# EMS Control Logic: Turning Economy and Reliability into SOC Rules EMS is strategy and coordination; PCS is execution and conversion. SOC banding, peak-valley arbitrage, anti-backflow and remote O&M with AEMS. EMS vs PCS division EMS is "strategy and coordination"; PCS is "execution and conversion" — clear roles make planning efficient. SOC banding (confirm on site) **SOC high 80–100%**: prioritise load/peak shaving; allow surplus to grid. **SOC normal 30–80%**: renewables first, battery smooths power, charge/discharge by tariff. **SOC low 20–30%**: limit discharge; prepare diesel or grid top-up. **SOC too low <20%**: protective mode; diesel/grid forced top-up; keep critical loads. Core functions Self-consumption, surplus to grid, peak-valley arbitrage (time function), self-use+backup, meter anti-backflow, remote monitoring/waveform/upgrade/alarm. VGRID [AEMS100/200/300/400/500](/en/page/grid-forming-weak-grid) dispatches PCS, BMS, PV, grid, diesel and loads, with cloud access. Reminder SOC thresholds are not fixed — set them with backup goals, load criticality, tariffs, diesel cost and battery strategy. ## Can EMS directly control the PCS? Yes. Via RS485/CAN/4G it dispatches PCS, BMS, STS and diesel, executing charge/discharge and transfer strategies. ## How is peak-valley arbitrage realised? EMS charges in off-peak and discharges in peak by tariff, under anti-backflow and backup constraints. ## Is EMS required for anti-backflow? For grid-tied sites that must not export, anti-backflow (meter + EMS strategy) is required. ## How many devices does AEMS manage? Up to 6 PCS and 6 MPPT, with WiFi/4G cloud comms and local HMI.