We wanted to build a DC microgrid at CCCamp19, but never fully got around to it. So we'll keep on trying in our lab, for the next camp and other events.
The idea of this project to develop different components that help us in running a DC microgrid. This will involve different tasks in the grid, like putting energy into the grid, consuming energy from the grid, connecting smaller sections together, etc. Over time, we'd like to include additional functions such as testing of equipment and monitoring of the grid, or individual units of the grid.
At CCCamp, a workgroup was formed to discuss and develop different ideas on how a DC grid could look and work like. There's a collection of some of these concepts at altpwr.net. This is supposed to be a concrete implementation of some of these concepts.
The first unit we built for the microgrid is called Consume001, and as the name suggest, its intention is to enable convenient consumption of power from the grid. In its initial and simplest form, the unit consists of a power "inlet", in this case a 4-pole Speakon socket (plugs and sockets are probably worth a project log themselves), a DC power meter, and some 12V car power sockets (with switches).
Above is the first version we put together at CCCamp19 (turns out making a square hole without the proper tools is one hell of fun). The DC power meter is called GC90, and has a TTL port to allow reading it out with a microcontroller. So the list of possible/planned additions is the following:
Remote readout of the power meter, e.g. via LoRaWAN
Different power outlets, such as USB C, DC barrel connectors
DCDC converter to allow different input voltages
a few more "input" connectors to allow better spreading of the grid
integrated battery backup
complete replacement of the power meter with a microcontroller that then also controls the DCDC meter and can connect/disconnect loads depending on grid voltage
I started working on the remote readout as one of the first things. The power meter uses a micro USB for its TTL connection, which is a little weird but also makes it easy to interface. Here's the first shot at setting this thing up:
Notice the small USB plug on the left side fo the power meter. There's a chain of boards, first a USB A breakout (mostly hidden by the case cover), a level shifter (5V of the power meter <-> 3.3V of the Arduino), an Arduino LoRaWAN dev board, and an FTDI for programming. I'm currently building a dedicated PCB for that.
Right now, there are no fuses in the unit but most of these car plugs already have on in them. Still, this is high on the list, especially for the input.
The DCDC converter should be really easy in its simplest form, just putting a ready made unit between the input and the power meter.
The last idea is probably the most complicated but also the coolest in terms of what it would allow us to do. Let's see what happens...