A power grid safety control strategy optimization method containing a large-scale variable current power supply

Abstract

The application discloses a power grid safety control strategy optimization method containing a large-scale variable current power supply, which comprises the following steps: obtaining power grid parameters when the power grid oscillates or the variable current power supply is cut off; calculating the damping contribution, electrical distance and current flow ratio angle of a generator according to the power grid parameters; performing positive direction and dimensionless processing on the damping contribution, electrical distance and current flow ratio angle to obtain the dimensionless damping contribution, electrical distance and current flow ratio angle; calculating the cut-off priority of the generator according to the dimensionless damping contribution, electrical distance and current flow ratio angle; and selecting and processing the generator cut-off sequence in the power grid according to the cut-off priority. The application can obtain more accurate and reliable generator cut-off priority, meet the actual situation and demand of the power grid, give the best generator cut-off strategy and improve the safety control performance of the power grid.

Description

Technical Field

[0001] The present invention relates to a method for optimizing a power grid security control strategy containing a large-scale current-converting power supply, and belongs to the technical field of power grid security control. Background Art

[0002] During the safe operation of interconnected power grids, the disconnection of some transmission lines can trigger low-frequency oscillations within the interconnected grid. This necessitates the urgent reduction of the output power of the sending-end generators to suppress grid oscillations. The effectiveness of control varies among different generators, and selecting the most effective generator disconnection strategy is the primary basis for developing a safe and stable control strategy for the grid. Due to the random nature of wind and photovoltaic power generation and their current low penetration rates, once a transmission line is disconnected, the grid prioritizes disconnecting all renewable energy sources before removing the generators.

[0003] When developing grid security and stability control strategies, traditional generator shedding schemes typically prioritize power plants and then perform generator shedding operations based on this priority. Considering the damping capacity of the generator control system and the electrical distance between its connection point and the receiving network as two important factors in determining stability, the damping contribution and the phase angle difference of the node voltage are typically used. These two parameters are quantified and weighted to determine the generator shedding priority.

[0004] However, with the widespread use of renewable energy and its increasing penetration, renewable energy is contributing increasingly to power generation output, presenting new opportunities and challenges for the security and stability of interconnected power grids. Traditional power generation solutions for low-frequency oscillations in power systems may face new challenges or require improvements. Currently, numerous scientific and technical publications have examined the physical mechanisms and control strategies for suppressing grid power oscillations using photovoltaic (converter-type) power supplies. These studies demonstrate that the presence of renewable energy generation equipment in the grid should be considered when selecting the optimal power generation solution for developing grid security and stability control strategies.

[0005] As the penetration rate of renewable energy continues to increase, when the power grid fluctuates and large-scale variable-current power sources are removed, the generators connected to the variable-current power sources through the bus will be significantly affected by the sudden drop in current. Traditional generator disconnection solutions do not consider the impact of variable-current power source removal on generators, and their disconnection priority is no longer suitable for the ever-evolving power grid system. The power grid system needs to consider new, more comprehensive and more accurate power grid security and control strategies and methods. Summary of the Invention

[0006] In response to the problem that traditional generator cutting schemes do not consider the impact of the removal of variable-current power supplies on generators, the present invention proposes an optimization method for power grid security and control strategies containing large-scale variable-current power supplies. The generator side current is corrected according to the correlation between the variable-current power supply and the generator, and a new current ratio angle index is introduced. The generator cutting priority is calculated based on the damping contribution, electrical distance and current ratio angle, providing a safer and more reliable generator cutting strategy.

[0007] In order to solve the above technical problems, the present invention adopts the following technical means:

[0008] The present invention proposes a method for optimizing a power grid security control strategy containing a large-scale variable current power supply, comprising the following steps:

[0009] When the power grid oscillates and the inverter power supply is cut off, the power grid parameters are obtained;

[0010] Calculate the generator's damping contribution, electrical distance, and current ratio angle based on grid parameters;

[0011] Performing normalization and per-unit processing on the damping contribution, electrical distance and current ratio angle to obtain the per-unit damping contribution, electrical distance and current ratio angle;

[0012] The generator removal priority is calculated based on the normalized damping contribution, electrical distance and current ratio angle weighting;

[0013] The generators in the power grid are selected and cut off in order according to the cutting priority.

