Pre-control method and device for safe and stable operation mode of power grid

Abstract

The application relates to a power grid safety and stability operation mode pre-control method and device; the method comprises the following steps: establishing a plurality of sets of operation mode simulation models according to preset operation data; determining all risks under each set of operation mode simulation models; simulating the development of power grid safety and stability operation mode pre-control for all scanned risks to obtain simulation pre-control results meeting stability criteria; and determining corresponding pre-control parameters according to the simulation pre-control results of each set of operation mode. The scheme of the application formulates a safety and stability operation mode pre-control method, effectively improves the safety and stability of regional power grid operation, reduces the influence of faults on the interconnection of AC and DC receiving ends in heavy load areas, guarantees the safety and stability of the power grid, and avoids the situation that DC blocking, AC system voltage collapse and other large influences are caused by faults.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power grid safety and stability control, in particular to a pre-control method and device for a power grid safety and stability operation mode. BACKGROUND

[0002] A large power transmission network is composed of a main grid (referred to as a main network) and a plurality of regional grids connected thereto. The regional networks can be divided into three categories according to their positions in the power system, namely, a sending-end grid, an intermediate grid, and a receiving-end grid. The receiving-end grid refers to a regional grid at one end of the main grid, which is mainly used for power reception. The receiving-end grid has a total generation capacity smaller than its load capacity, resulting in a need for power reception from other grids to ensure the balance between power generation and consumption.

[0003] Power grid safety and stability control refers to a control method for restoring the system to a normal operation state by executing various emergency control measures when the power system is in an emergency state. High-voltage direct current transmission is a high-power long-distance direct current transmission method that takes advantage of the advantages of stable direct current, such as no inductive reactance, capacitive reactance, and no synchronization problem; the transmission process is direct current.

[0004] The safe and stable operation of the power system plays a crucial role in the operation of the power grid, ensuring the stable supply of electricity and supporting the stable and development of the economy and society. With the rapid development and application of direct current transmission technology, some regions with weak power supply and lack of power supply have connected to long-distance large-capacity direct current feed-in to adapt to the rapid growth of industrial load. However, before the power grid structure is perfected or during the maintenance of key lines, the heavy load area of the alternating current and direct current receiving end may still have multiple operation risks, and even the shedding of heavy load and the blocking of direct current may have a significant impact on the operation of other regional power grids. Therefore, for the heavy load area of the alternating current and direct current receiving end, in the case of imperfect power grid structure or key line maintenance, the safe and stable operation of the power grid can be ensured by the pre-control method, meeting the requirements of the "Power System Safety and Stability Guidelines", and avoiding the impact of the expansion of the fault when a fault occurs. Direct current blocking refers to the stopping of power transmission by the direct current transmission system.

[0005] In related technologies, the existing safety and stability control strategies and pre-control methods are mostly designed for the stability problems existing in part of the system or are only formulated for the heavy load area of the direct current receiving end. There is no pre-control method for the safety and stability of the area that is both the receiving end of the alternating current system and the receiving end of the direct current system and directly connected to the heavy load. SUMMARY

[0006] To at least partially overcome the problems in the related art, the present application provides a pre-control method and device for a power grid safety and stability operation mode.

[0007] According to a first aspect of the embodiments of the present application, a method for pre-control of safe and stable operation mode of a power grid is provided, comprising:

[0008] establishing simulation models of a plurality of operation modes according to preset operation data;

[0009] determining all risks in the operation mode for each simulation model of the operation mode;

[0010] simulating pre-control of safe and stable operation mode of the power grid for all scanned risks to obtain simulation pre-control results meeting stability criteria; the stability criteria are conditions for the pre-controlled results to meet the condition that the AC / DC system can be restored to stability after a fault;

[0011] determining pre-control parameters corresponding to each operation mode according to the simulation pre-control results.

[0012] Further, the preset operation data is annual typical operation mode data.

[0013] The operation mode includes a dry large mode, a dry small mode, a wet large mode, and a wet small mode.

[0014] The simulation model includes each operation mode and all related line maintenance modes and main transformer maintenance modes corresponding to the operation mode.

[0015] Further, the determination of all risks in the operation mode includes:

[0016] scanning the risk of the AC / DC receiving end accessing a heavy load area under the given load and DC power condition of the operation mode;

[0017] numbering the risks under each operation mode.

