41 results about "Nyquist plot" patented technology

A method is provided for measuring D-Q impedance of a component of a polyphase power grid connected to a grid node, and evaluating the margin of stability at a node using Nyquist diagrams generated from the measured D-Q impedance data. A generator, coupled to the polyphase power grid, is controlled to induce suppressed-carrier stimulus current into the grid node. Circuitry measures response signals of suppressed-carrier form existing within a bus voltage at the grid node and a branch current of the component being measured. The method includes measuring complex voltage components of the response signals contained in the bus voltage and complex current components of the response signals contained in the branch current to form simultaneous equations that are resolved to determine the D-Q impedance parameters Zqq, Zqd, Zdq and Zdd of the measured component.

Defects in components in ICs which may cause circuit failures during operation of the IC are often difficult to detect during and immediately after fabrication of the IC by DC test methods. A method of testing components to detect such defects using AC Impedance Spectroscopy is disclosed. Data may be analyzed using Nyquist plots and Bode plots. Nyquist plots of typical defect types are disclosed. Components may include MOS transistor gate structures, contacts, vias and metal interconnect lines. Components tested may be contained in integrated circuits or in test circuits. Integrated circuits containing components tested by AC Impedance Spectroscopy may be partially fabricated or deprocessed after fabrication.

A method for designing the precession crossover parameters of the maglev high-speed rotor system, establishing the complex coefficient dynamic model of the maglev closed-loop rotor system, drawing the negative frequency Nyquist curve of the complex coefficient open-loop transfer function at the highest speed and calculating the low-pass cut-off frequency of the precession crossover , and then determine the correction target at the highest speed according to the phase angle margin requirements of the precession mode, search the design frequency and determine the precession cross gain at the highest speed, and then determine the precession cross gain in the entire speed range to ensure that the rotor advances The phase angle stability margin in the whole speed range realizes the robust and stable design of precession cross feedback. Based on the negative frequency Nyquist curve, the present invention proposes a method for designing the precession cross parameters of the maglev high-speed rotor system from the phase angle margin. Compared with the usual multivariable system design method such as the state space analysis method, it is not only very intuitive, but also has good robustness. Rod, so it is more suitable for use in centrifuges, high-precision CNC lathes, turbines, energy storage flywheels, and practical magnetic suspension high-speed rotor systems such as magnetic suspension flywheels and magnetic suspension control torque gyroscopes.

A probe having a pair of closely spaced electrodes is immersed in the lubricant and one electrode is excited with a relatively low voltage AC current. The frequency is swept over a range of about 1-10,000 Hertz and the current and phase angle measured at selected frequency intervals. The reactive (Z″) and resistive (Z″) impedances are computed for each current measurement and values of Z″ plotted as a function of Z′ as a Nyquist plot. The center of curvature of the plot between the origin and the minimum value of Z″ is located; and, the angle of depression of a line from the origin through the center of curvature Θ is determined from the plot. Samples of lubricant having known concentration of soot are measured and the angle Θ determined for each sample. The angle is then plotted as a function of soot concentration and a smooth curve fitted to the data plots. The curve may be programmed into a microcomputer to be used with the sensor for real time determination of soot concentration.

A novel stability analysis method for a cascade system of a three-phase voltage source PWM rectifier and LLC resonant converter is provided. Based on the front-stage PWM rectifier output impedance model and a back-stage LLC resonant converter input impedance model of a cascade system and the impedance ratio stability criterion, the stability of the cascade system can be analyzed by combining theBode diagram and the Nyquist plot. The invention only needs to derive the output impedance of the front-stage converter and the input impedance of the back-stage converter, and can be used for judgingthe stability of the cascade system. This method avoids the drawback that the stability of cascade system can only be judged by simulation curve, and improves the accuracy of stability analysis of cascade system. The stability of the system can be intuitively seen from Bode diagram and Nyquist curve, and the influence of each parameter in the system on the system stability margin can be analyzed,so that the stability margin of the system can be improved.

The invention discloses a method for quickly computing a Bode plot and a Nyquist plot of rotary mechanical vehicle starting and parking processes. The method is based on rotor vibration signals and key-phase signals, which are measured by an eddy current sensor, of the rotary mechanical vehicle starting and parking processes, and the Bode plot and the Nyquist plot of the vehicle starting and parking processes are quickly computed; and an integral computing process is based on Hilbert transform processing for the vibration signals of the vehicle starting and parking processes, and is combined with phase-retaining filtering processing for the vibration signals and extraction of periodic information in the key-phase signals, so that the Bode plot and the Nyquist plot of the rotary mechanical vehicle starting and parking vibration signals are quickly computed. Experimental data analysis results show that Bode plot and Nyquist plot curves computed by the method are smooth, vibration peak values and vibration phases which are obtained by the method are more accurate, phase computational precision is unaffected by rotation speed, and the method is a good method for computing Bode plots and Nyquist plots of rotary mechanical vehicle starting and parking unsteady signals.

