Hamidreza Keyhani

Flying-capacitor boost converter

This paper introduces the flying-capacitor dc-dc boost converter. In the proposed topology, a high voltage gain ratio and improved conversion efficiency are achieved with low inductor core and copper losses. The input current ripple of the new converter is low while its ripple frequency is high, yielding a low-sized input filter. Furthermore, the voltage stresses on the power switches and diodes of the proposed converter are considerably low. It is shown that the proposed converter can be extended to higher stages to achieve a higher voltage gain ratio at enhanced efficiency. The principle of operation of the new converter is proposed, and the comparison with the conventional boost topology is presented. A complete analysis of this converter in the steady state and small signal operation is performed as well. Simulation results and a design example are also given to demonstrate the effectiveness of the proposed power converter.

Partial-Resonant Buck–Boost and Flyback DC–DC Converters

This paper introduces innovative nonisolated and isolated soft-switched dc-dc topologies with the step-up/down ability. The nonisolated topology is constructed by adding a small ac capacitor in parallel with the main inductor of the conventional buck-boost converter and replacing its semiconductor devices with the reverse-blocking switches. By using a novel control scheme, true zero-voltage switching is realized at both turn-on and turn-off of the power switches irrespective of the input voltage, output voltage, or load value. The isolated form of the converter is created by substituting the main inductor with an air-gapped high-frequency transformer, similar to the flyback converter. In this case, two smaller ac capacitors are placed on both sides of the transformer to realize soft switching as well as passive clamping; no extra clamping circuit is required. The basic operation of the proposed partial-resonant converters includes four modes and is described in detail. The comprehensive analysis of the topologies is carried out as well. Various experimental results in different operating conditions are provided to verify the performance of the proposed power converters.

A soft-switching three-phase ac-ac converter with a high-frequency ac link

A new three-phase ac-ac converter with a high-frequency ac link, soft switching characteristic, unity input power factor, step-up and step-down operation, and bidirectional power flow is introduced in this paper. The converters link is composed of an ac inductor and a very small ac capacitor; there is no short-life bulky electrolytic capacitor. Moreover, the converters switches are zero voltage at turn-on and low loss at turn-off; therefore, the switching losses are considerably low, which subsequently permits the switching frequency to be high. The total number of the switches in this novel topology is as low as twelve, suitable for low power applications. The basic operation of the new converter includes eight distinct modes, which are described in detail. The analysis and optimal design of the proposed topology are carried out as well. Simulation results are also given to demonstrate the effectiveness of the proposed power converter.

An Isolated Resonant AC-Link Three-Phase AC–AC Converter Using a Single HF Transformer

An isolated three-phase ac-ac converter with a high frequency (HF) ac link, soft switching operation, high input power factor, and bidirectional power flow is introduced. The galvanic isolation is attained by a single HF transformer, which is substantially smaller than the line-frequency transformers. Moreover, the magnetizing inductance of this transformer and two small ac capacitors form the convertors HF ac link; no bulky short-life electrolytic capacitor is used. The magnetizing inductance is the main component for transferring power, and the link capacitors provide partial resonance to achieve zero voltage switching for the power switches in all operating modes. The basic operation of the topology is composed of 16 modes and is described. The detailed analysis of the proposed topology is carried out to reveal further the converters behavior in different operating conditions. The simulation and experimental results are also provided to demonstrate the effectiveness of the proposed power converter.

Isolated soft-switching HFAC-link 3-phase ACAC converter using a single-phase HF transformer

A new resonant three-phase ac-ac converter with a high-frequency ac link, soft switching characteristic, unity input power factor, galvanic isolation, and bidirectional power flow is introduced in this paper. The galvanic isolation is realized with only one single-phase high-frequency transformer, which is substantially small. The converters ac link is formed by the magnetizing inductance of the high-frequency transformer and two considerably small ac capacitors; no bulky short-life electrolytic capacitor is used. Moreover, the converters switches are turned on at zero voltage and are turned off with low loss; therefore, the converters switching losses are significantly low, which subsequently permits the switching frequency to be high. The operation of the topology comprises 16 distinct modes and is described in detail. The analysis of the proposed topology is carried out to reveal the converters behavior in different operating conditions. Simulation results are also given to demonstrate the effectiveness of the power converter.

