A new energy station oscillation accurate tracing and emergency control method and storage medium

Abstract

The application discloses a new energy station oscillation accurate tracing and emergency control method and a storage medium, and comprises the following steps: obtaining impedance data of a new energy station and a large power grid under different working conditions through frequency sweeping; an emergency control structure of the new energy station oscillation and a control parameter selection method are proposed; according to real-time monitoring results of power flow of each node in the new energy grid-connected system, the working condition of the new energy equipment and the large power grid is judged online, impedance under the corresponding working condition is extracted for oscillation mode discrimination, key mode information under the current working condition is obtained, and the position of the best controllable and observable node under the current working condition is obtained; when the oscillation mode discrimination result is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the best controllable and observable node. The new energy station oscillation accurate tracing and emergency control method and system provided by the application can respond to the resonance risk of the new energy grid-connected system online, damp the oscillation risk mode, and significantly improve the operation stability of the new energy station.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to a method and storage medium for precise tracing and emergency control of oscillations in new energy power plants. Background Technology

[0002] The large-scale integration of new energy equipment into the power grid has resulted in significant multimodal and weakly damped characteristics of the new power system. The diversification of modes has exacerbated the risk of multi-frequency oscillations in the new power system. Due to the reverse distribution of the geographical locations of new energy bases and load centers in my country, large-scale transmission of new energy via high-voltage AC / DC has become the norm, which has increased the complexity of the power grid structure. The short-circuit ratio of the power grid varies greatly under various complex operating conditions. In addition, the external characteristics change due to random fluctuations in the output of new energy, making the stability of the new energy grid-connected system increasingly critical. Assessing the potential multi-frequency oscillation risk of the power system under different operating conditions is crucial to ensuring the safe and stable operation of the new power system.

[0003] The increasing penetration of new energy sources in emerging power systems highlights the weak damping characteristics of these systems. The negative resistance and capacitive effects of power electronic devices further reduce the modal damping ratio. With a large number of power electronic devices integrated into the power grid, the number of oscillation modes increases, making modal analysis more difficult and raising the oscillation risk of new energy power systems. Oscillation problems have become a significant factor jeopardizing the stable operation of new energy power plants.

[0004] Furthermore, due to the rapid propagation speed of oscillations, oscillation control strategies must be formulated in a short period of time to avoid expanding the scope of impact. This is relatively difficult in actual operation. There are relatively few existing research schemes for precise oscillation source tracing and emergency control, and they are mainly offline source tracing schemes. There are few studies on oscillation source tracing and emergency control measures based on real-time monitoring data. In summary, existing research schemes cannot meet the emergency control requirements of oscillations in new energy power plants and cannot guarantee the stable operation of new energy power systems.

[0005] Therefore, it is necessary to study a method and storage medium for precise source tracing and emergency control of oscillations in new energy power plants, design a precise source tracing method and an emergency control strategy for oscillations, and provide a feasible solution for precise source tracing and emergency control of oscillations in new energy power plants. Summary of the Invention

[0006] In order to solve the problems in the prior art, the present invention provides a method and system for precise source tracing and emergency control of oscillations in new energy power stations. The purpose is to accurately trace the source of oscillations in new energy power stations, suppress the propagation of oscillations in new energy power stations, improve the oscillation mode damping ratio, and ensure the safe and stable operation of new energy power stations.

[0007] To achieve the above-mentioned objectives, this invention provides a method and system for precise source tracing and emergency control of oscillations in new energy power plants, comprising a method for precise source tracing and emergency control of oscillations in new energy power plants, characterized by the following steps:

[0008] Step 1: Frequency sweep to obtain and store the impedance data of each power electronic device in the new energy power station under different operating conditions in the new energy grid-connected system; frequency sweep to obtain and store the impedance data of the large power grid under different operating conditions.

[0009] Step 2: Design the control structure of the emergency controller for new energy oscillation, define key modal stability indices, and find the optimal parameters of the emergency controller based on maximizing the modal stability indices. Then, tune the emergency controller for new energy oscillation using the optimal parameters.

