Analytical Evaluation of Surface-Mounted PMSG Performances Connected to a Diode Rectifier

This paper analyzes some operational issues of threephase surface-mounted permanent magnet synchronous generators (PMSGs) connected to a diode rectifier. This simple configuration coupled to a single-switch dc–dc converter is used in smallscale wind energy conversion systems, as well as in energy harvesting systems, to reduce costs. The diode rectifier causes an intrinsic limit for the maximum convertible power, which is related to the load impedance matching, and additional joule losses due to the distorted currents. By using an analytical steady-state model of the rectifier and of the PMSG, this paper discusses how to achieve two particularly meaningful operating conditions characterized respectively by the maximum power transfer and the maximum power per ampere. The theory is validated by simulation and test results on a prototype

An analysis of the thermal interaction between components in power converter applications

Accurately predicting the temperature of semiconductor devices is very important in the initial design of power electronics converter. RC thermal models derived from well-known methods have some ability to predict the temperature. However, the accuracy is boundary condition specific, hence, these methods cannot be used in the reliability analysis. To make the thermal model more accurate and robust the factors contributing to discrepancies need to be analyzed carefully. These are power-module-materials’ non-linear properties, thermal grease layer and the cooling system (i.e., liquid-cooled cold plate). In this work, estimation of accurate RC parameters from FEA thermal model is demonstrated in COMSOL. The electrical model having temperature dependent power loss model is coupled to refined thermal model and solved in a circuit simulator, PLECS. The proposed method is applied in two applications: assessing thermal interaction between IGBTs and anti-parallel diodes in a half-bridge power module, and assessing thermal interaction among the discrete switches in an interleaved bidirectional DC-DC converter. Results show that the impact of material non-linearity, thermal grease layer and cooling boundary conditions are significant for accurate prediction of IGBT and diode temperatures. The proposed model is consistent to FEA results and differs by 2-6.5% comparing to the experimental results

Living with COVID-19 and preparing for future pandemics: revisiting lessons from the HIV pandemic

In April, 2020, just months into the COVID-19 pandemic, an international group of public health researchers published three lessons learned from the HIV pandemic for the response to COVID-19, which were to: anticipate health inequalities, create an enabling environment to support behavioural change, and engage a multidisciplinary effort. We revisit these lessons in light of more than 2 years’ experience with the COVID-19 pandemic. With specific examples, we detail how inequalities have played out within and between countries, highlight factors that support or impede the creation of enabling environments, and note ongoing issues with the scarcity of integrated science and health system approaches. We argue that to better apply lessons learned as the COVID-19 pandemic matures and other infectious disease outbreaks emerge, it will be imperative to create dialogue among polarised perspectives, identify shared priorities, and draw on multidisciplinary evidence