Construction method and device of injection current feasible region considering whole fault process, terminal equipment and storage medium

Abstract

The invention discloses an injection current feasible region construction method and device considering the whole fault process, terminal equipment and a storage medium, and belongs to the technical field of current feasible region construction, and the method comprises the steps: obtaining electric power data of an electric power system and an initial electric power system operation state quantity, and constructing a nonlinear mathematical model before a fault, solving to obtain a first power system operation state quantity; then constructing a nonlinear mathematical model in the fault corresponding to each injection current, and solving to obtain a second power system operation state quantity corresponding to each injection current; then constructing a post-fault nonlinear mathematical model, and solving to obtain a third power system operation state quantity; and finally, determining the feasible region of the injection current according to the third power system operation state quantity. By implementing the method, the problem that the application value of the feasible region in the aspect of guaranteeing the stable operation of a power system is limited because the constructed feasible region cannot provide effective guidance for the whole fault process in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of current feasible domain construction, and in particular to a method, device, terminal equipment and storage medium for constructing an injection current feasible domain considering the entire fault process. Background Art

[0002] As the global energy crisis intensifies, power grids are trending toward a "dual high" trend: a high proportion of renewable energy and a high proportion of power electronics. This trend is emphasizing the application of both renewable energy and power electronics. However, VSC systems are susceptible to transient synchronization and stability issues after experiencing major disturbances, such as power system failures. If the injected current exceeds a certain range, it can cause system voltage fluctuations, frequency deviations, and even system oscillations and failures, threatening the safe and reliable operation of the power system.

[0003] Existing technologies often focus on analyzing stability during a fault when determining the feasible domain for injected current, but ignore the recovery of the power system's transient stability after the fault is cleared. However, in reality, even after a system loses transient stability during a fault, it is still possible to recover. Examining only stability during the fault period results in the construction of the feasible domain for injected current failing to consider the entire system's operation. Consequently, the constructed feasible domain fails to provide effective guidance for the entire fault process, limiting its application value in ensuring stable power system operation. Summary of the Invention

[0004] The present invention provides a method, apparatus, terminal device and storage medium for constructing an injection current feasible domain that takes into account the entire fault process. The method can solve the problem in the prior art that the complete operation process of the power system is not taken into account when constructing the injection current feasible domain, resulting in the constructed injection current feasible domain being unable to provide effective guidance for the entire fault process, thereby limiting its application value in ensuring the stable operation of the power system.

[0005] An embodiment of the present invention provides a method for constructing a feasible region of injected current considering the entire fault process, including:

[0006] Acquire power data of the power system and initial power system operating state quantities when there is no fault; wherein the power data includes: phase-locked loop proportional coefficient, equivalent resistance, equivalent reactance, equivalent fault network voltage, and phase-locked loop integral coefficient;

[0007] Based on the power data and the initial power system operating state quantity, a pre-fault nonlinear mathematical model of the power system is constructed, and the pre-fault nonlinear mathematical model is solved to obtain a first power system operating state quantity of the power system at the beginning of the fault;

[0008] Constructing a nonlinear mathematical model of the fault corresponding to each injected current based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, and solving the nonlinear mathematical model of the fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0009] constructing a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solving the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current;

[0010] According to the third power system operating state quantity, an operating trajectory of the power system after the fault corresponding to each injected current is drawn, and a feasible region of the injected current is determined according to the operating trajectory.

[0011] Furthermore, the above nonlinear mathematical model before the fault is:

[0012]

[0013] Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, V tq represents the q-axis component of the AC voltage at the grid connection point, x p It represents the integral of the difference between the active power tracking reference value and the active power before the fault, P ref Indicates the tracking reference value of active power, P represents active power, x V It represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, k i1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

[0014] Furthermore, based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, a nonlinear mathematical model corresponding to each injected current is constructed, and the nonlinear mathematical model is solved to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated, including:

[0015] Get the preset maximum output current;

[0016] Calculate the minimum injection current based on the preset maximum output current and the equivalent resistance;

[0017] Calculate the maximum injection current based on the preset maximum output current and the equivalent reactance;

[0018] Determining a current value range of the injection current according to the minimum injection current and the maximum injection current;

[0019] Acquire a plurality of injection currents from the current value range according to a preset step size, and for each injection current, construct a nonlinear mathematical model of the fault corresponding to each injection current based on the injection current, a phase-locked loop proportional coefficient, an equivalent fault network voltage, a phase-locked loop integral coefficient, and the first power system operating state quantity;

[0020] Solving the nonlinear mathematical model of the above fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0021] Among them, the nonlinear mathematical model of the above fault is:

[0022]

[0023] Where c represents the linear function expression of the above injection current, θ′ pll The phase angle of the phase-locked loop output when the fault starts, x′ pll It represents the integral of the q-axis component of the AC voltage at the beginning of the fault.

[0024] Furthermore, the above-mentioned nonlinear mathematical model after the fault is:

[0025]

[0026] Where, P in represents the input active power reference value after adjusting the power recovery rate, τ represents the active power recovery rate time constant, θ″ pll Indicates the phase angle of the phase-locked loop output when the fault is cleared, x″ pllrepresents the integral of the q-axis component of the AC voltage when the fault is cleared, x″ P Indicates the integral of the difference between the active power tracking reference value and the active power when the fault is cleared, x″ V It represents the integral of the difference between the tracking reference value of the AC voltage at the grid connection point and the amplitude of the AC voltage at the grid connection point when the fault is cleared.

