Turns Ratio Research Articles

New Structure of Single-Switch Ultra-High-Gain DC/DC Converter for Renewable Energy Applications

This study introduces a new modified high-gain single-switch single-ended primary-inductor converter-based dc/dc converter. The low input ripple of the proposed converter makes it very suitable for renewable energy applications. In the proposed topology, a three-winding coupled-inductor and a voltage doubler rectifier are used to achieve high voltage gain without needing an extreme duty cycle. This circuit can provide an ultra-high voltage conversion ratio without requiring a large number of the turns ratio of the three-winding coupled-inductor (TWCI). Due to a regenerative clamped circuit, the leakage energy of the coupled-inductor is recycled; thus, the maximum voltage spike across the single-power switch is restricted. Therefore, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> with a low maximum voltage rating can be utilized, which can alleviate the conduction power dissipations of the converter. Here, the switching power losses have been reduced significantly due to the circuit's soft-switching operation for the switch and all diodes. The steady-state analysis of the proposed converter is discussed thoroughly. Finally, the theoretical analysis is verified through the experimental results from a sample prototype (400-W, 25-400 V).

Structure of Contact Layer of Steel (0.2% С) and Electrical Conductivity of Contact in Sliding on Steel Under Alternative Electric Current with Different Turn Ratios of Current Source

Structure of Contact Layer of Steel (0.2% С) and Electrical Conductivity of Contact in Sliding on Steel Under Alternative Electric Current with Different Turn Ratios of Current Source

Smooth DC-Link Y-Source Inverters: Suppression of Shoot-Through Current and Avoiding DC Magnetism

The Y-source impedance network is truly referred to as the origin of the magnetically coupled impedance source inverters. The key characteristics, including high boost capability and design flexibility, are associated with the coupled inductor turn ratio. However, the magnetic element brings some practical challenges, such as voltage spikes, high shoot-through (ST) current, and bulky coupled inductors. This article proposes two new Y-source inverters with clamped dc-link voltage. Due to the high boost ability, they are suitable for single-stage high gain inversions. Additionally, the significant reduction in the amplitude of the ST current leads to a reduction of the total power loss and capacity of the reactive component. Another attractive characteristic is that the Y-shaped coupled inductor's stored energy is no longer affected by the power rating of the converter, as a result of the zero dc magnetizing current. All these contribute to the high efficiency and power density of the proposed converters. The design guidelines of the components are presented and a thorough comparison with the state of the art is carried out. The achievements are then confirmed through extensive tests on a 500 W laboratory setup.

A High Step-Up Transformerless DC–DC Converter With New Voltage Multiplier Cell Topology and Coupled Inductor

In this article, a new high step-up transformerless dc–dc converter based on a voltage multiplier and a coupled inductor topology is presented. The proposed converter has two stages. In the first stage, a modified boost converter is designed by the coupled inductor, and in the second stage, a new voltage multiplier by using a coupled inductor is illustrated. In this converter, high voltage gain can be achieved by adjusting the turn ratio of two coupled inductors and the duty cycle, which result in three degrees of design freedom. Using a single power switch with low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistance in the converter structure leads to simple control and low conduction loss. In addition, total voltage stresses of active elements are decreased, which increases efficiency. Steady-state performance and theoretical achievements are confirmed by experimental test results on a test setup with one 200-W dc–dc prototype.

A high gain soft switched DC–DC converter for renewable applications

ABSTRACT This article presents a novel high gain soft-switching DC–DC converter with low component count and low voltage stress across switching devices. The proposed converter employs coupled inductor and voltage multiplier techniques to achieve high gain at low duty and low turn ratios. An active clamp circuit is also used to reduce voltage stress across the switch. As a result, lower voltage rating switches having lower on-state resistance (Rds-on ) are used, lowering system cost. It also helps to achieve zero voltage switching (ZVS) turn-on across both MOSFETs, reducing switching losses and improving efficiency. The leakage energy of the coupled inductor is recycled to improve the voltage gain, and the quasi resonance formed by the leakage inductance and switched capacitors helps to achieve zero current switching (ZCS) across diodes. This also helps in controlling the falling rate of output diode current, helping to mitigate the reverse recovery problem. The steady-state analysis has been carried out. A 500W prototype of the proposed converter is built up and tested to validate the working of the converter.

