Open-loop control sends power setpoints to the inverters without any feedback of the actual value. Closed-loop control feeds back the values measured at the point of interconnection and corrects the commands. In closed-loop operation, the controller compares the real and reactive power read by the meter against the total command. It then adds a correction so that the target is actually met at the meter. For active power limits, open-loop control is enough in a pure feed-in system. A system with self-consumption should use closed-loop control so that surplus PV goes to local loads and the interconnection point still meets the grid operator's limit. For reactive power, closed-loop control is normally recommended because it compensates for the effects of the line and any transformer. One exception is a site with high self-consumption and a large reactive demand, such as electrical machines without compensation equipment. There the inverters may produce almost only reactive power and still miss the setpoint, so open-loop control is advised. On Tesla Megapack systems, closed-loop control is turned off by default at commissioning. This prevents wind-up if the meter's current transformer or potential transformer wiring is wrong. It should be switched on only after the meter readings are confirmed to match the applied command. In SMA systems, a device with the System Manager function can take over closed-loop control at the point of interconnection.
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related_toc1 drafted · lead Closed-loop plant control
Tesla System Controller corrects Megapack power commands using real and reactive power feedback from the meter.
sec=2.3.4 h=3b39d623a8e7sec=2.5.5 h=54730bb896f4sec=2.5.4 h=a5508dbc6f2fc2 drafted · lead Point of interconnection
Closed-loop control uses measured values fed back from the point of interconnection.
sec=h1 h=92b23ebd81e8tbl=6.r6 h=eb6b0a239b8dc3 drafted · lead Energy meter
The meter provides the feedback signal for closed-loop control.
sec=2.3.4 h=3b39d623a8e7sec=2.5.5 h=54730bb896f4sec=2.5.4 h=a5508dbc6f2fc4 verified · fact Export limitation
Open-loop control is enough to limit active power feed-in in pure feed-in systems. Systems with self-consumption need closed-loop control.
sec=h1 h=92b23ebd81e8sec=h201 h=41daf4831d8dverified by: review-workflowverified on: 2026-10-24
c5 drafted · lead Self-consumption
With self-consumption, closed-loop control is used so that the power at the interconnection point still meets the grid operator's limit.
c6 drafted · lead Reactive power
SMA recommends closed-loop control for reactive power setpoints so line and transformer effects are compensated.
c7 verified · fact Active power
sec=h1 h=92b23ebd81e8sec=2.3.4 h=3b39d623a8e7verified by: review-workflowverified on: 2026-10-24
c8 drafted · lead High reactive power demand
With high self-consumption and high reactive demand, inverters may fail to hold the setpoints, so open-loop control is recommended.
c9 drafted · lead System manager function proposed
A System Manager can take over closed-loop control at the point of interconnection.
tbl=6.r6 h=eb6b0a239b8dc10 drafted · lead SMA Data Manager M
The Data Manager offers both operating modes for active and reactive power.
c11 drafted · lead SMA Cluster Controller
Uses open-loop control in systems with no self-consumption and direct limitation of feed-in.
sec=h201 h=41daf4831d8dc12 drafted · lead Tesla Megapack platform (generation not stated) proposed
sec=2.3.4 h=3b39d623a8e7sec=2.5.5 h=54730bb896f4sec=2.5.4 h=a5508dbc6f2fClosed Loop Control Enable is a read/write boolean at Modbus register 21401.
tbl=97.r1 h=44c528c5141ftbl=109.r1 h=44c528c5141ftbl=97 h=45b9d99a7b8b