Showing papers on "Rectifier published in 2022"
TL;DR: In this paper, a miniaturized split-phase half-turn transformer is demonstrated, which leverages the well-established parallelization benefit of employing multiple phases, as in a matrix transformer, with the dramatic reduction in copper loss associated with the relatively new Variable Inverter/Rectifier Transformer (VIRT) architecture.
Abstract: High step-down, high output current converters are required in many common and emerging applications, including data center server power supplies, point-of-load converters, and electric vehicle charging. Miniaturization is desirable but challenging owing to the high step-down transformer ubiquitously used in these converters. In this work, a miniaturized split-phase half-turn transformer is demonstrated, which leverages the well-established parallelization benefit of employing multiple phases, as in a matrix transformer, with the dramatic reduction in copper loss associated with the relatively new Variable Inverter/Rectifier Transformer (VIRT) architecture. While these techniques have been described in earlier studies, their combination has not been well explored. A detailed design procedure is described and is used to develop a 97.7% peak efficiency and 97.1% full-load efficiency prototype having a transformer that is 12%–36% smaller than best-in-class designs in the literature at the same power level while also being more efficient. This work showcases the miniaturization benefit of employing multiphase, fractional-turn transformers in high step-down, high output current applications and provides comprehensive guidance to designers interested in applying and extending these techniques.
31 citations
TL;DR: In this article, a parallel configured 48-pulse rectifier, which is formed by two 24 pulse rectifiers connected in parallel through a tapped and coupled interphase reactors respectively, is proposed.
Abstract: To satisfy the ever-growing stringent requirement on the power quality of on-board electric power system, a novel parallel configured 48-pulse rectifier, which is formed by two 24-pulse rectifiers connected in parallel through a tapped and coupled interphase reactors respectively, is proposed. Through the comprehensive harmonic analysis on the proposed rectifier, it is revealed that the 23rd and 25th harmonics generated by the two 24-pulse rectifiers are equal in magnitude while opposite in direction, which evidently enables the 48-pulse operation. To better understand the performances of the proposed rectifier, its input current, output voltage, kVA rating, and power losses of magnetic devices are analyzed in detail. Afterward, the validity of the theoretical analysis is verified by simulation and experiment. The results confirm that the proposed 48-pulse rectifier has superior harmonic reduction ability, high reliability, and high power density. More importantly, due to the parallel structure, it also features high fault-tolerant ability, which makes it very suitable for aviation or aerospace applications.
20 citations
TL;DR: Theoretical analyses show that the proposed scheme can mitigate the dc-link current ripple over the full index range for a CSC and its carrier-based modulation, which can automatically select the desired vectors and last predetermined dwell times, is presented.
Abstract: This article presents a direct carrier-based modulation scheme to mitigate the dc-link current ripple for a current source converter (CSC) Excessive dc-link current ripple increases system losses, causes current distortion, and leads to more electromagnetic interference, so, it should be mitigated Compared with increasing dc-link inductor or switching frequency, it is more attractive to mitigate dc-link current ripple with modulation schemes However, existing modulation schemes suffer from either high dc-link current ripple or shrink of modulation index range To address this issue, this article analyzes the mechanism of mitigating the dc-link current ripple and proposes a new modulation scheme for a CSC By employing two kinds of non-nearest three vectors to synthesize the reference current, the proposed scheme successfully extends the index range from [ $\sqrt 3 /3$ , 1] to [0, 1] For easier implementation, its carrier-based modulation, which can automatically select the desired vectors and last predetermined dwell times, is also presented Theoretical analyses show that the proposed scheme can mitigate the dc-link current ripple over the full index range for a CSC The effectiveness of the proposed modulation scheme is verified experimentally with a CSC operating as a rectifier
20 citations
TL;DR: This work aims to maximize the system efficiency of a single-stage inductive power transfer (IPT) charger by minimizing the overall losses using a CP charging scheme and proposes a novel optimal control strategy to maintain CP output and maximum efficiency throughout the charging process.
Abstract: A typical battery charging process consists of a constant-current (CC) charging phase which is followed and completed by a constant-voltage charging phase. Moreover, replacing the CC charging by constant-power (CP) charging can eliminate thermal problems and enhance the cycle life of the battery. This work aims to maximize the system efficiency of a single-stage inductive power transfer (IPT) charger by minimizing the overall losses using a CP charging scheme. The single-stage CP IPT charger employs series-series compensation and adopts an active rectifier on the secondary side. Based on a time-domain model, the conditions of zero voltage switching (ZVS) and minimum circulating reactive power are derived. Then, the power losses in the magnetic coupler, inverter and active rectifier are analyzed and optimized under CP output condition. Combining the conditions of ZVS, minimum circulating reactive power, and minimum overall losses, we propose a novel optimal control strategy to maintain CP output and maximum efficiency throughout the charging process. In addition, the proportional integral controller is not needed. Finally, a 120-W experimental prototype is built to verify the performance of the proposed control strategy. Experimental results demonstrate high precision CP output and an efficiency of around 87.5 $\%$ for the proposed single-stage inductive power transfer battery charger.