[0027] Furthermore, determining the feasible region of the injected current according to the operating trajectory includes:

[0028] After obtaining each running trajectory, determine whether the running trajectory converges within a preset time period;

[0029] If converged, the injection current corresponding to the above operation trajectory is used as the target injection current; otherwise, the corresponding injection current is used as the non-target injection current;

[0030] According to all target injection currents, the injection current feasible region is generated.

[0031] Furthermore, after determining the feasible region of the injected current, the method further includes:

[0032] Obtaining a current injection current of the power system, and comparing the current injection current with the injection current feasible region;

[0033] When the current injected current is not within the feasible region of the injected current, it is determined that the current power system has not recovered stability, and an early warning is issued.

[0034] Based on the above method embodiment, the present invention provides a corresponding device embodiment;

[0035] The present invention provides a device for constructing a feasible region of injected current considering the entire fault process, comprising:

[0036] A data acquisition module, a first power system operation state quantity calculation module, a second power system operation state quantity calculation module, a third power system operation state quantity calculation module, and an injection current feasible region determination module;

[0037] The data acquisition module is used to acquire power data of the power system and the initial power system operating state quantity when there is no fault; wherein the power data includes: phase-locked loop proportional coefficient, equivalent resistance, equivalent reactance, equivalent fault network voltage and phase-locked loop integral coefficient;

[0038] The first power system operating state quantity calculation module is used to construct a pre-fault nonlinear mathematical model of the power system based on the power data and the initial power system operating state quantity, and solve the pre-fault nonlinear mathematical model to obtain the first power system operating state quantity of the power system at the beginning of the fault;

[0039] The second power system operating state quantity calculation module is used to construct a nonlinear mathematical model corresponding to each injected current in the fault based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, and solve the nonlinear mathematical model in the fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0040] The third power system operating state quantity calculation module is used to construct a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solve the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current;

[0041] The injection current feasible region determination module is used to draw the operation trajectory of the power system after the fault corresponding to each injection current according to the third power system operation state quantity, and determine the injection current feasible region according to the operation trajectory.

[0042] Furthermore, the above-mentioned pre-fault nonlinear mathematical model is constructed as follows:

[0043]

[0044] Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, V tq represents the q-axis component of the AC voltage at the grid connection point, x p It represents the integral of the difference between the active power tracking reference value and the active power before the fault, P ref Indicates the tracking reference value of active power, P represents active power, x V It represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, ki1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

[0045] Based on the above method embodiment, the present invention provides a corresponding terminal device embodiment;

[0046] The present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the method for constructing a feasible domain of injected current considering the entire fault process described in any embodiment of the present invention.

[0047] Based on the above method embodiment, the present invention provides a storage medium embodiment;

[0048] The present invention provides a storage medium comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the method for constructing a feasible domain of injected current considering the entire fault process described in any embodiment of the present invention is implemented.

[0049] The embodiments of the present invention have the following beneficial effects:

[0050] The present invention provides a method, device, terminal equipment and storage medium for constructing a feasible domain of injection current considering the entire fault process, the method comprising: first obtaining power data of the power system and the initial power system operating state quantity when there is no fault; wherein the power data comprises: a phase-locked loop proportional coefficient, an equivalent resistance, an equivalent reactance, an equivalent fault network voltage and a phase-locked loop integral coefficient; then, based on the power data and the initial power system operating state quantity, constructing a pre-fault nonlinear mathematical model of the power system, and solving the pre-fault nonlinear mathematical model to obtain the first power system operating state quantity of the power system at the beginning of the fault; then, based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, lock Phase loop integral coefficient and the above-mentioned first power system operating state quantity, construct a nonlinear mathematical model corresponding to each injected current during the fault, and solve the above-mentioned nonlinear mathematical model during the fault to obtain the second power system operating state quantity corresponding to each injected current when the fault is eliminated; then, based on the above-mentioned second power system operating state quantity and the above-mentioned power data, construct a nonlinear mathematical model corresponding to each injected current after the fault, and solve the above-mentioned nonlinear mathematical model after the fault to obtain the third power system operating state quantity corresponding to each injected current; finally, based on the above-mentioned third power system operating state quantity, draw the operating trajectory of the power system after the fault corresponding to each injected current, and determine the feasible domain of the injected current based on the above-mentioned operating trajectory. Therefore, the present invention sequentially constructs nonlinear mathematical models of the power system before, during and after the fault, and finally solves the operating trajectory after the fault corresponding to each injected current. Based on all the operating trajectories, the feasible domain of the injected current is finally obtained. Therefore, in the process of constructing the entire injection current feasible domain, the entire operating process of the power system is fully taken into account, so that the obtained feasible domain can provide an effective reference for the entire fault process, and ultimately provide a guarantee for the stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0052] Figure 1 It is a flowchart of a method for constructing a feasible region of injected current considering the entire fault process provided by one embodiment of the present invention.

[0053] Figure 2 FIG. 1 is a schematic diagram of the topology structure of a WG-VSG system provided in one embodiment of the present invention.

[0054] Figure 3 This is a simulation diagram of a calculation example provided by an embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram of the outer loop control strategy in different stages provided by an embodiment of the present invention.

[0056] Figure 5 It is a schematic diagram of the mechanism process of revealing the entire fault process by the equal area law provided by one embodiment of the present invention.

[0057] Figure 6 This is a diagram showing the construction result of the current feasible region in the case of Example 1 provided by one embodiment of the present invention.

[0058] Figure 7 4 is a diagram showing the construction results of the current feasible region in the cases of Examples 2 and 4 provided by one embodiment of the present invention.

[0059] Figure 8 4 is a diagram showing the construction results of the current feasible region in the cases of Examples 3 and 4 provided by one embodiment of the present invention.

[0060] Figure 9 Schematic diagram of the effect of the removal time on the feasible region of the injected current provided by an embodiment of the present invention.

