Power density

About: Power density is a research topic. Over the lifetime, 9534 publications have been published within this topic receiving 197264 citations. The topic is also known as: volumic power & volume power density.

A High Power Density Series-Stacked Energy Buffer for Power Pulsation Decoupling in Single-Phase Converters

Abstract: A high-efficiency, high-power-density buffer architecture is proposed for power pulsation decoupling in power conversion between dc and single-phase ac. We present an active decoupling solution that yields improved efficiency and reduced circuit complexity compared to existing solutions. In the proposed architecture, the main energy storage capacitor is connected in series with an active buffer converter across the dc bus. The series-stacked capacitor blocks the majority of the dc bus voltage to reduce the voltage stress on the buffer converter, such that fast, low-voltage transistors can be employed for the buffer converter. Moreover, the series capacitor provides the majority of the power pulsation decoupling through a wide voltage swing, and the buffer converter only needs to process a small fraction of the total power of the entire architecture, allowing a very small active circuit volume and very high system efficiency. The circuit operation and design constraints are analyzed in detail. In the proposed buffer architecture, the series stacking of a nearly lossless capacitor and a lossy converter presents a challenge of capacitor voltage balancing and power loss compensation. We propose a control scheme exploiting the small ripple in the bus voltage and dc input current to compensate for the power loss in the buffer converter while maintaining the voltage balance. Light-load techniques are also introduced to ensure that the buffer architecture meets strict ripple requirements while providing sufficient loss compensation. A 2-kW hardware prototype based on low-voltage GaN switches has been built to demonstrate the performance of the proposed solution. A power density of 25 W/cm $^3$ (410 W/in $^3$ ) by rectangular box volume and an efficiency above 98.9% across a wide load range has been experimentally verified.

Sensitivity of a Nanocrystalline Luminescent Thermometer in High and Low Excitation Density Regimes

Abstract: Two figures of merit are typically taken into account studying rare-earth-doped materials and processes suitable for optical nanothermometry, namely, temperature sensing range and the sensitivity. To optimize the composition of such phosphors and make quantitative comparison between different materials, other factors, such as excitation density and pulse duration, have to been included. Owing to the metastable character of lanthanide excited states, the excitation intensity has a critical importance but has been disregarded so far. Our studies show, based on a new nanocrystalline Er:LiYbP4O12 luminescent thermometer, the influence of the excitation power density on its suitability for temperature sensing. The highest sensitivity was reached for LiYbP4O12:0.1% Er nanocrystals upon pulsed excitation: 2.88%/K at average power below 25 mW/cm2, while the same material displayed lower ∼0.5%/K sensitivity at higher 50–300 mW/cm2 excitation intensities. The mechanism responsible for the observed sensitivity chang...