Electric Spring Using MPUC5 Inverter for Mitigating Harmonics and Voltage Fluctuations

This article introduces a novel configuration of electric spring (ES) based on the modified five-level packed u-cell (MPUC5) inverter for mitigating harmonics and voltage fluctuations at various points of a grid with unstable generated power from distributed renewable energy sources. Immanent merits of the proposed configuration include, but are not limited to, halved dc-links voltages, boost mode operation, the possibility of higher power applications, smooth five-level voltage waveform with low total harmonic distortion (THD) index, the smaller size of output low-pass filter, and low switching frequency. The operation principles, design procedure, and configuration of the MPUC5-based ES (MPUC5-ES) are also presented. Besides, a simple and yet efficient controller without any extra control loop for regulating dc bus voltages has been proposed. Finally, the introduced multilevel ES is tested through extensive simulation and experimental studies to confirm its dynamic and steady-state performances in various operation modes in a weak grid fed by both conventional and intermittent renewable energy sources.