Voltage Gain Range Research Articles

A PWM LLC Type Resonant Converter Adapted to Wide Output Range in PEV Charging Applications

In conventional LLC-based plug-in electric vehicle (PEV) onboard chargers, the battery pack voltage varies in a wide range with the change of state of charge. This makes it difficult to optimally design the pulse frequency modulated LLC resonant converter. Besides, the voltage regulation of the LLC converter is highly dependent on the load conditions. In this paper, a modified pulse width modulated (PWM) LLC type resonant topology (PWM-LLC) is proposed and investigated in PEV charging applications. The switching frequency of the primary LLC network is constant and equal to the resonant frequency. The voltage regulation is achieved by modulating the duty cycle of the secondary side auxiliary mosfet . Compared with the conventional LLC topology, the proposed topology shrinks the magnetic component size and achieves a wide and fixed voltage gain range independent of load conditions. Meanwhile, zero-voltage-switching and zero-current-switching are realized among all MOSFETs and diodes, respectively. A 100-kHz, 1-kW converter prototype, generating 250–420 V output from the 390-V dc link, is designed and tested to verify the proof of concept. The prototype demonstrates 96.7% peak efficiency and robust performance over wide voltage and load ranges.

Interleaved Switched-Capacitor Bidirectional DC-DC Converter With Wide Voltage-Gain Range for Energy Storage Systems

In this paper, an interleaved switched-capacitor bidirectional dc-dc converter with a high step-up/step-down voltage gain is proposed. The interleaved structure is adopted in the low-voltage side of this converter to reduce the ripple of the current through the low-voltage side, and the series-connected structure is adopted in the high-voltage side to achieve the high step-up/step-down voltage gain. In addition, the bidirectional synchronous rectification operations are carried out without requiring any extra hardware, and the efficiency of the converter is improved. Furthermore, the operating principles, voltage and current stresses, and current ripple characteristics of the converter are analyzed. Finally, a 1 kW prototype has been developed which verifies a wide voltage-gain range of this converter between the variable low-voltage side (50–120 V) and the constant high-voltage side (400 V). The maximum efficiency of the converter is 95.21% in the step-up mode and 95.30% in the step-down mode. The experimental results also validate the feasibility and the effectiveness of the proposed topology.

An Enhanced Hybrid Switching-Frequency Modulation Strategy for Fuel Cell Vehicle Three-Level DC-DC Converters with Quasi-Z Source

For fuel cell vehicles, the fuel cell stack has a soft output characteristic whereby the output voltage drops quickly with the increasing output current. In order to interface the dynamic low voltage of the fuel cell stack with the required constant high voltage (400 V) of the inverter DC link bus for fuel cell vehicles, an enhanced hybrid switching-frequency modulation strategy that can improve the voltage-gain range is proposed in this paper for the boost three-level DC-DC converter with a quasi-Z source (BTL-qZ) employed in fuel-cell vehicles. The proposed modulation strategy retains the same advantages of the original modulation strategy with more suitable duty cycles [1/3, 2/3) which avoids extreme duty cycles. Finally, the experimental results validate the feasibility of the proposed modulation strategy and the correctness of its operating principles. Therefore, the BTL-qZ converter is beneficial to interface the fuel cell stack and the DC bus for fuel cell vehicles by using the proposed modulation strategy.

A Bidirectional Resonant DC–DC Converter Suitable for Wide Voltage Gain Range

This paper proposes a new bidirectional resonant dc-dc converter suitable for wide voltage gain range applications (e.g., energy storage systems). The proposed converter overcomes the narrow voltage gain range of conventional resonant dc-dc converters, and meanwhile achieves high efficiency throughout the wide range of operation voltage. It is achieved by configuring a full-bridge mode and a half-bridge mode operation during each switching cycle. A fixed-frequency phase-shift control scheme is proposed and the normalized voltage gain can be always from 0.5 to 1, regardless of the load. The transformer root-mean-square (rms) currents in both the forward and reverse power flow directions have a small variation with respect to the voltage gain, which is beneficial to the conduction losses reduction throughout a wide voltage range. Moreover, the power devices are soft-switched for minimum switching losses. The operation principles and characteristics of the proposed converter are firstly analyzed in this paper. Then the analytical solutions for the voltage gain, soft-switching, and rms currents are derived, which facilitates the parameters design and optimization. Finally, the proposed topology and analysis are verified with experimental results obtained from a 1-kW converter prototype.