[0014] Furthermore, the grid parameters include the current of the variable power supply input to the grid, the current on the generator side, the voltage phase angle between the generator and the receiving grid, the generator power angle, and the generator rotor speed.

[0015] Furthermore, the damping contribution is calculated as:

[0016] According to the preset sampling interval, the Q group [△T e , △δ, △ω], where △T e represents the change in the electromagnetic torque of the generator, △δ represents the change in the generator power angle relative to the steady-state operating point, △ω represents the change in the generator rotor speed relative to the steady-state operating point, and Q is an integer;

[0017] Using the least squares matrix to process the Q group [ΔT e , △δ, Δω], and the damping torque coefficient D is obtained e , the expression of the least squares matrix B is as follows:

[0018]

[0019] wherein, △δ q represents the generator power angle change amount collected at the qth sampling time, △ω q represents the generator rotor speed change amount collected at the qth sampling time, △T eq represents the generator electromagnetic torque change amount collected at the qth sampling time, q = 1, 2, …, Q;

[0020] According to the damping torque coefficient D e The damping contribution of the generator in the sampling period is calculated, and the calculation formula is as follows:

[0021]

[0022] wherein, S d represents the damping contribution of the generator, and [t1, t2] represents the sampling period.

[0023] Further, the calculation method of the electrical distance is:

[0024] According to the voltage phase angle of the generator access node and the voltage phase angle of the receiving end power grid, the electrical distance of the generator is calculated, and the calculation formula is as follows:

[0025] D i = θ i - θ ref (3)

[0026] wherein, D i represents the electrical distance of the i th generator in the regional power grid, θ i represents the voltage steady-state angle of the i th generator access node, θ ref represents the voltage steady-state angle of the receiving end reference generator access node, i = 1, 2, …, m, and m is the number of generators in the regional power grid.

[0027] Further, the calculation method of the current ratio angle is:

[0028] According to the grid parameters, the correlation degree matrix of the converter type power supply and the generator is obtained, and the expression of the correlation degree matrix R is as follows:

[0029]

[0030] wherein, △θ ji represents the voltage angle between the injection bus of the j th converter type power supply and the injection bus of the i th generator, i = 1, 2, …, m, m is the number of generators in the regional power grid, j = 1, 2, …, n, and n is the number of converter type power supplies in the regional power grid;

[0031] According to the correlation degree matrix, the current value of the generator affected after the converter type power supply is removed is calculated, and the calculation formula is as follows:

[0032]

[0033] Among them, ΔI a It represents the current impact matrix of all generators in the regional power grid after the conversion power source is removed, ΔI ai Indicates the current impact value of the i-th generator after the conversion power supply is removed, ΔI dj Indicates the current value when the jth variable current power supply is cut off;

[0034] The current ratio angle of the generator is calculated based on the current value affected by the generator and the electrical distance of the generator. The calculation formula is as follows:

[0035]

[0036] Among them, Δβ i Denotes the current ratio angle of the i-th generator in the regional power grid, D i represents the electrical distance of the i-th generator, I ai represents the current on the i-th generator side.

[0037] Furthermore, the method to obtain the normalized damping contribution, electrical distance and current ratio angle is:

[0038] The maximum damping contribution Max(S) is obtained from the damping contribution, electrical distance and current ratio angle of all generators. d ), maximum electrical distance Max(D) and maximum current ratio angle Max(Δβ);

[0039] According to [Max(S d ),Max(D),Max(Δβ)] are used to normalize the damping contribution, electrical distance and current ratio angle of each generator:

[0040]

[0041] Among them, S' di Denotes the positive value of the damping contribution of the i-th generator in the regional power grid, D' i represents the positive value of the electrical distance of the i-th generator, Δβ' i The current of the i-th generator is the positive value of the angle, S di represents the damping contribution of the i-th generator, D i represents the electrical distance of the i-th generator, Δβ i represents the current ratio angle of the i-th generator, i = 1, 2, …, m, where m is the number of generators in the regional power grid;

[0042] According to the normalized value, the normalized damping contribution, electrical distance and current ratio angle are obtained:

[0043]

[0044] Among them, S” di Denotes the damping contribution of the ith generator after normalization, D” i represents the electrical distance of the ith generator after normalization, Δβ” i It represents the normalized current ratio angle of the i-th generator.

