Inherent Damping Characteristics of Feedforward-Based Harmonic Current Controllers in Active Power Filters

초록

An Active Power Filter (APF) is an effective solution for compensating harmonic currents from nonlinear loads. In general, the harmonic current control of an APF can be categorized into two schemes: a feedback scheme and a feedforward scheme. Among these, the feedforward scheme has been widely adopted for APF control because it does not require a harmonic current detector. However, many studies have not provided sufficient explanations for why such a detector is unnecessary. Furthermore, the control stability of the feedforward scheme has been analyzed in the same manner as that of the feedback scheme. In practice, since the fundamental current controller is involved in harmonic current control, even in the feedforward scheme, such conventional stability analysis methods are not accurate. Therefore, this paper conducts an accurate analysis of the control loop for the feedforward scheme. Consequently, the feedforward scheme not only eliminates the need for a harmonic current detector but also provides improved stability due to its inherent damping characteristic, making it more suitable for APF control.

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