# Classic Discrete Control Technique and 3D-SVPWM Applied to a Dual Unified Power Quality Conditioner
## 1 Introduction
Besides, in [25], authors propose the use of three isolated H-bridge with a voltage source at the DC side of series active power filter with capability to protect sensitive loads against harmonics, sags, swells and unbalances of the power system voltages. Furthermore, in [17], the authors present an experimental evaluation of a digital control system based on a dual digital signal processor architecture for a three-phase UPQC; where the results show the minimization of delays caused by the processing time and the increment of the UPQC performance. On the other side, several control techniques have been proposed in the literature [5], such as the based on artificial neural networks to separate the harmonics in the nonlinear load [26; 27], which can present delays and large computation time. Other authors have used wavelet analysis techniques to represent a time-varying signal to control the UPQC [5], such as in [28] where a control strategy is proposed to extract the compensating signals for the control of series and shunt converters of the UPQC, or in [29] where it is used for power quality improvement with the UPQC. Other techniques based on \(pq\) and \(dq\) theories have been proposed [5], such as in [30] where the authors proposed a solution for power quality issues with the UPQC under-voltage and load unbalances conditions; or in [31], where the authors use a UPQC to inject a minimum active power and with limitations in the rated voltage capacities of the series compensators and the phase difference during voltage sags events; however these techniques use low pass and high pass filters that can affect the performance of the controller [5]. The literature shows that the UPQC has been used to improve power quality and the harmonics of the system; however; the control techniques have some disadvantages as large computation time and 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). The proposed control technique enables the UPQC to isolate the load from a harmonic-contaminated power supply and the momentary variations of the signals. At the same time, the current harmonics are eliminated and the power factor of the load is corrected, generating an ideal system at the common connection point. The designed model allows us to quickly implement the control technique as a prototyping system with a low computational cost. The classic discrete-time control has the advantage of obtaining a fixed commutation frequency [32] what for industrial application helps to reduce audible noise, size of electrical equipment, eliminate subharmonics in the output signal, and others. Besides, PID controllers are developed for the series APF, shunt APF, DC bus voltage, DC bus unbalance voltage, and PWM. The rest of the document is divided into four more sections. Section 2 describes the UPQC in dual topology, defining the detailed models of the series and shunt APFs. Section 3 presents the discrete controllers designed in the frequency domain and the 3D-SVPWM. Section 4 presents the results obtained from the application of the dual UPQC to a three-phase system. Finally, Section 5 presents the conclusions of the document. Figure 3: UPQC in dual topology.