18 citations
TL;DR: In this paper, a cascade model-predictive control for a three-phase unity power factor rectifier is presented, where the output power is used as a feedforward to enhance the transient dynamics of the output dc voltage.
Abstract: In this article, a novel cascade model-predictive control for a three-phase unity power factor rectifier is presented. Unlike the traditional control techniques for rectifiers, the proposed method uses a cascade dual-model-predictive control for the inner and outer control loops. The three-phase currents of the rectifier are controlled with the inner control loop, while the desired output voltage is achieved with the outer control loop. In this proposal, the output power is used as a feedforward to enhance the transient dynamics of the output dc voltage. Several advantages can be highlighted such as a fixed switching frequency, and output voltage variations are avoided when a sudden change in the load or a voltage sag appears. The overall control proposal has been fully integrated into a digital signal processor. Selected experimental results are introduced to validate the theoretical contributions of this article.
16 citations
TL;DR: A series of bipolar output active rectifiers with center-tapped winding is proposed to serve as secondary rectification circuits and a family of isolated four-port converters with symmetrical bipolar outputs is further developed to integrate renewable energy and energy storage.
Abstract: Using a multiport converter to integrate renewable energy and energy storage into the bipolar dc bus is a desirable solution due to its high efficiency and reliability. In this article, a series of bipolar output active rectifiers with center-tapped winding is proposed to serve as secondary rectification circuits. Then, a family of isolated four-port converters with symmetrical bipolar outputs is further developed to integrate renewable energy and energy storage. The proposed symmetrical bipolar output isolated four-port converters can achieve single-stage power conversion, symmetrical bipolar output voltage, soft switching, and decoupled control. A typical four-port converter, named full-bridge interleaving bidirectional buck/boost + semiactive rectifier with bipolar output converter, is specifically analyzed in detail in terms of operation principles, voltage and power relationship, port current ripples, soft switching performance, and control. Finally, experimental tests have been performed to verify the feasibility and effectiveness of the proposed topology.
15 citations
TL;DR: A condition monitoring scheme for the dc-link capacitors used in ac/dc/ac pulsewidth-modulation converters based on the signal injection, which can estimate capacitance in real time when both the rectifier and the inverter are in normal operation is proposed.
Abstract: This article proposes a condition monitoring scheme for the dc-link capacitors used in ac/dc/ac pulsewidth-modulation converters based on the signal injection, which can estimate capacitance in real time when both the rectifier and the inverter are in normal operation. First, a low-frequency signal is injected into the dc-link voltage, and its effects on the total harmonic distortion (THD) of the input current are analyzed. Accordingly, a suitable injection frequency is selected to keep the THD of input current within limits prescribed by the IEEE standard. Then, a novel calculation method of capacitor current without any dc-link current sensor is given, where the converter system is still in normal operation and different inverter operations are both taken into consideration. Finally, capacitance estimation based on the slide discrete Fourier transform is introduced. At the end of this article, experiments have been done to validate the correctness of the conclusion and effectiveness of the proposed scheme.
13 citations
TL;DR: In this article, the authors proposed an IPT system with multiple semiactive rectifier cells (SARCs) connected in series at the receiver (Rx) side, which can maintain zero phase angle operation with unity power factor.
Abstract: Inductive power transfer (IPT) systems with multiple output voltages are potential to supply a variety of loads simultaneously. This article proposes an IPT system with multiple semiactive rectifier cells (SARCs) connected in series at the receiver (Rx) side. These SARCs are independent of each other and their output voltages can be regulated individually with single receiver coil, which reduces the cost and volume. The proposed IPT configuration has the advantages of high flexibility, simple control, and no cross regulation. Considering that the SARC may cause additional reactance and lead to detuning of the Rx side, variable inductor is introduced to ensure the full tuning condition. Thus, the proposed IPT system can maintain zero phase angle operation with unity power factor in the whole load range, minimizing the reactive power losses. In addition, both primary inverter and the SARCs can achieve zero voltage switching. To verify the feasibility and validity of the proposed IPT system, an experimental prototype with two outputs of 640 W/150 V and 400 W/120 V is built.
12 citations
TL;DR: Through time-domain analysis, this article reveals that with a dual-side 90° phase shift, the hard switching of the inverter can be avoided, the power level can be enhanced, and the discontinuous conduction mode can be avoid to eliminate noises.
