Method, device and equipment for judging transient voltage stability of power system and medium

Abstract

The invention relates to the technical field of transient stability analysis and control of a power system, in particular to a method, a device and equipment for judging transient voltage stability of the power system and a medium. The method comprises the following steps: calculating Thevenin equivalent potential and critical instability potential of a power system, an induction motor critical instability slip value and a transient process induction motor maximum slip value, and if the Thevenin equivalent potential is smaller than the critical instability potential or the transient process induction motor maximum slip value is larger than the induction motor critical instability slip value, determining that the induction motor is in a non-stable state; and if yes, judging that the transient voltage of the power system is in an unstable state, otherwise, judging that the transient voltage of the power system is in a stable state when the maximum slip value of the induction motor in the transient process is smaller than or equal to the critical unstable slip value of the induction motor and the Thevenin equivalent potential is greater than or equal to the critical unstable potential. Therefore, the problem of misjudgment or missed judgment caused by lack of theoretical support of a judgment method in related technologies is solved, and accurate judgment of the transient voltage stability of the power system is realized by calculating a series of parameters of the power system.

Description

Technical Field

[0001] The present application relates to the field of transient stability analysis and control of power systems, and in particular to a method, device, equipment and medium for determining transient voltage stability of power systems. Background Art

[0002] Driven by the goal of low-carbon development, the new power system is accelerating its evolution towards a high proportion of renewable energy, a high degree of power electronics, and two-way interaction between sources and loads. Its operating characteristics have undergone profound changes. Among them, the receiving-end system, as the power load center, has weaker transient voltage stability than the sending-end system. As the penetration rate of renewable energy (such as photovoltaic and wind power) in the power system continues to increase, the traditional transient voltage stability judgment method can no longer meet the safe and stable operation requirements of the new power system. Therefore, a new transient voltage stability judgment method is needed to ensure the safe and stable operation of the receiving-end power system.

[0003] In related technologies, the method for judging the transient voltage stability of the power system is mainly based on engineering experience. That is, if the hub bus voltage is lower than 0.75pu for more than 1.0 second, the power system is judged to be transient voltage unstable.

[0004] However, the above method has obvious limitations. Since it is based on engineering experience and lacks strict mathematical and physical theoretical support, it may lead to misjudgment or missed judgment, and it cannot be applied to new scenarios where new energy is widely connected, which urgently needs to be solved. Summary of the Invention

[0005] The present application provides a method, device, equipment and medium for determining the transient voltage stability of an electric power system, so as to solve the problem that the method for determining the transient voltage stability of an electric power system in the related art is prone to misjudgment or missed judgment due to lack of theoretical support.

[0006] A first embodiment of the present application provides a method for determining transient voltage stability of a power system, comprising the following steps:

[0007] Calculating the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor of the power system during a transient process;

[0008] determining whether the Thevenin equivalent potential is less than the critical instability potential; if so, determining that the transient voltage of the power system is in an unstable state; otherwise, determining whether the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor;

[0009] If the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor, it is determined that the transient voltage of the power system is in an unstable state; otherwise, it is determined that the transient voltage of the power system is in a stable state.

[0010] According to one embodiment of the present application, after calculating the Thevenin equivalent potential of the power system, the method further includes:

[0011] Calculating the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system;

[0012] A Thevenin equivalent model of the power system is constructed based on the Thevenin equivalent potential and the equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

[0013] According to one embodiment of the present application, the calculating of the critical instability potential of the power system and the critical instability slip value of the induction motor of the power system includes:

[0014] Based on the balance principle between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor, when the electromagnetic torque is equal to the mechanical torque, calculating the critical instability slip value of the induction motor;

[0015] A critical buckling potential of the power system is calculated based on the Thevenin equivalent resistance, the Thevenin equivalent reactance, and the mechanical torque of the induction motor of the power system.

[0016] According to one embodiment of the present application, the calculating the maximum slip value of the induction motor in the transient process of the power system includes:

[0017] Calculating a first reactive power of the power system generated by the renewable energy, a voltage amplitude at a renewable energy grid connection point under different slips, and an electromagnetic torque of the induction motor;

[0018] Calculating a second reactive power of the new energy grid connection point under different slips based on the voltage amplitude of the new energy grid connection point;

[0019] It is determined whether the electromagnetic torque and the mechanical torque of the induction motor are equal. If the electromagnetic torque and the mechanical torque are equal, a maximum slip value of the induction motor in the transient process is calculated according to a preset inertia time constant of the induction motor, the electromagnetic torque, and the mechanical torque.

