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The main purpose of the solar photovoltaic power plant (SPVPP), with installed power of 500 kW on the roof of the factory GRUNER Serbian Ltd in Vlasotince, is to electrical supply of consumers in the factory. Considering the geometric dimensions of the roof and the daily and monthly profiles of electricity consumption in the factory, at the beginning of 2021, SPVPP was designed. In this way It is achieves parallel operation with the electricity distribution network, with the possibility of delivering surplus electrical energy. SPVPP was performed by the company CONSEKO Ltd., Belgrade in the period 15.0715.10.2021 and was put into trial operation at the end of September 2021, and the use permit of the plant for operation was issued on 30.12.2021. Since that date, SPVPP has been officially in exploitation operation. The GRUNER factory is on March 30, 2022 concluded with JP EPS, Branch "EPS Snabdevanje" concluded a contract for full supply of electricity for the period 01.04.2022 to 31.12.2023. The paper presents some key experiences from the construction and operation of PVPP, which could be interesting for both designers and implementers. The realization of PVPP has made a certain contribution to the promotion of renewable energy sources and the use of "green" energy in the territory of the Republic of Serbia.

The paper presents the most important measurements related to the vertical vibrations characterization of the bucket wheel boom (BWB) of excavator in the coal delivery system at Thermal Power Plant „Nikola Tesla"-B. The position of the BWB was measured, as well as the pressures above and below the piston on the hydraulic cylinders for his vertical movement. Based on this measurements, vibration analysis was performed and the dominant oscillation modes were detected with frequencies of 0.5 [Hz] (for the case of the BWB operating mode when is performed being coal grip) and 0.59 [Hz] (for the case with the BWB when rising in the air). Based on these values and the known speeds of raising and lowering the BWB, the vibration amplitudes were determined. Among other things, the analysis and determination of the period of damped oscillations of the BWB proved to be very important for determining his equivalent moment of inertia. Based on the obtained measurements and analysis of vibrations, all the lacks of the existing system were noticed and a new solution of the BWB electro-hydraulic drive was designed, which was at the end successfully realized. The results presented in this paper are part of the project "Reconstruction of the electro-hydraulic drive of the BWB on TPP Nikola Tesla -B", which was done in August 2017, system implementation, commissioning and exploitation testing the BWB electro-hydraulic drive were done in mid-December 2017, since when the complete system has been in use at the coal delivery system.

The paper presents a practical realization of digital voltage control of a synchronous "buck-boost" power converter, with a wide range of input voltage changes. The power converter is adapted to the power from input solar panels and for different types of output loads. The paper analyzes the basic principles of above mentioned power converter in continuous conduction mode. Also, the paper presents a control strategy based on the PIC18F4520-MICROCHIP microcontroller. All measuring signals (input and output voltage, as well as output current) are connected to the input of the digital controller via galvanically isolated measuring circuits, with appropriate A/D conversion. Finally, some of the most important experimental results obtained during testing of the synchronous „buck-boost" power converter at different input voltages and different output loads are presented.

The Surveillance, Alert & Warning System (SAWS) is used for surveillance and warning about the potential causes of public dangers in specific areas. The system acquires all the necessary data which represent the state of objects which might cause the potential emergency and dangers, and in case that an emergency situation arises, the system is used for general, partial or selective warning of the population in the endangered area about the danger’s occurrence and its cease. The SAWS which is very important, is managed from the Command and Control Center (CCC). The importance of this system is evidenced by the fact that it has data transmission on two transmission paths (WiFi and UHF). The role of uninterruptible power supply (UPS) is very important, because in case of loss of mains power 230V, 50Hz, it should take over the power. The control system should provide a very fast switch to the backup power supply without interruption and voltage failure of the SAWS. The implemented UPS system consists of the following the most important elements: (1) mains charger with PFC, (2) battery bank, (3) inverter and (4) electronic fast static switch. In case of loss of mains power, the required duration of independent operation, i.e. autonomy of the system is about 24 hours. The paper will present the results of design and implementation, as well as the key experimental results obtained during the testing of the power supply system and it’s commissioning in exploitation.

Power electronics devices and modules that are most often used in power supply systems when compared to the passive components usually exhibit a very poor ability to withstand surge voltages. These surge voltages can be of different origins, and in most cases are transient surges. The recorded surge voltages even at low levels can lead to a damage of the mentioned power electronics devices or power converter components. Consequently, it is very important to implement a number of measures to increase the insulation level of the entire system. In this paper the two representative examples of insulation coordination are elaborated: i) an industrial AC drive and ii) photovoltaic inverter used in solar grid-connected power systems.

Insulation coordination in the field of power electronics has become a very important issue. It certainly deserves the attention of both designers and users of various topologies of power converter modules and devices. Over decades of experience in this area, a lot of experiential and practical data has been collected and documented in several key standards. The paper presents the basic terminology and basic types of insulation used in modern power converters, as well as an overview of relevant standards. Except being important for designers, the insulation coordination of the power converters has become also a very important issue for users.