[0061] Figure 10 1 is a schematic diagram of simulation results of point A and point B provided by an embodiment of the present invention.

[0062] Figure 11 It is a schematic diagram of simulation results when point C and point D are not cut off according to an embodiment of the present invention.

[0063] Figure 12 Schematic diagram of the effect of power recovery rate after power removal on the current feasible region provided by an embodiment of the present invention.

[0064] Figure 13 FIG. 4 is a schematic diagram of simulation results of point D provided by an embodiment of the present invention.

[0065] Figure 14 FIG. 1 is a schematic diagram of simulation results of point E provided by an embodiment of the present invention.

[0066] Figure 15 It is a structural diagram of a device for constructing a feasible region of injected current considering the entire fault process provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0067] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0068] See also Figure 1 To address the problem in the prior art that the entire operation process of the power system is not considered when constructing the injection current feasible region, resulting in the constructed injection current feasible region being unable to provide effective guidance for the entire fault process, thereby limiting its application value in ensuring the stable operation of the power system, an embodiment of the present invention provides a method for constructing the injection current feasible region that considers the entire fault process, including:

[0069] Step S101: acquiring power data of the power system and initial power system operating state quantities when there is no fault; wherein the power data includes: a phase-locked loop proportional coefficient, an equivalent resistance, an equivalent reactance, an equivalent fault network voltage, and a phase-locked loop integral coefficient;

[0070] Specifically, the above power data also includes: tracking reference value of active power, tracking reference value of grid connection point AC voltage, active outer loop proportional coefficient, active outer loop integral coefficient, reactive outer loop proportional coefficient and reactive outer loop integral coefficient.

[0071] Specifically, the above initial power system operating state quantities are: the phase-locked loop output phase angle θ before the fault pll , the integral of the q-axis component of the AC voltage before the fault x pll , before the fault, the integral of the difference between the active power tracking reference value and the active power x p , and the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault x V .

[0072] Schematically, the topology of the WG-VSG system is as follows Figure 2 As shown, C is the source side capacitance, U dc DC voltage, E is VSC output voltage, L f is the filter inductor, C f is the filter capacitor, θ t is the voltage phase angle at the grid connection point, Z g1 and Z g2 Both are equivalent grid-side impedance, Z g1 =R g1 +jX g1 , Z g2 =R g2 +jX g2 , R g1and R g2 Are equivalent grid side resistance, X g1 and X g2 All are equivalent grid-side reactance, V g is the equivalent grid-side voltage, Δω pll is the phase-locked loop angular frequency change, s is a complex variable, and "LVRT" stands for low voltage ride-through control. The VSC is connected to the grid through the LC filter, and the voltage at the AC side grid connection point (PCC) is V t <θ t , the grid voltage is V s <0°.

[0073] Indicatively, existing literature primarily focuses on transient stability analysis during faults, while ignoring the transient stability of the system after fault removal. However, whether the fault is removed, when the fault is removed, and how the current is injected during the fault will all affect the transient stability of the system. This is illustrated using the simulation example in Table 1. Specific system parameters are shown in Table 2:

[0074] Table 1 Example

[0075] Calculation example Voltage drop Injection current Is the fault cleared? Is it stable? Calculation example 1 1pu→0.095pu 0.5pu / 1pu no no Calculation example 2 1pu→0.095pu 0.8pu / 1pu Cut off at 0.3s yes Calculation example 3 1pu→0.095pu 0.5pu / 1pu Cut off at 0.5s yes Calculation example 4 1pu→0.095pu 0.8pu / 1pu Cut off at 0.5s no

[0076] Table 2 System parameters

[0077]

[0078]

[0079] Indicatively, the above examples are simulated, and the simulation diagram of the example is as follows Figure 3 As shown, by comparing Case 1 ("Case 1") and Case 2 ("Case 2"), it can be seen that when the system is disturbed by a three-phase symmetrical fault and the grid-side voltage drops to 0.095 pu, if the fault is not removed, the system cannot be stable; however, if the fault is removed at 0.3 s, the system will transition to a transient stable equilibrium state. Therefore, it is necessary to consider the entire fault process to facilitate the transient synchronous stability of the WG-VSC system. By comparing Case 2 and Case 4 ("Case 4"), it can be seen that when the grid-side voltage drops to 0.095 pu, if the fault is removed at 0.3 s, the system will transition to a transient stable equilibrium state; however, if the fault is removed at 0.5 s, the system will not be able to maintain transient stability. Therefore, the post-fault removal time also affects the system transient stability results. From the comparison between Case 3 and Case 4, we can see that when the grid voltage drops to 0.095 pu, the fault is cleared at 0.5 s, and the voltage injected during the fault is (i tdref ,i tqref)=(0.5 pu, 0.1 pu), the system will transition to a transient stable equilibrium state; however, if the injection during the fault is (i tdref , i tqref )=(0.8 pu, 1 pu), the system will not be able to maintain transient stability. Therefore, the current injection during the fault also affects the transient stability result of the system.

[0080] Specifically, considering a fault occurring on the grid side, the entire fault process can be divided into three stages: before the fault, during the fault, and after the fault. The outer-loop control strategies under different stages are as Figure 4 shown. Figure 4 In, P f represents the filtered input active power, k pP represents the proportional coefficient of the active outer-loop PI link, k iP represents the integral coefficient of the active outer-loop PI link, V acf represents the filtered AC voltage value, V acref represents the AC voltage reference value, V ac represents the AC voltage, k pv represents the proportional coefficient of the reactive outer-loop PI link, k iv represents the integral coefficient of the reactive outer-loop PI link, P in represents the active power reference value after adjusting the power recovery rate.

