18 results about "Nyquist stability criterion" patented technology

The invention discloses a harmonic stability evaluation method, device and equipment applied to a renewable energy power system and a medium, the method is applied to the technical field of power system harmonic, and the method comprises the steps: carrying out the impedance aggregation processing of topological structure data, and obtaining a harmonic impedance model; processing the renewable energy equipment data based on a Nyquist stability criterion to obtain a stability boundary condition of the power system; constructing a node admittance matrix based on the harmonic impedance model and the stability boundary condition; processing the node admittance matrix by using a Fourier technology to obtain impedance spectrum data, and processing the impedance spectrum data based on a modal impedance maximum value analysis method to obtain resonance modal characteristics; processing the resonance mode characteristics and the real-time operation condition to obtain a time domain verification result; and carrying out harmonic stability evaluation based on a time domain verification result. According to the method provided by the invention, the technical problem of harmonic stability evaluation distortion caused by incomplete measurement data can be solved.

The invention relates to the technical field of power systems, and discloses a multi-level direct current sending end small disturbance stability assessment method, device and equipment and a medium. Carrying out frequency domain impedance modeling on the following network type new energy converter, the constructed network type energy storage converter, the following network type load converter and the modularized multi-level high-voltage direct current converter station, and constructing a frequency domain impedance network of the all-electric system based on an equivalent impedance model of each device; and performing small disturbance stability analysis on the frequency domain impedance network by using a generalized Nyquist stability criterion, and determining the small disturbance stability of the all-electric system in an alternating current and direct current hybrid scene through a Nyquist diagram of impedance ratios of two sides of a voltage source and a current source in the frequency domain impedance network. Therefore, an effective evaluation means is provided for stable operation of the alternating-current and direct-current series-parallel all-electric system.

The invention relates to the field of power systems, in particular to a multi-power-supply system broadband oscillation risk testing and evaluating method. The method comprises the following steps: accessing a new energy physical controller to a semi-physical simulation platform, injecting a sweep frequency voltage disturbance signal, and collecting the signal to generate a semi-physical three-dimensional impedance matrix; constructing a corresponding single-machine electromagnetic model in electromagnetic transient simulation software, and injecting sweep-frequency voltage disturbance to generate a single-machine impedance characteristic curve; comparing the two, and correcting electromagnetic model control parameters according to a deviation frequency band; and finally, combining the corrected models and the like, injecting a sweep frequency disturbance signal at a grid-connected point, obtaining impedance, and evaluating the oscillation risk according to a Nyquist stability criterion. According to the method, a semi-physical simulation platform and electromagnetic transient simulation software are combined, impedance scanning is carried out on a physical controller, comparison verification and parameter correction are carried out on the physical controller and an electromagnetic model, the problem of large difference between the model and an actual system is effectively solved, and the accuracy and reliability of broadband oscillation risk assessment are remarkably improved.

The invention provides a high-stability control method for a power grid simulator, and the method comprises the steps: embedding a virtual impedance feature Zvirref (s) in an integral controller of a voltage controller module, and forming a controller structure of Ki * Zvirref (s) / s; and dynamically adjusting the integral gain Ki according to the virtual impedance generated by the power grid simulator and the physical impedance provided by the impedance network B so as to meet the condition that the amplitude of the virtual impedance is not higher than the amplitude of the physical impedance in the frequency range in which the virtual impedance is presented to be non-passive. Decoupling between internal control dynamic and virtual impedance characteristics of the power grid simulator is realized, and the self-stability of the power grid simulator under different impedance simulation conditions is ensured; the self-adaptive adjustment of the closed-loop transfer function of the power grid simulator is realized, the virtual impedance and the physical impedance are ensured to meet the Nyquist stability criterion, and the interaction stability between the power grid simulator and the tested object is improved.

