Showing papers on "Rectifier published in 2018"
TL;DR: In this paper, an active single-phase rectifier (ASPR) with an auxiliary measurement coil (AMC) and its corresponding control method are proposed to track the maximum system efficiency under varied loads and detuning conditions in real time.
Abstract: The efficiency of wireless power transfer (WPT) systems is highly dependent on the load, which may change in a wide range in field applications. Besides, the detuning of WPT systems caused by the component tolerance and aging of inductors and capacitors can also decrease the system efficiency. In order to track the maximum system efficiency under varied loads and detuning conditions in real time, an active single-phase rectifier (ASPR) with an auxiliary measurement coil (AMC) and its corresponding control method are proposed in this paper. Both the equivalent load impedance and the output voltage can be regulated by the ASPR and the inverter, separately. First, the fundamental harmonic analysis model is established to analyze the influence of the load and the detuning on the system efficiency. Second, the soft-switching conditions and the equivalent input impedance of ASPR with different phase shifts and pulse widths are investigated in detail. Then, the analysis of the AMC and the maximum efficiency control strategy are provided in detail. Finally, an 800-W prototype is set up to validate the performance of the proposed method. The experimental results show that with 10% tolerance of the resonant capacitor in the receiver side, the system efficiency with the proposed approach reaches 91.7% at rated 800-W load and 91.1% at 300-W light load, which has an improvement by 2% and 10% separately compared with the traditional diode rectifier.
243 citations
TL;DR: In this paper, a pulse density modulation (PDM) based implementation for maximum efficiency point tracking (MEPT) was proposed to eliminate all the mentioned disadvantages of existing MEPT implementations.
Abstract: Maximum efficiency point tracking (MEPT) control has been adopted in state-of-the-art wireless power transfer (WPT) systems to meet the power demands with the highest efficiency against coupling and load variations. Conventional MEPT implementations use dc/dc converters on both transmitting and receiving sides to regulate the output voltage and maximize the system efficiency at the expense of increased overall complexity and power losses on the dc/dc converters. Other implementations use phase-shift control or on–off control of the transmitting side inverter and the receiving side active rectifier instead of dc/dc converters but cause new problems, e.g., hard switching, low average efficiency, and large dc voltage ripples. This paper proposes a pulse density modulation (PDM) based implementation for MEPT to eliminate all the mentioned disadvantages of existing implementations. Delta-sigma modulators are used as an example to realize the PDM. A dual-side soft switching technique is proposed for the PDM. The ripple factor of the output voltage with PDM is derived. A 50 W WPT system is built to validate the proposed method. The system efficiency is maintained higher than 70% for various load resistances when the power transfer distance is 0.5 m, which is 1.67 times the diameter of the coils.
139 citations
TL;DR: In this article, a flexible 2.45 GHz power harvesting wristband that generates a net dc output from a −24.3-dBm RF input is presented, which is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management.
Abstract: This paper presents a flexible 2.45-GHz wireless power harvesting wristband that generates a net dc output from a −24.3-dBm RF input. This is the lowest reported system sensitivity for systems comprising a rectenna and impedance-matching power management. A complete system has been implemented comprising: a fabric antenna, a rectifier on rigid substrate, a contactless electrical connection between rigid and flexible subsystems, and power electronics impedance matching. Various fabric and flexible materials are electrically characterized at 2.45 GHz using the two-line and the T-resonator methods. Selected materials are used to design an all-textile antenna, which demonstrates a radiation efficiency above 62% on a phantom irrespective of location, and a stable radiation pattern. The rectifier, designed on a rigid substrate, shows a best-in-class efficiency of 33.6% at −20 dBm. A reliable, efficient, and wideband contactless connection between the fabric antenna and the rectifier is created using broadside-coupled microstrip lines, with an insertion loss below 1 dB from 1.8 to over 10 GHz. A self-powered boost converter with a quiescent current of 150 nA matches the rectenna output with a matching efficiency above 95%. The maximum end-to-end efficiency is 28.7% at −7 dBm. The wristband harvester demonstrates net positive energy harvesting from −24.3 dBm, a 7.3-dB improvement on the state of the art.
