Fault limit clearing time determination method and device

Abstract

The present invention discloses a method and a device for determining the fault critical clearing time. Wherein, the method includes: determining a target motor and the receiving-end system corresponding to the target motor; determining an equivalent circuit model according to the receiving-end system and the target motor; when the receiving-end system is in a fault state, determining, based on the equivalent circuit model, the critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and the first slip value corresponding to the critical slip value; based on the first slip value, determining whether the target motor satisfies the stable operating condition after performing a preset fault clearing process on the receiving-end system; when the judgment result is that the target motor satisfies the stable operating condition, determining the fault critical clearing time corresponding to the receiving-end system based on the critical slip value. The present invention solves the technical problems in the related art that due to the fluctuation of the power grid fault critical clearing time, the system operation stability is poor and the evaluation accuracy of the fault critical clearing time is low.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular, to a method and device for determining the fault critical clearing time. Background Technique

[0002] Currently, in the context of the vigorous development of new energy, there are many grid-connected operations of new energy systems in the power system, such as wind power systems. The access of new energy systems has an important impact on the stability of the receiving-end system of the power grid. When a fault occurs in the power grid, the conventional method is to cut off the fault circuit within the fault critical clearing time. However, the existence of new energy systems leads to changes in the fault critical clearing time. In related technologies, intelligent algorithms are often used to evaluate the receiving-end system and select indicators, resulting in long calculation time and inaccurate evaluation of power grid stability. And it fails to provide guidance for the fault critical clearing time and power grid stability evaluation based on the power grid with new energy systems.

[0003] In view of the above problems, no effective solution has been proposed yet. Summary of the Invention

[0004] Embodiments of the present invention provide a method and device for determining the fault critical clearing time, so as to at least solve the technical problems in related technologies that due to the fluctuation of the fault critical clearing time of the power grid, the stability of the system operation is poor and the accuracy of the evaluation of the fault critical clearing time is low.

[0005] According to one aspect of an embodiment of the present invention, there is provided a method for determining the fault critical clearing time, including: determining a target motor and a receiving-end system corresponding to the target motor, where the receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electric energy to the target motor; determining an equivalent circuit model according to the receiving-end system and the target motor; in the case that the receiving-end system is in a fault state, based on the equivalent circuit model, determining a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault clearing process on the receiving-end system, and the preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value; based on the first slip value, determining whether the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, where the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault clearing process on the receiving-end system; in the case that the determination result is that the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, determining the fault critical clearing time corresponding to the receiving-end system based on the critical slip value.

[0006] Optionally, the step of, in the case that the receiving-end system is in a fault state, based on the equivalent circuit model, determining a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, includes: in the case that the receiving-end system is in the fault state, based on the equivalent electrical parameters in the equivalent circuit model, determining the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per unit value, fault electromagnetic power per unit value, and fault mechanical power per unit value corresponding to the target motor; based on the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the original stable mechanical power per unit value, the fault electromagnetic power per unit value, and the fault mechanical power per unit value, determining a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value.

[0007] Optionally, determining the critical slip value corresponding to the target motor transitioning from the original stable operating state to the locked-rotor state, and the first slip value corresponding to the critical slip value, based on the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the original stable mechanical power per-unit value, the fault electromagnetic power per-unit value, and the fault mechanical power per-unit value, includes:

[0008] Determining multiple slip solutions corresponding to the target motor in the following manner;

[0009]

[0010] where P M* is the fault electromagnetic power per-unit value, P L* is the fault mechanical power per-unit value, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U1 is the input bus voltage value, P 0* is the original stable mechanical power per-unit value, the solution result of s is the multiple slip solutions, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is a correlation coefficient; taking the largest value among the multiple slip solutions as the critical slip value, and taking the smallest value among the multiple slip solutions as the first slip value.

[0011] Optionally, determining whether the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system based on the first slip value includes: determining the preset kinetic energy change amount, the preset decelerating work amount, and the preset accelerating work amount corresponding to the target motor after performing the preset fault removal process on the receiving-end system based on the first slip value, where the preset kinetic energy change amount is the change in kinetic energy of the target motor before and after performing the preset fault removal process, the preset decelerating work amount is the decelerating work amount of the rotor of the target motor before performing the preset fault removal process, and the preset accelerating work amount is the accelerating work amount of the rotor of the target motor after performing the preset fault removal process; determining the difference between the preset decelerating work amount and the preset accelerating work amount; taking the condition that the difference is less than the preset kinetic energy change amount as the stable operating condition, and determining whether the target motor satisfies the stable operating condition if the preset fault removal process is performed on the receiving-end system.

[0012] Optionally, after determining to perform the preset fault removal process on the receiving-end system based on the first slip value, determining a preset kinetic energy change amount corresponding to the target motor includes: determining an inertia time constant of the rotor of the target motor and an original stable slip value of the target motor during the original stable operation based on equivalent electrical parameters in the equivalent circuit model; determining the preset kinetic energy change amount based on the inertia time constant, the first slip value, and the original stable slip value.

[0013] Optionally, determining the preset kinetic energy change amount based on the inertia time constant, the first slip value, and the original stable slip value includes:

[0014] Determining the preset kinetic energy change amount by the following method:

[0015]

[0016] where, △W K is the preset kinetic energy change amount, T j is the inertia time constant, s1 is the first slip value, and s0 is the original stable slip value.

[0017] Optionally, in the case where the determination result is that after performing the preset fault removal process on the receiving-end system, the target motor satisfies the stable operation condition, determining a fault limit removal time corresponding to the receiving-end system based on the critical slip value includes: after performing the preset fault removal process on the receiving-end system and the target motor satisfies the stable operation condition, obtaining a fault limit slip value based on the critical slip value; determining the fault limit removal time corresponding to the receiving-end system based on the fault limit slip value.

[0018] Optionally, obtaining the fault limit slip value based on the critical slip value includes: obtaining the fault limit slip value by the following method:

[0019]

[0020] where, S3 is the critical slip value, S c is the fault limit slip value, S0 is the original stable slip value of the target motor during the original stable operation, and k is a first correlation coefficient.

[0021] Optionally, determining the fault limit clearing time corresponding to the receiving-end system based on the fault limit slip value includes: determining the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, per-unit value of the original stable mechanical power, and original stable slip value of the target motor based on the equivalent electrical parameters in the equivalent circuit model; and determining the fault limit clearing time corresponding to the receiving-end system according to the fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the per-unit value of the original stable mechanical power, and the original stable slip value.

[0022] Optionally, determining the fault limit clearing time corresponding to the receiving-end system according to the fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the per-unit value of the original stable mechanical power, and the original stable slip value includes: obtaining the fault limit clearing time by the following method according to the fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the per-unit value of the original stable mechanical power, and the original stable slip value:

[0023]

[0024] where, t c is the fault limit clearing time, S c is the fault limit slip value, T j is the inertia time constant, s0 is the original stable slip value, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U1 is the input bus voltage value, P 0* is the per-unit value of the original stable mechanical power, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is the second correlation coefficient.

