ANSNPThe series of neutral line security protectors are connected in parallel in low-voltage distribution systems with harmonic loads, which can quickly and real-time detect dynamically changing harmonic currentsTracking and compensation. The basic principle of the midline security protector is:Collect overcurrent information on the neutral line of the system through the current detection link, and quickly calculate it through the controllerCalculate and extract the content of each harmonic current, generate harmonic current commands, and generate compensation current in the opposite direction to the overcurrent amplitude through power execution devicesFlow and inject into the neutral line to eliminate excessive current in the neutral line.