Michigan communities can breathe easier this winter knowing that the state has made it easier to connect affordable and reliable clean energy, thanks to an update to utility DTE’s interconnection procedures. The updated procedures provide a clearer, fairer, and more consistent process for connecting distributed energy resources (DERs) such as rooftop solar to the grid, ultimately paving the way for more clean energy to come online in Michigan.
The recent update to Michigan’s statewide rules required each utility, including DTE, to revise their interconnection procedures and submit them to the Michigan Public Service Commission (MPSC) for review and approval. DTE’s application was the only one that was converted to a contested case, involving expert testimony, cross-examination, and legal briefs. The Union of Concerned Scientists (UCS) and their partners in Michigan intervened in the case, with a focus on how “export-limited” DERs are handled.
Export-limited DERs are systems where the maximum output to the grid is constrained to be less than the DER’s full capacity. This is typically needed when the grid has insufficient hosting capacity for the proposed DER. Historically, penetration screens have been based on nameplate capacity, which is overly conservative for modern solar photovoltaic (PV) systems. The updated procedures now base the penetration screen on export capacity, making it more aligned with current technology.
One of the key advancements in the updated procedures is the inclusion of safeguards against inadvertent export, where a DER momentarily exceeds the export limit. The procedures now require any power control system (PCS) to respond to inadvertent export within 30 seconds, certified by UL 3141. Additionally, if the PCS malfunctions, the DER must stop exporting energy to the grid.
In the original filing, DTE sought to place restrictions on PCS technology, which were deemed unnecessary by UCS. After discussions and a settlement agreement, DTE agreed to ease the restrictions on PCS while adding a voltage screen to address concerns about the risks of inadvertent export. The settlement also included provisions for unintentional islanding, IEEE 2800 applicability, and net metering eligibility.
Overall, the settlement marks a significant victory for clean, distributed energy in Michigan. By working closely with DTE and other stakeholders, the updated procedures now provide clear guidance for DER projects and effectively manage the risk of inadvertent export. Customers in DTE’s territory can now follow a more reasonable set of procedures when implementing clean solar energy projects, resulting in more projects being approved more quickly.
