Topic
Output impedance
About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.
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TL;DR: In this paper, the impedance of small platinum electrodes has been measured as a function of frequency in the range of 0·1 Hz to 10 kHz, and the value of K is about 2·5 Mω for a surface are of 0.05 mm2.
Abstract: The impedance of small platinum electrodes has been measured as a function of frequency. In the range of 0·1 Hz to 10 kHz, this impedance Z can be described accurately as K/(i2πf)m. The value of K is about 2·5 Mω for a surface are of 0·05 mm2. The values for m are in the order of 0·75. Various step responses are computed based on this expression and are compared to recorded wave forms. All step responses are shown to result directly and consistently from the same expression. The consequences of these results for various models and equivalent circuits of the electrode-medium interface are discussed.
107 citations
TL;DR: In this paper, the authors studied the effect of the voltage variation caused by the current flow through the capacitors on the performance of the four-switch inverter in the low-frequency region.
Abstract: The four-switch inverter, having a lower number of insulated gate bipolar transistors(IGBTs), has been studied for the possibility of reducing the inverter cost. But it has a limited performance in the low-frequency region, because the balance among the phase currents collapses due to the fluctuation of the center tap voltage of the DC-link capacitors. This problem could be solved if the DC-link capacitance is infinitely large, but it is a costly solution. In this paper, this problem is looked at from the perspective of source impedance and the voltage variation caused by the current flow through the capacitors. The source impedance of the center tap is large compared with other normal IGBT arms. This causes an asymmetry among the three voltage sources, resulting in phase current distortion and unbalance. Second, the capacitor voltage change caused by current flow is another source of current distortion and unbalance. The voltage errors are derived, and based on them, a compensation method is proposed. Effectiveness of the proposed method is demonstrated by the simulation and experimental results.
106 citations
TL;DR: The proposed line impedance cooperative stability region identification method is more effective and less conservative than the norm-based stability criteria and can provide guidance for system planning and stabilization method researches with simplified computational process.
Abstract: Although the low-frequency/harmonic oscillation of grid-tied inverters under weak grids has been widely researched, the classical impedance-based approach focuses more on the identification of stable operating points and the stability margin of return-ratio matrix. Furthermore, it cannot provide stability regions of system parameters. Therefore, this paper proposes a line impedance cooperative stability region identification method. Firstly, the output impedance matrix and the input admittance matrix are respectively built in $d-q$ axis. Secondly, a novel stability forbidden region is proposed. It is less conservative than the forbidden region criteria in existing literatures. Based on the stability forbidden region, the stability operation region is established via mirror, translation and rotation mappings. It is less conservative compared with the norm-based stability criteria. The solving of stability operation region is first transformed into the eigenvalue identification problem in this paper. Furthermore, the detailed line impedance cooperative stability region is solved by guardian map theory. It can provide guidance for system planning and stabilization method researches with simplified computational process. Finally, the simulation and experimental results show that the proposed line impedance cooperative stability region identification method is more effective and less conservative.
106 citations
Patent•
24 Jun 1986
TL;DR: In this article, an impedance matching arrangement is proposed for frequency hopping radio communications system which is operable over a wide frequency band, so as to match the operating impedance of the antenna at each of the frequencies used.
Abstract: An impedance matching arrangement is suitable for use with a frequency hopping radio communications system which is operable over a wide frequency band, so as to match the operating impedance of the antenna at each of the frequencies used. As the frequency of the radio system hops from one frequency to another, a note of any impedance mismatch is noted and data derived therefrom is stored for future use when that frequency is next selected so as to reduce any impedance mismatch.
106 citations
Patent•
30 Jan 2003
TL;DR: In this article, an impedance matching device is provided with an input detector for detecting RF voltage and current at the input terminal, and an output detector to detect RF voltage outputted from the output terminal.
Abstract: An impedance matching device is provided, for which the electric characteristics at an output terminal are accurately analyzed. The matching device is provided with an input detector for detecting RF voltage and current at the input terminal, and an output detector for detecting RF voltage outputted from the output terminal. The matching device also includes a controller for achieving impedance matching between a high frequency power source connected to the input terminal and a load connected to the output terminal. The impedance matching is performed by adjusting variable capacitors based on the detection data supplied from the input detector. When the impedance of the power source is matched to that of the load, the controller calculates the output impedance, RF voltage and RF current at the output terminal, based on the adjusted capacitances of the capacitors, a pre-obtained reactance-impedance data and the detection data supplied from the output detector.
106 citations