Resilient Power Systems Inc. — Department of Energy SBIR Phase II: C52-16d

Description

As dependency on renewables increases, these resources become a necessity that must continue operating during harsh grid and weather-related conditions. The standard commercial practice uses three-phase low-voltage power converters and step-up transformers for connection to the distribution grid. The large number of step-up transformers and low-voltage converter output filters have caused an increase in distribution line problems. The step-up transformers require large inrush current during energization, thereby necessitating manual and expensive grid reconnection processes when the solar converters trip-off during harsh weather or fault events. The output filters disrupt and destabilize the grid during fault events. The North American Electric Reliability Corporation requires grid tie medium-voltage equipment to withstand 2X rated voltage. To remove obstacles for high penetration of solar energy into the nation’s grid, solar converters capable of connecting directly to medium-voltage feeders with large overvoltage capability and no passive filters that can withstand harsh weather-related events, such as hurricanes, floods, and lightning, have become a requirement, not an option. To address the above issues, this effort will deliver a rugged, modular, scalable up to 34.5kV low-cost multi-port converter. This system eliminates the troublesome step-up transformer and output filter with 2X withstand voltage rating and no-inrush current. The proposed technology not only survives normal power line conditions but continues to operate during harsh electrical and weather events and can withstand up to 2 feet of flood water without shutting down. Additionally, the proposed technology will have large overload capacity to supply reactive fault current during short circuits to reduce voltage dips that would prevent other grid equipment from tripping. The converter will integrate energy storage through an isolated dc port which provides flexibility for different batteries. This converter increases system efficiency, eliminates power line problems, and provides reactive volt-ampere compensation. It also costs less than a low voltage solar converter + storage converter + output filter + step-up transformer. During Phase I, the project team developed the control algorithms, high frequency transformer optimization process, analyses for weather-related transient events, and commercialization feasibility study. During Phase II, the team will develop hardware and software for standards conformance, build a 1.2MW prototype, and perform system validations. During a Phase III effort, the team plans to deploy a pilot in the field and validate the performance in a real-world environment. If successful, the proposed technology will reduce the cost of solar energy and will remove obstacles for high penetration of solar energy into the nation’s grid.