Showing papers on "Inductor published in 2021"

A Novel Generalized Common-Ground Switched-Capacitor Multilevel Inverter Suitable for Transformerless Grid-Connected Applications

Abstract: Recent research on common-ground switched-capacitor transformerless (CGSC-TL) inverters shows some intriguing features, such as integrated voltage boosting ability, possible multilevel output voltage generation, and nullification of the leakage current issue. However, the number of output voltage levels and also the overall voltage boosting ratio of most of the existing CGSC-TL inverters are limited to five and two, respectively. This article presents a generalized circuit configuration of such converters capable of higher voltage gain and output voltage levels generation. A basic five-level (5L) CGSC-TL inverter is first proposed using eight power switches and two self-balanced dc-link capacitors. A generalized extension of the circuit for any output voltage levels and voltage gain is then presented while keeping all the traits of the proposed basic 5L-CGSC-TL inverter. The circuit descriptions, control strategy, design guidelines, comparative study, and the relevant simulation and experimental results for the proposed 5L-CGSC-TL inverters and its seven-level derived topology are presented to validate the effectiveness and feasibility of this proposal.

A Novel Modified Switched Inductor Boost Converter With Reduced Switch Voltage Stress

Abstract: Recently, switched inductor (SI) and switched capacitor techniques in dc–dc converter are recommended to achieve high voltage by using the principle of parallel charging and series discharging of reactive elements. It is noteworthy that four diodes, one high-voltage rating switch, and two inductors are required to design classical SI boost converter (SIBC). Moreover, in classical SIBC, the switch voltage stress is equal to the output voltage. In this article, modified SIBC (mSIBC) is proposed with reduced voltage stress across active switches. The proposed mSIBC configuration in this article is transformerless and simply derived by replacing the one diode of the classical SI structure with an active switch. As a result, mSIBC required low-voltage rating active switches, since the total output voltage is shared into two active switches. Moreover, the proposed mSIBC is low in cost, provides higher efficiency, and requires the same number of components compared with the classical SIBC. The continuous conduction mode and discontinuous conduction mode analysis, the effect of nonidealities on voltage gain, design methodology, and comparison are presented in detail. The operation and performance of the designed 500-W mSIBC are experimentally validated under different perturbations.

Soft-Switching Solid-State Transformer With Reduced Conduction Loss

Abstract: Solid-state transformers (SSTs) are a promising solution photovoltaic (PV), wind, traction, data center, battery energy storage system (BESS), and fast charging electric vehicle (EV) applications. The traditional SSTs are typically three-stage, i.e., hard-switching cascaded multilevel rectifiers and inverters with dual active bridge (DAB) converters, which leads to bulky passives, low efficiency, and high electromagnetic interference (EMI). This article proposes a new soft-switching solid-state transformer (S4T). The S4T has full-range zero-voltage switching (ZVS), electrolytic capacitor-less dc link, and controlled dv/dt , which reduces EMI. The S4T comprises two reverse-blocking current-source inverter (CSI) bridges, auxiliary branches for ZVS, and transformer magnetizing inductor as a reduced dc link with 60% ripple. Compared with the prior S4T, an effective change on the leakage inductance diode is made to reduce the number of the devices on the main power path by 20% for significant conduction loss saving and retain the same functionality of damping the resonance between the leakage and resonant capacitors and recycling trapped leakage energy. The conduction loss saving is crucial, being the dominating loss mechanism in SSTs. Importantly, the proposed single-stage SST not only holds the potential for high power density and high efficiency but also has full functionality, e.g., multiport dc loads integration, voltage regulation, and reactive power compensation, unlike the traditional single-stage matrix SST. The S4T can achieve single-stage isolated bidirectional dc–dc, ac–dc, dc–ac, or ac–ac conversion. It can also be configured input-series output-parallel (ISOP) in a modular way for medium-voltage (MV) grids. Hence, the S4T is a promising candidate for the SST. The full functionality, e.g., voltage buck–boost, multiport, etc., and the universality of the S4T for the dc–dc, dc–ac, and ac–ac conversion are verified through the simulations and experiments of two-port and three-port MV prototypes based on 3.3 kV SiC mosfet s in dc–dc, dc–ac, and ac–ac modes at 2 kV.

