Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.

Mitigation of Harmonics in Grid-Connected and Islanded Microgrids Via Virtual Admittances and Impedances

Abstract: Optimization of the islanded and grid-connected operation of microgrids is important to achieve a high degree of reliability. In this paper, the authors consider the effect of current harmonics in single phase microgrids during both modes of operation. A detailed analysis of the effect of the output impedance of the considered primary control loops on the harmonic output of the considered voltage source inverters is initially carried out. A virtual admittance loop is proposed to attenuate the current harmonic output in grid-connected operation that is generated due to the grid voltage distortion present at the point of common coupling (PCC) and due to local non-linear loads. This paper also considers the harmonic current sharing and resulting voltage harmonics at the PCC during islanded operation of the microgrid. A capacitive virtual impedance loop was implemented to improve the harmonic current sharing and attenuate the voltage harmonics at the PCC. Experimental results are given to validate the operation of the proposed algorithms.

High-Power Operation of Terahertz Oscillators With Resonant Tunneling Diodes Using Impedance-Matched Antennas and Array Configuration

Abstract: We report the theoretical and experimental results of an examination of the structure needed to achieve high output power in resonant tunneling diode (RTD) oscillators in the terahertz range. An offset-fed slot antenna and antenna width adjustments were employed in a single oscillator to increase the output power by increasing the radiation conductance and impedance matching. A high output power oscillation (~400 μW) at 530-590 GHz was obtained by RTDs with a large negative deferential conductance (NDC) region and offset-fed slot antennas. The maximization of the output power that was obtained by adjusting the antenna width was attributed to the impedance matching between the RTD and antenna. An output power of >;1 mW is theoretically expected in an oscillator that combines an RTD with a large NDC region, offset-fed slot antenna, and antenna width adjustment. In an array configuration, oscillators with an offset structure were employed for array elements and connected together with the metal-insulator-metal stub structure. A single peak was observed in the oscillation spectrum, and combined output powers of 610, 270, and 180 μW at 620, 770, and 810 GHz were obtained in a two-element array.

An accurate equivalent circuit for the unloaded piezoelectric vibrator in the thickness mode

Abstract: An equivalent circuit model for the unloaded piezoelectric vibrator in the thickness mode is presented. The model contains two branches, the motional branch and the static branch, like the lossless resonator model, but the circuit elements are generalized by making each a complex constant. The mechanical, dielectric and piezoelectric losses associated with the vibrator are accounted for by the imaginary components of the circuit elements. The model produced impedance curves that closely matched the impedance calculated by using equations derived from vibration theory and the data measured for lead zirconate titanate and PVDF - TRFE co-polymer samples. The calculation of the circuit parameters from the complex elastic, dielectric and piezoelectric material constants is straightforward and the model accurately fits both the baseline dielectric behaviour and the piezoelectric resonance around and below the fundamental resonance. Conversely, when the complex circuit parameters are known, the complex material constants can be derived by straightforward calculations without any loss of information.

An Impedance Method for Dynamic Analysis of Active Material Systems

Abstract: This paper describes a new approach to analyzing the dynamic response of active material systems with integrated induced strain actuators, including piezoelectric, electrostrictive, and magnetostrictive actuators. This approach, referred to as the impedance method, has many advantages compared with the conventional static approach and the dynamic finite element approach, such as pin force models and consistent beam and plate models. The impedance approach is presented and described using a simple example, a PZT actuator-driven one-degree-of-freedom spring-massdamper system, to demonstrate its ability to capture the physics of adaptive material systems, which is the impedance match between various active components and host-structures, and its utility and importance by means of an experimental example and a numerical case study.The conventional static and dynamic finite element approaches are briefly summarized. The impedance methodology is then discussed in comparison with the static approach. The basic e...

Uniform and repeatable plasma processing

Abstract: Dynamic control and delivery of radio frequency power in plasma process systems is utilized to enhance the repeatability and uniformity of the process plasma. Power, voltage, current, phase, impedance, harmonic content and direct current bias of the radio frequency energy being delivered to the plasma chamber may be monitored at the plasma chamber and used to control or characterize the plasma load. Dynamic pro-active control of the characteristics of the radio frequency power to the plasma chamber electrode during the formation of the plasma enhances the uniformity of the plasma for more exact and controllable processing of the work pieces.