103 citations
TL;DR: In this article, a triple band differential rectenna for RF energy harvesting applications is proposed, which is designed to operate in frequency bands of universal mobile telecommunication service (2.1 GHz), lower WLAN/Wi-Fi (2, 2.48 GHz), and WiMAX (3.3-3.8 GHz).
Abstract: A triple band differential rectenna for RF energy harvesting applications is proposed in this paper. The rectenna is designed to operate in frequency bands of universal mobile telecommunication service (2.1 GHz), lower WLAN/Wi-Fi (2.4–2.48 GHz), and WiMAX (3.3–3.8 GHz). For designing the proposed rectenna, first a differentially fed multiband slot antenna that works as the front-end receiving unit is designed, fabricated, and tested to check its performance. It is observed that a peak antenna gain of 7, 5.5, and 9.2 dBi is achieved at 2, 2.5, and 3.5 GHz, respectively. In the next step, a triple band differential rectifier is designed using the Villard voltage doubler where interdigital capacitors (IDCs) in lieu of lumped components are used. The full rectifier circuit comprising of the rectifying unit and impedance matching circuit is fabricated and tested to check its performance in the desired bands. The peak RF-dc conversion efficiency of 68% is obtained using the three-tone measurement. In the final stage, both antenna and the rectifier circuit are integrated through SMA connecter in order to implement the proposed rectenna. Measurement of the proposed rectenna shows an approximate maximum efficiency of 53% at 2 GHz, 31% at 2.5 GHz, and 15.56% at 3.5 GHz.
100 citations
TL;DR: A nonlinear adaptive backstepping controller is designed to control the common dc-bus voltage for different components in a dc microgrid under various operating conditions.
Abstract: In this paper, a nonlinear adaptive backstepping controller is designed to control the common dc-bus voltage for different components in a dc microgrid under various operating conditions. The dc microgrid in this paper comprises a solar photovoltaic (PV) unit, a battery energy storage system (BESS), a backup diesel generator, and loads (both critical and noncritical). The controllers are designed for all components except loads where the main control objective for all controllers is to maintain a constant voltage at the dc-bus where all components are connected. This paper considers solar PV systems as the renewable energy source, whereas a diesel generator equipped with a rectifier is used as a backup supply to maintain the continuity of power supply in the case of emergency situations. The proposed controller is designed recursively based on the Lyapunov control theory, where all parameters within the model of different components are considered unknown. Adaptation laws are used to estimate these unknown parameters while the stability of the dc microgrid, with these adaptation laws, is ensured through the formulation of suitable control Lyapunov functions (CLFs) at different stages of the design process. The negative definiteness or semidefiniteness of these CLFs guarantees the stability of the dc microgrid. Finally, the performance of the proposed controllers is verified using both simulations and experiments on a test dc microgrid under different operating conditions. The proposed controller ensures the regulation of the dc-bus voltage within the acceptable limits under different operating conditions.
93 citations
TL;DR: The proposed secondary-side control method not only achieves CC charging, but also ensures no reactive impedance seen into the semiactive rectifier, which improves the system performance and is suitable for the applications that require compact receiver and no wireless communication link between the transmitter and the receiver.
Abstract: Charging current and efficiency of a wireless power transfer system depend on the equivalent load resistance of supercapacitor load, which varies during charging. To achieve constant current (CC) charging and maximized efficiency under variable loads, control method that employs primary-side phase shift H-bridge inverter and secondary-side semiactive rectifier are proposed. The proposed secondary-side control method not only achieves CC charging, but also ensures no reactive impedance seen into the semiactive rectifier. Furthermore, the maximum efficiency tracking is based on searching the minimum system dc input current for any given output power. It is realized by phase shift H-bridge inverter that is controlled by the perturbation and observation algorithm. Simulation and experimental results validate the feasibility of the proposed control method. During CC charging of 3 A, the maximum efficiency is 81% and largest efficiency improvement is 15.2% at light load. The proposed control method improves the system performance and is suitable for the applications that require compact receiver and no wireless communication link between the transmitter and the receiver.
90 citations
TL;DR: The dq-frame impedance measurement method for single-phase systems based on the Hilbert transform is proposed, and the modeling approach is verified by the frequency-domain simulations on the switching models.
