The control strategies were studied to solve the problem of the harmonic currents increment in the reactive power compensator consisting of capacitors and static var generator. Firstly, accurate extraction algorithm of load harmonic current based on multiple secondorder general integrator was investigated. Secondly, resonant controller was applied to control the harmonic current flowing from the pulse width modulation gridconnected converter to the grid based on the traditional d-axis gridvoltageoriented vector control, so as to suppress the harmonic current in the grid. Simulation model of the system was established and simulation research was carried out. The validity of the extraction algorithm of load harmonic current and the control strategy of harmonic suppression was verified by the simulation results.