[0020] According to one embodiment of the present application, calculating the electromagnetic torque of the induction motor includes:

[0021] determining a stator circuit time constant of the induction motor, an initial value of the electromagnetic torque, and a terminal value of the electromagnetic torque;

[0022] A time-varying relationship of the electromagnetic torque is determined based on the stator circuit time constant, the initial value of the electromagnetic torque, and the final value of the electromagnetic torque, and the electromagnetic torque of the induction motor is obtained based on the changing relationship.

[0023] According to the method for determining the transient voltage stability of the power system of the embodiment of the present application, the Thevenin equivalent potential, critical instability potential, critical instability slip value of the induction motor, and maximum slip value of the induction motor during the transient process of the power system are calculated. If the Thevenin equivalent potential is less than the critical instability potential or the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor, the transient voltage of the power system is determined to be in an unstable state. Otherwise, when the maximum slip value of the induction motor during the transient process is less than or equal to the critical instability slip value of the induction motor and the Thevenin equivalent potential is greater than or equal to the critical instability potential, the transient voltage of the power system is determined to be in a stable state. Thus, the problem of misjudgment or omission caused by the lack of theoretical support in the determination method in the related art is solved, and the accurate determination of the transient voltage stability of the power system is achieved by calculating a series of parameters of the power system.

[0024] A second embodiment of the present application provides a device for determining transient voltage stability of a power system, comprising:

[0025] a calculation module, configured to calculate the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor of the power system during a transient process;

[0026] a judgment module, configured to judge whether the Thevenin equivalent potential is less than the critical instability potential; if so, determining that the transient voltage of the power system is in an unstable state; otherwise, judging whether the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor;

[0027] The determining module is configured to determine that the transient voltage of the power system is in an unstable state if the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor; otherwise, determine that the transient voltage of the power system is in a stable state.

[0028] After calculating the Thevenin equivalent potential of the power system, the calculation module further includes:

[0029] a first calculation unit, configured to calculate the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system;

[0030] A second calculation unit is used to construct a Thevenin equivalent model of the power system based on the Thevenin equivalent potential and the equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

[0031] According to one embodiment of the present application, the computing module includes:

[0032] a third calculation unit, configured to calculate a critical instability slip value of the induction motor based on a balance principle between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor when the electromagnetic torque is equal to the mechanical torque;

[0033] A fourth calculation unit is configured to calculate a critical buckling potential of the power system based on the Thevenin equivalent resistance, the Thevenin equivalent reactance, and the mechanical torque of the induction motor of the power system.

[0034] According to one embodiment of the present application, the computing module includes:

[0035] a fifth calculation unit, configured to calculate a first reactive power of the power system generated by the renewable energy, a voltage amplitude at a renewable energy grid connection point under different slip conditions, and an electromagnetic torque of the induction motor;

[0036] A sixth calculation unit, configured to calculate a second reactive power of the new energy grid connection point under different slips based on the voltage amplitude of the new energy grid connection point;

[0037] a seventh calculation unit, configured to determine whether the electromagnetic torque and the mechanical torque of the induction motor are equal; and if the electromagnetic torque and the mechanical torque are equal, calculating the maximum slip value of the induction motor in the transient process according to a preset inertia time constant of the induction motor, the electromagnetic torque, and the mechanical torque.

[0038] According to one embodiment of the present application, the fifth computing unit includes:

[0039] a determination subunit, configured to determine a stator circuit time constant of the induction motor, an initial value of the electromagnetic torque, and a termination value of the electromagnetic torque;

[0040] An acquisition subunit is used to determine a change relationship of the electromagnetic torque over time based on the stator circuit time constant, the initial value of the electromagnetic torque and the terminal value of the electromagnetic torque, and obtain the electromagnetic torque of the induction motor based on the change relationship.

[0041] According to the device for determining the transient voltage stability of a power system according to the embodiment of the present application, the Thevenin equivalent potential, critical instability potential, critical instability slip value of the induction motor, and maximum slip value of the induction motor during the transient process of the power system are calculated. If the Thevenin equivalent potential is less than the critical instability potential or the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor, the transient voltage of the power system is determined to be in an unstable state. Otherwise, when the maximum slip value of the induction motor during the transient process is less than or equal to the critical instability slip value of the induction motor and the Thevenin equivalent potential is greater than or equal to the critical instability potential, the transient voltage of the power system is determined to be in a stable state. Thus, the problem of misjudgment or missed judgment caused by the lack of theoretical support in the determination method in the related art is solved, and the accurate determination of the transient voltage stability of the power system is achieved by calculating a series of parameters of the power system.

