Aged and insufficient domestic power plants and insecure, unreliable and expensive power imports pose significant challenges for the power sector of Afghanistan. On the other hand, due to the absence of a suitable transmission grid, the internal renewable energy resources are not adequately developed, despite their abundant resource potential throughout the country. This paper proposes a voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission link to connect the Herat province in the west, which has huge solar and wind energy potential, to Kabul, the capital of the country and the main load center. A techno-economic analysis of this HVDC against high-voltage alternating current (HVAC) technology was performed to determine the suitability and effectiveness of the proposed transmission system. The active, reactive and corona losses were calculated as the technical parameters and the discounted cash flow (DCF) method was deployed to economically compare both technologies. The outcomes of the paper disclose that the implementation of this transmission project is techno-economically feasible, and can result in the energy security and economic stability of the country.

This paper proposes a new and surge-less solid-state direct current (DC) circuit breaker in a high-voltage direct current (HVDC) transmission system to clear the short-circuit fault. The main purpose is the fast interruption and surge-voltage and over-current suppression capability analysis of the breaker during the fault. The breaker is equipped with series insulated-gate bipolar transistor (IGBT) switches to mitigate the stress of high voltage on the switches. Instead of conventional metal oxide varistor (MOV), the resistance–capacitance freewheeling diodes branch is used to bypass the high fault current and repress the over-voltage across the circuit breaker. The topology and different operation modes of the proposed breaker are discussed. In addition, to verify the effectiveness of the proposed circuit breaker, it is compared with two other types of surge-less solid-state DC circuit breakers in terms of surge-voltage and over-current suppression. For this purpose, MATLAB Simulink simulation software is used. The system is designed for the transmission of 20 MW power over a 120 km distance where the voltage of the transmission line is 220 kV. The results show that the fault current is interrupted in a very short time and the surge-voltage and over-current across the proposed breaker are considerably reduced compared to other topologies.

Integrating renewable energy into existing power grids is essential to maintaining a balance between supply and demand. They ensure a stable and reliable energy supply by seamlessly adjusting to the variations in energy production and consumption. This study introduces an innovative approach to achieving energy balance by integrating floating photovoltaic (FPV) systems with hydropower. This combination addresses not only environmental concerns but also the issue of underproduction in hydropower dams. The primary objective is to find the most economical combination of components for a 100% hybrid renewable energy system using a Multi-Objective Genetic Algorithm (MOGA). The integrated system is projected to add 988,508 MWh of electricity to the grid each year, surpassing the required amount needed to meet demand. Despite some energy losses, the contribution of each system is derived from the optimization process, where the FPV system contributes approximately 29% of the total energy produced, while the hydroelectric system provides the remaining 71%. These percentages are based on the modeled energy output of the combined system in the study. The study highlights the consistency and reliability of the FPV source, emphasizing its low cost of energy (COE) and net present cost (NPC). Moreover, implementing a 166.3 MW FPV system significantly reduces 238,739 tons of CO2 emissions. By exploring this approach, ongoing research and development in renewable energy technologies can enhance efficiency, cost-effectiveness, and overall performance, leading to a more robust and sustainable energy balance.

The power transmission system of Afghanistan is witnessing a significant shortage in terms of capacity, reliability, flexibility, and energy security. The goal of this paper was to identify and examine the associated issues, challenges, and opportunities for domestic transmission grid and power imports in the country. On these bases, proposals and recommendations were provided that can help the Afghan energy sector strategically enhance its transmission capacity and make the country's existing massive renewable energy potential exploitation feasible. The focus was on the expansion of high-voltage direct current transmission technology. The findings of the paper revealed that the utilization of high-voltage direct current, hybrid high-voltage alternating current, and high-voltage direct current transmission technologies can facilitate bulk power transmission and trade between south and central Asia, as well as regional energy sustainability, development, and security.