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This study covers a self-powered wireless communication system that is powered using a piezoelectric energy harvester (PEH) in a shoe. The lead-zirconate-titanate (PZT) ceramic of the PEH was coated with UV resin, which (after curing under UV light) allowed it to withstand periodic pressure. The PEH was designed with a simple structure and placed under the sole of a shoe. The durability of the PEH was tested using a pushing tester and its applicability in shoes was examined. With periodic compression of 60 kg, the PEH produced 52 μW of energy at 280 kΩ. The energy generated by the PEH was used to power a wireless transmitter. A step-down converter with an under-voltage lockout function was used to gather enough energy to operate the wireless transmitter. The transmitter can be operated initially after walking 24 steps. After the transmitter has been activated, it can be operated again after 8 steps. Because a control center receives signals from the transmitter, it is possible to check the status of workers who work outside at night or mostly alone, to detect emergencies. [ABSTRACT FROM AUTHOR]

The purpose of this study is to conduct an economic evaluation of a photovoltaic-energy storage system (PV–ESS system) based on the power generation performance data of photovoltaic operations in Korea, and to calculate the optimal capacity of the energy storage system. In this study, PV systems in Jeju-do and Gyeongsangnam-do were targeted, PV systems in this area were assumed to be installed on a general site, and the research was conducted by applying weights based on the facility's capacity. All the analyses were conducted using the actual amount of Korea power exchange (KPX) transactions of PV systems in 2019. In order to calculate the optimal capacity of the power conditioning system (PCS) and the battery energy storage system (BESS) according to global horizontal irradiation (GHI), PV systems with a minimum/maximum/central value were selected by comparing the solar radiation before the horizontal plane for three years (2017–2019) in the location where the PV systems was installed. As a result of the analysis, in Jeju-do, if the renewable energy certificate(REC) weight decreased to 3.4 when there was no change in the cost of installing a BESS and a PCS, it was more economical to link to the BESS than the operation of the PV system alone. In Gyeongsangnam-do, it was revealed that if the REC weight was reduced to 3.4, it was more likely to link to the BESS than the operation of the PV system alone. [ABSTRACT FROM AUTHOR]

High voltage electric power equipment requires rigorous regulation testing to specific standards which ensure proper and safe operation in the grid. Manufacturers conduct these tests in order to prove standard compliance and product liability. Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power converters. Generally, those AC power converters or power supplies require performance validation, burn-in and/or lifetime testing under different load conditions, defined by the end-user or standards for the given applications. For flexible and efficient MV verification testing, this paper presents a five-level multilevel converter-based MV regenerative AC electronic load with one-cycle control (OCC), which is based on five-level diode-clamped multilevel converters with back-to-back structure and can emulate any impedance load. In this paper, especially the dc-link capacitor voltage balance of the proposed multilevel MV regenerative AC load is deeply analyzed. Simulation and experimental results are presented to verify the dc-link voltage balance performance of the proposed multilevel MV regenerative AC electronic load. [ABSTRACT FROM AUTHOR]

This paper presents a new multilevel one-cycle control (OCC) technique for a five-level diode-clamped multilevel converter (DCMC)-based static VAR compensator (STATCOM). The OCC algorithm in combination with multi-carrier level-shifted PWM control is used in the proposed five-level DCMC-based STATCOM. The automatic dc link voltage balance is simply realized by four voltage compensators presented as the part of the OCC controller. In this paper the OCC principle of a two-level converter-based STATCOM is reviewed and extended to the five-level DCMC-based STATCOM. The proposed multilevel OCC control method of the five-level DCMC-based STATCOM in steady-state and dynamic operation modes is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]