A method and system for suppressing transient overvoltage of new energy power grid

Abstract

The present application relates to the technical field of excitation control of high-voltage direct-connection phase modifier, and specifically discloses an excitation control method and system for suppressing transient overvoltage of new energy power grid, comprising: real-time monitoring of machine terminal voltage and reactive power of high-voltage direct-connection phase modifier, and calculation of machine terminal voltage change rate and reactive power change rate; judging whether the system is in voltage recovery stage according to the machine terminal voltage change rate and the reactive power change rate; if the system is in voltage recovery stage, generating a reverse additional voltage reference value according to the detected redundant reactive power; superimposing the reverse additional voltage reference value to the machine terminal voltage reference value of the high-voltage direct-connection phase modifier to generate demagnetization instruction, and suppressing the redundant reactive power output by the high-voltage direct-connection phase modifier; the reverse additional voltage reference value automatically exits after superimposing for a preset time, and the system returns to normal excitation control.

Description

Technical Field

[0001] This invention relates to the field of excitation control technology for high-voltage direct-connected synchronous condensers, specifically to an excitation control method and system for suppressing transient overvoltages in new energy power grids. Background Technology

[0002] The penetration rate of new energy power generation, such as wind and solar power, in the power system continues to increase. However, new energy units are generally connected to the grid through power electronic converters, whose inherent low rotational inertia and weak short-circuit capacity significantly reduce the overall inertia and voltage support capacity of the power system. After disturbances such as short-circuit faults, sudden large-capacity load connections, or disconnection of new energy power plants, the system often experiences severe transient processes. After the fault is cleared, the voltage enters the recovery phase. If the control response of dynamic reactive power compensation equipment (such as synchronous condensers and SVG) in the system does not match the dynamics of the grid, transient overvoltage problems are very likely to occur. Excessively high transient voltages not only threaten the insulation safety of electrical equipment such as new energy units and transformers, but may also cause relay protection malfunctions and large-scale disconnection of new energy units from the grid, seriously restricting the safe and stable operation of power grids with a high proportion of new energy.

[0003] High-voltage direct-connected synchronous condensers, as a type of large-capacity synchronous reactive power compensation device, directly connect to the high-voltage power grid (typically 35kV), eliminating the need for a step-up transformer. They offer advantages such as fast dynamic response, large reactive power output capacity, and strong overload capacity, making them key equipment for improving the short-circuit capacity of the power grid and enhancing transient voltage support capabilities. Their excitation control system is the core for regulating reactive power output and maintaining stable terminal voltage. Currently, high-voltage direct-connected synchronous condensers generally use conventional PID excitation controllers based on terminal voltage feedback. While this controller performs well under steady-state conditions and with small disturbances, it has inherent limitations when dealing with rapid transient processes after a fault. 1. Response Lag and Overshoot Issues: Conventional PID control is a deviation regulation, meaning its action begins after a deviation occurs between the actual and reference values ​​of the generator terminal voltage. During the transient process of fault clearing and rapid voltage recovery, due to the electromagnetic inertia of the excitation system (including the excitation regulator, excitation power unit, and generator field winding), there is an unavoidable lag in the generation, transmission, and execution of control commands. When the voltage is detected to have recovered or even exceeded the reference value, the demagnetization command issued by the controller has not yet had time to fully act on the magnetic field. This causes the synchronous condenser to continue outputting, or even briefly over-outputting, the strong excitation reactive power required during the fault, forming "redundant reactive power." This redundant reactive power injected into the system becomes a key factor in exacerbating the amplitude and prolonging the duration of transient overvoltage.

[0004] 2. Single Control Mode: Existing excitation control strategies typically employ a single control mode, failing to identify and implement differentiated control objectives based on different stages of the power grid transient process (such as the fault occurrence stage, fault duration stage, and voltage recovery stage). During a fault, the synchronous condenser needs to rapidly excite to support the voltage; while during the voltage recovery stage, reactive power output needs to be quickly suppressed to avoid overvoltage. Conventional controllers struggle to adaptively complete this rapid role transition.

