Abstract: Based on principle of sliding mode control，the mine-used resonant impedance type hybrid active power filter system (RITHAPF) control technology was further researched，and reactive power compensation and harmonic suppression on power grid were made.The switching function modeling method was adopted to make modeling and propose the mathematical model of RITHAPF.Through the derivation of RITHAPF equivalent model，a convergence and stability criterion was put forward for RITHAPF system.Combining the influence of discrete index reaching law on discrete sliding mode control，the reaching law index of the continuous system was extended to the discrete system，to prove that influence of the discrete index on the system perturbations and external disturbances is still robust.Furthermore，according to the discrete mathematical model of active power filter，the synovial discrete mathematical model is given.The active part current tracking controller was designed based on the reaching law of the discrete sliding mode control.The simulation results showed that the resonant impedance type hybrid active filter based on sliding mode control had a good performance of reactive power and harmonic current compensation for 6 kV DC hoisting system bus.

Key words: Resonant impedance, Fundamental series resonance, Sliding mode control, Hybrid active power filter