Operation of One-Cycle Controlled Three-Phase Active Power Filter With Unbalanced Source and Load

Abstract

The power quality of the ac electric system has become a great concern due to the rapidly increasing numbers of electronic equipment being connected to the grid. In order to reduce harmonic contamination in power lines and to improve its transmission efficiency, the research on active power filters (APF) has become a hot topic. Many control methods for APF were proposed in recent years. Among them, one-cycle control (OCC) has shown great promise featuring excellent harmonic suppression, simple circuitry, robust performance, and low cost for the control of three-phase APFs. Theory and experiments in previous papers have demonstrated the validity of OCC-controlled APFs working with balanced line voltages and balanced nonlinear loads.However, in reality, neither three-phase grid voltages nor threephase nonlinear loads are balanced at all times; therefore, it is vital for an APF to be able to handle unbalanced sources and/or loads. In this paper, the OCC-controlled three-phase APF working with unbalanced three-phase line voltages and unbalanced loads are studied, respectively. Theoretical analyses and experimental results indicate that with OCC control, sinusoidal input currents can be realized, whether the input voltages and/or the nonlinear loads are balanced or unbalanced.Index Terms-Active power filter (APF), asymmetric power systems, harmonic current suppression, one-cycle control (OCC), power quality, unbalanced load, unbalanced power systems.

A current based OCC technique implemented by DSP for a three-phase OCC rectifier

“…On the other hand, to calculate average current, it is not recommended to use a pure integrative, since in practice it presents saturation problems [20]. In this sense, a low pass filter (LPF) or a peak detector is normally used [9][10][11]. Unlike aforementioned reported works, to calculate average value, in present proposal it is used a lead-lag compensator (LLC) as averaging method:…”

“…OCC was also applied in APFs, when non linear load is balanced [10]. However, when load is unbalanced, no solutions were proposed [11]. Unbalanced load is always a problem in APF, because distribution networks generally feeds single phase loads and there is no way to constrain which phase is most utilized.…”

Implementation of One-Cycle Control for Switched Capacitor Converters

“…The one-cycle control (OCC) method, which was developed for switching converters [12]- [22], has the ability to control the duty-ratio of switches so that the average diode-voltage is exactly equal to the control reference in each switching cycle. It completely rejects external disturbances and enables the output voltage to rapidly follow the control reference.…”

Theoretical Analysis and Control of DC Neutral-point Voltage Balance of Three-level Inverters in Active Power Filters

“…The control of harmonic perturbations with active power filters (APF) has become a hot topic in the power engineering field. In the past two decades, active power filters have been developed rapidly to suppress harmonics in the power distribution systems of 380V voltage grids [1]- [3]. However, the voltage grids of many power distribution systems for petroleum based power generation is 600V.…”