Input Voltage Applications Research Articles

Investigations on heat-generation stability and PTC effects of self-heating cement composites under diverse temperature conditions

In this study, the novel aspect lies in investigating heat-generation stability expressed as positive temperature coefficient (PTC) effects of self-heating cement under diverse temperature conditions. Self-heating cement composites were fabricated, and subjected to various types of heating tests including monotonic, cyclic, and long-term tests at three distinct temperatures: 25°C, 0°C, and −20°C. The results revealed a novel finding that the heat-generation performance decreased due to the increased electrical resistivity during the heating test, attributed to the PTC effect when high input voltage was applied. Conversely, the absence of PTC effect with low input voltage application resulted in a consistent temperature increase and negligible changes in electrical resistivity, particularly at low temperatures. These experimental findings provide valuable insights into the investigations on stability of heat-generation performance of self-heating cement composites, offering implications for their practical applications.

Soft charging and fewer switches based single‐source double‐boost multilevel DC‐AC converter for low/medium voltage applications

AbstractThis paper presents a novel generalized step‐up switched‐capacitor multilevel inverter (SCMLI) appropriate for low/medium voltage input applications. To reduce the overall number of power switches, the suggested topology makes use of reduction switch count (SC) technology. The complementary working mechanism of each pair of switches simplifies the modulation method. The complete inductive‐load capability is taken into account in the proposed inverter. Furthermore, because capacitor voltages are automatically balanced, complex voltage control circuitry is not necessary. Due to a reduction in current spikes on the devices, the topology also has the ability to soft‐charge the capacitors in a quasi‐resonant manner. Performance is also enhanced by extending the lifetime and dependability of the inverters. The construction, operation, modulation method, values of the capacitors, and circuit losses are explained to demonstrate how the suggested topology should function. One of the inverter's primary differentiators from the others is its double‐boosting capability based on reduced components. Based on loss calculations, a thorough analysis of the suggested topology's efficiency of 98.31% is presented. Next, the benefits of the suggested inverter are compared to those of other inverters that have been recently suggested. The steady‐state and dynamic performance of the suggested topology is then confirmed by modeling the system on the Simulink platform and performing experiments using a DSP‐based prototype experimental setup.

Push-pull forward LLC resonant converter for low input voltage applications

A push-pull forward LLC resonant converter suitable for renewable energy power generation systems is proposed in this paper. The converter introduces the LLC resonant tank into the traditional push-pull forward converter and adopts pulse frequency modulation (PFM) control, which solves the problem of voltage spike of switches of the conventional push-pull converter, realizes the zero-voltage switching (ZVS) of the switches and has high conversion efficiency. In addition, the rectifier part of the structure adopts voltage doubling rectifier technology, which is beneficial to reduce the turn ratio and optimize the leakage inductance of the transformer. In this paper, the working principle of the converter is described in detail, and its gain characteristics and soft switching conditions are analyzed. Finally, an experimental prototype of 1 kW is built, and the output voltage of 380 V is achieved when the rated input voltage is 48–72 V, and its efficiency is up to 96.1 %.

Novel Coordinated Control Strategy for Step-Up/Down Current-Source Converter

Current-source converter (CSC) is more attractive and increasingly used to occasions with higher requirements for reliability due to inherent anti-short circuit ability. This paper combines the CSC with DC/DC converter to adapt to lower input voltage applications. However, rational allocation of the duty cycle for each switch to achieve the target voltage output and the increase of overall switching times brought by DC/DC converter are major problems. Proposed coordinated control strategy can reasonably take full advantage of degrees of freedom based on the adjustment variable to achieve accurately control of grid-side current and load voltage. In addition, dc-link current pulses according to 6 times grid angular frequency which avoids using the zero-vector to reduce the switching times. Experimental results show the proposed scheme can not only guarantees the power quality at grid side and precise voltage output, but also avoids using zero-vector.

