With the expansion of renewable energy sources, the stable and high-quality operation of microgrids composed of new energy sources has attracted widespread attention. Among them, the power conversion system (PCS), as an important part of microgrids, plays a crucial role in their operation and management. The PCS operation modes are classified into grid-connected and off-grid modes. However, in off-grid mode, due to the access of nonlinear and unbalanced loads, the output voltage quality of a PCS is worse, and the voltage waveform distortion is serious. To solve these problems, a fast repetitive control (FRC) strategy is proposed for a power conversion system with an Active Neutral Point Clamped (ANPC) architecture of three levels. The voltage loop control strategy can be applied to the voltage/frequency ($V/f$) mode and the grid-forming mode. The control strategy can effectively realize the suppression of the harmonics of the output voltage and has a 100% capability to carry unbalanced loads. Finally, a 1725 kVA PCS prototype is developed, and the proposed control strategy is verified using the MT3200 HIL semiphysical simulator of ModelingTech in the $V/f$ mode as an example. This practically verifies the feasibility and validity of the proposed control strategy, which has a certain degree of engineering practicability and reference due to the simplicity of the design and the ease of realization.

This paper proposes a hierarchical current-limiting strategy for power conversion systems oper-ating as grid-forming virtual synchronous generators (VSGs). The strategy coordinates adaptiveactive/reactive power reference reconstruction, transient virtual impedance (TVI), and circularcurrent-vector limiting so that the converter can suppress fault current while retaining voltage-source behavior as far as the hardware constraints allow. The final stability and ride-through capability are evaluated through a 10-kVA hardware prototype under islanded load steps, overload operation, grid-connected frequency disturbance, and single-phase, two-phase, three-phase, and phase-angle-jump fault scenarios. Comparative tests with a conventional virtual-impedance-plus-current-limiting method show that the proposed hierarchical coordination reduces fault-entry and fault-clearance current transients and improves post-fault recovery. The results demonstrate that staged coordination among power limiting, TVI, and direct current limiting provides a practical solution for grid-forming VSGs with limited overcurrent capacity.

This study presents the first peer-reviewed multi-year field performance analysis of an operational 50 kWp monocrystalline photovoltaic (PV) system installed at Andijan State Technical Institute (ADTI, 40.78°N, 72.34°E), Uzbekistan, covering 40 months of Growatt-platform monitoring data from January 2023 through April 2026. The 2024 full-year reference dataset reveals an annual PV yield of 61,945 kWh (specific yield: 1,239 kWh/kWp/year; annual average capacity factor: 14.1%), establishing the first field-validated solar resource benchmark for the Andijan region. A critical seasonal asymmetry is quantified: summer months (June–August) yield an average 8,797 kWh/month compared to 675 kWh/month in winter (December–February), a 13.0× ratio that fundamentally governs hydrogen storage strategy. Coupling the measured PV data with experimentally validated alkaline water electrolysis parameters for 316L stainless steel electrodes — characterized across 1,000 hours of continuous operation in our prior publications — annual hydrogen production potential is quantified at 178.6 kg/year (current 9.6% energy efficiency) and 520.9 kg/year (improved 28% efficiency through NiFe catalyst, zero-gap architecture, and 70°C operation). Minimum seasonal hydrogen storage of 32.6 kg is required for uniform year-round supply continuity. Techno-economic analysis yields levelized cost of hydrogen (LCOH) of $1.3/kg (current) and $0.67/kg (improved system) at campus scale, falling to $0.4/kg at 1 MW scale. Over the 40-month measurement period, the ADTI system has avoided 63.1 tonnes of CO₂ emissions. Multi-year data confirm resource stability with year-on-year summer peak yields in the two most stable comparable months (April Δ = +1.1%; May Δ = +5.2%), validating the 2024 dataset as a representative regional benchmark. These results provide the first evidence-based foundation for solar hydrogen feasibility planning in Uzbekistan, directly supporting the country’s raised 40% renewable electricity target by 2030.