Method and device for cooperatively inhibiting multi-band oscillation through three channels of synchronous unit

Abstract

The invention belongs to the field of oscillation suppression of a power system, and particularly discloses a method and a device for cooperatively suppressing multi-band oscillation through three channels of a synchronous unit, and the method comprises the steps: employing a reactive damping controller, a PSS damping controller and a speed regulation side damping controller based on a flexible excitation system and a speed regulator; the damping components respectively act on the first channel, the second channel and the third channel to generate damping so as to suppress multi-band oscillation; the problems of time-varying characteristics and diversity of the system and complex and changeable oscillation modes under the double-high characteristic are considered, and parameters of the damping controller are dynamically optimized on line in real time based on reinforcement learning; key frequency bands suppressed by different channels are dynamically and flexibly adjusted according to the monitored change condition of the oscillation mode of the system; the optimal damping configuration can be realized, wider frequency band and stronger damping are provided, the conditions of complex and changeable oscillation modes and frequency band widening brought by a high-proportion new energy power grid are dealt with more efficiently and flexibly, and the safe and stable operation capability of the system is improved.

Description

Technical Field

[0001] The present application belongs to the field of power system oscillation suppression, and more specifically, relates to a method and device for three-channel coordinated suppression of multi-band oscillations in a synchronous unit. Background Art

[0002] The increasing degree of power electronics in the power system's "source-grid-load-storage" architecture has resulted in a "dual high" system characterized by a high proportion of renewable energy generation and power electronics. While renewable energy generation offers low-carbon benefits, it also increases the factors influencing the system's dynamic behavior. In particular, the introduction of multi-level control based on converters has led to profound changes in the dynamic characteristics of this "dual high" power system, raising new stability issues.

[0003] Under the "double high" characteristics, the dynamic response of the power system has become nonlinear and strongly coupled, affecting the oscillation characteristics of the power system units and making the system's oscillation patterns increasingly complex. On the one hand, for power grids with a large proportion of hydropower, the water hammer effect of hydropower units can worsen system damping when the speed regulator parameters are improperly set, triggering ultra-low frequency oscillations that continue to decrease in frequency. On the other hand, the impact of the high proportion of renewable energy access has squeezed the operating space of conventional units, and the power system structure (inertia distribution) and operating mode (power flow) have undergone profound changes. As a result, the oscillation modal characteristics that originally occurred between synchronous units have become more complex, the oscillation frequency band has become wider, and the damping characteristics of existing units are unable to meet the power balance requirements between units.

[0004] New oscillation issues arising from the high penetration of renewable energy into the power grid not only affect the efficiency of power supply systems but, in severe cases, can even lead to large-scale power outages, resulting in serious consequences, significant economic losses, and a significant threat to the safe and stable operation of the power grid. For these reasons, optimizing transmission systems, improving control methods, and resolving oscillation issues within these systems have become imperative. To date, the primary approaches to suppressing power system oscillations include adding dynamic correctors to the excitation system and power system stabilizers (PSSs). PSSs are widely accepted for their superior damping characteristics, global adaptability, simple structure, and low cost. However, currently used single-input or dual-input PSSs operate in a single frequency band and are often designed for and perform well in a specific frequency band. However, as oscillation modes become more complex and oscillation frequencies decrease, the limitations of single-band PSSs are becoming increasingly apparent. They cannot adequately address oscillations in the low, medium, and high frequency bands, posing a significant threat to system safety and stability. Furthermore, PSS2Bs provide insufficient positive damping in certain low-frequency regions, and may even produce negative damping, making them ineffective in suppressing low-frequency oscillation modes. In addition, although PSS4B can solve the problem of insufficient amplitude-frequency output of traditional single-band PSS in the low and medium frequency bands, its high control freedom increases the complexity of control design. Its structure is complex, and each bridge arm contains multiple complex transfer function modules with numerous parameters. There are also mutual influences between multiple branches, making it extremely difficult to adjust. It has not yet been effectively applied in actual engineering.

[0005] In general, faced with the complex and changeable oscillation modes and wider frequency bands brought about by a high proportion of new energy power grids, the existing power supply-side additional damping controller is unable to cope with various oscillation modes, and its limitations are becoming increasingly prominent. It is difficult to effectively provide a wider operating frequency band and provide appropriate damping for the complex and changeable oscillation modes. Summary of the Invention

[0006] In response to the defects of the existing technology, the purpose of this application is to provide a method and device for three-channel coordinated suppression of multi-band oscillations in a synchronous unit, aiming to solve the problems of complex and changeable oscillation modes and widening frequency bands brought about by a high proportion of new energy power grids. The existing power supply side additional damping controller is difficult to effectively provide a wider working frequency band in the face of multiple oscillation modes, resulting in the inability to provide suitable damping for complex and changeable oscillation modes.

