Output impedance

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

Modeling, Analysis, and Suppression of the Impact of Full-Scale Wind-Power Converters on Subsynchronous Damping

Abstract: This paper presents modeling, analysis, and suppression of the impact of a voltage-source converter (VSC)-based full-scale wind turbine (FSWT) on subsynchronous damping in power systems. First, a detailed output impedance model of the grid-interfacing VSC is presented and analyzed under different converter operating modes, control functions, and variations in operating point. Second, the output impedance model is used to analyze the impact of the grid-interfacing VSC on the electrical damping characteristics in the subsynchronous frequency range and interactions with an electrically nearby synchronous generator. The IEEE first benchmark for subsynchronous resonance studies is used for theoretical analysis and simulation results. It is found that the grid-interfacing VSC of the FSWT can have a negative impact on overall electrical damping and there is a risk of subsynchronous torsional oscillation especially at lower frequency modes. Third, to mitigate such interactions, an active damping controller is developed to reshape the output impedance of the interfacing VSC and yield positive electrical damping at torsional modes. Time-domain simulation results are presented to validate the theoretical analysis and show the effectiveness of the proposed active damping controller.

Input filter interaction in three phase AC-DC converters

Abstract: It is well known that the addition of an input filter preceding a switched mode regulator poses a problem of performance degradation and potential instability due to its negative input impedance at low frequencies. Three phase converters are essentially multivariable systems. The objective of this paper is to analyze the problem of input filter interaction in three phase AC-DC converters from a multivariable perspective and to establish criteria that guarantee stability and satisfactory performance of the converter with an input filter. The dq average model of a three phase boost rectifier is used for the analysis. The minor loop, the stability of which has to be guaranteed is identified. A sufficient condition for stability, based on the singular values of the filter output impedance and converter input admittance matrices is derived. Simulation results are presented to illustrate the results.

A 4–18-GHz reconfigurable RF MEMS matching network for power amplifier applications

Abstract: We have developed a novel reconfigurable matching network based on the loaded-line technique. The network is composed of N-switched capacitors (N = 4–8) with a capacitance ratio of 4–5:1 and is suitable for power amplifiers at 4–18 GHz, or as an impedance tuner for noise parameter and load-pull measurements at 10–28 GHz. The networks are very small, and offer better performance than double or triple stub matching networks. Extensive loss analysis indicates that the 8-element network has a loss of 0.5 dB at 4–12 GHz, and less than 1.5 dB at 18 GHz, even when matching a 10Ω output impedance to a 50Ω load. As expected, the 4-element matching network has about half the loss of the 8-element network, but with much less impedance coverage. Both networks were simulated and measured in high VSWR conditions and can handle at least 500 mW of RF power at 4–18 GHz. The application areas are in phased array antennas, reconfigurable power amplifiers, and wideband noise-parameter and load-pull measurement systems. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 356–372, 2004.

Single-Phase Modified Quasi-Z-Source Cascaded Hybrid Five-Level Inverter

Abstract: This paper proposes the combination of a novel modified quasi-Z-source (MqZS) inverter with a single-phase symmetrical hybrid three-level inverter in order to boost the inverter three-level output voltage. The proposed single-phase MqZS hybrid three-level inverter provides a higher boost ability and reduces the number of inductors in the source impedance, compared with both the single-phase three-level neural-point clamped quasi-Z-source inverter and the single-phase quasi-Z-source cascaded multilevel inverter. Additionally, it can be extended to obtain the nine-level output voltage by cascading two three-level pulse width modulation switching cells with a separate MqZS and a dc source, which herein is called a single-phase MqZS cascaded hybrid five-level inverter (MqZS-CHI). A modified modulation technique based on an alternative phase opposition disposition scheme is suggested to effectively control the shoot-through state for boosting the dc-link voltage and balancing the two series capacitor voltages of the MqZS. The performances of both the proposed MqZS-CHI and the modulation techniques are verified through simulation and experimental results.