Wide Voltage Operation Research Articles

High‐Voltage Operation of All‐Oxide Solid‐State Sodium Batteries Using NASICON‐Related Materials

AbstractAll‐oxide solid‐state sodium batteries (AOSSSBs), which are composed of oxide electrolytes and oxide active materials with sodium‐ion carriers, have attracted attention because of their high safety and material abundance. However, the operating voltage of AOSSSBs is inevitably low because the number of active materials available for use in AOSSSBs is restricted by undesirable reactions at electrolyte/electrode interfaces during high‐temperature fabrication. Herein, we fabricate AOSSSBs using a Na superionic conductor‐type solid electrolyte Na3Zr2(SiO4)2(PO4) (NZSP), a Na superionic conductor‐type negative active material NaTi2(PO4)3, and a mixed‐phosphate cathode active material Na4Ni3(PO4)2(P2O7) by a Na2B4O7 ⋅ 10H2O‐assisted low‐temperature fabrication technique. The obtained NaTi2(PO4)3/NZSP/Na4Ni3(PO4)2(P2O7) batteries exhibit an average discharge voltage of 3.1 V, which is the highest voltage ever reported in AOSSSBs. In addition, Na2B4O7 ⋅ 10H2O‐containing NZSP electrolytes show a wider electrochemical window in comparison with the pristine NZSP, enabling the batteries to endure a wide voltage operation (a capacity retention of 71 % after 10 cycles of charge/discharge in 0–5.1 V).

A new modulation strategy on isolated battery charger with wide input and output voltage range

AbstractA new wide voltage operation range isolated battery charger, which is composed of an asymmetric T‐type AC–DC power rectifier and a modified re‐configurable half bridge DC–DC power converter, is proposed in this paper. The asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages for increasing power conversion efficiency. As the isolated DC–DC power stage, a modified re‐configurable half bridge converter applies a three‐winding transformer to achieve a wide output operation range. The proposed battery charger operates over a wide AC input voltage range and wide DC output voltage range. A 3.2 kW hardware battery charger prototype is built to adapt AC voltage between 85 and 265 V. Both constant current and constant voltage modes are implemented experimentally to charge the battery up to 6.5 A from 50 to 500 V. The experimental results prove that the proposed asymmetric T‐type rectifier adopts different modulation strategies under different AC bus voltage amplitudes and different battery voltages can increase the power conversion efficiency, the proposed DC–DC converter can output the DC voltage from 50 to 500 V and the proposed battery charger can achieve around 94% efficiency.

Analysis and Verification of a Half-Dual Bridge Resonant Converter with Voltage Match Modulation

To overcome the weakness of the narrow conversion gain of dual bridge resonant converter, a half-dual bridge resonant converter (H-DBRC) with voltage match modulation (VMM) is proposed and implemented for wide voltage range applications. The H-DBRC, including a full bridge on the primary side and a half bridge on the secondary side, is adopted to realize the bidirectional power flow and wide voltage operation. Owing to the synergy between the H-DBRC structure and VMM strategy, the converter can operate in full-bridge state and half-bridge state with maximized ZVS (zero-voltage switching) operation and minimized circulating current. The steady-state analysis is performed and the solutions for both forward and backward modes could be obtained uniformly by using the fundamental harmonics approximation approach. The soft-switching characteristics, implementation process and design example are analyzed in detail. Finally, to confirm the theoretical analysis and feasibility, both simulation and experimental verifications are demonstrated in this paper. Since the converter consistently achieves voltage-matching operation, the optimal ZVS range can be obtained when the voltage gain M is between 0.5 to 1. Moreover, the economic cost and control complexity are greatly reduced because only six switches are required in the converter.

A Composite DC-DC Converter Based on the Versatile Buck-Boost Topology for Electric Vehicle Applications.