[0007] To achieve the above objectives, in a first aspect, the present application provides a device for three-channel coordinated suppression of multi-band oscillations of a synchronous unit, comprising: a speed regulation side damping controller, a PSS damping controller, and a reactive damping controller; The synchronous unit includes a flexible excitation system, a generator, a speed control system, and a prime mover. The AC side of the flexible excitation system is connected to the generator terminal via a transformer and connected in parallel to the generator terminal to form a first channel. The reactive damping controller is used to inject reactive damping control through the first channel. The DC side of the flexible excitation system or the output end of the excitation current circuit is connected to the excitation winding of the generator to form a second channel. The PSS damping controller is used to indirectly provide damping control through the generator. The speed control system is connected to the generator rotor shaft via the prime mover to form a third channel. The speed control side damping controller is used to indirectly provide damping control through the prime mover. The speed regulation side damping controller, PSS damping controller and reactive damping controller are used to generate corresponding control signals according to the real-time working signals of the synchronous units, and act on the third channel, second channel and first channel respectively to generate active damping to suppress oscillations in different frequency bands; the frequency bands suppressed by the reactive damping controller and PSS damping controller can be dynamically adjusted according to the oscillation mode of the power system where the synchronous units are located.

[0008] Further preferably, the real-time operating signal of the synchronous unit is one or a combination of speed deviation, power deviation, frequency deviation and excess power.

[0009] Further preferably, when the flexible excitation system is a voltage source type flexible excitation system, it includes a two-stage converter, the front-stage converter is a rectifier device constructed by a voltage source converter VSC; the rear-stage converter is a DC chopper; The AC side of the flexible excitation system is connected via a transformer and in parallel with the generator terminal to form the first channel; The output end of the DC chopper is connected to the excitation winding of the generator to form a second channel.

[0010] Further preferably, when the flexible excitation system is a current source-based flexible excitation system, the AC side of the flexible excitation system is connected via a transformer and connected in parallel with the generator end to form a first channel; The DC side of the flexible excitation system is connected to the excitation winding of the generator to form a second channel.

[0011] Further preferably, the device for collaboratively suppressing multi-band oscillations of three channels of a synchronous unit further includes an online parameter adjustment module for optimizing the parameters of the reactive damping controller, the PSS damping controller, and the speed regulation side damping controller respectively according to the frequency bands suppressed by the first channel, the second channel, and the third channel, in combination with the real-time operating conditions of the power system, through a measurement unit, a reward calculation, and an intelligent agent; Among them, the intelligent agent action is used to optimize the parameters of the speed regulation side damping controller, PSS damping controller and reactive damping controller; the reward is to use the stability index of the synchronous unit as prior knowledge to guide the intelligent agent training, and the optimal damping ratio is used as the target reward; the selection of the intelligent agent action is calculated using the value function method or the policy gradient-based method.

[0012] Further preferably, the reactive damping controller includes a first signal processing unit, a first gain unit, a first lead-lag unit and a first limiter unit; The first signal processing unit is used to use the working parameters of the synchronous unit as the input signal and filter the real-time working signal based on the suppression frequency band; the first gain unit is used to gain the signal output by the first signal processing unit and transmit it to the first lead-lag unit; the first lead-lag unit is used to correct the phase deviation of the equivalent transfer function of the first channel; the first limiting unit is used to limit the output signal of the first lead-lag unit, and the limited signal is used as the output signal.

[0013] Further preferably, the first signal processing unit of the reactive damping controller is a PSS2B signal processing unit that processes the input signal to form acceleration mechanical power; or is a speed sensor for separating signals of each frequency band.

[0014] Further preferably, the PSS damping controller includes a second signal processing unit, a second lead-lag unit and a stabilizer; the second signal processing unit is a PSS2B signal processing unit or a PSS4B mid-frequency band branch signal processing unit, which is used to combine the speed deviation and the power deviation into an integral signal of the acceleration power, which is transmitted to the second lead-lag unit for processing and then input into the stabilizer.

[0015] Further preferably, the speed regulation side damping controller includes a third signal processing unit, a third lead-lag unit, a third gain unit and a third limiting unit; the third signal processing unit is used to filter the real-time working signal based on the third channel suppression frequency band using a slope tracking function, and to isolate the filtered signal.

