High-voltage tolerance type static synchronous phase modifier adaptive to wind and light absorption

Abstract

The invention relates to the technical field of electric energy conversion and control of an electric power system, and discloses a high-voltage tolerance type static synchronous phase modifier adaptive to wind and light absorption, which comprises a constructed network type power conversion chain used for accessing a grid-connected point of a power grid and operating as a controllable voltage source, the transient synchronous support capability not lower than three times of rated current is provided during a system fault period; an equipment internal state monitoring unit; a broadband oscillation identification unit; provided is a dynamic security boundary decision maker. According to the invention, the dominant oscillation mode in the power grid is acquired in real time and dynamically identified, and the targeted damping current instruction is generated based on the information, so that accurate and active suppression of broadband oscillation is realized, and the stability of the power grid in a complex oscillation mode is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of power system power conversion and control technology, and in particular to a high-voltage-tolerant static synchronous condenser adapted to wind and solar power consumption. Background Technology

[0002] With the acceleration of the global energy transition, the large-scale grid connection of new energy sources such as wind power and photovoltaic power has become a common trend. However, the randomness and volatility of high-proportion new energy sources, as well as the weakening of grid inertia and short-circuit capacity when connected to the grid through power electronic equipment (such as flexible DC transmission systems), pose a severe stability challenge to traditional AC grid systems. In particular, under the "weak AC-strong DC" grid connection mode, the large-scale collection and transmission channels of new energy are prone to inducing broadband oscillations, including subsynchronous oscillations and supersynchronous oscillations, which pose a huge threat to the safe and stable operation of the grid. At the same time, grid faults and fluctuations in new energy output may also lead to drastic voltage fluctuations at the grid connection point, causing an increase in transient overvoltage stress on power electronic equipment such as static synchronous condensers, accelerating the aging of equipment insulation, and even causing permanent damage.

[0003] In existing technologies, static synchronous condensers have been widely used in power grids to provide reactive power support, voltage regulation, and power fluctuation suppression. However, traditional static synchronous condensers have certain shortcomings in scenarios with a high proportion of renewable energy grid connection: First, their control strategies are usually based on fixed parameters, making it difficult to identify and suppress broadband and dynamically changing subsynchronous and supersynchronous oscillations in the power grid in real time and accurately, resulting in limited ability to suppress complex oscillation modes. Second, the equipment focuses more on rated performance during design and operation, lacking real-time collaborative perception and dynamic safety boundary management of multi-dimensional internal states such as power device junction temperature, DC bus voltage, energy storage unit status, and insulation aging. Under severe transient overvoltage and overcurrent conditions, the equipment is prone to overheating or insulation breakdown, posing a risk of shutdown due to self-protection, and challenging the reliability and lifespan of the equipment. Finally, existing solutions usually operate as independent equipment, failing to achieve deep coordination of impedance and oscillation information with the flexible DC transmission system in the same renewable energy aggregation area. This makes it impossible to reshape the impedance characteristics of the grid connection point at the system level to fundamentally avoid the resonance region, limiting the improvement of overall stability. Summary of the Invention

[0004] The technical problem to be solved by this invention is that in scenarios with a high proportion of renewable energy grid connection, static synchronous condensers mainly suffer from insufficient broadband oscillation suppression capability, lack of multi-dimensional state perception and dynamic safety boundary management, and failure to coordinate with flexible DC transmission systems to improve system stability. To address this, we propose a high-voltage-tolerant static synchronous condenser adapted to wind and solar power consumption.

