Current-fed Push-pull Converter Research Articles

High-Voltage Autonomous Current-Fed Push–Pull Converter With Wireless Communication Applied to X-Ray Generation

High-Voltage Autonomous Current-Fed Push–Pull Converter With Wireless Communication Applied to X-Ray Generation

High voltage power supply controller for Electrostatic precipitators

Gaseous exhausts from various industries pollute the environment with fly-ash generally filtered by electrostatic precipitators (ESPs) before being released to the atmosphere. This paper presents the development of a controller for ESP power supply. The controller maintains the voltage applied to ESP at its maximum average value by duty cycle control that results in an improvement in dust collection-efficiency. The limiting factor for the output voltage is the breakdown of gas (spark/arc) in the electrode gap of ESP. During a spark/arc condition, the duty cycle limit imposed by the controller causes a reduction in output voltage that leads to the prevention of spark/arc. The present design has a response faster than line frequency power supply controllers. The control circuit is simpler, easy to implement and uses a standard PWM controller IC. The design of power stage uses a flyback current-fed push-pull DC-DC converter with multiple secondary circuits, which has the advantages of instantaneous current limit and less voltage stress on rectifier-diodes. Simulation is performed to obtain a 1 kV, 100 W output from a 24VDC source. The results are compared with experimental values to validate the controller’s ability to achieve good load regulation during normal operation and a reduction in output voltage during spark/arc condition.

Analysis and Design of Series LC Partial-Resonance-Pulse-Based ZCS Current-Fed Push-Pull Converter

This article analyzes a partial-resonance-pulse, created through a series LC resonant circuit, on the current-fed push-pull converter topology to achieve the zero-current-switching (ZCS) of the semiconductor switches. During switching overlap of the semiconductor switches, referred to as energy storage mode, the resonance occurs and offers the natural commutation of the semiconductor devices. During this period, the current is smoothly transferred from one switch to the other and the outgoing switch commutates naturally with ZCS. It solves the historical problem of the voltage spike across the devices at their turn-off and thus, eliminates the requirements of the snubber across switches or the clamping circuit. This reduces the hardware complexity and makes the converter snubberless, compact, and cost-effective. The variable frequency with constant switching overlap time is adopted for the load voltage regulation and to maintain the ZCS of the devices for a given range of source voltage and load current. A comprehensive study of the steady-state operation and analysis of the proposed topology is reported along with the design and selection of the resonant tank elements. A hardware proof-of-concept prototype rated at 500 W is developed and tested to validate the analysis and claims and demonstrate the converter performance. An efficiency of 96.2% is recorded in a laboratory on the prototype at full load.

Bidirectional Soft Switching Push–Pull Resonant Converter Over Wide Range of Battery Voltages

This article presents a bidirectional soft-switching push-pull resonant converter that is highly efficient over a wide range of battery voltages. It is derived by integrating a current-fed push-pull circuit and an active voltage doubler circuit with a bidirectional switch. The converter operates as a pulsewidth modulation (PWM) current-fed push-pull resonant-boost converter in the forward direction, but as a PWM half-bridge resonant converter in the backward direction. The most attractive feature of the proposed converter is that, by employing the bidirectional switch and corresponding switching modulation, it can achieve almost ZVS at turn-off instants under wide variations of battery voltages. Therefore, the proposed converter achieves high efficiency even during high-frequency operation. Moreover, no instantaneous reactive current flows through the circuit under wide variations of battery voltages and loads. Furthermore, the proposed bidirectional resonant converter has a high conversion ratio in both power flow directions without using a transformer that has high turns-ratio. The operating principles and characteristics of the proposed bidirectional resonant converter are presented in detail. Experimental results using a 1-kW prototype verified the feasibility and efficiency of the proposed converter.

Resonant Push–Pull Converter With Flyback Regulator for MHz High Step-Up Power Conversion

With the trend toward achieving high efficiency, high power density and high operating frequency in power converters, a galvanic isolated circuit architecture is proposed in this article for high step-up applications with wide input-voltage range. This converter consists of a current-fed resonant push-pull (PP) converter as a dc transformer (dcX) dealing with most of the power with high efficiency and an active clamp flyback converter (ACF) as a regulator within a large conversion range. As a single-stage converter, the ACF regulator is paralleled with PP converter to share the total power and regulates the high output voltage. An experimental prototype with an input-voltage range of 24-32 V and output 400 V/400 W is built under 1 MHz switching frequency. A peak efficiency of 97.1% and a power density of 210 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (or 13 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) are achieved. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter for MHz high step-up dc-dc conversion.

