High Step-Up Transformerless Inverter for AC Module Applications With Active Power Decoupling
Not provided.
Automation & Control Systems↗
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Development of an AC Module System: Final Technical Report
The GreenRay Inc. program focused on simplifying solar electricity and making it affordable and accessible to the mainstream population. This was accomplished by integrating a solar module, micro-inverter, mounting and monitoring into a reliable, 'plug and play' AC system for residential rooftops, offering the following advantages: (1) Reduced Cost: Reduction in installation labor with fewer components, faster mounting, faster wiring. (2) Maximized Energy Production: Each AC Module operates at its maximum, reducing overall losses from shading, mismatch, or module downtime. (3) Increased Safety. Electrical and fire safety experts agree that AC Modules have significant benefits, with no energized wiring or live connections during installation, maintenance or emergency conditions. (4) Simplified PV for a Broader Group of Installers. Dramatic simplification of design and installation of a solar power system, enabling faster and more efficient delivery of the product into the market through well-established, mainstream channels. This makes solar more accessible to the public. (5) Broadened the Rooftop Market: AC Modules enable solar for many homes that have shading, split roofs, or obstructions. In addition, due to the smaller building block size of 200W vs. 1000W, homeowners with budget limitations can start small and add to their systems over time. Through this DOE program GreenRay developed the all-in-one AC Module system with an integrated PV Module and microinverter, custom residential mounting and performance monitoring. Development efforts took the product from its initial concept, through prototypes, to a commercial product sold and deployed in the residential market. This pilot deployment has demonstrated the technical effectiveness of the AC Module system in meeting the needs and solving the problems of the residential market. While more expensive than the traditional central inverter systems at the pilot scale, the economics of AC Modules become more and more favorable as the product matures and is made in high volumes. GreenRay's early customers have been highly enthusiastic about the AC Module system benefits.
14 SOLAR ENERGY↗
Hysteresis Reduction in Tunneling Magnetoresistive Sensor With AC Modulation Magnetic Field
A simple and practical AC modulation method to reduce the hysteresis in tunneling magnetoresistive sensor is demonstrated. It is shown that with a suitable AC modulation magnetic field that is applied along the sensing direction of TMR sensor, the hysteresis in the sensor can be reduced to a negligible level. And depending on the amplitude of the modulation field, the sensitivity and the dynamic range of the TMR sensor can be tuned to meet practical requirements in specific applications. Here, the influence of the modulation on the noise of TMR sensor is also studied.
42 ENGINEERING↗
Soft Switching Over the Entire Line Cycle for a Quadruple Active Bridge DCX in a DC to Three-Phase AC Module
This paper is focused on a transformer-isolated quadruple active bridge (QAB) dc-dc converter loaded by three full-bridge dc-ac inverters. The QAB functions as a "DC trans-former" (DCX) in the dc-to-three-phase ac module. The QAB outputs provide time-varying power at twice the line frequency, which presents challenges in maintaining zero voltage switching (ZVS) on the secondary sides during low-power portions of the line cycle. It is shown how ZVS can be achieved in a phase, even at zero-power transfer, using a relatively small circulating current provided by the magnetizing inductance of the high-frequency transformer. The approach is particularly effective in high-voltage applications using SiC MOSFETs, where reductions in switching loss outweigh additional conduction losses due to the circulating currents. A detailed analysis of ZVS switching waveforms at the zero power transfer is presented, including effects of nonlinear device capacitances. Analytical expressions are given for the optimal values of the magnetizing inductance and dead times of the QAB primary and secondary bridges. The approach is verified by experimental results on a 600 V, 4 kW prototype, demonstrating greater than 98.5% efficiency from 1 kW to 4 kW, with a peak efficiency of 99.0%. Compared to conventionally operated prototype, a 54% reduction in total loss is achieved at rated power.