[0005] To achieve the above objectives, this application adopts the following technical solution: a high-voltage-tolerant static synchronous condenser adapted for wind and solar power integration, characterized in that it comprises: The grid-connected power converter chain is used to connect to the grid and operate as a controllable voltage source, providing transient synchronization support capability of no less than three times the rated current during system faults. The equipment internal status monitoring unit includes a voltage sensor for monitoring the DC bus voltage inside the static synchronous condenser, a temperature sensor for monitoring the junction temperature or case temperature of the power semiconductor device, and a monitoring module for monitoring the status of the energy storage unit inside the static synchronous condenser. The wideband oscillation identification unit has its signal input terminal connected to the transformer at the grid connection point. It is used to collect electrical signals in real time and dynamically identify the subsynchronous and supersynchronous dominant oscillation modes in the power grid. The dynamic safety boundary decision-maker, whose input is connected to the internal status monitoring unit of the device, is used to calculate a maximum safe output current limit that dynamically changes over time based on real-time monitored voltage, temperature and energy storage status data through the fusion of electrothermal and energy models. A multi-objective cooperative controller has a first interface connected to a wideband oscillation identification unit, a second interface connected to a dynamic safety boundary decision-maker, and its output connected to a modulation module of a grid-type power converter chain. The multi-objective cooperative controller is configured to generate damping, grid-forming, and inertia support current commands based on the dominant oscillation mode information, and constrain them with the maximum safe output current limit, and then integrate them into a comprehensive current command through the optimization decision module and issue it to the grid-forming power converter chain. A wide-area collaborative interface, connected to the multi-target collaborative controller, is used to exchange impedance and dominant oscillation mode information with the flexible DC transmission system in the same new energy aggregation area.

[0006] Preferably, the broadband oscillation identification unit employs a sparse component analysis method, specifically including the following steps: a) Perform adaptive filtering on the acquired signal to suppress power frequency and specific harmonics; b) Perform recursive sparse decomposition on the filtered signal and extract the frequency, amplitude and damping ratio of each oscillation component in the range of 10Hz to 300Hz in real time with a period of 10 milliseconds. c) Cluster and evaluate the confidence of the extracted modes, and output only the dominant oscillation mode information with a confidence level higher than the threshold to the multi-objective cooperative controller.

[0007] Preferably, the dynamic safety boundary decision maker is computed by coupling the following three sub-models: The electrothermal dynamic model, based on the real-time losses of power semiconductor devices and the heat sink temperature, predicts the junction temperature change trajectory in the next tens of seconds and reverse-calculates the thermal stability current limit curve that does not trigger overheat protection. The energy storage energy management model calculates the maximum continuous output power that the energy storage unit can provide under the premise of meeting the preset transient support time requirements, based on the real-time state of charge, health status and power capability curves of the energy storage unit, and converts it into a current limit. The voltage withstand assessment model dynamically determines the recommended current output limit to avoid accelerated insulation aging caused by overvoltage stress, based on the current grid connection point voltage level and the insulation withstand characteristic curve of the stationary synchronous condenser. The dynamic safety boundary decision-maker takes the minimum value of the above three limit curves at each future time to generate the final dynamic safety current limit sequence.

[0008] Preferably, the optimization decision module in the multi-objective cooperative controller adopts a constrained model predictive control framework, which solves the optimization problem in a rolling time domain. The state-space equation of the problem includes a simplified equivalent power grid model and the dynamic model of the equipment itself. The control variable is the comprehensive current command, the primary constraint is the maximum safe output current limit, and the optimization objective is to minimize a composite performance index. This index is based on the oscillation risk characterized by the dominant oscillation mode information and the deviation term reflecting the voltage and frequency stability at the grid connection point.

[0009] Preferably, the oscillation risk term in the optimization objective is expressed by a multimodal oscillation comprehensive risk index. To quantify, this index Calculated using the following formula: ;in, The total number of dominant oscillation modes identified and output in real time by the broadband oscillation identification unit; and The first Real-time amplitude and frequency of each dominant oscillation mode; This is the base value of the rated voltage; For the first Real-time estimation of damping ratio for each dominant oscillation mode; This refers to the system's most sensitive resonant frequency, which was determined in advance through power grid impedance scanning analysis. Assign higher weights to frequency-related hazard levels for frequency bands that are prone to subsynchronous oscillations or equipment resonance. and Here is the adjustment coefficient. Preferably, the mathematical description of the rolling optimization problem solved by the optimization decision module in each control cycle is as follows: ; ;in, For prediction in the time domain; , These are the grid connection point voltage deviation and frequency deviation based on model predictions, respectively. This is an index representing the risk of oscillations at future moments based on model predictions. , , These are the weighting coefficients; The composite current command vector to be optimized; The dynamic safety boundary decision-maker generates a sequence of future time-period dynamic safety current limits. Preferably, when the energy storage unit is a supercapacitor array, the instantaneous power support current limit calculated by the energy storage energy management model... Determined by the following formula: in, ; This is the real-time DC bus voltage; This represents the maximum permissible power of the supercapacitor array; For safety factor; This represents the real-time state of charge of the supercapacitor array. The set lower limit of the state of charge; This represents the total capacitance of the supercapacitor array. This is the lowest operating voltage for the supercapacitor array; This is a preset transient support duration requirement. Preferably, the cooperative control implemented by the wide-area cooperative interface specifically includes: a) The multi-objective cooperative controller sends the key dominant oscillation mode frequency and its risk level identified locally to the flexible DC transmission system and requests the other party to return its impedance amplitude and phase characteristics near that frequency; b) Based on the impedance information of both parties, the multi-objective cooperative controller uses the admittance compensation method based on the Nyquist stability criterion to calculate and issue local additional virtual impedance adjustment commands, and at the same time sends the cooperatively optimized impedance adjustment suggestions to the other party so that the total equivalent impedance of the grid connection point avoids the unstable region at the dominant oscillation mode frequency.

