For resolving the problem that power filter cannot work normally because TCR (thyristor controlled reactor)
generates extra third harmonic current under asymmetrical voltage, the paper proposes the estimation method of current
capacity that TCR generates extra third harmonic current under asymmetrical voltage. Considering extra third harmonic
current under asymmetrical voltage, Optimum method based on genetic algorithm is used to design the parameters of
power filter. With reactive power compensation and harmonic suppression project of a steel mill as example, the proposed
method is simulated by Matlab. Simulation results show optimized power filter can eliminate extra third harmonic current
effects under asymmetrical voltage, meet the requirement of reactive power compensation, reduce harmonics current that
load injects into system, and guarantee the power filter safe operation under asymmetrical voltage.