[0025] According to another aspect of the embodiments of the present invention, a device for determining the fault critical clearing time is provided, including: a first determination module, configured to determine a target motor and a receiving-end system corresponding to the target motor, where the receiving-end system at least includes: a new energy system, and the receiving-end system is configured to supply electric energy to the target motor; a second determination module, configured to determine an equivalent circuit model according to the receiving-end system and the target motor; a first calculation module, configured to, when the receiving-end system is in a fault state, based on the equivalent circuit model, determine a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault clearing process on the receiving-end system, and the preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value; a first judgment module, configured to, based on the first slip value, judge whether the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, where the stable operating condition is the condition that needs to be satisfied for the target motor to enter a new stable operating state after performing the preset fault clearing process on the receiving-end system; a third determination module, configured to, when the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, based on the critical slip value, determine the fault critical clearing time corresponding to the receiving-end system.

[0026] In an embodiment of the present invention, a target motor and a receiving-end system corresponding to the target motor are determined, where the receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electric energy to the target motor; an equivalent circuit model is determined according to the receiving-end system and the target motor; when the receiving-end system is in a fault state, based on the equivalent circuit model, a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value are determined, where the first slip value is the slip value when the target motor enters a new stable operating state after performing a preset fault removal process on the receiving-end system, and the preset fault removal process is a fault removal performed on the receiving-end system when the target motor is at the critical slip value; based on the first slip value, it is determined whether the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, where the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault removal process on the receiving-end system; when the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, based on the critical slip value, the fault limit removal time corresponding to the receiving-end system is determined. The purpose of improving the accuracy of the fault limit removal time for a power grid with a new energy system is achieved, and the technical effect of improving the stability of the operation of a power grid with a new energy system is realized. Furthermore, the technical problem in the related art that due to fluctuations in the power grid fault limit removal time, the system operation stability is poor and the evaluation accuracy of the fault limit removal time is low is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0028] Figure 1 is a flowchart of an optional method for fault limit removal time according to an embodiment of the present invention;

[0029] Figure 2 is an equivalent schematic diagram of an optional method for fault limit removal time according to an embodiment of the present invention;

[0030] Figure 3 is an equivalent schematic diagram of another optional method for fault limit removal time according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of the electromagnetic torque change of an optional method for fault limit removal time according to an embodiment of the present invention;

[0032] Figure 5 It is a schematic diagram of an optional method for the fault critical clearing time provided according to an embodiment of the present invention;

[0033] Figure 6 It is a schematic diagram of another optional method for the fault critical clearing time provided according to an embodiment of the present invention;

[0034] Figure 7 It is a schematic diagram of an optional device for determining the fault critical clearing time provided according to an embodiment of the present invention. Detailed implementation manners

[0035] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily need to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0037] For the convenience of description, some nouns or terms related to the embodiments of the present application are described below:

[0038] Slip is the difference between the rotational speed of the stator rotating magnetic field of the generator and the rotor speed, and is the frequency difference between the generator voltage and the system voltage frequency.

[0039] The fault critical clearing time is the time elapsed from the moment of the fault occurrence to the moment when the corresponding circuit breaker automatically trips to cut off the fault, and is the sum of the protection system action time when the motor can recover from the transient state and the circuit breaker action time.

[0040] According to an embodiment of the present invention, a method embodiment of a method for determining the fault critical clearing time is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that here.

[0041] Figure 1 is a method for determining the fault critical clearing time according to an embodiment of the present invention. As Figure 1 shown, the method includes the following steps:

[0042] Step S102, determine the target motor and the receiving-end system corresponding to the target motor. Among them, the receiving-end system at least includes: a new energy system, and the receiving-end system is used to provide electrical energy for the target motor;

[0043] Step S104, determine an equivalent circuit model according to the receiving-end system and the target motor;

[0044] Step S106, when the receiving-end system is in a fault state, based on the equivalent circuit model, determine the critical slip value corresponding to the target motor transitioning from the original stable operating state to the locked-rotor state, and the first slip value corresponding to the critical slip value. Among them, the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault clearing process on the receiving-end system. The preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value;

[0045] Step S108, based on the first slip value, determine whether the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system. Among them, the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault clearing process on the receiving-end system;

[0046] Step S110, when the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, determine the fault critical clearing time corresponding to the receiving-end system based on the critical slip value.

[0047] Through the above steps, the purpose of improving the accuracy of the fault critical clearing time for a power grid with a new energy system can be achieved, and the technical effect of improving the stability of the operation of a power grid with a new energy system is realized. Furthermore, the technical problems in the related art, such as poor system operation stability and low evaluation accuracy of the fault critical clearing time due to fluctuations in the fault critical clearing time of the power grid, are solved.

[0048] In the method for calculating the critical clearing time of a fault provided by the embodiments of the present invention, in order to obtain a highly accurate critical clearing time of a fault, first, the target motor and the receiving-end system including a new energy system are equivalently processed to obtain an equivalent circuit model. When the receiving-end system is in a fault state, according to the above equivalent circuit model, the critical slip value corresponding to the target motor transitioning from the original stable operating state to the stalled state is determined, as well as the first slip value corresponding to the above critical slip value. The first slip value is the slip value corresponding to the target motor when it enters a new stable operating state after performing a preset fault clearing process on the receiving-end system. Since performing the fault clearing at an inappropriate critical clearing time may lead to the serious consequence that the power grid cannot resume stable operation, before performing the actual fault clearing process, it is necessary to pre-determine whether the target motor can return to a new stable state. The preset fault clearing process is the fault clearing performed on the receiving-end system when the target motor is at the critical slip value. If, after performing the above preset fault clearing process, the target motor will return to the operating state corresponding to the first slip value, it is necessary to further determine whether the target motor meets the stable operation conditions. When the judgment result is that after performing the preset fault clearing process on the receiving-end system, the target motor meets the stable operation conditions, it is considered that after actually performing the fault clearing at the critical slip value, the target motor can stably operate in the operating state corresponding to the first slip value. Therefore, based on the critical slip value, the critical clearing time corresponding to the receiving-end system is determined.

[0049] Optionally, there can be multiple types of the above new energy systems, for example: a wind power system.

[0050] Optionally, there can be multiple situations where the above receiving-end system is in a fault state. For example: the above fault state can be a double-circuit single-circuit fault. After a double-circuit single-circuit fault occurs, the impedance in the receiving-end system increases, and the electromagnetic torque provided to the target motor will decrease, and the balance with the mechanical torque is broken. When the electromagnetic torque is less than the mechanical torque, the speed of the target motor will slowly decrease, and the slip value of the target motor will gradually increase. If no treatment is performed after exceeding the critical clearing time, the receiving-end system will collapse and the target motor will stall.