[0005] 3. Parameter tuning contradictions: In pursuit of rapid fault support capabilities, a strong control gain is often required, but this may lead to more severe overshoot and oscillations during the voltage recovery phase; conversely, reducing the gain to achieve smoothness during the recovery phase weakens the fault support strength. This contradiction between control performance is difficult to reconcile within the conventional PID framework.

[0006] To address the aforementioned issues, some improvements have been implemented in existing technologies, such as optimizing PID controller parameters to adapt to wider frequency band disturbances; introducing state feedback, fuzzy control, or adaptive control algorithms based on modern control theory; or optimizing the reactive power distribution of the system through coordinated control of multiple synchronous condensers, SVG, and other reactive power compensation devices. However, these solutions may still fail to fundamentally solve the motion lag problem caused by the physical inertia of the excitation system, or they may make the control system overly complex, reduce reliability, and make engineering implementation difficult.

[0007] Therefore, in response to the specific technical problem of high-voltage direct-connected synchronous condensers outputting redundant reactive power due to lag in excitation response during transient processes in new energy power grids, especially during the voltage recovery phase, which in turn worsens transient overvoltage, there is an urgent need for a new excitation control strategy that can maintain the strong support advantage of conventional controllers during faults while quickly and accurately suppressing redundant reactive power output during the voltage recovery phase. Summary of the Invention

[0008] To achieve the objective of this invention, this application provides an excitation control method for suppressing transient overvoltages in a new energy power grid, comprising: Step S1: Monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and calculate the rate of change of terminal voltage and reactive power. Step S2: Determine whether the voltage recovery phase is underway based on the rate of change of the terminal voltage and the rate of change of reactive power. Step S3: If the voltage recovery phase is underway, a reverse additional voltage reference value is generated based on the detected redundant reactive power. Step S4: The reverse additional voltage reference value is superimposed on the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser. Step S5: The superimposed reverse voltage reference value will automatically exit after a preset time and return to normal excitation control.

[0009] In some specific embodiments, step S2, determining whether the voltage recovery phase is underway, includes: When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, it is determined that the fault stage has begun. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the system is determined to have entered the voltage recovery phase.

[0010] In some specific embodiments, the criteria for determining the fault stage are: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold.

[0011] In some specific embodiments, the determination criteria for the voltage recovery phase are as follows: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

[0012] In some specific embodiments, the reverse additional voltage is determined according to the following formula: Among them, K Q ΔQ is the adjustable gain coefficient, and ΔQ is the deviation between the current reactive power and the steady-state reference value, used to characterize the redundant reactive power.

[0013] In some specific embodiments, the redundant reactive power Δ Q The resulting transient overvoltage component Δ U _ov The relationship is: in, X s For the system equivalent reactance, U s The operating voltage at the grid connection point, Δ Q This is redundant reactive power.

[0014] In some specific embodiments, the preset time is set according to the response lag time of the excitation system, ranging from 10ms to 20ms.

[0015] To achieve the same inventive objective, this application also provides an excitation control system for suppressing transient overvoltages in a new energy power grid, comprising: Monitoring module: Used to monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and to calculate the rate of change of terminal voltage and reactive power. Judgment module: used to determine whether the system is in the voltage recovery phase based on the rate of change of the terminal voltage and the rate of change of reactive power; Additional control module: used to generate a reverse additional voltage reference value based on the detected redundant reactive power if the voltage recovery phase is in progress; Suppression module: used to superimpose the reverse additional voltage reference value onto the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser; Exit Module: This module automatically exits after a preset time following the superposition of the reverse additional voltage reference value, reverting to normal excitation control.

[0016] In some specific embodiments, the determination module determines whether the voltage recovery phase is underway, including: When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, it is determined that the fault stage has begun. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the voltage recovery phase is determined to have begun.