[0010] Preferably, the grid-type power converter chain adopts a modular multilevel converter topology, and its bridge arm sub-modules adopt a configuration that isolates the double H-bridge from the intermediate frequency transformer; Meanwhile, the internal status monitoring unit of the equipment includes partial discharge sensors distributed in each bridge arm submodule. The dynamic safety boundary decision-maker adaptively tightens the insulation aging factor in the voltage withstand assessment model based on the characteristic change trend of the partial discharge signal, thereby preventing the current output limit from being reduced in advance.

[0011] Preferably, it also includes a preventive protection module integrated in the multi-objective cooperative controller. The preventive protection module continuously monitors the rate of decrease of the maximum safe output current limit output by the dynamic safety boundary decision-maker and the communication delay of the wide-area cooperative interface. When it detects that the limit is decaying rapidly and the communication delay is too large, it automatically switches the control mode from the cooperative optimization mode to the local conservative defense mode. In this mode, some performance optimization objectives are ignored, and the local safety of the equipment and the basic support of the power grid are prioritized to the greatest extent.

[0012] The technical effects and advantages of this invention are as follows: In this invention, firstly, by real-time acquisition and dynamic identification of the dominant oscillation mode in the power grid, and generating targeted damping current commands based on this information, precise and proactive suppression of broadband oscillations is achieved, significantly improving the stability of the power grid under complex oscillation modes. Secondly, by real-time monitoring of multi-dimensional internal parameters such as junction temperature, DC voltage, energy storage status, and insulation status of power devices, and by dynamically calculating the safe current boundary using electrothermal, energy, and voltage withstand models, the synchronous condenser can adaptively optimize its output while strictly ensuring its own safety, greatly improving the operational reliability and service life of the equipment under severe transient conditions. Thirdly, by real-time interaction and coordinated adjustment of impedance and oscillation information with the flexible DC transmission system in the same renewable energy aggregation area, the impedance characteristics of the grid connection point are reshaped at the system level, jointly suppressing broadband oscillations and improving the overall stability of the transmission channel. Attached Figure Description

[0013] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is a schematic diagram illustrating the system flow principle of the present invention. Detailed Implementation

[0014] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0015] Reference Figure 1 As shown, the present invention provides a technical solution: a high-voltage withstand type static synchronous condenser adapted to wind and solar power integration, the system architecture of which includes a grid-type power converter chain, an internal equipment status monitoring unit, a wideband oscillation identification unit, a dynamic safety boundary decision-maker, a multi-objective cooperative controller, and a wide-area cooperative interface.

[0016] Grid-based power converter chain: The grid-based power converter chain is the foundation for the entire static synchronous condenser to achieve power conversion, connect to the grid, and operate as a controllable voltage source. In this embodiment, the grid-based power converter chain can adopt a topology based on a modular multilevel converter (MMC). This MMC topology has advantages such as modularity, high voltage level, excellent harmonic performance, and fault ride-through capability, making it suitable for high-voltage, high-capacity grid-connected scenarios. Its rated capacity can be set to ±35Mvar, and the rated voltage is 37kV. To further improve the grid-based power converter chain... The transient support capability and DC fault ride-through capability of the power converter chain are enhanced by the fact that its internal bridge arm sub-modules can adopt a configuration that isolates them from the intermediate frequency transformer using a double H-bridge design. This design can effectively improve the voltage withstand capability of the sub-modules, reduce device stress, and provide multiple fault isolation paths, thereby enhancing the robustness of the entire system. The grid-type power converter chain has the ability to provide transient synchronous support capability of no less than 3 times the rated current during system faults. Thus, when the grid is subjected to severe disturbances, it can quickly respond and inject large current to stabilize the grid connection point voltage, maintain synchronous operation of the system, and avoid instability.