[0081] Schematically, it can be seen from Figure 4 that: Before the fault (t < t0): The active and reactive currents are generated by the active power control (P control) and the AC voltage control (Vac control). To filter out high-frequency disturbances, the detected values of the active power P and the AC voltage Vac are usually low-pass filtered, and τ is the recovery rate time constant of the active power. It should be noted that in different scenarios, the active and reactive outer-loop controls can also adopt the DC voltage control and the reactive power control. During the fault (t0 < t < t F [[ID=3`6]]):After the fault occurs, the voltage at the PCC (grid connection) point drops, and the active and reactive currents switch to the low-voltage ride-through (LVRT) control. At the same time, the input of the integral controller under the normal control strategy is set to zero. During the fault, i tdref and i[[ID=3`9]] tqref are directly given by the LVRT control strategy. After the fault (t > t F ):After the fault is cleared, the voltage at the PCC point rises, and the active and reactive currents switch to the normal control strategy. When τ = 0, it means that P ref directly returns to the given value; when τ ≠ 0, it means that P ref needs to return to the given value at a certain rate. Therefore, based on the assumptions, the non-linear mathematical models of the WG-VSC system before, during, and after the fault can be obtained for transient stability analysis.

[0082] Step S102: constructing a pre-fault nonlinear mathematical model of the power system based on the power data and the initial power system operating state quantity, and solving the pre-fault nonlinear mathematical model to obtain a first power system operating state quantity of the power system at the beginning of the fault;

[0083] Specifically, after solving the above nonlinear mathematical model before the fault, the phase-locked loop output phase angle θ' at the beginning of the fault is obtained. pll , and the integral x' of the q-axis component of the AC voltage at the beginning of the fault pll , when the fault starts, the integral of the difference between the active power tracking reference value and the active power is x' p , and x', which represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage at the beginning of the fault V , where θ' pll and x' pll As the above-mentioned first power system operating state quantity.

[0084] Specifically, the pre-fault nonlinear mathematical model is an algebraic-differential equation. Therefore, it is iteratively solved using common numerical methods, such as numerical methods, until the difference between the power system operating state quantities obtained in two consecutive iterations is less than a preset threshold. This yields the first power system operating state quantity. At the initial iteration moment, the initial power system operating state quantity is substituted into this equation.

[0085] In a preferred embodiment, the above-mentioned pre-fault nonlinear mathematical model is:

[0086]

[0087] Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, V tq represents the q-axis component of the AC voltage at the grid connection point, x p It represents the integral of the difference between the active power tracking reference value and the active power before the fault, P ref Indicates the tracking reference value of active power, P represents active power, x VIt represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, k i1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

[0088] Specifically, before the fault, the system active and reactive currents are given by the normal outer loop control strategy. Therefore, the interaction between the phase-locked loop and the outer loop is considered to construct the above-mentioned pre-fault nonlinear mathematical model.

[0089] In this preferred embodiment, a pre-fault nonlinear mathematical model is constructed using relevant power data and initial power system operating state quantities when there is no fault.

[0090] Step S103: constructing a nonlinear mathematical model corresponding to each injected current based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, and solving the nonlinear mathematical model to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0091] Specifically, the nonlinear mathematical model of the fault is also an algebraic-differential equation. When solving it, the first power system operating state quantity is substituted as the value used in the first iteration, and finally the second power system operating state quantity is obtained. Among them, the second power system operating state quantity includes: the phase-locked loop output phase angle θ" when the fault is cleared pll , the integral x″ of the q-axis component of the AC voltage when the fault is cleared pll , when the fault is cleared, the integral of the difference between the active power tracking reference value and the active power x″ P , and the integral x″ of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage when the fault is cleared V .

[0092] In a preferred embodiment, the above-mentioned nonlinear mathematical model corresponding to each injected current is constructed based on the above-mentioned equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient and the above-mentioned first power system operation state quantity, and the above-mentioned nonlinear mathematical model is solved to obtain the second power system operation state quantity corresponding to each injected current when the fault is eliminated, including:

[0093] Get the preset maximum output current;

[0094] Calculate the minimum injection current based on the preset maximum output current and the equivalent resistance;

[0095] Calculate the maximum injection current based on the preset maximum output current and the equivalent reactance;

[0096] Determining a current value range of the injection current according to the minimum injection current and the maximum injection current;

[0097] Acquire a plurality of injection currents from the current value range according to a preset step size, and for each injection current, construct a nonlinear mathematical model of the fault corresponding to each injection current based on the injection current, a phase-locked loop proportional coefficient, an equivalent fault network voltage, a phase-locked loop integral coefficient, and the first power system operating state quantity;

[0098] Specifically, from the above examples 2 and 4, it can be seen that the injection of reference current during the fault period will affect the equilibrium state of the system at the time of removal, and further affect the transient stability of the system during the entire fault process. Therefore, constructing the current feasible region helps to intuitively determine the given reference current during the system fault period and judge whether the system will transition to a stable state after the fault. Therefore, the injection current feasible region is the key to ensure the transient stability of the PLL synchronization of the WG-VSC system after the fault. tqref and i tdref It is worth noting that the “after the fault” mentioned in the definition covers both situations where the fault is not removed and after the fault is removed.

[0099] Specifically, the linear function relationship between the active and reactive currents of the power system in a fault state and the equivalent resistance and equivalent reactance is defined as:

[0100] f(I)=X e I tdref -R e I tqref

[0101] Where f(I) represents the linear function relationship of active and reactive currents with respect to equivalent resistance and equivalent reactance (i.e., the linear function expression of the injection current mentioned above). When the function value of f(I) is given and set to c, the nonlinear mathematical model of the fault can be obtained. At this time, the operating limit of the VSC output current (i.e., the preset maximum output current) I is also considered. m , the value range of c is (-R e I m , X e I m ). Then, according to the preset step size ε, several injection currents can be obtained from the current value range.

