A Grid-Connected Multilevel Converter for Interfacing PV Arrays and Energy Storage Devices

This paper presents a design procedure and a \ud control strategy for a grid-connected single-phase multilevel \ud converter. The proposed system uses two series connected H-bridge modules, one fed by photovoltaic panels, the other by \ud energy storage devices. The former switches at line frequency, \ud while the latter operates in PWM. The system is designed to \ud minimize the voltage stress on the switches, while the control \ud strategy is such that a constant active power is delivered to the \ud grid with high power factor, even if the energy produced by the \ud photovoltaic panels is variable. The paper illustrates the power \ud converter design procedure, the hybrid PWM method and the \ud small signal modeling used to design the controllers of each \ud inverter. In addition, the performance of the multilevel converter \ud is verified by means of simulation and experimental results, \ud which show the system ability to operate as expectedFAPES

Fast System to measure the dynamic on‐resistance of on‐wafer 600 V normally off GaN HEMTs in hard‐switching application conditions

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Minimal Extrathyroidal Extension in Predicting 1-Year Outcomes: A Longitudinal Multicenter Study of Low-to-Intermediate-Risk Papillary Thyroid Carcinoma (ITCO#4)

Background: The role of minimal extrathyroidal extension (mETE) as a risk factor for persistent papillary thyroid carcinoma (PTC) is still debated. The aim of this study was to assess the clinical impact of mETE as a predictor of worse initial treatment response in PTC patients and to verify the impact of radioiodine therapy after surgery in patients with mETE. Methods: We reviewed all records in the Italian Thyroid Cancer Observatory (ITCO) database and selected 2237 consecutive patients with PTC who satisfied the inclusion criteria (PTC with no lymph node metastases and at least 1 year of follow-up). For each case, we considered initial surgery, histological variant of PTC, tumor diameter, recurrence risk class according to the American Thyroid Association (ATA) risk stratification system, use of radioiodine therapy, and initial therapy response, as suggested by ATA guidelines. Results: At 1-year follow-up, 1831 patients (81.8%) had an excellent response, 296 (13.2%) had an indeterminate response, 55 (2.5%) had a biochemical incomplete response, and 55 (2.5%) had a structural incomplete response. Statistical analysis suggested that mETE (odds ratio [OR] 1.16, p=0.65), tumor size >2 cm (OR 1.45, p=0.34), aggressive PTC histology (OR 0.55, p=0.15), and age at diagnosis (OR 0.90, p=0.32) were not significant risk factors for a worse initial therapy response. When evaluating the combination of mETE, tumor size, and aggressive PTC histology, the presence of mETE with a >2 cm tumor was significantly associated with a worse outcome (OR 5.27, 95% CI, p=0.014). The role of radioiodine ablation in patients with mETE was also evaluated. When considering radioiodine treatment, propensity score-based matching was performed, and no significant differences were found between treated and non-treated patients (p=0.24). Conclusions: This study failed to show the prognostic value of mETE in predicting initial therapy response in a large cohort of PTC patients without lymph node metastases. The study suggests that the combination of tumor diameter and mETE can be used as a reliable prognostic factor for persistence and could be easily applied in clinical practice to manage PTC patients with low-to-intermediate risk of recurrent/persistent disease

Reduced redundant power processing concept: A reexamination

The Reduced Redundant Power Processing (R2P2) concept was introduced in literature with the aim of improving the overall conversion efficiency of two-stage high-quality rectifiers, capable of providing high power factor and tight output voltage regulation, but it has been applied to DC-DC conversion too. The idea is to have one converter processing only a fraction of the total output power, the remaining part coming directly from the other converter or, in DC-DC converter applications, directly from the input source. This idea, that is at first sight very appealing, has been implemented in different ways using basic converter topologies. In this paper, it is demonstrated that most of the R2P2 implementations that have been proposed in literature are actually not able to achieve a better efficiency compared with a full power processing, because they do not represent a correct implementation of the concept. Indeed, it is possible to demonstrate that they are equivalent to solutions that process the entire load power. It is demonstrated that it is possible to develop R2P2 structures that achieve better efficiencies compared to the full power processing counterparts, but only at the expense of more complicated topologies, and for specific applications in which the processed power is a tiny fraction of the overall output power

Analysis and Design of the Soft-Switched Clamped-Resonant Interleaved Boost Converter

This paper presents the detailed analysis and design of a soft-switching DC-DC converter called clamped-resonant interleaved boost converter (CRIB). This topology, thanks to a resonant L-C tank connected between the drain terminals of the switches of two interleaved boost cells, achieves zero-voltage and zero current commutations of all devices, independently of the load current, with a reduced dv/dt across the switches, making the converter suitable for high-frequency operation. Moreover, a proper no-load operation is proved, whenever the minimum voltage gain is higher than a given threshold. Differently from previous works on current-fed resonant converters, the presented theoretical analysis includes the effect of the input filter inductors, allowing to derive a simple design procedure to meet the given specifications. According to the outlined design steps, an experimental prototype was built, rated at 42~54 V to 400 V~300 W. Measurements confirm the theoretical predictions, showing an efficiency above 96% at the nominal power in the whole input voltage range. Finally, the possibility to reduce the overall magnetic volume by coupling the two input inductors is demonstrated

A High-Quality Rectifier Based on the Forward Topology with Secondary-Side Resonant Reset

The use of buck-derived topologies for unity power factor ac-to-dc applications is limited by their inherent inability to draw current from the line in those intervals, during the line half period, in which the input voltage is lower than the output one. This drawback is overcome in the proposed high-quality rectifier based on the forward topology with secondary-side resonant reset. The employed secondary side reset capacitor is able to provide proper transformer reset by recycling the transformer stored energy to the load and, at the same time, it allows to draw energy from the line even when the input voltage is lower than the output one. Consequently, besides to a better utilization of the transformer core (bipolar core excitation), a low distorted input current waveform can be obtained with a power factor close to unity. Experimental results of a 200 W prototype confirm the theoretical expectations

Series Resonant Converter with Wide Load Range

A modification of the series resonant converter topology is presented which extends converter operation from no-load to full-load. This result is accomplished by adding two switches at the secondary-side bridge rectifier, thus improving output voltage control. The resonant inverter can be operated either at constant switching frequency, even for the half-bridge topology, or at variable switching frequency. With constant switching frequency, the output voltage is regulated by controlling the switches of the rectifier stage. Soft-switching commutations of all switches are maintained in any operating condition, thus optimizing overall efficiency. The secondary-side control of the output voltage adds another interesting feature to the basic converter, i.e. the step-up and step-down regulation capability which allows the use of this topology in high power factor rectification, too. Simulated and experimental results confirm proper converter operation in the range from no-load to full-load