The composite converter allows integrating the high-efficiency converter modules to achieve superior efficiency performance, becoming a prominent solution for electric transport power conversion. In this work, the versatile buck–boost dc–dc converter is proposed to be integrated into an electric vehicle composite architecture that requires a wide voltage range in the dc link to improve the electric motor efficiency. The inductor core of this versatile buck–boost converter has been redesigned for high voltage applications. The versatile buck–boost converter module of the composite architecture is in charge of the control stage. It provides a dc bus voltage regulation at a wide voltage operation range, which requires step-up (boost) and step-down (buck) operating modes. The PLECS thermal simulation of the composite architecture shows a superior power conversion efficiency of the proposed topology over the well-known classical noninverting buck–boost converter under the same operating conditions. The obtained results have been validated via experimental efficiency measures and experimental transient responses of the versatile buck–boost converter. Finally, a hardware-in-the-loop (HIL) real-time simulation system of a 4.4 kW powertrain is presented using a PLECS RT Box 1 device. The HIL simulation results verified the accuracy of the theoretical analysis and the effectiveness of the proposed architecture.

Analysis and Implementation of a Bidirectional Converter with Soft Switching Operation

This paper presents a soft switching direct current (DC) converter, with the benefits of bidirectional power conversion and wide-ranging voltage operation for battery charging and discharging capability. A series resonant circuit with variable switching frequency modulation is used to achieve the advantages of soft switching turn-on or turn-off of semiconductor devices. Therefore, the switching power losses in power devices can be reduced. A symmetric resonant circuit topology with a capacitor–inductor–inductor–capacitor (CLLC) structure is adopted to achieve a bidirectional power conversion capability for battery storage units in electric vehicle applications. Due to the symmetric circuit structure on both input and output sides, the converter has similar voltage gains for each power flow operation. In order to overcome the drawback of narrow voltage range operation in conventional resonant converters, a variable transformer turns ratio is adopted in the circuit, to achieve wide output voltage operation (150–450 V) for battery charging applications. To demonstrate the converter performance, a 1-kW laboratory prototype was constructed and tested. Experimental results are provided, to verify the effectiveness of the studied circuit.

Design and Implementation of a High-Power DC/DC Converter for HVDC Interconnections With Wide DC Voltage Range and Fault-Blocking Capability

Highly efficient and lightweight high-voltage high-power dc/dc converter is one of the key equipments needed by future HVDC grid. In order to satisfy the technical requirements of interconnecting HVDC lines with different voltage levels, this article develops a thyristor-submodule hybrid dc/dc converter (TSDC) by combining the merits of low cost, low conduction loss, and high robustness of thyristors with the high controllability of the cascaded half-bridge submodules (SMs). The proposed converter presents the attractive features of efficient dc/dc conversion, reliable turn-on and turn-off of the thyristors, wide dc voltage operation range, and above all, the dc fault-blocking capability which avoids the installation of dc circuit breakers. The circuit structure, operating principle, and control schemes are discussed. The validity and effectiveness of the TSDC are verified by 150-MW, 100-kV/300-kV simulation case study as well as the experimental tests from a 4.5-kW, 300-V/450-V scaled-down prototype.

Bidirectional Resonant Converter for DC Microgrid Applications

A bidirectional resonant converter is presented and verified in this paper for an electric vehicle battery charger/discharger system. The presented circuit can achieve forward and backward power operation, low switching losses on active devices, and wide output voltage operation. The circuit structure of the presented converter includes two resonant circuits on the primary and secondary sides of an isolated transformer. The frequency modulation approach is adopted to control the studied circuit. Owing to the resonant circuit characteristic, active devices for both forward (battery charge) and backward (battery discharge) power operation can be turned on at zero voltage switching. In order to implement a universal battery charger for different kinds of electric vehicle applications, the DC converter is demanded to have a wide output voltage range capability. The topology morphing between a full bridge resonant circuit and half bridge resonant circuit is selected to obtain high- and low-output voltage range operations so that the 200–500 V output voltage range is realized in the presented resonant converter. Compared to the conventional bidirectional converters, the proposed can be operated under a wide voltage range operation. In the end, a 1 kW laboratory prototype circuit is built, and experiments are provided to demonstrate the validity and performance of the presented bidirectional resonant converter.