[0045] Furthermore, the calculation formula of the generator removal priority is as follows:

[0046] PRI i =a·S” di +(1-a)·(b·D” i +(1-b)·△β” i ) (9)

[0047] Among them, PRI i represents the removal priority of the i-th generator, a is the index weight of the damping contribution index, and b is the subdivision index weight of the relative electrical distance of the current ratio angle.

[0048] Furthermore, a generator removal priority of 0 indicates that the generator cannot be removed; a lower generator removal priority value indicates a higher priority for removal of the generator.

[0049] The following advantages can be obtained by adopting the above technical means:

[0050] The present invention proposes a method for optimizing the safety and control strategy of a power grid containing large-scale variable-current power supplies. Considering that the removal of a large number of variable-current power supplies will inevitably affect the current, power angle, etc. of the generator, the present invention introduces a new current ratio angle index based on the existing technology. The generator cutting priority is calculated by damping contribution, electrical distance, and current ratio angle. The resulting generator cutting priority is more comprehensive and the numerical value is more accurate and reliable, meeting the actual situation and needs of the power grid. It can provide the best generator cutting strategy and improve the safety and control performance of the power grid. The method of the present invention also determines the correlation between the variable-current power supply and each power plant based on the topological position of the variable-current power supply in the power grid structure, and then calculates the current value affected by the generator after the variable-current power supply is removed. Finally, an accurate current ratio angle index is calculated to ensure the accuracy of the power grid safety and control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the system for injecting variable current power into the power grid;

[0052] Figure 2Schematic diagram of voltage vectors on the generator, converter type power supply and receiving grid side;

[0053] Figure 3 The present invention is a flowchart of the steps of a method for optimizing a power grid security control strategy containing a large-scale variable current power supply. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings:

[0055] Systems where variable current power is injected into the grid, such as Figure 1 As shown in the figure, considering that the power oscillation under electromechanical time and the photovoltaic inverter dynamic process under electromagnetic time are in different time scales and the gap is large, the variable current power supply is represented by an active current source. Figure 1 In, X, X l are the equivalent reactances of the synchronous generator side and the receiving grid side, respectively, and k is X and X l The coefficient between a , I b Represent the current sources on the generator side and the grid side, I d It represents the active current injected by the variable current power supply into the grid. E, V, and U are the synchronous machine electromotive force, grid point voltage, and grid-side electromotive force, respectively. δ and β are the corresponding phase angles of E and U, respectively.

[0056] exist Figure 1 Based on this, the voltage vector diagram of the equivalent system is made, as shown in the following example: Figure 2 As shown, it is assumed that E and U are equal and constant.

[0057] when Figure 1 When the system is operating normally, the variable current power supply suppresses power oscillation by injecting or absorbing active power into the grid. The electromagnetic power P output by the synchronous generator e It can be expressed as:

[0058]

[0059] The active power absorbed by the grid is:

[0060] P ∞ =VUsinβ / (kX) (11)

[0061] According to the principle of conservation of system active power, we can get:

[0062]

[0063] Simplifying formula (12) we can get:

[0064]

[0065] According to Kirchhoff's current law:

[0066]

[0067] Formula (14) can be rewritten as:

[0068] kEcosδ-kV=V-Ucosβ (15)

[0069] kEsinδ+kXI d =Usinβ (16)

[0070] Combining formulas (15) and (16), we can obtain:

[0071] [V(1+k)-kEcosδ] 2 +(kEsinδ+kXI d ) 2 =U 2 (17)

[0072] Linearizing formula (17) yields:

[0073]

[0074] Where ΔV represents the change in the grid voltage when the output current value of the variable power supply changes, δ0 is the system rated phase angle, Δδ represents the change in the phase angle of E when the output current value of the variable power supply changes, I d0 is the rated output current of the variable current power supply, ΔI d It indicates the change in the output current value of the variable current power supply, and V0 is the initial value of the rated voltage of the network point.

