The audible noise of AC filter capacitors is one of the major noise sources in High VoltageDirect Current (HVDC) converter stations. In order to avoid the sharp noise of AC filter capacitors, it isnecessary to design a Multiple Harmonic Current Injection System (MHCIS) for power capacitors toanalyze their audible noise characteristics. Simulating effectively the noise of AC filter capacitors undertheir actual working conditions in converter stations is the primary target of this proposed MHCIS. Toensure the accuracy of the harmonic currents injected into the power capacitors, each harmonic current isdetected and controlled separately. On the basis of the instantaneous reactive power theory, a selectiveharmonic current detection algorithm is proposed in this paper for the single-phase MHCIS. The amplitudeof the selected harmonic current can be tracked timely and exactly in d-q synchronous rotational coordinatesystem, such that a Proportional Integral (PI) controller can be directly operated to eliminate the steadystateerrors. The experimental parameters are usually invariable in this system, the phase deviation of theselected harmonic current is also fixed. Thus the phase angle offset of the corresponding harmonic currentcan be detected and calculated to compensate the system inherent delay. Owing to the accurate detectionand control of multiple harmonic currents, the actual working conditions of AC filter capacitors can beaccurately simulated, and the reliable noise analysis results of power capacitors can be obtained. Finally,the proposed selective harmonic current detection and control algorithm is verified by the theoreticalanalysis, simulation and experimental results.