[0016] In a second aspect, the present application provides a method for collaboratively suppressing multi-band oscillations in three channels of a synchronous unit, comprising the following steps: Step S1: Identify the oscillation mode of the power system where the synchronous generator set is located, and divide the oscillation frequency band of the power system into a first frequency band, a second frequency band, and a third frequency band; Step S2: dynamically adjusting the first frequency band and the second frequency band suppressed by the reactive damping controller and the PSS damping controller according to the change of the power system oscillation mode; Step S3: Utilize the reactive damping controller, the PSS damping controller, and the speed regulation side damping controller to generate corresponding control signals according to the real-time working signals of the synchronous unit, and act on the first channel, the second channel, and the third channel respectively to generate active damping to suppress oscillations in the first frequency band, the second frequency band, and the third frequency band.

[0017] Further preferably, in step S3, the real-time working signal of the synchronous unit is used as the input of the reactive damping controller, and the online parameter adjustment module is used to perform online dynamic optimization of the reactive damping controller parameters through the first channel. A switching signal is generated according to the generated additional damping control signal, and the fully controlled device in the flexible excitation system is disconnected, and reactive power is directly injected or absorbed into the generator end to suppress oscillation damping; The real-time working signal of the synchronous unit is used as the input of the PSS damping controller. The online parameter adjustment module is used to dynamically optimize the parameters of the PSS damping controller online through the second channel, control the excitation of the excitation winding, and generate damping torque for the generator to suppress oscillation. The real-time working signal of the synchronous unit is used as the input of the speed regulation side damping controller. The online parameter adjustment module is used to perform online dynamic optimization of the speed regulation side damping controller parameters through the third channel, and an additional damping control signal is generated to control the speed governor, thereby generating a damping torque for the generator to suppress oscillation.

[0018] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: (1) This application provides a device for three-channel coordinated suppression of multi-band oscillations in a synchronous unit. The device has three channels, wherein the first channel can quickly and flexibly provide damping to the power grid, the second channel can provide greater and more stable damping support to the power grid, and the third channel can change the input power of the unit's prime mover without participating in the change of electromagnetic power. The device has good robustness and also has the characteristics of multi-machine decoupling. While providing damping to the unit itself, it does not bring damping to other units, thus avoiding parameter coordination and installation site selection. The three channels operate in coordination and have good robustness. They can make up for the limited oscillation suppression capability of existing additional damping controllers in the ultra-low frequency band and the poor damping effect for multiple oscillation modes at the same time, providing a wider frequency band and stronger damping.

[0019] (2) This application provides a method for collaboratively suppressing multi-band oscillations in three channels of a synchronous unit. The damping controller parameters corresponding to the three channels can be dynamically optimized online based on reinforcement learning. This method fully utilizes the trial-and-error characteristics of reinforcement learning and the environment interaction and the ability of deep learning to process high-dimensional data. It takes into account the random changes in the steady-state operating point in the actual operation of the power system. By optimizing the damping controller parameters of the three channels online through an intelligent agent, it can more effectively cope with the complex and changeable oscillation patterns of the synchronous unit system.

[0020] (3) This application provides a method for three-channel coordinated suppression of multi-band oscillations of a synchronous unit. The first frequency band corresponding to the first channel controlled by the reactive damping controller and the second frequency band corresponding to the second channel controlled by the PSS damping controller can be dynamically and flexibly adjusted according to the detected changes in the oscillation mode of the synchronous unit. This can give full play to the characteristics of the reactive damping controller that can flexibly and quickly provide damping. It can even use this characteristic to further widen the oscillation suppression frequency band, and hopefully achieve full-band oscillation suppression. In general, this application can improve the robustness of the additional damping controller, widen the working frequency band of the damping controller, and is more conducive to improving the small-disturbance stability and transient performance of the power system, improving the stability performance of the power system in the full frequency band of oscillation, and effectively dealing with the complex and changeable oscillation modes and widening of the frequency band brought about by a high proportion of new energy power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the principle of a device for collaboratively suppressing multi-band oscillations in three channels of a synchronous unit provided in an embodiment of the present application; Figure 2 This is a schematic diagram of the structure of a device for collaboratively suppressing multi-band oscillations in three channels of a synchronous unit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0023] The term "and / or" in this application describes an association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. The symbol " / " in this document indicates that the associated objects are in an "or" relationship, for example, A / B means A or B.

[0024] The terms "first" and "second" and the like in the description and claims of this application are used to distinguish different objects rather than to describe a specific order of the objects.

[0025] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0026] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more.