[0010] Step 3: Based on the real-time power flow monitoring results of each node in the new energy grid-connected system, determine the operating conditions of the new energy equipment and the main power grid online, and extract the impedance of the main power grid and each new energy equipment under the corresponding operating conditions from the impedance data obtained by frequency sweep.

[0011] Step 4: Combine the extracted impedance under the current operating condition to determine the oscillation mode, obtain the key mode information under the current operating condition, and obtain the optimal controllable and observable node position under the current operating condition;

[0012] Step 5: Based on the oscillation mode discrimination results, if it is determined that there is no oscillation risk under the current operating conditions, continue to monitor the power flow of each node in the new energy grid-connected system in real time;

[0013] Step Six: Based on the oscillation mode discrimination results, if it is determined that there is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the optimal controllable and observable node;

[0014] Step 7: Increase the damping of the critical mode and suppress oscillations according to the additional emergency controller.

[0015] Furthermore, the grid connection point is selected as the harmonic signal injection point, the harmonic voltage source is selected as the signal source, and the harmonic injection amplitude is set according to the magnitude of the real-time injected harmonic voltage response voltage. The harmonic signal amplitude is selected as 10% of the response harmonic voltage amplitude.

[0016] Furthermore, the oscillation emergency control structure includes a proportional element, a bandpass filter element, a phase correction element, and a limiting element. These four elements are cascaded together to form an oscillation emergency controller. The controller input signal is the dq-axis component of AC voltage, and the controller additional position is the input terminal of the current inner loop control.

[0017] The transfer function expression for the controller is:

[0018]

[0019]

[0020]

[0021] Among them G F (s) is the transfer function of the bandpass filter stage, which consists of a cascaded first-order low-pass filter stage and a first-order high-pass filter stage. z is the damping ratio of the bandpass filter, ω0 is the cutoff frequency of the bandpass filter, and s is the Laplace operator. Where G... PC G(s) is the transfer function of the phase correction stage, which includes two cascaded phase correction controllers. T1 is the upper cutoff time constant of the phase correction controller, T2 is the lower cutoff time constant of the phase correction controller, and s is the Laplace operator. G(s) is the transfer function of the oscillation emergency control structure, and K... G The proportional coefficient of the proportional element.

[0022] Furthermore, the cutoff frequency ω0 in the bandpass filter stage, the upper cutoff time constant T1 in the phase correction stage, and the lower cutoff time constant T2 are set to satisfy the following relationship:

[0023]

[0024]

[0025] Where ω b The bandwidth angular frequency characterizes the correction range of the phase correction stage. The bandwidth angular frequency ω is selected as the bandwidth angular frequency. b And the proportional coefficient K of the proportional element G As a control variable, the objective function Q is defined as the negative of the real part of the eigenvalues ​​corresponding to the key modes. The objective function Q is:

[0026] Q = -Re(λ) critical )

[0027] Where λ critical The key eigenvalue is the eigenvalue with the largest real part among all eigenvalues, also known as the key oscillation mode. Re() is the algorithm for finding the real part.

[0028] Traversing when ω b and K G When the value of Q changes, the real part of the key modal eigenvalue is in the left half-plane and furthest from the imaginary axis when Q reaches its maximum value. The control parameters at this point are the optimal control parameters for the selected emergency control.

[0029] Furthermore, based on the online monitoring device to determine the current operating conditions of the power grid and new energy equipment, and based on the stored impedance data of the power grid under different operating conditions obtained by frequency sweeping, as well as the stored impedance data of each new energy equipment in the new energy power station under different operating conditions obtained by frequency sweeping, the impedance data of the power grid and new energy power station under the current operating conditions are extracted.

[0030] Furthermore, based on the extracted impedance data of each unit of the new energy grid-connected system under the current operating conditions, a node admittance matrix of the new energy grid-connected system is established based on the impedance data. The oscillation mode is calculated based on the node admittance matrix. The key oscillation mode is determined based on the frequency domain characteristics of the oscillation mode. The presence of oscillation risk is determined based on the position of the real part of the key mode in the complex plane. If the real part of the key mode is in the left half-plane, there is an oscillation risk. If the real part of the key mode is in the right half-plane, there is no oscillation risk.