The invention belongs to the field of airborne power system design, and particularly relates to a stability constraint method for an MEA variable-frequency alternating-current power system. The method comprises the following steps: firstly, establishing a port impedance / admittance model of each device in a system; secondly, analyzing the stability of each subsystem, and redesigning if the stability margin does not meet the requirement; then, on the premise that all subsystems are stable, the overall stability of the system is analyzed according to a generalized Nyquist stability criterion; if the whole system is unstable or underdamped, quantitatively identifying a high-influence negative subsystem with the maximum stability deterioration degree in a mode of setting admittance of a load-side subsystem to be zero; and finally, the stability margin of the high-influence negative subsystem is improved by redesigning the high-influence negative subsystem. The MEA variable-frequency alternating-current power system is ensured to have enough stability margin in the design stage, so that the stability problem is avoided.

The present invention proposes a method for generating chatter-free tool axis vectors for five-axis ball-end tool machining. First, representative tool axis vectors are determined at critical tool locations based on the Nyquist stability criterion to construct a critical tool axis vector set. Then, a four-element vector interpolation algorithm is used to interpolate the critical tool axis vector set within a general region to generate smooth tool axis vectors. The machining stability of each tool location is then checked. If chatter occurs, the steepest descent method is used at the tool location where chatter occurs to determine the chatter-free tool axis vector with the smallest angular change from the original tool axis vector. These chatter-free tool axis vectors are then added to the critical tool axis vector set. New tool axis vectors are then interpolated based on the critical tool axis vector set. This process is repeated until the tool axis vectors at all tool locations pass the cutting stability check. The present invention can generate a smooth and chatter-free tool path along the tool path, effectively suppressing cutting vibration during multi-axis machining.

The present application relates to the technical field of power system, discloses a kind of multi-level DC sending end small signal stability evaluation method, device, equipment and medium, the present application considers the coupling influence between different heterogeneous devices, to network type new energy converter, network type energy storage converter, network type load converter and modular multi-level high voltage direct current converter station are carried out frequency domain impedance modeling, and based on the equivalent impedance model of each device, the frequency domain impedance network of all-electric system is constructed, the small signal stability of frequency domain impedance network is analyzed using generalized Nyquist stability criterion, the Nyquist diagram of impedance ratio on the two sides of voltage source and current source in frequency domain impedance network is determined The small signal stability of all-electric system under AC / DC hybrid scene, so as to provide an effective evaluation means for the stable operation of AC / DC hybrid all-electric system.

A stability detection method and system for grid-connected and grid-connected converters based on impedance modeling is proposed. This method determines the impedance matrix of the voltage source inverter based on a small-signal model of the voltage source inverter, and establishes a first impedance ratio, a second impedance ratio, and a third impedance ratio with the equivalent impedance matrix of the power grid. If the first impedance ratio does not satisfy the Nyquist stability criterion, the converter is determined to be in a negatively damped state; if the first impedance ratio satisfies the Nyquist stability criterion, the converter is determined to be in a positively damped or underdamped state. The product of the second and third impedance ratios is used as the oscillation damping coefficient. If the oscillation damping coefficient is less than zero, the converter is determined to be in a negatively damped stable state; if the oscillation damping coefficient is greater than or equal to zero and less than the critical damping coefficient, the converter is determined to be in an underdamped stable state; if the oscillation damping coefficient is greater than or equal to the critical damping coefficient, the converter is determined to be in a positively damped stable state. This method accurately describes the dynamic characteristics of the converter under nonlinear and large disturbance conditions.

The invention discloses a grid-connected converter parameter domain construction method based on an interactive coupling effect, and relates to the technical field of power system control, and the method comprises the steps: building a small signal model according to a topological circuit and a control structure of a grid-connected converter, and obtaining a system open-loop transfer function through the small signal model; deducing a security domain upper boundary and a security domain lower boundary of a first control bandwidth ratio according to a system open-loop transfer function and a Nyquist stability criterion so as to determine a control bandwidth ratio security domain, and mapping the control bandwidth ratio security domain into a security domain of a proportionality coefficient and an integral coefficient of a DC voltage controller; and determining a constraint relationship between the second control bandwidth ratio and a steady-state output power limit value of the grid-connected converter to obtain an operation parameter feasible region, and constructing a multi-dimensional parameter feasible region for guiding parameter design of the grid-connected converter. According to the invention, the parameter domain of the grid-connected converter can be accurately constructed, guidance is provided for parameter adjustment, and stable operation of a power system can be maintained.