[0017] Internal Equipment Status Monitoring Unit: This unit monitors key operating parameters within the stationary synchronous condenser in real time, providing fundamental data for the dynamic safety boundary decision-maker. It includes various sensors and monitoring modules: Voltage sensors are primarily used for real-time monitoring of the DC bus voltage. For example, high-precision voltage transformers or resistive voltage dividers are installed on the high-voltage DC bus, with a sampling frequency of at least 10kHz to capture transient voltage changes. Temperature sensors monitor the junction or case temperature of power semiconductor devices. This can be achieved by installing PT100 platinum resistance thermometers, thermistors, or fiber optic temperature sensors on the heat sink of the IGBT power module, or by estimating the junction temperature through an online loss model. By directly measuring the case temperature and combining it with the thermal resistance characteristics of the semiconductor chip, it is possible to... To more accurately determine the actual operating temperature of the device, so as to adjust the operating strategy in a timely manner and prevent overheating; the monitoring module is used to monitor the status of the energy storage units inside the device, such as the status of the supercapacitor array; if the grid-type power converter chain is equipped with energy storage units, the monitoring module will collect data such as the total voltage of the energy storage units, the voltage, current and temperature of each series and parallel module in real time, and accurately calculate the real-time state of charge and health status of the energy storage units based on these data, providing accurate input for the energy storage energy management model; furthermore, in a preferred embodiment, the internal status monitoring unit of the device also includes partial discharge sensors distributed in each bridge arm sub-module, which are used to monitor the partial discharge activity of the insulation material of the sub-module in real time, thereby providing early warning of insulation aging or damage. Wideband Oscillation Identification Unit: The wideband oscillation identification unit is used to acquire electrical signals at the grid connection point in real time and dynamically identify all subsynchronous and supersynchronous dominant oscillation modes in the grid. Its implementation steps are as follows: First, acquire the voltage or current signal of the grid through the transformer at the grid connection point; Second, perform adaptive filtering on the acquired signal to suppress power frequency and specific harmonics; for example, use an adaptive notch filter or extended Kalman filter to filter out the 50Hz power frequency fundamental wave and any possible major integer harmonics from the original signal to avoid these strong components interfering with the identification of oscillation modes; Third, perform recursive sparse decomposition on the filtered signal. This step extracts the frequency of each oscillation component within the range of 10Hz to 300Hz in real time with a period of, for example, 10 milliseconds. Amplitude and damping ratio Recursive sparse decomposition, a signal processing technique, can separate multiple independent oscillation components from complex signals by continuously updating the sparse dictionary, even if the frequencies of these components are very close. The 10-millisecond cycle ensures rapid response and dynamic tracking of power grid oscillations. The fourth step involves clustering and confidence assessment of the extracted modes. Within multiple consecutive 10-millisecond cycles, cluster analysis is performed on the identified oscillation modes to eliminate random noise or transient disturbances. Confidence assessment, based on factors such as mode duration, amplitude stability, and comparison with historical data, ensures the reliability of the identification results. Only when the confidence of a mode exceeds a preset threshold, for example, if it is identified and its amplitude is stable within five consecutive cycles, is the mode confirmed as "dominant oscillation mode information" and output to the multi-objective cooperative controller. This screening mechanism ensures that the oscillation information transmitted to the controller is real and continuous, avoiding malfunctions caused by false information. The dominant oscillation mode information includes, but is not limited to, its frequency, amplitude, and damping ratio.

