14 results about "Nyquist curve" patented technology

The invention belongs to the field of stability analysis of a grid-connected system of a grid-building converter, and particularly relates to a grid-building converter grid-connected resonance risk analysis method considering virtual impedance, which comprises the following steps: S1, establishing a three-phase time domain differential equation and simplifying the equation into a single-phase equivalent time domain model; converting into a harmonic state space model of the main circuit; s2, constructing a harmonic state space model of a control system comprising an active power control loop and a reactive power control loop; s3, introducing a virtual impedance control link, and correcting the voltage amplitude reference phasor output by the reactive power control loop; deriving an expression of a modulation signal disturbance phasor; s4, obtaining a complete frequency domain admittance model YGSC of the network construction converter considering the influence of the virtual impedance; an open loop gain TGFM of the grid converter grid-connected system is constructed; and S5, drawing a Nyquist curve based on TGFM, and carrying out resonance risk determination. According to the method, the interaction dynamic characteristics of the network building converter and the power grid under the influence of the virtual impedance can be accurately represented, and the resonance risk of the grid-connected system is evaluated.

The invention discloses a power supply detection device and a test method thereof, particularly relates to the field of power electronic control, and is used for solving the problems of high-frequency phase distortion and incapability of reflecting a stability boundary under a real load dynamic state in an open-loop state caused by introduction of additional impedance due to disconnection of a loop in an existing open-loop injection test method. A switching node voltage ripple signal is synchronously collected as a disturbance input signal and an output voltage feedback signal is synchronously collected as a response output signal in a power supply closed-loop state; performing time domain alignment on the two signals to generate a time correlation signal pair; fourier transform is carried out on the signal pair to extract open-loop transfer function characteristics; mapping the characteristics to an intersection phase angle of a Nyquist plane identification curve and a unit circle; generating a chaos distortion index based on the local curvature change characteristics of the Nyquist curve of the intersection neighborhood; and correcting the phase angle of the intersection point by using a chaotic distortion index, and outputting a loop stability evaluation conclusion according to a correction result, thereby realizing high-precision stability evaluation of uninterrupted closed-loop control.

The invention discloses a grid-connected stability analysis method for a multi-converter system, and the method comprises the steps: building a transfer function model from the voltage amplitude-phase disturbance to the power harmonic disturbance of a converter port based on the admittance characteristics of converters, the conversion relation between the voltage / current amplitude-phase disturbance and the positive and negative sequence disturbance, and the power disturbance decomposition relation; simplifying the voltage-power harmonic models of the plurality of converters and connecting lines step by step through series aggregation operation and parallel aggregation operation to generate a grid-connected point single-port voltage-power harmonic transfer function model; and combining the grid-connected point single-port model with a power grid side voltage-power harmonic transfer function model, and judging the system stability according to the origin surrounding property of a Nyquist curve of a joint transfer function determinant.

The invention relates to an electrochemical impedance spectroscopy-based battery health state estimation method, which comprises the following steps of: acquiring EIS data of different batteries with known SOH, and establishing a corresponding Nyquist curve; based on the medium-low frequency band and low frequency band data of the Nyquist curves of the different batteries, determining medium-low frequency Euclidean distances corresponding to the different batteries; fitting to obtain an SOH estimation equation by combining the SOH of different batteries and the Euclidean distance of low and medium frequencies; carrying out EIS test on the to-be-tested battery to obtain battery impedance data, establishing a Nyquist curve of the to-be-tested battery, and determining a low and medium frequency Euclidean distance of the to-be-tested battery; and substituting the low and medium frequency Euclidean distance of the to-be-measured battery into the SOH estimation equation to obtain an SOH value corresponding to the to-be-measured battery. Compared with the prior art, the current health state of the lithium battery can be obtained simply, efficiently and accurately.