Implementation of a Resonant Converter with Topology Morphing to Achieve Bidirectional Power Flow

A DC converter with the benefits of reverse power capability, less switching loss and wide voltage operation is presented and implemented for wide input voltage applications such as fuel cell energy, photovoltaic (PV) system and DC wind power. Two full bridge resonant circuits are used in the presented converter to achieve bidirectional power flow capability and reduce switching losses on active devices. To overcome the wide input DC voltage variation problem for fuel cell energy and PV solar panel, the topology morphing between the half bridge circuit and full bridge circuit is adopted on the primary side to obtain low (or high) voltage gain under a high (or low) input voltage condition. Therefore, the stable DC voltage is controlled at the load side by using the variable switching frequency modulation. The studied hybrid CLLC converter is tested by a 1 kW prototype and the performance is verified and confirmed by experiments.

Analysis and Implementation of a Frequency Control DC–DC Converter for Light Electric Vehicle Applications

In order to realize emission-free solutions and clean transportation alternatives, this paper presents a new DC converter with pulse frequency control for a battery charger in electric vehicles (EVs) or light electric vehicles (LEVs). The circuit configuration includes a resonant tank on the high-voltage side and two variable winding sets on the output side to achieve wide output voltage operation for a universal LEV battery charger. The input terminal of the presented converter is a from DC microgrid with voltage levels of 380, 760, or 1500 V for house, industry plant, or DC transportation vehicle demands, respectively. To reduce voltage stresses on active devices, a cascade circuit structure with less voltage rating on power semiconductors is used on the primary side. Two resonant capacitors were selected on the resonant tank, not only to achieve the two input voltage balance problem but also to realize the resonant operation to control load voltage. By using the variable switching frequency approach to regulate load voltage, active switches are turned on with soft switching operation to improve converter efficiency. In order to achieve wide output voltage capability for universal battery charger demands such as scooters, electric motorbikes, Li-ion e-trikes, golf carts, luxury golf cars, and quad applications, two variable winding sets were selected to have a wide voltage output (50~160 V). Finally, experiments with a 1 kW rated prototype were demonstrated to validate the performance and benefits of presented converter.

Hybrid DC-DC Converter with Low Switching Loss, Low Primary Current and Wide Voltage Operation

A full-bridge converter with an additional resonant circuit and variable secondary turns is presented and achieved to have soft-switching operation on active devices, wide voltage input operation and low freewheeling current loss. The resonant tank is linked to the lagging-leg of the full bridge pulse-width modulation converter to realize zero-voltage switching (ZVS) characteristic on the power switches. Therefore, the wide ZVS operation can be accomplished in the presented circuit over the whole input voltage range and output load. To overcome the wide voltage variation on renewable energy applications such as DC wind power and solar power conversion, two winding sets are used on the output-side of the proposed converter to obtain the different voltage gains. Therefore, the wide voltage input from 90 to 450 V (Vin,max = 5Vin,min) is implemented in the presented circuit. To further improve the freewheeling current loss issue in the conventional phase-shift pulse-width modulation converter, an auxiliary DC voltage generated from the resonant circuit is adopted to reduce this freewheeling current loss. Compared to the multi-stage DC converters with wide input voltage range operation, the proposed circuit has a low freewheeling current loss, low switching loss and a simple control algorithm. The studied circuit is tested and the experimental results are demonstrated to testify the performance of the resented circuit.

Analysis of a PWM Converter with Less Current Ripple, Wide Voltage Operation and Zero-Voltage Switching

This paper studies and implements a power converter to have less current ripple output and wide voltage input operation. A three-leg converter with different primary turns is presented on its high-voltage side to extend the input voltage range. The current doubler rectification circuit is adopted on the output side to have low current ripple capability. From the switching states of the three-leg converter, the presented circuit has two equivalent sub-circuits under different input voltage ranges (Vin = 120–270 V or 270–600 V). The general phase-shift pulse-width modulation is employed to control the presented converter so that power devices can be turned on at zero voltage in order to reduce switching loss. Compared to two-stage circuit topologies with a wide voltage input operation, the presented converter has the benefits of simple circuit structure, easy control algorithm using a general integrated circuit or digital controller, and less components. The performance of the presented circuit is confirmed and validated by an 800 W laboratory prototype.