Improved Hybrid Switched Inductor/Switched Capacitor DC–DC Converters

Abstract: High voltage gain dc–dc converters are widely used in various applications like low-voltage sustainable sources. In traditional boost converters, the voltage gain is limited by high voltage stress, high current ripple, and low efficiency due to employing a high duty cycle ratio. In this article, we propose converters that are a combination of four substructures, namely active switched inductor, passive switched inductor, switched capacitor cell, as well as an auxiliary switch with nonisolated configuration. The proposed structures have high voltage gain compared to the conventional either switched inductor-based or switched capacitor-based ones in addition to a low duty cycle ratio. By adding an auxiliary switch, the efficiency is improved, particularly for high voltage gains. The principle of operation and steady-state analysis are discussed in detail. Also, simulation results from PSCAD/EMTDC software are validated by a prototype built for experimental examination. The results demonstrated that the voltage gain and efficiency could be improved by utilizing the auxiliary switch.

A High Efficiency High Density DC/DC Converter for Battery Charger Applications

Abstract: Increased attention is being paid to the solid-state-transformer (SST) based charging station which requires a high efficiency high power density DC/DC stage. This framework would provide universal charging for all electric vehicles (EVs) no matter their battery voltage is 400 V or 800 V. In this paper, a two stage DC/DC converter consisting of a three-phase (3P) CLLC converter and four-phase interleaving Buck converter is proposed to achieve a wide output voltage range from 200 V to 800 V with bi-directional energy transfer capability. With SiC devices, a PCB winding based six-leg integrated transformer is used for the 3P transformer, and a PCB winding based EI core is used for the negative coupling inductors. The detailed design process of integrated magnetics is presented. A 12.5 kW prototype with over 97.7 % efficiency and 100 W/in3 power density is built to verify the feasibility of the proposed structure.

Extension of ZVS Region of Series–Series WPT Systems by an Auxiliary Variable Inductor for Improving Efficiency

Abstract: To maintain a stable output voltage under various operating conditions without introducing extra dc/dc converters, phase-shift (PS) control is usually adopted for wireless power transfer (WPT) systems. By using this method, however, zero-voltage switching (ZVS) operation cannot be guaranteed, especially in light-load conditions. To achieve high efficiency and reduce electromagnetic interference, it is significant for WPT systems to achieve ZVS operation of all switching devices in the whole operation range. In this article, an auxiliary variable inductor, of which the equivalent inductance can be controlled by adjusting the dc current in its auxiliary winding, is designed for series–series-compensated WPT systems under PS control to mitigate the loss arising from hard switching. As a result, a wide ZVS operation range of all switching devices can be achieved. A laboratory prototype is built to verify the theoretical analysis. The experimental results show that, under load and magnetic coupling variations, ZVS operation at fixed operation frequency as well as a constant dc output voltage can be maintained. Compared to the conventional method with only PS control, the proposed WPT can achieve higher overall efficiency in a wider load range owing to the wide ZVS operation range.

A Field Enhancement Integration Design Featuring Misalignment Tolerance for Wireless EV Charging Using LCL Topology

Abstract: This article proposes a magnetic integration design for EV wireless power transfer (WPT) systems, where the compensation and transmitting coils overlap one on top of the other to share the ferrite layer without any decoupling consideration. The magnetic field generated by both the compensation and transmitting coils are exploited to transfer power. To this end, a compensation method is proposed to enable magnetic field enhancement without any reactive power flow between the compensation and the transmitting coils, and to achieve input zero phase angle and constant current output. In addition, an efficient finite element analysis-based coil optimization algorithm is proposed to improve the coil misalignment tolerance on the horizontal plane, in which a reversely connected inner coil is used to stabilize the system output under misalignment conditions. Analytical and simulation results confirm transmission flux density enhancement and reduced leakage field characteristics of the proposed coil design. Finally, a scaled-down WPT prototype is built and tested to verify the performance and effectiveness of the design. The proposed design achieves 91.17% efficiency and misalignment tolerance up to 200 mm in any XY-direction while maintaining the power transfer and its efficiency. The results of this work provide insights into magnetic integration design of high-order compensation topologies featuring higher compactness, less ferrite usage, magnetic field enhancement, and misalignment tolerance for WPT systems.

