Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

A High-Voltage ZVZCS DC--DC Converter With Low Voltage Stress

Abstract: A high-voltage zero-voltage-zero-current-switched dc--dc converter with low voltage stress is presented in this paper. Its circuit structure is extended from a previously developed zero-voltage-switched dc--dc converter consisting of six series-connected switching devices, one three-phase transformer, and an output current tripler. The voltage stress on each switching device is only one-third of the input voltage. Compared with the previous converter, apart from retaining the advantage of having low voltage stresses on the switches, the main advancements of the proposed converter have also included (1) wider soft-switching range; (2) elimination of circulating energy on the primary side during the freewheeling stage; and 3) use of phase-shift pulsewidth modulation in output voltage control. Detailed topological operations and steady-state characteristics of the converter will be given. A 2.2-kW, 990-V/110-V dc--dc converter prototype has been built and tested. Experimental results are favorably compared with the theoretical predictions.

Small-Signal Model of Voltage Source Inverter (VSI) and Voltage Source Converter (VSC) Considering the DeadTime Effect and Space Vector Modulation Types

Abstract: This paper presents a modified small-signal model of a voltage source inverter (VSI) and a voltage source converter (VSC) that captures model nonlinearities such as deadtime and modulation effects that were not presented in the literature. Previous research has concentrated on developing compensation methods for these types of phenomena in a switching model, but very little on predicting them. In this paper, the small-signal model of the VSI in literature is used, and the different phenomena are then incorporated into the model to get a complete one. In addition, the effect of voltage and current feedback control is also analyzed. The output impedance of the VSI is derived with the modified small-signal model, compared to the conventional one and validated with switching model and experimental results.

Step-up converter combining KY and buck-boost converters

Abstract: A step-up converter is presented, which combines the KY converter and the traditional buck-boost converter. By doing so, the limitations on voltage conversion ratio of the KY converter, up to two, can be improved. Aside from this, such a converter possesses a non-pulsating output current, thereby not only decreasing current stress on the output capacitor but also reducing output voltage ripple.

Low-frequency current ripple reduction in front-end boost converter with single-phase inverter load

Abstract: The low-frequency current ripple that always appears at the input of the single-phase DC/AC inverters decreases the lifetime of DC voltage sources, such as fuel cells and chemical batteries. In this study, based on series and parallel feedback theory, a proportional-integral (PI) controller is designed for the front-end boost converter in two-stage power converters. This controller increases the output impedance of the boost converter, which reduces the low-frequency current ripple at the input of this two-stage converter. Since the designed controller corrupts the dynamic response of the boost converter, the DC-link voltage severely over/undershoots in step load conditions. Overcoming this issue by employing a non-linear gain in the forward path is shown. By applying this proposed technique, the output voltage over/undershoot stays in an acceptable range. Therefore both the low-frequency input current ripple and the DC-link over/undershoot problems disappear simultaneously without employing any additional equipment, especially a bulky DC capacitor. The simulation and experimental results for a 2.5 kW prototype confirm the performance of the proposed idea.

Voltage source with enhanced source impedance control

Abstract: A voltage source having a current feedback control loop for enhanced source impedance control of the output of the voltage source. Current feedback is used for a voltage-source amplifier wherein the source impedance is increased/decreased and/or reshaped by the voltage source amplifier's closed-loop gain and the additional current feedback. In particular, the enhanced source impedance control is accomplished through feedback of the output current of the voltage source to an analog error amplifier at an input to the voltage control loop. The output impedance Z desired is then adjusted in accordance with the equation Z desired =Z inv1 {1+G(s) H(s)}, where G(s) is the voltage source amplifier's closed-loop transfer function, H(s) is the transfer function of the output current feedback circuit and Z inv1 is the original source impedance of the voltage controlled voltage amplifier. Thus, once G(s) is defined, H(s) may be defined simply as the combined impedance of the output current feedback circuit. Impedance of this output current feedback circuit may then be altered until the source impedance of the circuit causes the voltage generating circuit to provide an output impedance which corresponds to the desired output impedance.