Step-down Power Research Articles

Data dimensionality reduction for an optimal switching mode classification applied to a step-down power converter

Abstract A dimensional reduction algorithm is applied to an intelligent classification model with the purpose of improving the efficiency and accuracy. The proposed classification model, used to distinguish the operating mode: Hard- and Soft-Switching, is presented and an analysis of the synchronized rectified step-down converter is done. With the aim of improving the accuracy and reducing the computational cost of the model, three different methods for dimensional reduction are applied to the input dataset of the model: self-organizing maps, principal component analysis and correlation matrix. The obtained results show how the number of variable is highly reduced and the performance of the classification model is boosted: the results manifest an improve in the accuracy and efficiency of the classification.

Extending the lower bound of attainable load-independent voltage gain values range in contactless, feedbackless and sensorless power delivery links

It is well-known that series(capacitive)-series(capacitive) compensated inductive wireless power transfer links (SS(CC)-IWPTL) operating at fixed frequency with constant coupling coefficient may be designed to attain arbitrary load independent voltage gain (LIVG) value, residing within a region defined only by loosely coupled transformer (LCT) parameters. Such a characteristic allows designing the system to be sensorless and operate without feedback, which is an extremely useful feature in hostile environment applications. Unfortunately, LCT parameters are not selected arbitrarily in practice; hence, the desired LIVG value may reside outside the attainable region, calling for an additional power conversion stage. In particular, region of attainable LIVG values is especially narrow when LCT inductances ratio is imposed by the application and thus cannot be freely selected. One of existing challenges is regulating the system output to low DC voltage while it is being fed from a much higher valued voltage source, i.e. calling for an extremely low LIVG value. The paper demonstrates that adopting an inductor rather than a capacitor as primary series compensation element allows to extend the lower bound of attainable LIVG values region for given LCT and operating frequency, potentially eliminating the need for an additional step-down power converter. Resulting coil-to-coil efficiency is quantified and guidelines for sizing corresponding compensation elements pair are established as well. Simulations and experiments accurately verify the proposed methodology.

An efficient high-gain bidirectional interleaved boost converter for PV integration to DC microgrid.

The design of a power electronic interface for high voltage difference DC buses is a key aspect in DC microgrid applications. A multi-port non isolated interleaved high-voltage gain bidirectional converter, which facilitates bidirectional power transfer and islanded operation in a DC microgrid, is presented in this paper. The forward high-voltage transfer ratio is achieved using a voltage multiplier circuit, and the high-gain step-down power conversion is performed using a resonant power module. A novel power transfer selection algorithm is proposed to control power flow among the interfaces of the RES, ESS, and DC grid converters, which utilizes the net power difference as the basis for switching the converter. The proposed converter is simulated for a 24 V PV source, 12 V battery, and 400 V DC grid interface using MATLAB/SIMULINK. A 200 W hardware prototype is implemented. The simulation results for voltages, currents, and power flow among RES, ESS, and microgrid DC bus proved an excellent voltage regulation, efficient power conversion, and a feasible duty cycle range with high voltage gain. These observations are validated through equivalent experimental results. A comparison is made regarding achieved gain, component sizing, achievable power transfer modes, efficiency, and control complexity with existing converters for DC microgrid applications. The presented topology proved to be a better interface with multiple-mode support with high efficiency.

A Control Design Technology of Isolated Bidirectional LLC Resonant Converter for Energy Storage System in DC Microgrid Applications

This paper presents a new control method for a bidirectional DC–DC LLC resonant topology converter. The proposed converter can be applied to power the conversion between an energy storage system and a DC bus in a DC microgrid or bidirectional power flow conversion between vehicle-to-grid (V2G) behavior and grid-to-vehicle (G2V) behavior. Furthermore, such a converter can be applied to energy storage systems for decentralized renewable energy generation systems, such as solar and wind power. In addition, this converter can be combined with a bidirectional inverter to allow energy storage in the system to improve the safety, stability, and power quality of the microgrid. In the proposed circuit structure, we use a bidirectional DC–DC LLC, which has the advantages of a higher voltage conversion ratio, lower part count, simpler control than similar converters such as DAB, CLLC, and L–LLC converters, and bidirectional power flow and electrical isolation. Specifically, to extend the battery life, it can be employed as a control strategy for discharging the energy stored in the battery (SOC) and reducing the temperature rise generated by the internal solid electrolyte interphase (SEI) when discharging the battery under the variation in distributed energy resource (DER) generation and load demand. To realize the bidirectional power conversion without using any auxiliary inductor and only changing the control strategy, the forward step-down power conversion was based on pulse frequency modulation (PFM) control, and the reverse step-up power conversion was based on pulse width modulation (PWM) control. In this paper, we introduce the bidirectional converter topology and its control strategy for the DC microgrid battery energy storage system. Finally, a 500 W prototype is built to verify the effectiveness of the proposed converter.