[0018] Further, the risks include at least one of the following: N-1 fault, N-2 fault, N-1 fault under maintenance mode, and N-2 fault under maintenance mode.

[0019] Further, the simulation of pre-control of safe and stable operation mode of the power grid includes:

[0020] performing simulation tests on faults corresponding to each risk under the condition that the DC is shut down;

[0021] performing simulation tests on faults corresponding to each risk under the condition that the DC is restored to operation.

[0022] Further, the stability criteria include at least one of the following: no overload of lines or main transformers, no instability of power angle, no instability of system steady-state voltage, no instability of system steady-state frequency, no instability of system transient voltage, no DC lockout, and no more than a preset threshold of DC commutation failure times.

[0023] Further, in the DC outage case, simulation tests are carried out for the faults corresponding to each risk, including:

[0024] In the DC outage case, simulation tests are carried out for the fault corresponding to the risk i;

[0025] By gradually reducing the amount of load connected by the AC-DC receiving end until the system can recover to stability after the fault corresponding to the risk i occurs, the load amount Pi at this time is recorded.

[0026] Further, in the DC recovery operation case, simulation tests are carried out for the faults corresponding to each risk, including:

[0027] In the case of the load amount Pi, the DC operation is recovered;

[0028] By gradually reducing the DC power until the system can recover to stability after the fault corresponding to the risk i occurs, the DC power Pdci at this time is recorded.

[0029] Further, the determining of the corresponding pre-control parameter according to the simulation pre-control result includes:

[0030] The final load amount Pload of the mode pre-control is determined as: Pload = min (P1, P2…Pi);

[0031] The final DC power Pdc of the mode pre-control is determined as: Pdc = min (Pdc1, Pdc2…Pdci).

[0032] According to a second aspect of the embodiments of the present application, a pre-control device for a safe and stable operation mode of a power grid is provided, including:

[0033] A model establishing module is configured to establish a plurality of simulation models of operation modes according to preset operation data;

[0034] A risk determining module is configured to determine all risks in each simulation model of the operation mode;

[0035] A simulation pre-control module is configured to simulate the pre-control of the safe and stable operation mode of the power grid for all the scanned risks, and obtain simulation pre-control results meeting a stability criterion; the stability criterion is a condition that the effect after the pre-control meets the condition that the AC-DC system can recover to stability after a fault;

[0036] A parameter determining module is configured to determine the corresponding pre-control parameter for each operation mode according to the simulation pre-control result.

[0037] The technical scheme provided by the embodiments of the present application has the following beneficial effects:

[0038] The scheme of the present application effectively improves the safety and stability of the regional power grid operation, reduces the influence of faults on the interconnection of the receiving end of AC and DC to the heavy load area, ensures the safe and stable operation of the power grid, and avoids the situation of large influence such as DC blocking and voltage collapse of AC system caused by faults.

[0039] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0041] Figure 1 is a flow chart of a power grid safety and stability operation mode pre-control method according to an exemplary embodiment.

[0042] Figure 2 is a structural block diagram of a power grid safety and stability operation mode pre-control device according to an exemplary embodiment. DETAILED DESCRIPTION

[0043] The exemplary embodiments will be described in detail hereinafter with reference to the attached drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they only represent examples of methods and apparatuses consistent with some aspects of the present application as detailed in the appended claims.

[0044] To further detail the technical solutions of the present application, first, the technical status of the art will be specifically explained.

[0045] Because the terminal user power load decreases (for example, large power equipment failure or large area line failure power failure), the power generation of the power plant steam turbine generator exceeds the amount delivered to the user, at which time the power plant is required to reduce the power generation to a value suitable for the actual load. Or the internal reason of the power plant, the grid outlet breaker trips suddenly, the steam turbine generator load suddenly drops to almost zero, these execution actions of the power plant are called load rejection.

[0046] Load shedding is divided into two kinds, one is active load shedding: when the active power provided by the power grid is greater than the active power required by the system, the active load shedding is carried out to improve the power supply quality of the power grid. The other is fault load shedding. In addition to the abnormality of the power grid, the tripping of the main switch of the generator and the tripping of the main steam valve of the steam turbine are the causes of the accident. When the power station suddenly sheds a large amount of load, the steam flow of the secondary loop decreases sharply, and the temperature and pressure of the primary loop coolant rise rapidly. This is the load shedding accident.

