Last week, the California Independent System Operator (CAISO), in conjunction with More Than Smart and three of the state’s distribution utilities (Pacific Gas & Electric Co., Southern California Edison, and San Diego Gas & Electric), unveiled a proposed set of coordination and process improvements that the group believes are necessary to manage the integration of significant distributed energy resources (DERs) onto the grid. The report, Coordination of Transmission and Distribution Operations In a High Distributed Energy Resource Electric Grid, notes that there have been relatively low volumes of DER penetration to date, but expects much higher volumes of DERs, of potentially more diverse character, in the future. In anticipation of this “high-DER” future, the report offers a set of suggestions that the group believes the CAISO and the distribution utilities should undertake to enable smooth integration of these resources.
The report recognizes that efforts are underway in California to reduce barriers to DER participation at both the distribution and wholesale levels, but notes that there is a lack of transparency between the transmission and distribution segments of the grid, which are connected but operated by different entities. While historically energy has flowed only from the transmission system on to the distribution system, DERs now inject energy onto the system at the distribution level, resulting in multi-directional flows over transmission-distribution interfaces. To ensure continued system reliability, the report recommends the CAISO, distribution utilities, and DER owners and aggregators work together to increase coordination and communication of operational conditions, constraints, and forecasts between: the distribution utilities and the CAISO, the distribution utilities and the DERs and their aggregators, and the CAISO and the DERs and their aggregators. Additionally, the report recommends development of a pro forma “integration agreement” for DER aggregators wishing to aggregate multiple DERs into a virtual resource. Over the longer term, the report recommends more robust development of real-time coordination processes, system protection and controls enhancements, and feasibility assessments.
Keeping an eye toward the future, the report notes that the working group behind the report will continue to meet to track progress and further advance coordination.