Battery demand response
A controller that follows grid frequency and sends a set point to the inverter, with independent metering at the connection and the battery.
- Measure
- Point-of-connection power, battery AC power, state of charge, availability and temperature limits
- Rule
- Event and rebound energy are measured against the programme's own baseline DOE
- Sensors
- ZDR-22, grid frequency sampled at 100 ms or better, 0.01 Hz resolution, 20 ms event recording ZDR-2X datasheet (PDF, opens in a new tab)
- On site
- ZGW-20 Gateway, BESS monitoring, dispatch records and onward telemetry ZGW-20 datasheet (PDF, opens in a new tab)
Hardware for battery flexibility telemetry
One controller at the connection for the fast response, one meter on the battery so its contribution can be separated, and the BMS for what the electricity cannot show.
Measures at the connection, follows grid frequency, and sends a changing set point to the inverter over Modbus
- Choose the CT type: mini-CTs on existing 1 A or 5 A CTs, or Rogowski coils at 1 kA and 3 kA
Frequency sampled at 100 ms or better at 0.01 Hz, 20 ms event recording, GPS time sync, RS-485 Modbus RTU master for up to 4 devices
The battery's own AC power, separated from the rest of the site
- Choose the CT rating for the battery's AC connection: 120 A split-core, or 300 A, 1 kA and 3 kA Rogowski coils
Keeps the event record, the availability picture and the onward telemetry
Where the BMS is on its own bus
State of charge, charge and discharge limits, temperatures and alarms from the BMS or inverter
What bounds a battery's dispatchable envelope
Nameplate power is not available power. These measurements are what turns a rating into a number you can offer.
| Position | What it tells you | Reference | Sensor |
|---|---|---|---|
| Point of connection | The change the grid actually saw, in one sign convention | Import positive and export negative, on matching interval boundaries ZDR-2X datasheet (PDF, opens in a new tab) | ZDR-22 (on this page), connection |
| Battery AC power | The battery's own contribution, separate from unrelated site load | Record whether auxiliary loads are inside the measurement ZEM-63 datasheet (PDF, opens in a new tab) | ZEM-65 (on this page), battery |
| State of charge and limits | How long a response can be sustained, and how much has to be kept back | The BMS state of charge is a model output, with its own reserve and uncertainty ZMB-3X datasheet (PDF, opens in a new tab) | ZMB-31 (on this page) |
| Availability and protection | Whether the capacity can be offered at all right now | Alarms, temperature limits, contactor state and maintenance mode | ZMB-31 (on this page), status registers |
AC and DC are different numbers. Point-of-connection power includes the inverter's losses and the site's auxiliaries. Say which side of them each figure is on.
The battery decides, not the controller. The battery management system owns its own protection. A set point is a request that the BMS can refuse, and the record should show when it did.
Dispatch and event evidence in Edge
A programme pays for what it can see. The record has to survive the event and the argument afterwards.
- Availability before commitment
- A calculated sensor removes unavailable capacity from the offer: reserve, temperature limits, alarms and maintenance mode all subtract from it.
- Requested against achieved
- Every dispatch keeps both: what was asked for and what the meters measured, with the ramp between them.
- Withdraw when the data goes stale
- If the BMS data or a meter stops, the availability falls to zero rather than continuing from the last good reading.
- The event record leaves the site
- Interval data and events export over MQTT or HTTP to the programme's own telemetry, and stay on the Gateway as well.
Commissioning checks
Do these with the battery's commissioning engineer present, and before any capacity is offered.
-
Every meter agrees on direction
During a known charge and a known discharge, compare the connection, the battery meter and the inverter's own figures.
Pass when all three tell the same story in one sign convention, with the differences explained.
-
State of charge and limits are read correctly
Compare the values in Edge with the BMS display across a charge and a discharge.
Pass when the values and their units match, including the charge and discharge limits.
-
A dispatch is followed and recorded
Run an approved dispatch and record requested power, achieved power, ramp and acknowledgement.
Pass when the achieved power follows the request inside the agreed time, and the record shows both.
-
Loss of data withdraws capacity
Simulate stale BMS data and an unavailable inverter in turn.
Pass when availability falls to zero and the programme telemetry says so.
-
A full cycle is captured
Run a bounded event and its recovery while keeping every interval.
Pass when the whole window is in the record, including the energy state at the start and the end.
What monitoring does not replace
Everything here sits outside the battery's own protection and the programme's own rules.
- External monitoring and dispatch must not bypass the battery management system, the inverter's protection or the site protection scheme.
- Nameplate power and energy are not continuously available flexibility once reserve, degradation, temperature and warranty conditions are applied.
- This guide does not approve grid-code compliance, fire safety, protection settings, market registration or settlement.
- Whether a measured reduction is a paid reduction is decided by the programme's baseline method, not by the meter.
Sources and related guides
Sources
- Measurement and verification for demand response (opens in a new tab) US Department of Energy and FERC. Baselines, interval measurement and how programme rules decide whether a reduction counts.
- Battery energy storage system evaluation method (opens in a new tab) US Department of Energy FEMP. Measured battery performance and the power and energy boundaries an evaluation needs.
- ZDR-2X Demand Response Controller datasheet (opens in a new tab) EpiSensor. Specifications, ranges and ordering codes.
Related
- Electric boiler demand response Application guide Shed electric heating stages against measured stored heat, prove each stage actually opened, and measure the recovery the site pays for afterwards.
- Solar PV monitoring Application guide Independent AC metering at the inverter and the grid connection, inverter registers for context, and an energy balance that adds up.
- Dynamic frequency response services explained Knowledge Base How dynamic response works, why it matters to grid operators, and the monitoring stack required to participate.
- Demand-response event energy and rebound worksheet Engineering tool Measure the reduction delivered in a demand response event, any shortfall, and the rebound afterwards.
Reviewed by EpiSensor Engineering on . Revision 4.
Check a battery site against its programme's rules
We will check what the registers give us, place the metering, and agree the availability rules.