Andrzej Firlit

The article analyses the hosting capacity of low-voltage (LV) power grids for connecting distributed energy sources (DER), mainly photovoltaic installations (PV), considering technical limitations imposed by power system operating conditions. The main objective of the research was to develop a simple equation that enables the quick estimation of the maximum power of an energy source that can be safely connected at a given point in the network without causing excessive voltage rise or overloading the transformer and line cable. The analysis was performed on the basis of relevant calculation formulas and simulations carried out in DIgSILENT PowerFactory, where a representative low-voltage grid model was developed. The network model included four transformer power ratings (40, 63, 100, and 160 kVA) and four cable cross-sections (25, 35, 50, and 70 mm²), which made it possible to assess the impact of these parameters on grid hosting capacity as a function of the distance from the transformer station. Based on this, the P_HCI indicator was developed to determine the hosting capacity of a low-voltage network, using only the transformer rating and the length and cross-section of the line for the calculations. A comparison of the results obtained using the proposed equation with detailed calculations showed that the approximation error does not exceed 15%, which confirms the high accuracy and practical applicability of the proposed approach.

Magazynowanie energii odgrywa kluczową rolę w procesie transformacji energetycznej, umożliwiając efektywną integrację odnawialnych źródeł energii, zwiększenie elastyczności systemów energetycznych oraz poprawę niezawodności dostaw energii. W artykule przedstawiono wybrane kierunki badań prowadzonych w Akademii Górniczo-Hutniczej w Krakowie koncentrujących się na zagadnieniach związanych z magazynowaniem energii i funkcjonowaniem magazynów. Część rozdziałów zawiera niezależne opracowania dotyczące szerokiego spektrum zagadnień technologicznych i inżynierskich. Obejmują one aspekty elektrochemiczne, materiałowe, cieplne, geotermalne, mechaniczne oraz elektroenergetyczne. Artykuł ma charakter interdyscyplinarny, aplikacyjny i wdrożeniowy, podkreśla znaczenie prowadzenia badań nad rozwojem i integracją nowoczesnych technologii magazynowania energii oraz innowacyjnych rozwiązań technicznych z potrzebami i wyzwaniami współczesnych systemów elektroenergetycznych.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

The paper presents the propagation assessment and power quality parameters improvement system in power distribution grid. In this work main functionalities of the system are described focusing on the individual assessment module. The module is using CIRED/CIGRE C4.109 method which is based on the 10-minutes aggregated data. Three cases of individual emission assessment using real measurement data in the distribution system operator environment ware analyzed. The obtained results confirmed the legitimacy of using 10-minute data to assess the emissions of harmonics.

Over the last few years, a dynamic increase in the installed capacity of distributed energy sources has been observed, with the largest share being photovoltaic sources. The power grid is a system of connected vessels, and changing the structure of electricity production has a specific impact on the operation of this network, which makes it necessary to study the impact of the sources on the power system. The current and projected increase in the number of connected installations will make the issues of interaction and cooperation of distributed sources with the network extremely important. The article presents an analysis of the impact of a photovoltaic farm on selected parameters of the quality of electricity supply. This analysis was made on the basis of simulation results in a computer program and measurement tests carried out on a real photovoltaic farm with a capacity of 1.8 MW connected to the medium voltage power grid. The impact of the farm-generated power on the values of fundamental indicators of the quality of electricity supply, such as voltage deviations, voltage asymmetry factors, and voltage distortions factors, is presented. These relationships were determined based on the correlation and regression analysis of individual electrical quantities.

W artykule podsumowano obrady jednej z sesji I Kongresu Energetyki Rozproszonej dotyczącej innowacyjnych rozwiązań technicznych i technologicznych w obszarze energetyki rozproszonej. Ten szeroki i wielopłaszczyznowy temat dotyczy istotnego aspektu trwającej właśnie transformacji energetycznej oraz silnie wiąże się z rozwojem i wdrażaniem inteligentnych systemów elektroenergetycznych smart grids.