[0031] Furthermore, the key modes under the current operating conditions are obtained through the modal analysis method, the left and right eigenvectors of the key modes are calculated, and the participation factors of the key modes at each node are calculated based on the left and right eigenvectors. The node with the largest participation factor is the best controllable and observable node.

[0032] The node admittance matrix contains information about the system's oscillation modes. The relationship between node voltage and node current in a power system is as follows:

[0033] I = YU

[0034]

[0035] Where n is the number of nodes in the power system, and also the order of the node admittance matrix, U is the node voltage, and I is the node injected current. The node admittance matrix in the above equation is then diagonalized:

[0036]

[0037] In the above formula, L is the left eigenvector matrix, whose row vectors are the left eigenvectors of the node admittance matrix Y; Λ is the eigenma matrix, whose diagonal elements are the eigenvalues ​​of the node admittance matrix Y; and V is the right eigenvector matrix, whose column vectors are the right eigenvectors of the node admittance matrix Y. The diagonal elements of the eigenma matrix Λ represent the modal information of each node. When the values ​​of the diagonal elements of Λ are close to 0, the corresponding mode is the key oscillation mode.

[0038] Furthermore, the step of obtaining the optimal controllable and observable node of the oscillation key mode in step four is as follows: obtain the key mode under the current operating condition through the modal analysis method, calculate the left and right eigenvectors of the key mode, calculate the participation factor of the key mode at each node based on the left and right eigenvectors, and the node with the largest participation factor is the optimal controllable and observable node.

[0039] Specifically, for the i-th oscillation mode, its participation factor is calculated as follows:

[0040]

[0041] Where L is the left eigenvector matrix, whose row vectors are the left eigenvectors of the node admittance matrix Y, and V is the right eigenvector matrix, whose column vectors are the right eigenvectors of the node admittance matrix Y. PF i is the participation factor corresponding to the i-th oscillation mode.

[0042] Furthermore, the basis for determining whether there is an oscillation risk in steps five and six is ​​as follows: The presence of an oscillation risk is determined based on the position of the real part of the critical mode in the complex plane. If the real part of the critical mode is in the left half-plane, there is an oscillation risk; if the real part of the critical mode is in the right half-plane, there is no oscillation risk. Based on the oscillation mode discrimination result, if it is determined that there is no oscillation risk under the current operating condition, real-time monitoring of the power flow at each node in the new energy grid-connected system continues; if it is determined that there is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the best controllable and observable node.

[0043] Furthermore, the invention includes a storage medium, characterized in that it includes a stored program, which, when executed, controls the device containing the storage medium to perform the above-described method for precise tracing and emergency control of oscillations in new energy power stations.

[0044] Based on the oscillation mode discrimination results, if it is determined that there is no oscillation risk under the current operating conditions, the power flow of each node in the new energy grid-connected system will continue to be monitored in real time; if it is determined that there is an oscillation risk based on the oscillation mode discrimination results, an emergency controller will be added to the control loop of the new energy equipment at the best controllable and observable node.

[0045] The beneficial effects of this invention are: This invention enables precise source tracing and emergency control of oscillations in new energy power plants, helps industry personnel obtain modal information of new energy grid-connected systems in real time, and can quickly control oscillations at the lowest cost when there is an oscillation risk, suppress the propagation of oscillations in new energy power plants, improve the oscillation mode damping ratio, and ensure the safe and stable operation of new energy power plants. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0047] Figure 1 This is a flowchart of the method for precise source tracing and emergency control of oscillations in new energy power stations according to the present invention;

[0048] Figure 2This is a flowchart of the new energy power station oscillation precise source tracing and emergency control system of the present invention;

[0049] Figure 3 This is a topology diagram of a new energy grid-connected system in an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the controller structure of the emergency controller attached to the inverter control loop of the new energy equipment in an embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the feasible domain of control parameters for the emergency controller in an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram illustrating the changes in system oscillation modes before and after applying emergency control in an embodiment of the present invention;

[0053] Figure 7 This is a comparison diagram of the impedance characteristics of the power grid and the new energy power station before and after the application of emergency control, according to an embodiment of the present invention.

