Step-down Mode Research Articles

Bidirectional DC - DC Converter Topology for Electric Vehicles Using Fuzzy Logic Controller

This project organizes an application of hybrid electric vehicle systems operated with novel designed bidirectional dc-dc converter (BDC) which interfaces a main energy storage (ES1), an auxiliary energy storage (ES2) and dc bus of different voltage levels. Proposed BDC converter can operate both step up and step-down mode. In which step up mode represents low voltage dual source -powering mode and step-down mode represents high voltage dc link energy –regenerating mode, both the modes are operated under the control of bidirectional power flow. This model can independently control power flow between low voltage dual source buck/boost modes. Here in, the circuit configuration, operation, steady-state analysis, and closed-loop control of the proposed BDC are discussed according to its three modes of power transfer. In this project fuzzy logic controller is used and also system results are validating through MATLAB/SIMULINK software. Index Terms—Bidirectional dc/dc converter (BDC), dual battery storage, hybrid electric vehicle, Fuzzy logic controller.

Analysis and Evaluation of 99% Efficient Step-up/down Converter based on Partial Power Processing

A step-up/and down converter based on partial power processing is proposed in this paper. With the same state equations, the step-up and step-down modes have the same small signal modelling. Therefore, a unified control strategy can be designed for both operating modes, achieving the auto-switching between two operating modes without requiring any additional control. The effect of the transformer's turn ratio on the current and voltage stresses is then analysed. The component stresses are reduced due to the decoupling of transformer. Moreover, the component stress factor method is implemented to evaluate the proposed step-up/down partial power converter. Compared with conventional step-up or step-down partial power converters, the proposed converter has the least component stress factor for a high voltage electrolysis system. In order to validate the proposed topology and modulation strategy, a 400 V prototype is implemented and experimentally evaluated. Measurement results confirm the high efficiency in the overall voltage range, and the maximum efficiency exceeds 99.5%.

Voltage Multiplier based Non-Isolated Buck-Boost Converter

This paper presents a new non-isolated high-gain Buck-Boost Converter (BBC) that uses a switched-inductor (SL) voltage multiplier. This type of DC-DC converter can be very useful in renewable energy applications, especially PV, where the output DC voltage is stepped up to a higher voltage. The output voltage of the proposed switched-inductor BBC (SLBBC) is around 15 times the input voltage with positive polarity when a 0.75 duty cycle of the power switches is used. This is achieved without the use of a transformer or common-core coupled inductors, so the topology is simple to construct. This high output voltage is achieved by using the SL voltage multiplier, which consists of three diodes and two inductors. There are two power switches that operate synchronously, which is an advantage of the design. However, it is discovered that the voltage gain in the step-down mode of the proposed converter is less than that of the other converters. The proposed converter is analyzed in the Continuous Conduction Mode (CCM). The operating principles and steady-state analysis are presented in detail. MATLAB/Simulink was used to prove the effectiveness of the proposed SLBBC.

Performance Analysis of a Cascaded Bidirectional DC-DC Converter for High Current Applications

In this paper, a high-current DC-DC converter with bidirectional capability is presented. The proposed converter topology combines a series capacitor bidirectional converter and a conventional bidirectional converter in a cascaded manner, thus achieving a quadratic voltage gain. The proposed topology is compared with other contemporary high current topologies in terms of voltage gains, component count and conversion efficiency. Furthermore, the converter performance is validated using the Simscape SimPowerSystems toolbox of MATLAB Simulink. It is determined that this topology demonstrated a conversion efficiency of 96% and 98% in step-up and step-down mode respectively, for a 250 W load. Moreover, a current gain of 12.5 was observed in step down mode for a switch duty cycle of 0.4. Lastly, current sharing between inductors and low current ripples were also demonstrated.

Wide voltage range and low current ripple bidirectional DC/DC converter

ABSTRACT Along with the prosperous growth of battery energy storage system being applied in renewable energy system, wide voltage range regulation and low current ripple bidirectional DC/DC converters attract much attention of researchers. Based on a basic boost–buck converter and voltage multiplying unit (VMU), this article proposes a two-stage DC/DC converter. The front stage is an input parallel output serial connected boost–buck converter and the back stage contains a dual-coupled inductors VMU. The storage inductors of the front stage aremagnetically coupled with those in back stage. Employing dual coupled inductors VMU can increase voltage gain while not increasing main switch voltage stress during step-up mode, which can widen the application scenarios. During step-down mode, a fully controlled method can obtain a greater step-down voltage ratio. Due to the interleaving control mode of the main switches, the current ripple of the battery side is lower when the converter works bidirectionally. The proposed converter has the advantages of widening voltage range regulation and lowering current ripple while avoiding extreme switch duty cycle. This article discusses theoretical step-up and step-down work mode of the proposed converter. Experimental results sampled from a 12 V/115 V prototype are presented to verify the analysis of the proposed converter.

