operating power limit P of each DC transmission system min_dc_i , and the initial down-regulation power margin ΔP of each DC transmission system is obtained DEC_dc_0_i , then, the initial down-regulation power margin ΔP of each DC transmission system DEC_dc_0_i With the power limit ΔP down DEC_dc_limt_i After comparing and finding the minimum value, the downward power margin ΔP of each DC transmission system is obtained. DEC_dc_i The downward power margin ΔP of each DC transmission system DEC_dc_i The specific calculation formula is:

[0106] ΔP DEC_dc_i =min((P ref0_dc_i -P min_dc_i ), ΔP DEC_dc_limt_i )

[0107] In the above formula, the downward power limit ΔP DEC_dc_limt_i The value ranges from 0.02pu to 0.8pu.

[0108] 2. Based on the upward power margin and downward power margin of each DC transmission system, calculate the upward power margin coefficient and downward power margin coefficient of each DC transmission system.

[0109] Specifically, this step includes the following process:

[0110] (1) The power margin of each DC transmission system is increased by ΔP INC_dc_i Sum up and get the total upward power margin ΔP of all DC transmission systems INC_dc_all , and then the total upward power margin of all DC transmission systems ΔP INC_dc_all Divided by the number of DC transmission systems participating in frequency coordination control m, the average upward power margin ΔP of all DC transmission systems is obtained INC_dc_avg ; Increase the power margin ΔP of each DC transmission system INC_dc_i Divided by the average upward power margin ΔP of all DC transmission systems INC_dc_avg , and obtain the upward power margin coefficient k of each DC transmission system ΔP_INC_dc_i The power margin factor k of each DC transmission system is ΔP_INC_dc_i The specific expression is:

[0111]

[0112] (2) The power margin of each DC transmission system is adjusted downward by ΔP DEC_dc_i Sum up and get the total down regulation power margin ΔP of all DC transmission systems DEC_dc_all , and then the total down-regulation power margin of all DC transmission systems ΔP DEC_dc_all Divided by the number of DC transmission systems participating in frequency coordination control m, the average downward power margin ΔP of all DC transmission systems is obtained DEC_dc_avg ; Reduce the power margin of each DC transmission system by ΔP DEC_dc_i Divided by the average down regulation power margin ΔP of all DC transmission systems DEC_dc_avg , and obtain the downward power margin coefficient k of each DC transmission system ΔP_DEC_dc_i The power margin factor k of each DC transmission system is ΔP_DEC_dc_i The specific expression is:

[0113]

[0114] 3. Based on the equivalent parameters of the DC receiving-end AC system, calculate the frequency deviation adjustment coefficient and frequency change rate adjustment coefficient of the DC receiving-end AC system.

[0115] Specifically, this step includes the following process:

[0116] (1) The equivalent capacity S of the AC system at the DC receiving end B_SiDivide by the equivalent droop coefficient R of the DC receiving AC system SG_Si , we can get the unit regulation power P of the DC receiving AC system SG_f_Si ; The unit adjustment power P of each DC receiving AC system SG_f_Si Sum and get the total unit regulation power P of all DC receiving AC systems SG_f_all , then the total unit regulated power P of all DC receiving AC systems SG_f_all Divided by the number of DC transmission systems participating in frequency coordination control m, the average unit regulation power P of all DC receiving AC systems is obtained. SG_f_avg ; The unit adjustment power P of each DC receiving AC system SG_f_Si Divide by the average unit regulation power P of all DC receiving AC systems SG_f_avg , and obtain the frequency deviation adjustment coefficient k of each DC receiving AC system Δf_Si The frequency deviation adjustment coefficient k of the DC receiving AC system Δf_Si The specific expression is:

[0117]