This invention discloses an intelligent collaborative control method and system for industrial equipment based on the Internet, belonging to the technical field of intelligent control. The method includes the following steps: Step S1, determining whether the control time deviation of the equipment is fixed; Step S2, setting a first cooling priority, setting open-loop control parameters for the valve opening time, and controlling the equipment according to the open-loop control parameters; Step S3, setting closed-loop control parameters for the valve opening time, and compensating the equipment according to the closed-loop control parameters. This invention adopts an open-loop control mode, pre-calculating the duty cycle sequence based on a feedforward compensation mechanism, improving the system's response speed and reducing the real-time calculation burden. When the control time deviation is not fixed, a control mode combining open-loop and closed-loop control is adopted, enhancing the system's robustness to parameter drift and external disturbances. The Nyquist stability criterion is introduced to verify the closed-loop control parameters online, achieving a balanced optimization of control performance and stability margin.

The invention provides an energy storage state-of-charge balance secondary control method based on security reinforcement learning, which comprises the following steps: constructing a state space, an action space and a reward function, establishing a strategy network and a value network, designing an action space constraint mechanism through a Nyquist stability criterion to meet the stability requirement of a system, and obtaining a control strategy by utilizing reinforcement learning interaction training, and deploying the control strategy in the system to realize online control. According to the method, the depth deterministic strategy gradient agent is constructed, the control action is generated in combination with the real-time operation state information of the system, the control target is to quickly realize the charge state dynamic balance and the system frequency stability between the energy storage devices, accurate modeling of a secondary controller is not needed, and the method has good adaptability and generalization ability and is suitable for large-scale popularization and application. The method can effectively improve the energy storage operation efficiency and safety, and is suitable for the adaptive coordination control of the energy storage charge state in various new energy power systems.

The invention belongs to the technical field of electrical engineering, and discloses a high-frequency resonance suppression method for a grid-forming type SLCC converter valve containing CLC amplitude limiting, and the method comprises the steps: constructing a double-6-pulse grid-forming type SLCC converter valve topology model, and constructing a grid-following type SVG sequence impedance model, a grid-forming type SVG sequence impedance model and a double-6-pulse LCC converter station admittance model according to the double-6-pulse grid-forming type SLCC converter valve topology model; establishing an equivalent impedance circuit model for the following network type SVG sequence impedance model and the constructed network type SVG sequence impedance model by utilizing a Nyquist stability criterion based on an impedance analysis method, and judging the stability of a corresponding system; and based on a stability discrimination result, adjusting a VSG parameter and a CLC amplitude limiting coefficient to complete high-frequency resonance suppression. According to the method, autonomous voltage building and frequency modulation of the network-building type SLCC are realized, and the method is suitable for a weak power grid scene with high-proportion new energy access.

A new energy base oscillation risk multi-port screening method, system and related device, the method comprising: collecting basic data of a new energy base, the basic data of the new energy base comprising an impedance data set of a new energy unit, a grid structure and parameters of a new energy grid-connected system, and an operation mode of the new energy grid-connected system; obtaining a multi-port equivalent model of the new energy base by using the basic data of the new energy base through vector fitting, impedance aggregation and a multi-port model generation process; the oscillation risk of the multi-port equivalent model of the new energy base is evaluated by using a Nyquist stability criterion, and the oscillation risk at each port is quantitatively screened by using a damping ratio index. The improved stability judgment method considering the right half plane pole is provided based on the Nyquist stability criterion, the influence of the right half plane pole of the open-loop transfer function on stability judgment can be avoided, and accurate positioning of the oscillation dominant field station can be achieved by adopting the damping ratio index.

