DERs#

Challenges from DERs

The energy mix is a group of different primary energy sources that are converted into the secondary energy which we use. Historically, this bulk power system consisted of a limited number of generation sources, such as coal-fired power plants supplying the primary source of energy for a given municipality. When alternative energy generation sources are deployed across the grid like solar, hydroelectric, and wind, this significantly complicates system dynamics. These distributed energy resources (DERs) are essential for propelling the green energy transition forward. Within the United States the DER contributions to the energy mix now approaches 10% (pg. 19, NASPI Technical Report 2020). Furthermore, DERs are growing faster than any other energy generation source.

With the adoption of DERs, both industrial sized generation operations and even individual consumers seek to sell energy back to the grid. Problematically, monitoring devices are not capturing needed data on fast events, such as inverter-related resource behaviors that can cause faults. Inverters which convert direct current (DC) generated by DERs like photovoltaic (solar) systems to the alternating current (AC) required to transmit electricity across the grid! Understanding how inverter health relates to system health is an area ripe for further study.

Notedly, Digital Fault Recorders (DFRs) and Dynamic Disturbance Recorders (DDRs) do recording high resolution data at 960 samples per second and >30 samples per second respectively, however, these measurements are event triggered, meaning that they collect data in windows rather than continuously. Since they are triggered in the case of predetermined event-conditions, they are not suitable to investigate with algorithms the very events in which they may need to be triggered (pg.19). Continuous data is therefore necessary to understand transient stability failures that can occur within just a few cycles in areas with high penetration of inverted-based generation sources.

Effects of inverted based resources can include:

  • Voltage fluctuations

  • Reverse power flows

  • Low-fault currents