Three-Port High Step-Up and High Step-Down DC-DC Converter With Zero Input Current Ripple

Abstract: In this article, a nonisolated three-port dc–dc converter with high voltage conversion ratio is proposed. In the proposed converter, by changing the place of input voltage source between each of the three ports, three different single-input two-output operation modes are achieved. The input current ripple of the proposed converter is eliminated at the low voltage side for the whole range of duty cycles. The voltage conversion ratios of the proposed converter can be increased by increasing the turns ratio of second winding of coupled inductors. Moreover, the proposed converter has achieved proper output voltage regulations for all output ports, simultaneously. The proposed converter can be utilized in the renewable energy conversion systems such as in photovoltaic and fuel cells. In this article, the voltage conversion ratios of the output ports, the voltage stress on switches, the average currents of switches and inductors, and the required condition for cancelling input current ripple at low voltage side are calculated theoretically. The theoretical results are verified and experimental results for 24 V input voltage and 304 V, 240 V output voltages with 400 W power are extracted for two different operation modes.

Switched Inductor Double Switch High Gain DC-DC Converter for Renewable Applications

Abstract: High voltage gain DC-DC converter is a prime requirement for renewable applications, in particular for PV. Though numerous DC-DC converter is available for increasing the voltage gain, the passive elements requirement is higher which reduces the compactness, consequently, increases the cost of the system. To address this issue, a high gain DC-DC converter is reported recently. However, the number of passive elements is quite high which increases the size. To reduce the number of passive elements and maintain the same number of semiconductor devices, in this paper, a new switched inductor arrangement is proposed which is named as switched inductor double switch DC-DC converter (SL-DS-DC). Moreover, the proposed converter has a higher gain as compared to the recently reported converter. The proposed converter is analyzed in steady state and a comparative analysis is presented to prove the suitability. Finally, the proposed converter is validated experimentally.

A Low-Cost Multiwinding Transformer Balancing Topology for Retired Series-Connected Battery String

Abstract: The traditional balance circuit is employed to balance the retired battery string. It will occupy some space for the extra switches, inductors, or/and capacitors of the energy storage system. This letter is trying to share the inductor of the dc–dc converter with the balance system by utilizing the current ripple on the inductor of the multiwinding transformer. The balance circuit does not require additional switches and control logic. The results of dynamic charging conditions show that the circuit is appropriate for balancing the battery string, and the system efficiency with the proposed approach reaches 94.1% at rated 28-W input power. The balance system only increases one diode and one inductor for each cell, which reduces the cost by 60% and 66% separately compared with the traditional resistance equalizer and transformer-based equalizer.

Power Coupling Mechanism Analysis and Improved Decoupling Control for Virtual Synchronous Generator

Abstract: A virtual synchronous generator (VSG) control-based grid-connected converter (GCC) is an attractive solution to improve the stability of a more renewable-energy-integrated power system. Unfortunately, the inherent power coupling (i.e., the interaction between the active power loop and the reactive power loop) defect of VSG control severely restricts the power delivery capacity and the grid support capability of the GCC. The virtual inductor is commonly used to reduce coupling, but its decoupling capability is very limited. In addition, the power coupling mechanism and its limiting factors are not clear. For this issue, the nature of power coupling in the VSG system is investigated first. The decoupling capability of the virtual inductor is studied, and the reason for decoupling effectiveness is revealed. It indicates that the effectiveness of decoupling results from the proper voltage compensation, but this kind of positive effect is limited by the d -axis voltage drop across the virtual inductor. Then, a q -axis voltage-drop-based power decoupling control (QVPDC) is proposed to further reduce the power coupling, which does not consider the d -axis voltage drop when applying the virtual inductor. Compared with the virtual-inductor-based decoupling method, the decoupling performance of QVPDC is better, and the computation burden is reduced by half. Finally, the analysis and the proposed method are validated by simulation and experiment.