[0042] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method for determining the transient voltage stability of the power system as described in the above embodiment.

[0043] A fourth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement the method for determining the transient voltage stability of a power system as described in the above embodiment.

[0044] A fifth aspect of the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the method for determining the transient voltage stability of a power system as described in the above embodiment.

[0045] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0047] Figure 1 A method for determining transient voltage stability of a power system provided in accordance with an embodiment of the present application;

[0048] Figure 2 Schematic diagram of the system structure for determining transient voltage stability according to one embodiment of the present application;

[0049] Figure 3is an overall determination flow chart of transient voltage stability according to one embodiment of the present application;

[0050] Figure 4 1 is a block diagram of an exemplary device for determining transient voltage stability of a power system according to an embodiment of the present application;

[0051] Figure 5 Schematic diagram of the structure of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0052] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0053] The following describes, with reference to the accompanying drawings, a method, apparatus, equipment, and medium for determining the transient voltage stability of an electric power system according to an embodiment of the present application. In view of the problem that the method for determining the transient voltage stability of an electric power system in the related art mentioned in the above background technology lacks theoretical support and is prone to misjudgment or missed judgment, the present application provides a method for determining the transient voltage stability of an electric power system. In this method, the Thevenin equivalent potential, critical instability potential, critical instability slip value of an induction motor, and maximum slip value of an induction motor during a transient process of the electric power system are calculated. If the Thevenin equivalent potential is less than the critical instability potential or the maximum slip value of an induction motor during a transient process is greater than the critical instability slip value of an induction motor, it is determined that the transient voltage of the electric power system is in an unstable state. Otherwise, when the maximum slip value of an induction motor during a transient process is less than or equal to the critical instability slip value of an induction motor and the Thevenin equivalent potential is greater than or equal to the critical instability potential, it is determined that the transient voltage of the electric power system is in a stable state. This solves the problem in related technologies of misjudgment or missed judgment caused by lack of theoretical support, and accurately judges the transient voltage stability of the power system by calculating a series of parameters of the power system.

[0054] Specifically, Figure 1 A flowchart of a method for determining transient voltage stability of a power system provided in an embodiment of the present application.

[0055] like Figure 1 As shown, the method for determining the transient voltage stability of the power system includes the following steps:

[0056] In step S101 , the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor of the power system during transient process are calculated.

[0057] According to one embodiment of the present application, after calculating the Thevenin equivalent potential of the power system, it also includes: calculating the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system; constructing the Thevenin equivalent model of the power system based on the Thevenin equivalent potential and the equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

[0058] According to one embodiment of the present application, calculating the critical instability potential of an electric power system and the critical instability slip value of an induction motor of the electric power system includes: calculating the critical instability slip value of the induction motor when the electromagnetic torque is equal to the mechanical torque based on the principle of balance between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor; and calculating the critical instability potential of the electric power system based on the Thevenin equivalent resistance, the Thevenin equivalent reactance and the mechanical torque of the induction motor.

[0059] Specifically, with the advancement of the global low-carbon development goals, the power system is accelerating its evolution towards a high proportion of renewable energy (such as photovoltaics, wind power, etc.), a high degree of power electronics, and two-way interaction between sources and loads. These changes have profoundly affected the operating characteristics of the power system, especially the transient voltage stability of the receiving system has become particularly fragile. Therefore, in order to solve the problem that the judgment method based on engineering experience is difficult to adapt to the needs of the current new power system, a new method is urgently needed to accurately evaluate and judge the transient voltage stability of the new power system, such as Figure 2 As shown, the embodiment of the present application calculates the Thevenin equivalent potential and equivalent impedance of the power system, the critical instability potential, the critical instability slip of the induction motor, and the maximum slip value of the induction motor in the transient process to achieve accurate judgment of the transient voltage stability of the system where new energy and induction motors coexist, thereby improving the level of new energy absorption and ensuring the safe and stable operation of the power grid.

[0060] Specifically, first, according to the circuit characteristics from the renewable energy access point to the receiving grid in the power system, the Thevenin equivalent potential of the power system with renewable energy access is calculated. and the Thevenin equivalent impedance X of the power system e , X e =X g +X s1 , Thevenin equivalent impedance includes the Thevenin equivalent resistance R eq and Thevenin equivalent reactance X eq , where the expression of Thevenin equivalent potential is:

[0061]

[0062] in, The Thevenin equivalent potential of the power system after the integration of new energy, is the impedance from the new energy access point to the grid end, is the equivalent complex impedance of the power grid, is the line complex impedance, R1 is the stator resistance of the induction motor, X1 is the stator reactance of the induction motor, X M is the induction motor excitation reactance, j is a unit imaginary number, is the equivalent potential of the power grid, is the current flowing through the line.

