AC Power Switch Research Articles

Modeling of a New Super-Gain BJT and an innovative Low-loss AC Switch based on Gummel-Poon model

This article gives a modeling method based on the Gummel-Poon model for the Super-Gain BJT developed in the GREMAN laboratory. First of all, the extraction principle, mathematical calculating method, and final extraction results of each model parameter will be presented. Secondly, the Gummel and Voltage-Current output curves for a single Super-Gain BJT, which are carried on in Pspice with the extracted parameters in the first part, will be drawn and be compared with experimentation results. At last, a new 600V AC switch that is composed of two single Super-Gain BJTs connected in anti series is simulated. To explain and reduce the error between the simulated results and experimental ones in hi-level injection, a new model with a dynamic resistance based on that of Gummel Poon is proposed and validated. Consequently, all of simulations have an error less than 10%, proving the good precision of the models as well as the characteristics of the new AC power switch.

Development of a Smart Static Transfer Switch Based on a Triac Semiconductor for AC Power Switching Control

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.

DC–DC converter implementation with wide output voltage operation

A direct current (DC) to DC converter with soft switching and high efficiency is developed for industry power units with a wide range of output voltage applications. A series resonant converter is the main circuit on the primary side to accomplish the soft switching characteristics for the active devices and rectifier diodes without switching loss or reverse recovery current loss. To overcome the drawback of the limited operation input or output voltage range in conventional LLC converters, a hybrid resonant converter including a half-bridge circuit and a full-bridge circuit with auxiliary windings is developed to achieve 8:1 (Vo,max = 8Vo,min) output voltage characteristics for a wide range of output voltage applications. To achieve this function, two AC power switches are used in the developed circuit. Since a single-stage hybrid resonant converter is presented instead of a two-stage converter to realize wide voltage range operation, the developed circuit has better efficiency when compared to conventional LLC converters and two-stage DC–DC converters. To confirm the circuit analysis and effectiveness, a prototype with a 400 W rated power was built and tested.

An Experimental Investigation of Electrical Clearance in Air for Overhead Traction System

While converting the existing rail network to electric traction, provision of specified minimum requirement of air gap clearance under old bridges and tunnels has always posed problems. Demand in specified electrical clearance of air-gap often forced the Indian Railways in construction of new bridges for the traction overhead lines to pass when the existing bridges still had their life left, which resulted in very high cost of electrification schemes. Extensive experimental investigation work is presented in this article for the performance of air-gap on actual catenary of contact wire assembly. Measurements were made under natural conditions of rain, fog, fair weather and under artificial rain with ac power frequency, lightning and switching impulse voltages. Investigations were also performed with the insertion of a solid insulating barrier in the gap. Considering the severest condition that of stream of water falling directly on the live conductor from the grounded object, the requirement for minimum air-gap clearance could be recommended to reduce to 170 mm for short time and 220 mm for long time applications, which is 37% lower than the air-gap clearance practiced hitherto. Development of twin contact wire assembly forming horizontal bundle is recommended for reducing the air-gap clearance further.

Effects of SiO2 and TiO2 Nano Fillers in Enhancing the Insulation Breakdown Strength of Epoxy Nano Composite Dielectric under Divergent Electric Fields

The proper mixing of nanoscale fillers in conventional dielectric materials leads to an enhancement in the breakdown strength and voltage endurance. In this study experimental investigations are carried out to compare the breakdown characteristics of epoxy nano-composites with that of a base epoxy resin under the influence of divergent electric fields so as to obtain inferences on its breakdown performances. This would in turn enable providing solutions to acquire more effective electrical insulation systems and explore the prospect of tapping the merits of utilizing the rapid strides made in field of fabrication of nano-dielectrics. The main objective is such studies are to enhance the electrical properties of the epoxy dielectric by employing nano-fillers such as SiO2, TiO2 etc. This research envisages the use of epoxy resin mixed with nano-fillers for ascertaining the ability of the nano-composite to be utilized as a dielectric/ insulator in power apparatus. The epoxy resin is mixed with appropriate proportion of SiO2 and TiO2 and experimentation is carried out under the influence of divergent electric fields. Classical breakdown voltage withstand tests such as AC power frequency, DC voltage, lightning impulse and switching impulse test is carried out on epoxy dielectrics (with and without nano-fillers) and the results are compared. In addition, a non-classical breakdown voltage test (high frequency high voltage) is also devised to analyze and ascertain the breakdown characteristics due to varying frequencies so as to investigate the possibility of utilizing such nano-composites in applications related to high speed switching devices.