A 24-Pulse Rectifier With a Passive Auxiliary Current Injection Circuit at DC Side

In this article, a simple series-connected 24-pulse rectifier with a passive auxiliary current injection circuit (ACIC) is proposed. The proposed rectifier consists of a 12-pulse rectifier and an ACIC. The ACIC includes a circulation current forming circuit, an auxiliary single-phase transformer (AST), and an auxiliary single-phase full-bridge rectifier (ASFR). The ASFR extracts alternating square-wave current from the dc side and injects it into the outputs of three-phase rectifier bridges to increase the output state of these bridges. The operating mode of the proposed rectifier is analyzed, and the functional relationship between the input current and turns ratio of AST is established. The AST turns ratio that minimizes the input line current total harmonic distortion (THD) is derived. The voltage and current rating of AST are calculated, and the design method of capacitors C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in ACIC is given. Under the optimal turns ratio, the ACIC extends the 12- to a 24-pulse rectifier. The resulting 24-pulse rectifier draws near-sinusoidal input currents with less than 5% THD. The AST in ACIC has a very low kilovolt-ampere rating (1.96% <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ), and the current ratings of ASFR are small. The theoretical analyzes are provided and experimentally verified using a 1.7 kW experimental prototype.

Study of Solid-State Pulse Adder for Narrow Pulses Over Capacitive Load

High-voltage narrow pulses with short rise time and falling time are preferential in capacitive loads such as dielectric barrier discharges (DBDs). Therefore, a compact all-solid-state pulse adder based on solid-state linear transformer driver topology is proposed to generate high-voltage sub-microsecond resonant pulses with voltage amplitude up to 30 kV. A 20-stage prototype of the proposed pulse adder was built. The influence of the load capacitance, the turns ratio, and the number of stages on the waveforms and the voltage gain of output pulses are analyzed. To weaken the electromagnetic interference and lower the requirement of precise synchronous switching, a compromise is made between the pulsewidth and electromagnetic compatibility. High-voltage resonant pulses with a voltage amplitude up to 30 kV, a pulsewidth shorter than 200 ns, a rise time of 72 ns, and a frequency of 1 kHz were obtained over a 20-pF capacitive load.

Interruption Characteristics of Transformer-Type Superconducting DC Circuit Breaker According to Transformer Turn-Ratio

Series and parallel connection of each superconducting element is required to solve the capacitance problem of the superconducting element. However, unbalanced quench of the superconducting element may occur due to the difference in critical current of a single element. We intended to add a neutral line to the secondary of the transformer of the transformer-type superconducting DC circuit breaker among the interruption technologies proposed. This way has the advantage that the transformer-type superconducting element reduces the fault current through the quenching, and the DC circuit breaker interrupts the fault current by creating an artificial zero-point. In addition, the neutral line solves the unbalanced quench of the superconducting element. In this paper, we compared and analyzed the operating characteristics of the transformer-type superconducting DC circuit breaker by changing the turn-ratio of the transformer from 1:1. As a result, we confirmed that the efficiency of the transformer-type superconducting DC circuit breaker was the best when the turn-ratio of the transformer was 1.1:1.

High step-up DC-DC converter with switched capacitor-coupled inductor and voltage multiplier module

A high step-up dc-dc converter based on a switched capacitor-coupled inductor (SC-CL) with voltage multiplier cells is proposed. It is composed of a SC-CL and a voltage multiplier module stacked on the load side. SC-CL produces the maximum output voltage with maximum voltage gain. These features make the projected converter suitable for renewable energy applications such as solar photovoltaic (PV). A low turn ratio of the coupled inductor is used for realizing the higher gain. It consists of a voltage boost unit SC-CL and a voltage multiplier module. In a DC micro-grid, PV energy is one of the utmost significant sources of power. Since the PV source voltage is very low, a very high voltage gain converter is required for a DC microgrid. Here, a step-up DC-DC converter topology with a very high voltage gain characteristic is proposed. The projected converter was simulated by MATLAB/Simulink to convert 30 V to 380 V.

