Quality Management of Energy Storage VSG Based on Odd-Order Repetitive Control

As renewable energy integration reduces grid strength, energy storage virtual synchronous generator (VSG) control becomes critical for grid support. However, power quality challenges arise from nonlinear loads and background harmonics in distribution networks. This study addresses energy storage VSG's power quality limitations by proposing a sensor-free selective control strategy to optimize point of common coupling (PCC) voltage or grid current without altering existing VSG structures. An odd-order repetitive control technique reshapes harmonic im-pedance, supported by a grid-VSG harmonic impedance model. Two supplementary loops selectively suppress voltage/current harmonics, enhancing power quality management without external sensors or harmonic extraction modules. The method eliminates hardware additions while resolving VSG harmonic issues in micro-grids and large grids. Results demonstrate significant improvements in harmonic mitigation, enabling energy storage VSG systems to partially replace active power filters (APFs). This approach offers a cost-effective solution for harmonizing renewable integration with grid stability, broadening VSG applicability. Key innovations include dual-loop adaptive harmonic suppression and impedance reshaping through modified repetitive control, advancing sensor-less power quality enhancement in modern power systems. The strategy effectively balances grid support functionality with harmonic management, facilitating scalable renewable energy adoption.