[0102] Preferably, the preset maximum output current is 1.2 pu.

[0103] Solving the nonlinear mathematical model of the above fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0104] Among them, the nonlinear mathematical model of the above fault is:

[0105]

[0106] Where c represents the linear function expression of the above injection current, θ′ pll The phase angle of the phase-locked loop output when the fault starts, x′ pll It represents the integral of the q-axis component of the AC voltage at the beginning of the fault.

[0107] Specifically, during the fault period i tqref and i tdref Given directly by the LVRT control strategy, the mathematical model of the WG-VSC system during the fault period only includes the PLL dynamics, and then the nonlinear mathematical model of the fault mentioned above is obtained.

[0108] In this preferred embodiment, a nonlinear mathematical model of the fault corresponding to each injected current is constructed and solved to obtain the second power system operating state quantity corresponding to each injected current.

[0109] Step S104: constructing a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solving the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current;

[0110] Specifically, the nonlinear mathematical model after the fault is also an algebraic-differential equation. By solving it, the operating state quantity of the third power system is obtained as follows: the phase angle of the phase-locked loop output after the fault is removed, the integral of the q-axis component of the AC voltage after the fault is removed, the integral of the difference between the tracking reference value of the active power after the fault is removed and the active power, and the integral of the difference between the tracking reference value of the AC voltage at the grid connection point and the amplitude of the AC voltage at the grid connection point after the fault is removed.

[0111] In a preferred embodiment, the above-mentioned post-fault nonlinear mathematical model is:

[0112]

[0113] Where, P in represents the input active power reference value after adjusting the power recovery rate, τ represents the active power recovery rate time constant, θ″ pllIndicates the phase angle of the phase-locked loop output when the fault is cleared, x″ pll represents the integral of the q-axis component of the AC voltage when the fault is cleared, x″ P Indicates the integral of the difference between the active power tracking reference value and the active power when the fault is cleared, x″ V It represents the integral of the difference between the tracking reference value of the AC voltage at the grid connection point and the amplitude of the AC voltage at the grid connection point when the fault is cleared.

[0114] Specifically, after a fault, compared with before the fault, the power ramp after the fault is removed is considered to construct the above-mentioned nonlinear mathematical model after the fault.

[0115] As can be seen from the three-stage nonlinear mathematical models constructed above, the pre-fault model has a system order of 4, and the control mode is outer-loop control coupled with a phase-locked loop (PLL); the fault-induced model has a system order of 2, and the control mode is PLL; and the post-fault model has a system order of 5, and the control mode is outer-loop, PLL, and weak-grid dynamic coupling. Based on these results, the mathematical model of the WG-VSC under fault transient switching control exhibits four characteristics: high order, strong nonlinearity, strong coupling, and transient switching. These characteristics pose challenges to transient synchronous stability analysis.

[0116] Specifically, based on the above three nonlinear mathematical models, a unified rotor motion equation is established:

[0117]

[0118] Where, represents the second-order derivative of the phase-locked loop, represents the first-order derivative of the phase-locked loop, represents the first-order derivative of the q-axis injected current, represents the first-order derivative of the d-axis injection current, P mmeq Indicates equivalent mechanical power, P eeq represents the equivalent electromagnetic power, D represents the equivalent damping, and J represents the equivalent inertia.

[0119] Since the system models are different at different stages, the specific details of P mmeq and P eeq The expression is shown in Table 3:

[0120] Table 3

[0121]

[0122]

[0123] And P mmeq0 and P mmeq2The expression is very complex, so the numerical integration method is used to draw it. Therefore, the equal area law reveals the mechanism of the whole fault process. The schematic diagram is as follows Figure 5 shown. Figure 5 In the figure, the horizontal axis is and the vertical axis is, S acc represents the acceleration area, S dec Indicates the deceleration area.

[0124] Specifically, from Table 3 and Figure 5 It can be seen that at t = t0, δ = δ0, a system failure occurs, P mmeq1 >P eeq1 ,δ starts to accelerate until the fault removal point C, forming the acceleration area S acc At t = t F When δ=δ F , system fault removal, P mmeq2 <P eeq2 , δ begins to decelerate until P mmeq2 =P eeq2 , that is, δ=δ F , forming the maximum deceleration area S dec.max If S acc ≤S dec.max , the system can recover transient stability after the fault is removed; if S acc >S dec.max , the system will be transiently unstable after the fault is removed.

[0125] In this preferred embodiment, a post-fault nonlinear mathematical model corresponding to each injected current is constructed using the power data and the second power system operating state quantity.

[0126] Step S105: based on the third power system operating state quantity, draw the operating trajectory of the power system after the fault corresponding to each injection current, and determine the feasible region of the injection current based on the operating trajectory.

[0127] Specifically, each injected current corresponds to a set of third power system operating state quantities, and thus the phase trajectory method is used to plot them one by one to obtain the operating trajectory of each injected current.

[0128] In a preferred embodiment, determining the feasible region of the injected current according to the operating trajectory includes:

[0129] After obtaining each running trajectory, determine whether the running trajectory converges within a preset time period;

[0130] If converged, the injection current corresponding to the above operation trajectory is used as the target injection current; otherwise, the corresponding injection current is used as the non-target injection current;

[0131] According to all target injection currents, the injection current feasible region is generated.

