The doctoral thesis of the student Ahmed Yahya Qasim, University of Basra, College of Engineering, Department of Electrical Engineering, was discussed under the title:
Voltage Stability Improvement of Multi–Machines with Nonlinear Load System Using UPQC This study focuses on conducting a simulation of a three-phase, three-wire unified power quality conditioner with (IEEE 33 bus) systems.
The IEEE 57 bus standard and its representation using MATLAB-Simulink. The study also focuses on using the UVTG control method to control the series variator and using the UVTG and SRF control methods with a PI controller to control the parallel variator. The weakest areas of the IEEE 33 bus and IEEE
(PSAT) after representing the two networks using the program (QV modal) 57 using the bus analysis method. Where (P-V) curves were used to test the effect of compensation (UPQC) for the reactive power of both networks to improve voltage stability. Connecting (UPQC) in narrow areas led to a clear increase in the maximum effective power (Pmax) as well as an increase in the load power margin (LPM(P)) for all weak commons. At common (18), which is the weakest in the (IEEE 33 bus) system, () increased. LPM(P) from (1.344) to (2.486). Likewise, the IEEE 57 bus increased from (2.744) to (4.992) at common (33), which is the weakest in the LPM(P) system. This increase leads to improved voltage stability. In weak areas of both systems.
UPQC has been performance tested to address power quality problems in weak areas including distortion and loss
Balance the source voltage, droop and increase voltage up to 50% of the source voltage. Four different types of loads were used in the test: balanced linear loads, unbalanced linear loads, balanced nonlinear loads, and finally unbalanced nonlinear loads. (UPQC) achieved a balance in the load voltage and source current and kept the load voltage constant at the required value (1pu) while the voltage dropped to a value of (0.5).
pu) and when the voltage increases to (pu 1.5). UPQC also succeeded in reducing the harmonics of voltages and current, as the THD of the load voltage was reduced from (29.16%) to a value less than (4%) and the THD of the source current was reduced from (20.95%) to a value less than (4%). ) for all test cases to comply with the IEEE 519 standard.
UPQC effectively corrects the power factor by compensating the reactive power of the load
Power factor (pf=0.8 lag) The power factor improves to (PF=1) under all test conditions. Through test results, it has been proven that the Unified Power Quality Conditioner (UPQC) is an effective tool in addressing power quality problems
Improving voltage stability.
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