Plug Power, LLC
In response to a request from the Chair of the Nwew York State Public Service Commission, the New York State Department of Public Service (DPS) initiated a collaborative investigation for standardizing and streamlining interconnection requirements for small distributed electric generation. DPS staff organized an Interconnection Standardization Working Group with representatives from utilities and equipment manufacturers. Grid interconnection technical issues were discussed and debated at a number of meetings. The Working Group prepared a report, Standard interconnection Requirements (SIR), for inverters rated less than 300 kVA connected to radial distribution lines, documenting where the group did, or did not, reach consensus in developing technical grid interconnection requirements for distributed generation systems.
The Working Group reached a consensus in developing a procedure for type-testing and verification-testing of static inverters for distributed generators smaller than 300 kVA connected to radial distribution lines. Type-testing is performed once for a specific interface package. The SIR document requires that all inverter designs be type-tested by an independent testing laboratory. Once an inverter design meets the type-test criteria, the design would be accepted by all New York State utilities.
The objective is to demonstrate static inverter interface equipment manufacturers' verification-testing, and the type-testing procedure that is in compliance with the proposed New York State Standard Interconnection Requirements formulated by the Interconnection Standardization Working Group, for distributed generators less than 300 kVA connected to radial distribution lines.
An independent testing laboratory will perform the inverter manufacturers' verification-testing protocol, and conduct type-testing procedures in compliance with the proposed New York State Standard Interconnection Requirements. Two inverters will be tested, a single-phase non-islanding inverter rated less than 10 kW, and a three-phase inverter with integrated protection and control rated less than 300 kW.
The project will demonstrate a well-defined static inverter test procedure, similar to the testing procedures in place for other electrical equipment, that will be in compliance with the proposed New York State Standard Interconnection Requirements. This will have applications to a number of emerging new distributed generation technologies that utilize static inverters such as fuel cells, photovoltaics, microturbines, and wind power. Inverter testing may become a new business service for New York State testing laboratories that could lead to future employment opportunities.
Schedule and Status
Testing at UL labs revealed no major difficulties with following the SIR document procedures with single-phase inverters. Problems were experienced with testing three-phase inverters because of the isolation transformers. Additional testing evaluated all combinations of "y-delta" and "delta-y" inverter isolation/utility distribution transformer wiring.