[0047] Before the power grid architecture is perfect or in the case of key line maintenance, the AC-DC receiving end heavy load area may still have various operation risks, and even the shedding of heavy load and the blocking of DC may have a significant impact on the operation of other regional power grids.

[0048] With the rapid economic development and the maturity of DC power transmission technology, more and more such scenarios will occur, that is, the DC receiving end region has the characteristics of weak power support at the end of the AC system and heavy load access. Such scenarios may be caused by the fact that the power grid construction lags behind the speed of economic development and load growth, or by key line maintenance. It is necessary to develop appropriate safety and stability operation mode pre-control methods for such scenarios.

[0049] The existing safety and stability operation mode pre-control method does not simultaneously consider the DC system, the AC system and the heavy load characteristics, which may lead to serious consequences such as low voltage, voltage collapse and DC blocking after partial failure, and even cause the accident to expand to the entire power system collapse.

[0050] In view of the above problems, the present application aims to provide a safety and stability operation mode pre-control method for AC-DC receiving end heavy load. The method considers the scenario of AC-DC receiving end heavy load access, and combines the power grid characteristics of the DC receiving end, the weak power support at the end of the AC system and the heavy load access region, which can effectively guarantee the safety and stability operation of the regional power grid and avoid the problems of DC blocking, transient low voltage and voltage collapse after regional failure.

[0051] Figure 1 A flowchart of a safety and stability operation mode pre-control method of a power grid according to an exemplary embodiment is shown. The method can include the following steps:

[0052] Establishing a plurality of sets of operation mode simulation models according to preset operation data;

[0053] For each set of operation mode simulation model, determining all risks under the operation mode;

[0054] For all the scanned risks, simulate the safety and stability operation mode pre-control of the power grid to obtain the simulation pre-control result that meets the stability criterion; the stability criterion is the condition that the effect after pre-control meets the stable condition of the AC-DC system after failure.

[0055] For each set of operation modes, the corresponding pre-control parameters are determined according to the simulation pre-control results.

[0056] The scheme of the present application effectively improves the safety and stability of the regional power grid operation, reduces the influence of faults on the AC receiving end access to the heavy load area, ensures the safe and stable operation of the power grid, and avoids the situation of large influence such as DC blocking, AC system voltage collapse caused by faults.

[0057] It should be understood that, although Figure 1 The steps in the flowchart of the present application are displayed in sequence according to the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps in the flowchart of the present application can include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with other steps or sub-steps or stages of other steps.

[0058] In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0059] In some embodiments, the preset operation data is annual typical operation mode data.

[0060] The operation modes include: dry large mode, dry small mode, wet large mode, and wet small mode.

[0061] The simulation model includes each set of operation modes, and all related line maintenance modes and main transformer maintenance modes corresponding thereto.

[0062] Specifically, according to the annual typical operation mode data, four sets of operation modes, KD (dry large), KX (dry small), FD (wet large), and FX (wet small), and simulation models of all related line maintenance modes and main transformer maintenance modes are established. Under the load and DC power conditions of the aforementioned given mode data, the risks of AC receiving end access to the heavy load area are scanned, including N-1 fault, N-2 fault, N-1 fault under maintenance mode, and N-2 fault under maintenance mode, and the occurrence of AC / DC system instability.

[0063] It should be noted that the "annual typical operation mode data" is general data in the industry, which is calculated and provided by the dispatching institution every year, and is used for various planning and test reference. The data is large in amount and involves many contents, and will not be described herein. The four operation modes are all part of the aforementioned annual typical operation mode data, and the annual typical operation mode data will include the four operation mode data.

[0064] The "simulation model" refers to modeling based on the aforementioned data using power system analysis software. Because even if the given data is the same, there will still be slight differences when modeling using different software. The scheme of the present application is not directed to a specific software, and can be implemented using various analysis software commonly used in the industry. Therefore, the present application uses "simulation model" as a general term. Based on the simulation model established as described above, the general power system simulation analysis software mainly functions to simulate and scan all related risks, such as setting N-1 fault, N-2 fault and then performing simulation calculation.

[0065] In some embodiments, the determining all risks in the operation mode includes:

[0066] Scanning the risk of the receiving end of AC and DC accessing a heavy load area under the given load and DC power condition;

[0067] Numbering the risks in each operation mode respectively.

