Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Modeling and Stability Analysis of $LCL$ -Type Grid-Connected Inverters: A Comprehensive Overview

Abstract: Due to the advantages of superior harmonics attenuation ability and reduced size, the LCL filter has been widely adopted to interface between the inverter and the grid for improving the quality of injected grid currents. However, the high-order characteristics and various constraints of the LCL filter complicate the filter design. Moreover, the stability of the internal current control loop of the individual inverter is susceptible to the inherent LCL -filter resonance peak. Meanwhile, the overall system stability would be aggravated by the external interactions between the inverter and the weak grid as well as among the paralleled inverters. Both the LCL -filter resonance peak and two types of interaction would cause severely distorted grid currents. Motivated by the existing problems, a comprehensive review on the modeling and stability analysis of the LCL -type grid-connected inverters is conducted in this paper. Concretely, the generalized parameter constraints of the LCL filter are outlined to facilitate the passive components selection, and the magnetic integration techniques of filter inductors are also introduced to reduce the weight and size of filter for increasing the power density of the system. Then, the various damping methods for enhancing the individual internal stability and the relevant application issues are also discussed. Furthermore, the impedance-based method for evaluating the system-level interactive stability is subsequently reviewed, with the emphasis on different modeling methods of inverter output impedance and online impedance measurement techniques. Finally, the future research trends on the modeling and stability analysis of LCL -type grid-connected inverters are also presented.

Review of narrowband impedance-matching limitations

Abstract: Many antennas can be characterized by their radiation Q (the ratio of reactance to radiation resistance). A classic problem is determining the maximum possible bandwidth, constrained by the maximum permissible reflection magnitude, and the number of tuned circuits in the impedance-matching circuit. This paper presents a review on theoretical limitations of narrowband impedance matching.

Broadband Continuous-Mode Doherty Power Amplifiers With Noninfinity Peaking Impedance

Abstract: In this paper, a broadband continuous-mode Doherty power amplifier (CM-DPA) is realized taking advantage of the noninfinity output impedances of peaking stage Specifically, the carrier PA of the designed DPA operates in a continuous class-J mode when the peaking PA is in the OFF-state, where the output impedance of the peaking PA has some influences on the carrier PA When the peaking transistor is in the OFF-state, the load impedance variation of the carrier transistor versus noninfinity peaking impedance is presented in this contribution The proposed method surmounts the back-off drain efficiency deterioration of DPAs at two side working bands through elaborately processing the noninfinity peaking impedance This paper also presents a method to derive the required OFF-state output impedance of the peaking stage by the carrier PA in a symmetrical broadband DPA A broadband CM-DPA working over 16–27 GHz (bandwidth of 51%) is designed and fabricated for interpreting our theories The simulated load trajectory of the carrier transistor is in line with the design space of continuous class-J mode Under continuous wave excitation, experimental results show the drain efficiencies of 465%–635% at 6-dB output back-off power levels and 56%–753% at peaking power levels The maximum output power of this DPA is 438–452 dBm with a gain of 94–115 dB across the whole working band Furthermore, a 20-MHz LTE modulated signal with a peak-to-average power ratio of 74 dB is also applied to the fabricated CM-DPA at 22 GHz At an average output power of 375 dBm, measurement results show the adjacent channel power ratios of −302 and −501 dBc before and after digital predistortion, respectively

Harmonic Suppression and Stability Enhancement for Parallel Multiple Grid-Connected Inverters Based on Passive Inverter Output Impedance

Abstract: In this paper, the inverter output impedance is passivized for solving the harmonic and the stability problems in the multiparallel inverters The harmonics are easily aroused because of the disturbances, and the system stability is challenged by the grid impedance Based on the simplified equivalent impedance model, the two problems are analyzed in the low-frequency (LF) band and the high-frequency (HF) band, respectively Aiming at improving the LF performance, the weighted-proportional grid voltage feedforward and the harmonic quasi-resonant controller with phase compensation are proposed The dynamic performance is enhanced with an additional current reference generation scheme In order to improve the HF performance, a novel digital phase lead filter which brings the system back to a minimum-phase case is proposed By the proposed control method, the high modulus of each inverter output impedance $Z_{o}$ is guaranteed, while the phase angles of $Z_{o}$ over the entire frequency band are avoided to be lower than −90° The experiments based on four-parallel inverters have been conducted to validate the effectiveness of the proposed control method

Structure and Dimension Effects on the Performance of Layered Triboelectric Nanogenerators in Contact-Separation Mode

Abstract: A triboelectric nanogenerator (TENG) is a potential solution for providing high output power by continuously harvesting ambient energy, which is expected to sustainably charge a battery for the new era—the era of the Internet of things and sensor networks. Generally, the existence of parasitic capacitance has been considered to be harmful in its output performance. Here, we systematically investigate the effects of structure and dimension of a TENG on its performance from the point view of parasitic capacitance by fabricating two types of layered TENGs with considering the dissimilarity of the two dielectric materials, symmetrical (ABBA) and alternate (ABAB) layered structure (SYM-TENG and ALT-TENG). Theoretical models of the two types of layered TENGs are proposed for illustrating their differences in parasitic capacitances and output characteristics. Larger parasitic capacitance enables the TENG to accommodate higher triboelectric charge density while reducing the internal impedance and maximum power de...