[0075] According to the above calculations and Figure 1 From the physical meaning of the above, it can be seen that when the active current I injected by the variable current power supply into the grid d Or when the power angle δ of the synchronous generator changes, the voltage V at the point where the variable current power source is connected to the grid will also change. Therefore, formula (18) can be changed to:

[0076]

[0077] Substituting formula (19) into the linearized formula (10) yields the change in electromagnetic power output by the synchronous generator:

[0078] ΔP e =K g Δδ-K f ΔI d (20)

[0079] Among them: K g K is the coefficient of the system's ability to achieve self-stabilization,f It is the coefficient of the variable current power supply's ability to control the system's dynamic characteristics. The subscript "0" represents the variable steady-state operating point value.

[0080]

[0081]

[0082] The above content analyzes the role of variable current power supply in grid security and stability. Conversely, when part of the transmission line of the grid is disconnected and the output power of the sending-end generator set needs to be urgently reduced to suppress oscillation, the variable current power supply is cut off first, then ΔI d =-I d , it can be seen from formula (20) that the removal of the variable current power supply will inevitably have an impact on the power angle and electromagnetic output power of the generator.

[0083] The present invention fully considers the impact of variable current power supply on generators and proposes a method for optimizing the security control strategy of power grids containing large-scale variable current power supply. Figure 3 As shown, the specific steps include:

[0084] Step A: When the power grid experiences oscillation and the inverter power source is removed, grid parameters are obtained. Grid parameters include, but are not limited to, the current input from the inverter power source to the grid, the current on the generator side, the voltage phase angle between the generator and the receiving grid, the generator power angle, and the generator rotor speed. These grid parameters can be obtained directly or indirectly through the system.

[0085] Step B: Calculate the damping contribution, electrical distance and current ratio angle of the generator according to the grid parameters.

[0086] Step B01: Analysis and calculation of the damping contribution of the generator:

[0087] The damping state of a generator during low-frequency oscillation is related to the network structure and parameters, operating conditions, and generator control system parameters. After a grid disturbance, the generator's PSS (power system stability), excitation winding, damping winding, and mechanical system can all provide a certain amount of positive damping. However, the excitation system and speed regulator may, under certain circumstances, exhibit negative damping, weakening the overall system damping and thus causing relative oscillations in the interconnected system.

[0088] During steady-state operation, the mechanical torque or power is equal to the generator's electromagnetic torque or output electromagnetic power. During electromechanical transients, the mechanical torque or power varies under the control of the speed regulator, and the electromagnetic power also varies with time. Mechanical power is determined by the prime mover and its speed regulation system, which influences rotor motion by varying the mechanical torque. During low-frequency oscillations in an interconnected system, the generator's rotor frequency fluctuates symmetrically around approximately 50 Hz, with minimal speed deviations. Long-term high or low frequency fluctuations are avoided, and the inertia of the speed regulator slows down the response of the mechanical power. Therefore, during these low-frequency oscillations, the mechanical power varies minimally, and the damping torque exerted on the rotor by the mechanical torque is negligible.

[0089] (1) Collect Q groups [△T e , △δ, △ω], where △T e represents the change in the electromagnetic torque of the generator, △δ represents the change in the generator power angle relative to the steady-state operating point, △ω represents the change in the generator rotor speed relative to the steady-state operating point, and Q is an integer.

[0090] Since [△T e , Δδ, Δω] are all changes relative to the steady-state operating point, so the present invention also needs to determine the steady-state operating point corresponding to each sampling moment. After a large disturbance occurs in the system, each generator will oscillate from the original steady-state operating point to the new steady-state operating point, so ΔT at different times is calculated. e , Δδ and Δω should use different steady-state values; collect the peak and valley values ​​of the electrical quantity in each oscillation cycle, use the cubic spline difference function to fit the upper and lower envelopes of the oscillation curve, and use the median of the two envelopes at the same moment as the steady-state operating point at that moment.

[0091] (2) Using the least squares matrix to process the Q group [ΔT e , Δδ, Δω], and the damping torque coefficient D is obtained e .

[0092] The generator excitation system affects the rotor motion by changing the electromagnetic torque. When Δω is small, the change in electromagnetic torque ΔT e can be decomposed into two components: synchronous torque and damping torque, namely:

[0093] ΔT e =K e Δδ+D e Δω (23)

[0094] Among them, K e is the electromagnetic synchronous torque coefficient, D e is the electromagnetic damping torque coefficient.

