Flexible frequency modulation method with heavy load and automatic response and remote direct control function

Abstract

The application discloses a large-load flexible frequency modulation method with automatic response and remote direct control functions, relates to the technical field of power systems, and provides two operation modes.Under the automatic response mode, a large-load controller acquires and records the power supply frequency of a grid-connected point, determines a first load power according to the power supply frequency at the current time, determines a second load power according to the comparison result of the power supply frequency at the current time and the power supply frequency at the previous time, and adjusts the target load power by using the minimum value in the first load power and the second load power.Under the remote direct control mode, the large-load controller adjusts the target load power according to a remote direct control instruction, and sends an alarm to a remote control center when the power supply frequency at the current time is less than the lower limit of the frequency range corresponding to the target load power.The technical scheme in the application provides two control modes, can adapt to various application scenarios, considers the influence of the frequency drop rate, and realizes multi-stage fine control of the large load.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, in particular to a large-load flexible frequency modulation method with automatic response and remote direct control functions. BACKGROUND

[0002] Large loads represented by electric vehicle charging stations, electrolytic aluminum plants, electric boilers, etc. bring challenges to the stability of the power supply frequency (50 Hz) of the power system during operation, on the one hand, and on the other hand, large loads have potential flexibility and can provide frequency support to the power system. In addition, in the case of large-scale access and replacement of traditional thermal power by wind power and photovoltaic power, the frequency modulation capability of the power system itself decreases, and non-traditional frequency modulation resources need to be tapped. Large loads are a potential frequency modulation resource, which can participate in frequency modulation as an independent load, or as part of a virtual power plant after aggregation. The current large load represented by electric vehicle charging piles usually passively responds to frequency during operation, i.e. when the frequency drops below a threshold, the charging pile automatically cuts off the charging load. This process is not active frequency modulation, and does not fully reflect the frequency modulation capability of large loads. It is necessary to design appropriate control strategies to tap the potential of large loads to provide frequency modulation for the power system.

[0003] The current large load represented by electric vehicle charging piles does not have a phased fine frequency modulation, but only a 1-0 frequency modulation mode of on-off (i.e. 1-0), which belongs to rough control. The rough control of 1-0 by large loads may cause frequency overshoot of the power system, reduce system stability, and increase the risk of equipment damage. In addition, in the existing frequency modulation mode, the frequency response of large loads only considers the frequency itself, and does not consider the frequency drop rate, which is an important indicator reflecting the current inertia of the power grid. Therefore, in view of the deficiencies in the prior art, it is urgent to propose a large load frequency modulation technology with phased fine frequency modulation capability considering the frequency and frequency drop rate indicators. SUMMARY

[0004] The purpose of the present application is to propose a large load frequency modulation method with phased fine frequency modulation capability, considering the frequency and frequency drop rate indicators, and having automatic response and remote direct control capabilities, in view of the deficiencies in the prior art.

[0005] The technical solution of the present application is to provide a large load flexible frequency modulation method with automatic response and remote direct control functions, which comprises:

[0006] The large load is connected to the power grid at the grid connection point, and the power supply voltage at the grid connection point is obtained. When the power supply voltage at the grid connection point is within a preset range, the large load controller operates in an automatic response mode, which comprises the following steps:

[0007] S1: acquiring a current time power supply frequency at a grid-connected point, and determining a first load power according to a size of the current time power supply frequency, wherein the first load power increases with an increase of the current time power supply frequency;

[0008] S2: comparing the current time power supply frequency with a previous time power supply frequency, and determining a second load power according to a comparison result, wherein if the current time power supply frequency is greater than or equal to the previous time power supply frequency, the second load power is set as a rated power value, and if the current time power supply frequency is less than the previous time power supply frequency, the second load power is determined according to a frequency drop rate, and the second load power decreases with an increase of the frequency drop rate;

[0009] S3: selecting a minimum value between the first load power and the second load power as a target load power, and adjusting a current load power to the target load power;

[0010] When the power supply voltage at the grid-connected point exceeds a preset range, the large load controller operates a remote direct control mode, and the remote direct control mode comprises the following steps:

[0011] The large load controller sets a target load power according to a remote direct control instruction, and adjusts the current load power to the target load power, and acquires a current time power supply frequency at the grid-connected point, and sends an alarm signal to a remote control center when the current time power supply frequency is less than a lower limit of a frequency range corresponding to the target load power.