Small Signal Analysis and Control of Snubberless Naturally-Clamped Soft-Switching Current-Fed Push-Pull DC/DC Converter

This article presents detailed small-signal modeling and closed-loop control design for transient performance evaluation of a high-frequency snubberless isolated current-fed push-pull dc-dc converter. The topology attains the natural commutation of semiconductor devices through zero current switching. The state-space averaging technique is employed to derive the transfer functions. A two-loop average current controller is designed and implemented on a digital signal processor to evaluate and demonstrate the transient performance of the converters. A complete procedure for a closed-loop control design is illustrated. Simulation results using PSIM 11.1.64 with the designed controller are shown to validate the stability of the system. Experimental results demonstrated satisfactory transient performance at various load conditions of the converter and validated the derived model and the control design.

ZVS three‐phase current‐fed push–pull converter employing a simple active‐clamp circuit for voltage step‐up applications

In this study, a new zero-voltage-switching (ZVS) three-phase current-fed push-pull converter is proposed for voltage step-up applications such as interfacing between the low-voltage high-current input sources such as photovoltaic, fuel cells and high-voltage dc bus. The proposed converter realises ZVS for all of the primary switches and zero-current-switching for secondary diodes that improves the conversion efficiency. In comparison with the existing three-phase current-fed push-pull converters with a voltage-clamped, one simpler active-clamp circuit is employed to reuse the leakage inductance for soft-commutation and suppress the transient surge voltage enabling the use of low voltage-rated switches with low on-state resistance. The theoretical analysis, design guidelines, comparative study, experimental results and loss breakdown for this topology are presented in the text. Finally, a 1.2 kW prototype has been implemented and tested in the laboratory to verify the effectiveness of the proposed concept.

Active‐clamped ZVS current‐fed push–pull isolated dc/dc converter for renewable energy conversion applications

This study introduces a new active-clamped current-fed push-pull dc-dc converter for renewable energy conversion applications. The proposed converter conserves small input current pulsation, high-voltage conversion ratio, zero-voltage switching (ZVS) and zero-current-switching operation for primary switches and rectifier diodes, respectively, over a large load range. Also, the additional active clamping circuit serves to suppress the voltage spike across all primary switches, as well as assists in achieving ZVS operation. So, the low-voltage switches with low on-state resistance can be adopted. These features can reduce switching loss, voltage stress, transformer turns ratio and diode reverse-recovery effect. More importantly, similar characteristics can be obtained with minimised switches compared with the reported converters that enable to reduce the cost and improve the reliability. Detailed steady-state operation, analysis, performance comparison, experimental results and loss breakdown of the proposed converter are fully discussed in this study. Finally, a 520 W prototype verifies the theoretical analysis.

Modeling and Controller Design of PV Micro Inverter without Using Electrolytic Capacitors and Input Current Sensors

This paper outlines the modeling and controller design of a novel two-stage photovoltaic (PV) micro inverter (MI) that eliminates the need for an electrolytic capacitor (E-cap) and input current sensor. The proposed MI uses an active-clamped current-fed push-pull DC-DC converter, cascaded with a full-bridge inverter. Three strategies are proposed to cope with the inherent limitations of a two-stage PV MI: (i) high-speed DC bus voltage regulation using an integrator to deal with the 2nd harmonic voltage ripples found in single-phase systems; (ii) inclusion of a small film capacitor in the DC bus to achieve ripple-free PV voltage; (iii) improved incremental conductance (INC) maximum power point tracking (MPPT) without the need for current sensing by the PV module. Simulation and experimental results demonstrate the efficacy of the proposed system.

A Switching Control Strategy for Single- and Dual-Inductor Current-Fed Push–Pull Converters

A switching control strategy is proposed for single- and dual-inductor current-fed push-pull converters. The proposed switching control strategy can be used with both current-fed push-pull converters with an active voltage doubler rectifier, or active rectifier, in the secondary-side of the isolation transformer. The proposed switching control strategy makes turn-on and turn-off processes of the primary-side power switches zero-voltage switching and zero-current switching, respectively. The soft-switching operation of the single- and dual-inductor push-pull converters, with both types of active rectifier, is explained. Simulation and experimental results are provided to validate soft-switching operation of the current-fed push-pull converters with the proposed switching control strategy.

Autonomous Polyphase Current-Fed Push–Pull Resonant Converter Based on Ring Coupled Oscillators

This paper presents an autonomous polyphase current-fed push-pull resonant converter without the need of monitoring and controlling its phase delays. Although the method is valid for multiple phases, a three-phase system is studied to show that accurate 120° phase shift can be realized by coupling three identical magnetic coils of a resonant converter with zero voltage switching (ZVS). Unlike the conventional converters, the proposed converter achieves a full-autonomous operation with automatic startup, full resonance at ZVS, and accurate dynamic balancing between the phases without any additional detection and control. A prototype of a three-phase system operating at 73.5 KHz has been built, and both simulation and practical results have demonstrated that the proposed converter can generate good quality sinusoidal waveforms with ZVS operation and precise phase delays. The proposed converter can be used for polyphase inductive power transfer systems where a generation of a rotating/travelling magnetic field is required.

