Abstract
The increased use of active power electronics for AC to DC conversion of electrical equipment causes emissions in the frequency range between 2-150kHz (Supraharmonic frequency range). Currently two different methods (IEC61000-4-30 and IEC61000-4-7) to measure supraharmonic emissions are used. In this study, the two methods are compared to each other by means of real measured signals. While other studies used synthesized signals, this study investigates real measured signals of a bi-directional electric vehicle (EV) charging station and a photovoltaic (PV) power plant. The signals indicate narrowband, wideband and time-varying emissions. The method described in IEC61000-4-30 Ed.3 offers benefits analyzing wideband emissions due to reduced data. Nevertheless, as the method is non-gapless, big deviations to IEC61000-4-7 and to a gapless method occur. Especially at time-varying signals the deviation reaches up to 50%. The method according to IEC61000-4-30 Ed.3 shows good results for constant level of emissions only. In reality, this is rarely the case, as emissions often get superimposed by other signals. The IEC 61000-4-7 method generates many data, but allows detailed investigations of narrowband emissions and as the measurement is gap-less time-varying emissions are detected properly. © 2022 IEEE.

Abstract
Wastewater treatment systems are major consumers of electricity being responsible for 3 to 5% of global energy consumption, and 56% of greenhouse gas emissions into the atmosphere in the water treatment sector. Climate change currently imposes the definition of a new pattern of human behavior in the defense and sharing of a common space that is the planet, so the optimization of water treatment models plays a crucial role in the definition of sustainability strategies as part of the challenges for decarbonization by 2050. The physical-chemical characteristics of the influent, the treatment techniques and associated technologies and the unpredictability of external phenomena of inefficiency transform wastewater treatment plants (WWTPs) into complex systems, sometimes difficult to understand. The study of energy efficiency plays an important role in the emergence of a standard behavior model, which allows the correction of unbalanced situations in the expected energy consumption. Given the importance of the topic, the present review aims to study energy auditing techniques and benchmarking tools developed for the wastewater treatment sector to reduce the current electricity consumption, which could represent up to 90% of total energy consumption. The result of the research was organized according to the criteria defined for the characterization of auditing techniques and benchmarking tools. A review was conducted from 51 scientific papers from different reference research platforms published in the last 20 years according to the keywords. This literature review has shown that there are, in the classification of consumption reduction, energy auditing and benchmarking tools; energy management techniques and methods directed to the energy efficiency of the treatment stages and specific equipment; and, finally, decision support tools. According to the methodology followed, it was possible to conclude that although the concern is not recent, there are techniques and tools for assessing energy performance more suitable for the wastewater sector. However, the authors recognize that associated with the complexity of wastewater treatment systems, inefficiency phenomena still strongly impact energy efficiency assessment, so the contributions for their identification and quantification may represent an added value for data analysis, systematization, and optimization methodologies.

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