Buck Rectifier Research Articles

An All-SiC Three-Phase Buck Rectifier for High-Efficiency Data Center Power Supplies

The low power losses of silicon carbide (SiC) devices provide new opportunities to implement an ultra high-efficiency front-end rectifier for data center power supplies based on a 400- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> ${\rm V}_{\rm dc}$</tex></formula> power distribution architecture, which requires high conversion efficiency in each power conversion stage. This paper presents a 7.5-kW high-efficiency three-phase buck rectifier with 480- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{V}_{{\rm ac}, {\rm rms}}$</tex></formula> input line-to-line voltage and 400- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm V}_{\rm dc}$</tex></formula> output voltage using SiC MOSFETs and Schottky diodes. To estimate power devices' losses, which are the dominant portion of total loss, the method of device evaluation and loss calculation is proposed based on a current source topology. This method simulates the current commutation process and estimates devices' losses during switching transients considering devices with and without switching actions in buck rectifier operation. Moreover, the power losses of buck rectifiers based on different combinations of 1200-V power devices are compared. The investigation and comparison demonstrate the benefits of each combination, and the lowest total loss in the all-SiC rectifier is clearly shown. A 7.5-kW prototype of the all-SiC three-phase buck rectifier using liquid cooling is fabricated and tested, with filter design and switching frequency chosen based on loss minimization. A full-load efficiency value greater than 98.5% is achieved.

Front-End Buck Rectifier With Reduced Filter Size and Single-Loop Control

This paper presents a transformerless solution for front-end rectification, which is particularly suitable for traction applications, requiring high voltages to be stepped down to appropriate dc voltage. The proposed topology is based on pulsewidth-modulation buck rectifier (current source inverter topology) and is capable of rectification and stepping down of single-phase ac supply, in a single stage. A new control scheme is proposed to achieve constant dc output voltage and sinusoidal source current, irrespective of large ripples in the dc inductor current. The proposed scheme is configured in single-loop voltage control mode. The relevant small-signal model is derived from the large-signal model using multiorder decomposition. An elaborate procedure of dc filter design is discussed, for circuit operation with minimum energy storage. All analytical results are validated by numerical simulation for sinusoidal and distorted source voltage. Experimental verification is achieved through a 1.2-kW grid-connected laboratory prototype.

Three phase six-switch PWM buck rectifier with power factor improvement

Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, three phase six-switch PWM buck rectifier is presented which operates at nearly unity power factor and provides variable output voltage. Small size energy storing components are required depending upon switching frequency. MATLAB simulation is performed and modified Sinusoidal Pulse Width Modulation (SPWM) switching technique is used in 3kW prototype converter to demonstrate low input current THD, nearly unity displacement factor, well regulated output voltage and reduced switching losses compared to conventional SPWM.

Detailed Analysis of How Power Stage and Power Clip Products Achieve Optimized Power Density

The power stage and power clip packages are designed to increase the power density, in a synchronous rectifier (SR) buck application, while using a significantly smaller PCB land pattern area than a conventional discrete pair of MOSFETs. This paper presents a detailed analysis of how these new Fairchild dual-die designs achieve this performance.

Transient and steady-state analysis of three-phase PWM buck rectifier

This study presents a qualitative and quantitative analysis of the output current response of a three-phase buck rectifier. The DC-side of the three-phase pulse-width modulation (PWM) buck rectifier is loaded by a typical series equivalent circuit comprising a resistor, an inductor and a constant voltage. An analytical solution of transient and steady-state processes is obtained using the difference equation method in the continuous conduction mode. The proposed analytical solution exhibits two repetition intervals, which accurately predict the ripple components of the output current. Hence, the solution of the process envelopes is obtained. The derivation of the plant transfer function from the analytical solution of the output current is also presented. System simulations and experimental studies are carried out to validate the analytical approach with various output loads.

Application of Resonant Snubber Switch Cell to Single-Phase Buck Rectifier

Application of resonant snubber switch cell to a single-phase buck rectifier is studied. The resonant snubber switch cell consists of an only active power switching device and a LC resonant circuit. The active power switching device is then turned on and off under the soft switching conditions. The experimental results under the sinusoidal pulse-width modulation (PWM) confirm that the input current can nearly be wave-shaped sinusoidally with a near-unity power factor.