An industrial design of 400 V – 48 V, 98.2% peak efficient charger usingE‐mode GaNtechnology with wide operating ranges for xEV applications

AbstractThis paper offers a wide‐operating range electric vehicle charger design by employing an interleaved inductor–inductor–capacitor iL2C DC–DC converter. It uses two parallel L2C converters with 8‐GaN switches on the primary side and a shared rectifier circuit on the secondary side, which it also enhances the circulating current, conduction losses, and current sharing. For iL2C converter, a constant voltage charging mode of operation is designed, also it proposes a hybrid control scheme of variable frequency + phase shift modulation (VFPSM). The entire concept is designed, simulated, and validated with a rated input voltage and load voltage of three different load conditions with converter line and load regulations are analyzed. To evaluate controller and converter performance, the idea is proven experimentally for variable load condition of full load, half load, light load with a rated input and output voltage of 400Vin–48V0. In addition, line regulation is also performed and validated for wide input voltage application of 300Vin–500 Vinwith an output voltage of 48V0at full load and peak efficiency of 98.2% is determined. Further, to provide the system effectiveness converter efficiencies are presented at various load operations from 3.3 kW to 330 W.

A Novel Hybrid Control Strategy and Dynamic Performance Enhancement of a 3.3 kW GaN–HEMT-Based iL2C Resonant Full-Bridge DC–DC Power Converter Methodology for Electric Vehicle Charging Systems

The conventional resonant inductor–inductor–capacitor (L2C) DC–DC converters have the major drawbacks of poor regulation, improper current sharing, load current ripples, conduction losses, and limiting the power levels to operate at higher loads for electric vehicle (EV) charging systems. To address the issues of the L2C converter, this paper proposes an interleaved inductor–inductor–capacitor (iL2C) full-bridge (FB) DC–DC converter as an EV charger with wide input voltage conditions. It comprises two L2C converters operating in parallel on the primary side with 8-GaN switches and maintains the single rectifier circuit on the secondary side as common. Further, it introduces the hybrid control strategy called variable frequency + phase shift modulation (VFPSM) technique for iL2C with a constant voltage charging mode operation. The design requirements, modeling, dynamic responses, and operation of an iL2C converter with a controller are discussed. The analysis of the proposed concept designed and simulated with an input voltage of 400 Vin at a load voltage of 48 V0 presented at different load conditions, i.e., full load (3.3 kW), half load (1.65 kW), and light load (330 W). The dynamic performances of the converter during line and load regulations are presented at assorted input voltages. In addition, to analyze the controller and converter performance, the concept was validated experimentally for wide input voltage applications of 300–500 Vin with a desired output of 48 V0 at full load condition, i.e., 3.3 kW and the practical efficiency of the iL2C converter was 98.2% at full load.

Nonisolated High-Step-Down DC–DC Converters With Low Component Count and Voltage Stress

This paper proposes two new non-isolated high step-down DC/DC converters. The converters' voltage conversion ratio and their semiconductor components' voltage stress are improved compared to the conventional buck converter. By coupling the inductors of the first proposed converter, its volume and price is reduced. By employing a clamp circuit with low elements to the first proposed converter, the second proposed converter is introduced, in which its voltage conversion ratio and the voltage stress of components are improved significantly; thus, in high input voltage applications, high-quality components (switches with low on-resistance and diodes with low forward voltage) can be used. In these converters, the leakage inductances of the coupled inductor are clamping, and their energy is recovered. The proposed converters have fewer elements than related high step-down counterparts' converters leading to lower volume and losses due to lower elements, increasing efficiency. The switches of the proposed converters are switches simultaneously, reducing the converters' control circuit complexity. This paper discusses the theoretical analysis and operational principle of both proposed converters. Besides, to verify their performances, experimental results of the converters with 155-24 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> input and output voltage are presented.