The invention discloses a passive damping control method and system of a single-phase LCL grid-connected inverter. The method comprises steps as follows: an established mathematical equation is converted into an open-loop transfer function of the single-phase LCL grid-connected inverter, the open-loop transfer function of the single-phase LCL grid-connected inverter is decomposed into a form of aproduct of an LCL filter model, a delay link model and a current regulator model, each link Bode image is drawn, the system stability is analyzed according to the open-loop transfer function of the control system and each link Bode image, system current regulator parameters are designed after constraint conditions calculated according to a nyquist diagram are added to the design of LCL filter parameters, and passive damping control of the single-phase LCL grid-connected inverter is realized. The system stability can be improved under the influence of delay of a digital system, damping controlis not required, additional sensors are not required, and the hardware cost of the control system is reduced.

A battery information processing system includes a control device configured to perform capacity calculation processing. The capacity calculation processing is processing for calculating a full charge capacity Q of the module based on a fitting curve Z calculated by fitting processing of a Nyquist plot representing a result of measurement of an AC impedance of the module. In an OCV-SOC curve of the module, there are a flat region in which a ratio of variation is lower than a reference value and a steep region in which the ratio of variation is higher than the reference value. The control device estimates an OCV of the module from a result of detection by a voltage sensor and performs the capacity calculation processing when the estimated OCV is in the flat region.

Embodiments of a digital-to-analog conversion system that utilizes a specialized clock signal to reshape an analog impulse response of a digital-to-analog converter (DAC) are disclosed. Preferably, a shape of the specialized clock signal is such that Nyquist images resulting from digital-to-analog conversion are controlled in a desired manner. In one embodiment, the digital-to-analog conversion system includes a DAC that converts a digital input signal into an analog output signal. A specialized clock signal is applied to the analog output signal of the DAC such that an analog impulse response of the DAC is reshaped according to a shape of the specialized clock signal, thereby providing a modified analog output signal. The specialized clock signal reshapes the analog impulse response of the DAC such that Nyquist images resulting from digital-to-analog conversion are controlled in a desired manner.

The invention discloses a method for judging the stability of a distributed power-supply system based on an equivalent open-loop transfer function. The method comprises the following steps: firstly, equivalently transforming a noise sensitivity transfer function of the system, on the basis of an equivalent two-port network characteristic of a source switch power supply, and deducing the equivalent open-loop transfer function shown in the description; and then respectively measuring port voltages v1(s) and v2(s) by connecting a small signal current source delta (s) to a connection bus of a converter, acquiring the equivalent open-loop transfer function shown in the description under the small signal disturbance, and drawing a Gop(s) nyquist diagram; and lastly, judging the stability of the system and forecasting the stability margin of the system according to the nyquist diagram. By using the method provided by the invention, the restraining terms of the original impedance ratio standard are extended. Besides, the method provided by the invention is easily realized and has important theoretic sense and application value in analyzing and designing the distributed power-supply system.

An object of the present invention is to provide a quality inspection method for obtaining a specifying factor which can more reliably indicate powder characteristics of a core material for an electrophotographic ferrite carrier. To achieve the object, a method for inspecting the quality of a core material for an electrophotographic ferrite carrier adopts a method characterized in that the impedance of the core material for the electrophotographic ferrite carrier is measured by using an AC-resistance measurement method to obtain a Nyquist diagram (Cole-Cole plot) in which a real number impedance (Z′) is arranged in an X-axis and an imaginary number impedance (Z″) is arranged in a Y-axis and then the characteristics of the particles of the core material for the electrophotographic ferrite carrier is evaluated by using the Nyquist diagram (Cole-Cole plot). Here, the quality of a core material for the electrophotographic ferrite carrier is judged according to a predetermined equivalent circuit by using the value of the parameters one or two or more in combination selected from |Rs|, Rp₁, CPE-T₁, CPE-P₁, Rp₂, CPE-T₂ and CPE-P₂, which are AC-resistance values (including constant) obtained when the impedance of the carrier particles was measured.

Embodiments of the invention compensate for repeatable run-out errors without causing servo system instability. In one embodiment, HDD has a peak filter on a feedback route of a servo system. The peak filter is designed so that a rotating frequency of a magnetic disk, the high-frequency components contained in the rotating frequency and a peak match the rotating frequency and the high-frequency components. Insertion of a required peak filter into the servo system allows compensation for a repeatable run-out (RRO) error due to an event such as a deviation from the roundness of a track. Also, since a Nyquist diagram of the system satisfies required characteristics, a repeatable run-out error may be compensated for without causing instability of the servo system due to use of the peak filter.

The invention provides a filter for electric vehicle converting equipment, and belongs to the technical field of electric vehicles. The filter is characterized in that the filter comprises a damping filtering unit connected between an input terminal and an output terminal and a resistance-capacitance filtering unit connected between the damping filtering unit and a grounding terminal and used for enabling high-frequency signals to pass. The filter for the electric vehicle converting equipment comprises the damping filtering unit and the resistance-capacitance filtering unit connected between the damping filtering unit and the grounding terminal and used for enabling the high-frequency signals to pass, and the structure is simple; the resistance-capacitance filtering unit is provided so that high-frequency signals can be passed, and the energy loss of a damping resistor is reduced; and the filter for the electric vehicle converting equipment is advantaged by stable performance during practical usage via the simulation of a Bode diagram and a Nyquist diagram and with the combination of stability criterion.