Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

Laminated voltage measuring device

Abstract: PROBLEM TO BE SOLVED: To improve the resolution of an A/D converter. SOLUTION: A switching control means 317 executes switching control of a switch means 316 based on a control table set corresponding to the polarity of an input voltage to a differential amplifier 314, to thereby execute output control of a reference voltage (0 V or DC 5 V) from a reference power source of the differential amplifier 314. Hereby, the switching control means 317 can square an input voltage from the differential amplifier 314 to the A/D converter 315 with an input voltage range of the A/D converter 315 in each polarity inversion. It is not required that the input voltage range of the A/D converter 315 is divided and used half-and-half in each polarity inversion as before, and the input voltage range of the A/D converter 315 can be used fully, to thereby acquire double resolution compared with hitherto, and the resolution of the A/D converter 315 can be improved up to its original resolution. COPYRIGHT: (C)2002,JPO

Virtual Impedance Based Stability Improvement for DC Microgrids with Constant Power Loads

Abstract: DC microgrid provides an efficient way to integrate different kinds of renewable energy sources with DC couplings. In this paper, in order to improve the stability of DC microgrids with constant power loads (CPLs), a virtual impedance based method is proposed. The CPLs have inherent instability issues induced by negative incremental impedances. This negative impedance makes the system poorly damped and the stability is thereby degraded. To enhance the system stability, virtual impedance based stabilizer comprised of series-connected inductance and resistance is employed. In particular, two types of stabilizers are used. Type I stabilizer locates at the output capacitor branch, and Type II stabilizer locates at the output inductance branch. Meanwhile, considering that the parallel interfacing converters are commonly in parallel in a microgrid, droop control is taken into account here. To validate the stability with the above stabilizers in a DC microgrid with parallel interfacing converters and CPL, the impedance matching approach is employed. The output impedance of the source converter and input impedance of the load are calculated respectively, and the influence of droop control, negative incremental impedance of CPL, proposed stabilizers are considered in the calculation of the impedance. It is demonstrated that with the proposed stabilizers, the instable poles can be moved to the stable region in the frequency domain. Simulation model with three interfacing converters is implemented based on MATLAB/Simulink to verify the proposed method.

New method for noninvasive measurement of utility harmonic impedance

Abstract: The new, noninvasive method of measurement for power system harmonic impedance is presented in the paper. The method is based on the observation of variations of voltage and current harmonics caused by natural load variability. The novelty of the method lays in a way the method rejects segments of data containing insufficient or false information about the identified power system. Segment selection/rejection uses logical conditions applied to RMS values of measured voltage and current. Harmonic impedance of the power grid is then calculated using modified power spectral method. The method was validated in a field test conducted at 30 kV feeder bus of HV/MV substation. Details of the experiment and the results are discussed the paper. Obtained results confirm that the method copes with temporal, band-limited excitation as well as with deep, sudden changes of utility background voltage.

Negative Impedance Converter With Reduced Nonideal Gain and Parasitic Impedance Effects

Abstract: In this paper, two novel negative impedance converter (NIC) structures are proposed. One of the introduced NICs exhibits the property of both simultaneously reduced nonideal gain and parasitic impedance effects. Also, the other one shows the property of reducing only parasitic impedance effects and employs only second-generation current conveyors; accordingly, it can be realized with commercially available active devices such as AD844s. In order to show the performance of the introduced NICs, a versatile circuit employing a minimum number of active and passive elements for all the analog filters and lossy inductor simulators is developed. The proposed topology with appropriate component and input port selections gives four kinds of lossy grounded simulated inductors as well. Further, the presented multipurpose circuit is the first one that provides both of the current-mode and voltage-mode standard universal filter responses as well as synthetic inductors from the same topology. The developed topology employing only grounded capacitors can also realize transimpedance-mode low-pass and bandpass responses simultaneously; thus, it is convenient for integrated circuit (IC) realization. Likewise, positive lossy inductor simulators consist of a grounded capacitor. Nevertheless, the realized circuit requires a single resistive component-matching condition. Simulation results using SPICE program and experimental results are included to verify the theoretical ones.