Highlights:Graphical/Tabular Abstract The proposed fast and robust PNS extractor for reference current generation The improving dynamic performances of grid connected RESI by use of PCI controller The providing controllability of activereactive power oscillationsUnbalanced grid voltages include positive and negative sequence (PNS) components. In particular, the negative sequence components that cause oscillations on the control signals, significantly affect the performance of the grid-connected renewable energy source inverters (RESI). In this study, proportional complex integrator (PCI) based current controller is proposed to deal with the disadvantages such as slow dynamic response, steady-state errors and complex structure of the proportional integral (PI) based dual current controller used for the control of grid connected RESI under non-ideal grid voltage conditions. The reference currents based on the active-reactive power reference signals, PNS components and the flexible control parameter are generated for use in control loops. The relationship between the active-reactive power oscillations, which are caused by non-ideal grid conditions, are comprehensively analysed and controlled with a flexible control parameter. An important contribution to similar previous studies is that the PNS voltagecurrent components required for the reference current generation are separated by the proposed fast and robust dual average filter based phase locked loop (DAPLL). The performance of the proposed PCI-based current control strategy is compared and tested with the PI-based dual current control strategy using various case studies.
Results:The performance of the proposed PNS extractor, the PI-based dual-current controller and the PCI-based current controller for the control of the grid-dependent inverter has been tested and verified under various scenarios such as phase to phase grid faults, grid voltage harmonics and variation of flexible control parameter. The effectiveness and availability of proposed test system is verified by using PSCAD/EMTDC software. The proposed system is shown in Figure A.
Conclusion:One of the important contributions of this study is the PNS voltage and current components required for use in the reference current generation with a novel PNS extractor, which is fast, robust and not affected by harmonic components. The results show that the proposed PCI-based current control strategy improves the dynamic response and stability of grid-connected RESI, minimizing current errors and harmonic components.