[0095] The expression of the least squares matrix B is as follows:

[0096]

[0097] in, △δ q Indicates the change in generator power angle collected at the qth sampling moment, △ω q Indicates the change in generator rotor speed collected at the qth sampling moment, △T eq It represents the change of the electromagnetic torque of the generator collected at the qth sampling moment, q = 1, 2, …, Q.

[0098] The decoupling of the damping torque and the synchronizing torque can be achieved through formula (24).

[0099] (3) According to the damping torque coefficient D e Calculate the damping contribution of the generator during the sampling period.

[0100] The synchronous torque mainly affects the oscillation frequency, while the damping torque is directly related to the development trend of the oscillation. e When D > 0, a positive damping torque component with the same phase as the speed change Δω is generated in the electromagnetic torque, which helps to suppress low-frequency oscillation. e When <0, the excitation system damping is negative. e It reflects the comprehensive damping of the excitation winding, excitation system and PSS. Since the damping effect of the speed regulator is ignored, D e The phase relationship between Δω and Δω reflects the overall damping properties of the unit control system.

[0101] The synchronous torque component in formula (23) has nothing to do with the low-frequency oscillation. The synchronous torque and damping torque are decoupled and the VT e The effect of the damping torque is cumulatively calculated. Therefore, the quantitative expression of the generator damping contribution from time t1 to time t2 is defined as:

[0102]

[0103] Among them, S d represents the damping contribution of the generator, and [t1, t2] represents the sampling period.

[0104] Step B02: After the inverter power source is removed, the power angle and electromagnetic output power of the thermal generator are affected. The electrical distance of the generator is calculated based on the voltage phase angle of the node where the generator is connected and the voltage phase angle of the receiving grid. The calculation formula is as follows:

[0105] D i =θ i -θ ref (26)

[0106] Among them, D i represents the electrical distance of the i-th generator in the regional power grid, θ i represents the voltage steady-state angle of the node connected to the i-th generator, θ ref represents the voltage steady-state angle of the receiving-end reference generator access node, i = 1, 2, …, m, where m is the number of generators in the regional power grid.

[0107] A longer electrical distance means that the difference between the voltage phase angle of the access node and the voltage phase angle of the receiving grid is larger.

[0108] Step B03: Analysis and calculation of the generator's current ratio angle:

[0109] (1) Photovoltaic power generation, a type of variable current power source, is a distributed power source. After the generated current is collected, it is boosted by a low-voltage box transformer and sent to the medium- and low-voltage grid busbars. Thermal power generators, on the other hand, boost the voltage by transformers and send it to the high-voltage grid busbars. Due to the interconnectedness of the grid, the current sent by the variable current power source will have a certain impact on each thermal generator in the regional network. The impact of the variable current power source on the current sent by each thermal generator needs to be determined by the degree of correlation between the variable current power source and each thermal generator.

[0110] The correlation between the variable-current generators and each power plant is determined based on their topological position in the power grid. Since the voltage angle gradually decreases along the direction of active power transmission, this correlation can be calculated by the voltage angle between the busbar injected by the variable-current generator and the busbar injected by the thermal generator. For n variable-current generators in a regional power grid, the correlation R between them and m thermal generators in the regional power grid is an n*m matrix, expressed as follows:

[0111]

[0112] Among them, △θ ji It represents the voltage angle between the injection bus of the j-th variable-current generator and the injection bus of the i-th generator, also known as the phase angle difference between the bus where the j-th variable-current generator is located and the bus where the i-th thermal generator is located, j = 1, 2, …, n.

[0113] (2) According to the correlation matrix, the current of each generator after the conversion power supply is cut off can be calculated. Figure 1 The affected current value is calculated as follows:

[0114]

[0115] Among them, ΔI a It represents the current impact matrix of all generators in the regional power grid after the conversion power source is removed, ΔI aiIndicates the current impact value of the i-th generator after the conversion power supply is removed, ΔI dj Indicates the current value when the j-th variable current power supply is cut off.