[0012] Further, in S1, the first load power P1 is determined according to the size of the current time power supply frequency f, and specifically comprises:

[0013] In the large load controller, a first frequency threshold F1 and a second frequency threshold F2 are set in a descending order, a current time power supply frequency f at the grid-connected point is acquired by a measurement module in an interface between the large load and the power grid t , and f t is compared with F1 and F2 respectively, if f t ≥ F1, P1 is set as L, if F2 ≤ f t < F1, P1 is set as 0.5L, if f t < F2, P1 is set as 0, wherein L is a rated power value of the large load.

[0014] Further, S2 specifically comprises:

[0015] The current time power supply frequency f t is compared with a previous time power supply frequency f t-1 recorded in the large load controller, if f t ≥ f t-1 , P2 is set as L, if f t < f t-1, the frequency reduction rate of the current time and the previous time is calculated, and the expression is as follows:

[0016] RoCoF = (f t -f t-1 ) / Δt

[0017] In the formula, RoCoF is the frequency reduction rate, Δt is the time interval of adjacent two measurements, the low threshold R1 and the high threshold R2 are set in order from small to large in the large load controller, and the frequency reduction rate RoCoF is compared with the low threshold R1 and the high threshold R2 respectively, if RoCoF

[0018] Further, S3 specifically includes:

[0019] The first load power P1 and the second load power P2 are combined according to the load minimum principle to obtain the target load power P, and the expression is:

[0020] P = min{P1, P2}

[0021] The large load controller adjusts the current load power to the target load power P, wherein when P = L, the large load controller does not cut the load, when P = 0.5L, the large load controller cuts off half of the load, and when P = 0, the large load controller cuts off all the load.

[0022] Further, the large load controller sets the target load power according to the remote direct control instruction, specifically including:

[0023] The large load controller receives the remote direct control instruction sent by the remote control center, and sets the load power value in the remote direct control instruction as the target load power P, and adjusts the current load power to the target load power P.

[0024] Further, the frequency range corresponding to the target load power P is:

[0025]

[0026] The current power supply frequency f of the grid connection point is obtained t , f t is compared with the lower limit of the frequency range corresponding to P, when P > 0.5L and F2 ≤ f t <F1, it is determined that the remote direct control instruction is not conducive to saving the local frequency that is too low, and the large load controller sends an alarm signal to the remote control center, or when P > 0 and f t <F2, it is determined that the remote direct control instruction is not conducive to saving the local frequency that is too low, and the large load controller sends an alarm signal to the remote control center, and when ft When the frequency is greater than or equal to the lower limit of the frequency range corresponding to P, the heavy load controller does not send an alarm signal to the remote control center.

[0027] Further, after the heavy load is connected to the power grid through the power electronic interface at the grid connection point, a voltage measuring device at the grid connection point measures the supply voltage and feeds back the voltage value to the heavy load controller, and the heavy load controller judges whether the voltage value is within the preset range. When the voltage value is within the preset range, the automatic response mode is run, and when the voltage value exceeds the preset range, the remote direct control mode is run.