Hybrid Bidirectional DC–DC Converter With Low Component Counts

In this paper, a hybrid bidirectional dc–dc converter is presented, which is a combination of a switched-capacitor converter and an inductor-based converter with low component counts. The input current ripple and peak charging current are small with the help of the inductor. The proposed converter is applicable in the battery charge/discharge systems, such as the distributed renewable energy systems, battery equalizer, auxiliary power supplies, traction drive system, and dual-voltage automotive systems based in new electrical architecture concept, where common ground is not required and within the voltage-gain range of 2–6. A comprehensive analysis of the steady-state operation, small-signal model, and component stress is given. The comparison with an alternative topology shows the advantages of low component counts, low total capacitor voltage stress, low inductor current, and low total active switch stress for the 42/14 V voltage level. A 42/14 V prototype rated at 20–120 W with a peak efficiency of 97.8% in boost mode and 97.62% in buck mode was built to verify the analysis.

A Wide Voltage-Gain Range Asymmetric H-Bridge Bidirectional DC-DC Converter with a Common Ground for Energy Storage Systems

A wide-voltage-conversion range bidirectional DC-DC converter is proposed in this paper. The topology is comprised of one typical LC energy storage component and the special common grounded asymmetric H-bridge with four active power switches/anti-parallel diodes. The narrow output PWM voltage is generated from the voltage difference between two normal (wider) output PWM voltages from the asymmetric H-bridge with duty cycles close to 0.5. The equivalent switching frequency of the output PWM voltage is double the actual switching frequency, and a wide step-down/step-up ratio range is achieved. A 300W prototype has been constructed to validate the feasibility and effectiveness of the proposed bidirectional converter between the variable low voltage side (24V~48V) and the constant high voltage side (200V). The slave active power switches allow ZVS turn-on and turn-off without requiring any extra hardware, and the maximum conversion efficiency is 94.7% in the step-down mode and 93.5% in the step-up mode. Therefore, the proposed bidirectional topology with a common ground is suitable for energy storage systems for example for renewable power generation systems or electric vehicles with a hybrid energy source.

An Improved PWM Strategy for Z-Source Inverter With Maximum Boost Capability and Minimum Switching Frequency

Z-source inverter provides a competitive single-stage dc–ac power conversion with the capability of both buck and boost voltage regulation. In order to maximize voltage gain and to increase efficiency, this paper proposes an improved pulse-width modulation (PWM) strategy. By adjusting the shoot-through duty ratio of one-phase leg, it regulates the average value of intermediate dc-link voltage, which is the same as the instantaneous maximum of three-phase line voltage in one switching time period $(T_{s})$ . And the other two-phase legs maintain the fixed switching states. Thus, the equivalent switching frequency of power devices in the inverter bridge is reduced to $1/ 3f_{s}$ ( $f_{s}$ is the frequency corresponding to $T_{s}$ ). The operating principles and closed-loop controller design are analyzed and verified by simulation and experiments. Compared with the existing PWM strategies, the improved PWM (IPWM) strategy demonstrates higher efficiency under full operation range of low voltage gain (1.27-2) application. However, with the IPWM strategy, the inductor current and capacitor voltage contain six-time-line-frequency ripples, which consequently require large size of the passive components when the output frequency is very low. Thus, it is also suitable for 400–800-Hz medium frequency aircraft and vessel power supply system due to a relatively high output line frequency. Furthermore, the idea of IPWM strategy can be extended to other kinds of three-phase impedance network-based inverters.