[0054] Figure 8 This is a Nyquist plot showing the ratio of grid impedance to new energy power station impedance before and after applying emergency control in an embodiment of the present invention.

[0055] Figure 9 The present invention provides time-domain simulation results of the three-phase current and active power at the grid connection point before and after the application of emergency control, according to an embodiment of the present invention. Detailed Implementation

[0056] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0057] See Figure 1 and Figure 2 This invention provides a method and system for precise source tracing and emergency control of oscillations in new energy power plants, comprising the following steps:

[0058] based on Figure 3 The renewable energy grid-connected system shown acquires and stores impedance data of each renewable energy device in the renewable energy power station under different operating conditions through frequency sweeping, and acquires and stores impedance data of the main power grid under different operating conditions through frequency sweeping; specifically:

[0059] The method for frequency sweeping of new energy equipment and large power grid is as follows: select the grid connection point of new energy power system as the harmonic injection point of large power grid frequency sweeping, drill the grid connection point of new energy equipment as the harmonic injection point of each equipment of new energy power station frequency sweeping, select the harmonic voltage source as the signal source, set the harmonic injection amplitude according to the response voltage of real-time injected harmonic voltage, and keep the harmonic signal amplitude at 10% of the response harmonic voltage amplitude at all times.

[0060] Specifically, the amplitude of the response harmonic voltage is obtained through Fourier transform. Assuming the current injected harmonic frequency is f, the component with frequency f after Fourier transform is extracted, and the amplitude of this component is the amplitude of the response harmonic voltage. The frequency sweeping step in this method monitors the real-time response of the injected harmonics to ensure that the injected harmonic signal always causes 10% voltage distortion, effectively reducing the frequency sweeping error.

[0061] Based on the aforementioned renewable energy grid-connected system, a renewable energy power station oscillation emergency control structure and control parameter selection method are proposed; specifically:

[0062] The oscillation emergency control structure includes a proportional element, a bandpass filter element, a phase correction element, and a limiting element. These four elements are cascaded together to form an oscillation emergency controller. The controller input signal is the dq-axis component of AC voltage, and the controller additional position is the input terminal of the current inner loop control.

[0063] The bandpass filter stage consists of a cascaded first-order low-pass filter stage and a first-order high-pass filter stage, with a transfer function G. F The expression for (s) is:

[0064]

[0065] Where z is the damping ratio of the bandpass filter, ω0 is the cutoff frequency of the bandpass filter, and s is the Laplace operator.

[0066] The phase correction stage includes two cascaded phase correction controllers with transfer function G. PC The expression for (s) is:

[0067]

[0068] Where T1 is the upper limit cutoff time constant of the phase correction controller, and T2 is the lower limit cutoff time constant of the phase correction controller.

[0069] The transfer function G(s) of the oscillating emergency control structure is:

[0070]

[0071] Where K G The proportional coefficient of the proportional element.

[0072] In this embodiment, the emergency controller is attached to the controller structure diagram in the inverter control loop of the new energy equipment, as shown in the figure below. Figure 4 As shown;

[0073] Furthermore, the steps for establishing a method for selecting control parameters for emergency control are as follows:

[0074] The cutoff frequency ω0 in the bandpass filter stage, the upper cutoff time constant T1 in the phase correction stage, and the lower cutoff time constant T2 are supposed to satisfy the following relationship:

[0075]

[0076]

[0077] Where ω b The bandwidth angular frequency characterizes the correction range of the phase correction stage. The bandwidth angular frequency ω is selected as the bandwidth angular frequency. b And the proportional coefficient K of the proportional element G As a control variable, the objective function Q is defined as the negative of the real part of the eigenvalues ​​corresponding to the key modes. The objective function Q is:

[0078] Q = -Re(λ) critical )

[0079] Where λ critical The key eigenvalue is the eigenvalue with the largest real part among all eigenvalues, also known as the key oscillation mode. Re() is the algorithm for finding the real part.