Control Strategy of AC-DC Converter Based on Dual Active Bridge With Minimum Current Stress and Soft Switching

This article presents a control strategy for the single-stage dual active bridge (DAB) ac-dc converters. To reduce the conduction loss and achieve zero voltage switching (ZVS), the global optimal working modes are reviewed. Based on the global optimal working modes, the input current of the DAB ac-dc converter is analyzed for the sinusoidal input voltage. The control algorithm of the DAB ac-dc converter is proposed to achieve the unit power factor with the minimum current stress and ZVS. The range of the working modes is analyzed to meet the wide load power. The working mode is varied with the line-frequency angle and load power, which guarantees that the DAB ac-dc converter works in the optimal working modes. The conduction loss in the converter with the variation of the series inductance and the turns ratio of the transformer is analyzed. The series inductance and the turns ratio of the transformer are designed to further improve the conduction loss. The proposed control strategy is applied to a 1 kW DAB ac-dc converter with 220 V/50 Hz input voltage and 200 V output voltage. The experimental results demonstrate the working mode, the soft switching performance, fast dynamic response, high efficiency, and high power quality.

Planar Piezoelectric Transformer-Based High Step-Down Voltage-Ratio DC–DC Converter

High step-down voltage-ratio converters are widely used in medium-/high-voltage systems, such as solar power equipment and electric charging station as auxiliary power supplies fed from the dc bus. Traditionally, magnetic transformer-based solutions with high turns ratio are implemented for voltage conversion and galvanic isolation. Instead of utilizing electromagnetic coupling, the high-voltage Rosen-type piezoelectric transformer (PT) provides an alternative solution with electro-mechanical coupling, whose equivalent circuit can be represented by a resonant circuit with an ideal transformer. Moreover, the high-voltage Rosen-type PT features natural mechanisms for high-voltage insulation, high-voltage conversion ratio, and a compact planar form factor, which are all beneficiary for a high step-down auxiliary power supply. This article renders a Rosen-type PT-based high step-down voltage-ratio converter with comprehensive analysis and detailed design procedure. To better understand the operating principle, electrical characteristics of the PT are first analyzed. Effects of input and output compensation components of the PT and their tolerance analysis are subsequently discussed to optimize the performance. After that, topologies of both the input inverter and the output regulation stages are selected. The proposed design is finally validated by a planar prototype with 10-mm height, 5 W full output power, 200 V to 1.5 kV input voltage, and 5 V regulated output voltage.

Design of High Step-Down Ratio Isolated Three-Level Half-Bridge DC–DC Converter With Balanced Voltage on Flying Capacitor

A high step-down ratio three-level half-bridge (TLHB) dc–dc converter with a current-doubler rectifier is presented for power conversion from a 48-to-60-V input to a 0.5-to-1-V output. The proposed TLHB topology and operation employed on the primary side improve the power-conversion efficiency by reducing the switching loss while minimizing the turn ratio of the transformer by converting the input voltage down to one quarter on the primary side. Moreover, it reduces the voltage stress on switches by half, thereby enabling the converter to be implemented with Si transistors with low breakdown voltage. The designed TLHB gate-driver IC minimizes the delay mismatches in gate drivers and mitigates the effect of the leakage inductance of the transformer, reducing the voltage imbalance on the flying capacitor without any balancing scheme in the controller. The proposed dc–dc converter implemented with 40-V Si transistors for the primary-side switches achieves 92.8% peak efficiency while supporting the maximum load current of 60 A and the maximum input voltage of 60 V. The converter with the proposed TLHB gate driver IC shows less than 0.8% voltage imbalance on the flying capacitor.