Dual-Stacked Bidirectional Boost/Buck DC–DC Converter

A new non-isolated bidirectional DC-DC converter with low voltage and current stresses across the semiconductor devices is presented in this paper. The proposed converter is a combination of a dual-stacked bidirectional boost converter. The converter presents different operations modes, such as: synchronous and asynchronous. These modes can reduce the current ripple of the voltage source. Besides that, in this paper, the modeling and control of the proposed converter are done. To validate the theoretical evaluations of the proposed converter, a 1 kW, 144 V/ 400 V prototype was built to verify its performance where the peak efficiency is 96.33 % and 96.87 % for step-up and step-down modes, respectively.

Contemporary materials for semiconductor switches in an isolated bidirectional DC-DC converter using a closed loop system with linear quadratic regulator control

This research seeks to create a novel bidirectional DC-DC converter capable of high step-up/down power transfer for diverse applications, such as grid systems, energy backup systems, fuel cell vehicles and hybrid electric vehicles. The converter features an inductor linked to an electric power grid to facilitate multi-layer energy conversion with galvanic isolation for improved voltage ratio and galvanic isolation. Notable among its features is this converter's capacity to recycle energy from a leaky inductor without needing additional snubber mechanisms or clamped circuits. To facilitate efficient operation, the converter employs power switches capable of soft switching both step-up and step-down modes. This option permits using MOSFETs with low on-state resistance, which is advantageous due to reduced voltage endurance at the primary side. This research explores the application of a linear quadratic regulator (LQR) for use with a constant frequency bidirectional DC-DC converter. Leveraging the high-order nature of converters, LQR controllers make full use of their potential by offering rapid dynamic response time, reliability and minimal changes in settling time for an array of operating conditions. Thorough analyses were carried out into the availability and stability conditions of an LQR controller in step-up mode using MATLAB/Simulink simulation results as evidence. This study also emphasizes the significance of performance and effectiveness in electronic power-switching devices, which rely heavily on material properties for operation. While silicon has traditionally been employed for these switches, advances in material science have seen wider band-gap semiconductors adopted to improve switching device performance. Therefore, this research encompasses selecting and implementing appropriate semiconductor materials into power electronic switches used by DC-DC converters.

A Wide Conversion Ratio Bidirectional Modified SEPIC Converter with Non dissipative Current Snubber

This article presents a wide conversion ratio bidirectional dc-dc converter based on a bidirectional modified Single-ended primary-inductor converter (SEPIC converter). A key feature of this modified SEPIC converter is the non-dissipative current snubber circuit, which is used to achieve zero current switching and to suppress voltage spikes that occur during MOSFET switching. The snubber is made up of a capacitor, an inductor, and a diode that work together to form a resonant circuit that absorbs the voltage spike and returns it to the circuit without dissipating it. Even with conventional MOSFETs, high efficiency is achieved. The SEPIC converter differs from other bi-directional DC-DC converters in that it provides continuous output current, has fewer components, and can provide high conversion ratios of step-up and step-down voltage without exceedingly low or high duty-cycle. This paper presents a theoretical analysis with stages of operation in both step-up and step-down modes, theoretical waveforms, and the design procedure, as well as a comparison with other bidirectional dc-dc converter topologies. The experimental results are presented to validate the performance of the proposed converter using a 500-W prototype with Voltage Source V1 = 48 V and Voltage SourceV2 = 300 V.