Frequency Domain Analysis and Optimal Design of Isolated Bidirectional Series Resonant Converter

This paper presents an optimal design approach for a dual-active-bridge series resonant converter (DABSRC) based on frequency domain analysis. The proposed design technique ensures efficient performance of DABSRC over a wide range of voltage gain and load variations. The operating principle of the converter is detailed to illustrate both zero voltage switching (ZVS) and zero current switching operations during bidirectional power transfer. Modeling the current-dependent power loss components as an equivalent series resistance, the converter is analyzed in frequency domain to derive amplitude and phase of the state variables accurately. Performing the power loss analysis in a normalized form, the characteristic equations for bidirectional power transfer, tank current, converter efficiency, and ZVS criteria are derived. Using these characteristics, the design of DABSRC is formulated as an efficiency optimization problem. Particle swarm optimization technique is adopted to determine the optimal tank parameters and transformer turns-ratio. Converter performance is evaluated on a 120-W lab-prototype, and peak efficiency of 95.2% and California energy commission efficiency of 92.1% are achieved. Close agreement among analytical predictions, numerical simulation, and experimental results validate the proposed design technique.

A Novel D-CLT Multi-Resonant DC-DC Converter with Reduced Voltage Stresses for Wide Frequency Variation Applications

In this paper, a dual-capacitor-inductor-transformer (CLT) (D-CLT) soft-switching dc–dc converter has been proposed. Combining the multiresonant technology, the converter employs two high-frequency transformers in the resonant tank and exhibits desirable characteristics. The fundamental and the third-order harmonics can be utilized to transfer active power simultaneously. The share of third harmonic is larger than first component. Thus, the converter can use the 100-kHz controlling signals to mainly transfer the 300-kHz active power, which makes it easier to realize high power density. Moreover, the available range for the third power delivery is expanded as well. A resonant zero point is introduced into the voltage gain curves. It ensures broadened voltage gain range (from zero to the maximum) and good protection for overcurrent issue. Then, improved soft-switching performances have been achieved: All the switches achieve the zero-voltage-switching (ZVS) turn- on , whereas all the diodes obtain the zero-current-switching (ZCS) turn- on and quasi-ZCS turn- off . Switching losses are constrained to the minimum. To verify the feasibility of the proposed converter, a 330-W prototype is established and tested. The results demonstrate the experiments match well with the theoretical analyses. The peak efficiency has reached 95.2%, although a high-loss diode bridge is adopted.

Single-Switch, Wide Voltage-Gain Range, Boost DC–DC Converter for Fuel Cell Vehicles

In order to match voltages between the fuel cell stacks and the DC link bus of fuel cell vehicles, a single-switch Boost dc–dc converter with diode-capacitor modules is proposed in this paper. The capacitors are charged in parallel and discharged in series. The wide voltage-gain range can be obtained by using a simple structure. In addition, the basic operating principles, the extended stages, the fault tolerant operation, and steady-state characteristics of the converter are analyzed and presented in this paper, and the small-signal model is also derived. A 400 V, 1.6 kW experimental prototype is developed, and the wide voltage-gain range (3.3 ∼ 8) is demonstrated with a maximum efficiency at 97.25%. The experimental results validate the effectiveness and feasibility of the proposed converter and its suitability as a power interface for fuel cell vehicles.

A Family of Resonant Two-Switch Boosting Switched-Capacitor Converter With ZVS Operation and a Wide Line Regulation Range

In this paper, a family of resonant two-switch boosting switched-capacitor converters (RTBSCs) with ZVS operation and a wide line regulation range is proposed. Based on our previously proposed two-switch boosting switched-capacitor converters (TBSCs), only a small resonant inductor is added, while two bulky capacitor banks are replaced by two much smaller resonant capacitors. Furthermore, by operating RTBSC above the resonant frequency, the transistors are ZVS turned on and diodes are Zero-current-switching (ZCS) turned on / off . This eliminates the hard-switched phenomenon of TBSC, leading to reduced component size by increasing the operating frequency without sacrificing the overall efficiency. In addition, the voltage-gain range of the RTBSCs is largely expanded and hence the input-voltage range is increased remarkably for regulated output voltage applications. Meantime, the voltage stress on transistors and diodes remains low, equal to the input voltage. A 3X RTBSC prototype with maximum output voltage 150 V, maximum output power 140 W, and a peak efficiency of 98.3% was built. The analysis is verified by simulation and experimental results.

