Frequency Response Analysis of Current Controllers for Selective Harmonic Compensation in Active Power Filters

Abstract

This paper compares four current control structures for selective harmonic compensation in active power filters. All controllers under scrutiny perform the harmonic compensation by using arrays of resonant controllers, one for the fundamental and one for each harmonic of interest, in order to achieve zero phase shift and unity gain in the closed-loop transfer function for selected harmonics. The complete current controller is the superposition of all individual harmonic controllers and may be implemented in various reference frames. The analysis is focused on the comparison of harmonic and total closed-loop transfer functions for each controller. Analytical similarities and differences between schemes in terms of frequency response characteristics are emphasized. It is concluded that three of them have identical harmonic behavior despite the fact that their implementation is significantly different. It emerges that the fourth one has superior behavior and robustness and can stably work at higher frequencies than the others. Theoretical findings and analysis are supported by comparative experimental results on a 7-kVA laboratory setup. The highest harmonic frequency that can be stably compensated with each control method has been determined, indicating significant differences in the control performance.

Hybrid Active Power Filter: Design Criteria

“…The shunt connection has been the most studied topology, where the APF is connected in parallel with the load. One of its traditional uses is the elimination of current harmonics produced by loads which generates such disturbances, this is HCS loads (Harmonic Current Source) [4,5]. However, the parallel APF is not suitable in situations where the load generates voltage harmonics, HVS loads (Harmonic Voltage Source).…”

Direct power control of shunt active filter using high selectivity filter (HSF) under distorted or unbalanced conditions

“…In this context, the most popular control technique is usually based on current controller which forces the SAPF current to follow its reference [7][8][9][10][11][12][13][14][15][16].…”

“…Also, there has been tremendous progress during the last decade in current control techniques for active power filters [12][13][14][15][16] including of a proportional controller plus multiple sinusoidal signal integrators [12], a PI controller plus a series of resonant controllers [13,14], or vector PI (VPI) controllers [15]. This is due to the development of powerful and fast microprocessors.…”

Modified PWM Technique for Harmonic Reduction

“…Indeed, accuracy and speed of the SAF response are related to this point [9][10][11]. Time domain and frequency domain are two well-known methods for generation of reference current [12][13][14][15]. Time domain methods are based on measurements and transformation of three-phase quantities such as d-q or p-q transformation, whereas the frequency methods are based on the Fast Fourier Transformation (FFT).…”

“…This fact is proved with mathematical equations. With regard to the compensation objectives, the control strategy and the method for extracting the nonactive load currents references are determined [8][9][10][11][12][13][14][15]. The purpose of this paper is to compensate the harmonic current using the frequency domain method of compensation in which all harmonic current components are targeted and eliminated.…”