[0027] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0028] like Figure 1 and Figure 2 As shown, the present application provides a device for three-channel coordinated suppression of multi-band oscillations of a synchronous unit, which acts on a synchronous unit, and the synchronous unit includes: a generator, a prime mover, a speed control system and a flexible excitation system; As an optional implementation, in this embodiment, the prime mover is a water turbine as an example; The flexible excitation system can be a current source-based flexible excitation system or a voltage source-based flexible excitation system; The flexible excitation system in the embodiment of the present application is a voltage source type flexible excitation system, including a two-stage converter; the front-stage converter is a voltage source converter (VSC), that is, Figure 2 The VSC in the rear stage forms a rectifier; the rear stage converter is a DC chopper, forming a chopper; the DC side of the front stage converter VSC is connected in parallel with the input terminal of the rear stage converter; in this embodiment, the switching devices in the front stage converter VSC and the rear stage DC chopper are all fully controlled switching devices IGBT; Figure 2 As shown, in this embodiment, the voltage source converter VSC based on fully controlled devices is a three-phase voltage source two-level structure (this embodiment adopts a two-level structure, but is not limited to a two-level structure, and may also adopt a three-level structure, a five-level structure, or an MMC structure); each phase bridge arm includes an IGBT with two upper and lower parallel diodes, which are sequentially designated as S1 to S6; the emitter and collector of each IGBT are respectively connected to the positive and negative electrodes of the parallel diode; like Figure 2 As shown, in this embodiment, the DC chopper based on the fully controlled device includes two bridge arms, each of which includes an IGBT with two upper and lower parallel diodes, which are sequentially S7 to S10; the emitter and collector of each IGBT are respectively connected to the positive and negative electrodes of the parallel diode; The positive and negative poles of the subsequent DC chopper circuit are connected to the positive and negative poles of the VSC respectively.

[0029] Since in this embodiment, all the switching devices in the VSC and the excitation chopper circuit are fully controlled switching devices IGBT, their control is more flexible and controllable.

[0030] like Figure 1 and Figure 2As shown, in this embodiment, the device for three-channel coordinated suppression of multi-band oscillation of a synchronous unit further includes a transformer group; namely, a first transformer TR1 and a second transformer TR2; The AC side connection terminal of the voltage source converter VSC is connected to the low voltage side of the transformer TR2, and the output terminal of the DC chopper is connected to the excitation winding of the synchronous unit; Or the AC side connection end of the current source type flexible excitation system is connected to the low voltage side of the transformer TR2, and the DC side of the current source type flexible excitation system is connected to the excitation winding of the synchronous unit; like Figure 1 and Figure 2 As shown, in this embodiment, the synchronous unit includes a basic control module of a flexible excitation system and a basic control module of a speed regulation system; The flexible excitation system basic control module is used to implement the basic functions of the excitation system. It generates switching signals based on the terminal voltage feedback value required by the synchronous unit to control the opening and closing of the fully controlled devices in the excitation system, generate excitation current, and control the excitation of the excitation winding to make the terminal voltage of the synchronous unit equal to the command value. The basic control module of the speed control system is used to achieve precise control of the unit speed, power and grid frequency. It adjusts the turbine guide vane opening in a closed loop according to the grid frequency or active power command value, controls the water flow entering the turbine, and thus controls the turbine output mechanical power; like Figure 1 and Figure 2 As shown, in the embodiment of the present application, the synchronous unit further includes a voltage stabilizing capacitor C; The voltage-stabilizing capacitor C is used to ensure the stability of the DC side voltage, provide a stable voltage source for obtaining the excitation current through chopping, providing reactive power to the grid side, and inverting to variable-frequency AC. The two ends of the voltage-stabilizing capacitor C are connected in parallel with the DC side of the voltage source converter VSC and the input end of the DC chopper. In this embodiment, each voltage source converter can adopt Figure 2 The single converter power cabinet shown can also adopt a multi-cabinet parallel structure to increase the capacity of the excitation system, meet the needs of large-capacity synchronous units, and further improve the operational reliability of the system.