Abstract: To increase the power density of a wireless power transfer (WPT) system, the coupling of coils can be strong. However, in a strongly coupled series–series WPT system with a diode rectifier, currents can be distorted and discontinuous, and first harmonic approximation is no longer valid. The inverter is likely to work in hard switching, leading to extra noise, decreased efficiency, and a potential hazard for a safe operation. Through time-domain analysis, this article reveals that with a dual-side 90° phase shift, the hard switching of the inverter can be avoided, the power level can be enhanced, and the discontinuous conduction mode can be avoided to eliminate noises. The factors impacting the soft switching operations of the inverter and the rectifier are analyzed. To achieve 90° dual-side phase shift, the conventional approach of using the receiver voltage/current, which can be distorted and discontinuous in strongly coupled WPT systems, for phase synchronization is no longer suitable. A new set of coils, namely driving coils, is used for phase synchronization so that dual-side phase shift can be implemented independent from power transfer. Experimental results have validated the effectiveness of the analysis.
12 citations
TL;DR: A control system of a three-phase grid-connected power converter, operating in the rectifier mode, which achieves the unity power factor target, i.e., unbalanced and distorted current instead of sinusoidal one for grid voltage imbalance and harmonics.
Abstract: This article proposes a control system of a three-phase grid-connected power converter, operating in the rectifier mode, which achieves the unity power factor target, i.e., unbalanced and distorted current instead of sinusoidal one for grid voltage imbalance and harmonics. Such a target is known from active power filters control, but it has not been used for power supply devices yet. Thanks to that, the three-phase converter is seen as resistive load by the utility grid, and active power is consumed with minimal possible rms current, keeping current asymmetry corresponding to the voltage asymmetry during unbalanced dips. Intentional introduction of current harmonics is not trivial from the point of view of both reference signals calculation and control system structure, because in the classical approach, it would require resonant terms in controller structure. Additionally, grid voltage asymmetry introduces another oscillating component, which imposes other resonant terms in the controller. The transformation presented in this article allows to achieve desirable current harmonics and asymmetry with the use of two proportional-integral controllers, one in each controlled axis. This article presents theoretical principles of the new transformation, control system structure as well as simulation and experimental tests of a three-phase converter utilizing this idea.
11 citations
TL;DR: This article takes a common parallel-connected 24-pulse rectifier as an example, researches its operation characteristics and fault tolerance under diode open-circuit fault conditions and determines that load voltage is the characteristic parameter that directly reflects the fault information.
Abstract: Multipulse rectifiers (MPRs) with dc side passive harmonic reduction circuits often have lower input current total harmonic distortion (THD) values and power losses, that fulfill power requirements for many industrial occasions. In addition to normal operation properties, fault tolerance is another aspect closely related to overall performance of MPRs. This article takes a common parallel-connected 24-pulse rectifier as an example, researches its operation characteristics and fault tolerance under diode open-circuit fault conditions. Operation modes under single or double diodes open-circuit fault in the main circuit, as well as diode open-circuit fault in the dc side harmonic reduction circuit are discussed in details. It can be determined that load voltage is the characteristic parameter that directly reflects the fault information. Related simulation and experimental verifications are performed, all results are consistence with theoretical waveforms. This article provides useful guidance for fault handling and clarifies factors related to the reliability of MPRs, which are helpful for novel MPRs design.
TL;DR: A novel high switching frequency isolated voltage fed hybrid bridge combing semi-active rectifier DC-DC converter is introduced for unidirectional power flow and wide voltage gain and a segmented control strategy is implemented on it.
Abstract: A novel high switching frequency isolated voltage-fed hybrid bridge combining semiactive rectifier dc–dc converter is introduced for unidirectional power flow and wide voltage gain. Three potentially appropriate working patterns are elaborated, including ideal output power derivation, current stress analysis, working voltage matching, output power distribution, soft switching characteristics, etc. In consideration of the optimization of the minimum of the root-mean-square value of the leakage inductor current, two truly applicable working patterns are selected. Meanwhile, based on the consideration of soft switching, a segmented control strategy is implemented on it. With the optimization of current stress and the realization of soft switching, the converter can theoretically realize higher efficiency operation. Eventually, the effectiveness of the proposed converter and the control strategy is verified by a 1 kW prototype.
01 Jan 2022
TL;DR: In this article, a dual-band and two-branch rectifier is proposed for wireless energy harvesting in the 2.45 and 5.8 GHz frequency bands, which achieves a maximum conversion efficiency of 59.683% for the primary band at 1dBm of incident power.