[0063] Furthermore, in order to simplify the calculation process and improve the calculation efficiency, Z is often ignored. g and Z s The Thevenin equivalent potential is calculated by U eq It means that its expression is:

[0064]

[0065] Among them, X s2 It is the reactance from the new energy access point to the induction motor terminal.

[0066] Thevenin equivalent resistance R eq The expression is:

[0067] R eq =Re[(jX e +jX s2 +R1+jX1) / / jX M ]; (3)

[0068] Thevenin equivalent reactance X eq The expression is:

[0069] X eq =Im[(jX e +jX s2 +R1+jX1) / / jX M ]; (4)

[0070] Secondly, a Thevenin equivalent model of the power system is constructed based on the calculated Thevenin equivalent potential and equivalent impedance. This equivalent model helps to better understand the electrical distance between the renewable energy access point and the receiving power grid and the degree of their interaction, thereby evaluating the response of the power system to disturbances.

[0071] Furthermore, since the equivalent potential and equivalent impedance are the key factors for calculating the critical instability potential U of the power system, lim and the critical instability slip S of the induction motor lim Therefore, the subsequent critical instability potential, critical instability slip value of the induction motor and maximum slip value of the induction motor in the transient process can be calculated based on the Thevenin equivalent model.

[0072] Specifically, first, based on the balance principle between the electromagnetic torque and the mechanical torque of the induction motor, when the electromagnetic torque and the mechanical torque are equal, the critical instability slip value S of the induction motor is calculated. lim , critical instability slip value S of induction motor lim It refers to the critical point where the motor transitions from a stable operating state to an unstable state. Its expression is:

[0073]

[0074] Among them, T m is the mechanical torque of the induction motor, which is a constant value, X2 is the value of the induction motor rotor reactance referred to the stator side, and R2 is the value of the induction motor rotor resistance referred to the stator side.

[0075] Then, the critical instability potential U of the power system is calculated based on the Thevenin equivalent resistance, Thevenin equivalent reactance and mechanical torque of the induction motor. lim , that is, the minimum voltage level at which the system can maintain stability. In other words, when the actual voltage of the power system drops below this critical value, the power system will not be able to maintain voltage stability and will enter an unstable state. Its expression is:

[0076]

[0077] According to one embodiment of the present application, calculating the maximum slip value of an induction motor in a transient process of an electric power system includes: calculating a first reactive power of the electric power system generated by a renewable energy source, a voltage amplitude of a renewable energy grid connection point under different slips, and an electromagnetic torque of an induction motor; calculating a second reactive power of the renewable energy grid connection point under different slips based on the voltage amplitude of the renewable energy grid connection point; judging whether the electromagnetic torque of the induction motor is equal to the mechanical torque; if the electromagnetic torque is equal to the mechanical torque, calculating the maximum slip value of the induction motor in a transient process according to a preset inertia time constant, the electromagnetic torque, and the mechanical torque of the induction motor.

[0078] According to one embodiment of the present application, calculating the electromagnetic torque of an induction motor includes: determining a stator circuit time constant, an initial value of the electromagnetic torque, and a terminal value of the electromagnetic torque of the induction motor; determining a change relationship of the electromagnetic torque over time based on the stator circuit time constant, the initial value of the electromagnetic torque, and the terminal value of the electromagnetic torque, and obtaining the electromagnetic torque of the induction motor based on the change relationship.

[0079] Specifically, after the grid voltage drops, the renewable energy source will enter low voltage ride-through. At this time, the renewable energy station will provide reactive power support to the grid in accordance with national standards. In other words, at this time, the reactive power support capability provided by the renewable energy source during the low voltage ride-through period is combined to simulate the situation when the grid voltage drops, and based on this, the maximum slip S that may occur in the transient process of the induction motor is calculated. max , that is, the maximum slip value S of the induction motor in the transient process max , where the output active and reactive current reference values ​​are,

[0080]

[0081] Among them, I max is the converter output current; I dref is the active current, I qref is the reactive current; k LVRT is the reactive voltage coefficient; U LVRT is the low wear action threshold; U PCC is the voltage amplitude at the grid connection point.

[0082] The first reactive power of the power system generated by renewable energy is:

[0083] Q=U PCC I t k LVRT (U LVRT -U PCC ); (8)

[0084] Among them, I t is the total output current of new energy.

