Design and Implementation of LCL-filter-based Grid-connected Inverters Without Damping

Suppressing resonances of LCL filter by either passive or active damping would increase loss or cost of a system.Therefore,we proposed a design method for numerical-controlled,undamped,LCL-filter-based,and space-vector-pulse-width-modulating(SVPWM) grid-connected inverters,which could realize stable system operation with appropriate design of parameters.A z-domain model of the grid-connected inverter was established,and the design procedure and an example of the system were provided in detail.Finally,experiments of a 15 kVA prototype of the proposed inverter were carried out.The results prove that the designed grid-connected inverter is a stable system,which keeps operating stably even under a sudden load change.Compared with active damping methods,the proposed grid-connected inverter does not need current sensor or voltage sensor,which might reasonably reduce the system cost.Besides,compared with passive damping methods,the proposed inverter has higher efficiency and smaller total harmonic distortion(THD) of grid current.