Identification of sensor location and link flow reconstruction using turn ratio and flow sensors in an arterial network

In this article, a quadratic programming problem is considered to identify all link flows in an arterial network when there are unmeasured link flows. A graphical method is provided to determine the minimum number of measurements and sensor locations required to obtain a fully observable model. It is shown that this method is also valid for the augmented graph with turn ratio measurements. If the minimum measurements required are met, a fully determined network can be obtained. If there is not enough measurement, a bound on the magnitude of the resulting inaccuracy in terms of vehicle kilometers traveled (VKT) can be calculated by the proposed linear programming method. The model is that of a queueing network; the parameters describe network geometry, saturation flow rates, turning ratios, timing plan and link flows. Three case studies are conducted to validate this approach. The first two cases are to calculate all missing flows by using a few numbers of measurements and minimum number of measurements required, respectively. Upper and lower bounds in terms of VKT are also calculated for these cases. Third case is to obtain a fully determined network with the minimum number of flow measurements when turn ratio sensors are included. Real measurements are collected from a network in Mugla including 55 links and 16 intersections. Vissim simulator is used to analyze the accuracy of the link flow calculations obtained from the proposed method. The results show that the proposed programming method can calculate the missing flows with a high accuracy and short computation time.

An Integrated Buck and Half-Bridge High Step-Down Converter

In this paper, an integrated buck and asymmetrical half-bridge (IBAHB) high step-down converter utilizing a single-stage driving design for highly efficient energy conversion is proposed. The proposed converter is able to instantly and synchronously transfer energy from input to output within one conversion period. The advantages of high step-down conversion, lower voltage stress and fewer semiconductor elements verify the feasibility of this proposed topology. The turns ratio of the transformer can be reduced to increase the coupling rate, which decreases the leakage inductance. The proposed integrated topology utilizes the single-stage energy transfer control algorithm to verify that the proposed experimental circuit has a full-load efficiency. This development will achieve the market’s demand for high-buck converters and other related products and the competitive advantage of growing with the trend.

Tapped-inductor bi-directional Cuk converter with high step-up/down conversion ratio and its optimum design

A bidirectional DC–DC converter is required for an energy storage system. High efficiency and a high step-up and step-down conversion ratio are the development trends. In this research, a series of bidirectional high-gain Cuk circuits was derived by combining tapped inductors and bidirectional Cuk. After analyzing and comparing the characteristics of each circuit, a bidirectional high-gain Cuk circuit with a tapped-inductor (reverse coupling) was proposed. The proposed converter has a simple structure and a high voltage gain in both the step-down (Buck) and step-up (Boost) operation modes. The voltage stress of S2 was low. The voltage stress of S1 was high, however, and this is a disadvantage of the proposed converter. The proposed circuit’s characteristics were thoroughly examined, including the voltage gain characteristics and the design of the main parameters. We established a power loss model of the new topology, and the tapped-inductor turn ratio was optimized for high efficiency. Finally, a 400 W experimental implementation of the converter was shown to achieve efficiencies of 93.5% and 92.4% in the step-up and step-down modes, respectively. These findings verified the validity of the proposed circuit’s theoretical analysis.

Analysis and implementation of an isolated high step‐down converter with interleaved output for low voltage applications

AbstractThis paper proposes a new isolated high step‐down dc‐dc converter with a more extensive output range and high efficiency. The interleaved output and ZVS‐ZCS switching for all semiconductors have made the converter appropriate for high output current applications. An auxiliary inductor is used to achieve the ZVS (zero‐voltage switching) and ZVZCS (zero‐voltage zero‐current switching) condition, which charges and discharges the parallel snubber capacitors of the power switches at different modes of operation. Therefore, the switching losses of semiconductor components are reduced significantly, which results in enhanced efficiency. Moreover, the connection of an auxiliary capacitor in series with the transformer has prevented the probability of DC‐current saturation. The proposed converter could be controlled with duty‐cycle or switching frequency variations. However, the output voltage control with the switching frequency variations gives an extended range of output voltage compared with the other presented converters. Moreover, a coupled inductor is used to relate the output gain with the turn ratios, which causes a more extensive range for output voltage gain. Finally, the theoretical analysis is given and is compared with a 140 W experimental prototype, which converts a higher input voltage 300v to 7.5 V of the output voltage.

