Study On One-cycle Control Three-level Three-phase Four-leg Active Power Filter

Active power filter (APF) is an important equipment to compensate harmonic and reactive currents in power systems. By realtime detecting harmonics and reactive current in the power line, then it generates the compensating current which is equal to harmonic current in amplitude and opposite in polarity, aim at improvement and advancement of electric quality. Compared with some conventional measures, active power filter has advantages of real time and accurate compensation. So active power filter has been studied widely and begin to intustralise.The one-cycle control (OCC) technique established a large-signal nonlinear control scheme with significant advantages in terms of rejection of line perturbation and speed of response. One-cycle control is developed to dynamically control the duty-ratio d of a switch, such that in each cycle the average of switched variable at the switch output is exactly equal to or proportional to the control reference. In this paper, new development of one-cycle control is survey, which includes the feasibility, modeling, steady state and dynamic study as well as some improvement in one-cycle control. Analyses the advantages of one-cycle control in the application of DC/DC converter, power factor correction (PFC), active power filter (APF), uninterruptible power supply (UPS), power amplifier and maximum power point tracking controller for photovoltaic power generation. Finally, the future development of one-cycle control was discussed.In a high voltage system, the circuit designers are often confronted with a serious challenge: there are no semiconductors capable of sustaining the desired voltage. Multilevel converters that provide more than two voltage levels, less distorted waveform and that have merits of low sustaining voltage, low switching losses, high efficiency and low EMI and that are called"perfect zero-harmonic"converters offer many benefits for higher voltage, higher power and especially higher frequency applications.A three level three-phase four-leg APF based on One-cycle control is presented. This scheme doesn't need any measured quantities of three-phase load currents and three-phase input voltages. And also the complicated calculation of the harmonics and reactive current components are eliminated. The controller is composed of some integrators with reset, flip-flops, comparators and linear components, which has the characteristics of simple, high precision and effectual compensation. In addition, it...