[0028] The beneficial effects of the present application are:

[0029] The technical solution of the present application provides two control modes. In the automatic response mode, the influence of the frequency drop rate is considered, the first load power is determined using the current supply frequency, and the second load power is determined using the comparison result of the current supply frequency and the previous supply frequency. When the current supply frequency is less than the previous supply frequency, the second load power is determined using the frequency drop rate, and finally the load power is adjusted according to the minimum value of the first load power and the second load power. In the remote direct control mode, a conflict determination mechanism is provided. When the current supply frequency is less than the lower limit of the frequency range corresponding to the target load power, it is determined that the remote direct control instruction is not conducive to saving the local frequency that is too low, and the remote control center is promptly notified to handle. The beneficial effects of the present application are at least embodied in the following aspects:

[0030] (1) The technical solution of the present application is suitable for load power adjustment of specific heavy load equipment. The specific heavy load equipment has the following common characteristics: i) aggregated by individual loads at the bottom layer, and the behavior of individual loads has randomness, which can be transmitted to the overall level through aggregation; ii) the heavy load equipment requires to meet the power demand within a limited time; for example, electric vehicle charging piles and electric boilers as representatives of heavy loads with potential adjustable capacity.

[0031] (2) The technical solution of the present application has flexibility in control mode, and can freely select the automatic response and remote direct control two operation modes according to actual needs, so that the frequency response of the heavy load adapts to multiple application scenarios, and improves the frequency support capability of the heavy load to the power system.

[0032] (3) The technical solution of the present application supports multi-stage, fine and relatively smooth adjustment of the heavy load, which can adjust the current load power to a more appropriate value, avoiding the overshoot phenomenon caused by the existing 0-1 rigid adjustment.

[0033] (4) The technical solution of the present application simultaneously considers the influence of frequency and frequency drop rate, can enable the large load device to simultaneously cope with the influence of excessively low frequency and excessively high frequency drop rate during operation, thereby effectively supporting power system frequency regulation.

[0034] (5) The technical solution of the present application sets a conflict determination mechanism in the remote direct control mode, the conflict determination mechanism can timely inform the remote control center to process when the power supply frequency is less than the lower limit of the frequency range corresponding to the target load power at the current moment, so that the large load can support the power system to adjust the remote frequency while not deteriorating the local frequency. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above and / or additional aspects of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0036] Figure 1 is a schematic flow chart of a large load flexible frequency regulation method with automatic response and remote direct control functions according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0038] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0039] As shown in Figure 1 The present embodiment provides a large load flexible frequency regulation method with automatic response and remote direct control functions, comprising:

[0040] The large load is connected to the power grid through a power electronic interface at a grid connection point (the grid connection point of the large load and the power grid is the grid connection point), the power supply voltage is measured through a voltage measurement device at the grid connection point, the power supply voltage at the grid connection point is obtained, the voltage value is fed back to the large load controller by the voltage measurement device, the large load controller judges whether the voltage value is within a preset range, when the power supply voltage at the grid connection point is within the preset range, the large load controller runs an automatic response mode, when the power supply voltage at the grid connection point exceeds the preset range, the large load controller runs a remote direct control mode.

[0041] In this embodiment, the local power supply frequency of the power grid refers to the power supply frequency at the current grid connection point obtained by the measurement module in the interface between the large load and the power grid, and the global power supply frequency refers to the sum of the grid connection point frequencies of multiple different regions; where the large load is a whole composed of multiple small loads connected in parallel.

[0042] In this embodiment, voltage fluctuations occur during the power consumption of high-load equipment. These voltage fluctuations at the grid connection point are affected by load changes, line impedance, and local grid configuration. When voltage fluctuations exceed a preset range (e.g., below 380V or above 420V), local imbalances or anomalies may occur in the grid, affecting overall operation. In such cases, load adjustments need to be made based on the overall grid situation to restore local or overall grid stability. Selecting the operating mode based on voltage fluctuations effectively ensures the safety of power equipment, maintains grid stability, improves power supply quality, and addresses potential impacts from large load connections, reducing the risk of equipment damage.

[0043] The high-load controller operates in automatic response mode, which adjusts the load power according to the local power supply frequency, specifically including the following steps:

[0044] S1: Obtain the current power supply frequency f at the grid connection point where the high load is connected to the power grid. t According to the current power supply frequency f t The magnitude of the load determines the first load power P1, where the first load power P1 varies with the current power supply frequency f. t It increases as it increases.