[0017] In some specific embodiments, the criteria for determining the fault stage are: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold; The criteria for determining the voltage recovery phase are as follows: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

[0018] The high-voltage direct-connected synchronous condenser staged additional excitation controller and method provided by this invention have the following significant advantages compared with the prior art: 1. This invention achieves precise, phased control of transient processes, fundamentally suppressing redundant reactive power during the voltage recovery phase. By monitoring the rate of change of generator terminal voltage and reactive power in real time, the invention intelligently identifies the transient phase (fault phase and voltage recovery phase) of the system. During the voltage recovery phase, an innovative reverse additional voltage reference value, dynamically calculated based on redundant reactive power, is introduced and directly superimposed onto the voltage reference of the original excitation system. This mechanism allows the excitation system to receive a clear "demagnetization" command at the start of voltage recovery, thereby actively and quickly offsetting the redundant reactive power continuously output due to excitation inertia. This suppresses the generation and deterioration of transient overvoltage at its source, solving the core problem of "overcorrection" caused by response lag in conventional PID control.

[0019] 2. Significantly improves transient voltage recovery quality and system safety level. Through the aforementioned active suppression mechanism, this invention can effectively reduce the peak value of transient overvoltage after fault clearance and shorten the duration of overvoltage. Simulation results show that under typical faults such as three-phase short circuits and commutation failures, the peak value of transient overvoltage at the renewable energy generator terminal can be significantly suppressed after applying this control strategy, and the voltage recovery curve is more stable. This directly reduces the impact risk of overvoltage on the insulation of renewable energy units, cables, transformers, and other grid-connected equipment, reduces the possibility of protection maloperation, and thus greatly improves the transient voltage safety and operational reliability of the power grid under high-proportion renewable energy access.

[0020] 3. The control structure is simple and reliable, easy to implement in engineering, and perfectly compatible with the original system. The core of this invention lies in adding an "additional control" module based on explicit criteria. This module only operates during specific voltage recovery phases and automatically exits after a preset time. It does not change the internal structure and parameters of the original excitation controller, requires no complex algorithm reconstruction or parameter tuning, and achieves functional enhancement simply by externally superimposing signals. This "plug-in" design concept allows this invention to be easily integrated into the excitation control system of existing high-voltage direct-connected synchronous condensers, with low implementation cost, minimal modification workload, and no impact on the performance of the original controller under other operating conditions, making it highly practical for engineering applications.

[0021] 4. Effectively overcomes the contradiction between control performance and achieves a balance between fault support and overvoltage suppression. This invention decouples the seemingly contradictory control objectives of "strong excitation support during faults" and "rapid suppression during voltage recovery" through a phased control strategy. During the fault phase, strong reactive power support is provided entirely by a high-performance conventional controller; during the voltage recovery phase, an auxiliary controller quickly intervenes to "brake" the system. This collaborative model eliminates the need for the controller to consider all dynamic processes under a single parameter set, thus perfectly solving the problem of voltage recovery overshoot while ensuring strong fault ride-through capability, and optimizing overall transient performance.

[0022] In summary, this invention, with its simple and ingenious design, effectively solves the critical transient overvoltage problem faced by high-voltage direct-connected synchronous condensers when supporting new energy power grids, significantly improving the dynamic performance of the control system and the safety and stability level of the power grid. It has important theoretical value and broad engineering application prospects. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic flowchart of an excitation control method for suppressing transient overvoltages in a new energy power grid, provided as an embodiment of the present invention; Figure 2 A schematic flowchart of an excitation control method for suppressing transient overvoltages in a new energy power grid, provided as an embodiment of the present invention; Figure 3 A control principle block diagram of an excitation control method for suppressing transient overvoltages in a new energy power grid, provided as an embodiment of the present invention; Figure 4 An equivalent model diagram of a wind power transmission system for an excitation control method used to suppress transient overvoltages in a new energy power grid, provided as an embodiment of the present invention; Figure 5 Comparison curves of voltage at the new energy generator terminal when a high-voltage direct-connected synchronous condenser has additional excitation control during a three-phase short-circuit fault and when a conventional synchronous condenser is connected to the grid. Figure 6 Comparison curves of reactive power output of high-voltage direct-connected synchronous condensers with and without additional excitation control during three-phase short-circuit faults and when conventional synchronous condensers are connected to the grid. Figure 7 The comparison curves of the voltage at the new energy generator terminal when the high-voltage direct-connected synchronous condenser has additional excitation control and when a conventional synchronous condenser is connected to the grid are shown for the three phase commutation failures. Figure 8 Comparison curves of voltage at the new energy generator terminal when the high-voltage direct-connected synchronous condenser has additional excitation control during three commutation failures and when a conventional synchronous condenser is connected to the grid. Figure 9 This is a schematic diagram of an excitation control system for suppressing transient overvoltages in a new energy power grid, provided as an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0027] Example 1 One embodiment of the present invention provides an excitation control method for suppressing transient overvoltages in new energy power grids, referring to... Figure 1-8 As shown, it includes: Step S1: Monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and calculate the rate of change of terminal voltage and reactive power. Step S2: Determine whether the system is in the voltage recovery phase based on the terminal voltage change rate and the reactive power change rate; In a specific embodiment of the present invention, step S2, determining whether the system is in the voltage recovery phase, includes: When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, the system is determined to have entered a fault phase. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the system is determined to have entered the voltage recovery phase.

