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In this paper, a three-phase AC-DC high step-up converter is developed for application to microscale wind-power generation systems. Such an AC-DC boost converter prossessess the property of the single-switch high step-up DC-DC structure. For power factor correction, the advanced half-stage converter is operated under the discontinuous conduction mode (DCM). Simulatanously, to achieve a high step-up voltage gain, the back half-stage functions in the continuous conduction mode (CCM). A high voltage gain can be obtained by use of an output-capacitor mass and a coupled inductor. Compared to the output voltage, the voltage stress is decreased on the switch. To lessen the conducting losses, a low rated voltage and small conductive resistance MOSFETs are adopted. In addition, the coupled inductor retrieves the leakage-inductor energy. The operation principle and steady-state behavior are analyzed, and a prototype hardware circuit is realized to verify the performance of the proposed converter.

A new DC-DC power converter is researched for renewable energy and battery hybrid power supplies systems in this paper. At the charging mode, a renewable energy source provides energy to charge a battery via the proposed converter. The operating principle of the proposed converter is the same as the conventional DC-DC buck converter. At the discharging mode, the battery releases its energy to the DC bus via the proposed converter. The proposed converter is a non-isolated high step-up DC-DC converter. The coupled-inductor technique is used to achieve a high step-up voltage gain by adjusting the turns ratio. Moreover, the leakage-inductor energies of the primary and secondary windings can be recycled. Thus, the conversion efficiency can be improved. Therefore, only one power converter is utilized at the charging or discharging modes. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.

This paper presents a new bidirectional dc-dc converter with a high conversion ratio for renewable energy systems. The coupled-inductor technique is used to achieve a high conversion ratio with very simple control circuits. In discharging mode, the converter acts as a two-stage boost converter, controlling one power switch to achieve high-voltage step-up conversion. In charging mode, the converter acts as two cascaded buck converters that control two power switches simultaneously to achieve high-voltage step-down conversion. The operating principles and analysis of the steady-state characteristics are discussed in great detail. Finally, a 24-V/200-V prototype circuit with output power of 200 W is implemented to verify the feasibility of the proposed converter. The maximum efficiency levels in discharging and charging modes are about 94.3% and 91.6%, respectively.

This study presents a single-phase power factor correction AC–DC converter that operates in discontinuous conduction mode. This converter uses the pulse-width modulation technique to achieve almost unity power factor and low total harmonic distortion of input current for universal input voltage (90 Vrms to 264 Vrms) applications. The converter has a simple structure and electrical isolation. The magnetizing-inductor energy of the transformer can be recycled to the output without an additional third winding. The steady-state analysis of voltage gain and boundary operating conditions are discussed in detail. Finally, experimental results are shown to verify the performance of the proposed converter.

In this paper, a high-conversion-ratio bidirectional dc-dc converter with coupled inductor is proposed. In the boost mode, two capacitors are parallel charged and series discharged by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stress on the main switch is reduced by a passive clamp circuit. Therefore, the low resistance RDS(ON) of the main switch can be adopted to reduce conduction loss. In the buck mode, two capacitors are series charged and parallel discharged by the coupled inductor. The bidirectional converter can have high step-down gain. Aside from that, all of the switches achieve zero voltage-switching turn-on, and the switching loss can be improved. Due to two active clamp circuits, the energy of the leakage inductor of the coupled inductor is recycled. The efficiency can be further improved. The operating principle and the steady-state analyses of the voltage gain are discussed. Finally, a 24-V-input-voltage, 400-V-output-voltage, and 200-W-output-power prototype circuit is implemented in the laboratory to verify the performance.

This paper investigates a new isolated single-phase AC-DC converter, which integrates a modified AC-DC buck-boost converter with a DC-DC forward converter. The front semi-stage is operated in discontinuous conduction mode (DCM) to achieve an almost unity power factor and a low total harmonic distortion of the input current. The rear semi-stage is used for step-down voltage conversion and electrical isolation. The front semi-stage uses a coupled inductor with the same winding-turn in the primary and secondary sides, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. The discharging time can be shortened. In other words, the duty ratio can be extended. This semi-stage can be operated in a larger duty-ratio range than the conventional AC-DC buck-boost converter for DCM operation. Therefore, the proposed converter is suitable for universal input voltage (90~264 Vrms) and a wide output-power range. Moreover, the voltage stress on the DC-link capacitor is low. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.

The grid-connected AC module is an alternative solution in photovoltaic (PV) generation systems. It combines a PV panel and a micro-inverter connected to grid. The use of a high step-up converter is essential for the grid-connected micro-inverter because the input voltage is about 15 V to 40 V for a single PV panel. The proposed converter employs a Zeta converter and a coupled inductor, without the extreme duty ratios and high turns ratios generally needed for the coupled inductor to achieve high step-up voltage conversion; the leakage-inductor energy of the coupled inductor is efficiently recycled to the load. These features improve the energy-conversion efficiency. The operating principles and steady-state analyses of continuous and boundary conduction modes, as well as the voltage and current stresses of the active components, are discussed in detail. A 25 V input voltage, 200 V output voltage, and 250 W output power prototype circuit of the proposed converter is implemented to verify the feasibility; the maximum efficiency is up to 97.3%, and full-load efficiency is 94.8%.