[0085] At this time, the voltage of the new energy grid connection point is:

[0086]

[0087] in,

[0088]

[0089] Where s is the slip of the induction motor, Z w is the impedance modulus of the induction motor side viewed from the new energy port, and α is the impedance angle.

[0090] At this time, the voltage amplitude of the new energy grid connection point under different slip is:

[0091]

[0092] in, is the complex impedance from the new energy access point to the potential in the grid, Z w is the impedance modulus of the induction motor side viewed from the new energy port, is the complex impedance of the induction motor side viewed from the new energy port.

[0093] Set impedance

[0094] but

[0095] Among them, Z d is the impedance modulus from the potential inside the grid, β is the impedance angle from the potential inside the grid, and F is a complex number The modulus of θ is a complex number Angle, plural angle.

[0096] At this time, the voltage amplitude of the new energy grid connection point is:

[0097] Then the second reactive power of the new energy grid connection point is obtained as:

[0098]

[0099] Combining equation (8) and equation (16), we can get

[0100] In this way, the current phase and grid connection point voltage value corresponding to different slips can be calculated, and then the electromagnetic torque can be calculated.

[0101] Furthermore, the stator circuit time constant τ and the initial value T of the electromagnetic torque of the induction motor are determined. e0 and the terminal value T of the electromagnetic torque e1 , and based on the stator circuit time constant τ, the initial value of the electromagnetic torque T e0 and the terminal value T of the electromagnetic torque e1 The relationship between the change of electromagnetic torque and time is determined, and the electromagnetic torque of the induction motor is obtained based on the change relationship, wherein the stator circuit time constant τ can be expressed as:

[0102]

[0103] The relationship between the change of electromagnetic torque and time in the transient process is:

[0104]

[0105] Furthermore, it is determined whether the electromagnetic torque of the induction motor is equal to the mechanical torque. If the electromagnetic torque T e and mechanical torque T m Equal, this means that the slip of the induction motor reaches the maximum, then according to the preset inertia time constant T of the induction motor J , electromagnetic torque Te and mechanical torque T m The maximum slip value S of the induction motor in the transient process is calculated by the following integration max , whose expression is:

[0106]

[0107] In step S102, it is determined whether the Thevenin equivalent potential is less than the critical instability potential. If the Thevenin equivalent potential is less than the critical instability potential, it is determined that the transient voltage of the power system is in an unstable state. Otherwise, it is determined whether the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor.

[0108] Specifically, if Figure 3 As shown, based on the relevant parameters involved in the method for judging the transient voltage stability of the power system obtained by the above calculation, first, the Thevenin equivalent potential U eq Is it less than the critical instability potential U lim , if the Thevenin equivalent potential is less than the critical instability potential, that is, U eq <U lim , this indicates that the current voltage level of the power system has fallen below the minimum voltage threshold required to maintain voltage stability. In this case, the power system is likely unable to recover to a stable state. Therefore, the power system transient voltage is determined to be in an unstable state. For example, assuming that after a power system fails, the calculated Thevenin equivalent potential is 0.65pu, while the critical instability potential is 0.75pu. Since 0.65pu<0.75pu, this indicates that the current voltage level of the power system is insufficient to maintain voltage stability. Therefore, the system is determined to be in a transient voltage instability state.

[0109] Furthermore, if the Thevenin equivalent potential U eq Greater than or equal to the critical instability potential U lim , that is U eq ≥U lim , this means that the voltage level of the power system is not lower than the minimum threshold required to maintain voltage stability, that is, the power system has sufficient voltage support capacity under the current conditions and can maintain voltage stability. At this time, in order to further evaluate the voltage stability of the power system in the transient process, especially whether the induction motor will lose synchronization due to the voltage drop, it is necessary to further determine the maximum slip value S of the induction motor in the transient process. max Is it greater than the critical instability slip value S of the induction motor? lim , according to the maximum slip value S of the induction motor in the transient process max and the critical instability slip value S of the induction motor limThe relationship between the size of the induction motor and the slip of the induction motor can be used to determine whether the slip exceeds the limit value at which it can maintain stability, so that possible instability risks can be identified in advance and corresponding measures can be taken (such as enhancing reactive power support, adjusting load distribution, etc.) to improve the overall stability of the system.

[0110] In step S103 , if the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor, it is determined that the transient voltage of the power system is in an unstable state; otherwise, it is determined that the transient voltage of the power system is in a stable state.

