چكيده به لاتين
It is safe to say that power electronic devices led to great progress in today’s technology. However, the increasing number of industrial loads using power electronic devices, caused many power quality problems. In this case, power quality conditioners play an important role in overcoming this issues. Unified power quality conditioner (UPQC) that is composed of two active filters is one of the most effective devices to enhance power quality. However the control of the converters is an important matter here.
To overcome the power quality issues in distribution system, in this project, the UPQC with dual control strategy is used. This method uses two active filters to remove grid voltage harmonics, unbalances, sag/swell and also the harmonics of the load current. Unlike the conventional UPQC, in dual control strategy, parallel active filter (PAF) and Series active filter (SAF) are controlled as voltage and current sources, respectively. In this manner, by using sinusoidal references, the pulse width modulation control of the UPQC deals with a well-known frequency spectrum.
Different control methods have already been implemented on this equipment. Despite the easy design and implementation of the proportional integral controller, a constant gain needs to be adjusted properly in the input controller of the PAF. The other problem with this type of controller is the non-zero steady-state error for sinusoidal inputs which makes it suitable only for initial levels of design.
The goal of this investigation is to introduce a resonant controller based on second order generalized integrators for UPQC to work in 3P4W distribution system. In the 3P4W topology, Neutral current is compensated using a fourth leg in series converter of the UPQC. The proposed control scheme not only improves power quality, but also reduces the number of measurements. The outstanding features of this scheme are reduction in switching losses by using sinusoidal references and also accurate tracking of control references with negligible steady state error. In order to evaluate the control system performance, simulations are held for both proportional-integral and proportional-resonant controllers in 3P3W and 3P4W systems and the results confirm the better performance of PR controller in most of the scenarios.
Keywords: Active power filter, Unified power quality conditioner, dual control strategy, resonant control.