[0045] In the high-load controller, the first frequency threshold F1 and the second frequency threshold F2 are set sequentially from largest to smallest. The high-load controller obtains the current frequency f at the grid connection point (i.e., the interface point between the high-load and the grid) through the measurement module in the interface between the high-load and the grid. t Where t represents the current time, and the frequency f from the previous time is... t Compare it with the first frequency threshold F1 and the second frequency threshold F2 respectively. If the power supply frequency f t If the load is greater than or equal to the first frequency threshold F1, then the value of the first load power P1 is set to L, which means the condition of not cutting off the load is met. L represents the rated power of the large load. If the power supply frequency f t If the load is less than the first frequency threshold F1 and greater than or equal to the second frequency threshold F2, i.e., the condition of cutting off half of the load has been met, then the value of the first load power P1 is set to 0.5L. If the power supply frequency f t If the load is less than the second frequency threshold F2, then the value of the first load power P1 is set to 0, which means that the condition for completely cutting off the load has been met.

[0046] In this embodiment, the heavy load is generally connected to the power grid through a power electronic interface, which has the function of measuring the power supply frequency at the grid connection point. The measured power supply frequency at the grid connection point is also the local frequency of the power grid (the frequency of the power grid at different locations should be uniform 50Hz, but due to transmission loss, load variation and other factors in the system, the frequency in the local area will deviate, therefore, the local frequency of the power grid refers to the real-time power grid frequency at the access point).

[0047] S2: Compare the current power supply frequency with the previous power supply frequency, and determine the second load power according to the comparison result, wherein if the current power supply frequency is greater than or equal to the previous power supply frequency, the second load power is set as the rated power value, and if the current power supply frequency is less than the previous power supply frequency, the second load power is determined according to the frequency drop rate, and the second load power decreases with the increase of the frequency drop rate.

[0048] Compare the current power supply frequency f t with the previous power supply frequency f t-1 recorded in the heavy load controller, if the power supply frequency f t is greater than or equal to the power supply frequency f t-1 , the value of the second load power P2 is set as L; if the power supply frequency f t is less than the power supply frequency f t-1 , the frequency drop rate between the current time and the previous time is compared, and the expression is as follows:

[0049] RoCoF=(f t -f t-1 ) / Δt

[0050] In the formula, RoCoF is the frequency drop rate, and Δt is the time interval between adjacent two measurements;

[0051] In the heavy load controller, the low threshold R1 and the high threshold R2 are set in order from small to large, and the frequency drop rate is compared with the low threshold R1 and the high threshold R2 respectively, if RoCoF

[0052] In this embodiment, the setting of the low threshold R1 and the high threshold R2 depends on the power grid safety and stability operation standard formulated by the power grid dispatching, for example, when Δt=0.5s, R1=1.0Hz / s, R2=2.0Hz / s; when Δt=1.0s, R1=0.5Hz / s, R2=1.0Hz / s.

[0053] S3: select the minimum value of the first load power P1 and the second load power P2 as the target load power P, and the large load controller adjusts the current load power to the target load power.

[0054] After the first load power P1 and the second load power P2 are calculated by S1 and S2 respectively, the first load power P1 and the second load power P2 are combined according to the minimum load principle to obtain the target load P, and the expression is:

[0055] P = min{P1, P2}

[0056] In the automatic response mode, the large load controller adjusts the current load power to the target load power P, that is, the large load is controlled to P, wherein when P = L, the large load controller does not cut the load, when P = 0.5L, the large load controller randomly cuts half of the load, and when P = 0, the large load controller cuts all the load. In the embodiment, the large load is the whole composed of a plurality of small loads in parallel, when P = L, all the small loads are retained, when P = 0.5L, the large load controller randomly cuts half of the small loads, and when P = 0, the large load controller cuts all the small loads.