Zero voltage switching high step‐up boost converter with coupled inductor for renewable energy applications

AbstractThis paper proposes a zero‐voltage switching high step‐up boost converter with coupled inductor for renewable energy applications. In this proposed circuit, main and auxiliary switches are turned ON at zero voltage switching to reduce switching losses. The voltage gain of the converter is increased by varying the turns ratio between primary and secondary of the coupled inductor (CI). The voltage spikes at the main switch are mitigated by using active clamping technique. The reverse recovery problem in diodes is alleviated due to leakage inductance of the CI. Zero current switching turn OFF in output diode is achieved, which can enhance the efficiency of the converter. A real‐time model for 100 W proposed converter circuit is developed to verify the theoretical analysis.

Scott-Tied Magnetically Linked Solar Multilevel Converter in Varying Environmental Conditions

Recently, multilevel converters (MLCs) have given promising solutions for medium-power and high-power renewable energy systems. However, voltage level enhancement leads to a higher device count, especially for three-phase configurations. A megawatt-scale three-phase 27-level converter with a Scott-connected arrangement is used for medium-voltage applications to address such issues. The Scott transformer uses 1:3:9 turn ratios between the windings to have 27-level output converter voltage with the advantage of two-phase to three-phase conversion. Moreover, the transformers enable the converter output voltage to medium-voltage levels (typically 11 to 33 kV). Traditional three-phase systems have cascaded power converter modules in each phase. However, this system provides an alternative solution for solar power injection into the grid with minimum cascaded voltage source converters forming a two-phase network. The quadrature displaced nearest level modulation strategy fundamentally switches phase A and B legs. Moreover, the solar photovoltaic (SPV) system is modeled at a megawatt-scale and tested in various environmental conditions. Thermal, cost, and leakage-inductance models are presented for the Scott-tied solar MLC. Obtained results demonstrate the satisfactory observation and control of the SPV system for renewable energy applications.

Design and implementations of high step‐up non‐isolated DC‐DC converters for electric vehicles application

AbstractAn effective hybrid energy system that connects with a fuel cell, solar, and battery system is described as a renewable energy (RE) source powered electric vehicle. The consequences of designing multi‐input DC‐DC converters for various sources are thoroughly studied. The fuel cell (FC) is utilized as the major source of energy, with photovoltaic (PV) livings utilized to recharge the battery, enhance efficiency, and diminish fuel consumption. By selecting a suitable coupled inductor turn ratio, the proposed structure efficiently enhances the rate of output voltage. A coupled inductor's created leakage inductance energy can be reclaimed, resulting in a reduction in the recommended converter's power losses. Variability in RE power production and load demand are both taken into account for maintaining the power balance. In addition, a power management technique is developed and implemented in a control technique. High gain, continuous input current, low voltage stress on switches, and extensive input and output operations are some of the interesting features of the proposed converter. The converter's results are also experimentally verified with the use of a programmable DC source.

Multilevel Converter With Nearest Level Control for Integrating Solar Photovoltaic System

This article presents a new Scott-ternary solar multilevel converter (ST-MLC)-based solar photovoltaic (PV) system for medium voltage applications. This system employs a single solar PV array as an input source and two voltage source converters (VSCs) to feed a three-phase grid. Solar power is fed from a two-phase to a three-phase medium voltage grid with balanced grid currents. The legs of VSCs are cascaded to form a two-phase system. The multiwinding transformers are connected in a Scott manner to develop a nine-level three-phase power conditioning system. The turn ratios of the transformers have ternary progression for the generation of higher levels. The modeling of the system is presented, and a closed-loop nearest level control strategy is incorporated to have minimum losses. Simulation results show the performance of the solar PV system under steady-state and dynamic irradiance. Varying solar profile is considered on basis of the daily average global solar irradiance from the geographical information system for New Delhi, India. The harmonic performance is analyzed for the converter voltage and grid current. Moreover, a detailed comparative analysis is covered for the ST-MLC to evaluate its superiority over its existing counterparts. Performance validation is done in a real-time test bench to validate the control and operation of the large-scale solar PV system.