[0051] Optionally, there can be multiple ways to determine the above equivalent circuit model. For example: the Thevenin two-port network equivalent method is used to obtain the equivalent circuit model.

[0052] It should be noted that when the target motor is operating normally and stably, the electrical energy provided by the receiving-end system to the target motor keeps the electromagnetic torque and mechanical torque of the target motor in a balanced state, which is regarded as the electromagnetic torque being equal to the mechanical torque. When a fault such as a single-circuit of a double-circuit line occurs, the electromagnetic torque of the target motor will be less than the mechanical torque, resulting in a torque deficit. After the fault is removed according to the appropriate fault critical clearing time, the relay protection device in the fault circuit will quickly remove the fault. At this time, the electromagnetic torque of the target motor increases, making the electromagnetic torque greater than the mechanical torque. The rotor of the target motor starts to accelerate under the action of the excessive electromagnetic torque, the speed of the target motor increases, and the slip value of the target motor decreases until the target motor enters a new stable operating point. After passing through the oscillation stage, the target motor will continue to operate in the new stable operating state.

[0053] It still needs to be noted that since the receiving-end system includes a new energy system, the instability mechanism is different from that of a traditional power grid without a new energy system. When a fault occurs in the circuit of the receiving-end system, it is necessary to remove the fault circuit. Since the receiving-end system will be in an unstable transient state before and after the removal, whether it can return to a new stable operating state after the fault removal is greatly affected by the fault critical clearing time. Determining the appropriate fault critical clearing time is very important for the stability of the power grid. If the selected fault critical clearing time does not meet the requirements of the power grid, a series of serious consequences will occur after the fault removal, such as the collapse of the receiving-end system and the blocking of the target motor.

[0054] In an optional embodiment, when the receiving-end system is in a fault state, based on the above equivalent circuit model, determining the critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked state, and the first slip value corresponding to the critical slip value, includes: when the receiving-end system is in the fault state, based on the equivalent electrical parameters in the above equivalent circuit model, determining the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value corresponding to the target motor; based on the above stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value, determining the critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked state, and the first slip value corresponding to the critical slip value.

[0055] It can be understood that when the receiving-end system is in a fault state, based on the equivalent electrical parameters in the equivalent circuit model, the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value corresponding to the target motor are determined. According to the above-mentioned multiple equivalent electrical parameters, the critical slip value and the first slip value of the target motor are determined.

[0056] In an alternative embodiment, determining the critical slip value corresponding to the target motor transitioning from the original stable operating state to the locked-rotor state, and the first slip value corresponding to the critical slip value, based on the above-mentioned stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value, includes:

[0057] Determine multiple slip solutions corresponding to the target motor in the following manner;

[0058]

[0059] where P M* is the fault electromagnetic power per-unit value, P L* is the fault mechanical power per-unit value, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U1 is the input bus voltage value, P 0* is the original stable mechanical power per-unit value, the solution result of s is the multiple slip solutions, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is the correlation coefficient; the largest value among the multiple slip solutions is taken as the critical slip value, and the smallest value among the multiple slip solutions is taken as the first slip value.

[0060] It can be understood that based on the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value, a mathematical expression is established in the above manner to determine multiple slip solutions corresponding to the target motor, and the largest value is taken as the critical slip value, and the smallest value is taken as the first slip value.

[0061] Optionally, the relationship between the fault electromagnetic power per-unit value and the fault mechanical power per-unit value can be various. For example, the mechanical process of the rotor of the target motor can be expressed as:

[0062]

[0063] Among them, T j is the inertia time constant of the rotor, T M is the electromagnetic torque on the rotor, T L is the mechanical torque, T B is the rated torque, ω is the actual electrical angular velocity, and ω0 is the synchronous electrical angular velocity. S B is the slip reference value, Ω B is the rated value of the mechanical angular velocity of the target motor, and Ω is the mechanical angular velocity of the target motor. Further, the relationship between the per-unit value of the fault electromagnetic power and the per-unit value of the fault mechanical power is established in the following manner:

[0064]

[0065] It should be noted that since the established mathematical expression is a quadratic equation system, it can be expected that there are two slip solutions.

[0066] In an optional embodiment, after determining the above-mentioned first slip value and determining whether to perform the above-mentioned preset fault removal process on the above-mentioned receiving-end system, determining whether the above-mentioned target motor satisfies the stable operation condition includes: based on the above-mentioned first slip value, determining the preset kinetic energy change amount, the preset decelerating work amount, and the preset accelerating work amount corresponding to the above-mentioned target motor after performing the above-mentioned preset fault removal process on the above-mentioned receiving-end system, where the above-mentioned preset kinetic energy change amount is the change amount of the kinetic energy of the above-mentioned target motor before and after performing the above-mentioned preset fault removal process, the above-mentioned preset decelerating work amount is the decelerating work amount corresponding to the rotor of the above-mentioned target motor before performing the above-mentioned preset fault removal process, and the above-mentioned preset accelerating work amount is the accelerating work amount corresponding to the rotor of the above-mentioned target motor after performing the above-mentioned preset fault removal process; determining the difference between the above-mentioned preset decelerating work amount and the above-mentioned preset accelerating work amount; using the condition that the above-mentioned difference is less than the above-mentioned preset kinetic energy change amount as the above-mentioned stable operation condition, and determining whether the above-mentioned target motor satisfies the stable operation condition if the above-mentioned receiving-end system performs the above-mentioned preset fault removal process.

[0067] It can be understood that before and after the receiving-end system performs the preset fault removal process, the energy of the target motor changes. According to the preset kinetic energy change amount, the preset decelerating work amount, and the preset accelerating work amount corresponding to the target motor, it can be determined whether the target motor can enter a new stable operation state. Determine the difference between the preset decelerating work amount and the preset accelerating work amount. When the above-mentioned difference is less than the preset kinetic energy change amount, it is considered that the target motor is in a stable operation.