Three-Port Converter With Leakage Inductance Energy Recycling for High Step-Down Applications

An emerging revolution in electric vehicles (EVs) is rapidly taking over the traditional fossil fuel vehicle market. Given its safety features and user-friendliness, the dual battery system (DBS) has been adopted in various EVs. A step-down three-port converter is essential for the DBS to supply low-voltage auxiliary power in EVs. In this paper, a novel high step-down three-port converter (TPC) is proposed by integrating the tapped-inductor technique and a buck converter for fulfilling the requirements of high step-down power conversion from sources to load with a reasonable duty cycle. It can also achieve independent power transfer among three ports. In addition, the energy stored in the leakage inductance of coupled inductor is recycled, with voltage spikes reduced across the switches. Finally, an experimental prototype is built to verify the theoretical analysis, with a main battery of 300 V, auxiliary battery of 48 V, load voltage of 24 V, and rated power of 300 W. The highest efficiency reached is 96.6%.

Arduino Based Pick and Place Robot with Robotic Arm for Industrial Use

This paper presents an Arduino-based pick and place robotic system for industrial use, featuring a microcontroller (Arduino Mega 2560) and a robotic arm. The system aims to automate various tasks and eliminate human error. Pick and place robots have found applications in industries such as bottle filling, packaging, bomb disposal, etc. Our project utilizes Robo Arduino to implement the pick and place mechanism, controlled by RF signals. The robotic arm, supported by a chassis with four Omni wheels, offers two degrees of freedom. Additional features include line following, wall detection, obstacle avoidance, and sensor integration. The key components include Arduino Mega 2560 as the microcontroller, 6 DOF metal mechanical arm, 4WD smart chassis kit, L298N H-Bridge dual motor driver, MG996R servo motor, PCA9685 servo driver, LM2596 DC-DC step-down power module, 11.1V 1100mAh 3S 30C lithium-ion battery, infrared wireless control kit, and jumper wires for component connections. We believe that our project will have a significant impact on industries in this era of technological revolution.

Silicon Power Interposer Technology (PIT) for Integrated Power Converter

Future generations of power converters must be miniaturized to power future electronic devices that are getting smaller and smarter. Monolithic integration is an ideal approach toward compact, efficient, and low-cost converters. This letter addresses two technology gaps in packaging technology and integrated inductor technology using the so-called power interposer technology (PIT). We implemented a step-down power converter to demonstrate PIT. The converter uses two GaN FETs, capacitors, and a gate driver stacked on a 0.28-mm-thick silicon die that hosts a 3D substrate-embedded toroidal microinductor. The converter switches 22 MHz in zero-voltage-switching mode achieving a peak efficiency of 83% at the full load of 1 W. PIT has shown unique technology advantages for future generations of integrated power converters, including high power density, low profile, superior thermal performance, scalability, and heterogeneous integration. Furthermore, PIT holds great commercial potential for high-power-density integrated power converters.

GaN-based step-down power converter and control strategy for hydrogen energy systems

The conventional Si-based semiconductors suffer from low switching frequency, high conduction loss and low efficiency. These shortcomings hinder the improvement of power electronic power converter performance. An attractive solution is to replace Si-based semiconductor devices with the wide-bandgap semiconductors based on gallium-nitride material. In terms of the step-down converters which are used for hydrogen energy systems, it is difficult for the traditional buck circuit to eliminate the output current ripple and achieve fault-tolerant operation. Therefore, topologies of the step-down power converter also need improvement. In this paper, a GaN-based step-down power converter and control strategy for hydrogen energy systems is presented. Firstly, the mathematical analysis of the conventional buck converter is done to clarify why it has limitations regarding the reliability and current ripple. Another alternative solution is discussed but still suffers from ripples. In order to eliminate the current ripple and enhance the fault-tolerant ability, a novel GaN-based solution is given and both analysis and design are provided. The current ripple can be perfectly cancelled and fault-tolerant operation can be fully achieved. The comparison is carried out with the existing solutions. The time-domain simulation tests are carried out. And the experimental prototype is established based on the enhancement mode GaN transistor. The experimental results verify the effectiveness of proposed design regarding the current ripple cancellation and dynamic performance.