[0111] Specifically, if the maximum slip value S of the induction motor in the transient process is max Greater than the critical instability slip value S of the induction motor lim , that is, s max >s lim , which means that during the transient process, the slip of the induction motor exceeds the limit value at which it can maintain stability. In this case, the induction motor will lose synchronization, causing the voltage to drop further, which may cause voltage collapse or other serious stability problems. Therefore, at this time, the power system is in a transient voltage instability state; if the maximum slip value of the induction motor in the transient process S max Less than or equal to the critical instability slip value S of the induction motor lim , that is, s max ≤s lim , which means that under severe transient conditions, the slip of the induction motor does not exceed its critical instability slip value. In this case, the induction motor can return to normal operation and the power system can maintain voltage stability. Therefore, the power system is in a transient voltage stability state. The expression of the transient voltage stability of the power system can be expressed as:

[0112]

[0113] Among them, Flag is the transient voltage discrimination output signal, Flag = 1 indicates that the transient voltage is unstable; Flag = 0 indicates that the transient voltage is stable.

[0114] That is to say, when the Thevenin equivalent potential is less than the critical instability potential, or the maximum slip value S of the induction motor in the transient process max Greater than the critical instability slip value S of the induction motor lim , that is U eq lim or s max >s lim When the transient voltage of the power system is in an unstable state; when the Thevenin equivalent potential is greater than or equal to the critical instability potential and the maximum slip value of the induction motor during the transient process is S max Less than or equal to the critical instability slip value S of the induction motor lim , that is U​eq ≥U lim And s max ≤s lim When , the transient voltage of the power system is in a stable state.

[0115] In summary, based on the specific discussion of the above embodiments, this application can achieve the following beneficial effects:

[0116] (1) Improving the accuracy of transient voltage stability judgment. This application provides a more scientific and accurate evaluation method by calculating the system's Thevenin equivalent potential, critical instability potential, and critical instability slip value of the induction motor. At the same time, it can better reflect the impact of new energy on the dynamic behavior of the power system, thereby improving the accuracy of judgment in new application scenarios.

[0117] (2) Enhance the safety and stability of the system. By accurately judging whether the power system is in a transient voltage instability state, timely measures can be taken to avoid voltage collapse events and ensure the safe operation of the power grid. At the same time, the reactive power support provided by new energy equipment during low voltage ride-through is also taken into account, which helps to maintain the voltage level at the grid connection point and further enhance the stability of the system.

[0118] (3) Improve the level of new energy absorption. Based on the analysis of the maximum slip value and critical instability slip value of the induction motor in the transient process, the control strategy of the new energy equipment can be optimized to enable it to provide reactive power support more effectively during the low voltage ride-through period, thereby improving the absorption capacity of new energy.

[0119] (4) Supporting the development of smart grids, this application can be integrated into the monitoring system of smart grids to achieve real-time monitoring and early warning of transient voltage stability of power systems, helping dispatchers to promptly identify potential problems and take corresponding measures.

[0120] According to the method for determining the transient voltage stability of the power system of the embodiment of the present application, the Thevenin equivalent potential, critical instability potential, critical instability slip value of the induction motor, and maximum slip value of the induction motor during the transient process of the power system are calculated. If the Thevenin equivalent potential is less than the critical instability potential or the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor, the transient voltage of the power system is determined to be in an unstable state. Otherwise, when the maximum slip value of the induction motor during the transient process is less than or equal to the critical instability slip value of the induction motor and the Thevenin equivalent potential is greater than or equal to the critical instability potential, the transient voltage of the power system is determined to be in a stable state. Thus, the problem of misjudgment or omission caused by the lack of theoretical support in the determination method in the related art is solved, and the accurate determination of the transient voltage stability of the power system is achieved by calculating a series of parameters of the power system.

[0121] Next, a device for determining transient voltage stability of a power system according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0122] Figure 4 It is a block diagram of a device for determining transient voltage stability of a power system according to an embodiment of the present application.

[0123] like Figure 4 As shown, the judging device 10 based on transient voltage stability of a power system includes: a calculation module 100 , a judging module 200 and a judging module 300 .

[0124] The calculation module 100 is used to calculate the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor in the transient process of the power system;

[0125] The judgment module 200 is used to judge whether the Thevenin equivalent potential is less than the critical instability potential. If the Thevenin equivalent potential is less than the critical instability potential, it is determined that the transient voltage of the power system is in an unstable state. Otherwise, it is determined whether the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor;

[0126] The determination module 300 is configured to determine that the transient voltage of the power system is in an unstable state if the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor; otherwise, determine that the transient voltage of the power system is in a stable state.

