Harmonic Damping Characteristics of Single-phase Full-bridge Rectifier Based Loads

With the rapid development of power electronic technology, many linear single-phase loads in low voltage systems are replaced by those equipped with a single-phase diode rectifier. Therefore, most of single-phase loads become harmonic producers due to their nonlinear characteristics. The nonlinear loads may have different damping characteristics at harmonic frequencies, which could cause potential power quality problems. This paper studies the harmonic damping characteristics of such nonlinear loads. The harmonic damping index is defined to quantify the damping effect of nonlinear loads of harmonic frequencies by analyzing the harmonic model. Then, the harmonic damping index of different harmonic frequencies is compared through simulations and experiments. The results show that the nonlinear load has a constant damping effect for the fundamental frequency, but a stronger damping for the harmonic frequencies. The harmonic damping of such nonlinear loads varies with the harmonic phase angle of supply voltage, and becomes stronger with the increase of the harmonic order. It implies that this type of nonlinear load may be beneficial to the suppression of harmonic resonance.