[0080] Traversing when ω b and K G When the value of Q changes, the real part of the key modal eigenvalue is in the left half-plane and furthest from the imaginary axis when Q reaches its maximum value. The control parameters at this point are the optimal control parameters for the selected emergency control.

[0081] The feasible region diagram of the control parameters of the emergency controller in this embodiment is shown below. Figure 5 As shown, the x-axis represents the parameter, the y-axis represents the parameter, and the z-axis represents the objective function Q. When the objective function Q reaches its maximum value, the emergency controller under this combination of control parameters has the best control effect.

[0082] Based on the real-time power flow monitoring results of each node in the renewable energy grid-connected system, the operating conditions of the renewable energy equipment and the main power grid are determined online. The impedances of the main power grid and renewable energy equipment under the corresponding operating conditions are extracted from the impedance data obtained by frequency sweeping. Specifically:

[0083] Based on the online monitoring device, the current operating conditions of the power grid and new energy equipment are determined. Based on the stored impedance data of the power grid under different operating conditions obtained by frequency sweeping, and the stored impedance data of each new energy equipment in the new energy power station under different operating conditions obtained by frequency sweeping, the impedance data of the power grid and new energy power station under the current operating conditions are extracted.

[0084] Based on the extracted impedance under the current operating condition, oscillation mode discrimination is performed, and key mode information under the current operating condition is obtained, leading to the determination of the optimal controllable and observable node position under the current operating condition; specifically:

[0085] Based on the extracted impedance data of each unit of the new energy grid-connected system under the current operating conditions, the node admittance matrix of the new energy grid-connected system is established based on the impedance data. The oscillation mode is calculated based on the node admittance matrix. The key oscillation mode is identified based on the frequency domain characteristics of the oscillation mode. The presence of oscillation risk is determined based on the position of the real part of the key mode in the complex plane. If the real part of the key mode is in the left half-plane, there is an oscillation risk. If the real part of the key mode is in the right half-plane, there is no oscillation risk.

[0086] The relationship between the node admittance matrix and the system oscillation mode can be proven as follows: The relationship between the node voltage and node current in the power system is:

[0087] I = YU

[0088]

[0089] Where n is the number of nodes in the power system, and also the order of the node admittance matrix, U is the node voltage, and I is the node injected current. The node admittance matrix in the above equation is then diagonalized:

[0090]

[0091] In the above formula, L is the left eigenvector matrix, whose row vectors are the left eigenvectors of the node admittance matrix Y; Λ is the eigenma matrix, whose diagonal elements are the eigenvalues ​​of the node admittance matrix Y; and V is the right eigenvector matrix, whose column vectors are the right eigenvectors of the node admittance matrix Y. The diagonal elements of the eigenma matrix Λ represent the modal information of each node. When the values ​​of the diagonal elements of Λ are close to 0, the corresponding mode is the key oscillation mode.

[0092] The steps to obtain the optimal controllable and observable node of the oscillation key mode are as follows:

[0093] The key modes under the current operating conditions are obtained through the modal analysis method. The left and right eigenvectors of the key modes are calculated. Based on the left and right eigenvectors, the participation factor of the key modes at each node is calculated. The node with the largest participation factor is the best controllable and observable node.

[0094] For the i-th oscillation mode, its participation factor is calculated as follows:

[0095]

[0096] Based on the oscillation mode discrimination results, if it is determined that there is no oscillation risk under the current operating conditions, the power flow of each node in the new energy grid-connected system will continue to be monitored in real time.

[0097] Based on the oscillation mode discrimination result, when it is determined that there is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the best controllable and observable node.

[0098] The additional emergency controller enhances the damping of critical modes and suppresses oscillations.

[0099] A schematic diagram of the changes in system oscillation modes before and after applying emergency control is shown below. Figure 6 As shown in the figure, after the application of emergency control, all three modes move towards the left half of the complex plane, and the modal damping is improved. The critical mode, which is closest to the imaginary axis, moves the most significantly.