Zero Voltage Switching Criteria of Triple Active Bridge Converter

Abstract: Triple active bridge (TAB) as an isolated multiport converter is a promising integrated energy system for smart grids or electric vehicles. This article aims to derive and analyze zero voltage switching (ZVS) regions of TAB, in which both switching losses are reduced, and electromagnetic interference issues are mitigated. In the proposed closed-form solution of ZVS criteria, parameters such as the parasitic capacitance of the switches, the leakage inductance of the transformer, the switching frequency, the port voltage, the phase-shift inside and between the full-bridges are all taken into account. The analysis shows how the five degrees of freedom can be used to maintain ZVS operation in various operating points. The analysis and derived closed-form ZVS criteria are experimentally verified using a laboratory prototype. The derived analytical ZVS criteria are a powerful tool to study and optimize the operation of TAB converters.

Review of High-Frequency High-Voltage-Conversion-Ratio DC–DC Converters

Abstract: The development of high-frequency power converters is continuously improving their power density, efficiency and fast dynamic response. Among them, high-voltage-conversion-ratio (HVCR) dc–dc converters are widely used in high gain, i.e., step-up/-down or bidirectional applications, such as power supply for data center, dc micro-grids, electrical vehicle charging systems, etc. In this article, the current main high-frequency HVCR dc–dc converters are classified into inductive-based and capacitive-based approaches, which can then be described further by four kinds in detail, namely transformer-based, coupled-inductor-based, and switched-capacitor-based, as well as combination of coupled inductor and switched capacitor. A comprehensive analysis and comparison is given, which can provide guidance for proper topology selection and further topology optimization.

A Soft-Switching Current-Source-Inverter-Fed Motor Drive With Reduced Common-Mode Voltage

Abstract: This article proposes a common-mode voltage (CMV) attenuation method for the three-phase current source inverter (CSI)-fed permanent-magnet synchronous machine drive. The key of this method is to introduce an auxiliary circuit branch connected in parallel with the dc link. Based on the dedicated switching strategy, the zero-voltage-switching conditions are provided for the main switches in the CSI. In particular, the zero current vector is newly constructed without utilizing shoot-through operation in the CSI. Thus, the CMV in the traditional CSI drives is attenuated significantly. Compared with the existing research on CMV suppression, the proposed method will not compromise the modulation index range or increase output current harmonics. Meanwhile, the overshoot voltage can be clamped by the auxiliary power circuit in the dc link under open-circuit fault in the power switches. The system configuration, operating principle, analysis of operation modes, as well as the control scheme are described in detail. Both simulation and experimental results are presented to verify the performance of the proposed method.

99% Efficient 2.5-kW Four-Level Flying Capacitor Multilevel GaN Totem-Pole PFC

Abstract: In this article, a high-efficiency and high-density 2.5 kW four-level flying capacitor multilevel (FCML) totem-pole bridgeless power-factor-correction (PFC) rectifier with 200 V GaN devices is analyzed, designed, and tested. This 2.5 kW four-level continuous conduction mode (CCM) GaN totem pole PFC operates with 360 kHz current ripple frequency which significantly reduces the inductor size while keeping a very low switching loss. This article compares the device loss of the four-level and two-level CCM GaN totem-pole PFC with the same ripple frequency (360 kHz) and shows that the four-level CCM GaN PFC has much less device loss. In addition, this article introduces the detailed design of a compact and low-profile matrix inductor based on the commercial composite inductors. This article also introduces the design of a high-density and low-loss flying capacitor. A 2.5 kW four-level FCML GaN totem-pole PFC prototype with 120 kHz switching frequency (360 kHz current ripple frequency) is developed and tested in this article. The tested peak efficiency is 99.25%. The PFC system power density is 104 W/in3, without a heatsink and with forced air cooling.

