Michal Kolcun

The continuous rise in electricity consumption and the integration of renewable energy sources into distribution grids are gradually posing challenges to conventional protection systems. This trend significantly impacts traditional centralized methods of electricity generation, shifting towards local production and consumption and moving closer to emerging microgrids. This aspect was specifically considered during the development of the current power system we utilize. To ensure the successful emergence of microgrids, it's imperative to begin addressing the issue of protecting these renewable energy sources, especially considering that our current devices lack communication or remote-control capabilities. The size of the topology and the number of devices managed at each point in a microgrid will play a crucial role. Therefore, addressing the overall management of individual devices and resources within the microgrid is essential.

This paper provides the assessment of the profitability of investing in household photovoltaic system in combination with a battery storage, either physical or virtual, and the optimal choice of the combination of the ratio of the power of photovoltaic system and the battery storage with respect to the return on investment in local conditions and pricing policies in Eastern Slovakia

Improvement of the principles of the implementation of a hybrid solar-wind system equipped with a battery for self-consumption of a local object, with the control of power consumed from the grid, is considered. The aim is to increase the degree of energy use from renewable energy sources for consumption while limiting the degree of battery discharge, taking into account deviations in the load schedule and generation of energy sources relative to the calculated (forecast) values. The possibility of compensating for deviations in the load schedule and renewable energy sources generation relative to the calculated (forecast) values is shown when electricity consumption decreases and the degree of energy use increases. Compliance of the schedule of the battery state of charge with the calculated schedule is achieved by correcting the consumption of active power according to the deviation of the state of charge with a given discreteness of time. The algorithm of the control was improved by taking into account the measured value of the load power with an increase in the degree of energy use. Also, the use of correction allows you to limit the depth of discharge of the battery at the accepted value. A mathematical 24 h model of energy processes was developed, taking into account the error in estimating the state of charge. The results of the modeling using archival data on renewable sources generation confirm that the proposed solutions are effective. For the considered application with average monthly generation in February, the correction allows reducing electricity consumption by 16–21% and payment costs at three tariffs by 24–27%.

The penetration of renewable energy sources into the electricity distribution network causes changes in power flows, making conventional protection no longer effective. Research suggests that the solution should be the massive deployment of phasor measurement units and a centralised control, monitoring and protection system. But is this system sufficiently ready for widespread deployment in practice? While research on the decentralised system is progressing further while linking it to microgrid applications is less common.

The constantly growing demand for electricity demands both on the installed power of energy sources and on the transmission capabilities of electrical networks. Considering the fact that increasing the transmission capabilities of electrical networks by building new lines is a time and financially demanding process, network operators strive to use the transmission capacities of existing lines as much as possible. One of the possibilities of this maximum use of existing capacities is the application of the calculation of the dynamic ampacity of the lines, when the operators of electric networks know how to determine the maximum load capacity of the lines depending on the current climatic conditions. The presented publication presents a methodology for determining the dynamic ampacity of overhead power lines under different climatic conditions with the subsequent application of this methodology to a specific conductor used in the implementation of overhead transmission lines.

Many problems arise in the operation of photovoltaic systems. Each of these problems affects the operation of photovoltaic systems by reducing the power of the entire system. Some problems can be avoided during the design of photovoltaic systems. For example, when designing photovoltaic systems, it is possible to eliminate the shading of photovoltaic panels from surrounding objects. It is also necessary to look at the shading from neighboring photovoltaic panels when designing photovoltaic systems. It is necessary to calculate the inclination of the sunlight based on the position of the sun and calculate the distance between the two panels accordingly. However, some problems appear during the operation of photovoltaic systems. These problems can be partially eliminated. The magnitude of the series resistance can be eliminated by reducing the transition resistance throughout the system. The paper describes these problems and their possible solutions in practice. In the practical part, we focused on simulations and experiments in the field of photovoltaic systems (PV). The simulations focused on both the influence of temperature and the series resistance of photovoltaic panels on the production of electricity. The experiments were focused on the influence of various faults/defects on the power and V-A characteristics of photovoltaic panels connected in strings. The paper also discusses the impact of bypass diodes on the operation of photovoltaic systems and determines the need to use bypass diodes.

The implementation of the planned power generation into the grid for a photovoltaic system with a battery is considered using the example of the accepted load schedule of a local object. Generation is carried out during peak hours at a constant power in time, taking into account the limit. The parameters are selected according to the average monthly generation of a photovoltaic battery for its location. Control with reference of active power uses a short-term forecast.

Further research and development in the field of microgrids and related modelling and testing will be necessary for successful application in practice, which will require various model elements. It will be possible to create near-real test microgrids to help better understand the behaviour of such grids. For this reason, it is necessary to develop elements of independent parts that appear in distribution networks that will experience conversion to microgrids in the future. Therefore, this article will describe and propose models of basic protection relays, whose potential for application in microgrids is high. The article will additionally provide models of some power supplies that will be found in such reconstructed new grids.

This work aimed to improve how the equipment of a grid-tied solar-wind system used the installed power of the storage battery while reducing the cost of electricity consumed by a local object from the grid. A method for calculating the parameters for a given load schedule is proposed, along with the value of the reduction in electricity consumption. Values for the power generation of a wind generator and photovoltaic battery are based on archival data. The possible power ratio of the wind generator and the photovoltaic battery is 1:8.33. The formation of the state of charge of the battery involves: a calculation of its value for the morning peak according to the forecast for the next day; adjustable discharge in the evening with full or partial compensation for the load consumption according to the forecast for the next day; a night charge with a given current value. At a one-tariff plan, one battery discharge cycle per day is used. A night charge from the grid is not used. With a two-tariff plan and the use of a night battery charge from the grid, one discharge cycle is used in the spring-summer-autumn period. The simulation confirms the possibility of reducing electricity costs by 2.9 times in winter, which corresponds to the set value, alongside a complete elimination of costs in summer.