[0068] Optionally, there are various ways to determine the preset decelerating work amount and the preset accelerating work amount. For example: the included angle between the actual electrical angular velocity and the synchronous electrical angular velocity of the rotor of the target motor is denoted as σ. When the operating state of the target motor changes, σ changes continuously. The following method is used to establish a time-related function:

[0069]

[0070] Combined with the established relationship between the fault electromagnetic power per unit value and the fault mechanical power per unit value:

[0071]

[0072] Among them, T j is the inertia time constant of the rotor, T M is the electromagnetic torque on the rotor, T L is the mechanical torque, T B is the rated torque, ω is the actual electrical angular velocity, and ω0 is the synchronous electrical angular velocity. B is the slip reference value, Ω B is the target motor mechanical angle angular velocity rating, Ω is the target motor mechanical angular velocity. Combined, we get:

[0073]

[0074]

[0075]

[0076] T j (1-s)ds=(P M* -P L* )dt

[0077] Among them, Ω0 is the initial value of the target motor mechanical angular velocity, and p is the correlation coefficient. Integrating the above results, we get:

[0078]

[0079] From the above analysis, we can know that when a fault occurs, such as a single-circuit fault in a double-circuit line, when one of the double-circuit lines is short-circuited to ground through impedance, It indicates the decrease of rotor speed and kinetic energy of the target motor during the fault process. The work done by the electromagnetic power corresponding to the target motor shortage over time is taken as the preset deceleration work, recorded as E A1 Similarly, after the preset fault removal process, the increase in the rotor speed, the increase in the kinetic energy of the target motor, and the work done by the excess electromagnetic power of the target motor over time are taken as the preset acceleration work, recorded as E A2 .

[0080] In an alternative embodiment, after determining to perform the preset fault removal process on the receiving-end system based on the first slip value, the preset kinetic energy change amount corresponding to the target motor includes: determining the inertia time constant of the rotor of the target motor and the original stable slip value of the target motor during the original stable operation based on the equivalent electrical parameters in the equivalent circuit model; determining the preset kinetic energy change amount based on the inertia time constant, the first slip value, and the original stable slip value.

[0081] It can be understood that the inertia time constant and the original stable slip value are determined based on the equivalent electrical parameters in the equivalent circuit model. The preset kinetic energy change amount is determined based on the inertia time constant, the first slip value, and the original stable slip value.

[0082] In an alternative embodiment, the determining the preset kinetic energy change amount based on the inertia time constant, the first slip value, and the original stable slip value includes:

[0083] Determine the preset kinetic energy change amount in the following manner:

[0084]

[0085] where, △W K is the preset kinetic energy change amount, T j is the inertia time constant, s1 is the first slip value, and s0 is the original stable slip value.

[0086] It can be understood that a mathematical expression of the preset kinetic energy change amount is established based on the inertia time constant, the first slip value, and the original stable slip value.

[0087] It should be noted that since the target motor cannot return to the stable operation state after the slip value of the target motor is greater than the critical slip value, the energy change before and after the preset fault removal process is used to represent the stable operation condition. The difference between the preset deceleration work amount and the preset acceleration work amount needs to be less than the change in the kinetic energy of the target motor rotor before and after the fault, and an expression for the stable operation condition can be established as After satisfying the above stable operation condition, the voltage can be considered stable.

[0088] In an alternative embodiment, after the above-mentioned preset fault removal process is performed on the receiving-end system and the target motor meets the above-mentioned stable operation conditions, based on the above-mentioned critical slip value, determining the fault limit removal time corresponding to the receiving-end system includes: after the above-mentioned preset fault removal process is performed on the receiving-end system and the target motor meets the above-mentioned stable operation conditions, based on the above-mentioned critical slip value, obtaining the fault limit slip value; based on the above-mentioned fault limit slip value, determining the fault limit removal time corresponding to the receiving-end system.

[0089] It can be understood that after the preset fault removal process is performed on the receiving-end system and the target motor meets the stable operation conditions, the fault limit slip value is obtained based on the critical slip value. It should be noted that the critical slip value is the slip value when the target motor enters the locked-rotor state. In order to ensure a reasonable operation time in the actual application scenario, the fault limit slip value needs to be slightly less than the critical slip value. According to the fault limit slip value, the fault limit removal time corresponding to the receiving-end system is determined.

[0090] It should be noted that in the actual power grid, considering factors such as the rotor inertia of the target motor, the critical slip value needs to be corrected to ensure that the obtained fault limit slip value is less than the critical slip value.

[0091] In an alternative embodiment, the above-mentioned obtaining the fault limit slip value based on the above-mentioned critical slip value includes: obtaining the above-mentioned fault limit slip value by the following method:

[0092]

[0093] wherein, S3 is the above-mentioned critical slip value, S c is the above-mentioned fault limit slip value, S0 is the original stable slip value of the above-mentioned target motor during the original stable operation, and k is the first correlation coefficient.

[0094] It can be understood that the critical slip value is corrected by the above method to obtain the fault limit slip value.

[0095] Optionally, there can be multiple values for the above-mentioned first correlation coefficient. For example, when the value of the first correlation coefficient is taken as 0.2, the expression for obtaining the fault limit slip value is:

[0096] In an alternative embodiment, determining the fault limit clearing time corresponding to the receiving-end system based on the above-mentioned fault limit slip value includes: determining the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, original steady mechanical power per unit value, and original steady slip value of the target motor based on the equivalent electrical parameters in the above-mentioned equivalent circuit model; determining the fault limit clearing time corresponding to the receiving-end system according to the above-mentioned fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original steady mechanical power per unit value, and the original steady slip value.

[0097] It can be understood that based on the equivalent electrical parameters in the equivalent circuit model, the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, original steady mechanical power per unit value, and original steady slip value of the target motor are determined. The fault limit clearing time is determined according to the above-mentioned multiple equivalent electrical parameters.

[0098] In an alternative embodiment, the determining the fault limit clearing time corresponding to the receiving-end system according to the above-mentioned fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original steady mechanical power per unit value, and the original steady slip value includes: obtaining the fault limit clearing time in the following manner according to the above-mentioned fault limit slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original steady mechanical power per unit value, and the original steady slip value:

[0099]

[0100] where t c is the above-mentioned fault limit clearing time, S c is the above-mentioned fault limit slip value, T j is the above-mentioned inertia time constant, s0 is the above-mentioned original steady slip value, R1 is the above-mentioned stator winding resistance, X1 is the above-mentioned stator winding reactance, R2 is the above-mentioned rotor winding resistance, X2 is the above-mentioned rotor winding reactance, U1 is the above-mentioned input bus voltage value, P 0* is the above-mentioned original steady mechanical power per unit value, A is the first characteristic constant of the above-mentioned target motor, B is the second characteristic constant of the above-mentioned target motor, C is the third characteristic constant of the above-mentioned target motor, and c1 is the second correlation coefficient.

[0101] It can be understood that based on the equivalent electrical parameters in the equivalent circuit model, the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, original stable mechanical power per unit value, and original stable slip value of the target motor during its original stable operation are determined. A mathematical expression for the fault boundary clearing time is established to obtain the fault limit clearing time. Referring to the fault limit clearing time to cut the fault loop of the receiving-end system is beneficial for the target motor to return to a new stable operation state.

