Modbus Registers 2.0b – E2 Series
These Modbus Addresses can be accessed to provide OpenADR signal data to third party control systems.
Modbus Integration - Quick Start
- The simplest way to integrate OpenADR signals into any control system is to poll the 3 Digital Outputs: event_pending 0:0111, event_moderate 0:0112 & event_high 0:0113. Shown in the violet shaded area. The E Series can also be configured to WRITE values to other Modbus servers or clients.
- event_special 0:0114 is not commonly used but could be included for future use.
- Pending offers the system time to prepare like pre-cooling the AC before the Event or just notifying personnel.
- Depending on the signals used by the Utility (Moderate or High) the logic for the reduction on the load should be based on binary states of those registers in accordance with the participation agreement.
Control systems can write to the opt_out 0:0103 register. ON will exclude the system from the Event or end the Event if in progress. All registers will return to non-Event states. The VTN will be notified. It is important to return the opt_out 0:0103 register to OFF after the Event as it will remain ON indefinitely.
In addition to the event_pending 0:0111 binary which ON=Event Notification and remains ON throughout the Event, 2 additional Analog Inputs give additional information about the Pending phase.
- event_status 3:0117 1 = far 2 = near & 3 = Active. Near and far are non-precise terms and vary greatly among Utility VTNs. They are more of a guide that anything else. Active is when the Event goes from the Pending to actual Moderate, High or Special.
- next_op_mode 3:0118 foretells what the Event will be when it becomes Active; 1 = Moderate, 2 = High & 3 = Special. This could be utilized in the overall control strategy particularly if the Utility uses more than 1 signals in their programs.
Epoch time variables
These variables provide epoch times in seconds for use in the control system
- current_time 3:5021 - the GRIDlink onboard clock Current time
- event_start_time 3:5023 - Event Start time in epoch seconds
- event_end_time 3:5023 - Event End time in epoch seconds
VTN Connection and Communications Status
There are 2 registers which indicate VTN connection status in the orange shaded area.
- vtn_connect 0:0003 - ON = good connection and notifications are within parameters
- comm_status 0:0115 - where -1=Server Refused Connection, -2=Error in Payload, -3=Certs Fail Authentication.