A microgrid controller is the control system (hardware + software) that monitors and manages a microgrid’s generation, storage, and loads to keep the site operating safely, efficiently, and—when designed—capable of islanding from the utility grid. In EV charging environments, a microgrid controller coordinates onsite resources such as solar PV, battery energy storage (BESS), and EV chargers to manage maximum demand, reduce costs, and maintain resilience.
What Is a Microgrid Controller?
A microgrid controller is the “brain” of the microgrid. It typically:
– Measures power flows at the point of common coupling (PCC) with the grid
– Monitors onsite generation and storage status
– Controls dispatch: when to charge/discharge batteries, curtail PV, or start generators
– Manages controllable loads (e.g., HVAC, process loads, managed charging)
– Maintains voltage/frequency stability in islanded mode (if supported)
– Executes priorities and constraints (safety limits, tariffs, emissions targets)
Controllers can be centralized (one main controller) or distributed (multiple controllers coordinating via a hierarchy).
Why Microgrid Controllers Matter for EV Charging
EV charging can create large, fast-changing loads. A microgrid controller helps:
– Keep site import below a maximum site demand limit to protect main LV panels and the main fuse rating
– Reduce maximum demand peaks by using storage and load control
– Increase renewable utilization by aligning charging with PV output
– Maintain fleet readiness with priority-based charging schedules
– Improve resilience by keeping critical chargers operational during outages
– Provide site-wide monitoring and reporting for energy and carbon KPIs
For fleet depots and campuses, this can enable more chargers without costly grid upgrades.
How a Microgrid Controller Works
Typical control loop:
– Collect measurements from meters, inverters, and breaker status (often sub-second to minute-level)
– Forecast or infer near-term load and generation (optional)
– Apply constraints: import/export limits, battery SOC limits, protection margins
– Dispatch resources: set inverter power, battery charge/discharge, generator output
– Allocate power to controllable loads, including EV chargers via load balancing or CPMS integration
– Verify stability and fail-safe behavior if communications are lost
Key Functions
Grid interface control
– Maintain import/export within contractual limits
– Manage PCC breaker operation and islanding transitions (where enabled)
Energy optimization
– Peak shaving, tariff optimization, demand charge reduction
– Renewables-aware scheduling and self-consumption maximization
Load management
– Dynamic control of EV charging and other flexible loads
– Priority rules for critical assets and operational schedules
Resilience and islanding
– Black start logic (in advanced systems)
– Frequency/voltage control in islanded operation
– Load shedding sequences for non-critical circuits
Monitoring and diagnostics
– Alarms, event logs, performance reporting
– Cybersecurity and access control (critical for operational technology)
Integration with EV Charging Systems
Common integration paths include:
– Direct control of EV chargers via OCPP through a CPMS
– Local load controllers that adjust charger current based on site capacity
– Meter-based feedback at the EV subpanel or whole-site incomer
– Coordination with maximum charge current per charger and site-wide demand caps
A robust design typically includes a local safety layer so charging remains within safe limits even if cloud connectivity is lost.
Design and Commissioning Considerations
– Measurement quality: correct meter placement (PCC vs feeder), CT orientation, sampling rate
– Communication reliability: Ethernet/cellular redundancy and local fallback control
– Protection coordination: ensure islanding transitions don’t create unsafe states
– Clear priorities: cost vs carbon vs resilience vs fleet readiness
– Documentation: control philosophy, setpoints, fail-safe behavior, test procedures
– Maintenance access planning for controller panels, meters, and networking equipment
Related Glossary Terms
Microgrid
Energy management system (EMS)
Battery energy storage system (BESS)
Managed charging
Load balancing
Dynamic load management
Maximum demand
Maximum site demand limit
Peak shaving
Main LV panels