Abstract
This paper presents a new control method for a three-phase four-wire Unified Power Quality Conditioner (UPQC) to deal with the problems of power quality under distortional and unbalanced load conditions. The proposed control approach is the combination of instantaneous power theory and Synchronous Reference Frame (SRF) theory which is optimized by using a self-tuning filter (STF) and without using load or filter currents measurement. In this approach, load and source voltages are used to generate the reference voltages of series active power filter (APF) and source currents are used to generate the reference currents of shunt APF. Therefore, the number of current measurements is reduced and system performance is improved. The performance of proposed control system is tested for cases of power factor correction, reducing source neutral current, load balancing and current and voltage harmonics in a three-phase four-wire system for distortional and unbalanced loads. Results obtained through MATLAB/SIMULINK software show the effectiveness of proposed control technique in comparison to the conventional p-q method.
Highlights
Among the main problems of power quality in the three-phase four-wire systems are the current harmonics, load unbalance, exceeding neutral current, voltage harmonic, voltage sag and voltage swell
The structure of Unified Power Quality Conditioner (UPQC) is similar to that of unified power flow controller (UPFC) used in transmission systems and its main goal is to control power flow in the fundamental frequency [8], whereas UPQC is used in distribution systems for performing duties of series and shunt active power filter (APF) simultaneously
The performance of proposed system is tested by using MATLAB/SIMULINK software in cases such as power factor correction, reducing source neutral current, load balancing and reducing current and voltage harmonics in a three-phase four-wire system for distortional and unbalanced loads
Summary
Among the main problems of power quality in the three-phase four-wire systems are the current harmonics, load unbalance, exceeding neutral current, voltage harmonic, voltage sag and voltage swell. In [18], the one-cycle control approach (without calculating the reference) is used for controlling a three-phase four-wire UPQC Among the these control methods, the most important and common control methods are p-q and SRF theories and so far some research have been done to modify these two control theory [19,20,21,22]. The performance of proposed system is tested by using MATLAB/SIMULINK software in cases such as power factor correction, reducing source neutral current, load balancing and reducing current and voltage harmonics in a three-phase four-wire system for distortional and unbalanced loads. Series APF is capable of compensating voltage unbalance and compensating harmonics at the point of common coupling in consumer side [28]
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