What Dynamic Load Throttling Is
Dynamic load throttling is the real-time reduction (and increase) of EV charging power to keep a site within electrical limits and operational rules. It “throttles” chargers up or down based on measured conditions such as site power cap, building load, charger count, tariff windows, or grid constraints.
In practice, it’s one of the main control actions used inside dynamic load management.
Why Dynamic Load Throttling Matters
Dynamic throttling prevents overload events while still delivering maximum usable charging:
– Protects against breaker trips and transformer overheating
– Allows more chargers on a limited connection without constant upgrades
– Reduces peak demand and potential demand charges
– Helps depots hit departure SOC targets by reallocating power dynamically
– Supports grid export/import constraints in sites with DER
How It Works
A throttling system typically uses:
– Real-time measurement (CTs/meters) of site import and sometimes feeder loads
– Control logic that calculates “available headroom”
– Setpoints sent to chargers (current limit or kW limit), updated continuously
Common triggers:
– Building load increases → EV charging is throttled down
– Many vehicles plug in simultaneously → each session is capped lower
– Priority vehicle needs energy soon → others throttle down so it can ramp up
– Time-of-use window opens → ramp up within the site cap
What Gets Throttled
Depending on charger capabilities and architecture, throttling can apply to:
– Per charger: reduce total kW output of a unit
– Per connector: cap each socket independently (useful for dual-port AC)
– Per phase current (AC): adjust A limits and maintain phase balance
– By group: cap a cluster of chargers fed from one DB/feeder
Throttling Strategies
Throttling is not only “reduce everyone equally.” Common strategies include:
– Equal-share throttling: everyone reduces proportionally
– Priority throttling: some chargers maintain higher power; others are reduced
– Minimum viable first: throttle to give baseline charge to all, then ramp priority vehicles
– Staggered throttling: temporarily reduce new sessions to avoid sudden peaks
– Phase-aware throttling: throttle only on overloaded phases in three-phase systems
Dynamic Load Throttling vs Active Power Throttling
These are closely related terms:
– Active power throttling usually refers to controlling charger output power (kW) as a feature
– Dynamic load throttling emphasizes that throttling changes continuously based on live site conditions
In many deployments, “active power throttling” is the capability and “dynamic load throttling” is how it’s applied operationally.
Best Practices
– Define hard limits (site cap, feeder limits) and enforce them first
– Use accurate metering at the correct point (main import, key feeders)
– Implement safe fallback behavior if comms/controller fails
– Combine throttling with scheduling in depots (departure-time priorities)
– Log setpoint changes and reasons for audit and tuning
– Test under worst-case simultaneity during commissioning
Common Pitfalls
– Throttling too aggressively → vehicles leave undercharged
– Throttling too slowly → short overshoot spikes still trip breakers
– Poor phase balancing → one phase overloads even with “throttling” enabled
– No priority logic → critical fleet vehicles don’t get enough power
– Not communicating policies to drivers → operational confusion and bay blocking
Related Terms for Internal Linking
– Dynamic load management
– Dynamic load balancing
– Active power throttling
– Depot power management
– Site power cap
– Demand charges
– Charging schedules