Energy storage STS switching principle and analysis
2025-08-21
The STS and the Power Storage Converter (PCS) collaborate to achieve seamless grid-connected/off-grid switching. The typical process is as follows:
1.Normal Grid-Connected Operation
Grid power supply → STS closes the grid-side SCR → The load is powered by both the grid and the energy storage PCS.
2.Grid Fault Switching
STS detects grid anomaly → Disconnects the grid-side SCR (≤8ms) → Notifies the PCS to switch to off-grid mode (V/F control) → PCS establishes voltage within 10ms → The load is 100% powered by the energy storage PCS.
3.Grid Recovery
STS detects normal grid parameters → PCS synchronizes output voltage phase → STS closes the grid-side SCR → PCS switches back to grid-connected mode (P/Q control) → The grid simultaneously supplies power to the load and charges the energy storage through the PCS.
Configuration Principles:
- Important load power + PCS-side power ≤ STS power. Generally, the load power should be ≤ 0.5 × STS rated power.
- Critical load power ≤ PCS-side power. For example, if the critical load power is a maximum of 250kW, a 250kW PCS is required, and the STS power must be at least 500kW.
In addition, if seamless load switching or high reliability is required, the STS may be powered by an independent, small-capacity UPS to ensure absolute stability of the control circuit. The corresponding electrical diagram is as follows:
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