การพัฒนาสมรรถนะของระบบควบคุมสำหรับวงจรปรับปรุงคุณภาพกำลังไฟฟ้ารวม

Abstract

This thesis proposes power quality improvement using a unified power quality conditioner (UPQC) in a balanced three-phase system. To improve the calculation of reference voltage and current, the harmonic identification by the power angle control method (PAC) has been developed with sliding window Fourier analysis (SWFA). In this thesis, the enhanced PAC algorithm is designed based on the apparent power control (UPQC-S). This approach is adopted to handle such as source voltage and load current problems. The unit vector template generation (UVTG) with PWM technique is applied to control the compensating voltage of the UPQC. In this work, the predictive controller is applied for the compensating current control on the dq-axis. This control is operated with the SVPWM technique to generate the switching state for the shunt active power filter. The predictive control with the SVPWM can provide good performance for the compensating current injection. The PI controller is used for the DC voltage bus control. The parameters of the PI controller are designed by using the root-locus technique in the z-plane. The proposed control strategy of UPQC is simulated using the processor in the loop (PIL) technique. For this technique, the MATLAB & Simulink program on the host computer is cooperated with the Code Composer StudioTM program for the eZdspTM F23885 board. The simulation results show that the proposed control strategy can mitigate the harmonic current, improve the power factor, and compensate for the voltage variations (sag and swell) in test cases. The performance indices for the power quality improvement are defined in the IEEE standard 519-2014. In addition, the predictive current control is tested to compare the performance of the harmonic current elimination with the SVPWM controller and the PI controller. After compensation, the predictive current control can provide better performance compared with those controllers even though the voltage source and the loads are changed. For the comparison study, the performance index is the percent of the current tracking error between the compensating current and the reference current.