Single-Switch Snubber Energy Recovery Bridge Leg for Buck Rectifier Applications

Single-switch bridge leg with a snubber energy recovery feature is studied for buck rectifier applications. To recover the snubber energy, two snubber capacitors are arranged across an active power device. An example of a single-phase rectifier applying a proposed bridge leg is implemented to investigate the operation. The experimental results under the sinusoidal pulse-width modulation confirm that the rectifier can recover the snubber energy and the input current is almost wave-shaped sinusoidally with a near-unity power factor.

Single-Phase Half-Controlled Buck Rectifier Capable of Recovering Snubber Energy

Single-phase half-controlled buck rectifier using a simple snubber energy recovery bridge leg is studied. When the active power devices assembled into this bridge leg are simultaneously turned on, the snubber capacitor is discharged and its stored energy is transferred to the load circuit. The experimental results confirm that the input current can be waveshaped sinusoidally with the higher efficiency than that of the conventional one.

A Novel Power Electronics-Based Fuel Cell Emulator

This paper proposes a prototype of a new power electronics-based fuel cell emulator. It can effectively replace a real electrochemical fuel cell stack during the development stage of a fuel-cell based power generation. The power stage of this new fuel cell emulator consists of a current source converter (buck rectifier) and a dc-to-dc buck converter. The research mainly focuses on emulating the electrical behavior of two well-known fuel cell systems: Proton Exchange Membrane (PEM) and Solid Oxide fuel cells. A 1.5kW PEM fuel cell case is presented inthis paper. Analysis, modeling and control strategy are presented. A hybrid control technique and a new voltage-current curve tracking technique have been proposed. Both static and dynamic performances of the proposed fuel cell emulator are experimentally verified. The results show that the proposed system can effectively perform in all three operation regions,i.e. activation, ohmic and concentration. With the collaboration of the power electronics circuits and the DSP-based controller, the proposed fuel cell emulator provides both precisely emulated voltage-current characteristic and high-quality output voltage and current.

Design of low-power high-frequency digital controlled DC-DC switching power converter

This paper models a low-power high-frequency digitally controlled synchronous rectifier (SR) buck converter. The converter is a hybrid system with three operation modes. Digital PID controler is used. Key problems such as quantization resolution of digital pulse-width modulation (DPWM) and steady-state limit cycles of digital control switching model power supply (SMPS) are discussed, with corresponding solutions presented. Simulation of a digital control synchronous buck is performed with a fixed-point algorithm. The results show that the described approach enables high-speed dynamic performance.

Steady‐state characteristics on a single‐phase buck rectifier with improved input‐current waveform

AbstractA single‐phase buck rectifier applying pulse width modulation (PWM) creates a large amount of low‐order harmonics flow out in the input current. A high‐inductance inductor must be used to reduce the pulsations of the DC inductor current and to produce a sinusoidal input current. To address this, the authors propose a single‐phase buck rectifier with improved input current waveform by adding a switch for back flow of the DC inductor current to the conventional structural elements. In this paper, the main circuit configuration and operating theory of the proposed rectifier are explained, and its effectiveness is confirmed through experimental results and simulations. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(4): 56–65, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20330

Low-cost current-fed PMSM drive system with sinusoidal input currents

Standard low- and medium-power drives are based on the voltage-source converter topology. There has been less research work on dual topology drives, based on a current-fed inverter structure. Although energy storage is more efficient in capacitors than in inductors, due to some inherent advantages of current-source converter topology, and at the first place, the absence of a dc-link electrolytic capacitor, a current-source drive system made with a considerably reduced dc link inductor could be better low-cost solution with improved reliability, lifetime, and transient response than conventional drive. This paper is about a new current-fed drive topology with sinusoidal input currents, which is applied to a permanent-magnet synchronous machine in low-cost applications. A three-switch front-end pulsewidth modulator buck rectifier with an appropriate control technique, a simple thyristor inverter at the output, together with a small dc choke (which can be embedded in the machine), virtually offers an inductorless integrated drive system solution and could challenge standard industry solutions. System description, analysis, design guidelines, simulated results, and measured experimental results will be presented.

Three-Phase Buck Rectifier Using Snubber Energy Recovery Bridge Legs

Three-phase buck rectifier using snubber energy recovery bridge legs is studied. The snubber capacitors assembled into the bridge legs are mainly charged and discharged under the resonance and the energy stored in them is transferred to the load circuit. Also, the currents flowing through power semiconductor devices are always limited to the dc current. The experimental prototype employing insulated-gate bipolar transistors is implemented to investigate the operation under the pulse-width modulation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor.