[0068] Specifically, the risks in the dry large operation mode are numbered as KD1, KD2…, the risks in the dry small operation mode are numbered as KX1, KX2…, the risks in the wet large operation mode are numbered as FD1, FD2…, and the risks in the wet small operation mode are numbered as FX1, FX2…

[0069] In some embodiments, the risks include at least one of the following: N-1 fault, N-2 fault, N-1 fault in maintenance mode, and N-2 fault in maintenance mode.

[0070] The N-1 fault refers to, in a normal operation mode, any one element in the power system being fault-free or being disconnected due to a fault, the power system being able to maintain stable operation and normal power supply, other elements not being overloaded, and the ability of the system to maintain stability and continuous power supply.

[0071] The N-2 fault refers to, in a normal operation mode, any two elements in the power system being fault-free or being disconnected due to a fault, the power system being able to maintain stable operation and normal power supply, other elements not being overloaded, and the ability of the system to maintain stability and continuous power supply.

[0072] In some embodiments, the simulation of the power grid safety and stability operation mode pre-control includes: in the case of DC outage, simulation tests are performed for faults corresponding to each risk; and in the case of DC recovery, simulation tests are performed for faults corresponding to each risk.

[0073] For all the scanned risks, power system analysis software is used to perform power grid safety and stability operation mode pre-control, and the effect of the pre-control should meet the requirements that the AC / DC system can recover to stability after the fault.

[0074] In some embodiments, the stability criterion includes at least one of the following: the line or main transformer is not overloaded, the power angle is not unstable, the system steady-state voltage is not unstable, the system steady-state frequency is not unstable, the system transient voltage is not unstable, the DC is not blocked, and the number of DC commutation failures is not greater than a preset threshold. The preset threshold can be set to a specific value according to the actual application scenario, such as 1 in some embodiments.

[0075] The stability criterion mainly includes: 1) the line or main transformer is not overloaded after the fault; 2) the power angle is not unstable after the fault; 3) the system steady-state voltage is not unstable after the fault, i.e., the system steady-state voltage can maintain operation between 0.95-1.05pu after the fault; 4) the system steady-state frequency is not unstable after the fault, i.e., the system steady-state frequency can maintain between 49.8-50.2Hz after the fault; 5) the system transient voltage is not unstable after the fault, i.e., the bus voltage can recover to more than 0.75pu within 1s after the fault; 5) the DC is not blocked after the fault; and 6) the number of DC commutation failures after the fault is not greater than 1.

[0076] It should be noted that "power angle not unstable" is a commonly used technical term in the art, and those skilled in the art can clearly understand the meaning of the technical term, so the present application does not repeat it.

[0077] In some embodiments, in the case of DC outage, simulation tests are performed for faults corresponding to each risk, including:

[0078] In the case of DC outage, simulation tests are performed for faults corresponding to risk i;

[0079] By gradually reducing the amount of load connected to the AC / DC receiving end until the system can recover to stability after the fault corresponding to risk i occurs, the load amount Pi at this time is recorded.

[0080] For example, in the case of the dry large operation mode, for the i-th risk (i is the scanned risk number in the dry large operation mode), in the case of DC outage, the simulation test is performed for the fault corresponding to the i-th risk, and the load connected to the receiving end of the AC / DC system is gradually reduced (the original mode data load is taken as the initial value) until the system can recover to stability after the fault corresponding to the i-th risk occurs. The load Pi at this time is recorded. The "recovery to stability" here is based on the case of DC outage. The simulation pre-treatment steps of the other three operation modes are the same as those of the dry large operation mode and will not be repeated.

[0081] In some embodiments, in the case of DC recovery, simulation tests are performed for the faults corresponding to each risk, including:

[0082] In the case of the load Pi, the DC operation is recovered.

[0083] The DC power is gradually reduced until the system can recover to stability after the fault corresponding to the i-th risk occurs, and the DC power Pdci at this time is recorded.

[0084] For example, in the case of the dry large operation mode, in the case of the load Pi, the DC operation is recovered, and the DC power is gradually reduced (the DC rated power is taken as the initial value) until the system can recover to stability after the fault corresponding to the i-th risk occurs. The DC power Pdci at this time is recorded. The "recovery to stability" here is different from the previous premise condition, as the DC operation has been recovered. The simulation pre-treatment steps of the other three operation modes are the same as those of the dry large operation mode and will not be repeated.

[0085] In some embodiments, the determination of the corresponding pre-control parameters according to the simulation pre-control results comprises:

[0086] The final load Pload of the mode pre-control is determined as Pload = min (P1, P2, …, Pi).