A Direct Single-Phase to Three-Phase AC/AC Power Converter

The traditional DC-link indirect AC/AC power converters (AC/DC/AC converters) employ two-stage power conversion, which increases the circuit complexity along with gate driving challenges, placing an excessive burden on the processor while implementing complex switching modulation techniques and leads to power conversion losses due to the use of a large amount of controlled power semiconductor switches. On the contrary, the traditional direct AC/AC voltage controllers, as well as frequency changers, suffer from high total harmonic distortion (THD) problems. In this paper, a new single-phase to three-phase AC/AC step-down power converter is proposed, which utilizes a multi-linking transformer and bilateral triode thyristors (TRIACs) as power semiconductor switches. The proposed direct AC/AC power converter employs single-stage power conversion, which mitigates the complexity of two-stage DC-link indirect AC/AC converters and traditional single-stage AC/AC frequency changers. Instead of using high-frequency pulse width modulated gate driving signals, line frequency gate pulses are used to trigger the TRIACs of the proposed AC/AC converter, which not only aids in reducing the power loss of the converter but also mitigates the cost and complexity of gate driver circuits. The proposed AC/AC converter reduces the THD of the output voltage significantly as compared to traditional direct AC/AC frequency changers. The performance of the proposed AC/AC converter is validated against RL and induction motor load in terms of overall THD and individual harmonic components through MATLAB/Simulink environment. A reduced-scale laboratory prototype is built and tested to evaluate the performance of the proposed AC/AC power converter. The experimental and simulation outcomes reveal the feasibility and excellent features of the proposed single-phase to three-phase AC/AC converter topology.

A 12V/24V-to-1V PWM-Controlled DSD Converter With Delay-Insensitive and Dual-Phase Charging Techniques for Fast Transient Responses

A 12V/24V-to-1V pulsewidth modulation (PWM) controlled double step-down (DSD) power converter with delay-insensitive and dual-phase charging techniques is presented. The proposed PWM controller has two feedback loops to regulate the output voltage and the voltage across the flying capacitor, respectively. With the proposed delay-insensitive technique, near-optimal transient responses are achieved by using the PWM control regardless of the time of occurrence of the transient. Moreover, the responses are further improved by two times by using the proposed dual-phase charging technique. The converter was fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> BCD process with all power transistors integrated on chip. For 12V-to-1V conversion and 24V-to-1V conversion, the measured peak efficiencies at 1-MHz switching frequency are 88.3% and 83.5%, respectively. With a load current step of 3 A and a rise time of 20 ns, the measured voltage droop and 1% settling time are 56 mV and 0.9 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> , respectively.

A Transformerless AC-AC Converter with Improved Power Quality Employed to Step-Down Power Frequency at Output

Variable voltage and frequency are required to govern the torque-speed characteristics of many industrial drive systems. Traditionally, this is achieved with a power converting system implemented with multistage converters. This technology is based on rectifying AC power into DC and then DC into AC with an inverter circuit. The power quality concerns of both conversion stages are tackled by selecting high switching frequency PWM control and harmonics mitigation filters. Also, using a bulky DC-link capacitor is one of the big sources of low system reliability, so this approach increases the conversion losses, circuit, and control complications. The frequency step-down conversion is very attractive with direct AC-AC converters as it has a simple control and circuit structure, but these converters face poor power quality challenges once the output frequency is decreased with respect to an input. In these converters, the total harmonic distortion (THD) of the output voltage becomes very poor once the output frequency is reduced. The problem of high THD of the output is addressed in the power converting circuits implemented with line frequency multi-winding transformers. The required number of output winding and switching devices (diodes and thyristors) increases once the value of the output frequency is decreased. This will increase the overall volume, cost, and losses. The use of a bulky and costly line frequency transformer may be eliminated if AC voltage controllers have non-inverted and inverted voltage buck capabilities, such existing topologies either have complex control schemes or require a large number of operating devices. Therefore, in this research article, a new transformerless frequency step-down converter employing fewer devices is proposed. This approach is realized with a high-frequency controlled rectifier for the required voltage stabilization and a low-frequency inverter bridge for frequency control. Its validation is supported by the results attained from Simulink and practical-based prototypes.