[0018] Dynamic safety boundary decision unit: The dynamic safety boundary decision unit is a component that ensures the safe operation of the static synchronous condenser. Its input is connected to the internal status monitoring unit of the equipment. Based on real-time monitored voltage, temperature, and energy storage status data, it calculates a maximum safe output current limit that dynamically changes over time by fusing electrothermal and energy models. The dynamic safety boundary decision-maker performs calculations by coupling the following three sub-models: First, the electrothermal dynamic model: based on the real-time losses of the power semiconductor device (calculated through the output current, DC voltage, and switching frequency of the grid-type power converter chain) and the heat sink temperature (monitored by a temperature sensor), it predicts the junction temperature change trajectory over the next tens of seconds. This prediction can be achieved by fusing the thermal network model with a Kalman filter to accurately predict the junction temperature of the hottest spot in the IGBT. Then, it reverse-engineers the thermal stability current limit curve that meets the maximum allowable junction temperature of the device without triggering overheat protection. Secondly, there is the energy storage management model: when a grid-type power converter chain is equipped with energy storage units (such as supercapacitor arrays), this model calculates the maximum continuous output power that the energy storage units can provide under the preset transient support time requirements, based on the real-time state of charge, health status, and power capability curves (considering internal resistance and temperature effects). and convert it into the corresponding current limit value. Specifically, when the energy storage unit is a supercapacitor array, the instantaneous power support current limit calculated by the energy storage energy management model... Determined by the following formula: in, The real-time DC bus voltage is monitored by a voltage sensor; The maximum effective power that a supercapacitor array can provide is calculated using the following formula: ;in This represents the maximum permissible power of the supercapacitor array; The safety factor is used to reserve a certain safety margin in calculations; The real-time state of charge of the supercapacitor array is provided by the monitoring module; The safe lower limit of the state of charge is set for the supercapacitor array; it is not recommended to continue discharging below this state. This represents the total capacitance of the supercapacitor array. This is the lowest operating voltage for the supercapacitor array; The system includes a preset transient support duration requirement, such as ensuring a transient current output for 10 seconds during grid faults; and finally, a voltage withstand assessment model. This model dynamically determines the recommended current output limit to avoid accelerated insulation aging caused by overvoltage stress, based on the current grid connection voltage level (collected by the grid connection voltage transformer) and the equipment's insulation withstand characteristic curve (Vt characteristic curve, which describes the lifespan of the insulation material under different voltage stresses). When the grid connection point voltage is too high, the model will provide a more conservative current output limit to protect the insulation life of the equipment. Furthermore, when the partial discharge sensor in the equipment's internal condition monitoring unit detects an upward trend in the characteristic changes of the partial discharge signal, it indicates that the insulation may be deteriorating rapidly. Based on this, the dynamic safety boundary decision-maker adaptively tightens the insulation aging factor in the voltage withstand assessment model, thereby proactively reducing the current output limit and further enhancing the equipment's safety margin under insulation damage conditions. The dynamic safety boundary decision-maker uses the above three limit curves... , and Take the minimum value at each future moment, that is This generates the final time-varying dynamic safety current limit sequence. The multi-objective cooperative controller is the intelligent decision-making center of the stationary synchronous condenser. Its first interface connects to the broadband oscillation identification unit to receive dominant oscillation mode information; its second interface connects to the dynamic safety boundary decision-maker to obtain the maximum safe output current limit; its output connects to the modulation module of the grid-type power converter chain, such as a PWM modulator, to issue comprehensive current commands. The multi-objective cooperative controller is configured to: generate damping current commands based on the dominant oscillation mode information (including frequency, amplitude, damping ratio, etc.), and generate grid support current commands (used to maintain grid connection point voltage stability) and inertia support current commands (used to provide virtual inertia and suppress frequency changes) in conjunction with grid requirements; when generating these commands, the controller uses the maximum safe output current limit... As a rigid constraint, it