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.

A digital controlled PV-inverter with grid impedance estimation for ENS detection

Abstract: The steady increase in photovoltaic (PV) installations calls for new and better control methods in respect to the utility grid connection Limiting the harmonic distortion is essential to the power quality, but other requirements also contribute to a more safe grid-operation, especially in dispersed power generation networks For instance, the knowledge of the utility impedance at the fundamental frequency can be used to detect a utility failure A PV-inverter with this feature can anticipate a possible network problem and decouple it in time This paper describes the digital implementation of a PV-inverter with different advanced, robust control strategies and an embedded online technique to determine the utility grid impedance By injecting an interharmonic current and measuring the voltage response it is possible to estimate the grid impedance at the fundamental frequency The presented technique, which is implemented with the existing sensors and the CPU of the PV-inverter, provides a fast and low cost approach for online impedance measurement, which may be used for detection of islanding operation Practical tests on an existing PV-inverter validate the control methods, the impedance measurement, and the islanding detection

Virtual Impedance Current Limiting for Inverters in Microgrids With Synchronous Generators

Abstract: This paper focuses on current limiting for voltage-controlled inverters during overloads caused by poor transient load sharing between inverters and synchronous generators in islanded microgrids The use of simple current reference saturation limiters can cause instability when the voltage regulator loses control after the current reference saturates The use of virtual impedance for current limiting is shown to improve transient stability during current limiting when operating in parallel with synchronous generators Small-signal analysis is used to set the virtual impedance magnitude and $X/R$ ratio, and validation is provided by simulation and experimental results

Apparatus for providing a control signal for a variable impedance matching circuit and a method thereof

Abstract: An apparatus for providing a control signal for a variable impedance matching circuit comprises a control module configured to generate a control signal for adjusting an impedance of a variable impedance matching circuit coupled to an antenna module. The control module is configured to generate the control signal based on a sensor signal received from a sensor circuit located in proximity to the antenna module. The sensor signal comprises information related to a power of an electromagnetic signal radiated by the antenna module.

Influence of the boundaries in the impedance of porous film electrodes

Abstract: This paper presents an enhanced model for the impedance of porous film electrodes. The impedance of a transmission line with two transport channels, a crosswise element and arbitrary terminal loads is solved analytically. The local impedances at the boundaries represent a frequency-dependent response of the blocking of ionic and electronic charge carriers at the two faces of the electrode region. A general expression is found that contains, as particular cases, a number of models of impedance for porous electrodes used in the literature. Some examples of the generalised transmission line illustrate the use of the model in the interpretation of experimental data. First, a polarisable electrode showing low-frequency dispersion of the constant phase element (CPE) type is analysed, and diagnosis criteria are derived to recognise whether the dispersion is caused by the boundary or the inner surface. Secondly, the manifestation in the impedance of the failure of a porous electrode due to direct charge transfer between the substrate and a redox couple in solution is investigated.

Light emitting diode driver

Abstract: A LED driver (10) is disclosed. The LED driver (10) includes a high frequency inverter (20) and an impedance circuit (30). The high frequency inverter (20) operates to produce a high frequency voltage source whereby the impedance circuit (30) directs a flow of alternating current through a LED array (40) including one or more anti-parallel LED pairs, one or more anti-parallel LED strings, and/or one or more anti-parallel LED matrixes. A transistor (T3) can be employed to divert the flow of the alternating current from the LED array (40), or to vary the flow of the alternating current through LED array (40).