Extendable Bidirectional DC–DC Converter With Improved Voltage Transfer Ratio and Reduced Switch Count

Bidirectional dc-dc converter (BDC) plays an important role in battery-based applications. This paper presents an extendable BDC using 8+5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> components, including 3+ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> MOSFETs, where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> is the number of stages. The detailed analysis of single-stage of the proposed converter is discussed. The voltage transfer ratio (VTR) of the converter during the step-up and step-down modes is derived. The effect of parasitic elements on the VTR and the efficiency is discussed. The state-space model is derived, and the open-loop transfer functions, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\widehat{\boldsymbol{v}}_{\boldsymbol H}/\widehat{\boldsymbol d}_{\boldsymbol H}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\widehat{\boldsymbol{v}}_{\boldsymbol L}/\widehat{\boldsymbol d}_{\boldsymbol L}$</tex-math></inline-formula> for both the modes are obtained. These transfer functions are validated using circuit level simulation. The operating modes of the converter are validated using a 300 W, 650 V, and 50 kHz prototype, and the experimental results are presented. Using the derived transfer functions, the PI controllers are designed using Ziegler–Nichols method for step-up and step-down modes. Using the Xilinx system generator (XSG), the designed controllers are implemented, and the experimental closed-loop results are presented. The performance comparison shows that the VTR of the single-stage converter using four MOSFETs is significantly improved compared to the other converters which achieve the quadratic VTR. Each extended stage requires a single MOSFET along with 4 passive components.

A Coupled Inductor-Based Bidirectional DC-DC Converter with Step-Up Step-Down Operation for Electric Vehicle Applications

A coupled-inductor-based high step-up high step-down DC-DC converter with bidirectional capability suitable for electric vehicle (EV) applications is proposed in this paper. The voltage gain in both step-up and step-down operations is increased by a two-winding coupled inductor. The current ripple in the low-voltage port is low making it suitable for renewable energy sources. In addition, the low number of components causes the efficiency of the proposed converter to be competitive with similar topologies in the literature. Due to the use of only three bidirectional switches with low voltage stress, the cost and volume of the converter are reduced. To demonstrate the performance of the proposed bidirectional converter, an analysis of the operation modes in the steady state is presented. Also, a comparison between the suggested converter and other similar converters in the literature is provided. The results of these comparisons show that the proposed converter has a lower number of components and higher efficiency than the others. In addition, lower voltage stress and noticeable voltage gain in comparison with others are further results of these comparisons. Eventually, the experimental results in step-up and step-down operations are presented. In step-up operation, the experimental prototype is tested under fs = 50 kHz, VLow = 20 V, VHigh = 110 V, rated power = 120 W, with 94.60% efficiency. Furthermore, VHigh is considered 100 V with VLow = 33 V and 94.43% efficiency at 50 W rated power in step-down mode operation.

High Efficiency and High Voltage Conversion Ratio Bidirectional Isolated DC–DC Converter for Energy Storage Systems

In this paper, a novel high-efficiency bidirectional isolated DC–DC converter that can be applied to an energy storage system for battery charging and discharging is proposed. By integrating a coupled inductor and switched-capacitor voltage doubler, the proposed converter can achieve isolation and bidirectional power flow. The proposed topology comprises five switches and a common core coupled inductor that uses only a set of complementary pulse-width-modulated signals to control and achieve high voltage gain without requiring high turn ratios or excessive duty cycles. Moreover, the proposed topology can recover the leakage inductance energy to improve the conversion efficiency. The main switches exhibit zero-voltage switching, which reduces the switching losses. A 500-W bidirectional converter is used to verify the feasibility of the proposed bidirectional converter through theoretical analysis and experiments. The experimental results indicate that the highest efficiency of the proposed converter in the step-up and step-down modes is 97.59% and 96.5%, respectively.

Novel Bidirectional Isolated DC/DC Converter with High Gain Ratio and Wide Input Voltage for Electric Vehicle Storage Systems

This study proposes a novel bidirectional isolated DC/DC converter with a high gain ratio and wide input voltage for electric vehicle (EV) storage systems. The DC bus of an EV can be used to charge its battery, and the battery pack can discharge energy to the DC bus through the bidirectional converter when the DC bus lacks power. The input voltage range of the proposed converter is 24 to 58 V on the low-voltage side, which meets the voltage specifications of most servers and batteries on the market. The proposed topology is verified through design, simulation, and implementation, and voltage gain, voltage stress, and current stress are investigated. The control bidirectional converter is simple. Only one set of complementary signals is required for step-up and step-down modes, which greatly reduces costs. The converter also features a continuous current at the low-voltage side, a leakage inductance function for energy recovery, and zero-voltage switching (ZVS) on certain switches, which can prevent voltage spikes on the switches and increase the efficiency of the proposed converter. A bidirectional converter with a total power of 1 kW is used to verify the topology’s feasibility and practicability. The power at the low-voltage side was 24–58 V, and the maximum efficiency in step-up mode was 94.5%, 96.5%, and 94.8%, respectively; the maximum efficiency in step-down mode was 94.4%, 95.4%, and 93.7%, respectively.