Abstract: The utilization of a large number of power electronic converters in the high-speed railway system results in the low-frequency instability for the single-phase vehicle-grid system. In order to probe into the problem, the impedance-based approach is adopted. This paper focuses on the dq -frame impedance modeling and verification of the single-phase converters in the electric multiple units. The closed-loop input impedance modeling methods for both single converter and interleaved converters considering the second-order generalized integrator-based phase-locked loop (PLL) are put forward. Then, the dq -frame impedance measurement method for single-phase systems based on the Hilbert transform is proposed, and the modeling approach is verified by the frequency-domain simulations on the switching models. The good agreement of the model and simulation illustrates that the modeling method is suitable and accurate enough until half of the switching frequency. It is elucidated that the single-phase rectifier's impedance has the off-diagonal characteristic and the negative-impedance characteristic on the dd channel at low frequencies. Moreover, both the current and voltage controls have influences on the negative impedance shaping, while PLL does not.
85 citations
TL;DR: This work demonstrates a new type of THz detector and proposes a method for manipulating ultrafast charge-carrier dynamics through the field enhancement of the nano-electrode, which can be applied to ultrafast photonic and electronic devices.
Abstract: Rectifiers have been used to detect electromagnetic waves with very low photon energies In these rectifying devices, different methods have been utilized, such as adjusting the bandgap and the doping profile, or utilizing the contact potential of the metal-semiconductor junction to produce current flow depending on the direction of the electric field In this paper, it is shown that the asymmetric application of nano-electrodes to a metal-semiconductor-metal (MSM) structure can produce such rectification characteristics, and a terahertz (THz) wave detector based on the nano-MSM structure is proposed Integrated with a receiving antenna, the fabricated device detects THz radiation up to a frequency of 15 THz with responsivity and noise equivalent power of 108 V/W and [Formula: see text] respectively, estimated at 03 THz The unidirectional current flow is attributed to the thermionic emission of hot carriers accelerated by the locally enhanced THz field at the sharp end of the nano-electrode This work not only demonstrates a new type of THz detector but also proposes a method for manipulating ultrafast charge-carrier dynamics through the field enhancement of the nano-electrode, which can be applied to ultrafast photonic and electronic devices
80 citations
TL;DR: This paper proposes a secondary-side resonance scheme to shape the primary current waveform in a way that significantly improves synchronous rectifier operation and reduces primary rms current.
Abstract: Both high switching frequency and high efficiency are critical in reducing power adapter size. The active clamp flyback (ACF) topology allows zero voltage soft switching (ZVS) under all line and load conditions, eliminates leakage inductance and snubber losses, and enables high frequency and high power density power conversion. Traditional ACF ZVS operation relies on the resonance between leakage inductance and a small primary-side clamping capacitor, which leads to increased rms current and high conduction loss. This also causes oscillatory output rectifier current and impedes the implementation of synchronous rectification. This paper proposes a secondary-side resonance scheme to shape the primary current waveform in a way that significantly improves synchronous rectifier operation and reduces primary rms current. The concept is verified with a ${\mathbf{25}}\hbox{--}{\text{W/in}}^{3}$ high-density 45-W adapter prototype using a monolithic gallium nitride power IC. Over 93% full-load efficiency was demonstrated at the worst case 90-V ac input and maximum full-load efficiency was 94.5%.
79 citations
TL;DR: The techniques to design the critical parameters including switching frequency, the highest harmonic order that can be mitigated using the proposed current-reference-based technique, and the coupling inductance that can attenuate the current harmonic orders above the highest order are investigated.
Abstract: In this paper, a selective harmonic current mitigation pulsewidth modulation (SHCM-PWM) technique with low switching frequencies is proposed for grid-connected cascaded H-bridge multilevel rectifiers to fully meet harmonic requirements within extended harmonic spectrum. In the proposed technique, instead of using the voltage references to calculate switching angles for the rectifier as in conventional selective harmonic elimination-PWM (SHE-PWM) or selective harmonic mitigation-PWM (SHM-PWM), current references are used to compensate the current harmonics due to both grid voltage harmonics and rectifier input voltage harmonics so as to meet the current harmonic requirements and total demand distortion within the whole harmonic spectrum. Furthermore, the techniques to design the critical parameters including switching frequency, the highest harmonic order that can be mitigated using the proposed current-reference-based technique, and the coupling inductance that can attenuate the current harmonic orders above the highest order are investigated. With the same switching frequency, the proposed SHCM-PWM technique uses smaller coupling inductance to meet higher orders of current harmonic requirements than the conventional SHE-PWM technique. Finally, simulations and experiments were conducted to validate the proposed technique.
