Research on low-voltage single-phase AC electronic loads with variable power factors based on SOGI-FLL

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.