[0132] Schematically, the construction result of the current feasible region in the case of Example 1 is shown in the figure below: Figure 6 As shown, during the fault period, (i tdref ,i tqref )=(0.5pu,1pu), without considering fault removal (i.e. t=+∞), point A1 is outside the constructed feasible region of injected current, and the system is transiently unstable. The construction results of the current feasible region in the cases 2 and 4 are shown in the figure below. Figure 7 As shown, during the fault period, (i tdref ,i tqref )=(0.8pu,1pu), considering that the fault is removed at t=0.5s, point A4 is outside the current feasible domain, and the system is still transiently unstable; if it is removed at t=0.3s, if only the transient stability constraint is considered, point A2 will be within the injection current feasible domain, and the system is transiently stable, but due to the inverter overcurrent constraint, the system still cannot operate at this operating point. The above simulation phenomenon is based on the mathematical model and does not consider the relay protection action, so the system is transiently stable. The construction results of the current feasible domain in the cases 3 and 4 are shown in the figure Figure 8 As shown, in the above-mentioned cases 3 and 4, during the fault period, the injection (i tdref ,i tqref )=(0.8pu,1pu), considering the fault is cleared at t=0.5s, point A4 is outside the current feasible region, the system transient stability operation constraint and the inverter overcurrent constraint are both satisfied, so the active / reactive reference current is injected during the fault period, and the system transient instability; while the current injected during the fault period (i tdref ,i tqref )=(0.5pu,1pu), point A3 is in the current feasible region, that is, the system is transiently stable.

[0133] Specifically, the factors affecting the above phenomenon are analyzed: if the removal time is too long, it may cause the reference current setting value during the fault period to be outside the feasible region of the injected current, resulting in transient instability of the WG-VSC. At this time, the time period after the fault occurs is generally divided into two parts: the first part: t = (t F ,T lim ), with the increase of the removal time, the feasible region of the injected current after the system is disturbed is reduced, and for any voltage drop, there is a critical removal time T max , when t>T max , the system will experience transient instability. Schematically, the effect of the cut-off time on the feasible region of the injected current is shown in the figure below. Figure 9 As shown, Figure 9The horizontal axis represents the reference value of the reactive injection current in the d-axis direction, and the vertical axis represents the reference value of the reactive injection current in the q-axis direction. Taking point A (id, iq) = (0.5pu, 0.6pu) and point B (id, iq) = (0.55pu, 0.6pu) as an example, the simulation results of point A and point B are shown in the following figure. Figure 10 As shown. The second part, t=(T lim ,+∞), when the removal time continues to increase until t=T lim , the feasible region of injected current no longer changes, and the transient stability of the system is no longer affected by the cut-off time. Figure 9 For example, T lim = 6.1s, when the removal time continues to increase, that is, t> 6.1s, the feasible region of the injected current remains unchanged. Taking point C(id, iq) = (0.28pu, 1pu) and point D(id, iq) = (0.35pu, 1pu) as an example, the simulation results when point C and point D are not removed are shown in the following figure. Figure 11 shown.

[0134] Specifically, the factors affecting the above phenomenon are analyzed: 2. Analysis of the impact of power recovery rate: After the fault is removed, the voltage at the PCC point increases, and the active and reactive currents switch to normal control strategies. In order to prevent the power shock to the system when the active power switches to the normal value, a first-order low-pass filter is used to limit its recovery rate, that is,

[0135]

[0136] Where, Indicates the input active power derivative.

[0137] Therefore, as the first-order low-pass filter coefficient changes, the transient stability of the system will be affected accordingly. Taking the removal time t = 0.3s as an example, the effect of the power recovery rate on the current feasible region after removal is shown in the following diagram: Figure 12 As shown, Figure 12 The feasible domain of injection current when τ is 0s, 0.08s and 0.2s is shown in Figure 2. Taking point D(id,iq)=(0.75pu,0.4pu) as an example, the simulation result diagram of point D is shown in Figure 2. Figure 13 As shown in the figure, when τ = 0s, the active power recovers instantaneously and the system becomes unstable, corresponding to point D outside the current feasible region at τ = 0s. When τ = 0.2s, the system becomes transiently stable after the disturbance, corresponding to point D within the current feasible region at τ = 0.2s. Therefore, as the first-order low-pass filter coefficient increases, the transient stability of the system increases.

[0138] Taking point E(id,iq)=(0.8pu,0.4pu) as an example, the simulation result diagram of point E is as follows: Figure 14 As shown in Figure 2. When τ = 0s, active power recovers instantaneously, causing the system to become unstable, corresponding to point E outside the feasible current region at τ = 0s. When τ = 0.2s, although active power recovers after the first-order lag, the system remains unstable, corresponding to point E outside the feasible current region at τ = 0.2s. Therefore, increasing the first-order low-pass filter coefficient has limited effect on improving system transient stability.

[0139] In this preferred embodiment, the injection current used to generate the injection current feasible region is determined by judging whether each operation trajectory can converge within a preset time period.

[0140] In another preferred embodiment, after determining the feasible region of the injection current, the method further includes:

[0141] Obtaining a current injection current of the power system, and comparing the current injection current with the injection current feasible region;

[0142] When the current injected current is not within the feasible region of the injected current, it is determined that the current power system has not recovered stability, and an early warning is issued.

[0143] Specifically, if the current injection current is not within the feasible region of injection current, it means that the node voltage in the current power system may deviate from the normal range, thereby threatening the stability of the system; or the equipment in the current power system is overloaded, accelerating insulation aging, or even causing failures, destroying the stable operation of the system; or there is an imbalance in reactive power in the current power system. All of the above will cause the power system to have problems with stability not being restored. Therefore, an early warning needs to be issued at this time to remind relevant personnel to inspect and troubleshoot the power system.