A study on improving the efficiency of non-isolated buck-boost bidirectional DC–DC converter

ABSTRACT In battery-based systems such as hybrid electric propulsion system for ships that use electric propulsion and DC grid, bidirectional converters are often used as interfaces between high-voltage power sources and low-voltage batteries for the purpose of storing excess energy and the fields of application for bidirectional converters are steadily expanding. This study proposes a new bidirectional converter with a high voltage conversion rate and low switch voltage stress. The proposed converter allows current to flow between modules by adding only one capacitor compared to a conventional bidirectional converter. To check the effectiveness of the proposed method, PSIM software by Powersim co. Ltd. was used to perform simulation tests. It was confirmed that the high voltage conversion rate was 4 times that of a conventional bidirectional converter in step-up mode and 1/4 that of a conventional bidirectional converter in step-down mode. Therefore, low-voltage components, such as MOSFETs, GTOs, etc., can be applied in the DC–DC converters thanks to the 1/4 voltage that is required in each switching time.

A Novel Nonisolated GaN-Based Bidirectional DC–DC Converter With High Voltage Gain

A nonisolated bidirectional dc–dc converter is proposed for energy storage systems in this article. The proposed converter is composed of three active switches, two synchronous rectifiers, two clamping capacitors, and two inductors. The proposed converter has advantages of being a simple structure, a fewer number of components, a common ground, lower voltage stress, and wide voltage gain range. Compared with the conventional buck converters, the novel converter triples the effective duty cycle and lowers voltage stresses across the active switches. A 300-W/500-kHz GaN-based experimental prototype is built and tested to verify the correctness and validity, demonstrating a peak efficiency of 94.54% in step-down mode and a peak efficiency of 94.88% in step-up mode.

Tapped-inductor bi-directional Cuk converter with high step-up/down conversion ratio and its optimum design

A bidirectional DC–DC converter is required for an energy storage system. High efficiency and a high step-up and step-down conversion ratio are the development trends. In this research, a series of bidirectional high-gain Cuk circuits was derived by combining tapped inductors and bidirectional Cuk. After analyzing and comparing the characteristics of each circuit, a bidirectional high-gain Cuk circuit with a tapped-inductor (reverse coupling) was proposed. The proposed converter has a simple structure and a high voltage gain in both the step-down (Buck) and step-up (Boost) operation modes. The voltage stress of S2 was low. The voltage stress of S1 was high, however, and this is a disadvantage of the proposed converter. The proposed circuit’s characteristics were thoroughly examined, including the voltage gain characteristics and the design of the main parameters. We established a power loss model of the new topology, and the tapped-inductor turn ratio was optimized for high efficiency. Finally, a 400 W experimental implementation of the converter was shown to achieve efficiencies of 93.5% and 92.4% in the step-up and step-down modes, respectively. These findings verified the validity of the proposed circuit’s theoretical analysis.

Novel High-Step-Up/Step-Down Three-Port Bidirectional DC/DC Converter for Photovoltaic Systems

This paper presents a novel three-port high-step-up/step-down bidirectional DC/DC converter with a coupled inductor for photovoltaic (PV) systems. The proposed converter combines a high-step-up converter, which is used to step-up the PV module to DC bus 200 V, and a battery charge/discharge bidirectional converter to form a three-port bidirectional converter. When sufficient energy is supplied from the PV modules, the converter can step-up the output of the PV modules and provide energy to the DC bus while charging the battery simultaneously. However, when no energy is supplied from the PV modules, the DC bus voltage is provided by the battery. Moreover, the energy stored in the leakage inductor is recycled to the DC-blocking capacitor, and synchronous rectification is conducted in the switch during the step-up mode to reduce switch loss and thereby increase the system’s overall efficiency. Finally, a 500 W three-port bidirectional converter is implemented to verify the feasibility and practicability of the proposed converter. The maximum efficiency of the proposed converter is 95.4%, 94.3%, and 94.7% when operated in the high-step-up mode, battery step-up mode, and step-down mode for the PV modules, respectively.