W artykule podjęto próbę przedstawienia współczesnych trendów i wyzwań w obszarze jakości dostawy energii elektrycznej w kontekście rozwoju inteligentnych systemów elektroenergetycznych oraz energetyki rozproszonej. Tematyka ta jest bardzo szeroka i wieloaspektowa, szczególnie ze względu na transformację energetyczną, w której uczestniczymy. Autorzy artykułu, członkowie Zespołu Jakości Energii Elektrycznej AGH, brali udział w realizacji wielu prac naukowo-badawczych, eksperymentalno-rozwojowych, dydaktycznych w ramach krajowych i międzynarodowych projektów. Związane one były ze współpracą z energetyką zawodową (OSD, OSP), przemysłem oraz instytucjami działającymi na rzecz rynku energii. Przedstawiono skrótowo przykładowe, wybrane zagadnienia.

This paper presents the electrical system factors having an influence on the work efficiency and performance of the LC passive harmonic filters (PHFs). Such filters are very often used in industries for the purpose of harmonics mitigation and reactive power compensation. Before their installation in the electrical system, many investigations should be performed in order to ensure their good design as well as work efficiency after connection. In this paper, the factors having an influence on the PHFs work efficiency and performance, such as the grid short-circuit power, primary grid voltage spectrum (voltage measured at the PCC before the filter connection), load reactive power and current characteristic harmonics, manufacturer filter parameters tolerance and filter-detuning phenomena are investigated. Most of the quoted factors are mentioned in the literature, but the novelty of this paper is that, based on the case study example of the single-tuned filter investigated in the laboratory, the influence of those factors on the filter work efficiency are demonstrated, and some solutions and recommendations are proposed. The studies are focused on the design of the single-tuned filter in the laboratory, and some simulation results are presented as well.

This paper presents an algorithm for finding the optimal control for a current controller that operates as a part of a control system of a shunt active power filter. The algorithm is based upon the Karush–Kuhn–Tucker conditions for finding an optimal value where control signal is limited and constraints create a cube. The explicit solution of the Karush–Kuhn–Tucker problem is presented and simplified calculations are given to lower calculation complexity. The presented Karush–Kuhn–Tucker algorithm is compared with a classical PI controller. It is given the algorithm for finding the optimal parameters of the PI controller and the behavior of the PI controller is compared with the presented algorithm. Attention has been paid to the saturation of controllers in commutation states of load currents, which has a negative impact on the final performance of the controllers and the controlled shunt active power filter. The paper also presents the software and hardware platforms applied to run the presented algorithms in real-time. For both controllers, the shunt active power filter response is shown using real experimental results. The results of the experiments prove better behavior regarding the presented algorithm, especially in the case of commutative load currents, where the output signals from other controllers become saturated.

Monitoring power quality (PQ) indicators is an important part of modern power grids’ maintenance. Among different PQ indicators, flicker severity coefficients P_st and P_lt are measures of voltage fluctuations. In state-of-the-art PQ measuring devices, the flicker measurement channel is usually implemented as a dedicated processor subsystem. Implementation of the IEC 61000-4-15 compliant flicker measurement algorithm requires a significant amount of computational power. In typical PQ analysers, the flicker measurement is usually implemented as a part of the meter’s algorithm performed by the main processor. This paper considers the implementation of the flicker measurement as an FPGA module to offload the processor subsystem or operate as an IP core in FPGA-based system-on-chip units. The measurement algorithm is developed and validated as a Simulink diagram, which is then converted to a fixed-point representation. Parts of the diagram are applied for automatic VHDL code generation, and the classifier block is implemented as a local soft-processor system. A simple eight-bit processor operates within the flicker measurement coprocessor and performs statistical operations. Finally, an IP module is created that can be considered as a flicker coprocessor module. When using the coprocessor, the main processor’s only role is to trigger the coprocessor and read the results, while the coprocessor independently calculates the flicker coefficients.