Direct 12V/24V-to-1V Tri-State Double Step-Down Power Converter With Online V CF Rebalancing and In-Situ Precharge Rate Regulation

In response to fast-growing high-voltage (HV) power IC market demands, this article presents a tri-state double step-down (DSD) power converter to achieve direct 12V/24V- to-1V dc-dc power delivery with high efficiency and high power density. By taking advantage of the benefits from both three-level and DSD converter topologies, the converter allows the use of lower voltage rating power devices and thus facilitates high switching frequency operation with smaller power passives. An online flying capacitor voltage ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CF</sub> ) rebalancing scheme is introduced to optimize switching nodes voltages and minimize power path mismatch for improved reliability and efficiency. During startup transients, an in-situ precharge rate regulation technique manages the charging process on flying capacitors precisely in avoidance of potential device breakdown. An IC prototype of this design was fabricated using a 180 nm HV bipolar-CMOS-DMOS (BCD) process with an active area die of 6.3 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At 3-W output power, a chip power density of 476 mW/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is accomplished. The online V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CF</sub> rebalancing reduces voltage mismatch between the flying capacitors by 16.7%. The converter achieves peak efficiencies of 88.3% and 92.1% for 24V/1V and 12V/1V conversion, respectively.

Protection of power transformers against the effect of magnetic storms

Abstract In the operation of large-scale power systems for the long-distance transmission of large amounts of electricity, a number of cases have been reported in which anomalies in the Earth’s magnetosphere, referred to as geomagnetic storms, have caused a severe system collapse. Changes in the geomagnetic field cause a semi-saturating phenomenon, in which the high-voltage lines and especially the high-voltage windings of the power transformers of the system are overloaded with current and subsequently also thermally. The present article briefly explains the physical nature of magnetic storms and then describes a new device that either eliminates the possibility of a step-down power transformer accident or significantly reduces its effects on the system. The essence of this device are frequency filters, which are connected in parallel to the high-voltage windings of power transformers. At the beginning of a geomagnetic storm, the frequency filter is automatically connected to the system and is automatically disconnected when it subsides. The operation of frequency filters does not require human intervention, acquisition and operating costs are low and their integration into existing power systems is easy.

To restrict the AC compressor starting current using a multi-winding power transformer, in PV based battery-less evaporation-distillation water treatment system

In this paper, a combined water treatment system that uses both reverse osmosis process (R.O.) and evaporation-distillation process (E.D.) sequentially is studied. The electrical supply of the process is a 1.1 kW battery-less photovoltaic system. One major problem here is the system's inability due to start-up electric motors, which the largest one is an AC compressor. As a result, voltage of different parts of the system falls at compressor starting moment, leading to under-voltage lockout function to operate in power converters. This will make the power converter output shut down for a second. Eventually, the compressor will not start to run and the system may get totally unstable. This paper proposes a starting step-down power transformer to run the AC compressor, and pass the starting moment. The transformer turn ratio is determined so that the compressor start with the least possible voltage. This will prevent system instability and PV operating point hanging situation. After the start-up moment, a mechanical switch will trigger the compressor to the nominal voltage to reach the nominal torque and speed at steady state. The experimental results shows that using a starter transformer can effectively strict the compressor's inrush current and prevent the PV-based system instability.

Design a three-phase step-down power supply based on ANSI/IEEE standard

An alternating current three-phase step-down power supply design is a system development process that creates an existing three-phase system whereby the primary side of the Y relationship and the secondary side of the Y relationship. The problems in the design of three-phase step-down power supply circuit are the existence of harmonics, losses and unbalance voltage. The power supply test is carried out using no-load and linear load resistance with the value of resistances in range of hundreds ohm. The circuit is tested for resistance number one, resistance number two, resistance number three and resistance number four transformers to obtain a power supply design that meet American National Standards Institute or Institute of Electrical and Electronic Engineering standards. The test results of four transformers in the form of three-phase step-down found that resistance number one and resistance number two type transformers have the lowest copper loss percentage, core loss, voltage THD and low unbalance voltage, so that these power supply can be made according to ANSI/IEEE provisions.

