MODBUS control of power sources and loads


Thread Starter

Thomas Podlesak

I am with the Power Generation Division of the U.S. Army's Communications-Electronics Research, Development and Engineering Center, Aberdeen Proving Ground, MD.

We are interested in monitorinng and controlling engine driven portable generators and their loads via MODBUS. We envision several generators and loads colocated in a small area all connected via MODBUS. We further envision connecting this local network to a larger network via Ethernet TCP/IP. We are looking essentially for an evaluation kit to get started with. This would consist of an Ethernet TCP/IP equipped master and several slave units, the latter haveing relay closures for control purposes and A/D converters to monitor device functions. We have been unable to find a suitable package that would get us started.

Lynn August Linse

Sounds almost like you want to make your own box.

However, there are LOTS of 'Modbus Load Curtailment/Demand Control' devices out there - many can tell you the current/load as well as will have large power relays to power on/off the load.

One partner we've worked with is, but most firms which make a "Modbus speaking power sub-meter" will also have the ability to manage a remote load. So SquareD, Schneider-Electric, etc will all sell.

Thomas Podlesak

I appreciate your response and looked at some of your references. They seem to partially solve the problem, but appear to be too sophisticated for some of our applications. We would like a simple, commercially available interface box with maybe a relay closure or two, and some A/D for monitoring.

Paul Wilhelm

Hello Thomas-

Please Google "Woodward TQG", or check out:

Any of the above mentioned controler models with Modbus protocol should be capable of starting/stopping and monitoring gensets. On ECU equipped gensets engine parameters can be read over CAN J1939 and mapped to Modbus. On older sets you can bring in some analog values and convert to Modbus for remote monitoring of oil pressure, water temp, etc. Once you start the gens you still need a controller to synch, parallel and load share with other units.

As stated in the previous post there are affordable COTS solutions available, some that include features for automatically starting and stopping generators in a system based on changing load demand (LDSS). LDSS is done on a peer-to-peer network- it does not require a supervisory "microgrid" controller. There are some things a supervisory microgrid controller can do that a genset controller alone can't, like anticipate load changes and shed load if needed, but having a layered control archetecture with LDSS available in the genset controllers will help you build a robust control system for tactical applications. I'd love to discuss this more with you.