[0057] In the embodiment, the large load controller can flexibly adjust the actual load output according to the target load power, so as to better respond to the change of the power supply frequency of the power grid, help the power grid maintain the frequency stability, and realize the adjustment of the power supply frequency. According to the minimum value operation rule, the combined load P obtained by S3 can take values of L, 0.5L and 0, which respectively correspond to no load cutting, cutting half of the load and cutting all the load. In the embodiment, the condition of not cutting the load is P1 = L and P2 = L, that is, the frequency f > 49.7 Hz and the condition of not cutting the load set by S2 is also met (f > 49.7 Hz and RoCoF < R1); the condition of cutting half of the load is that the condition of cutting half of the load set by S1 is met and the condition of cutting all the load set by S2 is not met, or the condition of cutting half of the load set by S2 is met and the condition of cutting all the load set by S1 is not met; and the condition of cutting all the load is that the condition of cutting all the load set by S1 is met or the condition of cutting all the load set by S2 is met. t+1 t Or RoCoF < R1); the condition of cutting half of the load is that the condition of cutting half of the load set by S1 is met and the condition of cutting all the load set by S2 is not met, or the condition of cutting half of the load set by S2 is met and the condition of cutting all the load set by S1 is not met; and the condition of cutting all the load is that the condition of cutting all the load set by S1 is met or the condition of cutting all the load set by S2 is met.

[0058] The large load controller operates in the remote direct control mode, which adjusts the load power according to the global power supply frequency, and specifically includes the following steps:

[0059] The large load controller adjusts the size of the target load power P according to the remote direct control instruction, and simultaneously acquires the current power supply frequency f of the grid connection point t When the power supply frequency f t ​When the lower limit of the frequency range corresponding to the target load P is less than the lower limit, it is determined that the remote direct control instruction is not conducive to saving the local excessively low frequency, and the large load controller sends an alarm signal to the remote control center. When the power supply frequency f t is greater than or equal to the lower limit of the frequency range corresponding to the target load P, the large load controller does not need to send an alarm signal to the remote control center.

[0060] In the remote direct control mode, the large load controller receives the remote direct control instruction and controls the magnitude of the target load P according to the value of the load power set in the remote direct control instruction, that is, adjusts the target load P to the value of the load power set in the remote direct control instruction; the set frequency range corresponding to the target load P is:

[0061]

[0062] In the formula, when P > 0.5L, the corresponding frequency is in the range greater than or equal to F1 and less than or equal to 50 Hz; when P = 0.5L, the corresponding frequency is in the range greater than or equal to F2 and less than F1; when P < 0.5L, the corresponding frequency is in the range greater than or equal to 0 and less than F2.

[0063] Obtain the power supply frequency f of the connection point at the current moment t , and compare the power supply frequency f t with the lower limit of the frequency range corresponding to P. When the power supply frequency f t is less than the lower limit of the frequency range corresponding to the target load P, that is, when it satisfies P > 0.5L and F2 ≤ f t < F1 or satisfies when P > 0 and f t < F2, it is determined that the remote direct control instruction is not conducive to saving the local excessively low frequency, and the large load controller sends an alarm signal to the remote control center to inform the remote control center of the situation of the local excessively low frequency. During this process, the large load controller still accepts the remote direct control instruction and adjusts the target load P according to the value of the load power set in the remote direct control instruction; when the power supply frequency f t is greater than or equal to the lower limit of the frequency range corresponding to the target load P, the large load controller does not need to send an alarm signal to the remote control center, and accepts the remote direct control instruction and adjusts the target load P according to the value of the load power set in the remote direct control instruction.

[0064] In this embodiment, the first frequency threshold F1 and the second frequency threshold F2 are set according to the grid safety and stable operation standard formulated by the actual power grid dispatching, and can be set as: F1 = 49.7 Hz, F2 = 49.5 Hz.