Mathematical Models of the Operating Modes of Power Autotransformers

The mathematical description of operation and voltage regulation of step-down and step-up double-wound power autotransformers has been considered. It has been shown that the available mathematical models of step-down and step-up double-wound autotransformers do not reflect the true physical meaning of its operation. The idling modes and operation under load of a double-wound power autotransformer have been considered, and systems of equations of its operation in up and down modes have been created. The systems of equations refine the existing mathematical models, satisfy the classical representation of physical processes of autotransformer operation, and are universal for description of the idling modes and operation under load. Vector diagrams of autotransformers have been constructed on the basis of the suggested systems of equations.

A Wide-Input-Range High-Efficiency Step-Down Power Factor Correction Converter Using a Variable Frequency Multiplier Technique

This paper demonstrates a two-stage implementation of a step-down power factor preregulator design that achieves a high efficiency across the entire universal input voltage range ( $\text{85}\text{--}\text{265}\,\textrm {V}_{\textrm {rms}}$ ) for an offline power supply application. In this implementation, a resonant LLC converter supplies power to a boost converter operating in a continuous conduction mode. A variable frequency multiplier technique is used in a resonant LLC converter stage to provide different dc gains and compress the effective input voltage range. The efficiency performance achieved is flatter and higher than other conventional offline power converter design consisting of a boost power factor correction circuit followed by a resonant LLC converter, whose efficiency tends to drop significantly at low-line input voltages. The proposed circuit allows MOSFETs with lower voltage ratings and better conduction/switching characteristics to be used in both converter stages. Both of the LLC stage and boost circuit can be better optimized due to the compressed operation range and better semiconductor switches. A scaling law of power losses versus breakdown voltage requirement for boost circuit under the condition of the same output power is presented. Experimental results demonstrated a flatter high efficiency performance across a wide input range.

Characteristic frequencies in averaged description of step-down (BUCK) DC-DC power converter

AbstractIn the description of small-signal transmittances of switch-mode power converters several characteristic frequencies are usually used, corresponding to poles and zeros of transmittances. The knowledge of these frequencies is important in the design of control circuits for converters and usually are assumed to be constant for a given power stage of a converter. The aim of the paper is to evaluate the influence of converter primary parameters and load conductance on characteristic frequencies. Analytical derivations and numerical calculations are performed for an ideal and non-ideal BUCK converter working in continuous or discontinuous conduction mode.

Bridgeless single‐phase step‐down PFC converter

This study presents a bridgeless single-phase step-down power factor correction (PFC) converter. The proposed converter consists of a buck converter in positive half-line cycle and a flyback converter in the negative one. The dead angle of input line current is omitted so high power factor (PF) and low total harmonic distortion (THD) are obtained. There are just two simultaneously conducting semiconductor devices in the charging path of buck and flyback inductors that reduce the conduction losses. A 80 W, 24 V experimental prototype verifies the operation of the proposed rectifier and a PF of 0.995 and THD <;10% can be achieved.

Forensic Engineering Analysis of a Sequence of Power Infrastructure Failures Atop an Office Building

A series of equipment failures occurred in a high-rise office building in Puerto Rico. The top 18th floor was occupied by the infrastructure systems of the building to include heating, air conditioning, electrical and plumbingsystems, and two 1,500kVA emergency generators that provided power for the entire building when the utility power was not available. The first failure occurred within a 3,000kVA, 13.8kV/480-277VAC stepdown power transformer on a Sunday night — a day after the annual maintenance of the electrical equipment took place. Thefailure of this transformer resulted in the operation of the two emergency generators — last maintained a month earlier. The second failure occurred in one of the two control panels associated with the fuel day tanks for the emergency generators due to power disturbances (harmonics) in the electrical distribution system in the building. This resulted in an overflow of fuel oil in one of the day tanks (615 gallons) and the spill of approximately 1,000 gallons of fuel oil on the 18th floor and lower floors (including the cellar).