Study On One-Cycle Controlled Active Power Filter Based On Current Reference

With the wide application of nonlinear equipments, a great amount of harmonic and reactive currents are generated in power system, which draws attention all over the world. Active power filter (APF) is one kind of power electronics devices used to restraining harmonics and compensating reactive power dynamically. The compensation performance is not affected by the impedance of power system, and it has advantages as fast response, high controllability and adaptability, etc. So the research on APF is more and more in many countries.One-cycle control (OCC) is one kind of nonlinear control methods. Its principle is to control the duty-ratio of switch to make the average value of switch variable of the switching converter equal to or proportional to the control reference in each cycle, so that steady-state and dynamic-state error can be eliminated effectively. Nowadays, OCC method has been applied to APF successfully,which displays fast response, excellent power source perturbation rejection and simple control circuit.Main tasks of the article are presented as follow:1. Introduce the theory and research actuality of APF and OCC.2. In order to solve the disadvantages of one-cycle controlled APF, this paper uses harmonic current detecting method based on instantaneous reactive power theory, tracing control circuit based one-cycle control which uses fundamental current and it's active component as control reference to single-phase APF, three-phase three-wire APF and three-phase four-wire APF with three-leg. The control equations and control models of are set up. The results of simulation verify that this scheme is effective, and in this scheme APF can provide harmonic current compensation or both harmonic and reactive currents compensation according to requirement with the distorted source voltages.3. With the analysis of three-phase four-wire APF with four-leg, OCC is applied to suppress neutral-phase current in three-phase four-wire system solely with current reference. After the control equation and control model are set up, the simulation is used to validate the scheme. In order to decrease the number of switches operating at high frequency in the main circuit,the paper applies OCC method with vector operation to replace ordinary OCC. The results of simulation verify this control method can compensate the neutral current as well as three-phase harmonic and reactive currents effectively. Anymore, this method can reduce the loss of switches in APF.