Our power quality applications: Active harmonic filter used in data center, Yangtze River Delta Digital Financial Data Center. The harmonics of the data center are mainly generated by UPS and some nonlinear DC power supplies. The power supply system consists of two 1000kVA transformers and one 800kW generator. The centralized management scheme is adopted. The capacity of each transformer is 400A. The source power filter is realized by four 100A parallel machines, the model is SinE-APF-100A, to automatically track and compensate the harmonic current generated by the load to ensure the safe and reliable operation of the entire system.