A Study On Hybrid Active Power Filter

By studying traditional instantaneous power theory in single-phase circuit, we developed a real-time detecting method in this paper based on digital technology, which can detect harmonic current and fundamental reactive current in both single-phase and three-phase circuits. Meanwhile, the rating of APF deriving from the topology of hybrid active power filter in this paper is much smaller than that of deriving from traditional topology. Theoretical analysis and simulation results have shown that the circuit can not only improve filtering performance but also suppress the resonance between passive filter and power systems.The instantaneous reactive power theory in three-phase circuits based on - co-ordinate shows its defect when applied to single-phase circuit. So by analyzing the stability of voltage vector and the changeability of current vector, we proposed to construct sinusoidal sequences with the same and delaying ninety-degree phase angles to voltage vector, then to multiply with the current vector respectively to bring about active and reactive power. For this reason, we redefined the instantaneous reactive power so as to make it easier for detecting harmonic current and fundamental reactive current. Furthermore, the detecting method is also fit for three-phase system.Most of the traditional real-time detecting method for harmonic current is based on sinusoidal voltage or locking the voltage phase accurately, which deviating from the real circumstances. In this paper, the real-time detecting method for harmonic current need only that the constructed voltage system be in step with the real voltage system (which can be obtained by cross-zero detection to voltage waveform), meanwhile, we have testified in concerned chapter that the phase is not important for the constructed voltage system. Otherwise, we also have probed into the reasons for the pulsation of instantaneous powers in distorted systems.