[0028] In a specific embodiment of the present invention, the determination condition for the fault stage is: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold.

[0029] In a specific embodiment of the present invention, the determination condition for the voltage recovery stage is: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

[0030] Step S3: If the system is in the voltage recovery phase, generate a reverse additional voltage reference value based on the detected redundant reactive power; In one specific embodiment of the present invention, the reverse additional voltage is determined according to the following formula: Among them, K QΔQ is the adjustable gain coefficient, and ΔQ is the deviation between the current reactive power and the steady-state reference value, used to characterize the redundant reactive power.

[0031] In one specific embodiment of the present invention, the redundant reactive power Δ Q The resulting transient overvoltage component Δ U _ov The relationship is: in, X s For the system equivalent reactance, U s The operating voltage at the grid connection point, Δ Q This is redundant reactive power.

[0032] Step S4: The reverse additional voltage reference value is superimposed on the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser. Through the aforementioned active suppression mechanism, this invention can effectively reduce the peak value of transient overvoltage after fault clearance and shorten the duration of overvoltage. Simulation results show that under typical faults such as three-phase short circuits and commutation failures, the peak value of transient overvoltage at the renewable energy generator terminal can be significantly reduced and the voltage recovery curve is more stable after applying this control strategy. This directly reduces the impact risk of overvoltage on the insulation of grid-connected equipment such as renewable energy generators, cables, and transformers, reduces the possibility of protection maloperation, and thus greatly improves the transient voltage safety and operational reliability of the power grid under high-proportion renewable energy access.

[0033] Step S5: The superimposed reverse voltage reference value automatically exits after a preset time, and the system returns to normal excitation control.

[0034] In one specific embodiment of the present invention, the preset time is set according to the response lag time of the excitation system, and the range is 10ms to 20ms.

[0035] Figure 2 A schematic flowchart of an excitation control method for suppressing transient overvoltages in a new energy power grid, provided as an embodiment of the present invention; Figure 3 This is a block diagram illustrating the control principle of an excitation control method for suppressing transient overvoltages in a renewable energy power grid, provided as an embodiment of the present invention. In this control strategy, a high-voltage direct-connected synchronous condenser adjusts its excitation current in stages to suppress transient overvoltages by real-time detection of the terminal voltage change rate dUt / dt and the reactive power increment change rate dQ / dt. Specifically, the controller maintains conventional excitation support during a fault, while rapidly introducing reverse excitation control during the voltage recovery phase after voltage recovery. This quickly reduces the redundant reactive power output of the synchronous condenser, thereby suppressing the overvoltage amplitude and shortening its duration.

[0036] When the system is operating normally, the auxiliary excitation control module is not activated, and the synchronous condenser is controlled by the conventional PID voltage loop. When a significant drop in the generator terminal voltage and a rapid increase in reactive power are detected, the system is determined to have entered a fault state and locked into fault preparation mode. When the voltage drop trend stops and the reactive power increase trend ends, the voltage is determined to have recovered, and reverse excitation control is immediately activated. A negative auxiliary voltage reference value is superimposed on the generator terminal voltage reference value, prompting the excitation system to demagnetize rapidly. This auxiliary control action automatically exits after a preset time, and the system returns to normal control.