[0102] Based on the above embodiments and alternative embodiments, the present invention proposes an alternative implementation manner. For the convenience of understanding, a specific example is given, specifically the following steps:

[0103] Represent the actual power grid system as an equivalent receiving-end system. Figure 2 It is an equivalent schematic diagram of an alternative fault limit clearing time method provided according to an embodiment of the present invention. As Figure 2 shown, E q ∠δ represents the voltage of the infinite power grid system. U1∠θ1 is the voltage of bus 1, U2∠θ2 is the voltage of bus 2, and U3∠θ3 is the voltage of bus 3. X T1 is the equivalent reactance of the step-up transformer, X T2 is the equivalent reactance of the step-down transformer, X L1 and X L2 are different line reactances, R L is the resistance of the constant impedance load, X L is the reactance of the constant impedance load. R1 is the stator winding resistance of the target motor, X1 is the stator winding reactance of the target motor, R2 is the equivalent resistance of the rotor winding, X2 is the equivalent reactance of the rotor winding, X m is the excitation reactance. P W and Q W are the active and reactive powers injected by the doubly-fed wind turbine into the system. As Figure 2 mentioned above, an equivalent model of the receiving-end system is established. Among them, P W is the active power injected by the doubly-fed wind turbine into the power grid system, Q W is the reactive power injected by the doubly-fed wind turbine into the power grid system, R W is an equivalent resistance that does not actually exist, X W is an equivalent reactance that does not actually exist. The variable resistance and reactance equivalent to the injected power of the wind turbine generator set, and the resistance value of its variable impedance is:

[0104]

[0105] Perform Thevenin two-port network equivalence on the circuit in the dashed box of Figure 2 , and the mathematical expression of the obtained equivalent circuit model is:

[0106]

[0107] Among them, E q '∠δ is the terminal electromotive force equivalent to the target motor, R1' is the stator resistance equivalent to the target motor, X1' is the reactance equivalent to the target motor, X m ' is the excitation reactance equivalent to the target motor, R2' is the rotor resistance equivalent to the target motor, X2' is the rotor reactance equivalent to the target motor, j is the imaginary part, R ∑2 is the composite side resistance of the above receiving-end system, X ∑2 is the composite side reactance of the above receiving-end system, R ∑3 is the power supply side resistance of the above receiving-end system, X ∑3 is the power supply side reactance of the above receiving-end system, X ∑1 is the power transmission side reactance of the above receiving-end system. The following relationships exist among the above equivalent electrical parameters:

[0108]

[0109] Figure 3 is an equivalent schematic diagram of another optional fault critical clearing time method provided according to an embodiment of the present invention, as Figure 3 shown, E q '∠δ is the terminal electromotive force equivalent to the target motor, representing the input of the receiving-end system, and represents the equivalent circuit model of the target motor and the receiving-end system. Figure 4 is a schematic diagram of the electromagnetic torque change of an optional fault critical clearing time method provided according to an embodiment of the present invention. When a fault occurs in the receiving-end system, the target motor will be correspondingly affected by the fault, as Figure 4 shown, the influence on the target motor is represented by the relationship between the electromagnetic torque and the slip. The relationship curve between the electromagnetic torque and the slip changes correspondingly with the processing of the fault clearing in the receiving-end system.

[0110] Figure 5 is a schematic diagram of an optional fault critical clearing time method provided according to an embodiment of the present invention, as Figure 5 shown, which is specifically explained by the change of the operating point on the relationship curve between the electromagnetic torque and the slip. When the target motor is in a stable operating state, the electromagnetic torque provided by the receiving-end system to the target motor is denoted as T M is equal to the mechanical torque denoted as T L, Point A is the stable operating point, and at this time the original stable slip value of the target motor is S0. When a fault occurs, such as a single-circuit short-circuit fault in a double-circuit line, the target motor is in a transient process, and the relationship curve between the electromagnetic torque and the slip of the target motor changes from T1 to T3. Due to the rotor inertia of the target motor, the slip of the rotor does not change immediately, and the operating point of the target motor suddenly changes from point A to point B. Assume that the mechanical torque T L remains unchanged, and T M decreases, resulting in an electromagnetic torque deficit. And according to the trend of the T3 curve, it can be seen that the electromagnetic torque deficit will become larger and larger. In the case of insufficient electromagnetic torque, the rotor is braked, the speed decreases, the slip increases, and the operating point moves from point B to point C along the T3 curve. If the fault persists, there will always be an electromagnetic power deficit, and the rotor will continue to decelerate until it stalls. If appropriate fault removal treatment is performed, the relay protection device will quickly act to remove the faulty line after the short-circuit fault. Assume that the fault is removed when the receiving-end system is at the operating point C. Then the relationship curve between the electromagnetic torque and the slip of the target motor becomes the T2 curve. As Figure 5 shown, the operating point of the target motor changes from point C to point D. At this time, the electromagnetic torque T M of the target motor is greater than the mechanical torque T L , and the rotor starts to accelerate under the action of the excess electromagnetic torque, and the slip of the target motor decreases. From the perspective of the relationship curve between the electromagnetic torque and the slip, the operating point moves from point D to point F along the T2 curve. During this process, the rotor of the target motor is in an accelerating process. When reaching point F, the electromagnetic torque of the target motor is balanced with the mechanical torque. Therefore, point F is the new stable operating point of the target motor after the fault removal treatment. However, due to the inertia of the rotor, there will be an oscillation stage before reaching the stable operating point F and stabilizing. The amplitude of the oscillation is determined by the magnitude of the moment of inertia J of the rotor. From the analysis of the transient process of the target motor before and after the fault removal, it can be seen that the slip corresponding to point G is the critical slip value. If the slip of the induction motor rotor crosses point G during the deceleration process, it will stall and cause voltage instability. If it does not cross point G, it can resume normal operation and reach the new operating point F.

[0111] In the case where the receiving-end system is in a fault state, the mechanical process of the rotor of the target motor can be expressed as:

[0112]

[0113] where T j is the inertia time constant of the rotor, T M is the electromagnetic torque on the rotor, T L is the mechanical torque, T B is the rated torque, ω is the actual electrical angular velocity, and ω0 is the synchronous electrical angular velocity. S B is the slip reference value, ΩB is the rated value of the mechanical angular velocity of the target motor, and Ω is the mechanical angular velocity of the target motor. Further, the relationship between the per-unit value of the fault electromagnetic power and the per-unit value of the fault mechanical power is established through the following method:

[0114]

[0115] Based on the equivalent circuit model, through the following method, determine the critical slip value corresponding to the target motor entering the blocked-rotor state from the original stable operating state, and the first slip value corresponding to the critical slip value:

[0116]

[0117] where, P M* is the above-mentioned per-unit value of the fault electromagnetic power, P L* is the above-mentioned per-unit value of the fault mechanical power, R1 is the above-mentioned stator winding resistance, X1 is the above-mentioned stator winding reactance, R2 is the above-mentioned rotor winding resistance, X2 is the above-mentioned rotor winding reactance, U1 is the above-mentioned input bus voltage value, P 0* is the above-mentioned per-unit value of the original stable mechanical power, the solution result of s is the above-mentioned multiple slip solutions, A is the first characteristic constant of the above-mentioned target motor, B is the second characteristic constant of the above-mentioned target motor, C is the third characteristic constant of the above-mentioned target motor, c1 is the correlation coefficient; take the largest value among the above-mentioned multiple slip solutions as the above-mentioned critical slip value, and take the smallest value among the above-mentioned multiple slip solutions as the above-mentioned first slip value.

