Welcome to the first edition of the Open DC Grid newsletter!
Open DC Grid is an open source project whose top level goals include:
Over the last month we launched the project in the form of the web site open-dc-grid.org derived from source material at our GitHub organization page. The web site has three sections accessible via tabs on the home page: one for the standard itself, one for implementations conforming to the standard, and one for the project which has pages on the team, meetings, ways to contribute etc. These sections derive from materials in three repositories on GitHub:
We went over these materials in our February 11 meeting. Links to a recording of that meeting and the presentations are available on our meetings page.
Over the next few months we expect the standard to evolve through a series of interim partial releases starting from 0.0.1 and eventually reaching 1.0.0, which will be our first official standard. We used semantic versioning where the leading digit indicates a major, incompatible change, the middle digits increment for backwards compatible changes and the trailing digits increment for minor corrections. It is likely there will never be a 2.0.0 release as that would be a different standard. All released versions of the standard will be directly accessible at the web site and as downloadable PDF files if someone wants to print a more conventional paper copy of the standard.
During our meeting we also went over some preliminary ideas for the system architecture defined by the standard and a key subpart the 48V bus link. The critical use cases that we hope to address are within a Solar Home System to interconnect solar or other sources, batteries and loads, and between systems that share power across an external link. This means that we need to manage multiple sources on a bus with droop control and multiple loads with power allocated among them. To generalize the model somewhat, we define devices that potentially have multiple ports connected via wired links. The links can take different forms such as a DC bus or point-to-point links such as USB-C or Ethernet. A microgrid consists of a network of devices and links with some administrative policy determining how energy moves between devices.
We envision one set of protocols to manage the energy transfers, independent of the link technology in use and another set of protocols that may be specific to particular link types. One essential link type recognized by the standard is a DC bus operating at a nominal 48V. This corresponds to an existing standard for automotive electrics, ISO-21780, so we would like to harmonize our standard with that one so devices could operate in both environments. Other standards in this area that are candidates for harmonization include IEEE P2030.10 and IEEE P2030.10.1, both in draft at the IEEE.
A key technology to implement devices conforming to the Open DC Grid is a programmable, bidirectional DC-DC converter with droop control to manage current sharing. Martin has begun implementing such a converter that will soon appear in our implementation repository. He presented a preliminary description of the technology at the February 11 meeting available on our meetings page. We are soliciting funding to support that development.
More updates from Open DC Grid will be coming soon. We welcome your feedback and participation (see our page on contributing).