[0065] In this embodiment, after the heavy load is connected to the power grid through the power electronic interface, the user can also select the operation mode of the heavy load controller according to the actual scheduling demand through the heavy load management and control platform (the heavy load management and control platform is a system for centralized management and monitoring of heavy load equipment, and the heavy load controller is in communication connection with the management and control platform). When the heavy load controller needs to adjust the load power according to the local power supply frequency of the power grid, the automatic response mode is selected, and when the heavy load controller needs to adjust the load power according to the global power supply frequency of the power grid, the remote direct control mode is selected. The heavy load controller works according to the logic of the mode selected by the user. Wherein, before the heavy load is running, it will access the heavy load management and control platform or the system energy management platform containing the heavy load through electronic circuits, other auxiliary equipment and communication network modules. The user can set the operation mode of the heavy load on the corresponding platform according to the actual demand before use, and can also change the operation mode on the platform after setting.

[0066] The technical solution of the present application includes automatic response and direct control mode (direct control for short) scheduled by the power grid, which is suitable for heavy load represented by electric vehicle charging, and requires that the heavy load equipment can collect the frequency of the grid point (i.e. the local frequency of the power grid) in real time, and has local data processing and calculation and load control capability (which can be realized by a heavy load controller). The heavy load can operate at the rated frequency (50Hz) of the power grid, and the heavy load controller (such as the load controller built-in in the charging pile) can be freely switched between the automatic response mode and the remote direct control mode.

[0067] In this embodiment, when switched to the automatic response mode, the heavy load controller can control the load according to the control logic in S1 to S3. The significance of automatic response is that the heavy load can respond in real time according to the measured local frequency information, providing support for the power grid frequency without the need for communication with the power grid scheduling or the third party, and without occupying the calculation resources of the power grid scheduling. When switched to the remote direct control mode, the heavy load controller is given control instructions by the power grid scheduling or the third party (such as the virtual power plant operator). The instructions can be to completely cut off the load, reduce the load by a given percentage, or not to cut off the load. The significance of the direct control mode is that the power grid scheduling masters the global frequency information of the power grid, which can be used for global optimization and flexible regulation and control of load resources.

[0068] In the remote direct control mode, when the direct control instruction is not conducive to saving the excessively low local frequency, the large load controller determines that the direct control instruction and the local frequency are in conflict, and immediately informs the remote dispatch center (grid dispatch or third party) to intervene in the processing. Specifically, for example, when the locally measured frequency is excessively low and needs to be completely cut off, but the direct control instruction does not require cutting off the load or only requires cutting off part of the load, the large load controller determines that there is a conflict, and immediately informs the remote dispatch center to intervene in the processing. Conversely, for example, when the locally measured frequency is normal, and the remote direct control instruction requires completely cutting off the load, it is not determined as a conflict, and the remote direct control instruction is executed, because at this time, a remote node in the entire grid may have an excessively low frequency, and the load needs to be cut off.

[0069] The steps in the present application can be adjusted in sequence, combined, and reduced according to actual needs.

[0070] The units in the device of the present application can be combined, divided, and reduced according to actual needs.

[0071] Although the present application is disclosed in detail with reference to the drawings, it should be understood that the description is merely exemplary and is not intended to limit the application. The scope of protection of the present application is defined by the appended claims, and can include various modifications, improvements and equivalent arrangements made to the application without departing from the scope and spirit of the present application.

