Protection configuration of DC energy storage unit: over-voltage protection, thermal protection and over-current protection, voltage and current change rate protection, charging protection; DC connection unit protection configuration: configuration of fuse, low-voltage DC circuit breaker, low-voltage DC isolation switch and mid-span Battery protection, for multiple battery energy storage units, the DC connection units should be connected as far as possible to avoid loss of more power supply capacity in the event of failure; bidirectional converter (PCS) protection configuration: input and output side overvoltage protection, over-frequency and under-voltage protection Frequency protection, phase sequence detection and protection, anti-islanding protection, overheat protection, overload and short circuit protection.