By Vadim Zheglov, Senior Consultant
As the penetration of variable Distributed Generation (DG) is increasing due to incentives and mandates, such as the Renewables Portfolio Standard (RPS) target in California of 33% by 2020, a number of challenges to utilities have arisen. The existing electric grid was designed and created to safely and reliably distribute power from a few centralized power generation sources through highly monitored and controlled transmission lines to distributed loads typically supplied via radial distribution feeders. Some DG such as small hydro and bio-gas generators are relatively constant and predictable in output. However, most of the recent growth in DG has been to exploit renewable resources, such as solar and wind energy, which are inherently intermittent. This intermittency can cause wide and unpredictable variability of the net power flow over the distribution system. This variability, along with the frequently wide dispersal of the generation by numerous small sources, can cause a number of voltage and power quality problems, and inhibits the utility’s operational control over the voltage and loading conditions in their service territory. At the same time, DG, in particular solar photovoltaic (PV) due to its recent popularity resulting in large-scale deployment of PV installations in many distribution systems, offers opportunities for utilities that, if leveraged, can help optimize grid performance.