Stability assessment of distributed multiconverter systems in automated grid

In this paper a comprehensive dynamic stability of current control approach for multi-unit pulse-width modulated (PWM) voltage source converters (VSCs) is presented. The model is based on radial topology of converters for harvesting controllable distributed energy recourses (DERs) across the distribution level of power grid. The control system has feedback compensation and limits the disturbances featuring fast regulation which is adjusted for multi-converter system. The controller enables islanded and grid-connected operations of DERs regardless of load types. The load dynamics will be included as feedforward compensation to provide perfect regulation of the voltage at the point of common coupling (PCC). The current controller is scrutinized under the system dynamics and transitions. In the islanded mode, one of the controllable units provides voltage and frequency control as a master controller and the other units operate based on the grid-connected control strategy in the slave mode. The slave converters can be used properly as interface of DERs or for the active integration of converter-interfaced loads (CILs). The stability assessment of the system is presented based on a detailed simulation. The simulation results show that the controller for the islanded parallel converters can ensure the stability of the system when converters are tied together.