[0127] After calculating the Thevenin equivalent potential of the power system, the calculation module 100 further includes:

[0128] a first calculation unit, configured to calculate the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system;

[0129] The second calculation unit is used to construct a Thevenin equivalent model of the power system based on the Thevenin equivalent potential and equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

[0130] According to one embodiment of the present application, the computing module 100 includes:

[0131] a third calculation unit, configured to calculate a critical instability slip value of the induction motor when the electromagnetic torque is equal to the mechanical torque based on a balance principle between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor;

[0132] The fourth calculation unit is used to calculate the critical instability potential of the power system based on the Thevenin equivalent resistance, the Thevenin equivalent reactance and the mechanical torque of the induction motor of the power system.

[0133] According to one embodiment of the present application, the computing module 100 includes:

[0134] a fifth calculation unit, configured to calculate a first reactive power of the power system generated by the renewable energy, a voltage amplitude at a renewable energy grid connection point under different slips, and an electromagnetic torque of the induction motor;

[0135] A sixth calculation unit, configured to calculate a second reactive power of the new energy grid connection point under different slips based on the voltage amplitude of the new energy grid connection point;

[0136] a seventh calculation unit, configured to determine whether the electromagnetic torque and the mechanical torque of the induction motor are equal; and if the electromagnetic torque and the mechanical torque are equal, calculating a maximum slip value of the induction motor in a transient process according to a preset inertia time constant, the electromagnetic torque, and the mechanical torque of the induction motor.

[0137] According to one embodiment of the present application, the fifth computing unit includes:

[0138] a determination subunit, for determining a stator circuit time constant of the induction motor, an initial value of the electromagnetic torque, and a terminal value of the electromagnetic torque;

[0139] The acquisition subunit is used to determine the change relationship of the electromagnetic torque over time based on the stator circuit time constant, the initial value of the electromagnetic torque and the terminal value of the electromagnetic torque, and obtain the electromagnetic torque of the induction motor based on the change relationship.

[0140] According to the device for determining the transient voltage stability of a power system according to the embodiment of the present application, the Thevenin equivalent potential, critical instability potential, critical instability slip value of the induction motor, and maximum slip value of the induction motor during the transient process of the power system are calculated. If the Thevenin equivalent potential is less than the critical instability potential or the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor, the transient voltage of the power system is determined to be in an unstable state. Otherwise, when the maximum slip value of the induction motor during the transient process is less than or equal to the critical instability slip value of the induction motor and the Thevenin equivalent potential is greater than or equal to the critical instability potential, the transient voltage of the power system is determined to be in a stable state. Thus, the problem of misjudgment or missed judgment caused by the lack of theoretical support in the determination method in the related art is solved, and the accurate determination of the transient voltage stability of the power system is achieved by calculating a series of parameters of the power system.

[0141] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0142] Memory 501 , processor 502 , and computer programs stored in the memory 501 and executable on the processor 502 .

[0143] When the processor 502 executes the program, the method for determining the transient voltage stability of the power system provided in the above embodiment is implemented.

[0144] Furthermore, the electronic device further includes:

[0145] The communication interface 503 is used for communication between the memory 501 and the processor 502 .

[0146] The memory 501 is used to store computer programs that can be run on the processor 502 .

[0147] The memory 501 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0148] If the memory 501, processor 502, and communication interface 503 are implemented independently, the communication interface 503, memory 501, and processor 502 can be interconnected via a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 5 Only one thick line is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0149] Optionally, in a specific implementation, if the memory 501, the processor 502 and the communication interface 503 are integrated on a chip, the memory 501, the processor 502 and the communication interface 503 can communicate with each other through an internal interface.

[0150] The processor 502 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0151] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above method for determining transient voltage stability of a power system.

[0152] An embodiment of the present application further provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the method for determining transient voltage stability of a power system as described in the above embodiment.

[0153] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0154] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0155] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for determining transient voltage stability of a power system, characterized in that: The following steps are involved: Calculating the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor of the power system during a transient process; determining whether the Thevenin equivalent potential is less than the critical instability potential; if so, determining that the transient voltage of the power system is in an unstable state; otherwise, determining whether the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor; If the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor, it is determined that the transient voltage of the power system is in an unstable state; otherwise, it is determined that the transient voltage of the power system is in a stable state.

2. The method according to claim 1, characterized in that After calculating the Thevenin equivalent potential of the power system, it also includes: Calculating the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system; A Thevenin equivalent model of the power system is constructed based on the Thevenin equivalent potential and the equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

3. The method according to claim 1, characterized in that Calculating the critical instability potential of the power system and the critical instability slip value of the induction motor of the power system includes: Based on the balance principle between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor, when the electromagnetic torque is equal to the mechanical torque, calculating the critical instability slip value of the induction motor; A critical buckling potential of the power system is calculated based on the Thevenin equivalent resistance, the Thevenin equivalent reactance, and the mechanical torque of the induction motor of the power system.