Conduction and entropy analysis of a mixed memristor-resistor model for neuromorphic networks

To build neuromorphic hardware with self-assembled memristive networks, it is necessary to determine how the functional connectivity between electrodes can be adjusted, under the application of external signals. In this work, we analyse a model of a disordered memristor-resistor network, within the framework of graph theory. Such a model is well suited for the simulation of physical self-assembled neuromorphic materials where impurities are likely to be present. Two primary mechanisms that modulate the collective dynamics are investigated: the strength of interaction, i.e. the ratio of the two limiting conductance states of the memristive components, and the role of disorder in the form of density of Ohmic conductors (OCs) diluting the network. We consider the case where a fraction of the network edges has memristive properties, while the remaining part shows pure Ohmic behaviour. We consider both the case of poor and good OCs. Both the role of the interaction strength and the presence of OCs are investigated in relation to the trace formation between electrodes at the fixed point of the dynamics. The latter is analysed through an ideal observer approach. Thus, network entropy is used to understand the self-reinforcing and cooperative inhibition of other memristive elements resulting in the formation of a winner-take-all path. Both the low interaction strength and the dilution of the memristive fraction in a network provide a reduction of the steep non-linearity in the network conductance under the application of a steady input voltage. Entropy analysis shows enhanced robustness in selective trace formation to the applied voltage for heterogeneous networks of memristors diluted by poor OCs in the vicinity of the percolation threshold. The input voltage controls the diversity in trace formation.

Hybrid Control for Three-Level LLC Resonant Converter of Dual-Bridge for Wide Output Range

A three-level (TL) LLC resonant converter of dual-bridge (DB) with hybrid control modulation strategy is proposed for the wide output-voltage range and high input-voltage applications. The topology integrates two neutral-point-clamped arms (NPCs) through an auxiliary transformer, which forms a new controllable double-voltage structure and makes all MOSFETs hold half of the input voltage. Based on the characteristics of the new topology, a hybrid modulation strategy is proposed corresponding to three gain modes, which include conventional pulse frequency modulation (PFM) and fixed frequency phase shift modulation (FF-PSM). Compared to conventional modulation strategies, the proposed hybrid modulation strategy, which improves the output voltage gain range, achieves zero-voltage switching (ZVS) of all the MOSFETs and zero-current switching (ZCS) of rectifier diodes under wider operating voltage and full load range. To minimize the frequency window and improve the efficiency of the converter, the parameter optimization method is designed, which based on the characteristics of the modulation strategy and the relationship among the maximum output voltage gain, resonant current and turned-off current. At last, the experimental results of the 600W prototype are presented to confirm the theoretical and characterization analysis.

An Enhanced Anti-surge Circuit for New Energy Vehicle Electronics System

This paper presents an input surge protection circuit for automotive electronics systems with an adjustable overvoltage protection threshold suitable for high input voltage applications. Compared with the conventional overvoltage protection circuit, it boasts a new high-voltage bandgap reference circuit design without pre-regulation, which takes up less space and can be used on a limited PCB board, expanding the practical application range of the chip. The gate protection circuit can monitor the gate-source voltage of the power MOS in real-time and control the charge pump’s operating mode to improve the system’s safety. The design and simulation of the circuit adopt the 0.18 μm 5V/25V BCD process. The simulation results show that the bandgap reference voltage varies by only 0.38 mV in the input voltage range of 3.5 V-25 V. The quiescent current is 146 uA at 5 V supply voltage. The power MOS can be turned on quickly within 50 us. The overvoltage response time is 599 ns, permitting the circuit to be shut down when a surge occurs.

Single‐stage buck‐boost off‐grid inverter with feedforward control

SummarySince the output voltage accuracy of the off‐grid inverter is low with the proportional‐integral (PI) control and a two‐stage inverter is often used in the low input voltage application, a single‐stage buck‐boost off‐grid inverter with feedforward control is proposed. The proposed inverter consists of a buck‐boost converter and a full‐bridge inverter. The buck‐boost converter operates at high frequency, while the full‐bridge inverter operates at line frequency. Therefore, the intermediate bus voltage is controlled as the unipolar half‐cycle sinusoidal voltage wave to reduce the voltage stress of semiconductors, and film capacitors can be used as intermediate bus capacitors for high reliability and high power density. The operating principle is illustrated. Design guidelines and example are given. The stability analysis and external characteristic analysis are given. A 500‐W proposed inverter is constructed to verify the theoretical analysis.

