A duplex ureter constitutes about 1% of the renal tract anomalies.A 39-year-old man presented with a 4-week history of left loin pain and microscopic haematuria. Investigation with a non-contrast CT KUB revealed a 6 mm non-obstructing calculus in the left distal ureter.Left ureteroscopy and lithotripsy was planned. However, ureteroscopy failed to identify the calculus. A double J ureteric stent was left in situ and the procedure abandoned in favour of further assessment with a CT urogram. Imaging surprisingly showed a left duplex ureter with the calculus in the non-stented ureter.Repeat ureteroscopy noted the second ureter opening within the distal intramural part of the stented ureter. The calculus was identified and laser lithotripsy performed. A double J stent was appropriately reinserted and removed 2 weeks later.Our case highlights the importance of contrasted imaging prior to performing ureteroscopy for calculus disease.
The increased number of nonlinear loads in the distribution system has caused a significant impact on its power quality in the form of higher harmonic distortion. The fast charging station (FCS) is an example of a powerful nonlinear load that is currently being widely promoted with the aim of supporting the continuous usage of electric vehicles (EV). The most common and cheapest method to minimize harmonic impact is through the use of a passive filter. This paper presents an optimal sizing and placement of a passive filter design based on the numbers of FCS installed in the distribution system. The MATLAB/m-file platform is used to model the power system harmonic flow, passive filter, and FCS. The control strategy used to minimize the total harmonic distortion (THD) due to the large number of FCS is presented based on the selection of optimal location and the size of passive filters that will provide minimum THD and apparent power losses to the overall distribution system. A Modified Lightning Search Algorithm (MLSA) technique is applied with the aim of identifying the optimal solution. The Pareto-Fuzzy technique is used to obtain a better solution among nondominated solutions. From the result, the optimal placements and sizes of passive filter will be able to reduce the maximum THD and also the total losses in the distribution system, which is equipped with 17 FCS units. This study is useful as a guide for grid owners to control the impact of large-scale FCS deployment in the distribution system.
This research is focusing on optimal placement and sizing of multiple variable passive filter (VPF) to mitigate harmonic distortion due to charging station (CS) at 449 bus distribution network. There are 132 units of CS which are scheduled based on user behaviour within 24 hours, with the interval of 15 minutes. By considering the varying of CS patterns and harmonic impact, Modified Lightning Search Algorithm (MLSA) is used to find 22 units of VPF coordination, so that less harmonics will be injected from 415 V bus to the medium voltage network and power loss is also reduced. Power system harmonic flow, VPF, CS, battery, and the analysis will be modelled in MATLAB/m-file platform. High Performance Computing (HPC) is used to make simulation faster. Pareto-Fuzzy technique is used to obtain sizing of VPF from all nondominated solutions. From the result, the optimal placements and sizes of VPF are able to reduce the maximum THD for voltage and current and also the total apparent losses up to 39.14%, 52.5%, and 2.96%, respectively. Therefore, it can be concluded that the MLSA is suitable method to mitigate harmonic and it is beneficial in minimizing the impact of aggressive CS installation at distribution network.
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