[0037] To verify the effectiveness of this phased additional excitation control strategy, for example... Figure 4 Simulation analysis was performed on the equivalent model of the wind power transmission system shown. Three-phase short-circuit faults and three consecutive commutation failures were set in the system, and the voltage and reactive power responses were compared under three schemes: conventional synchronous condenser, high-voltage direct-connected synchronous condenser without additional control, and synchronous condenser with additional control.

[0038] Figure 5 The figures show the voltage comparison curves of the new energy generator terminals under a three-phase short-circuit fault. Simulation results show that after adopting the proposed staged additional excitation control strategy, the peak value of transient overvoltage in the voltage recovery stage is significantly reduced, and the voltage recovery process is more stable. Figure 6 The figures show a comparison of reactive power output curves under a three-phase short-circuit fault using a high-voltage direct-connected synchronous condenser. It can be seen that, under the additional control strategy, the synchronous condenser can quickly switch from outputting reactive power to absorbing reactive power after voltage recovery, effectively suppressing voltage surges caused by reactive power redundancy.

[0039] Figure 7 The figures show a comparison of the terminal voltage curves of the new energy vehicle under three commutation failures. During the continuous commutation failure process, the proposed strategy can effectively suppress voltage overshoot during each commutation recovery period and control the overvoltage peak value to a low level. Figure 8 The output curves show the reactive power output of the high-voltage direct-connected synchronous condenser under three commutation failures. The additional control strategy enables the synchronous condenser to quickly switch to reactive power absorption mode during each voltage recovery phase, significantly reducing excess reactive power in the system and shortening the voltage recovery time.

[0040] Based on the simulation results above, the proposed control strategy can effectively reduce the amplitude of transient overvoltage and accelerate voltage recovery under both three-phase short circuit and continuous commutation failure faults, verifying its feasibility and effectiveness in improving the transient voltage safety of new energy power grids.

[0041] The core of this invention lies in adding an "additional control" module based on explicit criteria. This module only operates during specific voltage recovery phases and automatically exits after a preset time. It does not alter the internal structure and parameters of the original excitation controller, requiring no complex algorithm reconstruction or parameter tuning; it enhances functionality solely through external signal superposition. This "plug-in" design allows for easy integration into existing high-voltage direct-connected synchronous condenser excitation control systems, resulting in low implementation costs, minimal modification work, and no impact on the original controller's performance under other operating conditions, making it highly practical for engineering applications.

[0042] This invention decouples the seemingly contradictory control objectives of "strong excitation support during faults" and "rapid suppression during voltage recovery" through a phased control strategy. During the fault phase, strong reactive power support is provided entirely by a high-performance conventional controller; during the voltage recovery phase, an auxiliary controller quickly intervenes to "brake" the system. This collaborative approach eliminates the need for the controller to consider all dynamic processes under a single parameter set, thus perfectly resolving the voltage recovery overshoot problem while ensuring strong fault ride-through capability, thereby optimizing overall transient performance.

[0043] Example 2 One embodiment of the present invention provides an excitation control system for suppressing transient overvoltages in new energy power grids, referring to... Figure 9 As shown, it includes: Monitoring module 10: Used to monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and to calculate the rate of change of terminal voltage and reactive power. Judgment module 20: used to determine whether the system is in the voltage recovery phase based on the rate of change of the terminal voltage and the rate of change of reactive power; Additional control module 30: used to generate a reverse additional voltage reference value based on the detected redundant reactive power if the system is in the voltage recovery phase; Suppression module 40: used to superimpose the reverse additional voltage reference value onto the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser; Exit module 50: This module automatically exits after a preset time following the superposition of the reverse additional voltage reference value, and the system returns to normal excitation control.

[0044] In some specific embodiments, the determination module 20 determines whether the system is in the voltage recovery phase, including: When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, the system is determined to have entered a fault phase. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the system is determined to have entered the voltage recovery phase.

