The low frequency oscillation with local mode caused by generators in the power grid is increasingly prominent. Oscillation source determination and damping is the key to solve this problem. An operational control method based on oscillation cluster identification is thus proposed for damping low frequency oscillation. This method identifies generators involved in low frequency oscillation by the amplitude and frequency of their phasor measurement unit active power data at first. Then the involved generators are divided into two opposite clusters based on correlation coefficients between their rotor angular velocities. Source generator in the active cluster is the main reason for causing oscillation and provides oscillation energy

while the generator in the passive cluster is driven to oscillate and consume oscillation energy for maintaining overall system energy conservation. Then operational control measures are finally provided to damp the oscillation. Results of two practical application cases on a real provincial power system demonstrate that this operational control method is fast and effective for damping the low frequency oscillation.