A new extended single-switch high gain DC–DC boost converter for renewable energy applications

High-gain DC/DC converters are considered one of the most important components of green energy systems. Large numbers of these converters are used for increasing the voltage gain by using an extreme duty cycle. However, it increases losses and the cost, degrades the system performance, and hence obtains a low efficiency. In this article, a new design of a high-gain DC/DC boost converter is proposed. This converter has the potential to be used in low input voltage applications that need a high voltage gain such as systems powered by solar photovoltaic panels and fuel cells. The new topology is characterized by its simplicity of operation, high voltage gain, better efficiency, continuity of the input current, reduced number of inductors and capacitors, and can be extended to get higher gains. The converter structure, principle of operation, and design consideration of inductors and capacitors are presented in detail. Derivation of power losses and efficiency is presented. A laboratory prototype is implemented, and various experimental tests are given. The achievement of the suggested design is confirmed and compared with other recent high-gain converters.

Modified Two-Channel LLC Resonant Converter With Optimal Efficiency for Wide Input Voltage Applications

A modified two-channel LLC resonant converter with optimal efficiency for wide input voltage applications. The converter has the same voltage gain and power handing ability as conventional full-bridge (FB) resonant converter, but the hardware cost is lower than conventional FB resonant converter, and the operational frequency range is narrower than conventional resonant converter for the same working condition. It has the characteristics of low input impedance at low input voltage, which is used to provide high voltage gain, and high input impedance at high input voltage, which is used to provide low voltage gain, the above characteristics are analyzed and optimized to improve the efficiency for photovoltaic applications where wide voltage gain is require. A 1 kW prototype is developed, the input voltage ranges from 80 V to 200 V, the output voltage and output power are 400 V and 1 kW, the experimental result shows that the full-load efficiency can reach 96.5% over the entire input voltage range, and the peak efficiency can reach 96.9% at full-load state.

An extendable soft‐switched high step‐up converter with near zero‐ripple input current suitable for fuel cell‐powered applications

In this paper, an extendable high step-up topology is presented for the low input voltage applications, that is, fuel cell (FC) source. The proposed converter eliminates the pulsating input current and reduces the high input current ripple. Thus, the lifetime of this non-linear source and energy flow is significantly improved. The high output voltage is achieved by using voltage multiplier cells (VMC) and a coupled inductor (CI) with reduced elements. Moreover, an auxiliary circuit is applied due to restoring the energy of leakage inductance in the CI. Therefore, not only all power switching devices are turned on under zero voltage switching (ZVS) but also the input current ripple is remarkably reduced to zero. Furthermore, normalized semiconductors’ voltage stresses are diminished. The reverse recovery problem of diodes and their turn-off power losses at high frequencies are alleviated owing to their zero current switching (ZCS) turn-off. In this paper, the performance of the proposed structure is investigated and compared with the traditional converters considering their voltage gain and voltage stress. Eventually, a 500-W prototype of the proposed converter is built and tested to validate mathematical analyses.

Closed Loop Modified SEPIC Converter for Photovoltaic System

The high static gain modified single ended primary coil (MSEPIC) converter is presented in this paper. The proposed converter presents low switch voltage and high efficiency for low input voltage and high output voltage applications. The configuration of MSEPIC converter is presented and analyzed. Closed loop feedback control with PID controller based on triggering system is developed for MSEPIC converter to maintain constant output voltage. Furthermore, the model is integrated with Photovoltaic generator where the input voltage and current depend on the solar irradiation rates. The proposed model is analyzed and simulated in Matlab/Simulink and m-file code. Simulation model is developed with a maximum power at full sun equal to 315 W, which presents efficiency equal to 99.03%. The PID controller works as intended, as the output voltage can approach the expected value. Furthermore, performance and robustness are tested by load variations and set point variations.

