How can a power sag immunity system (PCS) in an energy storage system prevent loss of control?

When the grid voltage drops, the PCS needs to maintain control (e.g., prevent accidental shutdown or reset) to ensure continuous operation or achieve uninterrupted grid-connected switching (LVRT). This requires coordinated hardware and software design.

Hardware aspects:

1. Wide input range auxiliary power supply: The auxiliary power supply for the control board and drive circuits should have a wide input voltage range (e.g., DC 300-1000V) to maintain stable output even when the DC bus voltage fluctuates due to voltage drops.

2. Critical voltage monitoring and holding: Monitor the MCU core voltage and use large-capacity energy storage capacitors or supercapacitors as backups when necessary to maintain short-term power supply.

Software/control aspects:

1. Fast detection algorithm: Real-time detection of grid voltage to quickly identify voltage drop events.

2. Seamless control mode switching: Smoothly switch from normal grid-connected mode to transient support mode (e.g., providing reactive power support); the control algorithm must be robust and stable.

3. Watchdog and state protection: Software watchdog and non-volatile storage of critical states prevent program crashes and ensure rapid resumption of operation after voltage recovery.