A stable three-phase LCL-filter based active rectifier without damping

Industrial-LCL-based grid converters using an active rectifier need to be designed in view of robustness, stability and high efficiency. In this paper the design of an active rectifier that does not need damping whether passive or active is described. This allows obtaining stability without the decrease of the efficiency typical for the passive damping methods or the increase of cost due to more sensors or more complex control algorithms that is typical for the active damping methods. This has been achieved with a careful choice of sensor position and of the passive elements in the LCL-filter. In fact if the current sensors are on the grid side, rather than on the converter side, the current loop is much more near to the stability. Moreover, if the grid side inductance is a fraction of the converter side one, the current loop is again much more near to the stability. Thus, with a proper design the system can be made stable at some switching frequencies even without any damping.