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.

Three-Phase Three-Level Isolated DC-DC Soft Switching Converter For Solar Applications

Three-level isolated DC-DC converter is an attractive topology in high input voltage applications, which can provide the voltage stress of the power devices to only a half of the dc voltage and also reduce the size of dc filter requirement. But major limitations in the existing three level ZVS converter topologies are brought out with an increased inductance in the primary side and it required to provide complete ZVS of all primary devices down to light loads. By employing an external inductance in the primary of the transformer, total leakage inductance of the transformer increases which is required for realization of soft switching of the converter switches but there are some disadvantages of connecting external inductance in the primary of the transformer. To overcome all these drawbacks, the three-phase three-level isolated DC-DC soft switching converter has been proposed in order to reduce voltage and current stresses. This converter topology requires less number of control switches and operates with an asymmetrical duty cycle control. The proposed three level DC-DC converters provide two- level voltage waveform before dc output filter, which significantly reduce the size of dc output filter. The proposed work has been implemented using MATLAB/SIMULINK and the performance of the proposed converter is verified through simulation results.&#x0D;

Overview on second & third order resonant switch mode power converter for variable input voltage applications

DC-DC converters have wide applications in the field of battery charger, distributed generation, power supplies and so on. There are various isolated and non-isolated topologies available which has to be chosen based on the size, cost , weight, application, power range and duty of the converter. Due to increasing applicability of DC-DC converters, it is essential to enhance the efficiency, controllability and output regulation to a step ahead. Resonant converters at high frequency has gained attention in the market to a large scale due to its low size and weight. With the developing enthusiasm for this subject, it is essential to have a detailed review to sum up and update a unique reference about the soft switching configurations for better performance of the converter. The paper provides a brief overview in two and three element soft switching configurations. Moreover, The current technologies evolved in the field of resonant converters are also briefed for wide input voltage applications.

Analysis of a Hybrid Variable-Frequency-Duty-Cycle-Modulated Low-$Q$ $LLC$ Resonant Converter for Improving the Light-Load Efficiency for a Wide Input Voltage Range

Light load efficiency and output voltage regulation of alow-Q LLC resonant converter is a critical problem for wide input voltage and load range applications. Parasitic capacitances such as rectifier diode junction capacitance (C3) degrade the soft switching performance. Compact size, high density, and high transformer turns-ratio requirements for microinverter applications add significant distributed capacitance (Cd) of the low-profile transformer, worsening the output regulation and zero-voltage-switching (ZVS) capability at light loads. Wide switching frequency requirement for regulation at light loads, which increases core losses and turnOFF switching losses in power MOSFETs, further degrades the power conversion efficiency. The conventional phase-shift modulation causes a high circulating current and loss of ZVS at light loads. Therefore, a hybrid adjustable switching-frequency-dutycycle modulation technique for improving the light load efficiency is proposed and analyzed for a full-bridge LLC resonant converter. Accurate loss analysis for the proposed modulation scheme, including the effect of parasitic capacitances, is performed using time-domain equations. The proposed methodology precalculates the optimal duty cycle at light load conditions for the required input voltage range such that minimum power losses are incurred. Variation in switching frequency at the preselected duty-cycle value regulates the output voltage. ZVS over a wide range of operating conditions is observed. An experimental prototype for a 20-40 V input, 380-V/300-W output LLC converter is tested for the validation of theoretical analysis.

RETRACTED: Resonant converter L3C for E-vehicle for charing a PV battery

Solar radiation and temperature can influence their power and output voltage in electric cars with roofup PV panels (e.g. Vpv = 24–48 V DC). In such devices, the variable input tension (PV panel), increased with various acquisitions and deposited in high voltage battery packaging, must be separated from the full capacity. In addition, the charger can work in constant stress, steady pressure or steady control modes, based on battery charge status (Vbat = 220–400 V CC), from full discharging conditions up to the floating stress level. The application of the variable PV input voltage and different charging conditions poses an significant task to control the converter.