[0144] In this preferred embodiment, by issuing an early warning when the current injected current is not within the feasible region of the injected current, the stability of the power system is judged.

[0145] Based on the above method embodiments, the present invention provides corresponding device embodiments.

[0146] like Figure 15 As shown, an embodiment of the present invention provides a device for constructing a feasible region of injected current considering the entire fault process, including:

[0147] A data acquisition module, a first power system operation state quantity calculation module, a second power system operation state quantity calculation module, a third power system operation state quantity calculation module, and an injection current feasible region determination module;

[0148] The data acquisition module is used to acquire power data of the power system and the initial power system operating state quantity when there is no fault; wherein the power data includes: phase-locked loop proportional coefficient, equivalent resistance, equivalent reactance, equivalent fault network voltage and phase-locked loop integral coefficient;

[0149] The first power system operating state quantity calculation module is used to construct a pre-fault nonlinear mathematical model of the power system based on the power data and the initial power system operating state quantity, and solve the pre-fault nonlinear mathematical model to obtain the first power system operating state quantity of the power system at the beginning of the fault;

[0150] The second power system operating state quantity calculation module is used to construct a nonlinear mathematical model corresponding to each injected current in the fault based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, and solve the nonlinear mathematical model in the fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated;

[0151] The third power system operating state quantity calculation module is used to construct a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solve the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current;

[0152] The injection current feasible region determination module is used to draw the operation trajectory of the power system after the fault corresponding to each injection current according to the third power system operation state quantity, and determine the injection current feasible region according to the operation trajectory.

[0153] In a preferred embodiment, the above-mentioned pre-fault nonlinear mathematical model is constructed as follows:

[0154]

[0155] Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, Vtq represents the q-axis component of the AC voltage at the grid connection point, x p It represents the integral of the difference between the active power tracking reference value and the active power before the fault, P ref Indicates the tracking reference value of active power, P represents active power, x V It represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, k i1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

[0156] It should be noted that the device embodiment described above is merely illustrative, wherein the modules described above as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. In addition, in the drawings of the device embodiment provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which can be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art can understand and implement it without paying any creative work. The above schematic diagram is only an example of a construction device for a feasible domain of injection current taking into account the entire fault process, and does not constitute a limitation on a construction device for a feasible domain of injection current taking into account the entire fault process, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components.

[0157] Based on the above method embodiment, the present invention provides a corresponding terminal device embodiment.

[0158] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the above-mentioned memory and configured to be executed by the above-mentioned processor. When the above-mentioned processor executes the above-mentioned computer program, it implements the above-mentioned method for constructing a feasible domain of injection current considering the entire fault process in any embodiment of the present invention.

[0159] For example, in this embodiment, the computer program may be divided into one or more modules, which are stored in the memory and executed by the processor to implement the present invention. The one or more modules may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution process of the computer program in the device.

[0160] The terminal device may be a computing device such as a desktop computer, a notebook computer, a PDA, or a cloud server. The device may include, but is not limited to, a processor and a memory;

[0161] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the above-mentioned device, connecting various parts of the entire device using various interfaces and lines;

[0162] The above-mentioned memory can be used to store the above-mentioned computer programs and / or modules. The above-mentioned processor realizes various functions of the above-mentioned device by running or executing the computer programs and / or modules stored in the above-mentioned memory, and calling the data stored in the memory. The above-mentioned memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required for a function, etc.; in addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage device.

[0163] Based on the above method embodiment, the present invention provides a corresponding storage medium embodiment.

[0164] Another embodiment of the present invention provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the method for constructing a feasible domain of injected current considering the entire fault process described in any embodiment of the present invention.

[0165] In this embodiment, the storage medium is a computer-readable storage medium, and the computer program includes computer program code, which may be in source code form, object code form, an executable file, or some intermediate form. The computer-readable medium may include any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a mobile hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunications signal, and a software distribution medium.

[0166] The above is 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 principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for constructing a feasible region of injected current considering the entire fault process, characterized in that: include: Acquire power data of the power system and initial power system operating state quantities when there is no fault; wherein the power data includes: phase-locked loop proportional coefficient, equivalent resistance, equivalent reactance, equivalent fault network voltage and phase-locked loop integral coefficient; Constructing a pre-fault nonlinear mathematical model of the power system based on the power data and the initial power system operating state quantity, and solving the pre-fault nonlinear mathematical model to obtain a first power system operating state quantity of the power system at the beginning of the fault; Constructing a nonlinear mathematical model of the fault corresponding to each injected current based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operating state quantity, and solving the nonlinear mathematical model of the fault to obtain a second power system operating state quantity of the power system when the fault is eliminated, corresponding to each injected current; constructing a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solving the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current; According to the third power system operating state quantity, an operating trajectory of the power system after a fault corresponding to each injected current is drawn, and the injected current feasible region is determined according to the operating trajectory.