Development of a Bidirectional DC–DC Converter with Rapid Energy Bidirectional Transition Technology

Bidirectional DC–DC converters are key devices in the DC distribution system and the energy storage system (ESS). It is important to consider the safety of the elements in the converter for rapid conversion of the power direction. Damages may occur to the power-related components in the circuit if the direction of the inductor current or the capacitor voltage changes instantaneously. To make the power flow change smoothly and quickly, this research proposed a bidirectional DC–DC converter with rapid energy transition technology implemented in the circuit architecture. The rapid energy bidirectional transition technology added a resonance path based on the LC resonant circuit, allowing rapid energy conversion through the resonance path. Therefore, the energy in the energy storage element could be quickly converted without causing circuit surges. Analyses of the converter operating in the step-up mode, the step-down mode, and the transition operation mode are presented. The proposed circuit architecture had a high voltage-conversion ratio and a simple architecture. A prototype bidirectional DC–DC converter with a full load of 500 W, a low side voltage of 24 V, and a high side voltage of 200 V was developed to prove the concept. The feasibility of the rapid energy bidirectional transition technology was verified by the simulation results and experimental results using the prototype converter. The maximum efficiencies in the step-up mode and the step-down mode were 95.3% and 93.8% respectively. Under full-load conditions, the transient time of the energy transition from the step-up mode to the step-down mode was 17.7 μs, and the transient time of the energy transition from the step-down mode to the step-up mode was 19.3 μs.

Novel soft-switching integrated various converter of ZVT-ZCT grid connected PV system

Solar photovoltaic systems contribute to the development of the world's most environmentally sustainable and cost-effective electrical energy. High-power inverters commonly use a technique known as three-level design to increase their performance by soft-switching. On the other hand, the switching action is stressed in normal operation because the current or voltage will not be zero at the time of the transition. For CUK, SEPIC, ZETA and CASCODE converters operating in critical switch mode, it has been proposed that a new type of DC-DC converters primarily formed on capacitive coupling DC-DC converters be developed. The proposed converters are zero-current-voltage-switching half-square-quarter-wave converters with a zero-current auxiliary circuit. LC-circuit resonance causes power switches to turn on at zero voltage, getting rid of the switching losses during turn on. The hybrid Incremental Conductance & Integral Regulator technique is used to track MPP available from PV system. The proposed converter's results and efficiency are compared to those of traditional semi-square-quarter-wave zero-current-converter converters. The proposed converters achieved power efficiencies of 98.7% in the step-up mode and 98.8% in the step-down mode for the rated load state, respectively. The proposed CUK, SEPIC, ZETA and CASCODE Converters Simulation are implemented in the MATLAB Simulink programme to validate its efficiency.

A highly efficient isolated single‐phase variable frequency AC–AC converter with flexible buck‐boost factor, inherent safe commutation, and continuous current

This paper proposes an isolated single-phase flexible buck-boost ac–ac converter with an adjustable output frequency and optimized semiconductors count. One power switch only operates with a high switching frequency in each half-cycle of the input voltage, and others operate with a low switching frequency equal to the output frequency. Thanks to this feature, the converter provides high efficiency, 95.5% in step-down mode and 91.5% in step-up mode. The galvanic isolation between the input and output sides is also regarded for the proposed topology by employing two coupled inductors. The converter has an inherent safe commutation by utilizing a simple modulation strategy. Thus, additional snubber circuits and complex commutation strategies are no longer required. The proposed converter does not require any input filter as it operates with the continuous input current. This paper presents the operating principle of the proposed topology in detail. For this purpose, a 200-W experimental prototype has been designed to examine the performance of the suggested converter for different operating modes and output frequencies. Results confirm the theory and operation of the proposed topology.

A Four-Phase Hybrid Step-Up/Down Converter With RMS Inductor Current Reduction and Delay-Based Zero-Current Detection

In this letter, a four-phase hybrid step-up/step-down dc–dc converter with a delay-based zero-current detector (ZCD) is proposed. The proposed power stage operates in step-up or step-down mode depending on the target output voltage. It utilizes hybrid switched-inductor-capacitor and dual-path topologies with multiphase operation to reduce conduction loss due to the dc resistance of the inductor by reducing the rms inductor current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_L</i> ). The delay-based ZCD determines the zero-current point of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_L</i> with a five-bit binary signal to compensate for the propagation delay between the control and the output signals of the driver. The system is fabricated using 180-nm CMOS technology. The power density is 1.838 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the peak efficiency is measured at 89.49% and 86.83% in the step-down and step-up mode, respectively, with a load current range of up to 2 A.