New Semiquadratic High Step-Up DC/DC Converter for Renewable Energy Applications

Abstract: In this article, a new semiquadratic high step-up coupled-inductor dc/dc converter (SQHSUCI) with continuous input current and low voltage stress on semiconductor components is presented. The proposed structure employs a coupled-inductor (CI) and two power switches with simultaneous operation to achieve an extremely high voltage conversion ratio in a semiquadratic form. The voltage stress across the main power switch is clamped by two regenerative clamp capacitors. Here, the switching losses of both MOSFET s have been reduced by applying quasi-resonance operation of the circuit created by the leakage inductance of the CI along with the balancing and clamp capacitors. Therefore, by considering the high gain conversion ratio along with low voltage stress on components, the magnetic and semiconductors losses of the SQHSUCI are reduced significantly. Also, the energy stored in the leakage inductance of CI is recycled to the output capacitor. These features make the proposed SQHSUCI more suitable for industrial applications. The operation principle, steady state, and also comparisons with other related converters in continuous conduction mode (CCM) are discussed in detail. Finally, experimental results of a prototype with 20 V input and 200 W–200 V output at 50 kHz switching frequency, verify the theoretical advantages of the proposed strategy.

Design, Control, and Analysis of a Novel Grid-Interfaced Switched-Boost Dual T-Type Five-Level Inverter With Common-Ground Concept

Abstract: Multilevel inverters with a common-ground structure and voltage step-up feature are beneficial for transformerless grid-connected photovoltaic applications. In this article, a novel topology of such converters with a five-level output voltage generation is presented. The proposed topology comprises of an integrated switched-boost (SB) module and a dual T-type (D2T) cell constructed with 10 power switches (six unidirectional and two bidirectional). An inductor in the integrated SB module is used to boost the voltage across two involved capacitors of the D2T cell. Therefore, a desirable ac voltage magnitude for the grid-connected application can be achieved over a wide range of input voltage changes. Current stress is also kept within a permissible input current range by the soft-charging operation of the involved capacitors through the inductor. A corresponding dead-beat continuous-current-control-set controller with a sinusoidal PWM modulator is implemented for controlling the real and reactive powers. The controller has an added benefit of achieving constant switching frequency for power switches. Circuit description, theoretical analyses, and comparative study are discussed. Simulation and experimental results are also presented to confirm the feasibility and correctness of the proposed topology.

Multiphase Interleaved Bidirectional DC/DC Converter With Coupled Inductor for Electrified-Vehicle Applications

Abstract: A nonisolated high-power-density bidirectional dc/dc converter named multiphase interleaved with a coupled inductor is described. The proposed converter allows low current and voltage ripple, lower power losses, reduction on power component stress, and magnetic volume. Moreover, the coupled inductor is applied to achieve current sharing between each leg in a simple manner, which is helpful to simplify the structure and meaningfully improve performance. Auxiliary clamp circuits are not required and can operate over a wide voltage and power range, achieve a better dynamic response and low ripple while maintaining high efficiency. This article illustrates the steady-state operating principle under the inductor current continuous, discontinuous conduction modes and their boundary conditions in detail, the voltage and current stress of the power devices are shown, parameter design guideline, mathematical derivations, and a comparison between the proposed converter and previous dc/dc converters were conducted. Finally, a 4.5-kW proof-of-concept laboratory prototype has been designed, developed, and tested to demonstrate the performance of the proposed converter for wide load variation. The measured efficiency for the rated load was over 98% for maximum input voltage. This article is accompanied by a video file demonstrating the operation of the converter.

Physics-Based Modeling of Parasitic Capacitance in Medium-Voltage Filter Inductors

Abstract: This article proposes a general physics-based model for identifying the parasitic capacitance in medium-voltage (MV) filter inductors, which can provide analytical calculations without using empirical equations and is not restricted by the geometrical structures of inductors The elementary capacitances of the MV inductor are identified, then the equivalent capacitances between the two terminals of the inductor are derived under different voltage potential on the core Further, a three-terminal equivalent circuit, instead of the conventional two-terminal equivalent circuit, is proposed by using the derived capacitances Thus, the parasitic equivalent capacitance between the terminals and the core are explicitly quantified Experimental measurements for parasitic capacitances show a good agreement with the theoretical calculations

Ultrahigh Step-Up DC-DC Converter Composed of Two Stages Boost Converter, Coupled Inductor and Multiplier Cell

Abstract: In this paper, an ultrahigh step-up DC-DC converter is proposed with combination of a quadratic boost converter, a coupled inductor and a multiplier cell which doubles output voltage. Secondary side of the coupled inductor is unified with the multiplier cell. In addition, leakage energy of the coupled inductor is recycled and transferred to output perfectly which causes high efficiency performance. Main advantages of the converter include its high voltage gain, low voltage stress on its semiconductors and requiring smaller inductor in low voltage side of the converter. Power losses of the inductors are low due to current sharing between the input inductor and the coupled inductor. Continuity of input current and existence of a common ground between the load and source make the converter suitable for different applications. The converter is compared with the other converters based on analysis of its operation modes. Validity of the analysis and the converter performance are experimented using a 150W prototype that converters 20V from input side to 400V in output.