Claims

1. A flexible frequency modulation method for heavy load with automatic response and remote direct control functions, characterized in that, The method comprises: The heavy load is connected to the power grid at the grid connection point, and the power supply voltage at the grid connection point is obtained; when the power supply voltage at the grid connection point is within a preset range, the heavy load controller operates in an automatic response mode, and the automatic response mode comprises the following steps: S1: obtaining the current power supply frequency at the grid connection point, and determining a first load power according to the size of the current power supply frequency, wherein the first load power increases with the increase of the current power supply frequency; Specifically, in the large load controller, the first frequency threshold F1 and the second frequency threshold F2 are set in descending order, and the current power supply frequency f of the grid point is obtained by the measurement module in the interface between the large load and the grid t , and f t is compared with F1 and F2 respectively, if f t ≥ F1, P1 is set as L, if F2 ≤ f t < F1, P1 is set as 0.5L, if f t < F2, P1 is set as 0, wherein L is the rated power value of the large load; S2: comparing the current power supply frequency with the previous power supply frequency, and determining a second load power according to the comparison result, wherein if the current power supply frequency is greater than or equal to the previous power supply frequency, the second load power is set as a rated power value, and if the current power supply frequency is less than the previous power supply frequency, the second load power is determined according to a frequency drop rate, and the second load power decreases with the increase of the frequency drop rate; Specifically, the current power supply frequency f t The power supply frequency f recorded in the high-load controller at the previous moment t-1 Compare them, if f t ≥f t-1 Then let P2 = L, if f t <f t-1 The rate of frequency decrease between the current time and the previous time is calculated using the following expression: RoCoF = (f t -f t-1 ) / Δt In the formula, P2 is the second load power, RoCoF is the frequency drop rate, Δt is the time interval of adjacent two measurements, the low threshold R1 and the high threshold R2 are set in the heavy load controller in the order from small to large, and the frequency drop rate RoCoF is compared with the low threshold R1 and the high threshold R2 respectively, if RoCoF < R1, P2 = L is set, if R1 ≤ RoCoF < R2, P2 = 0.5L is set, and if RoCoF ≥ R2, P2 = 0 is set; S3: selecting the minimum value of the first load power and the second load power as a target load power, and adjusting the current load power to the target load power; When the power supply voltage at the grid connection point exceeds the preset range, the heavy load controller operates in a remote direct control mode, and the remote direct control mode comprises the following steps: The heavy load controller sets the target load power according to the remote direct control instruction, adjusts the current load power to the target load power, and obtains the current power supply frequency at the grid connection point; when the current power supply frequency is less than the lower limit of the frequency range corresponding to the target load power, an alarm signal is sent to the remote control center.

2. The method of claim 1, wherein the method is characterized by, The S3 specifically comprises: The first load power P1 and the second load power P2 are combined according to the load minimum principle to obtain a target load power P, and the expression is: P = min{P1, P2} The heavy load controller adjusts the current load power to the target load power P, wherein when P = L, the heavy load controller does not cut the load, when P = 0.5L, the heavy load controller cuts half of the load, and when P = 0, the heavy load controller cuts all the load.

3. The method of claim 1, wherein the method is characterized by, The heavy load controller sets the target load power according to the remote direct control instruction, and specifically comprises: The heavy load controller receives the remote direct control instruction sent by the remote control center, and sets the load power value in the remote direct control instruction as the target load power P, and adjusts the current load power to the target load power P.

4. The method of claim 1, wherein the method is characterized by, The frequency range corresponding to the target load power P is: Obtain the current time point of the grid connection point supply frequency f t Compare f t with the lower limit of the frequency range corresponding to P, when P>0.5L and F2≤f t When F1, it is determined that the remote direct control instruction is not conducive to saving the local frequency that is too low, and the heavy load controller sends an alarm signal to the remote control center, or, when P>0 and f t When F2, it is determined that the remote direct control instruction is not conducive to saving the local frequency that is too low, and the heavy load controller sends an alarm signal to the remote control center, when f t When f is greater than or equal to the lower limit of the frequency range corresponding to P, the heavy load controller does not send an alarm signal to the remote control center.

5. The method of claim 1, wherein the method is characterized by, The large load is connected to the power grid through a power electronic interface, a voltage measuring device at the grid connection point measures the supply voltage and feeds back the voltage value to the large load controller, the large load controller judges whether the voltage value is within a preset range, when the voltage value is within the preset range, an automatic response mode is run, and when the voltage value exceeds the preset range, a remote direct control mode is run.

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