76 citations
TL;DR: In this article, a self-enhancing conditioning circuit (CC) that exponentially amplifies the output electrical energy converted from the mechanical domain of a T-ENG, in orders of magnitude compared to traditional CC, is presented.
TL;DR: In this paper, an adaptive neural (AN) estimator is used in voltage-oriented control to eliminate the grid voltage sensors, and a new startup process is proposed to ensure a smooth starting of the system.
Abstract: This paper proposes a new ac voltage sensorless control scheme for the three-phase pulse-width modulation rectifier. A new startup process to ensure a smooth starting of the system is also proposed. The sensorless control scheme uses an adaptive neural (AN) estimator inserted in voltage-oriented control to eliminate the grid voltage sensors. The developed AN estimator combines an AN network in series with an AN filter. The AN estimator structure leads to simple, accurate, and fast grid voltages estimation, and makes it ideal for low-cost digital signal processor implementation. Lyapunov-based stability and parameters tuning of the AN estimator are performed. Simulation and experimental tests are carried out to verify the feasibility and effectiveness of the AN estimator. Obtained results show that the proposed AN estimator presented faster convergence and better accuracy than the second-order generalized integrator-based estimator; the new startup procedure avoided the overcurrent and reduced the settling time; and the AN estimator presented high performances even under distorted and unbalanced grid voltages.
01 Sep 2018
TL;DR: This paper presents the design, analyses and implementation of an optimized single stage high power wireless charging system capable of transferring 100 kW at an operating frequency of 22 kHz and a coil-to-coil distance of 5 inches.
Abstract: This paper presents the design, analyses and implementation of an optimized single stage high power wireless charging system capable of transferring 100 kW at an operating frequency of 22 kHz and a coil-to-coil distance of 5 inches. The detailed design and implementation of the power electronics including the high frequency inverter and rectifier and wireless power transfer coils along with the resonant stage are described. FEA simulation results of the coils and the resonant network analysis are validated by using a Venable frequency response analyzer. Experimental results corresponding to 50 kW operation are presented to validate the design process.
14 Mar 2018
TL;DR: In this paper, a 2.4 GHz rectifying patch antenna (rectenna) is designed and tested for near-field charging and activation of medical implant devices using radiating antennas.
Abstract: A radiating near-field method of recharging and activating medical implants using a 2.4-GHz rectifying patch antenna (rectenna) is designed and tested. Traditional near-field charging uses magnetically coupled coils, but these are highly sensitive to misalignments between the transmitter and receiver. In contrast, the proposed design employs the principles of wireless power transfer using radiating antennas. These antennas provide a misalignment-insensitive power delivery method, even when the receive antenna footprint is small (27.5 mm × 19.75 mm). A misalignment analysis is performed up to 15 cm, showing a maximum loss of 7.5 dB. As a proof-of-concept demonstration, a rectenna receiver was fabricated consisting of a patch antenna attached to a radio frequency (RF) rectifier. This integrated rectifier is a voltage quadrupling circuit that provides RF–DC rectification with efficiency of 40% at 0 dBm. For validation, a real-time actuation of a medical drug pump is demonstrated using only wirelessly transmitted power with no additional power storage elements.
TL;DR: In this article, a frequency-selective surface (FSS) was designed and optimized for ambient RF energy harvesting, and a matched full-wave rectifier integrated with the absorber FSS was fabricated to demonstrate its performance.