[0118] (2) The equivalent capacity S of the AC system at the DC receiving end B_Si Multiply by the equivalent inertia time constant H of the AC system at the DC receiving end Si , we can get the rotational kinetic energy E of the DC receiving AC system Si ; The rotational kinetic energy E of each DC receiving AC system Si Add up and get the total rotational kinetic energy E of all DC receiving AC systems all , then the total rotational kinetic energy E of all DC receiving AC systems all Divided by the number of DC transmission systems participating in frequency coordination control, m, we can get the average rotational kinetic energy E of all DC receiving AC systems. avg ; The rotational kinetic energy E of each DC receiving AC system Si Divided by the average rotational kinetic energy E of all DC receiving AC systems avg , and obtain the frequency change rate adjustment coefficient k of each DC receiving AC system dfdt_Si The frequency change rate adjustment coefficient k of the DC receiving AC system dfdt_Si The specific expression is:

[0119]

[0120] Step 2, realizing DC frequency control, including steps S102-S105;

[0121] S102: Calculating the frequency regulation capability coefficient of each DC transmission system participating in the frequency regulation of the AC system at the sending end based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving end AC system;

[0122] Specifically, the frequency modulation capability parameters include a frequency deviation adjustment capability coefficient and a frequency change rate adjustment capability coefficient; this step includes the following two situations:

[0123] (1) When a power shortage disturbance occurs in the AC system at the DC transmission end, the frequency deviation adjustment capability coefficient of each DC transmission system is the downward adjustment power margin coefficient k of each DC transmission system. ΔP_DEC_dc_i Frequency deviation adjustment coefficient k of the AC system at the DC receiving end Δf_Si The frequency change rate regulation capability coefficient of each DC transmission system is the downward power margin coefficient k of each DC transmission system. ΔP_DEC_dc_i The frequency change rate adjustment coefficient k of the AC system at the DC receiving end dfdt_Si The product of.

[0124] (2) When a power surplus disturbance occurs in the AC system at the DC transmission end, the frequency deviation adjustment capability coefficient of each DC transmission system is the upward power margin coefficient k of each DC transmission system. ΔP_INC_dc_i Frequency deviation adjustment coefficient k of the AC system at the DC receiving end Δf_Si The frequency change rate regulation capability coefficient of each DC transmission system is the upward power margin coefficient k of each DC transmission system. ΔP_INC_dc_i The frequency change rate adjustment coefficient k of the AC system at the DC receiving end dfdt_Si The product of.

[0125] In summary, the frequency deviation adjustment capability coefficient k of each DC transmission system is a_Δf_i The expression is:

[0126]

[0127] Frequency change rate regulation capability coefficient k of each DC transmission system a_dfdt_i The expression is:

[0128]

[0129] Step S103: based on the frequency regulation capability coefficient of each DC power transmission system and the frequency of the sending-end AC system, the frequency regulation auxiliary power of each DC power transmission system connected to the same sending-end AC system is calculated.

[0130] Specifically, this step includes the following process:

[0131] 1. Acquire the frequency of the DC sending end AC system in real time, and use the frequency of the DC sending end AC system to calculate the frequency deviation value and frequency change rate of the DC sending end AC system;

[0132] Specifically, this step includes the following process:

[0133] (1) Based on the voltage of the AC power system, the original frequency f0 of the AC power system is calculated through a phase-locked loop, and the frequency f of the AC system at the sending end is obtained after filtering. 0_filt , the filter can be a first-order inertial filter or a second-order filter.

[0134] (2) Based on the normalization of the filtered system frequency, the system frequency f is obtained, and its calculation formula is: Among them, f n It is worth noting that the frequency of the AC power system described in the embodiment of the present invention is a frequency that has been filtered, and generally uses a normalized frequency f.

[0135] (3) The frequency of the AC power system is used to calculate the deviation value and the rate of change of the frequency of the AC power system.

[0136] Specifically, the deviation value of the frequency of the AC power system is equal to the difference obtained by subtracting the rated value of the frequency of the AC power system from the frequency of the AC power system. Let Δf represent the deviation value of the AC power system, then Δf=f-1.

