NEIS 2017 - Conference on Sustainable Energy Supply and Energy Storage Systems

The identification of the grid impedance and its frequency characteristic is important to evaluate the effect on the power quality by electrical energy sources and loads. The measurement results can be used for an improved design of inverters and their control parameters, grid-side filters and the determination of resonance frequencies. The approach used in this contribution to determine the grid impedance is based on the switching of an ohmic load. The resulting transients in voltage and current caused by this switching can be used to calculate the frequency dependent grid impedance. In this paper the development of an antiserial super cascade circuit using SiC-Jfets for the application within the determination of the grid impedance is presented. With this switch topology high switching frequencies can be achieved which is important for a precise identification of the grid impedance especially at higher frequencies. The development of the antiserial super cascade circuit is outlined and measurement results with a prototype are shown.

Active network management (ANM) is a promising approach to cope with the proliferation of distributed generation from renewables. The distribution system operator (DSO) can utilize its own assets in this regard, e.g. by installing remotely controllable on load tap changer transformers. Additionally, the DSO can incorporate distributed energy resources from third parties into its active network management. This, however, involves specific challenges such as dealing with temporary unavailabilities of these systems and ensuring a smooth transition between autonomous control and control by the DSO. This contribution presents an extended ANM control algorithm that addresses these challenges.