Power system disruptions can be categorized as issues with the quality of electricity brought on by voltage sags, lightning strikes, and other system-related interferences. The static transfer switch (STS) has recently emerged as the most important technology for electric power transmission, distribution, and control systems to manage power supply during power system disruption issues, particularly in cost-effectively supplying power to critical loads and sensitive loads without interruption. In this paper, for the switching between the two AC sources during the voltage disruptions issue with low transfer time, a smart static transfer switch (SSTS) based on a digital switching algorithm and Triac semiconductor switch is proposed and experimentally tested. A digital switching algorithm based on online AC voltage sensing and zero-crossing detection is proposed and implemented inside a DSP MCU. The printed circuit board (PCB) of the proposed SSTS is designed and manufactured for the experimental performance investigation with different AC input voltage conditions. A comparative study based on the advantages and disadvantages of the proposed SSTS system with the previous works is also presented. A smart static transfer switch with a transition time of less than one cycle and a digital protection technique during fault conditions is obtained in this work.

The power factor correction (PFC) converters built for telecom applications must meet certain standards in order to keep the total harmonics distortion (THD) at the specified low levels to reduce the current stresses, reduce the power losses and hence increase the converter efficiency and input power factor (PF). Thus, in this paper, the small-signal stability models of the telecom bridge and bridgeless PFC converters are derived and based on the derived stability models, the fast-dynamic response integral-proportional (IP) current control technique is proposed to improve the control loops performance around the current waveform zero-crossing point, reduce zero crossing distortion (ZCD), reduce the THD, and reaches the input current PF near to unity. The digital simulation modeling using PSIM software of the 2.5 kW bridge and bridgeless PFC converters is performed to show the converter's performance with the proposed current technique as compared with the conventional proportional-integral (PI) control technique. The proposed current controller in this work improves the current control loop performance, reduces the ZCD period, reduces the THD to about 5% and reaching converters input PF near unity in both bridge and bridgeless PFC converters.

In this paper, a two-stage AC-AC power supply is designed to specifically handle the operation and performance improvements of the power system with highly inductive loads. The proposed power supply scheme includes an input interleaved power factor correction (PFC) stage to improve the input power factor (PF) and regulate the DC bus voltage required for the second stage, which is a voltage source inverter (VSI) with an output low pass filter to adjust the load harmonics contents and regulate the load voltage and frequency to the specified AC load values. The small-signal models of the PFC and VSI stages are obtained, and optimal voltage and current control loops for both stages are designed based on the obtained models to improve the required system power performance and stability. PSIM simulation is used to examine the performance of the proposed power supply under various input-output operation conditions. This work achieves a 500VA, (180-260)V RMS Power supply with an input PF of 99%, better output voltage regulation, and a lower THD value for the purpose of supplying industrial inductive loads.

The adoption of 5G technology in communications necessitates an increase in supply power factor and conversion efficiency to improve power quality. A two-stage AC-DC power supply with a power factor correction (PFC) stage and a DC-DC converter stage is the best option for supplying power to these loads, with the PFC stage's optimized design offering a high power factor and the DC-DC stage's optimized design offering low voltage and current stresses, low thermal and conduction power losses and then high conversion efficiency. Thus, an optimized design and manufacturing technique for the magnetic components, including the high-frequency (HF) transformer and inductors are proposed in this paper for the telecom power supply second stage to offer operation with zero voltage switching (ZVS), improve conversion efficiency, reduce voltage and current stresses, and maintain the load voltage and current ripple contents at the standard levels. Loss analysis is performed on all designed magnetic power components. The performance of the developed converter with the optimized design components is investigated using PSIM simulations and experimental verification.

Power quality in terms of power factor (PF), efficiency, and total harmonic distortions (THDs) is an important consideration in power supplies designed for 5G telecom servers. This paper presents a different magnetic parts design and manufacturing techniques of power supplies, design and selection criteria of switching elements as well as the optimal design of control loops based on small-signal stability modeling and an appropriate stability criterion. The designed telecom power supply consists of the power factor correction (PFC) stage to increase the input power factor and the isolated phase-shift pulse width modulation (PWM) zero-voltage switching (ZVS) DC-DC converter stage to regulate the supply voltage to the specified load value while maintaining a high conversion efficiency. A two-stage outdoor telecom power supply with a power rating of 2 kW was designed and fabricated on a printed circuit board (PCB). The distinct two-stage power components of the power supply were subjected to loss analysis. Furthermore, PSIM simulation and experiments were used to demonstrate the total harmonic distortions (THDs), voltage ripples, power efficiency, and PF performance of the supply current for the proposed power supply under various operating situations. This work produces an industrial high power density power supply with a high PF, low THD and high conversion efficiency which is suitable for telecom power server applications.

The brittle behavior traditional directly welded connections of steel beams to concrete-filled steel tube columns is caused primarily by excessive out-of-plane deformation of the tube walls at the level of the beam tension flange. To address this issue, this study proposes a reference connection that involves fillet welding a built-up steel beam directly to the corner of a diamond-shaped concrete-filled steel tube (DCFST) column. Two options are suggested for enhancing the seismic performance of the reference connection: a predrilled hole with a 12-mm diameter at the midwidth of each beam flange, or a rib stiffener reinforcement on the outside of each beam flange. The two proposed specimens and a traditional directly welded connection were subassembled and investigated experimentally. The results showed that the reference DCFST connection significantly improved the seismic response of the directly welded connection in terms of initial stiffness, strength, ductility, and energy-dissipating capacity. Specifically, the initial stiffness and strength capacity increased by over 150% compared with that of the traditional connection counterpart. Furthermore, the rib stiffeners contributed to further enhancement of the seismic response by shifting the beam plastic hinge away from the column face. Overall, these findings suggest that the use of DCFST connections is reliable for composite moment-resisting frames (C-MRFs), and the proposed enhancements can improve the seismic performance of these connections significantly.