Zero-Current-Switched Three-Phase SVM-Controlled Buck Rectifier

A zero-current-transition (ZCT) cell is analyzed and designed to be used with a three-phase pulsewidth-modulation buck rectifier. This rectifier was space-vector controlled and used unidirectional current switches. The proposed ZCT circuit is load independent and achieves a high noise and voltage stress reduction and provides ZCTs to almost all transitions of the rectifier's switches and to the additional auxiliary switches. Theoretical equations have been obtained for design purposes. The circuit is easy to design and the driving signals for the auxiliary switches are also easy to obtain, as demonstrated in this paper.

Dynamic and steady state analysis of a three phase buck rectifier

Current source rectifiers among other alternatives, offer several advantages over line commutated rectifiers. Advantages include displacement power factor control and reduced line current harmonic distortion. This paper analyzes the current source rectifier (CSR) in transient and steady state, the models are developed in a synchronous reference frame. The load behavior is characterized for two load conditions, resistive load or, in general, increasing current for increasing voltage, and constant output power, decreasing output current for increasing voltage. Constant power operation can occur for a converter system supplying a pulse width modulation (PWM) inverter with high dynamics. Several static converter characteristics such as power factor, real and reactive power are analyzed for both types of load. Transient characteristics are analyzed for both types of load by exact small-signal model with full set of equations.

Power factor preregulators based on combined buck-flyback topologies

The limitation imposed on the achievable power level by the IEC 1000-3-2 standard in buck-derived power factor preregulators, is overcome by using a combined buck-flyback power stage. Two different step-down converters are proposed in this paper, which incorporate an auxiliary flyback stage. The auxiliary stage uses the same switch of the main converter, plus an additional power switch commutated at the line frequency. As compared to a simple buck rectifier, with this solution the harmonic content of the absorbed line current, at a given power level, can be reduced, thanks to the resulting increased conduction angle of the input rectifier bridge. Experimental results based on a 1 kW prototype are reported to validate the theoretical analysis of the proposed topologies.

Single-phase buck rectifier employing voltage reversal circuit for sinusoidal input current waveshaping

To ensure the continuous inductor current of single-phase buck rectifier even with a small energy storage/transfer inductor, the voltage reversal circuit is connected with a conventional circuit in cascade. This contributes to the sinusoidal input current waveshaping with a near-unity power factor. The operation, modulated with sinusoidally time-integrated input current, is simulated by a rigorous state-space method and the results obtained by this are compared with those executed for a conventional topology. The arrangement tested, using three insulated-gate bipolar transistors and a microcomputer as a PI controller, is implemented to experimentally investigate the operation. The simulated and experimental results confirm the usefulness of the rectifier presented as a single-phase buck rectifier with a good quality input current.

Three-phase six-pulse buck rectifier with high quality input waveforms

The design and analysis of a three-phase, six-pulse buck rectifier is presented. The PWM modulation technique is analysed using the commuting function. Such analysis represents the main design tool for the commutation sequence, since it provides information about the harmonic behaviour of the rectifier signals with respect to the parameters involved in the modulation. The carrier signal is selected after a spectral analysis has been performed, to minimise the harmonic distortion content, thus obtaining high quality input currents. Likewise, as an additional and helpful tool for the designer, a digital circuit was developed to generate and store the commuting function, which is then applied to the rectifier. Some tests were carried out on a prototype. The results which focus on the power factor and the total harmonic distortion are presented.

A comparative study of single-switch three-phase high-power-factor rectifiers

Three three-phase single-switch high-power-factor rectifier implementations were evaluated on a comparative basis. Specifically, the discontinuous-conduction-mode (DCM) boost rectifier with a 5th-harmonic-trap filter, the DCM boost rectifier with a harmonic-injection circuit, and the multiresonant, zero-current-switching buck rectifier were compared with respect to their efficiencies, compliance with the IEC555-2 specifications, volumes, weights and costs. The comparisons were done for the three-phase line-to-line input voltage of 380 V/sub rms//spl plusmn/20% and for 0-6 kW output power range.

Single-Phase Buck Rectifier with Improved Input Current Waveform

Single-Phase Buck Rectifier with Improved Input Current Waveform