Response regimes of nonlinear energy harvesters with a resistor-inductor resonant circuit by complexification-averaging method

Abstract: In this paper, the steady-state response regimes of nonlinear energy harvesters with a resistor-inductor resonant circuit are theoretically investigated. The complexification averaging (CA) method is used to theoretically analyze the energy harvesting performance and reduce the motion equations into a set of first-order differential equations. The amplitudes and phases of both the response displacement and the output voltage are derived, and the corresponding stability conditions are determined. The response regimes are studied with the variation of nonlinear stiffness coefficients and coupling parameters, which are verified by the time domain analysis. The frequency island phenomenon is found and analyzed. Additionally, the backbone curve for deducing the extreme vibration frequency and amplitude is derived. Simultaneously, the analytical expressions of the switching points (critical amplitude and frequency) to identify the hardening and softening properties are established. Accordingly, a criterion is given to determine the occurrence of the jump phenomenon, and its effectiveness is verified. Overall, this paper presents an in-depth theoretical analysis of nonlinear energy harvesters with a resistor-inductor resonant circuit. It presents the theoretical framework and guidance for more extensive evaluations and understanding the theoretical analysis of nonlinear energy harvesters with external circuits.

Soft-Switched Single Inductor Single Stage Multiport Bidirectional Power Converter for Hybrid Energy Systems

Abstract: A soft-switched nonisolated multiport bidirectional converter is proposed for hybrid energy system applications. The proposed topology improves the efficiency and expands the applications of the conventional three-port converter (TPC) by adding a soft-switching cell and a bidirectional power flow path from output to charge the energy storage device. Moreover, soft-switching conditions for all TPC switches in all operating modes are achieved. The topology uses one inductor that is shared by all power flow paths. Thus, power conversion in all operating modes is done in a single-stage and the conduction loss is reduced. To implement the soft-switching cell, coupled inductors are used to optimize the magnetic core and volume of the converter. Various converter operating modes are presented, and design considerations are discussed. Moreover, different control system operating modes are explained and designed in detail. Finally, a converter prototype to supply a 250 W–200 V load is implemented, and the theoretical analysis is validated by the experimental results.

Steady-State and Transient DC Magnetic Flux Bias Suppression Methods for a Dual Active Bridge Converter

Abstract: This article presents dc magnetic flux bias suppression methods for a dual active bridge (DAB) converter in both steady state and transient process. The steady-state dc offset is caused by asymmetries of the circuit and power switches in practice, while the transient offset is caused by the sudden update of phase shift ratio. This dc bias will increase the conduction losses, lead to loss of zero voltage switching (ZVS), and even saturate the magnetic components. To prevent this risk, this article proposes methods to suppress the dc bias both in steady state and transient process. For steady-state dc bias suppression, the duty cycles of square voltages generated by the primary and secondary side H-bridges are regulated according to the dc bias current. The conditions to achieve zero dc bias and the small-signal model to regulate the dc bias current are derived. For transient dc bias suppression, the phase shift ratio variation is limited to ensure the peak inductor current within the safe operating range. Tunnel magnetoresistance (TMR) is employed to sense the currents, and an analog integration and sampling method is proposed to detect dc bias. Finally, the proposed method is verified through experimental results on a 3200-W DAB prototype.