In this paper, a novel high step-up dc-dc converter for distributed generation systems is proposed. The concept is to utilize two capacitors and one coupled inductor. The two capacitors are charged in parallel during the switch-off period and are discharged in series during the switch-on period by the energy stored in the coupled inductor to achieve a high step-up voltage gain. In addition, the leakage-inductor energy of the coupled inductor is recycled with a passive clamp circuit. Thus, the voltage stress on the main switch is reduced. The switch with low resistance RDS(ON) can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the diodes is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory to verify the performance of the proposed converter.

A novel two-switch high-step-up isolated converter with voltage lift is proposed in this paper. The proposed isolated converter utilizes a transformer with low turn ratio to achieve high step-up gain. The secondary winding charges two boosting capacitors in parallel as switches during the switch-on period, and two boosting capacitors are discharged in series during the switch-off period. Thus, the converter has high voltage gain with appropriate duty ratio. In addition, by using two clamping diodes and a capacitor on the primary side, leakage energy is recycled, and the voltage spikes of the two active switches are clamped, thereby improving conversion efficiency. Finally, experimental results based on a prototype implemented in the laboratory with an input voltage of 24 V, an output voltage of 200 V, and an output power of 200 W verify the performance of the proposed isolated converter; full-load efficiency is nearly 93%.

The study presents a non-isolated bidirectional DC-DC converter, which has simple circuit structure. The control strategy is easily implemented. Also, the synchronous rectifier technique is used to reduce the losses. The voltage gain of the proposed converter is the half and the double of the conventional bidirectional DC-DC buck/boost converter in the step-down and step-up modes, respectively. Therefore the proposed converter can be operated in wide-voltage-conversion range than the conventional bidirectional converter. The voltage stresses on the switches of the proposed converter are a half of the high-voltage side. In addition, the operating principle and steady-state analyses are discussed. Finally, a prototype circuit is implemented to verify the performance of the proposed converter.

An ultra-large voltage conversion ratio converter is proposed by integrating a switched-capacitor circuit with a coupled inductor technology. The proposed converter can be seen as an equivalent parallel connection to the load of a basic boost converter and a number of forward converters, each one containing a switched-capacitor circuit. All the stages are activated by the boost switch. A single active switch is required, with no need of extreme duty-ratio values. The leakage energy of the coupled inductor is recycled to the load. The inrush current problem of switched capacitors is restrained by the leakage inductance of the coupled-inductor. The above features are the reason for the high efficiency performance. The operating principles and steady state analyses of continuous, discontinuous and boundary conduction modes are discussed in detail. To verify the performance of the proposed converter, a 200 W/20 V to 400 V prototype was implemented. The maximum measured efficiency is 96.4%. The full load efficiency is 95.1%.

A novel high step-up dc-dc converter with coupled-inductor and switched-capacitor techniques is proposed in this paper. The capacitors are charged in parallel and are discharged in series by the coupled inductor, stacking on the output capacitor. Thus, the proposed converter can achieve high step-up voltage gain with appropriate duty ratio. Besides, the voltage spike on the main switch can be clamped. Therefore, low on-state resistance RDS(ON) of the main switch can be adopted to reduce the conduction loss. The efficiency can be improved. The operating principle and steady-state analyses are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory. Experiment results confirm the analysis and advantages of the proposed converter.

A novel bidirectional dc-dc converter is presented in this paper. The circuit configuration of the proposed converter is very simple. The proposed converter employs a coupled inductor with same winding turns in the primary and secondary sides. In step-up mode, the primary and secondary windings of the coupled inductor are operated in parallel charge and series discharge to achieve high step-up voltage gain. In step-down mode, the primary and secondary windings of the coupled inductor are operated in series charge and parallel discharge to achieve high step-down voltage gain. Thus, the proposed converter has higher step-up and step-down voltage gains than the conventional bidirectional dc-dc boost/buck converter. Under same electric specifications for the proposed converter and the conventional bidirectional boost/buck converter, the average value of the switch current in the proposed converter is less than the conventional bidirectional boost/buck converter. The operating principle and steady-state analysis are discussed in detail. Finally, a 14/42-V prototype circuit is implemented to verify the performance for the automobile dual-battery system.

In this paper, a novel high step-up dc-dc converter is proposed for a sustainable energy system. The proposed converter uses coupled-inductor and switched-capacitor techniques. The capacitors are charged in parallel and discharged in series by the coupled inductor to achieve high step-up voltage gain with an appropriate duty ratio. Besides, the voltage stress on the main switch is reduced with a passive clamp circuit; low on-state resistance Rds(on) of the main switch can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the diode is alleviated by a coupled inductor. Thus, the efficiency can be further improved. The operating principle and steady-state analyses of voltage gain are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory to verify the performance of the proposed converter.

This paper proposes a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20-40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input.