Design of Power Switching and Distribution Circuits for Solar Power Generation

With the development of clean energy, switching and distribution issues in a photovoltaic system are getting much attention in recent years. This paper designs a DC to AC inverter and power switching and distribution system between a solar power system and the municipal system by using the Darlington amplifier structure with the photosensitive resistor and accompanying relays, and details the system circuits. The proposed system can achieve a stable output of 110 V AC, as well as self-generating driving voltage and switching between the municipal electrical system and the solar power system. The mathematic analysis and actually test results demonstrate that the proposed method is an easy, inexpensive, and low cost way to build a solar power switching and distribution system.

Analysis and implementation of a three-phase four-wire switching mode rectifier based on a switch-clamped scheme

In this paper, a three-phase four-wire switching mode rectifier with a hysteresis current control strategy is proposed for improving the power factor and reducing current harmonics. The proposed circuit configuration is based on a three-level switch-clamped scheme to reduce the voltage stress of the AC power switches. Three voltage levels are generated on the phase-to-neutral voltage of the proposed rectifier. The purposes of the proposed control strategy are to correct the voltage imbalance of the DC bus capacitors, to draw the sinusoidal line currents with a nearly unity power factor and to keep the constant DC-link voltage. Applications of the proposed circuit can be used in the AC/DC/AC converters, active power filter and voltage sag compensator. Characteristics of the rectifier are examined and the validity is verified by simulation and experiments based on a laboratory prototype circuit.

Implementation of the AC∕AC converter based on neutral-point switch-clamped topology

A single-phase AC/AC converter based on neutral-point switch-clamped topology is proposed. The adopted AC/DC converter is controlled to have a stable constant DC bus voltage and draw a sinusoidal line current with unity input power factor. The AC side voltage of the AC/DC converter is controlled to generate a unipolar PWM waveform using the conventional half-bridge PWM rectifier and one AC power switch with voltage stress vdc/2. A carrier-based current control scheme is used in the inner control loop to track the line current command. A proportional-integral (PI) control is adopted in the outer control loop to maintain the constant DC bus voltage. On the inverter side, a sinusoidal output voltage is generated to provide a stable and clean source voltage to the critical load. A fixed-frequency current controller is adopted to generate the proper PWM waveform. A conventional half-bridge PWM inverter with one AC power switch is used in the DC/AC converter to generate the unipolar PWM voltage waveform on the AC side. The system model and control algorithm are described and analysed. To verify the effectiveness of the proposed operation scheme, experimental results based on a laboratory prototype were performed.

High-power-factor single-phase switch clamped rectifier

A high-power-factor rectifier based on a neutral point switch clamped scheme is presented. A control scheme for the proposed rectifier is propounded to draw a sinusoidal line current with nearly unity power factor, achieve balanced neutral point voltage and regulate the DC bus voltage. An AC power switch is employed in the power circuit to generate a three-level pulsewidth modulation voltage on the AC terminal. A hysteresis current control scheme is used to track the line current in phase with the mains voltage. The fine current command is derived from a voltage controller and a phase-locked loop circuit. A capacitor voltage compensator is employed in the proposed control algorithm to achieve the balanced neutral point voltage. To investigate the effectiveness of the proposed control scheme, experiments based on a laboratory prototype circuit are performed.