A ZVS single-inductor multi-input multi-output DC-DC converter with the step up/down capability

A multiple input-output dc-dc topology with soft switching operation and step up/down ability is introduced in this paper. The number of the converters inputs and outputs are completely arbitrary while they can be at different voltage and power levels. The proposed topology is composed of a small ac inductor-capacitor pair as the high-frequency link and only one reverse-blocking switch for each input or output of the converter. In order to transfer power, the link inductor charges through the inputs one-by-one and then discharges to the outputs in a proper sequence. The link capacitor creates partial resonances to achieve the zero-voltage switching at both turn-on and turn-off of all the power switches. A small-sized high-frequency transformer can be employed in the converters link for galvanic isolation. The principle of operation of the proposed topology is described, and a detailed analysis of the converter is carried out. Experimental results are provided to validate the performance of the proposed multi-input multi-output dc-dc converter.

Isolated ZVS High-Frequency-Link AC-AC Converter With a Reduced Switch Count

This paper introduces an isolated soft-switched three-phase ac-ac converter with a high-frequency link and reduced switch count for low- and medium-power applications. A small air-gapped high-frequency transformer acts as the key component by providing galvanic isolation as well as transferring power using its magnetizing inductance. Two small ac capacitors are placed on both sides of the transformer to realize zero-voltage switching for the semiconductor devices in addition to passive clamping. Therefore, the proposed topology is expected to be highly efficient and reliable due to soft-switching operation and exclusion of limited-lifetime electrolytic capacitors. Furthermore, the proposed converter has a high input power factor, step-up/down ability, and bidirectional power flow with arbitrary output voltage amplitude and frequency. The basic operation of the converter includes eight modes and is described in detail. Theoretical analysis and design are also given to illustrate its operation at various operating points. Simulation and experimental results are provided to verify the performance of the proposed power converter.

A soft-switched highly reliable grid-tied inverter for PV applications

This paper introduces a soft-switched high-frequency-link inverter for grid-tied PV systems. This single-stage inverter can perform the step-up/down operation and also has the ability to effectively harvest the highest possible power from the PV array. The high-frequency link is formed by an ac inductor and a small ac capacitor without the use of bulky short-life electrolytic capacitors. The link inductor is responsible for transferring the PV power to the grid while the link capacitor facilitates zero-voltage switching for the power devices. Galvanic isolation can be realized by replacing the link inductor with an air-gapped high-frequency transformer. This novel topology has seven total switches, making it suitable for low and medium power PV applications. Furthermore, the converter has a high power density and reliability due to the minimization of passive component sizes and the requisite number of power switches. The proposed PV inverters control scheme and operating algorithm are presented, followed by a detailed design analysis. Experimental results are also provided to demonstrate the effectiveness of the proposed topology under different operating conditions.

A Soft-Switched Three-Phase AC–AC Converter With a High-Frequency AC Link

This paper introduces a three-phase ac-ac resonant converter with a high-frequency ac link, soft-switching operation, almost unity input power factor, step-up/down capability, and bidirectional power flow. The converters link is composed of an ac inductor and a small ac capacitor. The link inductor transfers power by charging through the input and discharging to the output, and the link capacitor creates partial resonances to realize zero-voltage switching for all the switches of the converter. Therefore, the proposed topology is expected to have high reliability and long lifetime due to the soft-switching operation and exclusion of short-life electrolytic capacitors. The total number of switches in this novel topology is as low as 12, which is suitable for low- and medium-power applications. The basic operation of the converter includes eight modes, which are described in detail. The full analysis and optimal design of the proposed topology are provided as well. Results of several simulations and experiments at different operating conditions are also presented to show the validity of the proposed converter.