Harmonics mitigation for offshore platform using active filter and line reactor methods

Propose of this study is to analyze power system profile especially harmonic at one of Offshore Platform in Indonesia. Field survey was conducted and found that total harmonic distortion (THD) both of voltage and current exceed limitation as recommended in IEEE 519-1992, THD-i 11.76% ZU A, 11.29% ZUD, 31.11% ZUG, and unbalance load exceed 5%. Analysis using ETAP 12.6 shows harmonic reduction could be achieved by installing multi-tuned passive harmonic filters. However, since the result of actual measurement shows unbalance power flow that reflect the dynamic impedance on the network system, therefore the passive filter would not effective to reduce harmonics. On the other case active filter type is not sensitive on dynamic impedance, due to its internal controller capable to compensate and cancel harmonic currents in any condition. Based on the above considerations, it is recommended to install a line reactor on each VFD and active harmonic filter on respective Point of Common Coupling (PCC) with sizing 60A and 4% in ZUA; 75A and 4% in ZUD and 120A and 3% impedance in ZUG for active filter and line reactor impedance respectively. The final THD-i in each NUI as follow 5.87%, 4.95% and 6.65%.