41 EE - Solar Energy Technologies Office (EE-4S)↗
An AC modulated near infrared gain calibration system for a “Violin-Mode” transimpedance amplifier, intended for advanced LIGO suspensions
The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a “tall-thin” rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse “Violin-Mode” vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor’s DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor’s more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz–300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m{sup −1} was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m{sup −1}, at that frequency.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
1 kV, 10-kW SiC-Based Quadruple Active Bridge DCX Stage in a DC to Three-Phase AC Module for Medium-Voltage Grid Integration
Interfacing low voltage dc to medium voltage three-phase ac grid is often based on series-stackable modular converter architectures. To minimize energy storage requirements, it is advantageous to employ a quadruple active bridge (QAB) stage operating as a "dc transformer" in each stackable module. The QAB stage offers three isolated dc link voltages, which then allow for flexible stacking of three single-phase dc-to-ac inverter stages. Each of the module phases processes a pulsating power having a component at twice the line frequency. This presents a challenge in maintaining zero voltage switching (ZVS) on the secondary sides of the QAB during low-power portions of the line cycle. This article is focused on the design of the QAB stage. A detailed analysis of ZVS switching waveforms is presented, including effects of nonlinear device capacitances. It is shown how ZVS can be achieved at all times using a relatively small circulating current provided by the magnetizing inductance of the high-frequency transformer. Analytical expressions are given for the optimal values of the magnetizing inductance and the dead times of the QAB primary and secondary bridges. This approach is verified by experimental results on a 1 kV, 10-kW SiC-based prototype, demonstrating a relatively flat efficiency curve with a peak efficiency of 97.1% at 75% load.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Performance Model for Characterizing AC Modules and Predicting Their Power.
Abstract not provided.
Riley, Daniel↗
SU-F-T-337: Accounting for Patient Motion During Volumetric Modulated Ac Therapy (VMAT) Planning for Post Mastectomy Chest Wall Irradiation
Purpose: To evaluate two dose optimization strategies for maintaining target volume coverage of inversely-planned post mastectomy radiotherapy (PMRT) plans during patient motion. Methods: Five patients previously treated with VMAT for PMRT at our clinical were randomly selected for this study. For each patient, two plan optimization strategies were compared. Plan 1 was optimized to a volume that included the physician’s planning target volume (PTV) plus an expansion up to 0.3 cm from the bolus surface. Plan 2 was optimized to the PTV plus an expansion up to 0.3 cm from the patient surface (i.e., not extending into the bolus). VMAT plans were optimized to deliver 95% of the prescription to 95% of the PTV while sparing organs at risk based on clinical dose limits. PTV coverage was then evaluated following the simulation of patient shifts by 1.0 cm in the anterior and posterior directions using the treatment planning system. Results: Posterior patient shifts produced a difference in D95% of around 11% in both planning approaches from the non-shifted dose distributions. Coverage of the medial and lateral borders of the evaluation volume was reduced in both the posteriorly shifted plans (Plan 1 and Plan 2). Anterior patient shifts affected Plan 2 more than Plan 1 with a difference in D95% of 1% for Plan 1 versus 6% for Plan 2 from the non-shifted dose distributions. The least variation in PTV dose homogeneity for both shifts was obtained with Plan 1. However, all posteriorly shifted plans failed to deliver 95% of the prescription to 95% of the PTV. Whereas, only a few anteriorly shifted plans failed this criteria. Conclusion: The results of this study suggest both planning volume methods are sensitive to patient motion, but that a PTV extended into a bolus volume is slightly more robust for anterior patient shifts.
60 APPLIED LIFE SCIENCES↗
Performance Model for Characterizing AC Modules and Predicting Their Power.
Abstract not provided.
Riley, Daniel↗
Predictive Reliability for AC Photovoltaic Modules Based on Electro-Thermal Phenomena.
Abstract not provided.
Armijo, Kenneth Miguel↗
Evolution of magnetism in Ru doped Na{sub 2}IrO{sub 3}
We synthesized Ru doped single crystalline samples of the honeycomb iridate material Na{sub 2}IrO{sub 3} and studied their magnetic properties using AC and DC magnetic susceptibility. The parent compound Na{sub 2}IrO{sub 3} is a spin orbit driven Mott insulator with long range order below T{sub N} = 15 K. We find that even smallest substitution of Ru changes the antiferromagnetic long range order state to a spin glass like state indicating the fragile nature of magnetism in Na2IrO3. We track the freezing temperature Tg as a function of Ru concentration and the shift of T{sub g} with frequency f of the ac modulation in AC susceptibility which is found to be very different from canonical spin-glasses like Cu-Mn.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
A Performance Model for Photovoltaic Modules with Integrated Microinverters
Photovoltaic (PV) systems using microinverters are becoming increasingly popular in the residential system market, as such systems offer several advantages over PV systems using central inverters. PV modules with integrated microinverters, termed AC modules, are emerging to fill this market space. Existing test procedures and performance models designed for separate DC and AC components are unusable for AC modules because these do not allow ready access to the intermediate DC bus. Sandia National Laboratories' Photovoltaics and Distributed Systems department has developed a set of procedures to test, characterize, and model PV modules with integrated microinverters. The resulting empirical model is able to predict the output AC power of with RMS error of 1-2%. This document describes these procedures and provides the results of model validation efforts.