[0087] The final DC power Pdc of the mode pre-control is determined as Pdc = min (Pdc1, Pdc2, …, Pdci).

[0088] Wherein, the min (*) function is the minimum value function.

[0089] The determined Pload and Pdc are the operation mode pre-control scheme under the mode data.

[0090] The so-called pre-control scheme refers to a scheme that can enable the safe and stable operation of the power system under certain specific conditions. The scheme provided by the present patent is to control the sizes of Pload (the final load size) and Pdc (the DC operation power size) to enable the regional power grid to meet the safe and stable operation criteria of the power grid.

[0091] The above steps are described by taking the dry large operation mode as an example, and the above operations are repeated for the remaining three sets of operation mode data of dry small mode, abundant large mode, abundant small mode, and the like, until all risks have corresponding safe and stable operation mode pre-control schemes.

[0092] The method of the application is mainly aimed at four sets of typical operation mode data commonly used in power grids, and a mode pre-control scheme applicable to most cases is obtained. For the working condition under specific operation mode data, the mode pre-control scheme under the specific operation mode data can also be obtained by using the method, and it is necessary to note that the risk under the worst condition is generally considered to ensure that the scheme can meet the fault ride-through under the operation mode data.

[0093] The safe and stable operation mode pre-control method of the AC / DC receiving end heavy load provided by the application has the following key points: 1) comprehensively consider the characteristics of the heavy load connected to the AC / DC receiving end region, especially the risk caused by the rapid growth of the load, the lag of the grid structure construction, or the maintenance condition; 2) the high DC power, heavy load, weak power support at the end of the AC line, and other multi-factor coupling can easily lead to stability problems, and the safe and stable operation mode pre-control needs to be considered and formulated.

[0094] The scheme of the application has the following beneficial effects: by formulating the safe and stable operation mode pre-control method, the safety and stability of the regional power grid operation are effectively improved, the influence of the fault on the heavy load region connected to the AC / DC receiving end is reduced, the safe and stable operation of the power grid is ensured, and the situation of large influence such as DC blocking and voltage collapse of the AC system caused by the fault is avoided.

[0095] Figure 2 is a structural block diagram of a power grid safe and stable operation mode pre-control device according to an exemplary embodiment. Referring to Figure 2 , the device comprises:

[0096] a model establishing module, configured to establish simulation models of a plurality of sets of operation modes according to preset operation data;

[0097] a risk determining module, configured to determine all risks under each set of operation mode simulation model;

[0098] a simulation pre-control module, configured to simulate the power grid safe and stable operation mode pre-control for all the scanned risks, and obtain simulation pre-control results meeting the stability criterion; the stability criterion is a condition that the effect after pre-control meets the condition that the AC / DC system can recover to stability after the fault;

[0099] a parameter determining module, configured to determine the corresponding pre-control parameters for each set of operation mode according to the simulation pre-control results.

[0100] As to the apparatus in the above embodiments, the specific steps in which the various modules perform operations have been described in detail in the embodiments related to the method, and will not be elaborated here. The various modules in the above pre-control apparatus can be realized by software, hardware and combinations thereof, in whole or in part. The various modules described above can be embedded in the processor in the computer device in hardware form or independent of the processor in the computer device, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the various modules.

[0101] It can be understood that the same or similar parts in the above embodiments can be mutually referred to, and the content not elaborated in some embodiments can be referred to the same or similar content in other embodiments.

[0102] It should be noted that, in the description of the present application, the terms "first", "second" and the like are used only for descriptive purposes, and should not be construed as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is at least two.

[0103] Any process or method descriptions in flow charts or described elsewhere herein can be understood as representing code modules, segments, or portions of code which include one or more executable instructions for performing specific logic functions or steps in the process, and that the various embodiments of the application include the use of alternative orderings, methods, and / or sequences of these steps or combinations thereof, as can be desired to implement the functions of the present application, and as would be understood by those of ordinary skill in the art. Additionally, the descriptions of the various embodiments of the present application have been presented for purposes of illustration and description, and are not intended to be exhaustive or to limit the present application to the precise forms disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art.

[0104] It should be understood that portions of the present application can be realized with hardware, software, firmware or a combination thereof. In the above embodiments, a plurality of steps or methods can be realized by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if realized by hardware, and as in another embodiment, it can be realized by any one or a combination of the following technologies known in the art: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) and the like.