Investigation of a hybrid converter with 16:1 wide voltage operation

Investigation of a hybrid converter with 16:1 wide voltage operation

Implementation of a Wide Input Voltage Resonant Converter with Voltage Doubler Rectifier Topology

A new circuit structure of LLC converter is studied and implemented to achieve wide zero-voltage switching range and wide voltage operation such as consumer power units without power factor correction and long hold up time demand, battery chargers, photovoltaic converters and renewable power electronic converters. The dc converter with the different secondary winding turns is adopted and investigated to achieve the wide input voltage operation (50–400 V). To meet wide voltage operation, the full bridge and half bridge dc/dc converters with different secondary turns can be selected in the presented circuit to have three different voltage gains. According to input voltage range, the variable frequency scheme is employed to have the variable voltage gain to overcome the wide input voltage operation. Therefore, the wide soft switching load variation and wide voltage operation range are achieved in the presented resonant circuit. The prototype circuit is built and tested and the experiments are demonstrated to investigate the circuit performance.

DC Converter with Wide Soft Switching Operation, Wide Input Voltage and Low Current Ripple

A soft switching current-source resonant converter is presented and implemented for wide voltage applications such as fuel cells and solar power. An LLC (inductor–inductor–capacitor) converter is adopted to accomplish zero voltage (current) operation on active switches (diodes). Thus, the circuit efficiency is increased. The interleaved pulse-width modulation (PWM) converter is employed on the input side to accomplish low input ripple current. A hybrid LLC converter is adopted to achieve wide voltage operation from Vin, min to 4Vin, min and to improve the weakness of a conventional LLC converter. Half-bridge diode rectification is employed on the output side to decrease power loss on the rectifier diode. To confirm the theoretical analysis and feasibility, experimental verifications with a 500-W prototype are demonstrated in this paper.

Resonant converter with less voltage rating of power switches and wide voltage operation

A resonant converter with less voltage rating of power switches and wide voltage operation is investigated in this Letter for medium voltage applications. Four active switches and two split capacitors are adopted on the primary side to reduce the voltage rating on power semiconductors. The resonant converter is adopted in the converter to have a wide soft switching operation range. Two flying capacitors are used in the presented circuit to operate as the resonant capacitor and also to achieve voltage balance of two input split capacitors. The variable winding turns are used on the secondary side to overcome the problem of the limited voltage operation in the conventional resonant converter. If the input voltage is in the low-input voltage range, the low turns-ratio of the power transformer is used to increase the voltage gain of the resonant converter. If the input voltage is in a high-voltage range, then the high turns-ratio of the transformer is adopted to reduce the voltage gain. Thus, the proposed converter can achieve wide input voltage operation. Experimental results with a 0.8 kW prototype are provided to confirm the effectiveness of wide input voltage operation from 260 to 800 V.

Analysis and Verification of a Wide Input Voltage PWM Converter with Variable Windings

A three-leg pulse-width modulation converter with auxiliary windings is provided and investigated to realize wide voltage operation and zero voltage switching characteristics on power switches. The presented converter has three converter legs on the input-side and two sets of winding turns on the output-side. Owing to the on/off states of the three converter legs and the two sets of secondary winding turns, the proposed converter can be operated under three different equivalent circuits to have wide input voltage operation from 30V ~ 240V (Vin,max = 8Vin,min). Compared with the multi-stage converters to realize wide input voltage operation, the proposed circuit topology has fewer circuit components and a simple control algorithm. Conventional duty cycle control with phase-shift between each converter leg is adopted to regulate load voltage and also accomplish zero voltage switching on active switches. The presented three-leg converter is tested with a laboratory circuit. Finally, experiments testify to the performance and validity of the presented converter.