[0118] Before and after the receiving-end system performs the preset fault removal process, energy changes occur in the target motor. According to the preset kinetic energy change amount, preset decelerating work amount, and preset accelerating work amount corresponding to the target motor, it can be judged whether the target motor can enter a new stable operating state. First, determine the preset decelerating work amount and preset accelerating work amount corresponding to the target motor. The angle between the actual electrical angular velocity and the synchronous electrical angular velocity of the rotor of the target motor is denoted as σ. When the operating state of the target motor changes, σ changes continuously. Through the following method, establish a time-related function:

[0119]

[0120] Combined with the established relationship between the per-unit value of the fault electromagnetic power and the per-unit value of the fault mechanical power:

[0121]

[0122] where, T j is the inertia time constant of the rotor, T M is the electromagnetic torque on the rotor, T L is the mechanical torque, T Bis the rated torque, ω is the actual electrical angular velocity, and ω0 is the synchronous electrical angular velocity. S B is the slip reference value, and Ω B is the rated value of the mechanical angular velocity of the target motor, and Ω is the mechanical angular velocity of the target motor. By combining them, we get:

[0123]

[0124]

[0125]

[0126] T j (1 - s)ds = (P M* - P L* )dt

[0127] where Ω0 is the initial value of the mechanical angular velocity of the target motor, and p is the correlation coefficient. Integrating the above result gives:

[0128]

[0129] From the above analysis, it can be seen that during a fault, such as in a double - circuit single - circuit fault, when one of the double - circuits has a ground short - circuit through an impedance, represents the decrease in the rotor speed during the fault and the decrease in the kinetic energy of the target motor, corresponding to the work done by the deficit electromagnetic power of the target motor over time, which is used as the preset deceleration work amount and denoted as E A1 . Similarly, after the preset fault removal process, the increase in the rotor speed, the increase in the kinetic energy of the target motor, and the work done by the excess electromagnetic power of the target motor over time are used as the preset acceleration work amount and denoted as E A2 . Figure 6 is a schematic diagram of another optional fault - limit removal time method provided according to an embodiment of the present invention. As Figure 6 shown, A1 is the deceleration area, and the size of the corresponding area is used to describe the preset deceleration work amount. A2 is the acceleration area, and the size of the corresponding area is used to describe the preset acceleration work amount. When the energy difference represented by the difference between the areas of A1 and A2 is less than the preset kinetic energy change amount of the target motor rotor before and after the fault, denoted as △W K .

[0130] Determine the difference between the preset deceleration work amount and the preset acceleration work amount. When the above difference is less than the preset kinetic energy change amount, it is considered that the target motor is in stable operation. Determine the above - mentioned preset kinetic energy change amount in the following way:

[0131]

[0132] where △WK is the preset kinetic energy change amount, T j is the above-mentioned inertia time constant, s1 is the above-mentioned first slip value, and s0 is the above-mentioned original stable slip value. Since the slip value of the target motor cannot return to the stable operation state after it is greater than the critical slip value, it is necessary to represent the stable operation condition by using the energy change before and after the preset fault removal process. The difference between the preset deceleration work amount and the preset acceleration work amount needs to be less than the change in the kinetic energy of the target motor rotor before and after the fault, and the expression of the stable operation condition can be established as After satisfying the above stable operation conditions, the voltage can be considered stable.

[0133] Since the receiving-end system includes a new energy system, the instability mechanism is different from that of the traditional power grid without a new energy system. After the fault is removed using the critical slip value, it can return to a new stable operation state (corresponding to the first slip value). In the actual power grid, considering factors such as the inertia of the target motor rotor, it is necessary to correct the critical slip value to ensure that the obtained fault limit slip value is less than the critical slip value. The fault limit slip value is obtained by the following method:

[0134]

[0135] Among them, S3 is the critical slip value, S c is the fault limit slip value, and S0 is the original stable slip value of the target motor during the original stable operation. Based on the equivalent electrical parameters in the equivalent circuit model, determine the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, original stable mechanical power per unit value, and original stable slip value of the target motor during the original stable operation. The fault limit removal time is obtained by the following method:

[0136]

[0137] Among them, t c is the fault limit removal time, S c is the fault limit slip value, T j is the inertia time constant, s0 is the original stable slip value, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U1 is the input bus voltage value, P 0* is the original stable mechanical power per unit value, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is the second correlation coefficient.

[0138] Removing the fault loop of the receiving-end system with reference to the fault critical clearing time is conducive to the target motor restoring to a new stable operation state. To verify the effectiveness of the evaluation method for the voltage stability of the receiving-end system, through Table 1 and Table 2, the critical clearing slip and the critical clearing time of the wind power integrated grid system are simulated and compared. It can be seen that the influence of the access of the new energy system to the receiving-end system is that the critical clearing slip value is smaller compared with the case without the new energy system access, and the corresponding critical clearing time is longer. It should be noted that the following specific values are only for illustrative purposes of the simulation results and do not constitute a limitation.

[0139] Table 1 Schematic comparison of the critical clearing slip of the wind power integrated grid system

[0140]

[0141] Table 2 Schematic comparison of the critical clearing time of the wind power integrated grid system

[0142]

[0143] The above optional implementation manners can at least achieve any one of the following effects: establishing an equivalent circuit model of the receiving-end system and analyzing the mechanism of voltage instability when there is a new energy system. Calculating the critical clearing time of the fault of the receiving-end system according to the transient energy, and using the fault clearing time as an index of the system stability strength. It can realize the quantitative analysis of the voltage stability of the receiving-end system, provide guidance for relevant personnel to evaluate the voltage stability of the receiving-end system, and can evaluate the influence of the access of new energy on the voltage stability of the receiving-end system.

[0144] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0145] In this embodiment, a device for determining the critical clearing time is also provided. This device is used to implement the above embodiments and preferred implementation manners, and those that have been described will not be repeated. As used below, the terms "module" and "device" can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation in hardware, or a combination of software and hardware, is also possible and contemplated.

[0146] According to an embodiment of the present invention, an apparatus embodiment for implementing the method of the critical clearing time is also provided. Figure 7 It is a schematic diagram of a device for determining the critical clearing time according to an embodiment of the present invention, as Figure 7As shown, the above-mentioned fault critical clearing time determination device includes: a first determination module 702, a second determination module 704, a first calculation module 706, a first judgment module 708, and a third determination module 710. The device will be described below.