A Switched-Reluctance Generator With Interleaved Interface DC–DC Converter

This paper presents the development of a wind switched-reluctance generator (SRG) with interleaved interface dc-dc converter. First, the power circuit and control scheme of the SRG are properly designed. The hysteresis current-controlled pulse width modulation (PWM) scheme is designed to achieve good winding current tracking control, and the robust voltage control scheme is developed to yield well-regulated dc output voltage under varying prime mover driving speed and load conditions. Moreover, the voltage regulation and the developed power performances of SRG are further enhanced using the proposed commutation shift approach. Next, an interleaved current-fed push-pull interface dc-dc converter with two modules is developed to establish the boosted common dc bus voltage of a dc microgrid from the SRG output having fault-tolerant capability. The rating analysis and circuit component design are conducted in detail. Similarly, well-regulated voltage with lower ripples is also yielded via the properly designed schematic and control scheme.

Naturally Clamped Snubberless Soft-Switching Bidirectional Current-Fed Three-Phase Push-Pull DC/DC Converter for DC Micro-Grid Application

A current-fed three-phase push-pull bidirectional dc-dc converter is proposed with unique features of natural zero current commutation and natural device voltage clamping. The proposed topology is suitable for uninterruptible power supply, storage, renewable energy sources, and interfacing two dc buses of 48- and 380-V dc buses in a dc microgrid. The proposed converter implements a novel and innovative modulation that results in natural commutation with zero current switching (ZCS) and device voltage clamping of low voltage side (LVS) current-fed devices, and zero voltage switching (ZVS) turn-on of high voltage side (HVS) voltage-fed devices. It eliminates the use of passive/active clamp circuits to mitigate the turnoff voltage spike across the devices, a traditional problem associated with current-fed topologies. Additionally, the higher ripple frequency reduces the volume of the transformer and the input inductor, making it suitable for high-power applications. The detailed modulation scheme, steady-state operation, and analysis, design, and soft-switching conditions have been explained. Simulation results obtained using PSIM 9.3 have been illustrated to verify the modulation, analysis, and proposed design. Experimental results have been demonstrated for full load (1 kW), half-load (500 W), and 20% load conditions on a proof-of-concept hardware prototype to validate the claims and performance. The efficiency is plotted against various load conditions for a wide range of battery voltage variation (40-59 V). Peak efficiencies of 95.8% and 93.8% are obtained at half-load condition for an input voltage of 59 V and nominal voltage (48 V), respectively. The experimental results for battery charging (reverse direction) using dual phase-shift plus pulsewidth modulation are given. The ZVS of HVS switches and the synchronous rectification of LVS active switches are shown through experimental results.

Impulse Commutated Zero-Current Switching Current-Fed Push–Pull Converter: Analysis, Design, and Experimental Results

Impulse commutated current-fed push-pull (ICCPP) converter has been analyzed and designed. The topology maintains zero-current switching (ZCS) of the semiconductor devices. Variable frequency modulation has been adopted to regulate load voltage and achieve ZCS over variable input voltage. At fixed input voltage, ZCS and load voltage are load independent. Natural clamping of devices is achieved via impulse commutation. Push-pull converters have only two devices with common ground with source requiring simple gate drive circuitry. A comprehensive study of the proposed converter, including steady-state analysis and design, has been reported. A 500-W prototype was developed in the laboratory to evaluate and demonstrate the performance of the converter.

Current-Fed Flyback Push-Pull DC-DC Converter Based on Three-Phase Transformer

Three-phase current-fed flyback push-pull dc-dc converter is proposed in this paper, which is a new circuit topology putting into practice based on current-fed flyback push-pull dc-dc converter. Structure is simplified; cost is cut down; efficiency and reliability are improved all by the high frequency three-phase transformer technique that carries out functions of flyback transformer as well as push-pull transformer at the same time. Three-phase transformer can be separated into relatively independent functions of flyback transformer and push-pull transformer with the reluctance produced by the magnetic gap in the central phase; the flyback transformer produces only common-mode flux in the magnetic circuit of push-pull transformer and does not influence its output signal; the magnetic flux in push-pull transformer is blocked by the magnetic gap and can only flow through the outer magnetic loop. Investigational device is designed; static and dynamic characteristics are observed and test results are verified by the experimentation.

