A Signal-Processing Adaptive Algorithm for Selective Current Harmonic Cancellation in Active Power Filters

Abstract

Selective harmonic cancellation has become of primary importance in a wide range of power electronics applications, for example, uninterrupted power systems, regenerative converters, and active power filters (APFs). In such applications, the primary objectives are an accurate cancellation of selected harmonics and a quick speed of response under transients. This paper provides a novel signal-processing algorithm for selective harmonic identification based on heterodyning, moving average finite-impulse response filters, and phase-locked loop (PLL). The algorithm is applied over the current of a nonlinear load in the feedforward-based control of an APF. The PLL tracks the phase and frequency of the fundamental component. Then, the fundamental phase is multiplied by the order of the selected harmonic, and two random unitary orthogonal "axis waves" are generated. These unitary waves, rotating at the harmonic frequency, are multiplied by the input load current, thereby "moving" the Fourier series coefficients of the selected harmonic to dc (heterodyning). Moving average FIR filters are used to filter the harmonics generated in the heterodyning process from the dc signal; moving average FIR filters are very suitable for most of the power quality applications, thanks to their "comb-type" frequency response and their quick transient response. Experimental results confirm good performance for steady-state harmonic cancellation and an optimal system response to load transients. The theory of the algorithm has been developed for single-and three-phase systems.

Harmonic resonances in Wind Power Plants: Modeling, analysis and active mitigation methods

“…Firstly, the instantaneous distorted current I d is measured. Then, by a signal processing algorithm the harmonic currents are identified [46], [47]. These harmonic currents feed the current controller which should assure steady-state tracking.…”

Deterministic Algorithm for Selective Shunt Active Power Compensators According to IEEE Std. 1459

“…In the last decade, the interest in the selective compensation of load non-efficient currents has increased, as it is demonstrated by the number of publications dealing with this topic [8][9][10][11][12][13][14][15][16][17][18][19]. Selective SAPCs contribute to reduce losses in the power networks and at the same time can be used for the dynamic support of the grid following the settings established by the power network managers.…”

“…Selective SAPCs usually focus on the harmonic currents cancellation, without considering the non-efficient currents demanded by unbalanced and reactive linear loads. Most of the works dealing with harmonic cancellation concern about fast response and harmonic detection [8][9][10]. However, they do not focus on the SAPC rating and overloading issues.…”

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.…”