The invention relates to the technical field of power grids, in particular to a frequency coupling admittance measurement error evaluation method, device and equipment and a storage medium, and the method comprises the steps: injecting multi-sine disturbance signals of different frequency ranges into tested power electronic equipment for multiple times; acquiring spectral characteristic data of the tested power electronic equipment when the multi-sine disturbance signal is injected each time; determining measurement data of the measured power electronic equipment in different frequency ranges according to the spectral characteristic data when the multi-sine disturbance signal is injected every time, and generating a frequency coupling admittance matrix according to the measurement data in different frequency ranges; and generating a Nyquist curve according to the frequency coupling admittance matrix, evaluating the frequency coupling admittance measurement error of the tested power electronic equipment by using the Nyquist curve, and optimizing the impedance measurement disturbance amplitude of the tested power electronic equipment according to the evaluation result until the measurement error meets the identification precision requirement of the Nyquist curve. Therefore, the problem that the accuracy of a measurement result in related technologies is poor is solved.

The invention provides a converter stability domain determination method based on an amplitude phase contour line. The method comprises the following steps: S1, drawing a Nyquist curve based on a loop gain transfer function of a converter and mapping the Nyquist curve to an amplitude-frequency plane and a phase-frequency plane; s2, converting the amplitude-frequency plane and the phase-frequency plane into an amplitude-phase isoline plane by considering the change of the short-circuit ratio; s3, an amplitude contour line and a phase contour line are drawn in the amplitude phase contour line plane, all intersecting points of the two contour lines are found out, auxiliary lines parallel to the axis are drawn in the amplitude phase contour line plane through the points, and the amplitude phase contour line plane is divided into a plurality of intervals through the auxiliary lines; s4, in the interval formed by the auxiliary lines, if any line parallel to the axis is in the range and has no intersection point, the system is stable in the power grid strength interval; otherwise, the system is unstable.

This application relates to the field of power system stability analysis technology, and particularly to a method, device, electronic equipment, and storage medium for determining oscillations in renewable energy power plants. The method includes: obtaining impedance models of target renewable energy units in a grid-connected renewable energy power plant under multiple preset operating conditions; based on the impedance models, outputting the impedance ratio matrix eigenvalues ​​of the target renewable energy units under each preset operating condition, and generating a Nyquist curve from the impedance ratio matrix eigenvalues ​​of the target renewable energy units under each preset operating condition; determining whether the grid-connected renewable energy power plant has an oscillation risk based on the Nyquist curve; and, when an oscillation risk exists, obtaining the oscillation result of the grid-connected renewable energy power plant based on a preset stability criterion and the network reactance matrix of the grid-connected renewable energy power plant. This solves the problem of unknown renewable energy unit models and parameters in practice, effectively reduces the computational load in the oscillation stability analysis of renewable energy power plants, and improves work efficiency.

The application discloses a kind of stability determination method of power system and unified power quality conditioner.Therein, the method includes: in power system, after injecting disturbance current corresponding to predetermined disturbance frequency to point of common coupling, obtaining point of common coupling voltage signal, grid-side current signal and load-side current signal;Determine the source impedance of grid-side and the load impedance of load-side;According to source impedance and load impedance, determine the return rate matrix;According to return rate matrix, determine the first eigenvalue and the second eigenvalue;Determine the first Nyquist curve corresponding to the first eigenvalue, and the second Nyquist curve corresponding to the second eigenvalue;According to Nyquist curve, determine the stability result of power system at predetermined disturbance frequency.The application solves the technical problem that there is strong limitation when determining whether power system is stable in related technology, and it is difficult to accurately evaluate the true stability degree.

The invention provides an MIMO (Multiple Input Multiple Output) system Nyquist stability judgment method based on dynamic reconstruction of a transfer function, which comprises the following steps of: 1, converting a 2 * 2 impedance model into a complex vector expression by applying a dynamic reconstruction method to obtain an SISO (Single Input Single Output) impedance transfer function with a complete dynamic state; 2, calculating an intersection point of the Nyquist curve and a real axis, judging whether the intersection point of the Nyquist curve and the real axis is located on the right side of a critical point (-1, 0), if so, determining that the system is stable, and otherwise, determining that the system is unstable; and 3, calculating the amplitude margin of the system under the stable working condition, and analyzing the magnitude of the stability margin of the system. According to the impedance analysis method based on dynamic reconstruction provided by the invention, the impedance matrix of the converter MIMO is accurately equivalent to complex vector representation of SISO through a mathematical transformation relation, and the dynamic characteristics of the system are completely reserved while dimension reduction mapping is realized, so that a more accurate stability analysis result is provided. The method has the advantage of universality and can be popularized to various types of converter models.

