Classic Discrete Control Technique and 3D-SVPWM Applied to a Dual Unified Power Quality Conditioner

The unified power quality conditioners (UPQCs) are useful to correct distortions in voltage and current waveforms in case of problems related to harmonics, flicker, and power factor. The dual topology of the UPQC allows a loop control in the inverters less demanding in terms of switching functions; however, the control techniques proposed in the literature have some disadvantages as large computation time and some calculation delays. Therefore, this paper presents the application of a classic discrete-time control model for a three-dimensional space vector pulse width modulation (3D-SVPWM) to be used with the dual UPQC, obtaining a fixed commutation frequency and a low computation cost. The results show that the applied method helps to reduce the harmonics in the source, voltage sags and load current and improve the power factor of the electrical circuit tested. Furthermore, the high frequency created by the switching of elements in the UPQC is filtered by the impedance of the power source and it does not represent a problem for the circuit. Due to the simplicity of the model, simulations demonstrate that the application of this classical control technique is enough to achieve good results to compensate harmonics and power factor with the dual UPQC. The development of the controllers is carried out by discretization of the transfer functions of the control in continuous time and their application with the three-dimensional space vector pulse width modulation (3D-SVPWM) technique.