A shunt active power filter for harmonic isolation in a cloud computing facility

Cloud computing has gained significant momentum in recent years. Server farms, the backbone of the cloud computing, also grow in the same pace. These server farms are equipped with thousands of computer server racks. Although these computer servers are powered by PFC-front end, which draws almost perfect sinusoidal current, large amount of AC side filter capacitors are installed to meet the harmonics and EMI requirement. The resulting resonance frequency between the line/system inductance and the filter capacitors becomes low, thus typical back ground harmonic distortion of the grid or neighboring harmonic-producing loads can cause significant voltage and current distortion. In this paper, a harmonic isolation technique based on a shunt active power filter is explored. The proposed technique can suppress the parallel and the series resonance, and maintain the power quality of the facility. Laboratory test results are provided to validate the performance of the proposed technique.