2. The method for constructing a feasible region of injected current considering the entire fault process according to claim 1, characterized in that: The nonlinear mathematical model before the fault is: Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, V tq represents the q-axis component of the AC voltage at the grid connection point, x p The integral of the difference between the tracking reference value of the active power before the fault and the active power, P ref Indicates the tracking reference value of active power, P represents active power, x V It represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage before the fault and the amplitude of the grid-connected point AC voltage, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, k i1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

3. The method for constructing a feasible region of injected current considering the entire fault process according to claim 2, characterized in that: The method includes constructing a nonlinear mathematical model corresponding to each injected current according to the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient, and the first power system operation state quantity, and solving the nonlinear mathematical model to obtain a second power system operation state quantity corresponding to each injected current when the fault is eliminated, including: Get the preset maximum output current; Calculating a minimum injection current based on the preset maximum output current and the equivalent resistance; Calculating a maximum injection current based on the preset maximum output current and the equivalent reactance; Determining a current value range of the injection current according to the minimum injection current and the maximum injection current; Acquire a plurality of injection currents from the current value range according to a preset step size, and for each injection current, construct a nonlinear mathematical model of the fault corresponding to each injection current based on the injection current, a phase-locked loop proportional coefficient, an equivalent fault network voltage, a phase-locked loop integral coefficient, and the first power system operating state quantity; Solving the nonlinear mathematical model of the fault to obtain a second power system operating state quantity corresponding to each injected current when the fault is eliminated; The nonlinear mathematical model of the fault is: Where c represents the linear function expression of the injection current, θ′ pll The phase angle of the phase-locked loop output when the fault starts, x′ pll It represents the integral of the q-axis component of the AC voltage at the beginning of the fault.

4. The method for constructing a feasible region of injected current considering the entire fault process according to claim 3, characterized in that: The post-fault nonlinear mathematical model is: Where, P in represents the input active power reference value after adjusting the power recovery rate, τ represents the active power recovery rate time constant, θ″ pll Indicates the phase angle of the phase-locked loop output when the fault is cleared, x″ pll represents the integral of the q-axis component of the AC voltage when the fault is cleared, x″ P Indicates the integral of the difference between the active power tracking reference value and the active power when the fault is cleared, x″ V It represents the integral of the difference between the tracking reference value of the AC voltage at the grid connection point and the amplitude of the AC voltage at the grid connection point when the fault is cleared.

5. The method for constructing a feasible region of injected current considering the entire fault process according to claim 4, characterized in that: Determining the injection current feasible region according to the operation trajectory includes: After obtaining each running trajectory, determining whether the running trajectory converges within a preset time period; If converged, the injection current corresponding to the running trajectory is used as the target injection current; otherwise, the corresponding injection current is used as the non-target injection current; The injection current feasible region is generated according to all target injection currents.

6. The method for constructing a feasible region of injected current considering the entire fault process according to claim 5, characterized in that: After determining the feasible region of the injection current, the method further includes: Obtaining a current injection current of the power system, and comparing the current injection current with the injection current feasible region; When the current injected current is not within the feasible region of the injected current, it is determined that the current power system has not recovered stability, and an early warning is issued.

7. A device for constructing a feasible region of injected current considering the entire fault process, characterized in that: include: A data acquisition module, a first power system operation state quantity calculation module, a second power system operation state quantity calculation module, a third power system operation state quantity calculation module, and an injection current feasible region determination module; The data acquisition module is used to acquire power data of the power system and the initial power system operating state quantity when there is no fault; wherein the power data includes: phase-locked loop proportional coefficient, equivalent resistance, equivalent reactance, equivalent fault network voltage and phase-locked loop integral coefficient; The first power system operating state quantity calculation module is used to construct a pre-fault nonlinear mathematical model of the power system based on the power data and the initial power system operating state quantity, and solve the pre-fault nonlinear mathematical model to obtain the first power system operating state quantity of the power system at the beginning of the fault; The second power system operation state quantity calculation module is used to construct a nonlinear mathematical model of the fault corresponding to each injected current based on the equivalent resistance, equivalent reactance, phase-locked loop proportional coefficient, equivalent fault network voltage, phase-locked loop integral coefficient and the first power system operation state quantity, and solve the nonlinear mathematical model of the fault to obtain a second power system operation state quantity of the power system when the fault is eliminated, corresponding to each injected current; The third power system operating state quantity calculation module is used to construct a post-fault nonlinear mathematical model corresponding to each injected current based on the second power system operating state quantity and the power data, and solve the post-fault nonlinear mathematical model to obtain a third power system operating state quantity corresponding to each injected current; The injection current feasible region determination module is used to draw the operation trajectory of the power system after the fault corresponding to each injection current according to the third power system operation state quantity, and determine the injection current feasible region according to the operation trajectory.

8. The device for constructing a feasible region of injected current considering the entire fault process according to claim 7, characterized in that: The nonlinear mathematical model before the fault is constructed as follows: Where θ pll Indicates the phase angle of the phase-locked loop output before the fault, k p Represents the phase-locked loop proportional coefficient, R e represents the equivalent resistance, i tqref Indicates the reference value of reactive injection current, X e represents the equivalent reactance, i tdref Indicates the reference value of active injection current, V F represents the equivalent fault network voltage, k i Represents the phase-locked loop integral coefficient, x pll represents the integral of the q-axis component of the AC voltage before the fault, V tq represents the q-axis component of the AC voltage at the grid connection point, x p It represents the integral of the difference between the active power tracking reference value and the active power before the fault, P ref Indicates the tracking reference value of active power, P represents active power, x V It represents the integral of the difference between the tracking reference value of the grid-connected point AC voltage and the amplitude of the grid-connected point AC voltage before the fault, V tref Indicates the tracking reference value of the AC voltage at the grid connection point, V td represents the d-axis component of the AC voltage, k p1 Indicates the active outer loop proportional coefficient, k i1 Indicates the active outer loop integral coefficient, k p2 Represents the reactive outer loop proportional coefficient, k i2 Indicates the reactive outer loop integral coefficient.

9. A terminal device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, the method for constructing a feasible domain of injected current considering the entire fault process as described in any one of claims 1 to 6 is implemented.

10. A storage medium, characterized in that: The storage medium includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the method for constructing the injection current feasible domain considering the entire fault process as described in any one of claims 1 to 6.

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