[0116] (3) After the variable current power supply is cut off, the influence of the disappearance of its injection current on the damping contribution of the generator is ignored, that is, sinδ in formula (13) is divided by zero, then ΔI d =-I d , and from formula (13) we can see the impact on the corresponding phase angle β is as follows:

[0117]

[0118]

[0119] Electrical distance indicator D i The current ratio angle Δβ is equal to the phase angle β in the steady state. The current ratio angle Δβ is the difference between the electrical distance D and the current ratio D after the power supply is cut off. i From another perspective, the current ratio angle Δβ is also caused by the change in current before and after the inverter power supply is cut off. Therefore, the current ratio angle of the generator is calculated based on the current value affected by the generator and the electrical distance of the generator. The calculation formula is as follows:

[0120]

[0121] Among them, Δβ i represents the current ratio angle of the i-th generator in the regional power grid, I ai represents the current on the i-th generator side.

[0122] Step C: Perform normalization and per-unit processing on the damping contribution, electrical distance, and current ratio angle to obtain the per-unit damping contribution, electrical distance, and current ratio angle. The specific operations are as follows:

[0123] Step C01: Obtain the maximum damping contribution Max(S) from the damping contribution, electrical distance and current ratio angle of all generators. d ), maximum electrical distance Max (D) and maximum current ratio angle Max (Δβ).

[0124] Step C02: According to [Max(S d ),Max(D),Max(Δβ)] perform forward processing on the damping contribution, electrical distance and current ratio angle of each generator (subtract the specific value of each object from the maximum value):

[0125]

[0126] Among them, S' diDenotes the positive value of the damping contribution of the i-th generator in the regional power grid, D' i represents the positive value of the electrical distance of the i-th generator, Δβ' i It represents the positive value of the current ratio angle of the i-th generator.

[0127] Step C03: Perform per-unit normalization processing based on the normalized value (dividing the normalized value by the maximum value) to obtain the normalized damping contribution, electrical distance, and current ratio angle:

[0128]

[0129] Among them, S” di Denotes the damping contribution of the ith generator after normalization, D” i represents the electrical distance of the ith generator after normalization, Δβ” i It represents the normalized current ratio angle of the i-th generator.

[0130] Step D: Calculate the generator removal priority based on the normalized damping contribution, electrical distance, and current ratio angle weighted. The calculation formula for the generator removal priority is as follows:

[0131] PRI i =a·S” di +(1-a)·(b·D” i +(1-b)·Δβ” i ) (34)

[0132] Among them, PRI i It represents the removal priority of the i-th generator, a is the index weight of the damping contribution index, and b is the subdivision index weight of the relative electrical distance of the current ratio angle. The values ​​of a and b can be set according to the working conditions.

[0133] Step E: Select and process the generators in the power grid for disconnection in order based on their disconnection priorities. A generator disconnection priority of 0 indicates that the generator cannot be disconnected; the lower the generator disconnection priority, the higher the priority for disconnection.

[0134] Compared to existing technologies, the method of the present invention fully considers the impact of removing a large number of variable-flow power supplies on the generator's current, power angle, and other factors. It introduces a new current ratio angle index based on existing technologies, calculating the generator cutting priority by taking into account damping contribution, electrical distance, and current ratio angle. The resulting generator cutting priority is more comprehensive, with more accurate and reliable values, meeting the actual conditions and needs of the power grid, and can provide an optimal generator cutting strategy, improving the power grid's safety and control performance. Furthermore, to more accurately calculate the current ratio angle index, the method of the present invention also determines the correlation between the variable-flow power supplies and each power plant based on their topological position in the power grid structure, and then calculates the current value affected by the generator after the variable-flow power supplies are removed. Ultimately, an accurate current ratio angle index is calculated, ensuring the accuracy of the power grid's safety and control strategy.

[0135] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for optimizing security control strategies for a power grid containing large-scale variable current power supplies, characterized in that: The steps include: When the power grid oscillates and the inverter power supply is cut off, the power grid parameters are obtained; Calculate the generator's damping contribution, electrical distance, and current ratio angle based on grid parameters; Performing normalization and per-unit processing on the damping contribution, electrical distance and current ratio angle to obtain the per-unit damping contribution, electrical distance and current ratio angle; The generator removal priority is calculated based on the normalized damping contribution, electrical distance and current ratio angle weighting; The generators in the power grid are selected and cut off in order according to the cutting priority.

2. The method for optimizing security control strategies for a power grid containing large-scale variable current power sources according to claim 1, characterized in that: The grid parameters include the current of the variable power supply input to the grid, the current on the generator side, the voltage phase angle between the generator and the receiving grid, the generator power angle, and the generator rotor speed.

