Investigation on series active filter compensated high power grid-connected voltage source inverters with LCL filter

This paper deals with Series Active Filter (SAF) based damping methods for the LCL filters of three-phase, grid connected, low voltage, high power Voltage Source Inverters (VSIs). The inherent resonance problem of LCL filters is damped via passive or active damping methods. Passive damping methods employing damping resistors create significant power losses reducing the overall system´s efficiency for high power inverters. Active damping methods, on the other hand, are not applicable due to inverter´s limited controller bandwidth. Unlike passive and active damping approaches, the proposed Series Active Filter (SAF) based systems maintain the stability of the inverter while eliminating the resistive power losses. The steady-state and dynamic performances of the SAF compensated VSIs are investigated and viability of them are demonstrated. Two novel methods, one superior than the other in terms of design simplicity are investigated providing efficiency, line current THD and dynamic response results. The developed methods are proven by theory and computer simulations.