SOLAR POWERED THREE PHASE MOTOR FOR VARIOUS APPLICATIONS

The Power electronics plays a vital role in the conversion and control of the electrical power for various applications such as heating &amp; lightning control, electrochemical processes, DC &amp; AC electrical machine drives, electrical welding, active power line filtering, static var compensator and many more.The main aim of the paper is to analyze and design of a current fed push pull DC-DC boost converter to integrate three phase electric motor through inverter. The regulated output which is obtained by the developed converter is fed to a typical load side inverter, and then to the various loads. To analyze the CFPP DC-DC converter in different operating cycles. The hardware circuit will be designed to test for the required output.Among the existing DC/DC converters, current-fed push-pull (CFPP) converter is a better option owing to its voltage boosting, isolation and compact characteristics.

A ZVS-PWM Three-Phase Current-Fed Push–Pull DC–DC Converter

In this paper, a ZVS-PWM three-phase current-fed push-pull dc-dc converter is proposed. When compared to single-phase topologies, the three-phase dc-dc conversion increases the power density, uses the magnetic core of the transformer more efficiently, reduces the stress on switches, and requires smaller filters since the frequency for its design is higher. The proposed converter employs an active clamping technique by connecting the primary side of the transformer to a three-phase full bridge of switches and a clamping capacitor. This circuit allows the energy from the leakage inductances to be reused, increasing the efficiency of the converter. If appropriate parameters are chosen, soft-commutation of the switches (ZVS) can also be achieved. The soft-commutation improves the efficiency even further, allows higher switching frequencies to be used, and reduces the electromagnetic interference significantly. Applications such as fuel cell systems, transportation, and uninterruptable power supplies are some examples that can benefit from the advantages presented by this converter. The theoretical analysis, a design example, and the experimental results for a prototype implementing this topology are presented. The prototype was designed to process 4 kW at full load with an input voltage of 120 V, an output voltage of 400 V, and a switching frequency of 40 kHz.

Power Flow Control Based Solely on Slow Feedback Loop for Heart Pump Applications

This paper proposes a new control method for regulating power flow via transcutaneous energy transfer (TET) for implantable heart pumps. Previous work on power flow controller requires a fast feedback loop that needs additional switching devices and resonant capacitors to be added to the primary converter. The proposed power flow controller eliminates these additional components, and it relies solely on a slow feedback loop to directly drive the primary converter to meet the heart pump power demand and ensure zero voltage switching. A controlled change in switching frequency varies the resonant tank shorting period of a current-fed push-pull resonant converter, thus changing the magnitude of the primary resonant voltage, as well as the tuning between primary and secondary resonant tanks. The proposed controller has been implemented successfully using an analogue circuit and has reached an end-to-end power efficiency of 79.6% at 10 W with a switching frequency regulation range of 149.3 kHz to 182.2 kHz.

Establishment of a Switched-Reluctance Generator-Based Common DC Microgrid System

This paper presents a dc microgrid including a switched-reluctance generator (SRG) with isolated boost dc-dc converter, a battery energy storage system, and a single-phase three-wire (1P3W) load inverter for generating ac 220/110 V 60-Hz outputs. The 400-V dc grid is established by the SRG with dc 48-V output followed by a current-fed push-pull (CFPP) dc-dc converter. The robust commutation and dynamic control schemes are developed for the SRG to have excellent output performances. For providing the domestic load power sources, a 1P3W transformerless 220/110 V inverter is established. A master and slave robust control schemes are proposed to yield balanced sinusoidal output voltage waveforms in both voltage outputs under varying load conditions. To improve the dc grid power supporting reliability, a battery energy storage system with bidirectional buck-boost interfacing converter is established. It can support the common dc bus voltage immediately when the main power source fault occurs. Conversely, the battery bank can be charged from the common dc bus through the same converter. Particularly, an auxiliary charger formed by a flyback switch-mode rectifier is equipped to allow the battery to be charged from the plug-in utility power as the long duration of microgrid fault occurs. Normal operation and good operating performance of the established microgrid are verified experimentally.

A Three-Phase Current-Fed Push–Pull DC–DC Converter With Active Clamp for Fuel Cell Applications

In this paper, a new active-clamped three-phase current-fed push-pull dc-dc converter is proposed for high-power applications where low-voltage high-current input sources such as fuel cells are used. The proposed converter has the following features: active clamping of the transient surge voltage caused by transformer leakage inductances, natural zero-voltage switching turn-on of main switches using energy stored in transformer leakage inductor, small current rating and zero-voltage and zero-current switching of clamp switches, no additional start-up circuitry for soft starting due to the operating duty cycle range between 0 and 1, and zero-current switching turn-off of rectifier diodes leading to negligible voltage surge associated with the diode reverse recovery. A comparative study along with loss analysis is performed. Experimental results from 5-kW laboratory prototypes of the proposed active-clamped converter and the passive-clamped converter are provided.