is fused through the built-in optimization decision module to generate a comprehensive current command. The control is issued to the grid-type power converter chain; the optimization decision module adopts a constrained model predictive control framework, which solves the optimization problem in a rolling time domain. The state-space equation of this problem includes a simplified equivalent grid model (node ​​voltage, system frequency) and the dynamic model of the equipment itself (DC voltage, AC current loop); the control variable is the comprehensive current command. The primary constraint is the maximum safe output current limit. To predict time variables in the time domain, its physical meaning is... (Same as above), ensuring that the commanded current does not exceed the equipment safety boundary under any circumstances; the optimization objective is to minimize the composite index consisting of oscillation risk, voltage deviation, and frequency deviation; specifically, the index used to quantify broadband oscillation risk in the optimization objective is calculated by the following formula: in, The total number of dominant oscillation modes identified and output in real time by the broadband oscillation identification unit; and The first The real-time amplitude and frequency of each dominant oscillation mode are based on the rated voltage base value and used for amplitude normalization. This is the base value of the rated voltage; For the first Real-time estimation of damping ratio for each dominant oscillation mode; The most sensitive resonant frequency of the system, which is determined in advance through power grid impedance scanning analysis, is usually the key frequency that causes subsynchronous or supersynchronous oscillations. As a frequency-related hazard level weighting coefficient, higher weights are assigned to frequency bands (15-40Hz subsynchronous frequency range) that are prone to causing subsynchronous oscillations or equipment resonance. and This is an adjustment coefficient used to adjust the sensitivity of the indicator and prevent the denominator from being zero. The mathematical description of the rolling optimization problem solved by the optimization decision module in each control cycle is as follows: ; in, To predict the time domain, such as 200 milliseconds, ensure that the controller can anticipate and respond to impending oscillations; , These are the grid connection point voltage deviation and frequency deviation, respectively, based on model predictions, used to ensure basic voltage and frequency support functions. For future moments predicted by the model The oscillation risk index is calculated in the same way as the aforementioned real-time oscillation risk indicator. The same, but the input is the system state quantity in the prediction time domain; , , These are weighting coefficients used to balance the relative importance of various optimization objectives; for example, increasing them when the risk of oscillation is high. The weights; The composite current command vector to be optimized; A sequence of dynamic safety current limits for future time periods is generated for the dynamic safety boundary decision-maker. Wide-area cooperative interface: The wide-area cooperative interface connects to a multi-objective cooperative controller for interacting with the flexible DC transmission system in the same renewable energy aggregation area to exchange impedance and dominant oscillation mode information. This cooperative control aims to fundamentally eliminate broadband oscillation risks at the system level. Specifically, the cooperative control implemented by the wide-area cooperative interface involves the multi-objective cooperative controller sending the locally identified key dominant oscillation mode frequencies and their risk levels to the flexible DC transmission system via the wide-area cooperative interface. Simultaneously, the local static synchronous condenser requests the flexible DC transmission system to return its impedance amplitude and phase characteristics near that frequency. Upon receiving the impedance information from the flexible DC transmission system, the multi-objective cooperative controller combines this with the local static synchronous condenser's own dynamic impedance... Based on the background grid impedance of the grid connection point, an admittance compensation method based on the Nyquist stability criterion is used to calculate the target equivalent impedance that enables the grid connection point to be in a stable region at the dominant oscillation mode frequency. According to the calculation results, the local static synchronous condenser calculates and sends the required virtual impedance adjustment command to the modulation module to change its own equivalent impedance at a specific frequency. At the same time, it sends the optimized impedance adjustment suggestion to the flexible DC transmission system through the wide-area cooperative interface to guide the flexible DC transmission system to perform corresponding impedance compensation. The ultimate goal of the cooperation is to make the total equivalent impedance of the grid connection point avoid the unstable region at the dominant oscillation mode frequency, thereby suppressing or eliminating broadband oscillations from the root.