[0045] In some specific embodiments, the criteria for determining the fault stage are: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold; The criteria for determining the voltage recovery phase are as follows: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

[0046] This invention intelligently identifies the transient phase (fault phase and voltage recovery phase) of the system by real-time monitoring of the rate of change of terminal voltage and reactive power. During the voltage recovery phase, it innovatively introduces a reverse additional voltage reference value dynamically calculated based on redundant reactive power, which is directly superimposed on the voltage reference of the original excitation system. This mechanism allows the excitation system to receive a clear "demagnetization" command at the start of voltage recovery, thereby actively and quickly offsetting the redundant reactive power continuously output due to excitation inertia. This suppresses the generation and deterioration of transient overvoltage at its source, solving the core problem of "overcorrection" caused by response lag in conventional PID control.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0048] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the functions specified in one or more boxes. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the invention. Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0049] The methods and apparatus provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0050] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "a specific embodiment" or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An excitation control method for suppressing transient overvoltages in new energy power grids, characterized in that, include: Step S1: Monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and calculate the rate of change of terminal voltage and reactive power. Step S2: Determine whether the voltage recovery phase is underway based on the rate of change of the terminal voltage and the rate of change of reactive power. Step S3: If the voltage recovery phase is underway, a reverse additional voltage reference value is generated based on the detected redundant reactive power. Step S4: The reverse additional voltage reference value is superimposed on the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser. Step S5: The superimposed reverse voltage reference value will automatically exit after a preset time and resume normal excitation control.

2. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 1, characterized in that, In step S2, determining whether the voltage recovery phase is underway includes: When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, it is determined that the fault stage has begun. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the voltage recovery phase is determined to have begun.

3. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 2, characterized in that, The criteria for determining the fault stage are as follows: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold.

4. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 2, characterized in that, The criteria for determining the voltage recovery phase are as follows: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

5. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 1, characterized in that, The reverse additional voltage is determined according to the following formula: Among them, K Q ΔQ is the adjustable gain coefficient, and ΔQ is the deviation between the current reactive power and the steady-state reference value, used to characterize the redundant reactive power.

6. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 5, characterized in that, The redundant reactive power Δ Q The resulting transient overvoltage component Δ U _ov The relationship is: in, X s For the system equivalent reactance, U s The operating voltage at the grid connection point, Δ Q This is redundant reactive power.

7. The excitation control method for suppressing transient overvoltages in a new energy power grid according to claim 1, characterized in that, The preset time is set according to the response lag time of the excitation system, and ranges from 10ms to 20ms.

8. An excitation control system for suppressing transient overvoltages in new energy power grids, characterized in that, include: Monitoring module: Used to monitor the terminal voltage and reactive power of the high-voltage direct-connected synchronous condenser in real time, and to calculate the rate of change of terminal voltage and reactive power. Judgment module: used to determine whether the voltage is in the recovery phase based on the rate of change of the terminal voltage and the rate of change of reactive power; Additional control module: used to generate a reverse additional voltage reference value based on the detected redundant reactive power if the voltage recovery phase is in progress; Suppression module: used to superimpose the reverse additional voltage reference value onto the terminal voltage reference value of the high-voltage direct-connected synchronous condenser to generate a demagnetization command and suppress the redundant reactive power output by the high-voltage direct-connected synchronous condenser; Exit Module: This module automatically exits after a preset time following the superposition of the reverse additional voltage reference value, reverting to normal excitation control.

9. The excitation control system for suppressing transient overvoltages in a new energy power grid according to claim 8, characterized in that, The determination module includes determining whether the voltage recovery phase is underway. When a rapid drop in terminal voltage and a rapid increase in reactive power are detected, it is determined that the fault stage has begun. After the fault phase is locked, the rate of change of the generator terminal voltage and the rate of change of the reactive power are continuously monitored. When a rapid rise in voltage and a rapid drop in reactive power are detected, the voltage recovery phase is determined to have begun.

10. The excitation control system for suppressing transient overvoltages in a new energy power grid according to claim 9, characterized in that, The criteria for determining the fault stage are as follows: When the terminal voltage of the high-voltage direct-connected synchronous condenser is lower than a set threshold, and the rate of change of the terminal voltage is less than the negative of the first preset threshold, and the rate of change of the reactive power is greater than the second preset threshold; The criteria for determining the voltage recovery phase are as follows: The rate of change of the terminal voltage is greater than a first preset threshold, and the rate of change of the reactive power is less than the negative of a second preset threshold.

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