Galvanically isolated voltage measurements are becoming increasingly important for the characterization of converter systems with fast switching Wide-Bandgap (WBG) semiconductors. A very high Common Mode Rejection Ratio (CMRR) > 80 dB for frequencies up to several tens of MHz is required to accurately measure, e.g., the high-side gate-source or drainsource voltage in a half-bridge, or voltages on floating potentials as, e.g., found in multi-level converters. Common to all listed measurement scenarios is the fast changing reference potential, which acts as Common Mode (CM) disturbance. This article derives the minimum necessary CMRR at different frequencies to constrain the time-domain measurement error below a certain limit. Thereby, only the switched voltage and the voltage transition rate (dv/dt) of the CM disturbance are to be considered and not the actual converter switching frequency f sw . Afterwards, a galvanically isolated measurement system with a CMRR > 100 dB up to 100 MHz and an analog measurement bandwidth of 130 MHz is presented. Critical design aspects to achieve this performance are investigated. Compared to commercially available isolated voltage probes, the presented measurement system does not require any additional equipment like an oscilloscope to perform and visualize measurements, since the data is already digitized/sampled and thus can be transmitted directly to a host device (e.g., computer or monitoring system) with corresponding Graphical User Interface (GUI) software. Experimental verification in frequency-and timedomain confirms that the performance is on par with the best commercially available isolated voltage probes.
This paper investigates the Electromagnetic Interference (EMI) noise signature of threephase three-level (3L) Triangular Current Mode (TCM)-modulated grid-tied Photovoltaic (PV) inverters that achieve full Zero Voltage Switching (ZVS) and thus minimal switching losses over the entire mains period and/or ensure > 99 % efficiency. Further required is a very high power density, which facilitates installation and is achieved with high switching frequencies > 100 kHz. The impact of the characteristic variation of f sw in all three phases and the therefore different instantaneous switching frequencies in each phase on the overall converter EMI noise signature is analyzed and it is found that the consideration of only one single phase is sufficient to characterize the noise emissions. Numeric approaches to estimate the detector output of EMI test receivers are compared and it turns out that the peak value of the noise voltage envelope is a useful measure to determine the required filter attenuation, provided the phase-shift of the harmonics is considered in the envelope detection. Finally, a hardware demonstrator of a 6.6 kW, > 99% efficiency threephase 3L-TCM PV inverter with a power density of 6.2 kW/dm 3 (102 W/in 3 ) is designed and the theoretical findings are verified. Moreover, the impact of parasitic capacitances from the switch-nodes and from the floating dc link to Protective Earth (PE) is thoroughly studied qualitatively and quantitatively with the result that these capacitances considerably reduce filter attenuation (35 dB at 150 kHz in the case at hand), requiring sufficient design margin.INDEX TERMS Electromagnetic interference (EMI), triangular current mode (TCM), inverter, dc-to-ac converter, soft switching, zero voltage switching (ZVS).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.