Overall requirements, specifications, KPI, and use case definitions

This report, Deliverable 1.1 of the iPLUG project, overviews the work that has been carried out as a foundation to stimulate the design of Multiport Power Converters (MPCs). The report details the grid requirements and KPI selection, as well as the definition of the topology, architecture and use cases.

Multiport Power Converters (MPCs) are defined as any device that interfaces more than two energy ports. A classification structure is then developed that allows all MPCs to be categorised, and therefore compared systematically, in terms of isolation type.

Three distinct scenario groups are identified where MPCs can provide significant benefit. These scenarios are: 1) distribution network support, 2) building connections (including residential and facility buildings), and 3) remote communities. Specific cases and data sources are identified, which will allow later iPLUG research to be tailored for particularly valuable applications.

The grid code and safety standard requirements for low- and medium-voltage converters and converter-interfaced devices are reviewed to identify the base requirements that MPCs are likely to be asked to comply with. The review shows that the requirements expected of conventional converter devices on these voltage levels are becoming more strenuous and advanced control requirements to support the local grid are beginning to be defined in grid codes. Galvanic isolation is not found to be required of converters on low- and medium-voltages but is described as offering significant benefits for the safe operation and interconnection of different voltage levels. The structure of future MPC requirements is also discussed, highlighting the complexity of imposing conventional specific energy source requirements on a device that will interface multiple different energy sources.

A set of key performance indicators (KPIs) are developed that describe the benefit that MPCs can offer and allow the comparison between different topologies. The KPIs are separated into network and converter KPIs, where the former describes the benefit that MPCs can bring to the grid and the latter describes the beneficial characteristics that MPCs can offer in comparison with conventional converter solutions.

A review of existing MPC configurations is carried out to identify the characteristics of different topologies and the gaps in the field where iPLUG research should be pursued. The review establishes a set of key features (which can be gathered from the literature review without needing additional studies, different to the KPIs) to describe topology characteristics. A Pugh Matrix scoring method is used to identify the topologies and features that are suitable for the iPLUG applications. The scoring highlights that several partially-isolated configurations are particularly suited to the iPLUG scenarios. The scoring method and review also highlight that further effort needs to be made to optimise the sizing of devices for a given voltage level and to explore the nuance of MPC control operation.

Finally, the features and considerations of control and communications for MPCs are outlined. From this overview, MPC operation is deemed to be feasible using DSP or FPGA devices, both of which are shown to be able to support the expected complex power converter operations.