RT20 | Flexgrid at Berkeley Lab: a Flexible Testbed for Power-HIL Experiments

​The Flexgrid testbed features an ensemble of Distributed Energy Resources (DER) designed for the study of their integration in the distribution grid, new controls development, and microgrid operations. The setup consists of three 240 V (AC) buses, each connected to one smart inverter with 14 kW PV and 3.3 kW / 6.4 kWh battery system. Flexgrid allows two modes of operations. When not used, the system is directly connected to the local distribution grid, with the inverters connected in a Delta configuration, supplying clean energy to the LBNL campus and allowing to test novel control algorithms on an actual distribution grid. Alternatively, the system can also be interfaced with an Opal-RT system in a power HIL setup, coupled through a 30 kW regenerative programmable three phase voltage source, driven by the Opal-RT simulator. In power HIL setup, the inverters can either remain in a Delta configuration, or be reconfigured to a Wye configuration. This allows the mapping of inverters to different nodes in the re-time model, to encompass a wide variety of simulation cases. Flexgrid also features programmable loads and uPMUs that can easily be integrated in a HIL setup.In recent projects, the full capabilities of Flexgrid were used in two separate projects. In the ADMS project, the Flexgrid was used to validate a physical controller to drive the inverters as system actuators to regulate the feeder head voltage. In the CyDER project, the interfacing with the power HIL setup was abstracted by the Functional Mockup Interface (FMI) standard for co-simulation. CyDER further used this model to interface with other standardized co-simulation blocks to control active and reactive power output of the inverter and battery systems, to support a distribution grid.Our presentation will focus on the Flexgrid testbed, its capabilities and future upgrades, and results from the two projects.