A Frequency Adaptive Phase Shift Modulation Control Based LLC Series Resonant Converter for Wide Input Voltage Applications

This paper presents an isolated LLC series resonant DC/DC converter with novel frequency adaptive phase shift modulation control, which suitable for wide input voltage (200–400 V) applications. The proposed topology integrates two half-bridge in series on the primary side to reduce the switching stress to half of the input voltage. Unlike the conventional converter, this control strategy increases the voltage gain range with zero-voltage-switching (ZVS) to all switches under all operating voltage and load variations. Adaptive frequency control is used to secure ZVS in the primary bridge with regards to load change. To do so, the voltage gain becomes independent of the loaded quality factor. In addition, the phase shift control is used to regulate the output voltage as constant under all possible inputs. The control of these two variables also significantly minimizes the circulating current, especially from the low-voltage side, which increases the efficiency as compared to a conventional converter. Experimental results of a 1-Kw prototype converter with 200–400-V input and 48-V output are presented to verify all theoretical analysis and characteristics.

Input-Parallel Output-Series DC-DC Boost Converter With a Wide Input Voltage Range, For Fuel Cell Vehicles

An input-parallel, output-series dc–dc Boost converter with a wide input voltage range is proposed in this paper. An interleaved structure is adopted in the input side of this converter to reduce input current ripple. Two capacitors are connected in series on the output side to achieve a high voltage gain. The operating principles and steady-state characteristics of the converter are presented and analyzed in this paper. A 400 V/1.6 kW prototype has been created which demonstrates that a wide range of voltage gain can be achieved by this converter and it is shown that the maximum efficiency of the converter is 96.62% and minimum efficiency is 94.14%. The experimental results validate the feasibility of the proposed topology and its suitability for fuel cell vehicles.

Small Scale Wind Generation System: Part I – Experimental Verification Of Flux Reversal Generator Block

<p>This research work, titled Small Scale Wind Generation System, reported in part I and part II, proposes modeling, analysis and control of a small scale wind energy conversion system employing a direct driven Flux Reversal Generator (FRG) connected to the micro grid through a Quasi-Z-Source Inverter (QZSI). The application of QZSI using FRG to feed micro grid is proposed for the first time in this research work. The QZSI can realize buck/boost, inversion and power conditioning in a single stage with improved reliability. Also it features a wide range of voltage gain which is suitable for applications in wind systems, due to the fact that the wind generator output varies widely with wind velocity. In addition, the modified Space Vector PWM (SVPWM) technique is proposed in this paper to satisfy the shoot-through characteristic of QZSI. This also adds to the contribution of this research work. In this part I of this full research, modelling of the small scale FRG for wind system using Finite Element Analysis (FEA) is presented. The major parameter of FRG viz, voltage, current, torque and power are analyzed, validated and then represented in d-q model. The simulation results are validated with the analytical results. An experimental set-up to run the full procedure reported in this paper. These results form the basis for part II of this research work.</p>

Design and Analysis of a High-Voltage-Gain Step-Up Resonant DC–DC Converter for Transportation Applications

Conventional power take-off (PTO) system in the automotive applications has shown some disadvantages such as low efficiency and high fuel consumption. Electrification for PTO system used in specialty vehicles requires the application of high-gain step-up dc-dc converter. A new candidate topology for high-voltage-gain step-up dc-dc converter using resonant technology has been proposed in this paper. In addition to its high voltage gain and wide input range, it also brings the benefits of low input current ripple, reducing current stress in switching devices and transformer, ZVS in two power MOSFETs, and ZCS in the rectifier diode operation over the full load range and high efficiency. Interleaved step-up topology helps the circuit to reduce the stress on the components, while it also decreases the transformer requirements. Series resonant tank is used to achieve ZVS and ZCS as well as extended voltage control. Detailed design analysis shows the impact of the transformer turns-ratio and resonant tank to the other circuit components. The input current ripple is also determined by the operating duty range. A 2-kW prototype has been built according to the design rules. The experimental results are used to verify the circuit operation and design analysis. A peak efficiency of 95.5% has been achieved for the prototype, and it shows an efficiency improvement compared with several other topologies.