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 an active power, reactive power and voltage distribution method, system and device and a medium, and the method comprises the steps: constructing an equivalent circuit model of a power system in a Sagomei region, the power system in the Sagomei region comprising a new energy converter, a network-constructed energy storage converter, a load converter and a modular multi-level converter; based on the equivalent circuit model, a Nyquist stability analysis method is adopted to calculate amplitude margins of the power system in the Sagomei region under different steady-state working points so as to quantify the small disturbance stability of the power system in the Sagomei region, and the amplitude margins are defined as distances from an intersection point of a Nyquist curve and a negative real axis to a critical stable point (-1, 0); and respectively designing and executing an active power distribution strategy, a reactive power distribution strategy and a voltage control strategy according to an analysis result of the amplitude margin. The problems that in the prior art, stability quantification means under multiple working conditions are lacked, and a power and voltage coordination control strategy suitable for the multiple working conditions is not formed are solved.

The present application discloses a method, apparatus, device, and storage medium for adjusting a floating wind turbine controller. The method includes: constructing a transfer function of the floating wind turbine power system based on the dynamic characteristic parameters of the floating wind turbine in the floating wind turbine power system and the control gain coefficient of the controller in the floating wind turbine power system; constructing constraints based on the poles of the transfer function and the Nyquist curve; constructing an objective function based on the step response characteristic parameters of the transfer function; under the constraints, optimizing the control gain coefficient with the goal of minimizing the value of the objective function to obtain the optimal value of the control gain coefficient; and controlling the controller to adjust the control gain coefficient according to the optimal value to adjust the stability of the floating wind turbine. The above scheme introduces a transfer function, constructs constraints and an objective function to determine the optimal value of the control gain coefficient of the floating wind turbine controller, and adjusts the control gain coefficient of the controller to the optimal value, thereby achieving the stability of the floating wind turbine efficiently and accurately.

The present invention discloses a parameter design method and a computer medium for a multi-machine grid-connected inverter interconnection system. The method includes: S1. Obtain the d-axis current inner-loop control function and the voltage outer-loop control function according to the structure of a single inverter; S2. Configure the parameters of one inverter according to the first method. The first method includes obtaining the current inner-loop and voltage outer-loop control parameters according to the current inner-loop control function and the voltage outer-loop control function under the constraints of a preset bandwidth and phase margin; S3. Configure the parameters of an unconfigured inverter according to the first method in combination with the bandwidth difference constraint and impedance adaptability constraint between inverters; draw the Nyquist curve; S4. Determine whether the Nyquist curve encloses the point (-1, j0). If not, it is determined that the parameter configuration of this inverter is completed; if so, it is determined that this inverter is an unconfigured inverter; after the determination ends, enter S3; S5. When the parameters of all inverters are configured, the parameter design of the system is completed.

This invention relates to the field of energy storage system technology, specifically to a battery aging detection method and system based on impedance spectroscopy. The battery aging detection method and system based on impedance spectroscopy is characterized by comprising: an adaptive frequency band focusing excitation module; a synchronous sampling and frequency domain transformation module; a spectral morphology feature encoding module; an intra-cluster dynamic baseline module; a temperature compensation module; a normalized weighted scoring module; an aging grading determination module; an aging trajectory prediction module; and an online evolution module for detection configuration. Compared with existing technologies, by using spectral morphology feature encoding, the Nyquist curve is discretized into a sequence of morphological descriptors, retaining the non-parametric aging information lost in ECM fitting, thus improving the sensitivity of early aging detection; through the adaptive frequency band focusing mechanism, the excitation energy is redistributed to the most sensitive frequency band according to the aging feature sensitivity ranking of each frequency band in the previous round of detection, thereby improving the signal-to-noise ratio.