[0105] Those of ordinary skill in the art can understand that all or part of the steps carried out by the above-mentioned embodiment methods can be instructed by a program to complete the relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, it includes one of the steps of the method embodiments or a combination thereof.

[0106] In addition, each of the function units in each embodiment of the present application can be integrated in one processing module, or each unit can be physically present separately, or two or more units can be integrated in one module. The integrated module can be realized in the form of hardware, or in the form of a software function module. When the integrated module is realized in the form of a software function module and sold or used as an independent product, it can also be stored in a computer readable storage medium.

[0107] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0108] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0109] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for pre-control of safe and stable operation mode of power grid, characterized in that, The method comprises the following steps: establishing simulation models of a plurality of operation modes according to preset operation data; determining all risks in each operation mode according to the simulation model of the operation mode; simulating the pre-control of the safe and stable operation mode of the power grid, and obtaining simulation pre-control results that meet the stability criterion; the stability criterion is a condition for the post-fault AC / DC system to be restored to stability after pre-control; determining the corresponding pre-control parameters according to the simulation pre-control results for each operation mode; wherein the simulation pre-control of the safe and stable operation mode of the power grid comprises: in the case of DC outage, simulating the fault corresponding to each risk; in the case of resuming DC operation, simulating the fault corresponding to each risk; wherein in the case of DC outage, simulating the fault corresponding to each risk comprises: in the case of DC outage, simulating the fault corresponding to risk i; by gradually reducing the amount of load connected to the AC / DC receiving end until the system can be restored to stability after the fault corresponding to risk i occurs, record the load amount Pi at this time; wherein in the case of resuming DC operation, simulating the fault corresponding to each risk comprises: in the case of load amount Pi, resume DC operation; by gradually reducing the DC power until the system can be restored to stability after the fault corresponding to risk i occurs, record the DC power Pdci at this time.

2. The method of claim 1, wherein, The preset operation data is annual typical operation mode data; The operation mode includes: dry large mode, dry small mode, wet large mode, and wet small mode; The simulation model includes each operation mode and its corresponding all related line maintenance mode and main transformer maintenance mode.

3. The method of claim 1, wherein, The determination of all risks in the operation mode comprises: scanning the risks of the heavy load area connected to the AC / DC receiving end under the given load and DC power of the operation mode; numbering the risks under each operation mode respectively.

4. The method of claim 1, wherein, The risk includes at least one of the following: N-1 fault, N-2 fault, N-1 fault under maintenance mode, and N-2 fault under maintenance mode.

5. The method of claim 1, wherein, The stability criterion includes at least one of the following: line or main transformer overload, power angle instability, system steady-state voltage instability, system steady-state frequency instability, system transient voltage instability, DC not blocked, and DC commutation failure number not greater than a preset threshold.

6. The method of claim 1, wherein, The determination of the corresponding pre-control parameters according to the simulation pre-control results comprises: the final load amount Pload of the mode pre-control is determined as: Pload=min(P1, P2 … Pi); the final DC power Pdc of the mode pre-control is determined as: Pdc=min(Pdc1, Pdc2 … Pdci).

7. A pre-control device for safe and stable operation mode of power grid, characterized in that, The method comprises the following steps: a model establishing module for establishing simulation models of a plurality of operation modes according to preset operation data; a risk determining module for determining all risks in each operation mode according to the simulation model of the operation mode; The simulation pre-control module is configured to simulate power grid safety and stability operation mode pre-control for all scanned risks to obtain simulation pre-control results meeting stability criteria; the stability criteria are conditions for pre-control results to meet a condition that an AC / DC system can be restored to stability after a fault; The parameter determination module is configured to determine pre-control parameters corresponding to each set of operation modes according to the simulation pre-control results; The simulation pre-control module is configured to perform simulation tests on faults corresponding to each risk in a DC outage condition and perform simulation tests on faults corresponding to each risk in a DC recovery condition; The simulation pre-control module is further configured to perform a simulation test on a fault corresponding to the risk i in the DC outage condition; gradually reduce the amount of load connected to the AC / DC receiving end until the system can be restored to stability after the fault corresponding to the risk i occurs, and record the load amount Pi at this time; In the case of the load amount Pi, the DC is recovered; gradually reduce the DC power until the system can be restored to stability after the fault corresponding to the risk i occurs, and record the DC power Pdci at this time.

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