Abstract: We present a frequency-selective surface (FSS) that is specially designed and optimized for ambient RF energy harvesting. The unit cell geometry incorporates channeling features in order to combine the collected power from multiple unit cells, allowing for efficient operation under low-power conditions. To demonstrate its performance, we designed and fabricated a matched full-wave rectifier integrated with the absorber FSS. Radiated measurements for the complete rectenna system are included in this paper demonstrating strong agreement with the simulation results. The proposed periodic structure absorbs 97% of the available energy at its resistive load, thus making it an ideal candidate for energy harvesting and channeling applications. Overall Radiation-to-dc conversion efficiency of the fabricated prototype was measured to be 61% when the collected power at the rectifier was 15 dBm.
TL;DR: In this paper, a new model predictive direct power control (MP-DPC) was proposed to overcome the drawbacks of model predictive control for single phase three-level rectifiers in the railway traction drive system, including huge online calculation, poor power control precision at the low switching frequency and variable switching frequency.
Abstract: This paper presents a new model predictive direct power control (MP-DPC) to overcome the drawbacks of model predictive control (MPC) for single phase three-level rectifiers in the railway traction drive system, including huge online calculation, poor power control precision at the low switching frequency and variable switching frequency. To do so, an exact analytical solution of instantaneous power estimation is adopted to predict active and reactive powers in next duty cycle updating interval for achieving the deadbeat control and reducing the predictive error at the low switching frequency (below 1 kHz). The optimal d -axis and q -axis components of input voltage within next duty cycle updating interval of the adopted rectifier in rotating coordinate system are directly calculated by minimizing the cost function. And the optimal drive pulses are generated by pulse width modulation stage in the proposed MP-DPC, other than evaluating cost function for each voltage vector in traditional MP-DPC. Finally, the influence of inductance mismatch on control system is analyzed, and an inductance estimation method is shown to improve the control precision. An experimental comparison with other five different DPC schemes has verified the effectiveness of the proposed MP-DPC scheme.
TL;DR: In this article, an optimal six-segment PWM scheme (type A) is proposed. But the analysis is limited to the three-phase isolated buck matrix-type rectifier.
Abstract: This paper first starts with reviewing several commonly practiced PWM schemes for the three-phase isolated buck matrix-type rectifier. Then, an optimal six-segment PWM scheme (“Type A”) is proposed. The analysis shows “Type A” PWM scheme has lower duty-cycle loss, maximum output inductor current ripple, and minimum switching loss comparing with other PWM schemes when the mosfet devices are employed. In addition, a low input current total harmonic distortion (THD) can be achieved with duty-cycle compensation. Finally, the steady-state analysis of duty-cycle loss, inductor current ripple, and THD are all compared and verified by the experimental results for “Type A” PWM and eight-segment PWM (“Type E”).
TL;DR: In this paper, a transmitter coil and a receiver coil were designed at 6.78 MHz for magnetic resonant wireless power transfer systems not only to have high efficiency at medium distances, which is comparable to the coil dimensions, but also to provide stable efficiency over the position variation of the receiver coil.
Abstract: A transmitter coil (TX-coil) as well as a receiver coil (RX-coil) has been designed at 6.78 MHz for magnetic resonant wireless power transfer systems not only to have high efficiency at medium distances, which is comparable to the coil dimensions, but also to provide stable efficiency over the position variation of the RX-coil. For mobile devices, the coils should be compact and have low profile and asymmetric, meaning that TX- and RX-coils have different dimensions. In this paper, TX-coil is designed by adding a small coil in series to achieve high quality factor (Q-factor) as well as relatively uniform magnetic field distribution. On the other hand, the scaling factor is introduced for wire width to design RX-coil with higher Q-factor. As a result, the proposed asymmetric coils reveal improved efficiency and degree of freedom in terms of position variation. This has been verified by measuring the system performance, including a power amplifier, full-wave rectifier, regulator, and load. The proposed TX-coil has size of $200 \times 200 \times 1$ mm3, while the size of the RX-coil is $100\times 100\times0.4$ mm3. The power transfer efficiency is 96% and 39% at the transmission distances of 50 and 300 mm, respectively.
TL;DR: A power compensation method is derived aiming at eliminating dc voltage oscillations, achieving sinusoidal grid current, and obtaining unity power factor, and the superiority of the proposed method over the prior DPC-SVM is validated by both simulation and experimental results obtained on a two-level pulsewidth modulation voltage source rectifier.
