Output impedance

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

Renewable Energy Systems Instability Involving Grid-Parallel Inverters

Abstract: This paper presents a study of renewable energy system stability based on impedance models of the sources and the grid. The focus is grid-parallel inverters controlled in the current injection mode. System stability analysis based on source output impedance and load input impedance is generalized to current-source systems. Output impedance modeling of current-controlled PWM inverters for grid interface of renewable sources is presented to provide the necessary impedance models for system stability analysis. The effects of current control loop design and output filter configurations on the inverter output impedance are considered. A practical method to measure grid impedance using a frequency analyzer is presented, and the associated difficulties due to the presence of harmonics in the grid voltage are discussed. An example system involving a single-phase grid-connected inverter is presented to demonstrate the application of the proposed system analysis method.

Impedance control circuit

Abstract: An impedance control circuit is provided which controls the output impedance of drivers which are coupled to the impedance control circuit. Accordingly, a desired driver output impedance can advantageously be established and maintained over a wide range of variations in operating conditions and manufacturing processes. Thereby shortening the signal settling time and increasing the attainable signaling frequency.

Continuous time programmable analog block architecture

Abstract: A programmable analog circuit apparatus receives a differential analog input signal and provides a processed differential analog output signal. The programmable analog circuit apparatus includes a first input transconductor, a differential amplifier, and a feedback transconductor. The first input transconductor has a programmable transconductance and includes an input transconductor positive input terminal and an input transconductor negative input terminal and an input transconductor positive output terminal and an input transconductor negative output terminal. The positive and negative input terminals are coupled to receive the differential analog input signal. The differential amplifier includes first and second amplifier input terminals and first and second amplifier output terminals. The positive and negative input transconductor output terminals are coupled to the first and second differential amplifier input terminals. The amplifier output terminals are coupled to the first and second amplifier input terminals. The amplifier provides the processed differential analog output signal via the amplifier output terminals. The feedback transconductor includes a positive feedback transconductor input terminal and a negative feedback transconductor input terminal and a positive feedback transconductor output terminal and a negative feedback transconductor output terminal. The positive and negative feedback transconductor input terminals are coupled to the first and second amplifier output terminals and the positive and negative feedback transconductor output terminals are coupled to the first and second amplifier input terminals. The feedback transconductor output terminals has a high output impedance.

A wide-band AC-coupled current source for electrical impedance tomography

Abstract: A current source suitable for application in electrical impedance tomography (EIT) is described The first stage of the commercially available current-feedback amplifier AD844 constitutes a current-conveyor implementation and allows the construction of wide-bandwidth current sources, thus avoiding the mismatching and temperature-induced problems that arise in discrete realizations The lack in gain accuracy of this circuit is overcome by the inclusion of its input buffer in an operational amplifier (op amp) feedback loop Saturation problems that appear when placing a DC-blocking capacitor between the source and the electrode are solved by a DC feedback that maintains DC voltage at the output near to 0 V without reducing the output impedance of the source Two AC-coupled current sources, in both inverting and non-inverting configurations, are described and their possible applications to EIT are listed

Adjustable impedance driver network

Abstract: A variable impedance driver network comprises a plurality of transmission gates connected in parallel between a voltage source and an output Each transmission gate has a predetermined nominal impedance and by turning on selective gates the overall impedance of the network may be adjusted to match that required at the output