[0031] like Figure 1 and Figure 2 As shown, in this embodiment, the three-channel device for collaboratively suppressing multi-band oscillations of a synchronous unit is used to damp oscillations according to different oscillation modes, and its damping control channels include three different channels: The AC side of the flexible excitation system is connected via a second transformer and connected in parallel with the generator terminal to form a first channel for directly injecting reactive damping control into the synchronous unit; The chopper device outputs an excitation current circuit, the output end of which is connected to the excitation winding of the generator to form a second channel for adjusting the excitation current of the generator to indirectly provide damping control to the system through the generator; The speed control system is connected to the generator rotor shaft through the turbine to form a third channel, which is used to adjust the governor signal in the speed control system to indirectly provide damping control to the system through the turbine; More specifically, the device for three-channel coordinated suppression of multi-band oscillation of synchronous units is used to detect the speed deviation of the units. or power deviation The signal generates a corresponding control signal through the additional damping controller, and acts on different channels to generate active damping to suppress oscillations in different frequency bands; the device for the three channels of the synchronous unit to collaboratively suppress multi-band oscillations includes a reactive damping controller, a PSS damping controller, a speed-regulating side damping controller and an online parameter adjustment module based on reinforcement learning; the online parameter adjustment module is used to optimize the parameters of the reactive damping controller, the PSS damping controller and the speed-regulating side damping controller online through the measurement unit, reward calculation and intelligent agent to ensure that the optimal damping configuration is provided to the system in real time; among them, the control device of the first channel is a reactive damping controller, which acts on the rectifier device of the flexible excitation system, and performs online dynamic optimization design of the reactive damping controller parameters based on the online parameter adjustment module and according to the suppression frequency band required by the first channel, and generates a switching signal according to the generated additional damping control signal to control the fully controlled devices in the excitation system The flexible excitation system is used to directly inject or absorb reactive power equal to the command value into the generator end to suppress oscillation damping; the control device of the second channel is a PSS damping controller, which acts on the chopper device of the flexible excitation system. Based on the online parameter adjustment module and according to the suppression frequency band required by the second channel, the PSS parameters are optimized online dynamically, and the excitation winding is controlled, thereby indirectly generating a damping torque to the generator to suppress oscillation damping; the control device of the third channel is a speed regulation side damping controller, which acts on the speed regulator device of the debugging system. Based on the online parameter adjustment module and according to the suppression frequency band required by the third channel, the speed regulator is controlled according to the additional damping control signal generated to control the switching of the fully controlled devices in the excitation system, and indirectly generating a damping torque to the generator through the speed regulation system to perform oscillation damping control.

[0032] like Figure 2 As shown, in this embodiment, the specific structures of the three controllers in the three-channel multi-band oscillation damping coordinated control device are described as follows: The reactive damping controller is composed of a signal processing unit, a gain unit, a lead-lag unit and a limiter unit. The signal processing unit adopts the speed deviation and power deviation As an input signal, it can prevent the reactive power from being reversed too much, and realize signal filtering and other functions based on the first frequency band that the reactive damping controller needs to suppress. The processed signal passes through the gain unit and serves as the input signal of the lead-lag unit. The lead-lag unit is used to correct the phase deviation of the equivalent transfer function of the reactive channel, and then passes through the limiting unit as the output signal of the reactive damping controller; as an optional implementation method, the signal processing unit of the reactive damping controller in this embodiment adopts the PSS2B typical signal processing unit, which converts the input signal speed deviation into and power deviation After processing, the accelerated mechanical power is generated, which can effectively prevent the problem of excessive reactive power back-regulation caused by the rapid output of turbines, etc. However, the signal processing unit is not limited to the typical PSS2B signal processing unit, and a speed sensor that can separate signals in different frequency bands can also be used; As an optional implementation, in this embodiment, the PSS damping controller adopts the classic PSS2B signal processing unit, but is not limited to the PSS2B signal processing unit. The mid-frequency branch signal processing unit in PSS4B can also be adopted; PSS2B is a dual-input PSS, and the input signal is mainly the speed deviation. and power deviation , combining it into an integral signal of the accelerating power, which is then fed into the stabilizer through a lead-lag unit. The PSS2B three-stage lead-lag module makes phase compensation more flexible, easy to implement, and has the advantages of low noise. It can also effectively avoid reactive power fluctuations caused by rapid changes in active power and effectively eliminate back-regulation, thus being widely used. As an optional implementation, in this embodiment, the speed regulation side damping controller is composed of a signal processing unit, a lead-lag unit, a gain unit and a limiter unit, and its input signal is a speed deviation. , but not limited to speed deviation The input signal can also be one or several signal combinations of speed or power deviation. The signal processing unit can be composed of a ramp tracking function and a two-stage DC isolation unit. Signal filtering and DC isolation are realized based on the third frequency band that the speed regulation side damping controller needs to suppress. The processed signal is then adjusted in phase and amplitude by the lead-lag unit and the limiter unit to obtain the output signal. The output signal is generally superimposed on the opening command signal.

[0033] In this embodiment, oscillations in different frequency ranges are allocated to different frequency bands under the action of the signal processing unit, and then processed by the damping controller of the corresponding frequency band channel, and then appropriate damping is provided. That is, the unit can generate damping torque through three different channels based on the three-channel multi-band oscillation damping collaborative control device module to suppress the oscillation of the corresponding frequency band. The suppression frequency band can be effectively expanded, thereby improving the safety and stability of the power generation system.