A novel high step-up dc-dc converter for a distributed generation system is proposed in this paper. The concept is composed of two capacitors, two diodes, and one coupled inductor. Two capacitors are charged in parallel, and are discharged in series by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stresses on the main switch and output diode are reduced by a passive clamp circuit. Therefore, low resistance R for the main switch can be adopted to reduce conduction loss. In addition, the reverse-recovery problem of the diode is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are also discussed in detail. Finally, a 24-V input voltage, 400-V output voltage, and 400-W output power prototype circuit of the proposed converter are implemented in the laboratory to verify the performance.

A novel high step-up dc-dc converter for fuel cell energy conversion is presented in this paper. The proposed converter utilizes a multiwinding coupled inductor and a voltage doubler to achieve high step-up voltage gain. The voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled. Therefore, the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a 750-W laboratory prototype converter supplied by a proton exchange membrane fuel cell power source and an output voltage of 400 V is implemented. The experimental results verify the performances, including high voltage gain, high conversion efficiency, and the effective suppression of the voltage stress on power devices. The proposed high step-up converter can feasibly be used for low-input-voltage fuel cell power conversion applications.

Conventional dc-dc boost converters are unable to provide high step-up voltage gains due to the effect of power switches, rectifier diodes, and the equivalent series resistance of inductors and capacitors. This paper proposes transformerless dc-dc converters to achieve high step-up voltage gain without an extremely high duty ratio. In the proposed converters, two inductors with the same level of inductance are charged in parallel during the switch-on period and are discharged in series during the switch-off period. The structures of the proposed converters are very simple. Only one power stage is used. Moreover, the steady-state analyses of voltage gains and boundary operating conditions are discussed in detail. Finally, a prototype circuit is implemented in the laboratory to verify the performance.

This paper proposes a novel three-phase ac-dc buck-boost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis.

A novel high step-up DC-DC converter, which is composed of one boost converter, two capacitors, two diodes and one coupled inductor, is presented in this study. The concept is that the two capacitors are charged in parallel and are discharged in series via the coupled inductor to achieve high step-up voltage gain under appropriate duty ratio. Also, the leakage-inductor energy of the coupled inductor is recycled and the voltage stress on the main switch can be reduced. Besides, the energy of leakage inductor can transfer to capacitor to increase voltage gain. Therefore low conduction resistance R DS(ON) of the main switch can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the output diode is alleviated. Thus, the efficiency can be further improved. The operating principle and steady-state analysis are discussed in detail. Finally, a prototype circuit with input voltage 24 V, output voltage 400 V and output power 200 W is implemented in the laboratory to verify the performance of the proposed converter.

This study presents a non-inverting buck–boost converter with an interleaved technique for fuel-cell systems. The converter transforms the fuel-cell energy into an electric current for efficiently running electric mobility systems. Two non-inverting buck–boost converters are integrated with an interleaved operation. Thus, a switch and a diode can be omitted, reducing cost. The interleaved operation reduces both the current ripple at the output and the current stress of the diodes. The operating principles and steady-state analysis are discussed in detail. An 800 W prototype circuit of the proposed converter that converts an input source (fuel-cell battery 24–45 V) into an output voltage (28 V) is built to verify performance. The synchronous rectifier technique is adopted to increase efficiency. Power loss and efficiency are also discussed.

A DC-DC converter with high step-up voltage gain is presented. The proposed converter uses the coupled inductor and the voltage-lift technique to achieve high step-up voltage gain. Additionally, the voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled in the proposed converter. Therefore the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a laboratory prototype circuit with input voltage 12-V, output voltage 100-V and output power 35-W is implemented to demonstrate the performance of the proposed converter.

A novel, single-stage, three-phase AC/DC step-down converter with electrical isolation has been presented. The front semi-stage, which is a three-phase AC/DC buck-boost converter, is operated in discontinuous conduction mode (DCM) to achieve unity power factor, pure sinusoidal input current and low total harmonic distortion of input current. The rear semi-stage, which is a DC/DC forward converter, is operated in continuous conduction mode at heavy load and is operated in DCM at light load for step-down voltage conversion. Also, the proposed converter has low voltage stress across the DC-link capacitor. In addition, the sixth times line frequency ripple component of DC-link voltage can be eliminated. Thus, smaller DC-link capacitor is required. Furthermore, the steady-state analysis of voltage gain and boundary-operating condition are discussed. The selections of inductors and capacitors are presented. Finally, simulated and experimental results are supplied to verify the theoretical analysis.

This work presents a single-phase AC/DC step-down converter, which is composed of two power stages, buck-boost converter and buck converter. The front stage is used for a power-factor-correction (PFC) circuit and is operated in discontinuous conduction mode (DCM) by using the pulse-width modulation (PWM) technique to achieve almost unity power factor and low total harmonic distortion of input current (THD i ). The rear stage is also operated in DCM to achieve voltage step-down and low DC-link voltage. The proposed converter can be applied for universal input voltage (85-265 V) and wide output power range. Also, the steady-state analysis of voltage gain and boundary operating condition are presented. Moreover, the selections of inductors, capacitors and input filter are depicted. Finally, a hardware circuit with simple control logic is implemented to illustrate the theoretical analysis.