[0100] The impedance characteristics of the power grid and renewable energy power plants before and after the application of emergency control measures are shown in the following figure. Figure 7 As shown, before emergency control, the phase difference between the grid and source impedances at the critical mode frequency was 185.4°, and the phase margin was -5.4°. After emergency control, the phase difference between the grid and source impedances at the critical mode frequency became 154.6°, and the phase margin became 25.4°. Emergency control improved the phase margin of the new energy grid-connected system. The conclusion is consistent with the modal analysis conclusion.

[0101] The Nyquist plot of the ratio of grid impedance to renewable energy plant impedance before and after applying emergency control is shown below. Figure 8 As shown, the Nyquist curve of the grid-source impedance ratio before emergency control surrounds the point (-1,j0) counterclockwise and is located within the safety margin circle. After emergency control, the Nyquist curve of the grid-source impedance ratio no longer surrounds (-1,j0) but moves away from the point (-1,j0), indicating that the stability margin of the new energy grid-connected system has been improved.

[0102] The time-domain simulation results of the active power and three-phase current at the grid connection point before and after emergency control are as follows: Figure 9 As shown, the feasibility of emergency control to suppress oscillations was verified from the time-domain simulation level.

[0103] Specifically, the modal information before and after applying emergency control is shown in Table 1:

[0104] Table 1

[0105]

[0106] It can be seen that after applying emergency control to the new energy power station, the damping ratio of the oscillation mode corresponding to each resonant frequency increased, with the key mode showing the largest increase. The propagation of oscillation in the new energy power station was suppressed, and the emergency control improved the stability of the new energy power station.

[0107] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0108] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0109] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for precise source identification and emergency control of oscillations in a new energy plant, characterized in that, The method comprises the following steps: Step one: obtaining impedance data of each power electronic equipment in the new energy station in the new energy grid-connected system under different operating conditions and storing, obtaining impedance data of the large power grid under different operating conditions by frequency sweeping and storing; Step two: designing a control structure of the new energy oscillation emergency controller, defining a key modal stability index, and traversing optimal parameters of the emergency controller based on the maximum of the modal stability index, and setting the new energy oscillation emergency controller with the optimal parameters; The control structure of the oscillation emergency controller comprises a proportional link, a band-pass filter link, a phase correction link and a limiting link, and the four links are cascaded to form the oscillation emergency controller, the input signal of the controller is an alternating voltage dq axis component, and the controller is additionally positioned at the input end of the current inner loop control; The transfer function expression of the controller is: wherein is the transfer function of the band-pass filter section, which is composed of a first-order low-pass filter section and a first-order high-pass filter section in cascade, is the damping ratio of the band-pass filter, is the cut-off frequency of the band-pass filter, is the Laplace operator, wherein is the transfer function of the phase correction section, which comprises two phase correction controllers in cascade, is the upper limit cut-off time constant of the phase correction controller, is the lower limit cut-off time constant of the phase correction controller, is the Laplace operator, is the transfer function of the oscillation emergency control structure, is the proportional coefficient of the proportional section; Step three: judging the operating conditions of the new energy equipment and the large power grid based on real-time monitoring results of the node flow in the new energy grid-connected system, and extracting the impedance of the large power grid and each device of the new energy under the corresponding operating conditions from the impedance data obtained by frequency sweeping; Step four: combining the extracted impedance under the current operating condition, discriminating the oscillation mode, obtaining the key modal information under the current operating condition, and obtaining the best controllable and observable node position under the current operating condition; Step five: based on the oscillation mode discrimination result, if there is no oscillation risk under the current operating condition, continue to monitor the real-time node flow in the new energy grid-connected system; Step six: based on the oscillation mode discrimination result, if there is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the best controllable and observable node position; Step seven: based on the added emergency controller, the damping of the key mode is improved and the oscillation is suppressed.

2. The method of claim 1, wherein, The step one further comprises the following steps: The grid-connected point is selected as the harmonic signal injection point, the harmonic voltage source is selected as the signal source, the harmonic injection amplitude is set according to the size of the response voltage of the real-time injected harmonic voltage, and the harmonic signal injection amplitude is selected as 10% of the response harmonic voltage amplitude.