The invention belongs to the field of power supply and dispatching, and provides a follow-up network energy storage capacity proportioning method considering frequency and voltage stability, which considers the mapping performance of a small interference model of a follow-up network hybrid system in voltage and frequency stability at the same time, and establishes frequency domain small signal models for a follow-up network type unit and a network type unit respectively. Transfer function expressions of respective impedance and power frequency response are obtained, and the transfer function expressions correspond to two aspects of voltage and frequency; the method comprises the following steps: respectively establishing a network tracking / constructing multi-machine parallel network model, calculating network tracking / constructing capacity matching ranges of voltage and frequency small interference stability requirements in different grid-connected scenes based on a generalized Nyquist stability criterion according to indexes such as an equivalent short-circuit ratio, and taking an intersection of the network tracking / constructing capacity matching ranges to obtain an overall matching boundary; on this basis, the influence caused by actual errors is considered, a certain margin is reserved for the matching, and meanwhile, the matching influence is analyzed based on a sensitivity function, so that the stability of the tracking / networking energy storage hybrid grid connection is improved.

The application discloses a kind of method and system for determining the reason of high-frequency oscillation of flexible direct current transmission system, method is suitable for when at least two converter units are operated in parallel, high-frequency oscillation is generated in flexible direct current system, comprising: establishing the impedance model of converter, obtaining the impedance Z MMC Of converter;Establish the impedance model of alternating current power grid, obtain the impedance Z g Of alternating current power grid;Based on Nyquist stability criterion, the phase difference of alternating current power grid impedance and converter impedance Z MMC Z g The absolute value of ratio is equal to 1 at the frequency point, the absolute value |∠Z MMC ∠Z g | of the phase difference of alternating current power grid impedance and converter impedance Z MMC More than or equal to 180 degrees, and flexible direct current transmission system will generate high-frequency oscillation;By scanning and calculating the impedance of converter, the high-frequency fluctuation of the impedance phase-frequency characteristic of converter is obtained, and the impedance phase of converter fluctuates up and down in the range close to 90 degrees by high-frequency fluctuation.Analysis shows that the high-frequency fluctuation of converter impedance phase is generated by cross-coupling component in converter model.

The invention relates to the technical field of intelligent power grids, and discloses a fan grid-connected oscillation early warning method and system considering impedance time variation and a medium, and the method comprises the steps: firstly, determining an impedance ratio model of a fan grid-connected system, and carrying out the calculation based on a generalized Nyquist stability criterion to obtain a Nyquist curve of an impedance ratio matrix; and then correcting the early warning margin of the criterion on the basis of the criterion to obtain a modified fan impedance expression and impedance ratio matrix. After the impedance time-varying characteristic is considered, the Nyquist curve presents a curve band with a certain width, and the curve band is used as an oscillation early warning impedance criterion. For impedance change differences caused by time-varying characteristics under different operation conditions, the width of a Nyquist curve band also changes, the potential oscillation risk degree of the system is evaluated by using the width of the curve band, a time-varying characteristic index CTI of an impedance criterion is introduced to quantify the width of the curve band, and the quantified curve band width is used as an oscillation risk evaluation index. And early recognition and early warning of the oscillation trend of the fan grid-connected system are realized.

The invention discloses a control design method of a following network type converter for inhibiting high-frequency resonance induced by a power loop, which comprises the following steps of: establishing small signal models of a current inner loop and a power outer loop of the following network type converter in a discrete domain, and calculating by using a hippeai stability criterion and a Nyquist stability criterion to obtain an accurate control parameter design range of the current inner loop and the power outer loop; therefore, the high-frequency resonance induced by the power loop is effectively suppressed, and the stability of the system is improved; when the problem of high-frequency resonance generated by the converter is solved, the problem of high-frequency resonance caused by a current inner loop of the converter is considered, and the problem of high-frequency resonance caused by interaction between a power outer loop and the current inner loop of the converter is also considered; according to the method, the high-frequency resonance problem caused by the current inner loop can be effectively suppressed, meanwhile, the design range of the control parameters of the power outer loop is determined by using the Nyquist criterion based on the stability of the open-loop transfer function of the power outer loop, the design is more reasonable, and the system stability can be further improved.