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.

Dynamic current balancing for power converters

Abstract: A current balance arrangement for the power switching devices of a push-pull converter circuit is disclosed. A dynamic dead band circuit is incorporated into a pulse width modulation current balance and output voltage regulation control circuit to prevent current imbalance from causing saturation of the power transformer core for all operating conditions of the converter including input voltage falling below its rated low-line value, sudden load surges, or turning off of the converter power supply. Whenever the dynamic dead band circuit determines that inverter current flow is being terminated by the dead band interval of the converter clock, a control signal is sent to the pulse width modulation circuitry of the converter to effect inverter current termination prior to initiation of the clock dead band interval in subsequent cycles of converter operation. The invention eliminates the need for providing inverter power switching devices having closely matched electrical characteristics.

Low-Frequency Resonance Suppression of a Dual-Active-Bridge DC/DC converter Enabled DC Microgrid

Abstract: In this paper, the small signal stability issue of a dual-active-bridge (DAB) converter enabled dc microgrid is addressed. The derived impedance characteristic of the source DAB converter reveal that the stability of this dc grid is decided by the low-frequency terminal behaviors of integrated units, which is different from that of dc microgrids powered by other types of source converters. At this low-frequency range, the tightly regulated load converter exhibits constant power load behavior even with a low control bandwidth, which degrades system stability by exacerbating interactions among power converters. Moreover, the deployed power management strategy requires operating mode transitions of energy storage units to achieve intelligent power flow, which further complicates system impedance characteristics. To analyze and solve these issues, the systematic impedance models of this dc grid under different operation modes are derived and analyzed. Reduced-order low-frequency models are simplified from the systematic impedance model to unravel the resonance mechanism. In addition, an impedance shaping technique is proposed to eliminate the resonant path in the reduced-order low-frequency models, therefore the dc grid stability has been improved. Finally, a hardware-in-the-loop application with OPAL-RT real-time simulators is used to validate proposed methods.

Low-frequency negative capacitance effect in systems of metallic nanoparticles embedded in dielectric matrix

Abstract: A negative capacitance (NC) effect in a low-frequency range (4–8×105Hz), previously shown to take place mainly in semiconductor structures, is evidenced in a nanometric system constituted by metallic (Ga) nanoparticles embedded in an insulating (SiOxwithx~1) matrix. The dependence of the NC phenomenon on the time-dependent transient current through the system is evidenced. A remarkable enhancement of the effect with size reduction of the nanoparticles is manifested. The physical mechanism responsible for the current inertia appears to be related to the space charges located at the multiple insulator–metal interfaces.

Synthesis of zero-impedance converter

Abstract: A method for synthesizing a system that converts a finite value of an impedance to zero, with an associated finite current and zero voltage, is presented. The synthesis method comprises positive current feedback of an exactly specified nature and value of its transfer function. The stability and dynamics of the system are controlled by an additional voltage loop. The zero-impedance converter is used to synthesize load-independent systems including (switch-mode) power converters and electric motor drive systems incorporating any kind of motor. >