This paper presents the development and validation of a computation model of a cascaded multilevel power inverter as an initial step toward creating a high-fidelity digital twin. A preliminary overview of the cascaded multilevel inverter topology is provided, followed by introducing a mathematical modeling approach that uses graph theory to derive the system's nodal equations. The computation model is implemented in a programmable environment, and its output is compared to the MATALB/Simulink-based simulation, which serves as a reference for performance evaluation. The evaluation is performed using the mean square error (MSE) metric to quantify the accuracy of the proposed model. Results indicate a close agreement between the computation model and simulation data, confirming the model's potential for integration into future real-time digital twin architectures for power converter control and diagnostics.

The rapid increase in electricity demand and peak load consumption has led to rising energy costs and grid instability. This paper proposes an adaptive control strategy for peak shaving, integrating energy storage (ES) and electric vehicles (EV) with real-time power supply-demand monitoring. The proposed system dynamically estimates household demand, including EVs as a load, and adjusts ES and EV charging and discharging schedules based on energy availability, load conditions, and time-of-use (TOU) pricing. By leveraging photovoltaic (PV) generation, surplus energy is stored in the ES and EV during low-demand periods and discharged during peak-demand hours, thereby reducing grid dependency and electricity costs. A real-time simulation model is developed to validate the effectiveness of the proposed strategy. The results demonstrate significant improvements in load balancing, cost reduction, and peak-shaving efficiency, ensuring optimal utilization of renewable energy sources and storage assets.

The building integrated photovoltaic (BIPV) systems are a popular option for integrating renewable energy sources in the power system, and for users to reduce energy bills. This paper analyzes the performance of inverters in BIPV systems with oversized PV configurations. Oversizing PV systems has become a common practice to optimize energy production, particularly in periods of low sunlight, but it raises concerns about efficiency, power quality, and potential economic implications. Performance analysis is performed on two inverters, one operating under an overloaded regime due to the oversized PV installation and another under normal conditions. Several performance metrics are compared, including efficiency, thermal behavior, THD, and economic factors. The results demonstrate that although oversizing can slightly increase the inverter’s temperature and affect power quality, the efficiency was better for the overloaded inverter, although the investment costs have increased. These results offer practical insights for designing PV systems, showing that oversizing can be beneficial if properly managed.

The consumers with building integrated photovoltaic (PV) systems have become prosumers, and their profit depends on network regulations, especially in the treatment of surplus electricity. Net-metering and feed-in tariff are the most common remuneration mechanisms for prosumers. Increasing the number of prosumers can cause various technical problems in the grid, therefore the distribution system operator sometimes imposes legal/regulatory and technical restrictions that are reflected in zero energy export. Integration of the energy storage systems can help with problems arising from these restrictions, but will make the initial investment significantly more expensive. This may negatively affect the profitability of investment. The main aim of this paper is analysis of different regulatory policies and their impact on building integrated PV system profitability. Two profitability metric factors were calculated for the purpose of better policy comparison. For the presented analysis, real data sets of a load demand and PV energy production were used. As an example, the integrated PV system installed at the Faculty of EE University of Sarajevo is analyzed.

Building integrated microgrids (BIMs) present a promising step towards a more efficient, decentralized and sustainable power system. Many buildings already have various renewable energy sources (RES) integrated, but the next step is adding energy storage (ES) systems, or proactive loads such as electric vehicles (EVs) to an already established system. However, ensuring the resilience of the system to accept these new elements presents a challenge in terms of stability, efficiency, and operational capability. This paper focuses on size optimized BIM simulated on Typhoon Hardware-in-the-Loop (HIL) platform using real measured load and PV production data. A rule-based energy management system (EMS) is proposed and its effective-ness is analyzed through testing resilience of the system under consideration. Performance analysis is conducted by adding an EV and assessing system response in several scenarios of load and EV use profiles. Through Typhoon HIL simulations the power profiles of system elements are analyzed, leading to conclusions on BIM performance.

Building integrated microgrids and building integrated photovoltaic systems (BIPV) are emerging as a promising avenue for seamlessly integrating small scale renewable energy sources (RES) into the grid. Challenges arise as new ideas are being explored and implemented in this area, and one of them is maximizing self-consumption and self-sufficiency, for any energy policy, but especially while adhering to zero energy export (ZEE) policy restrictions. As a solution to enhance the utilization of BIPV system this paper proposes a load management (LM) technique. By combining on-grid photovoltaic (PV) system with controllable loads, this paper demonstrates how proactive LM can increase self-consumption and self-sufficiency factors, as well as mitigate PV produced energy dumping due to ZEE restrictions. A case study in the wood sector's industrial building illustrates the efficiency of this approach, showcasing reduced reliance on grid power during sunny periods and increased self-sufficiency through strategic load scheduling. Real-world data analysis validates the effectiveness of LM in aligning PV generation with building energy demands, offering insights into its potential for broader adoption in the renewable energy sector.

Direct current (DC) power systems are gaining interest in the last decade due to increased utilization of DC outputted power sources, DC based energy storage (ES) elements and DC inputted loads. Microgrids are also becoming widely researched as the main foundation of smart grid. It is therefore logical to try to utilize DC microgrid (DCMG) concepts in organization of power systems in wide range of applications. DC microgrids have several important advantages compared to alternating current (AC) microgrids. The control system is essential in order to keep DCMG operating properly, reliable and efficient. Their control structures, with special interest in hierarchical control are explored and compared in this paper in terms of architecture and techniques. This paper presents real world applications using DCMG concept. Future research propositions given in the final chapter can be used as a foundation for researchers exploring the area.

A building-integrated microgrid (BIM) has been a widely utilized concept in low-carbon smart cities. The key advantages of microgrids are using locally available renewable energy sources (RES) and reducing dependency on fossil fuels. Solar photovoltaic (PV) systems and battery storage systems play a crucial role in BIM to achieve desired goals. Due to legal/regulatory and technical restrictions, the distribution system operator (DSO) often imposes zero energy export (ZEE) for these microgrids. Therefore, the sizing of solar-battery systems in BIM, which will be technically feasible and economically optimized, is a challenge for designers, owners and DSO. The objective of this paper is to show the practical approach for design and sizing a microgrid for public buildings using the real data sets of a power consumption and solar energy production. As an example, the BIM for the Faculty of Electrical Engineering, University of Sarajevo is presented.

Abstract Simulation of unsteady flow of SF6 gas in a simplified high-voltage circuit breaker model describing the nozzle, contacts and their nearest surrounding is presented. SF6 is considered as viscous, compressible, real gas described by Redlich-Kwong model. Heat transfer is taken into account due to the gas compressibility. The heat source, triggered by the electric arc between the contacts, was out of the scope of the current research, thus it was not included in the simulations presented. Turbulence, caused by the gas viscosity, is described using realizable k-ε model. In the simulation model, one of the contact sides – electrodes, is considered as moving at prescribed velocity. The part of the space ‘swept’ by the moving electrode is considered as the gas with imposed artificially increased viscosity in order to imitate the rigid body behaviour. Thus, no moving parts of the computational mesh are used in the model. The conservation equations of mass, momentum and energy, given in integral form, are solved using a finite-volume method on unstructured computational grids.