Abstract: Direct power control with space vector modulation (DPC-SVM) features simple structure, fast dynamic performance, and little tuning work. However, the conventional DPC-SVM cannot achieve accurate power control under unbalanced grid conditions. A modified DPC-SVM is thus proposed for accurate power control under both ideal and unbalanced grid conditions. Though the power control accuracy is improved when compared with the conventional DPC-SVM, it still suffers highly distorted grid current and dc voltage oscillations with an unbalanced network. Therefore, a power compensation method is subsequently derived aiming at the following targets: eliminating dc voltage oscillations, achieving sinusoidal grid current, and obtaining unity power factor. To that end, average grid-side reactive power and oscillations in converter-side active power are controlled as zero by simply adding a compensation to original power reference. Additionally, the proposed method does not require extraction of a positive sequence or negative sequence component of grid voltage. Compared with the conventional DPC-SVM in an ideal grid, only additional compensation of power reference is required. As a result, control performance can be significantly improved without substantial increase in complexity. The superiority of the proposed method over the prior DPC-SVM is validated by both simulation and experimental results obtained on a two-level pulsewidth modulation voltage source rectifier.
TL;DR: A single-stage WPT resonant converter with bridgeless boost power-factor-correction (PFC) rectifier is proposed to improve efficiency and power quality of line input, and reduce production cost and complexity for high-power WPT system.
Abstract: Wireless power transfer (WPT) has drawn more and more attention and has many applications, such as wireless electric vehicle charging systems, which require high power, high efficiency, and high power factor. In this paper, a single-stage WPT resonant converter with bridgeless boost power-factor-correction (PFC) rectifier is proposed to improve efficiency and power quality of line input, and reduce production cost and complexity for high-power WPT system. The bridgeless single-stage topology is creatively proposed to apply in WPT system, which is much more advantageous than conventional two-stage WPT converter with individual boost PFC stage.
TL;DR: A compact dual-band impedance matching network is introduced and applied to the design of rectifying circuits and theoretical analysis is carried out and closed-form design formulas are derived.
Abstract: In this brief, a compact dual-band impedance matching network is introduced and applied to the design of rectifying circuits. The matching network can work at two arbitrary frequencies with arbitrary complex impedance simultaneously. Theoretical analysis is carried out and the closed-form design formulas are derived. For validation, a dual-band rectifier working at 0.915 and 2.45 GHz is implemented. The measured maximum RF-to-dc efficiencies are 77.2% and 73.5% at 0.915 and 2.45 GHz, respectively.
TL;DR: The proposed voltage modulated direct power control for three-phase pulsewidth modulated rectifier has guaranteed that the closed system is globally exponentially stable.
Abstract: In this paper, a voltage modulated direct power control for three-phase pulsewidth modulated rectifier is proposed. With the suggested method, the differential equations describing the rectifier dynamics are changing from a linear time-varying system into a linear time-invariant one. In this way, conventional feedback and feedforward controllers are applicable for the independent control of active and reactive powers. The proposed method has guaranteed that the closed system is globally exponentially stable. A feedback linearization method is also employed for generating the active power reference of inner loops. Finally, some experimental tests are conducted to verify its effectiveness.
TL;DR: Theoretical analysis and performance comparison show that the proposed topology of a novel rectifier with power recycling based on a branch-line coupler features recycling ability within a wide input power range.
Abstract: In this brief, a novel rectifier with power recycling based on a branch-line coupler is proposed to operate within a wide input power range. In the proposed topology, two output ports of the coupler are connected with two subrectifiers dealing with higher power level (main branches), while the isolation port is connected with the subrectifier dealing with lower power level (power recycling branch). By using the branch-line coupler, the power reflected from the two main branches can be efficiently transmitted to the power recycling branch. Consequently, the power can be reused and thus the RF-dc conversion efficiency can be improved. In this way, the rectifier can maintain high efficiency in a wide input power range. Theoretical analysis and performance comparison are carried out, which show that the proposed topology features recycling ability within a wide input power range. For validation, a rectifier working at 2.45 GHz is implemented and compared to other designs. The measured efficiency remains over 50% from 8.5 to 32.5 dBm, indicating that high efficiency can be obtained within wide input power range.
