Aggregate and dispatch a fleet of V2G-capable EVs as a virtual power plant using OCPP 2.1 bidirectional sessions managed from a central CSMS

Steps

1. Maintain a real-time fleet state database indexed by chargePointId and transactionId; for each active bidirectional session, store the current SOC (from MeterValues 'SoC' measurand), available discharge power (from the V2XChargingNeeds response), and session start time.
2. Receive a dispatch signal from the grid operator or VPP market system specifying total MW discharge target and duration; distribute the target across available V2G-capable sessions using a dispatch algorithm (e.g., proportional to available discharge capacity, or merit-order based on SOC and departure time constraints).
3. For each session in the dispatch plan, send a SetChargingProfile request with a ChargingProfile containing a negative-power ChargingSchedule period (discharge) for the dispatch duration, a ChargingRateUnit of 'W', and stackLevel set to distinguish VPP dispatch from other profiles.
4. Monitor MeterValues during the dispatch window: collect 'Power.Active.Import' (negative = discharge) and 'Energy.Active.Export.Register' measurands at the configured SampledValue interval; aggregate across all sessions to compute fleet-level power and energy delivered.
5. Handle session drop-outs gracefully: if a vehicle disconnects mid-dispatch, recalculate the dispatch plan across remaining sessions and send updated SetChargingProfile requests — maintain a headroom buffer (e.g., deploy 90% of available capacity) to absorb unexpected dropouts.
6. After the dispatch window, send a ClearChargingProfile (targeting the VPP stackLevel) or a new SetChargingProfile with a positive power schedule to resume normal charging; report the delivered energy and power time series to the grid operator via the agreed telemetry channel.