[0034] A method for three-channel coordinated suppression of multi-band oscillations in a synchronous unit, comprising the following steps: Accurately estimate and analyze the oscillation mode of the power system. As an optional implementation method, in the embodiment of the present application, a signal analysis method such as Fourier transform, wavelet analysis, Prony algorithm, etc. can be used. It is not necessary to know the model parameters in advance. Instead, the system model is reconstructed through the measured wave signal on site, thereby realizing the oscillation pattern recognition and dynamic analysis; the oscillation frequency band of the synchronous unit is divided into a first frequency band, a second frequency band, and a third frequency band; As an optional implementation, the frequency bands may be divided into: a third frequency band (0.01-0.1 Hz), a second frequency band (0.1-2 Hz), and a first frequency band (2-20 Hz); The three-channel multi-band oscillation damping cooperative control device is based on the oscillation frequency band and combines the online parameter adjustment module based on reinforcement learning to perform online dynamic parameter design of the damping controller parameters; the intelligent agent in the online parameter adjustment module based on reinforcement learning simulates the "human brain" and continuously explores and summarizes the "experience and knowledge" about the system oscillation in the interaction with the system environment, thereby continuously updating the evaluation criteria of its own decision-making and correcting the corresponding strategy to achieve dynamic parameter optimization; among them, the speed regulation side damping controller of the third channel suppresses the third frequency band; the PSS damping controller of the second channel suppresses the second frequency band; the reactive damping controller of the first channel suppresses the first frequency band; the three damping controllers respectively perform online real-time design of controller parameters according to the oscillation frequency band they suppress, combined with reinforcement learning and optimization algorithms; the three channels have little influence on each other due to the differences in the adjustment time scales; The real-time online optimization design of the parameters of the three-channel multi-band oscillation damping cooperative control device relies on the online parameter adjustment module based on reinforcement learning, which is equivalent to introducing reinforcement learning into the adaptive control of the damping controller, making full use of the trial-and-error characteristics of the interaction between reinforcement learning and the environment and the ability of deep learning to process high-dimensional data, taking into account the characteristics of random changes in the steady-state operating point in the actual operation of the power system, and improving the previous "offline solution" based on deterministic working conditions, but failing to consider the problems of variable steady-state operating points of the power system caused by real-time changes in parameters in the actual power system and complex and changeable oscillation modes caused by the access of a high proportion of new energy power grids; among them, the intelligent agent first perceives the system environment of the current synchronous unit, and obtains the environmental observation quantity at the current moment according to the measurement unit. s， Then the action is performed according to the existing method network a , and updates the initial state in the environment to the state at the next moment; the agent performs actions by comparing a The reward value corresponding to the final state and the initial state r , to determine the execution a After sWhether it is trending towards a better direction, while saving the reward value after taking relevant actions; the agent continuously trains based on these reward values, accumulating its own "knowledge and experience", so that future action selections can refer to previous experience, thereby guiding the update of subsequent methods; As an optional implementation, in the embodiment of the present application, the action of the intelligent agent is to optimize and adjust the damping controller parameters of the three channels, and the reward is to use the power system stability index as prior knowledge to guide the intelligent agent training, and the optimal damping ratio can be used as the target reward; the model solving algorithm in the online parameter adjustment module based on reinforcement learning can specifically use a value function-based method, such as the Q-learning algorithm, the Deep Q-Network algorithm, etc., or a policy gradient-based method, such as the PPO algorithm, etc.

[0035] In the embodiment of the present application, in order to address the problem that the gain of the PSS damping controller may suddenly increase in the high-frequency band of oscillation, resulting in poor suppression effect on lower-frequency oscillations, the reactive damping controller directly injects reactive power into the generator end and adjusts the time block, so that the channel gain of the reactive controller can be monotonically decreased with frequency, avoiding the limitation of the high-frequency band gain on the low-frequency band damping ratio. In addition, under working conditions where unstable operation is prone to occur, such as weak system connection and high transmitted active power, the reactive damping controller has a better damping improvement capability and stable operation control capability. Therefore, the first frequency band suppressed by the reactive damping controller and the second frequency band suppressed by the PSS damping controller can be adjusted online according to the change of the system oscillation mode, that is, the frequency bands suppressed by the first channel and the second channel can be dynamically adjusted according to actual conditions, and the parameters of the reactive damping controller and the PSS damping controller can be adjusted online based on reinforcement learning, giving full play to the characteristics of the reactive damping controller in providing damping flexibly and quickly, and comprehensively enhancing the three-channel multi-band oscillation damping collaborative control device to provide better damping characteristics for the power system in a wider frequency band, thereby improving the stability performance of the power system in the entire oscillation frequency band. Specifically, when the system oscillation frequency is high, the parameters of the first and second frequency bands are adjusted according to the frequency band classification method described above. When the system oscillation frequency is low, the first frequency band can be dynamically adjusted to the 0.1-0.5 Hz frequency band, and the reactive damping controller parameters of the first channel are dynamically re-optimized. The second frequency band can be dynamically adjusted to the 0.5-2.5 Hz frequency band, and the PSS damping controller parameters of the second channel are dynamically re-optimized. Dynamically and flexibly adjusting the key operating frequency bands of the damping controllers in different channels based on monitored changes in the system oscillation mode can fully utilize the reactive damping controller's ability to flexibly and quickly provide damping, broaden the damping controller's operating frequency band, and more effectively address the complex and changing oscillation modes caused by a high proportion of renewable energy. This improves the robustness of the supplementary damping controller and enhances the stability of the power system.