TL;DR: In this paper, a modular isolated soft-switching dc-dc converter that can offer two levels of fault tolerance is proposed, which consists of input-parallel-output-series (IPOS) connected modules.
Abstract: A modular isolated soft-switching dc–dc converter that can offer two levels of fault tolerance is proposed. A typical application is the wind energy conversion system used in offshore series-dc wind farm concept. The converter consists of input-parallel-output-series (IPOS) connected modules. Each module is a full-bridge dc–dc converter with an active rectifier, which can achieve zero voltage switching for all primary side switches and zero current switching for all secondary side switches and diodes. Under normal operation, the converter is operated with secondary phase-shifted modulation. When tolerable fault occurs in certain module, reconfiguration method ensures uninterrupted operation for the system. Additionally, modular structure provides another level of fault tolerance. More benefits of IPOS structure include reduced input current and output voltage of each module, module shedding capability, reduced ripple content due to interleaving, intrinsic balancing, and scalable control method. Both normal and faulty operations are simulated and also verified by scaled-down prototype experiment.
TL;DR: The authors exploit the use of electromagnetic waves from broadcasters to power wireless sensors and propose to realize harvesting operation at typical ambient radio frequency power levels found within urban environments.
Abstract: Energy harvesting technologies are required for autonomous applications, like sensors, for which a long-time power sourcing from a battery is infeasible. An energy harvester converts different forms of environmental energy into electricity. It can replace, totally or partially, the batteries of certain micro-systems that have low-energy requirements. Therefore, the authors exploit the use of electromagnetic waves from broadcasters to power wireless sensors. The authors propose to realize harvesting operation at typical ambient radio frequency power levels found within urban environments. To explore the potential for ambient RF energy harvesting, an RF spectral survey was undertaken from outside in Paris. The average RF power in the frequency range 0.9-3 GHz is about -12 dBm. The harvester includes an antenna, an impedance-matching network, and a rectifier; it was designed to cover two frequency bands from the largest RF contributors (GSM1800 and UMTS Band 1). A prototype is designed, fabricated, and measured. The RF-to-DC rectifier and the choice of the load to optimize the amount of DC power are presented. An efficiency of ~45% was observed experimentally for the UMTS Band 1 and 33% for the GSM1800, whenever the incident power is -7 dBm. Numerical and experimental data are reported and discussed.
TL;DR: Novel single- and dual-band complex impedance compression networks are proposed and applied to the design of rectifying circuits for efficiency improvement and the experimental results show that the proposed rectifiers with the ICN can improve the efficiency at low input power levels without degrading the maximum conversion efficiency.
Abstract: In this paper, novel single- and dual-band complex impedance compression networks (ICNs) are proposed and applied to the design of rectifying circuits for efficiency improvement. The proposed ICNs are connected to the microwave input of two parallel subrectifiers. They reduce the variation ranges of the rectifier input impedance, which change with input power. Thus, the loss due to impedance mismatch is reduced, and high conversion efficiency can be obtained over wider input power ranges. Compared with the resistance compression networks (RCNs), the proposed ICNs are able to compress the variation range of the complex impedance, rather than that of the resistance, featuring design flexibility. A detailed analysis is carried out. For demonstration, a 2.45-GHz rectifier and a dual-band rectifier working at 2.45 and 5.8 GHz for the industrial, scientific, and medical band are implemented based on the ICN. The experimental results show that, in comparison to the counterparts without the ICN, the proposed rectifiers with the ICN can improve the efficiency at low input power levels without degrading the maximum conversion efficiency. Besides, the ICN-based rectifiers have a much simpler circuit structure than the RCN-based rectifiers.
TL;DR: In this article, a hybrid rectifier consisting of a 12-pulse rectifier in parallel with a Vienna rectifier is presented, and a detailed analysis of how to select the output power sharing ratio based on system losses and input current distortion is presented.