[0147] The first determination module 702 is configured to determine a target motor and a receiving-end system corresponding to the target motor. The receiving-end system at least includes: a new energy system, and the receiving-end system is configured to supply electric energy to the target motor;

[0148] The second determination module 704 is connected to the first determination module 702 and is configured to determine an equivalent circuit model according to the receiving-end system and the target motor;

[0149] The first calculation module 706 is connected to the second determination module 704 and is configured to, when the receiving-end system is in a fault state, based on the equivalent circuit model, determine a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value. The first slip value is the slip value when the target motor enters a new stable operating state after a preset fault clearing process is performed on the receiving-end system. The preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value;

[0150] The first judgment module 708 is connected to the first calculation module 706 and is configured to, based on the first slip value, judge whether the target motor satisfies the stable operating conditions after the preset fault clearing process is performed on the receiving-end system. The stable operating conditions are the conditions that the target motor needs to satisfy to enter a new stable operating state after the preset fault clearing process is performed on the receiving-end system;

[0151] The third determination module 710 is connected to the first judgment module 708 and is configured to, when the judgment result is that the target motor satisfies the stable operating conditions after the preset fault clearing process is performed on the receiving-end system, determine the fault critical clearing time corresponding to the receiving-end system based on the critical slip value.

[0152] In a device for determining the fault critical clearing time provided by an embodiment of the present invention, a first determination module 702 is provided for determining a target motor and a receiving-end system corresponding to the target motor. The receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electrical energy to the target motor; a second determination module 704, connected to the first determination module 702, for determining an equivalent circuit model according to the receiving-end system and the target motor; a first calculation module 706, connected to the second determination module 704, for determining, when the receiving-end system is in a fault state, a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value when the target motor enters a new stable operating state after performing a preset fault clearing process on the receiving-end system, and the preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value; a first judgment module 708, connected to the first calculation module 706, for judging whether the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system based on the first slip value, where the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault clearing process on the receiving-end system; a third determination module 710, connected to the first judgment module 708, for determining the fault critical clearing time corresponding to the receiving-end system based on the critical slip value when the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system. The purpose of improving the accuracy of the fault critical clearing time for a power grid with a new energy system is achieved, and the technical effect of enhancing the stability of the operation of a power grid with a new energy system is realized. Furthermore, the technical problem in the related art that due to the fluctuation of the power grid fault critical clearing time, the stability of the system operation is poor and the evaluation accuracy of the fault critical clearing time is low is solved.

[0153] It should be noted that the above-mentioned various modules can be implemented by software or hardware. For example, for the latter, it can be implemented in the following ways: the above-mentioned various modules can be located in the same processor; or, the above-mentioned various modules are located in different processors in any combination.

[0154] It should be noted that the above first determination module 702, second determination module 704, first calculation module 706, first judgment module 708, and third determination module 710 correspond to steps S102 to S110 in the embodiment. The examples and application scenarios implemented by the above modules and the corresponding steps are the same, but are not limited to the content disclosed in the above embodiment. It should be noted that the above modules, as part of the device, can run in a computer terminal.

[0155] It should be noted that the optional or preferred implementation manners of this embodiment can be referred to the relevant descriptions in the embodiment, and will not be repeated here.

[0156] The above device for determining the fault critical clearing time may further include a processor and a memory. The first determination module 702, second determination module 704, first calculation module 706, first judgment module 708, third determination module 710, etc. are all stored in the memory as program units, and the corresponding functions are implemented by the processor executing the above program units stored in the memory.

[0157] The processor contains a kernel, and the kernel retrieves the corresponding program unit from the memory. One or more kernels can be set. The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash memory (flash RAM), and the memory includes at least one storage chip.

[0158] An embodiment of the present invention provides a non-volatile storage medium, on which a program is stored, and when the program is executed by a processor, it implements the method for determining the fault critical clearing time.

[0159] An embodiment of the present invention provides an electronic device, which includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, the following steps are implemented: determining a target motor and a receiving-end system corresponding to the target motor, where the receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electrical energy to the target motor; determining an equivalent circuit model according to the receiving-end system and the target motor; in the case that the receiving-end system is in a fault state, based on the equivalent circuit model, determining a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault removal process on the receiving-end system, and the preset fault removal process is a fault removal performed on the receiving-end system when the target motor is at the critical slip value; based on the first slip value, determining whether the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, where the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault removal process on the receiving-end system; in the case that the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, determining the fault limit removal time corresponding to the receiving-end system based on the critical slip value. The device in this article can be a server, a PC, etc.

[0160] The present invention also provides a computer program product which, when executed on a data processing device, is adapted to execute a program initialized with the following method steps: determining a target motor and a receiving-end system corresponding to the target motor, wherein the receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electric energy to the target motor; determining an equivalent circuit model according to the receiving-end system and the target motor; in the case that the receiving-end system is in a fault state, based on the equivalent circuit model, determining a critical slip value corresponding to the target motor transitioning from the original stable operating state to the locked-rotor state, and a first slip value corresponding to the critical slip value, wherein the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault removal process on the receiving-end system, and the preset fault removal process is a fault removal performed on the receiving-end system when the target motor is at the critical slip value; based on the first slip value, determining whether the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, wherein the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault removal process on the receiving-end system; in the case that the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, determining a fault limit removal time corresponding to the receiving-end system based on the critical slip value.

[0161] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0162] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0163] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one process Figure 1 or more processes and / or boxes Figure 1 or more boxes specified in a box.

[0164] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process Figure 1 or more processes and / or boxes Figure 1 or more boxes specified in a box.

[0165] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0166] The memory may include non-permanent memory in the computer-readable medium, in the form of random access memory (RAM) and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.

[0167] Computer-readable media includes permanent and non-permanent, removable and non-removable media and can be implemented by any method or technology for information storage. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media such as modulated data signals and carrier waves.

[0168] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0169] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0170] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for determining the critical clearing time of a fault, characterized in that Including: Determine a target motor and a receiving-end system corresponding to the target motor, where the receiving-end system at least includes: a new energy system, and the receiving-end system is used to supply electric energy to the target motor; Determine an equivalent circuit model according to the receiving-end system and the target motor; When the receiving-end system is in a fault state, based on the equivalent circuit model, determine a critical slip value corresponding to the target motor changing from the original stable operating state to the locked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault removal process on the receiving-end system, and the preset fault removal process is a fault removal performed on the receiving-end system when the target motor is at the critical slip value; Based on the first slip value, determine whether the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, where the stable operating condition is the condition that the target motor needs to satisfy to enter a new stable operating state after performing the preset fault removal process on the receiving-end system; When the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault removal process on the receiving-end system, based on the critical slip value, determine the fault limit removal time corresponding to the receiving-end system.