[0019] Preventive Protection Module: A preventive protection module is also integrated into the multi-objective cooperative controller. This module continuously monitors the rate of decrease of the maximum safe output current limit output by the dynamic safety boundary decision-maker and the communication delay of the wide-area cooperative interface. When the module detects a rapid decline in the device's internal condition (severe overheating, accelerated insulation aging, or energy depletion) and excessive communication delay or even communication interruption of the wide-area cooperative interface, the system determines that it may be in an emergency or unfavorable cooperative operating condition. In this case, the preventive protection module automatically and seamlessly switches the control mode of the multi-objective cooperative controller from a cooperative optimization mode that pursues multi-objective optimization to a local conservative defense mode. In this mode, the multi-objective cooperative controller temporarily ignores some performance optimization objectives (e.g., reducing the target weight of oscillation damping, resulting in a weight decrease) to prioritize ensuring the local safety of the device and the basic support of the power grid (such as maintaining stable voltage at the grid connection point). This preventive protection mechanism ensures that in extreme or uncertain environments, the device can prioritize self-protection and provide basic support, avoiding system collapse caused by excessive pursuit of performance optimization or communication limitations.

[0020] The working principle of this invention is as follows: a grid-type power converter chain is used as a controllable voltage source connected to the power grid to provide synchronous voltage support and dynamic reactive power compensation. The internal status monitoring unit, broadband oscillation identification unit, and dynamic safety boundary decision-maker of the equipment work together to collect key internal status parameters of the equipment in real time, accurately identify broadband oscillation modes of the power grid, and calculate the dynamic safety operation boundary by integrating multi-source information. The multi-objective collaborative controller serves as the core decision-making unit. Under the premise of simultaneously accepting the stability requirements of the power grid and the safety boundary constraints of the equipment itself, it generates the globally optimal comprehensive current command through online optimization algorithm and sends it to the power converter chain for execution. The wide-area collaborative interface further expands the system control capability of the equipment. By exchanging information and coordinating control with external systems such as flexible DC transmission, broadband oscillations are suppressed from the global level of the power grid.

[0021] The beneficial effects achieved by this invention lie in the deep integration and synergistic optimization of the grid's active support function and the equipment's own safety protection mechanism, providing a systematic solution to address the stability challenges brought about by a high proportion of new energy grid connection. Specifically, this is manifested in: ensuring the operational safety and long-term reliability of equipment under harsh conditions such as transient overvoltage and high current support through real-time dynamic safety boundary management; effectively suppressing subsynchronous and supersynchronous oscillations and improving the stability of the local grid through accurate identification and multi-objective synergistic optimization control of wide-frequency oscillations; enhancing the overall robustness of the new energy aggregation and transmission system under complex oscillation conditions through wide-area synergistic control capabilities; and further enhancing the system's built-in preventive protection mechanism to maintain basic equipment safety and grid support under extreme or abnormal conditions, achieving dual protection for grid and equipment safety.

[0022] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A high-voltage-tolerant static synchronous condenser adapted for wind and solar energy absorption, characterized in that, include: The grid-connected power converter chain is used to connect to the grid and operate as a controllable voltage source, providing transient synchronization support capability of no less than three times the rated current during system faults. The equipment internal status monitoring unit includes a voltage sensor for monitoring the DC bus voltage inside the static synchronous condenser, a temperature sensor for monitoring the junction temperature or case temperature of the power semiconductor device, and a monitoring module for monitoring the status of the energy storage unit inside the static synchronous condenser. The wideband oscillation identification unit has its signal input terminal connected to the transformer at the grid connection point. It is used to collect electrical signals in real time and dynamically identify the subsynchronous and supersynchronous dominant oscillation modes in the power grid. The dynamic safety boundary decision-maker, whose input is connected to the internal status monitoring unit of the device, is used to calculate a maximum safe output current limit that dynamically changes over time based on real-time monitored voltage, temperature and energy storage status data through the fusion of electrothermal and energy models. A multi-objective cooperative controller has a first interface connected to a wideband oscillation identification unit, a second interface connected to a dynamic safety boundary decision-maker, and its output connected to a modulation module of a grid-type power converter chain. The multi-objective cooperative controller is configured to generate damping, grid-forming, and inertia support current commands based on the dominant oscillation mode information, and constrain them with the maximum safe output current limit, and then integrate them into a comprehensive current command through the optimization decision module and issue it to the grid-forming power converter chain. A wide-area collaborative interface, connected to the multi-target collaborative controller, is used to exchange impedance and dominant oscillation mode information with the flexible DC transmission system in the same new energy aggregation area.

2. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 1, characterized in that: The broadband oscillation identification unit employs a sparse component analysis method, specifically including the following steps: a) Perform adaptive filtering on the acquired signal to suppress power frequency and specific harmonics; b) Perform recursive sparse decomposition on the filtered signal and extract the frequency, amplitude and damping ratio of each oscillation component in the range of 10Hz to 300Hz in real time with a period of 10 milliseconds. c) Cluster and evaluate the confidence of the extracted modes, and output only the dominant oscillation mode information with a confidence level higher than the threshold to the multi-objective cooperative controller.

3. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 1, characterized in that: The dynamic safety boundary decision-maker is computed by coupling the following three sub-models: The electrothermal dynamic model, based on the real-time losses of power semiconductor devices and the heat sink temperature, predicts the junction temperature change trajectory in the next tens of seconds and reverse-calculates the thermal stability current limit curve that does not trigger overheat protection. The energy storage energy management model calculates the maximum continuous output power that the energy storage unit can provide under the premise of meeting the preset transient support time requirements, based on the real-time state of charge, health status and power capability curves of the energy storage unit, and converts it into a current limit. The voltage withstand assessment model dynamically determines the recommended current output limit to avoid accelerated insulation aging caused by overvoltage stress, based on the current grid connection point voltage level and the insulation withstand characteristic curve of the stationary synchronous condenser. The dynamic safety boundary decision-maker takes the minimum value of the above three limit curves at each future time to generate the final dynamic safety current limit sequence.

4. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 1, characterized in that: The optimization decision module in the multi-objective cooperative controller adopts a constrained model predictive control framework, which solves the optimization problem in a rolling time domain. The state-space equation of the problem includes a simplified equivalent power grid model and the dynamic model of the equipment itself. The control variable is the comprehensive current command, and the primary constraint is the maximum safe output current limit. The optimization objective is to minimize a composite performance index, which is based on the oscillation risk characterized by the dominant oscillation mode information and the deviation term reflecting the voltage and frequency stability at the grid connection point.

5. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 4, characterized in that: The oscillation risk term in the optimization objective is expressed by a multimodal oscillation comprehensive risk index. To quantify, this index Calculated using the following formula: in, The total number of dominant oscillation modes identified and output in real time by the broadband oscillation identification unit; and The first Real-time amplitude and frequency of each dominant oscillation mode; This is the base value of the rated voltage; For the first Real-time estimation of damping ratio for each dominant oscillation mode; This refers to the system's most sensitive resonant frequency, which was determined in advance through power grid impedance scanning analysis. Assign higher weights to frequency-related hazard levels for frequency bands that are prone to subsynchronous oscillations or equipment resonance. and This is the adjustment coefficient.

6. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 5, characterized in that: The mathematical description of the rolling optimization problem solved by the optimization decision module in each control cycle is as follows: ; ;in, For prediction in the time domain; , These are the grid connection point voltage deviation and frequency deviation based on model predictions, respectively. This is an index representing the risk of oscillations at future moments based on model predictions. , , is the weighting coefficient; is the comprehensive current command vector to be optimized; The future time period dynamic safety current limit sequence generated for the dynamic safety boundary decision-maker.

7. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 3, characterized in that: When the energy storage unit is a supercapacitor array, the instantaneous power support current limit calculated by the energy storage energy management model. Determined by the following formula: in, ; This is the real-time DC bus voltage; This represents the maximum permissible power of the supercapacitor array; For safety factor; This represents the real-time state of charge of the supercapacitor array. The set lower limit of the state of charge; This represents the total capacitance of the supercapacitor array. Minimum operating voltage of supercapacitor array; This is the preset transient support duration requirement.

8. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 1, characterized in that: The cooperative control implemented by the wide-area cooperative interface is as follows: a) The multi-objective cooperative controller sends the locally identified key dominant oscillation mode frequency and its risk level to the flexible DC transmission system, and requests the other party to return its impedance amplitude and phase characteristics near that frequency; b) Based on the impedance information of both parties, the multi-objective cooperative controller uses the admittance compensation method based on the Nyquist stability criterion to calculate and issue the locally added virtual impedance adjustment command, and at the same time sends the cooperatively optimized impedance adjustment suggestion to the other party so that the total equivalent impedance of the grid connection point avoids the unstable region at the dominant oscillation mode frequency.

9. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption as described in claim 3, characterized in that: The grid-type power converter chain adopts a modular multilevel converter topology, and its bridge arm sub-module adopts a configuration that isolates the double H-bridge from the intermediate frequency transformer. Meanwhile, the internal status monitoring unit of the equipment includes partial discharge sensors distributed in each bridge arm submodule. The dynamic safety boundary decision-maker adaptively tightens the insulation aging factor in the voltage withstand assessment model based on the characteristic change trend of the partial discharge signal, thereby preventing the current output limit from being reduced in advance.

10. The high-voltage withstand type stationary synchronous condenser adapted for wind and solar power consumption according to claim 1, characterized in that: It also includes a preventive protection module integrated into the multi-objective cooperative controller. The preventive protection module continuously monitors the rate of decrease of the maximum safe output current limit output by the dynamic safety boundary decision-maker and the communication delay of the wide-area cooperative interface. When it detects that the limit is decaying rapidly and the communication delay is too large, it automatically switches the control mode from the cooperative optimization mode to the local conservative defense mode. In this mode, some performance optimization objectives are ignored, and the local safety of the equipment and the basic support of the power grid are prioritized to the greatest extent.

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