4. The method according to claim 1, wherein The calculating of the maximum slip value of the induction motor in the transient process of the power system includes: Calculating a first reactive power of the power system generated by the renewable energy, a voltage amplitude at a renewable energy grid connection point under different slips, and an electromagnetic torque of the induction motor; Calculating a second reactive power of the new energy grid connection point under different slips based on the voltage amplitude of the new energy grid connection point; It is determined whether the electromagnetic torque and the mechanical torque of the induction motor are equal. If the electromagnetic torque and the mechanical torque are equal, a maximum slip value of the induction motor in the transient process is calculated according to a preset inertia time constant of the induction motor, the electromagnetic torque, and the mechanical torque.

5. The method according to claim 4, characterized in that The calculating of the electromagnetic torque of the induction motor comprises: determining a stator circuit time constant of the induction motor, an initial value of the electromagnetic torque, and a terminal value of the electromagnetic torque; A time-varying relationship of the electromagnetic torque is determined based on the stator circuit time constant, the initial value of the electromagnetic torque, and the final value of the electromagnetic torque, and the electromagnetic torque of the induction motor is obtained based on the changing relationship.

6. A device for determining transient voltage stability of a power system, characterized in that: include: a calculation module, configured to calculate the Thevenin equivalent potential of the power system, the critical instability potential of the power system, the critical instability slip value of the induction motor of the power system, and the maximum slip value of the induction motor of the power system during a transient process; a judgment module, configured to judge whether the Thevenin equivalent potential is less than the critical instability potential; if so, determining that the transient voltage of the power system is in an unstable state; otherwise, judging whether the maximum slip value of the induction motor during the transient process is greater than the critical instability slip value of the induction motor; The determining module is configured to determine that the transient voltage of the power system is in an unstable state if the maximum slip value of the induction motor in the transient process is greater than the critical instability slip value of the induction motor; otherwise, determine that the transient voltage of the power system is in a stable state.

7. The device according to claim 6, characterized in that After calculating the Thevenin equivalent potential of the power system, the calculation module further includes: a first calculation unit, configured to calculate the Thevenin equivalent impedance of the power system, wherein the equivalent impedance includes the Thevenin equivalent resistance and the Thevenin equivalent reactance of the power system; A second calculation unit is used to construct a Thevenin equivalent model of the power system based on the Thevenin equivalent potential and the equivalent impedance, so as to calculate the critical instability potential, the critical instability slip value of the induction motor and the maximum slip value of the induction motor in the transient process based on the Thevenin equivalent model.

8. The device according to claim 6, characterized in that The computing module includes: a third calculation unit, configured to calculate a critical instability slip value of the induction motor based on a balance principle between the electromagnetic torque of the induction motor and the mechanical torque of the induction motor when the electromagnetic torque is equal to the mechanical torque; A fourth calculation unit is configured to calculate a critical buckling potential of the power system based on the Thevenin equivalent resistance, the Thevenin equivalent reactance, and the mechanical torque of the induction motor of the power system.

9. The device according to claim 6, characterized in that The computing module includes: a fifth calculation unit, configured to calculate a first reactive power of the power system generated by the renewable energy, a voltage amplitude at a renewable energy grid connection point under different slip conditions, and an electromagnetic torque of the induction motor; A sixth calculation unit, configured to calculate a second reactive power of the new energy grid connection point under different slips based on the voltage amplitude of the new energy grid connection point; a seventh calculation unit, configured to determine whether the electromagnetic torque and the mechanical torque of the induction motor are equal; and if the electromagnetic torque and the mechanical torque are equal, calculating the maximum slip value of the induction motor in the transient process according to a preset inertia time constant of the induction motor, the electromagnetic torque, and the mechanical torque.

10. The device according to claim 9, characterized in that The fifth computing unit includes: a determination subunit, configured to determine a stator circuit time constant of the induction motor, an initial value of the electromagnetic torque, and a termination value of the electromagnetic torque; An acquisition subunit is used to determine a change relationship of the electromagnetic torque over time based on the stator circuit time constant, the initial value of the electromagnetic torque and the terminal value of the electromagnetic torque, and obtain the electromagnetic torque of the induction motor based on the change relationship.

11. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method for determining transient voltage stability of a power system according to any one of claims 1 to 5.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the method for determining transient voltage stability of a power system as claimed in any one of claims 1 to 5.

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