[0137] Specifically, the rate of change of the frequency of the AC power system is equal to the differential of the frequency of the AC power system with respect to time, that is, the rate of change is

[0138] 2. The frequency deviation adjustment capability coefficient, the proportionality coefficient and the frequency deviation value of each DC power transmission system are multiplied to obtain the first frequency modulation auxiliary power of each DC power transmission system. The specific expression of the first frequency modulation auxiliary power of each DC power transmission system is:

[0139] P f1_dc_i =k a_Δf_i k p_dc_i Δf

[0140] 3. The second frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency change rate adjustment capability coefficient, the differential coefficient and the frequency change rate of each DC power transmission system. The specific expression of the second frequency regulation auxiliary power of each DC power transmission system is:

[0141]

[0142] 4. The frequency modulation auxiliary power of each of the DC power transmission systems is obtained by summing the first frequency modulation auxiliary power and the second frequency modulation auxiliary power. The specific expression of the frequency modulation auxiliary power of each of the DC power transmission systems is:

[0143] P f_dc_i =P f1_dc_i +P f2_dc_i

[0144] In summary

[0145]

[0146] Step S104: adding the frequency modulation auxiliary power of each DC power transmission system to the initial power of each DC power transmission system to obtain the alternative power of each DC power transmission system.

[0147] P d_ord1_i represents the alternative frequency of each DC transmission system i, P d_ord0_i represents the initial power of each DC transmission system i, then P d_ord1_i =P f_dc_i +P d_ord0_i .

[0148] Step S105: determining the actual power of each DC power transmission system according to the comparison result of the candidate power of each DC power transmission system with the minimum operating power limit and the maximum operating power limit of each DC power transmission system.

[0149] Specifically, depending on the comparison results, there are the following situations:

[0150] (1) For each DC transmission system, if the alternative power of the DC transmission system is less than the minimum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the minimum operating power limit of the DC transmission system.

[0151] P min_dc_i represents the minimum operating power limit of each DC transmission system i, P d_ord_i represents the actual power of each DC transmission system i, that is, P d_ord1_i <P min_dc_i , then limit processing is performed, P d_ord_i =P min_dc_i .

[0152] (2) For each DC transmission system, if the alternative power of the DC transmission system is greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the maximum operating power limit of the DC transmission system.

[0153] P max_dc_i represents the maximum operating power limit of each DC transmission system i, that is, P d_ord1_i>P max_dc_i , then limit processing is performed, P d_ord_i =P max_dc_i .

[0154] (3) For each DC transmission system, if the alternative power of the DC transmission system is not less than the minimum operating power limit of the DC transmission system and not greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the alternative power of the DC transmission system.

[0155] That is, P min_dc_i ≤P d_ord1_i ≤P max_dc_i , then P d_ord_i =P d_ord1_i .

[0156] The above-mentioned maximum operating power limit and minimum operating power limit can be determined based on experience. For example, in a specific embodiment of the present invention, the maximum operating power limit is 1.0pu and the minimum operating power limit is 0.1pu; when each DC transmission system has overload operation capability, the maximum operating power limit of each DC transmission system can also be the 2h overload fixed value of each DC transmission system.

[0157] Through the above-mentioned limiting processing, the actual power of each DC transmission system can be limited between the maximum operating power limit and the minimum operating power limit.

[0158] An embodiment of the present invention further discloses a computer-readable storage medium having computer program instructions stored thereon; when the computer program instructions are executed by a processor, the DC frequency coordination control method considering the frequency modulation capability as described in the above embodiment is implemented.

[0159] The embodiment of the present invention also discloses a DC frequency coordinated control system considering frequency modulation capability, such as Figure 5 As shown, the system includes: a multi-DC frequency coordination control subsystem 501 and a DC frequency control subsystem 502 .

