An Improvised Low Voltage Ride Through Technique for the Robust Power Control of PMSG Systems Feeding Weak Grid

Abstract

Grid-connected PMSGs exhibit significant sensitivity to unbalanced grid voltages, particularly during voltage sags, which introduce negative sequence components that lead to undesirable oscillations in grid currents, active/reactive power, and DC link voltage at twice the grid frequency.  This study aims to enhance the dynamic performance of PMSGs under such adverse conditions by developing a novel reference current generation strategy that mitigates these fluctuations without relying on dual vector control. The approach estimates the stator flux angular frequency in the α–β frame using voltage and current signals, eliminating the need for a PLL or voltage differentiation. The MSC manages active power, while the GSC maintains constant DC link voltage and UPF. Extensive simulations and real-time validation using OPAL-RT OP4510 demonstrate the scheme’s robustness. For instance, in Case I, oscillations in active power, reactive power, grid current, and DC voltage were reduced from 12.05%, 4.22%, 13.07%, and 0.422% to 0.497%, 1.73%, 7.37%, and 0.0152%, respectively. In Case IV with a severe phase-A fault, oscillations dropped from 86.56% to 12.32% in active power and from 87.23% to 32.23% in grid current. Across all test cases, total harmonic distortion in grid current was consistently brought below 5%, proving the method’s superiority over conventional techniques. Simulations conducted on a 2.5kW PMSG under various unbalanced grid voltage conditions using PSCAD/EMTDC confirm the suggested method's efficacy and its edge over current control techniques.