3. The method of claim 1, wherein, The step two further comprises the following steps: Setting the cutoff frequency in a bandpass filter section , the upper limit cutoff time constant in a phase correction section , the lower limit cutoff time constant satisfying the relationship among the three: wherein is the bandwidth angular frequency, which characterizes the correction range of the phase correction link, and the bandwidth angular frequency and the proportional link proportional coefficient is set as the control variable, and the target function is the negative of the real part of the characteristic root corresponding to the critical mode, and the target function is: wherein is the largest eigenvalue in real part among all eigenvalues, i.e. the critical eigenvalue, also called critical oscillation mode, is the real part algorithm; When the value of and is changed , the value of , the real part of the critical modal eigenvalue is in the left half plane and is farthest from the imaginary axis, and the control parameter at this time is the optimal control parameter of the selected emergency control.

4. The method of claim 1, wherein, The step three further comprises the following steps: Based on the online monitoring device, the operating conditions of the current large power grid and new energy equipment are judged, the impedance data of the large power grid and the new energy station under the current operating condition are extracted based on the stored impedance data of the large power grid under different operating conditions obtained by frequency sweeping and the stored impedance data of each new energy equipment in the new energy station under different operating conditions obtained by frequency sweeping.

5. The method of claim 1, wherein, The step four further comprises the following steps: Based on the impedance data of each unit of the new energy grid-connected system under the current operating condition, a node admittance matrix of the new energy grid-connected system is established based on the impedance data, an oscillation mode is calculated based on the node admittance matrix, a key oscillation mode is judged based on the frequency domain characteristics of the oscillation mode, left and right eigenvectors of the key mode are calculated, participation factors of the key mode at each node are calculated based on the left and right eigenvectors, and the node with the largest participation factor is the best controllable and observable node.

6. The method of claim 1, wherein, The step four further comprises the following steps: The node admittance matrix contains system oscillation mode information, and the relationship between the node voltage and the node current of the power system is: wherein is the number of nodes of the power system, also the order of the nodal admittance matrix, is the node voltage, is the node injection current, the nodal admittance matrix in the above equation is diagonalized by matrix In the above formula is the left eigenvector matrix, whose row vectors are the left eigenvectors of the node admittance matrix is the characteristic matrix, whose diagonal elements are the eigenvalues of the node admittance matrix is the right eigenvector matrix, whose column vectors are the right eigenvectors of the node admittance matrix The diagonal elements of the characteristic matrix characterize the modal information of each node. When the diagonal elements of the characteristic matrixare close to 0, the corresponding mode is a critical oscillation mode.​​ 7. The method of claim 1, wherein, The step four further comprises the following steps: The step of obtaining the optimal controllable and observable node of the oscillation critical mode is: obtaining the critical mode under the current working condition through the modal analysis method, calculating the left and right eigenvectors of the critical mode, calculating the participation factor of the critical mode at each node based on the left and right eigenvectors, and the node with the largest participation factor is the optimal controllable and observable node; In particular, for the first oscillation mode, the participation factor is calculated as follows: wherein is a left eigenvector matrix whose row vectors are the node admittance vectors of the left eigenvectors of is a right eigenvector matrix whose column vectors are the node admittance vectors of the right eigenvectors of is the participation factor corresponding to the th oscillation mode.

8. The method of claim 1, wherein, The steps five and six further comprise the following steps: The basis for judging whether there is an oscillation risk is: judging whether there is an oscillation risk according to the position of the real part of the critical mode in the complex plane, if the real part of the critical mode is in the left half plane, there is an oscillation risk, if the real part of the critical mode is in the right half plane, there is no oscillation risk, based on the oscillation mode discrimination result, if it is judged that there is no oscillation risk under the current working condition, the real-time monitoring of the power flow of each node in the new energy grid-connected system is continued; When it is judged that there is an oscillation risk, an emergency controller is added to the control loop of the new energy equipment at the optimal controllable and observable node.

9. A storage medium, characterized by The program stored in the storage medium, when running, controls the device where the storage medium is located to execute the new energy station oscillation accurate tracing and emergency control method according to any one of claims 1-8. The program stored in the storage medium, when running, controls the device where the storage medium is located to execute the new energy station oscillation accurate tracing and emergency control method according to any one of claims 1-8.

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