Large capacity multi-HVDCs feed and large-scale new energy grid connection have become the main characteristics of China Southern Power Grid （CSG）, and the problem of frequency stability is increasingly prominent. In order to make full use of the frequency regulation function of the unit under pumped storage pump conditions, a multi-level low frequency integrated stability control system composed of pump cutting and load shedding, wide area low-frequency centralized pump cutting, local low-frequency decentralized pump cutting and low-frequency load shedding is designed. Combined with the operation characteristics of the unit under pumped storage pump conditions, the coordination and cooperation method of frequency stability control strategies at all levels are formed. Based on RTDS system, the hardware on-loop real-time simulation analysis of frequency stability control system is carried out, and the adaptability and reliability of each level stability control strategy are verified in various cases. According to the actual operation of the system, the optimization measures such as exiting the low-frequency slip locking function of the pump storage substation are put forward. The low frequency integrated stability control system has been put into practical operation in the field.