Modified impedance source inverter for power conditioning system

Based on classical impedance source inverter concept, this paper presents a modified impedance source inverter controlled by different pulse width modulation control strategies for solar PV/battery-powered applications. A brief topology analysis, generalized discussion and design of impedance network elements are presented. Comparison with the classical impedance source inverter is presented. Using simulation, analytical results are presented that ensure stability. The proposed voltage type inverter has reduced inrush current at startup, less capacitor voltage stress and minimum inductor current ripples. DC link voltage boost, reduced total harmonic distortion of output current and voltage, better voltage gain and wide range of output voltage control can be achieved easily with improved power quality. Experimental set-up of the modified impedance source inverter with Field Programmable Gate Array (FPGA) controller has been constructed to ascertain the results.

Dual-Bridge LLC Resonant Converter With Fixed-Frequency PWM Control for Wide Input Applications

This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency pulsewidth-modulated (PWM) control is employed and a range of twice the minimum input voltage can be covered. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor, and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the design of magnetic components as well. Over the full load range, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter is presented along with the converter performance. Finally, all theoretical analysis and characteristics are verified by experimental results from a 120-V to 240-V input 24 V/20 A output converter prototype.

Model Predictive Control of Quasi-Z-Source Four-Leg Inverter

This paper presents a model predictive control (MPC) scheme for quasi-Z-source (qZS) three-phase four-leg inverter. In order to cope with the drawbacks of traditional voltage source inverters (VSIs), a qZS three-phase four-leg inverter topology is proposed. This topology features a wide range of voltage gain which is suitable for applications in renewable energy-based power systems, where the output of the renewable energy sources varies widely with operating conditions such as wind speed, temperature, and solar irradiation. To improve the capability of the controller, an MPC scheme is used which implements a discrete-time model of the system. The controller handles each phase current independently, which adds flexibility to the system. Simulation and experimental studies verify the performances of the proposed control strategy under balanced and unbalanced load conditions as well as single-phase open-circuit fault condition.

A Bidirectional Three-Level LLC Resonant Converter With PWAM Control

This paper proposes a bidirectional three-level LLC resonant converter with a new pulse width and amplitude modulation control method. With different control signals, it has three different operation modes with different voltage gains. Therefore, it can achieve wide voltage gain range by switching among these three modes, which is attractive for energy storage system applications needing wide voltage variation. The proposed topology operates with constant switching frequency, which is easy to implement with digital control, and it can achieve soft switching for all the switches and diodes in the circuit as a conventional LLC resonant converter. The performance of the proposed converter is validated by the experimental results from a 1-kW prototype with 20 A maximum output current.

Wideband dual‐mode complementary metal–oxide–semiconductor receiver

A dual-mode complementary metal–oxide–semiconductor (CMOS) receiver operating from 1 to 2 GHz is presented. The proposed receiver employs a switchable low-noise amplifier (LNA) and two separated down-conversion paths to realise dual-mode operation. For receiving weak signals without large blockers, the receiver works in the high-gain mode which adopts the common gate (CG)–common source (CS) LNA and the active-mixer-based down-conversion path to achieve high gain and low noise figure (NF). In the case of large in-band blockers, the receiver works in the high linearity mode, which uses the LNA as a low-noise transimpedance amplifier followed by a 25% duty-cycle current-driving passive mixer and a transimpedance amplifier based on current buffer to obtain high in-band linearity. Implemented in a 0.18 μm CMOS technology, this receiver achieves 4.9 dB NF and a voltage gain range of 29.4–92.6 dB in high-gain mode, whereas +0.9 dBm in-band input-referred third-order interception and a voltage gain range of 15.8–20.1 dB in high linearity mode.