Abstract: In this paper, we present a novel design of high-efficiency, dual-band and two-branch rectifier for wireless energy harvesting in the 2.45 and 5.8 GHz frequency bands. The rectifier is based on a two conversion circuit; a dual-band voltage doubler for the first branch and a single-diode rectifier for the higher frequency band in order to further enhance in 5.8 GHz the efficiency of the resulting circuit. The rectifier achieves a maximum conversion efficiency of 59.683% for the primary band at 1dBm of incident power, while it reaches in the second band (5.8 GHz) at 3 dBm an efficiency of 51.521%. These results allowed the resulting rectifier to be the most efficient at these frequencies and in particular for the low incident powers compared to other reported designs with the same radio frequency conditions.
TL;DR: In this paper, a self-driven thyristor scheme comprised of only three components was proposed to reduce the size of the bulk capacitors in a 60-W GaN-based active-clamp flyback converter.
Abstract: Universal serial bus power delivery fast chargers equipped with wide-bandgap devices are driven to higher power density and efficiency. The indispensable high-voltage bulk capacitors used to smooth the rectifier output could take 40% of the total system volume due to the large capacitance value required. This letter discussed a capacitor reduction method using a self-driven thyristor scheme comprised of only three components in total. No extra control circuit is needed. Circuit analysis and design equations are presented, and the design results are implemented in a 60-W GaN-based active-clamp flyback converter. The measurement results on the prototype show a 36.4% reduction of the bulk-capacitor size with similar efficiency compared to the conventional solution.
TL;DR: In this paper, a cascaded power current controller is proposed to suppress the current pulsation in a single-phase rectifier, where the power current loop is cascaded between the speed and current loops.
Abstract: For a single-phase rectifier, a common issue is that there exists a component fluctuating at twice the grid frequency in dc-link voltage due to the fluctuating input power. This fluctuating dc-link voltage causes modulation error, which induces severe phase current pulsation at low frequency. An additional LC filter can suppress the voltage fluctuation at the cost of increasing volume and reducing power density. The conventional software method is achieved by the modulation ratio or frequency compensation. However, the compensation methods have limited performance. In this article, a cascaded power current controller is proposed to suppress the current pulsation. The power current is constructed and used as the control target. Accordingly, the power current loop is cascaded between the speed and current loops. Maintaining a constant power current beneficially rejects the current ripple. Compared to the conventional closed-loop method, the proposed method does not need a phase-locked loop or resonant controller. Therefore, it has the ability to suppress current pulsation within a wide frequency range, and can achieve improved dynamic performance due to the fast convergence. Experimental results confirm the expected performance of the proposed method.
TL;DR: In this paper, an inductance-matrix-based framework is proposed to evaluate the interaction among different generator ports, diode-bridge rectifiers, and the active rectifier that is used to control the power flow.
Abstract: An integrated generator–rectifier system is a promising architecture to harvest energy in offshore wind turbines. The system processes the majority of the incoming power using reliable, efficient, and inexpensive passive diodes operating at the generator line frequency. Elimination of capacitors at the diode rectifiers’ output by appropriately phase shifting the voltages of a multiport generator further improves the reliability of the overall architecture. This article creates a generalized framework to evaluate the interactions among different generator ports, diode-bridge rectifiers, and the active rectifier that is used to control the power flow. The framework enables quantifying the effect of integration on the dc bus power ripple and power imbalance among different generator ports. An exemplary winding layout is proposed that ensures theoretically zero interaction between the passive ports, although all the ports are mounted on a magnetic structure. A 10-MW integrated generator–rectifier design and simulation proves the accuracy of the framework using coupled circuit and finite-element simulation. Finally, a laboratory prototype shows the realization of the winding layout. The proposed inductance-matrix-based framework can be used to evaluate other winding layouts to estimate the effect of magnetic coupling on the performance of the system.
TL;DR: A method of reconfiguring the flying capacitor multilevel power conversion input stage for a wide voltage range of operation is revealed and components can be selected and optimized for very confined operating conditions.
Abstract: Wide input or output voltage range converters are required in various applications, including railway, industrial, military, aerospace, and many more. However, it has been challenging to achieve and maintain high efficiency under a wide range of input or output voltages of operation because of shifting operating conditions and compromised component selections required to cover a wide voltage range of operation. In this article, a method of reconfiguring the flying capacitor multilevel power conversion input stage is revealed for a wide voltage range of operation. A pulse voltage is produced by the input stage. With proper configuration under different input voltage levels, the voltage across key components, namely power switches, inductors, and capacitors, can be maintained relatively constant. In this way, components can be selected and optimized for very confined operating conditions. Also, the amplitude and frequency of the pulse voltage produced by the input stage are also maintained relatively constant. Therefore, a followed filter stage, a resonant tank, or an isolation + rectifier stage can be designed and operated with optimization. High and maintained overall efficiency are achieved over a wide change of the input voltage.
01 Jan 2022