Abstract: This paper presents a hybrid rectifier consisting of a 12-pulse rectifier in parallel with a Vienna rectifier. In the proposed structure, the 12-pulse rectifier supplies the bulk power to the load, whereas the Vienna rectifier shapes the input current to reduce its harmonic distortion. The unidirectional power flow of the Vienna rectifier results in undesirable distortion around the current zero crossing, which deteriorates current shaping in this region. To overcome this problem, besides current shaping, the Vienna rectifier is forced to participate in the active power. In this regard, the share of output power in each rectifier module must be calculated. To shape the input current, the reference current for the Vienna rectifier is generated using instantaneous power theory, and current tracking is carried out using the finite control set model predictive control. A detailed analysis of how to select the output power sharing ratio based on system losses and input current distortion is presented. The theoretical analysis is verified by using simulation and experimental results obtained from a 1 kW laboratory setup.
TL;DR: In this article, a 3 kW, three-phase, two-channel interleaved Vienna-type rectifier with greater than 99% efficiency is presented, with particular attention paid to the switching-frequency circulating current generated by the interleaving operation.
Abstract: In this paper, the design and implementation of a 3 kW, three-phase, two-channel interleaved Vienna-type rectifier with greater than 99% efficiency is presented. The operating principle of the interleaved Vienna-type rectifier is introduced, with particular attention paid to the switching-frequency circulating current generated by the interleaved operation, as well as effective mitigation methods. An optimized design procedure for the converter is then presented to achieve maximum efficiency, for which detailed loss calculation models and hardware design guidelines are developed and introduced. Finally, experimental results obtained with a 3 kW experimental prototype are presented for validation purposes, demonstrating the 99.28% extreme efficiency attained by the converter at nominal load, in close agreement with the 99.32% predicted by the design procedure developed.
TL;DR: To achieve high power efficiency independent of coupling, inherent regulation properties of resonant converters are utilized to avoid losing soft switching for any coupling value, and the optimal load is presented to the IPT link at the maximum energy throughput coupling.
Abstract: In typical multi-MHz inductive power transfer (IPT) systems, a change in coupling or load resistance can significantly deteriorate the end-to-end efficiency due to a deviation from the optimal load of the IPT link and suboptimal operation of the resonant inverter due to the loss of soft switching condition. This paper proposes solutions for an IPT system to operate efficiently when large changes in coupling take place. To achieve high power efficiency independent of coupling, we utilize inherent regulation properties of resonant converters to avoid losing soft switching for any coupling value, and present the optimal load to the IPT link at the maximum energy throughput coupling. A probability-based model is introduced to assess and optimize the IPT system by analyzing coupling as a distribution in time, which depends on the dynamic behavior of the wireless charging system. The proposed circuits are a Class D rectifier with a resistance compression network in the receiving end and a load-independent Class EF inverter in the transmitting end. Experiments were performed at 6.78 and 13.56 MHz verifying high efficiency for dynamic coupling and variable load resistance. End-to-end efficiencies of up to 88% are achieved at a coil separation larger than one coil radius for a system capable of supplying 150 W to the load, and the energy efficiency was measured at 80% when performing a uniformly distributed linear misalignment of 0–12.5 cm, corresponding to a receiver moving at a constant velocity over a transmitter without power throughput control.
TL;DR: In this paper, a multiband dual-polarized rectenna for RF energy harvesting in C-band application range is presented, where a matching network has been designed and is connected in between receiving antenna and the rectifier circuitry in order to match the antenna and load in different frequency bands.
Abstract: The paper presents a multiband dual polarized rectenna for RF energy harvesting in C-band application range. The receiving antenna of the designed rectenna is consisting of a truncated corner square patch loaded with several circular slots, L-slots and U-slot. A proximity coupled feeding arrangement is used for obtaining a wide impedance bandwidth so that the complete C-band from 4 to 8 GHz can be covered. The proposed antenna has the advantage of compact size and dual polarization since circular polarization is realized at three bands (5.42 GHz, 6.9 GHz and 7.61 GHz) in the −10 dB impedance bandwidth range. For efficient RF to DC conversion a two-stage voltage doubler rectifier is used considering that it provides a higher voltage multiplication with a small threshold voltage at its primary stage. For ensuring maximum RF to DC conversion efficiency; a matching network has been designed and is connected in between receiving antenna and the rectifier circuitry in order to match the antenna and load in different frequency bands. It is observed that a maximum conversion efficiency of 84% is achieved at 5.76 GHz. The proposed rectenna has been fabricated and it is found that measured results are in good match with the simulated results.