A single-phase three-level pulsewidth modulation AC/DC converter with the function of power factor corrector and active power filter

Abstract A single-phase three-level pulsewidth modulation (PWM) AC/DC converter with the function of power factor corrector and active power filter is proposed to reduce harmonic currents flowing into the power system and to draw a nearly sinusoidal current with unity power factor. The circuit topology of the adopted three-level PWM AC/DC converter is based on a conventional two-level full-bridge rectifier and one AC power switch. The control signals of the power switches are derived from the voltage balance compensator, current controller and detected operation region of mains voltage. A three-level PWM voltage pattern on the AC side of the converter in each half cycle of mains frequency is generated. Computer simulations are implemented to confirm the operation of the adopted converter with the function of power factor corrector and active power filter.

Using Boundary Scan Test Method for High Tech Industrial Equipment

The goal of this paper is to present the use of boundary scan testing method for high tech industrial equipment - the cargo system controller (CSC) for the Boeing 777 aeroplane. For testing purposes of the (CSC), a station containing a computer equipped with a GPIB controller, an AC and DC power source, digital multimeter, function generator, scope, switch matrix, VXI rack and Tektronix Serial Test Module were used. Both the method and the algorithm used for testing the CSC are presented. This paper also emphasises the advantages obtained due to the use of FPGAs Xilinx 4010 in the testing scheme.

Single‐phase three‐level PWM rectifier with power‐factor correction

AbstractA novel control strategy for single‐phase unidirectional switching‐mode rectifier (SMR) that draws a sinusoidal line current in phase with the supply voltage is proposed and discussed in this paper. In the adopted circuit topology, two AC power switches are placed between the AC side of the SMR and the center‐tapped terminal of the DC‐link capacitors. The control schemes are based on the hysteresis current control (HCC) technique and the simple look‐up table. The control schemes, stored in a programmable array logic (PAL), are implemented such that the line current is driven to follow the current command. There are three voltage levels (uDC, uDC/2, 0) on the AC side of the rectifier in each half cycle. The blocking voltage of each AC power switch is clamping to half of the DC‐link voltage. Software simulations and experimental circuits are implemented and measured to verify the proposed control strategy.

A new control scheme for single-phase PWM multilevel rectifier with power-factor correction

A new control scheme for a single-phase bridge rectifier with three-level pulsewidth modulation is proposed to achieve high power factor and low current distortion. The main circuit consists of a diode-bridge rectifier, a boost inductor, two AC power switches, and two capacitors. According to the proposed control scheme based on a voltage comparator and hysteresis current control technique, the output capacitor voltages are balanced and the line current will follow the supply current command. The supply current command is derived from a DC-link voltage regulator and an output power estimator. The major advantage of using a three-level rectifier is that the blocking voltage of each AC power device is clamping to half of the DC-link voltage and the generated harmonics of the three-level rectifier are less than those of the conventional two-level rectifier. There are five voltage levels (0, /spl plusmn/V/sub DC//2, /spl plusmn/V/sub DC/) on the AC side of the diode rectifier. The high power factor and low harmonic currents at the input of the rectifier are verified by software simulations and experimental tests.

Low crosstalk packaging design for Josephson logic circuits

Theoretical and experimental studies are accomplished for inductive crosstalk noise reductions at Josephson chip-to-card connectors. This noise is induced by large AC power and high switching speed signal currents. The crosstalk mechanism was analyzed using a Partial Element Equivalent Circuits Model. Ground inductance causes not only crosstalk noise between connectors but also ground fluctuation noise inside the chip. This ground noise is large enough to cause false logic operations. Test chips and cards with improved connectors were produced for an experimental evaluation. Power crosstalk noise was measured using Josephson sampling circuits fabricated on the chip. The crosstalk noise - signal level ratio was less than 2.5%, when 250 MHz, 50 mA power currents were supplied. Crosstalk noise between neighboring signal connectors was also reduced to negligible level, including the worst case. These results favorably agree with calculations. This low crosstalk packaging design can be applied to high speed Josephson logic systems.