[0160] The multi-DC frequency coordination control subsystem 501 is used to calculate the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of the receiving AC system, including:

[0161] A frequency regulation margin coefficient calculation module is configured to calculate the frequency regulation margin coefficient of each DC power transmission system based on the operating status of each DC power transmission system; and

[0162] The frequency regulation coefficient calculation module is configured to calculate the frequency regulation coefficient of each DC receiving end AC system based on the equivalent parameters of each DC receiving end AC system.

[0163] The DC frequency control subsystem 502 is used to calculate the power instruction of the DC transmission system including the DC frequency modulation auxiliary power, including:

[0164] The frequency regulation capability coefficient calculation module is configured to calculate the frequency regulation capability coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving-end AC system;

[0165] A frequency modulation auxiliary frequency calculation module is configured to calculate the frequency modulation auxiliary power of each DC power transmission system connected to the same sending-end AC system at the sending end based on the frequency modulation capability coefficient of each DC power transmission system and the frequency of the sending-end AC system;

[0166] a candidate power calculation module configured to add the frequency modulation auxiliary power of each of the DC power transmission systems to the initial power of each of the DC power transmission systems to obtain the candidate power of each of the DC power transmission systems; and

[0167] The system actual power determination module is configured to determine the actual power of each of the DC power transmission systems according to a comparison result of the alternative power of each of the DC power transmission systems with the minimum operating power limit and the maximum operating power limit of each of the DC power transmission systems.

[0168] An embodiment of the present invention further discloses a computer device, including a processor and a memory configured to store a computer program that can be run on the processor; wherein, when the processor is configured to run the computer program, the method steps in the aforementioned embodiment are executed.

[0169] In practical applications, the processor includes a field programmable gate array (FPGA), and the processor may be a central processing unit (CPU) or a digital signal processor (DSP). It is understandable that for different devices, the electronic device used to implement the function of the processor may be other, and the embodiment of the present invention does not specifically limit it.

[0170] The above-mentioned memory can be a volatile memory (volatile memory), such as a random access memory (RAM); or a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory, a hard disk (HDD) or a solid-state drive (SSD); or a combination of the above-mentioned types of memory, and provide instructions and data to the processor.

[0171] An embodiment of the present invention further discloses a computer-readable storage medium, on which a computer program is stored; when the computer program is executed by a processor, the DC frequency coordination control method considering the frequency modulation capability as described in the above embodiment is implemented.

[0172] In summary, the embodiments of the present invention are used in high voltage or ultra-high voltage DC transmission systems. When a large load disturbance occurs in the AC power system, the active power transmitted by each DC transmission system is adjusted through frequency coordination control, the frequency regulation capability of the AC power system is improved, the system frequency fluctuation rate and amplitude are reduced, the frequency stability of the AC power system is improved, and the safe and stable operation of the AC power system is ensured.

[0173] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0174] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0175] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0176] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0177] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0178] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A DC frequency coordinated control method considering frequency modulation capability, characterized in that: include, Based on the operating status of each DC transmission system, the frequency regulation margin coefficient of each DC transmission system is calculated; based on the equivalent parameters of each DC receiving AC system, the frequency regulation coefficient of each DC receiving AC system is calculated; Based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving-end AC system, the frequency regulation capacity coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system is calculated; Based on the frequency regulation capability coefficient of each DC transmission system and the frequency of the sending-end AC system, the frequency regulation auxiliary power of each DC transmission system connected to the same sending-end AC system at the sending end is calculated; Adding the frequency modulation auxiliary power of each of the DC power transmission systems to the initial power of each of the DC power transmission systems to obtain the alternative power of each of the DC power transmission systems; The actual power of each of the DC power transmission systems is determined according to a comparison result between the alternative power of each of the DC power transmission systems and the minimum operating power limit and the maximum operating power limit of each of the DC power transmission systems.

2. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 1, characterized in that: Calculate the frequency margin coefficient of each DC transmission system, including the upward power margin coefficient and downward power margin coefficient of each DC receiving AC system, including; Based on the operating status of each DC transmission system, the upward power margin of each DC transmission system is calculated; based on the upward power margin of each DC transmission system, the upward power margin coefficient of each DC transmission system is calculated; Based on the operating status of each DC transmission system, the downward power margin of each DC transmission system is calculated; based on the downward power margin of each DC transmission system, the downward power margin coefficient of each DC transmission system is calculated.

3. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 2, characterized in that: Calculate the upward power margin of each DC transmission system, including, The initial upward power margin of each DC transmission system is obtained by subtracting the current power command of each DC transmission system from the maximum operating power limit of each DC transmission system. Then, the initial upward power margin of each DC transmission system is compared with the upward power limit, and the minimum value is obtained to obtain the upward power margin of each DC transmission system. Calculate the upward power margin factor of each DC transmission system, including, The upward power margin of each DC transmission system is summed up to obtain the total upward power margin of all DC transmission systems, and then the total upward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average upward power margin of all DC transmission systems; the upward power margin of each DC transmission system is divided by the average upward power margin of all DC transmission systems to obtain the upward power margin coefficient of each DC transmission system.

4. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 2, characterized in that: Calculate the power margin of each DC transmission system, including: The initial downward power margin of each DC transmission system is obtained by subtracting the minimum operating power limit of each DC transmission system from the current power command of each DC transmission system, and then the initial downward power margin of each DC transmission system is compared with the downward power limit to obtain the minimum value, thereby obtaining the downward power margin of each DC transmission system; Calculate the down regulation power margin factor of each DC transmission system, including, The downward power margins of each DC transmission system are summed to obtain the total downward power margin of all DC transmission systems, and then the total downward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average downward power margin of all DC transmission systems; the downward power margin of each DC transmission system is divided by the average downward power margin of all DC transmission systems to obtain the downward power margin coefficient of each DC transmission system.

5. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 1, characterized in that: Calculate the frequency adjustment coefficient of each DC receiving AC system, including calculating the frequency deviation adjustment coefficient and frequency change rate adjustment coefficient of each DC transmission system, including, The equivalent capacity of the AC system at the DC receiving end is divided by the equivalent droop coefficient of the AC system at the DC receiving end to obtain the unit regulation power of the AC system at the DC receiving end; The unit regulation power of each DC receiving AC system is summed to obtain the total unit regulation power of all DC receiving AC systems, and then the total unit regulation power of all DC receiving AC systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average unit regulation power of all DC receiving AC systems; The unit regulation power of each DC receiving end AC system is divided by the average unit regulation power of all DC receiving end AC systems to obtain the frequency deviation regulation coefficient of each DC receiving end AC system; The rotational kinetic energy of the DC receiving AC system is obtained by multiplying the equivalent capacity of the DC receiving AC system by the equivalent inertia time constant of the DC receiving AC system. The rotational kinetic energy of each DC receiving AC system is summed to obtain the total rotational kinetic energy of all DC receiving AC systems. The total rotational kinetic energy of all DC receiving AC systems is then divided by the number of DC transmission systems participating in frequency coordination control to obtain the average rotational kinetic energy of all DC receiving AC systems. The frequency change rate adjustment coefficient of each DC receiving AC system is obtained by dividing the rotational kinetic energy of each DC receiving AC system by the average rotational kinetic energy of all DC receiving AC systems.

6. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 2, characterized in that: Calculate the frequency regulation capability coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system, including calculating the frequency deviation regulation capability coefficient and frequency change rate regulation capability coefficient of each DC transmission system, including, When a power shortage disturbance occurs in the AC system at the DC sending end, the frequency deviation adjustment capability coefficient of each DC transmission system is the product of the downward adjustment power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the AC system at the DC receiving end, and the frequency change rate adjustment capability coefficient of each DC transmission system is the product of the downward adjustment power margin coefficient of each DC transmission system and the frequency change rate adjustment coefficient of the AC system at the DC receiving end; When a power surplus disturbance occurs in the AC system at the DC sending end, the frequency deviation adjustment capability coefficient of each DC transmission system is the product of the upward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the AC system at the DC receiving end, and the frequency change rate adjustment capability coefficient of each DC transmission system is the product of the upward power margin coefficient of each DC transmission system and the frequency change rate adjustment coefficient of the AC system at the DC receiving end.

7. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 1, characterized in that: Calculating the frequency modulation auxiliary power of each of the DC transmission systems connected to the same AC system at the sending end includes: Acquire the frequency of the sending-end AC system in real time, and use the frequency of the sending-end AC system to calculate the frequency deviation value and frequency change rate of the sending-end AC system; The first frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency deviation adjustment capacity coefficient, the proportional coefficient and the frequency deviation value of each DC power transmission system; The second frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency change rate regulation capability coefficient, the differential coefficient and the frequency change rate of each DC power transmission system; The frequency modulation auxiliary power of each of the direct current power transmission systems is obtained by the sum of the first frequency modulation auxiliary power and the second frequency modulation auxiliary power.

8. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 7, characterized in that: The proportionality coefficient is the ratio of the rated operating power of each of the DC power transmission systems in the current operating mode to the equivalent droop coefficient of each of the DC power transmission systems; The differential coefficient is twice the product of the rated operating power of each of the DC power transmission systems in the current operating mode and the equivalent inertia time constant of each of the DC power transmission systems.

9. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 1, characterized in that: Determining the actual power of each of the DC transmission systems, comprising, For each of the DC power transmission systems, if the standby power of the DC power transmission system is less than the minimum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the minimum operating power limit of the DC power transmission system; For each of the DC power transmission systems, if the standby power of the DC power transmission system is greater than the maximum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the maximum operating power limit of the DC power transmission system; For each of the above-mentioned DC transmission systems, if the alternative power of the DC transmission system is not less than the minimum operating power limit of the DC transmission system and not greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the alternative power of the DC transmission system.

10. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 7, characterized in that: The frequency deviation value of the DC sending-end AC system is equal to the difference obtained by subtracting the frequency rated value of the sending-end AC system from the frequency of the sending-end AC system; The rate of change of the frequency of the sending-end AC system is equal to the differential of the frequency of the sending-end AC system with respect to time.

11. A DC frequency coordinated control system considering frequency modulation capability, characterized in that: include, A frequency regulation margin coefficient calculation module is configured to calculate the frequency regulation margin coefficient of each DC power transmission system based on the operating status of each DC power transmission system; A frequency regulation coefficient calculation module is configured to calculate the frequency regulation coefficient of each DC receiving end AC system based on equivalent parameters of each DC receiving end AC system; The frequency regulation capability coefficient calculation module is configured to calculate the frequency regulation capability coefficient of each DC transmission system participating in the frequency regulation of the sending-end AC system based on the frequency regulation margin coefficient of each DC transmission system and the frequency regulation coefficient of each DC receiving-end AC system; A frequency modulation auxiliary frequency calculation module is configured to calculate the frequency modulation auxiliary power of each DC power transmission system connected to the same sending-end AC system at the sending end based on the frequency modulation capability coefficient of each DC power transmission system and the frequency of the sending-end AC system; a candidate power calculation module configured to add the frequency modulation auxiliary power of each of the DC power transmission systems to the initial power of each of the DC power transmission systems to obtain the candidate power of each of the DC power transmission systems; and The system actual power determination module is configured to determine the actual power of each of the DC power transmission systems according to a comparison result of the alternative power of each of the DC power transmission systems with the minimum operating power limit and the maximum operating power limit of each of the DC power transmission systems.

12. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 11, characterized in that: The frequency regulation margin coefficient calculation module includes an upward power margin coefficient calculation module and a downward power margin coefficient calculation module. Among them, the upward power margin coefficient calculation module includes: A first calculation module is configured to calculate the upward power margin of each DC power transmission system based on the operating status of each DC power transmission system; and A second calculation module is configured to calculate an upward power margin coefficient of each DC power transmission system based on the upward power margin of each DC power transmission system; Among them, the downward adjustment power margin coefficient calculation module includes: A third calculation module is configured to calculate the downward power margin of each DC power transmission system based on the operating status of each DC power transmission system; and The fourth calculation module is configured to calculate a downward power margin coefficient of each DC power transmission system based on the downward power margin of each DC power transmission system.

13. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 12, characterized in that: The first calculation module calculates the upward power margin of each DC transmission system, including: The initial upward power margin of each DC transmission system is obtained by subtracting the current power command of each DC transmission system from the maximum operating power limit of each DC transmission system. Then, the initial upward power margin of each DC transmission system is compared with the upward power limit, and the minimum value is obtained to obtain the upward power margin of each DC transmission system. The second calculation module calculates the upward power margin coefficient of each DC transmission system, including: The upward power margin of each DC transmission system is summed up to obtain the total upward power margin of all DC transmission systems, and then the total upward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average upward power margin of all DC transmission systems; the upward power margin of each DC transmission system is divided by the average upward power margin of all DC transmission systems to obtain the upward power margin coefficient of each DC transmission system.

14. The DC frequency coordinated control method considering frequency modulation capability as claimed in claim 12, characterized in that: The third calculation module calculates the downward power margin of each DC transmission system, including: The initial downward power margin of each DC transmission system is obtained by subtracting the minimum operating power limit of each DC transmission system from the current power command of each DC transmission system, and then the initial downward power margin of each DC transmission system is compared with the downward power limit to obtain the minimum value, thereby obtaining the downward power margin of each DC transmission system; The fourth calculation module calculates the downward power margin coefficient of each DC transmission system, including: The downward power margins of each DC transmission system are summed to obtain the total downward power margin of all DC transmission systems, and then the total downward power margin of all DC transmission systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average downward power margin of all DC transmission systems; the downward power margin of each DC transmission system is divided by the average downward power margin of all DC transmission systems to obtain the downward power margin coefficient of each DC transmission system.

15. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 11, characterized in that: The frequency adjustment coefficient calculation module includes a frequency deviation adjustment coefficient calculation module and a frequency change rate adjustment coefficient; The frequency deviation adjustment coefficient calculation module is configured to calculate the frequency deviation adjustment coefficient of each DC power transmission system, including: The equivalent capacity of the DC receiving-end AC system is divided by the equivalent droop coefficient of the DC receiving-end AC system to obtain the unit regulation power of the DC receiving-end AC system; the unit regulation powers of each DC receiving-end AC system are summed to obtain the total unit regulation power of all DC receiving-end AC systems, and then the total unit regulation power of all DC receiving-end AC systems is divided by the number of DC transmission systems participating in frequency coordination control to obtain the average unit regulation power of all DC receiving-end AC systems; the unit regulation power of each DC receiving-end AC system is divided by the average unit regulation power of all DC receiving-end AC systems to obtain the frequency deviation regulation coefficient of each DC receiving-end AC system; The frequency change rate adjustment coefficient is configured to calculate the frequency change rate adjustment coefficient of each DC transmission system, including: The rotational kinetic energy of the DC receiving AC system is obtained by multiplying the equivalent capacity of the DC receiving AC system by the equivalent inertia time constant of the DC receiving AC system. The rotational kinetic energy of each DC receiving AC system is summed to obtain the total rotational kinetic energy of all DC receiving AC systems. The total rotational kinetic energy of all DC receiving AC systems is then divided by the number of DC transmission systems participating in frequency coordination control to obtain the average rotational kinetic energy of all DC receiving AC systems. The frequency change rate adjustment coefficient of each DC receiving AC system is obtained by dividing the rotational kinetic energy of each DC receiving AC system by the average rotational kinetic energy of all DC receiving AC systems.

16. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 12, characterized in that: The frequency regulation capability coefficient calculation module includes a frequency deviation adjustment capability coefficient calculation module and a frequency change rate adjustment capability coefficient calculation module; The frequency deviation adjustment capacity coefficient calculation module is configured to calculate the product of the downward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the DC receiving-end AC system to obtain the frequency deviation adjustment capacity coefficient of each DC transmission system when a power shortage disturbance occurs in the DC sending-end AC system; when a power surplus disturbance occurs in the DC sending-end AC system, calculate the product of the upward power margin coefficient of each DC transmission system and the frequency deviation adjustment coefficient of the DC receiving-end AC system to obtain the frequency deviation adjustment capacity coefficient of each DC transmission system; Among them, the frequency change rate regulation capability coefficient calculation module is configured to, when a power shortage disturbance occurs in the AC system at the DC sending end, calculate the product of the downward power margin coefficient of each DC transmission system and the frequency change rate regulation coefficient of the AC system at the DC receiving end to obtain the frequency change rate regulation capability coefficient of each DC transmission system; when a power surplus disturbance occurs in the AC system at the DC sending end, calculate the product of the upward power margin coefficient of each DC transmission system and the frequency change rate regulation coefficient of the AC system at the DC receiving end to obtain the frequency change rate regulation capability coefficient of each DC transmission system.

17. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 11, characterized in that: The frequency modulation auxiliary frequency calculation module calculates the frequency modulation auxiliary power of each of the DC power transmission systems connected to the same AC system at the sending end, including: Acquire the frequency of the sending-end AC system in real time, and use the frequency of the sending-end AC system to calculate the frequency deviation value and frequency change rate of the sending-end AC system; The first frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency deviation adjustment capacity coefficient, the proportional coefficient and the frequency deviation value of each DC power transmission system; The second frequency regulation auxiliary power of each DC power transmission system is obtained by multiplying the frequency change rate regulation capability coefficient, the differential coefficient and the frequency change rate of each DC power transmission system; The frequency modulation auxiliary power of each of the direct current power transmission systems is obtained by the sum of the first frequency modulation auxiliary power and the second frequency modulation auxiliary power.

18. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 17, characterized in that: The proportionality coefficient is the ratio of the rated operating power of each of the DC power transmission systems in the current operating mode to the equivalent droop coefficient of each of the DC power transmission systems; The differential coefficient is twice the product of the rated operating power of each of the DC power transmission systems in the current operating mode and the equivalent inertia time constant of each of the DC power transmission systems.

19. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 11, characterized in that: The system actual power determination module determines the actual power of each of the DC power transmission systems, including: For each of the DC power transmission systems, if the alternative power of the DC power transmission system is less than the minimum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the minimum operating power limit of the DC power transmission system; For each of the DC power transmission systems, if the standby power of the DC power transmission system is greater than the maximum operating power limit of the DC power transmission system, determining the actual power of the DC power transmission system to be the maximum operating power limit of the DC power transmission system; For each of the above-mentioned DC transmission systems, if the alternative power of the DC transmission system is not less than the minimum operating power limit of the DC transmission system and not greater than the maximum operating power limit of the DC transmission system, the actual power of the DC transmission system is determined to be the alternative power of the DC transmission system.

20. The DC frequency coordinated control system considering frequency modulation capability as claimed in claim 17, characterized in that: The frequency deviation value of the DC sending-end AC system is equal to the difference obtained by subtracting the frequency rated value of the sending-end AC system from the frequency of the sending-end AC system; The rate of change of the frequency of the sending-end AC system is equal to the differential of the frequency of the sending-end AC system with respect to time.

21. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, the steps of the DC frequency coordinated control method considering the frequency modulation capability as described in any one of claims 1 to 10 are implemented.

22. A computer-readable storage medium having a computer program stored thereon; characterized in that: When the computer program is executed by a processor, the steps of the DC frequency coordinated control method considering the frequency modulation capability as described in any one of claims 1 to 10 are implemented.

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