Five-Degree-of-Freedom Modulation Scheme for Dual Active Bridge DC–DC Converter

Abstract: A five-degree-of-freedom (5-DOF) modulation scheme is proposed in this article for dual active bridge converter to improve its efficiency in a wide operation range. First, the possible operation modes of the converter under the 5-DOF is analyzed. As a result, 11 effective modes are obtained and their steady-state characteristics expressions are solved, including the inductor root-mean-square (rms) current, inductor peak-to-peak current, and transmission power, etc. It is worth mentioning that the inductor peak-to-peak current expression is simple and it can be regarded as an indicator for rms current. Thus, the peak-to-peak current is treated as the objective to obtain the optimal solutions of each mode, and the global minimum peak-to-peak (GMPP) modulation scheme is obtained. However, there are only two switches that can realize soft-switching operation in the low-power range under GMPP, which results in significant switching loss. Therefore, to further expand the soft-switching operation range in the low-power range, the soft-switching conditions are also taken into consideration, and an optimized five-degree-of-freedom (O5-DOF) modulation scheme is proposed. With the proposed O5-DOF, almost all switches can realize soft-switching operation during the whole load range, and the inductor rms current is minimized simultaneously. Finally, the experimental results are presented to validate the theoretical analysis and effectiveness of the proposed modulation scheme.

An Improved Boost-Based dc/dc Converter With High-Voltage Step-Up Ratio for DC Microgrids

Abstract: In this article, an improved ripple-free input current boost-based high step-up (HSU) dc/dc converter compared to the coupled inductor (CI) ones is proposed, where the large CI is replaced by an inductor and a built-in transformer. By doing so, the energy is transferred to the output by two smaller magnetic components. Hence, a more compact and more efficient coupled magnetic component with greater flexibility in increasing its turns ratio is succeeded, allowing us to achieve higher dc voltage gains (higher than 20). Additionally, an active clamp is employed to recycle the leakage energy of the transformer, eliminating at the same time the switching losses. Therefore, by increasing the switching frequency it is feasible to build a highly efficient, reduced-size HSU converter that can be integrated along with a low maximum power point voltage photovoltaic module for dc microgrid applications. Finally, a 250-W-rated prototype has been implemented to verify the functionality of the presented converter in continuous conduction mode operation with an input voltage range of 16–20 V and an output voltage of 400 V.

High-Gain Bidirectional Quadratic DC–DC Converter Based on Coupled Inductor With Current Ripple Reduction Capability

Abstract: In this article, a high-gain bidirectional quadratic dc–dc converter is proposed. This converter is studied under step-up and step-down modes. In each power flow direction, two switches and two antiparallel diodes of the other switches operate. Therefore, the switching losses depend only on the operation of two switches in each direction. The use of coupled inductor in the proposed converter significantly reduces the input and output current ripples of the step-up and step-down modes, respectively, at all operating points of continuous and discontinuous conduction modes (CCM and DCM). The voltage gain of the proposed converter in the step-up mode is as high as that of the cascaded boost converter, and in the step-down mode, the converter voltage gain is similar to that of the cascaded buck converter. Thus, the high-voltage conversion ratio with an appropriate duty-cycle in both power flow directions can be achieved. The operating principles and steady-state analysis of the proposed converter in CCM, DCM, and the boundary-conditions between these modes are discussed in detail. Finally, a prototype of the converter is implemented in the laboratory and the experimental results are presented to validate the effectiveness of the proposed converter.

A Novel Interleaved Parallel Bidirectional Dual-Active-Bridge DC–DC Converter With Coupled Inductor for More-Electric Aircraft

Abstract: Although conventional dual-active-bridge (DAB) dc–dc converters have been applied in more-electric aircraft, the maximum transmission power of conventional DAB converters is still limited by its structure. In order to increase the maximum transmission power, this article proposes a novel interleaved parallel bidirectional DAB converter. Two bidirectional buck/boost converters are applied in low-voltage side of the proposed converter. So the voltage of transformer primary side would not be limited by the voltage of low-voltage bus and can be controlled by the duty cycle according to the modulation strategies. In this article, three phase-shift control methods are used for the proposed topology. From the analysis of operation modes and power characteristics of the proposed topology, compared with the single phase-shift (SPS), the extended phase shift can reduce the reactive power and current stress. The pulsewidth modulation (PWM) plus single phase-shift (PWMSPS) can achieve more than twice of the maximum transmission power of conventional DAB converter. Finally, test results verify the theoretical analysis and the validity of the proposed converter.