3. The method for optimizing security control strategy of a power grid containing a large-scale variable current power supply according to claim 1, characterized in that: The damping contribution is calculated as: Collect Q group from historical power grid data according to the preset sampling interval ,in represents the change in the electromagnetic torque of the generator, Indicates the change in the generator power angle relative to the steady-state operating point, It represents the change of the generator rotor speed relative to the steady-state operating point, Q is an integer; Using the least squares matrix to process the Q group , and the damping torque coefficient is obtained , the expression of the least squares matrix B is as follows: ； in, is the electromagnetic synchronous torque coefficient, , , It represents the change of the generator power angle collected at the qth sampling moment, It represents the speed change of the generator rotor collected at the qth sampling moment, represents the change in the generator electromagnetic torque collected at the qth sampling moment, ; According to the damping torque coefficient Calculate the damping contribution of the generator during the sampling period. The calculation formula is as follows: ； in, represents the damping contribution of the generator, Indicates the sampling period.

4. The method for optimizing security control strategies for a power grid containing large-scale variable current power supplies according to claim 1, characterized in that: The calculation method of electrical distance is: The electrical distance of the generator is calculated based on the voltage phase angle of the generator access node and the voltage phase angle of the receiving grid. The calculation formula is as follows: ； in, represents the electrical distance of the ith generator in the regional grid, represents the voltage steady-state angle of the node connected to the i-th generator, It represents the voltage steady-state angle of the receiving end reference generator access node, , m is the number of generators in the regional power grid.

5. The method for optimizing security control strategy of a power grid containing a large-scale variable current power supply according to claim 1, characterized in that: The calculation method of the current ratio angle is: According to the grid parameters, the correlation matrix between the variable current power supply and the generator is obtained. The correlation matrix The expression is as follows: ； in, represents the voltage angle between the injection bus of the j-th variable current generator and the injection bus of the i-th generator, , m is the number of generators in the regional power grid, , n is the number of variable current power sources in the regional power grid; The current value of the generator affected by the removal of the variable current power supply is calculated based on the correlation matrix. The calculation formula is as follows: ； in, represents the current impact matrix of all generators in the regional power grid after the conversion power source is removed, It represents the current impact value of the i-th generator after the conversion power supply is removed. Indicates the current value when the jth variable current power supply is cut off; The current ratio angle of the generator is calculated based on the current value affected by the generator and the electrical distance of the generator. The calculation formula is as follows: ； in, represents the current ratio angle of the i-th generator in the regional power grid, represents the electrical distance of the ith generator, represents the current on the i-th generator side.

6. The method for optimizing security control strategy of a power grid containing a large-scale variable current power supply according to claim 1, characterized in that: The method to obtain the normalized damping contribution, electrical distance and current ratio angle is: Get the maximum damping contribution from the damping contribution, electrical distance and current ratio angle of all generators respectively , Maximum electrical distance and the maximum current ratio angle ; according to Forward the damping contribution, electrical distance, and current magnitude angle of each generator: ； in, represents the positive value of the damping contribution of the i-th generator in the regional power grid, represents the positive value of the electrical distance of the i-th generator, represents the positive value of the current ratio angle of the i-th generator, represents the damping contribution of the i-th generator, represents the electrical distance of the ith generator, represents the current ratio angle of the i-th generator, , m is the number of generators in the regional power grid; According to the normalized value, the normalized damping contribution, electrical distance and current ratio angle are obtained: ； in, represents the damping contribution of the ith generator after per-unit normalization, represents the electrical distance of the ith generator after normalization, It represents the normalized current ratio angle of the i-th generator.

7. The method for optimizing security control strategy of a power grid containing large-scale variable current power supply according to claim 6, characterized in that: The calculation formula of the generator removal priority is as follows: ； in, represents the removal priority of the i-th generator, a is the index weight of the damping contribution index, and b is the subdivision index weight of the relative electrical distance of the current ratio angle.

8. The method for optimizing security control strategy of a power grid containing large-scale variable current power sources according to claim 1, characterized in that: A generator removal priority of 0 indicates that the generator cannot be removed; a lower generator removal priority value indicates a higher priority for removal of the generator.

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