14 SOLAR ENERGY↗
Modeling Photovoltaic Module-Level Power Electronics in the System Advisor Model; NREL (National Renewable Energy Laboratory)
Module-level power electronics, such as DC power optimizers, microinverters, and those found in AC modules, are increasing in popularity in smaller-scale photovoltaic (PV) systems as their prices continue to decline. Therefore, it is important to provide PV modelers with guidelines about how to model these distributed power electronics appropriately in PV modeling software. This paper extends the work completed at NREL that provided recommendations to model the performance of distributed power electronics in NREL’s popular PVWatts calculator [1], to provide similar guidelines for modeling these technologies in NREL's more complex System Advisor Model (SAM). Module-level power electronics - such as DC power optimizers, microinverters, and those found in AC modules-- are increasing in popularity in smaller-scale photovoltaic (PV) systems as their prices continue to decline. Therefore, it is important to provide PV modelers with guidelines about how to model these distributed power electronics appropriately in PV modeling software.
14 SOLAR ENERGY↗
Mass spectrometer has wide angular acceptance
Higher mass resolution is achieved by replacing conventional mass/velocity spectrometers with system of planar ac-modulated grids. System gives focusing for all angles of incidence. Ac-modulation and detection scheme minimizes sensitivity to light and other types of radiation.
Neugebauer, M. M.↗
Predictive Reliability for AC Photovoltaic Modules Based on Electro-Thermal Phenomena.
Abstract not provided.
Armijo, Kenneth Miguel↗
Static and Dynamic Effects of Lateral Carrier Diffusion in Semiconductor Lasers
Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. It is well known that the value of diffusion coefficients affects the threshold pumping current of a semiconductor laser. At the same time, the strength of carrier diffusion process is expected to affect the modulation bandwidth of an AC-modulated laser. It is important not only to investigate the combined DC and AC effects due to carrier diffusion, but also to separate the AC effects from that of the combined effects in order to provide design insights for high speed modulation. In this presentation, we apply a hydrodynamic model developed by the present authors recently from the semiconductor Bloch equations. The model allows microscopic calculation of the lateral carrier diffusion coefficient, which is a nonlinear function of the carrier density and plasma temperature. We first studied combined AC and DC effects of lateral carrier diffusion by studying the bandwidth dependence on diffusion coefficient at a given DC current under small signal modulation. The results show an increase of modulation bandwidth with decrease in the diffusion coefficient. We simultaneously studied the effects of nonlinearity in the diffusion coefficient. To clearly identify how much of the bandwidth increase is a result of decrease in the threshold pumping current for smaller diffusion coefficient, thus an effective increase of DC pumping, we study the bandwidth dependence on diffusion coefficient at a given relative pumping. A detailed comparison of the two cases will be presented.
Li, Jian-Zhong↗
Control Design of Series-connected PV-powered Grid-forming Converters via Singular Perturbation
We report modular architectures that consist of several series-connected dc-ac converters have been a focal point of recent innovations in transformerless medium-voltage applications. In this paper, we consider an architecture consisting of dc-ac modules containing a quadruple active bridge dc-dc converter, which generates three floating dc links that feed grid-side dc-ac inverters. Practical implementation of such a converter module in PV systems requires a variety of controllers that collectively achieve maximum power point tracking, dc-link regulation, and ac-side power control. Design of such multi-loop systems is generally quite challenging due to the potential for destabilizing interactions among loops. Here we propose a design approach where singular perturbation theory is used to decompose the timescales at which each control loop operates and provides a systematic framework for parametric selection. Our approach also ensures system stability of multiple modules with identical controls connected in series across a grid. The paper concludes with experimental results of three 1000 W series-connected converter modules across a stiff grid.
24 POWER TRANSMISSION AND DISTRIBUTION↗