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In order to overcome the drawbacks of the conventional passive loads with constant parameters, single-phase AC electronic loads with the back-to-back topology have emerged. However, in low-voltage and low-power situations, the grid voltage will be affected by harmonic currents and easily distorted. Therefore, a variable power-factor control strategy based on the second-order generalized integrator frequency locked loop (SOGI-FLL) is proposed. SOGI-FLL is adopted to improve the phase locking accuracy under the distorted grid voltage, and the fundamental and quadrature components are obtained, based on which a control scheme is designed to continuously adjust power factors; the power factor angles of rectifier side and inverter side are controlled cooperatively to reduce dc-link oscillations. Experimental results show that, the designed single-phase low-voltage AC electronic load can simulate capacitive, resistive and inductive loads, respectively, and the power factor is continuously adjustable in the range of 0.5~1.0. [ABSTRACT FROM AUTHOR]

1500-V photovoltaic (PV) configuration is the standard design in the solar PV industry. Extending the maximum dc voltage from 1000 to 1500 V can reduce the installation cost of the entire power plant. However, it may affect the reliability of the corresponding 1500-V PV inverters, due to the increased loading stresses, i.e., voltage stress and thermal loading of power devices. In this context, this article proposes a solution to the reliability enhancement of silicon carbide-mosfet-based 1500-V PV inverters with variable gate resistance. This solution offers a possibility to adaptively adjust the switching speed to make a compromise between the switching power loss and voltage overshoot during commutation, thus enhancing the reliability. The evaluation results based on the mission profile of a 125-kW 1500-V PV system installed in Denmark indicate that the PV inverter with the proposed design, i.e., variable gate resistance, can improve reliability performance compared to the fixed gate resistance solution while ensuring a safer operating voltage margin. [ABSTRACT FROM AUTHOR]