Improvement of Power Quality and Reliability with multifunctional PV-inverters in distributed energy systems

The share of distributed generation (DG) within the distribution network increases strongly. A lot of these DG units are driven by renewable energy sources (RES). Up to now, these units only inject active power depending from the availability of their primary source. In future on the one hand DG units have to contribute to grid stability, but on the other hand DG units can provide additional functionalities in order to offer a surplus value for the customer. Therefore especially inverter-coupled systems are well suited. Additional functionality could be improvement of power quality and reliability (PQR), but also peak shaving, provision of control energy or reactive power compensation is conceivable. This paper presents several approaches of such multifunctional inverter systems developed by ISET e.V., SMA and TU Sofia with the focus on PQR.