[0036] Further preferably, the three-channel multi-band oscillation damping system control device is based on the collected speed deviation , power deviation , frequency deviation and excess power One or a combination of several signals in the output is used as the input signal, and the three frequency bands are adjusted respectively to generate positive damping with appropriate phases, thereby providing appropriate damping for oscillations in different frequency bands.

[0037] In general, this application has the following advantages compared with the prior art: (1) This application provides a device for three-channel coordinated suppression of multi-band oscillations in a synchronous unit. The device has three channels, wherein the first channel can quickly and flexibly provide damping to the power grid, the second channel can provide greater and more stable damping support to the power grid, and the third channel can change the input power of the unit's prime mover without participating in the change of electromagnetic power. The device has good robustness and also has the characteristics of multi-machine decoupling. It provides damping to the unit while not bringing damping to other units, thus avoiding parameter coordination and installation site selection. The three channels operate in coordination and have good robustness. They can make up for the problems of the existing additional damping controller's limited ability to suppress oscillations in the ultra-low frequency band and poor damping effect for multiple oscillation modes at the same time, and provide a wider frequency band and stronger damping.

[0038] (2) This application provides a method for collaboratively suppressing multi-band oscillations in three channels of a synchronous unit. The damping controller parameters corresponding to the three channels can be dynamically optimized online based on reinforcement learning. This method fully utilizes the trial-and-error characteristics of reinforcement learning and the environment interaction and the ability of deep learning to process high-dimensional data. It takes into account the random changes in the steady-state operating point in the actual operation of the power system. By optimizing the damping controller parameters of the three channels online through an intelligent agent, it can more effectively cope with the complex and changeable oscillation patterns of the synchronous unit system.

[0039] (3) This application provides a method for three-channel coordinated suppression of multi-band oscillations of a synchronous unit. The first frequency band corresponding to the first channel controlled by the reactive damping controller and the second frequency band corresponding to the second channel controlled by the PSS damping controller can be dynamically and flexibly adjusted according to the detected changes in the oscillation mode of the synchronous unit. This can give full play to the characteristics of the reactive damping controller that can flexibly and quickly provide damping. It can even use this characteristic to further widen the oscillation suppression frequency band, and hopefully achieve full-band oscillation suppression. In general, this application can improve the robustness of the additional damping controller, widen the working frequency band of the damping controller, and is more conducive to improving the small-disturbance stability and transient performance of the power system, improving the stability performance of the power system in the full frequency band of oscillation, and effectively dealing with the complex and changeable oscillation modes and widening of the frequency band brought about by a high proportion of new energy power grids.

[0040] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0041] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0042] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the two are connected to each other and the relative position relationship after the connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after the connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after the connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference to the directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0043] In addition, in the embodiments of the present application, the mathematical concepts mentioned include symmetry, equality, parallelism, and perpendicularity. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense. A small amount of deviation is allowed, and it is possible to be approximately symmetric, approximately equal, approximately parallel, or approximately perpendicular. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0044] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A device for three-channel coordinated suppression of multi-band oscillations in a synchronous unit, characterized in that: include: Speed regulating side damping controller, PSS damping controller and reactive damping controller; The synchronous unit includes a flexible excitation system, a prime mover, a generator, and a speed control system. The AC side of the flexible excitation system is connected to the generator terminal via a transformer in parallel to form a first channel. The reactive damping controller is used to inject reactive damping control through the first channel. The DC side of the flexible excitation system, or the output end of the excitation current circuit, is connected to the excitation winding of the generator to form a second channel. The PSS damping controller is used to indirectly provide damping control through the generator. The speed control system is connected to the generator rotor shaft through the prime mover to form a third channel. The speed control side damping controller is used to indirectly provide damping control through the prime mover. The speed regulation side damping controller, PSS damping controller and reactive damping controller are used to generate corresponding control signals according to the real-time working signals of the synchronous units, and act on the third channel, second channel and first channel respectively to generate active damping to suppress oscillations in different frequency bands; the frequency bands suppressed by the reactive damping controller and PSS damping controller can be dynamically adjusted according to the oscillation mode of the power system where the synchronous units are located.

2. The device according to claim 1, characterized in that The real-time working signal of the synchronous unit is one or a combination of speed deviation, power deviation, frequency deviation and excess power.