2. The method according to claim 1, wherein The step of, when the receiving-end system is in a fault state, based on the equivalent circuit model, determining a critical slip value corresponding to the target motor changing from the original stable operating state to the locked-rotor state, and a first slip value corresponding to the critical slip value, includes: When the receiving-end system is in the fault state, based on the equivalent electrical parameters in the equivalent circuit model, determine the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, original stable mechanical power per-unit value, fault electromagnetic power per-unit value, and fault mechanical power per-unit value corresponding to the target motor; Based on the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the original stable mechanical power per-unit value, the fault electromagnetic power per-unit value, and the fault mechanical power per-unit value, determine a critical slip value corresponding to the target motor changing from the original stable operating state to the locked-rotor state, and a first slip value corresponding to the critical slip value.

3. The method according to claim 2, wherein The step of, based on the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the original stable mechanical power per-unit value, the fault electromagnetic power per-unit value, and the fault mechanical power per-unit value, determining a critical slip value corresponding to the target motor changing from the original stable operating state to the locked-rotor state, and a first slip value corresponding to the critical slip value, includes: Determine multiple slip solutions corresponding to the target motor in the following manner; Among them, P M* is the per-unit value of the faulty electromagnetic power, P L* is the per-unit value of the faulty mechanical power, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U 1* is the input bus voltage value, P 0* is the per-unit value of the original stable mechanical power, the solution result of s is the multiple slip solutions, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is the correlation coefficient; Take the largest value among the multiple slip solutions as the critical slip value, and take the smallest value among the multiple slip solutions as the first slip value.

4. The method according to claim 1, wherein Based on the first slip value, determining whether the target motor satisfies the stable operation condition after performing the preset fault removal process on the receiving-end system, includes: Based on the first slip value, determining the preset kinetic energy change amount, preset deceleration work amount, and preset acceleration work amount corresponding to the target motor after performing the preset fault removal process on the receiving-end system, where the preset kinetic energy change amount is the change in kinetic energy of the target motor before and after performing the preset fault removal process, the preset deceleration work amount is the deceleration work amount corresponding to the rotor of the target motor before performing the preset fault removal process, and the preset acceleration work amount is the acceleration work amount corresponding to the rotor of the target motor after performing the preset fault removal process; Determining the difference between the preset deceleration work amount and the preset acceleration work amount; Taking the difference being less than the preset kinetic energy change amount as the stable operation condition, and determining whether the target motor satisfies the stable operation condition if the receiving-end system performs the preset fault removal process.

5. The method according to claim 4, wherein The determining, based on the first slip value, of the preset kinetic energy change amount corresponding to the target motor after performing the preset fault removal process on the receiving-end system, includes: Based on the equivalent electrical parameters in the equivalent circuit model, determining the inertia time constant of the rotor of the target motor and the original stable slip value of the target motor during the original stable operation; Based on the inertia time constant, the first slip value, and the original stable slip value, determining the preset kinetic energy change amount.

6. The method according to claim 5, wherein The determining, based on the inertia time constant, the first slip value, and the original stable slip value, of the preset kinetic energy change amount, includes: Determining the preset kinetic energy change amount in the following manner: where ΔW K is the preset kinetic energy change, T j is the inertial time constant, s1 is the first slip value, and s0 is the original stable slip value.

7. The method according to claim 1, wherein In the case where the judgment result is that the target motor satisfies the stable operation condition after performing the preset fault removal process on the receiving-end system, determining the fault limit removal time corresponding to the receiving-end system based on the critical slip value, includes: In the case where the target motor satisfies the stable operation condition after performing the preset fault removal process on the receiving-end system, obtaining the fault limit slip value based on the critical slip value; Based on the fault limit slip value, determining the fault limit removal time corresponding to the receiving-end system.

8. The method according to claim 7, characterized in that The obtaining, based on the critical slip value, of the fault limit slip value, includes: Obtaining the fault limit slip value in the following manner: Among them, S3 is the critical slip value, S c is the fault limit slip value, S0 is the original stable slip value of the target motor during the original stable operation, and k is the first correlation coefficient.

9. The method according to claim 7, wherein The determining, based on the fault limit slip value, of the fault limit removal time corresponding to the receiving-end system, includes: Based on the equivalent electrical parameters in the equivalent circuit model, determining the stator winding resistance, stator winding reactance, rotor winding resistance, rotor winding reactance, input bus voltage value, inertia time constant, original stable mechanical power per unit value, and the original stable slip value of the target motor during the original stable operation; Determine the fault-limited clearing time corresponding to the receiving-end system according to the fault-limited slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original stable mechanical power per-unit value, and the original stable slip value.

10. The method according to claim 9, wherein The determining of the fault-limited clearing time corresponding to the receiving-end system according to the fault-limited slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original stable mechanical power per-unit value, and the original stable slip value includes: Obtain the fault-limited clearing time through the following manner according to the fault-limited slip value, the stator winding resistance, the stator winding reactance, the rotor winding resistance, the rotor winding reactance, the input bus voltage value, the inertia time constant, the original stable mechanical power per-unit value, and the original stable slip value: where t c is the fault critical clearing time, S c is the fault critical slip value, T j is the inertia time constant, s0 is the original stable slip value, R1 is the stator winding resistance, X1 is the stator winding reactance, R2 is the rotor winding resistance, X2 is the rotor winding reactance, U 1* is the input bus voltage value, P 0* is the per-unit value of the original stable mechanical power, A is the first characteristic constant of the target motor, B is the second characteristic constant of the target motor, C is the third characteristic constant of the target motor, and c1 is the second correlation coefficient.

11. A device for determining the fault critical clearing time, characterized in that, Including: A first determination module, configured to determine a target motor and the receiving-end system corresponding to the target motor, where the receiving-end system at least includes: a new energy system, and the receiving-end system is configured to supply electric energy to the target motor; A second determination module, configured to determine an equivalent circuit model according to the receiving-end system and the target motor; A first calculation module, configured to, when the receiving-end system is in a fault state, based on the equivalent circuit model, determine a critical slip value corresponding to the target motor transitioning from the original stable operating state to the blocked-rotor state, and a first slip value corresponding to the critical slip value, where the first slip value is the slip value corresponding to the target motor entering a new stable operating state after performing a preset fault clearing process on the receiving-end system, and the preset fault clearing process is a fault clearing performed on the receiving-end system when the target motor is at the critical slip value; A first judgment module, configured to, based on the first slip value, judge whether the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, where the stable operating condition is the condition that needs to be satisfied for the target motor to enter a new stable operating state after performing the preset fault clearing process on the receiving-end system; A third determination module, configured to, when the judgment result is that the target motor satisfies the stable operating condition after performing the preset fault clearing process on the receiving-end system, determine the fault-limited clearing time corresponding to the receiving-end system based on the critical slip value.

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