Wide Voltage Resonant Converter Using a Variable Winding Turns Ratio

This paper presents a inductor–inductor–capacitor (LLC) resonant converter with variable winding turns to achieve wide voltage operation (100–400 V) and realize soft switching operation over the entire load range. Resonant converters have been developed for consumer power units in computers, power servers, medical equipment, and adaptors due to the advantages of less switching loss and better circuit efficiency. The main disadvantages of the LLC resonant converter are narrow voltage range operation owing to wide switching frequency variation and limited voltage gain. For computer power supplies with hold-up time function, electric vehicle battery chargers, and for power conversion in solar panels, wide input voltage or wide output voltage operation capability is normally demanded for powered electronics. To meet these requirements, the variable winding turns are used in the presented circuit to achieve high- or low-voltage gain when Vin is at low- or high-voltage, respectively. Therefore, the wide voltage operation capability can be implemented in the presented resonant circuit. The variable winding turns are controlled by an alternating current (AC) power switch with two back-to-back metal-oxide-semiconductor field-effect transistors (MOSFETs). A 500-W prototype is implemented and test results are presented to confirm the converter performance.

DC–DC converter implementation with wide output voltage operation

A direct current (DC) to DC converter with soft switching and high efficiency is developed for industry power units with a wide range of output voltage applications. A series resonant converter is the main circuit on the primary side to accomplish the soft switching characteristics for the active devices and rectifier diodes without switching loss or reverse recovery current loss. To overcome the drawback of the limited operation input or output voltage range in conventional LLC converters, a hybrid resonant converter including a half-bridge circuit and a full-bridge circuit with auxiliary windings is developed to achieve 8:1 (Vo,max = 8Vo,min) output voltage characteristics for a wide range of output voltage applications. To achieve this function, two AC power switches are used in the developed circuit. Since a single-stage hybrid resonant converter is presented instead of a two-stage converter to realize wide voltage range operation, the developed circuit has better efficiency when compared to conventional LLC converters and two-stage DC–DC converters. To confirm the circuit analysis and effectiveness, a prototype with a 400 W rated power was built and tested.

Analysis and Implementation of a Phase-Shift Pulse-Width Modulation Converter with Auxiliary Winding Turns

A phase-shift pulse-width modulation converter is studied and investigated for railway vehicle or solar cell power converter applications with wide voltage operation. For railway vehicle applications, input voltage range of dc converters is requested to have 30–40% voltage variation of the nominal input voltage. The nominal input voltages of dc converters on railway vehicles applications may be 37.5 V, 48 V, 72 V, 96 V and 110 V. Therefore, a new dc converter with wide input voltage operation from 25 to 150 V is presented to withstand different nominal input voltage levels such as 37.5–110 V on railway power units. To realize wide input voltage operation, an auxiliary switch and auxiliary transformer windings are used on output side of conventional full-bridge converter to have different voltage gains under different input voltage values. Phase-shift pulse-width modulation is adopted in the developed dc converter to accomplish soft switching operation on power switches. To confirm and validate the practicability of the presented converter, experiments based on a 300 W prototype were provided in this paper.

A Novel Impedance-Network-Based Electric Spring

An electric spring (ES) can well maintain the balance between supply and demand to compensate for the intermittent nature of small-scale renewable energy resources (RES). Despite its popularity, the second generation of ES (ES-2) is deemed to have a few practical problems. The most conspicuous one is the requirement of accurate dead-time control is in the ES circuit to avoid bridge shoot-through problem, which is necessitated by the series-connection of multiple voltage sources and/or converters to realize a wide voltage range. This however could cause output voltage waveform distortions. In this study, inspired by the Z-source network structure, we propose a novel ES topology with a specifically designed impedance network, i.e., an impedance-network-based (i.e., a network of passive devices such as inductors and capacitors) ES (IN-ES), which intrinsically has a wide voltage range and is immune to the bridge shoot-through issue (i.e., switch tubes on the same bridge arm of the inverter are turned ON/OFF at the same time). Detailed theoretical derivation, simulation and experimentation are conducted in this study, which verify the unique advantageous features of the proposed IN-ES, demonstrating a wide voltage operation range, undistorted waveforms and safe operations.