3. The device according to claim 1, characterized in that It also includes an online parameter adjustment module for optimizing the parameters of the reactive damping controller, the PSS damping controller, and the speed regulation side damping controller based on the frequency bands suppressed by the first channel, the second channel, and the third channel, combined with the real-time operating conditions of the power system, through the measurement unit, reward calculation, and intelligent agent; Among them, the intelligent agent action is used to optimize the parameters of the speed regulation side damping controller, PSS damping controller and reactive damping controller; the reward is to use the stability index of the synchronous unit as prior knowledge to guide the intelligent agent training, and the optimal damping ratio is used as the target reward; the selection of the intelligent agent action is calculated using the value function method or the policy gradient-based method.

4. The device according to any one of claims 1 to 3, characterized in that When the flexible excitation system is based on a voltage source type, it includes two converters. The front-stage converter is a rectifier device constructed by a voltage source converter (VSC); the rear-stage converter is a DC chopper. The AC side of the flexible excitation system is connected to the generator terminal through a transformer and connected in parallel to the generator terminal to form a first channel. The output end of the DC chopper is connected to the excitation winding of the generator to form a second channel. When the flexible excitation system is a current source-based flexible excitation system, the AC side of the flexible excitation system is connected through a transformer and connected in parallel with the generator end to form a first channel; the DC side of the flexible excitation system is connected to the excitation winding of the generator to form a second channel.

5. The device according to claim 1, characterized in that The reactive damping controller includes a first signal processing unit, a first gain unit, a first lead-lag unit and a first limiter unit; The first signal processing unit is used to use the working parameters of the synchronous unit as the input signal and filter the real-time working signal based on the suppression frequency band; the first gain unit is used to gain the signal output by the first signal processing unit and transmit it to the first lead-lag unit; the first lead-lag unit is used to correct the phase deviation of the equivalent transfer function of the first channel; the first limiting unit is used to limit the output signal of the first lead-lag unit, and the limited signal is used as the output signal.

6. The device according to claim 5, characterized in that The first signal processing unit of the reactive damping controller is a PSS2B signal processing unit, which processes the input signal to form acceleration mechanical power; or it is a speed sensor used to separate signals of each frequency band.

7. The device according to claim 1 or 5, characterized in that The PSS damping controller includes a second signal processing unit, a second lead-lag unit and a stabilizer; The second signal processing unit is a PSS2B signal processing unit or a PSS4B intermediate frequency branch signal processing unit, which is used to combine the speed deviation and the power deviation into an integral signal of the acceleration power, and transmit it to the second lead-lag unit for processing and then input to the stabilizer.

8. The device according to claim 1, characterized in that The speed regulation side damping controller includes a third signal processing unit, a third lead-lag unit, a third gain unit and a third limiting unit; the third signal processing unit is used to filter the real-time working signal based on the third channel suppression frequency band using a ramp tracking function, and to isolate the filtered signal from DC.

9. A method for collaboratively suppressing multi-band oscillations in three channels of a synchronous generator set based on the device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1: Identify the oscillation mode of the power system where the synchronous generator set is located, and divide the oscillation frequency band of the power system into a first frequency band, a second frequency band, and a third frequency band; Step S2: dynamically adjusting the first frequency band and the second frequency band suppressed by the reactive damping controller and the PSS damping controller according to the change of the power system oscillation mode; Step S3: Utilize the reactive damping controller, the PSS damping controller, and the speed regulation side damping controller to generate corresponding control signals according to the real-time working signals of the synchronous unit, and act on the first channel, the second channel, and the third channel respectively to generate active damping to suppress oscillations in the first frequency band, the second frequency band, and the third frequency band.

10. The method according to claim 9, characterized in that In step S3, the real-time operating signal of the synchronous unit is used as the input of the reactive damping controller, and the online parameter adjustment module is used to perform online dynamic optimization of the reactive damping controller parameters through the first channel. A switching signal is generated according to the generated additional damping control signal to disconnect the fully controlled devices in the flexible excitation system, and reactive power is directly injected or absorbed into the generator end to perform oscillation damping control. The real-time working signal of the synchronous unit is used as the input of the PSS damping controller. The online parameter adjustment module is used to dynamically optimize the parameters of the PSS damping controller online through the second channel, control the excitation of the excitation winding, and generate damping torque for the generator to suppress oscillation. The real-time working signal of the synchronous unit is used as the input of the speed regulation side damping controller. The online parameter adjustment module is used to perform online dynamic optimization of the speed regulation side damping controller parameters through the third channel, and an additional damping control signal is generated to control the speed governor, thereby generating a damping torque for the generator to suppress oscillation.

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