Buck Mode Research Articles

High Voltage Gain Switched-Z-Source Bidirectional DC-DC Converter

The DC-DC converters are the essential modules in electric vehicles, grid interface of renewable energy sources and DC power supplies. This paper presents a novel high gain bidirectional switched Z-source DC-DC converter. The proposed bidirectional converter utilizes switched-capacitor concept with inductors for high voltage gain. The proposed bidirectional converter presents wide operating range of operation in both boost and buck mode of operation. The proposed converter has common ground between input and output, and uses only 5 active switches and 4 passive elements with reduce switch voltage stress. The current drawn from the low voltage side input source is continuous with reduced ripple. The operating principle, circuit analysis, design, mathematical model and closed loop operation of the proposed converter are presented. The proposed converter is verified through computer simulation and laboratory experiments. The simulation and experimental results are presented.

Multimode Smooth Transition Technique for Three-Level Cascaded Noninverting Buck–Boost DC–DC Converter

In this article, a new three-level cascaded noninverting buck-boost converter (TL-CNIBB) is proposed, which has a superior adaptation for a wide-range voltage input of renewable energy access. Firstly, the operation principle is analyzed for TL-CNIBB and it is mainly divided into four modes, namely buck mode with the voltage ratio below or above 0.5, boost mode with the voltage ratio below or above 2. Due to multilevel and multimode features, several fundamental issues are required to be settled, such as a dead zone between buck mode and boost mode, capacitor voltage unbalance on both sides, and subharmonics at the edge of modes. For dead zone and capacitor voltage balance problems, a systematic control strategy is proposed, and four kinds of smooth transition technologies are proposed to deal with different cases. Furthermore, to avoid the chattering and subharmonics at the edge of modes, a modified hysteretic transition method is proposed. Finally, a prototype of TL-CNIBB system is constructed, and the experiments are carried out to verify the performance of the proposed system with high viability and flexibility.

GaN-Based High-Power-Density AC–DC–AC Converter for Single-Phase Transformerless Online Uninterruptible Power Supply

This article introduces a new transformerless ac-dc-ac converter topology suitable for a high-power-density high-frequency single-phase online uninterruptible power supply (UPS) with a common neutral between the input and output ac ports. The proposed converter comprises an input power factor correction rectification (ac-dc) stage which is followed by an inversion (dc-ac) stage. The rectification stage operates in boost mode during the input positive half line cycle and buck-boost mode during the input negative half line cycle, while the inversion stage operates in buck and buck-boost modes in the output positive and negative half line cycles, respectively. The rectification stage utilizes boundary conduction mode control enabling soft-switching and allowing high-frequency operation. The inversion stage is operated in continuous conduction mode, wherein a digital controller regulates the output voltage of the converter across both resistive and reactive loads. The proposed online UPS utilizes a single (nonsplit) dc-bus between the rectification and inversion stages, resulting in a 50% reduction in dc-bus capacitance requirement compared to conventional split-bus online UPS topologies. Additionally, two battery interface solutions are also investigated which provide a trade-off between passive volume and additional switch-count. To verify the performance and control of the proposed online UPS, a GaN-based electrolytic-free 1-kVA prototype online UPS is designed, built, and tested. The prototype ac-dc-ac converter achieves a peak efficiency of 95.2% and maintains a high efficiency of above 92.3% across the full output power range. The electrolytic-free prototype ac-dc-ac converter for the online UPS achieves a power density of 26.4 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Non-Inverting Cascaded Bidirectional Buck-Boost DC-DC Converter with Average Current Mode Control for Lithium-Ion Battery Charger

In order to develop renewable energy, it also needs to enhance the developing of supporting elements. For example, lithium-ion batteries as a component of energy storage. Lithium-ion batteries (Li-ion) have been chosen as energy storage devices for portable equipment, unmanned Aerial Vehicle (UAV) and grid storage systems. But there is a problem such as the process of charging the battery for UAV. Conventional converters used in those chargers have disadvantages such as limited power, lower voltage gain and also high current stress. Therefore, such converters are not efficient to be used for charging the battery. This paper proposes a cascaded bidirectional buck-boost converter for charging the battery. This converter can be operated bidirectional and have better rated power and higher voltage gain. Also, this topology has the same polarity with the input. From the test results, the converter can work in either forward or backward power flow. This converter is working in both buck or boost mode and has an efficiency of 83% in buck mode and 81% for boost mode. The charging process is about 83 minutes until SOC approximately 90 – 95.Keywords: battery charger, cascaded bidirectional buck – boost converter, constant current, li-ion introduction.

Optimal Power Management for Seismic Nodes

Estimating the state-of-charge of a lead-acid battery at remote seismic nodes is a key factor in managing the available power. Optimal management enables the continuous acquisition of seismic data of an area. This paper presents the management of lead-acid batteries at remote seismic nodes, using the Neural Network model's historical data to estimate the battery's state-of-charge. Powersim (PSIM) simulation tool was used to implement photovoltaic energy harvesting system with a buck mode converter and maximum power point tracking algorithm to acquire historical data. A backpropagation neural network technique for training the historical dataset of hourly points in 500 days on the Matlab platform is adopted, and a feedforward neural network is employed due to the irregularities of the input data. The neural network model's hidden layer contains the transfer function of the Tansig Function to produce the model output of state-of-charge estimations. Besides, this paper is based on the management of estimating the state-of-charge of the lead-acid battery near-realtime instead of relying on the vendor's lifecycle information. The simulated results show the simplicity and optimal estimations of state-of-charge of the lead-acid battery with RMSE of 0.023%.

Analysis and Design of a Nonisolated Bidirectional DC–DC Converter Based on CLC Network

This article proposes a nonisolated bidirectional dc–dc converter based on the π type resonant network for renewable energy sources. The circuit consists of a front-stage boost inverter, a CLC resonant network and a poststage voltage doubled rectifier. The proposed converter has simple structure and smaller volume without conventional transformer, easier to achieve modularity and integration. Under bidirectional power flow, the switches can achieve zero voltage turn- on and the rectifier diodes can achieve zero current turn- off with the wide load range. In this article, the operation modes, output power characteristics, soft-switching conditions, and the optimization design of the circuit are analyzed. A 200 W prototype based on GaN device is implemented and tested to verify validity of the proposed converter. The prototype can achieve a peak efficiency 95.4% in boost mode and 94.1% in buck mode.

Implementation of modular MPPT algorithm for energy harvesting embedded and IoT applications

The establishment of the latest IoT systems available today such as smart cities, smart buildings, and smart homes and wireless sensor networks (WSNs) are let the main design restriction on the inadequate supply of battery power. Hence proposing a solar-based photovoltaic (PV) system which is designed DC-DC buck-boost converter with an improved modular maximum power point tracking (MPPT) algorithm. The output voltage depends on the inductor, capacitor values, metal oxide semiconductor field effect transistor (MOSFET) switching frequency, and duty cycle. This paper focuses on the design and simulation of min ripple current/voltage and improved efficiency at PV array output, to store DC power. The stored DC power will be used for smart IoT systems. From the simulation results, the current ripples are observed to be minimized from 0.062 A to 0.02 A maintaining the duty cycle at 61.09 for switching frequencies ranges from 300 kHz to 10 MHz at the input voltage 48 V and the output voltage in buck mode 24 V, boost mode 100 V by maintaining constant 99.7 efficiencies. The improvised approach is compared to various existed techniques. It is noticed that the results are more useful for the self-powered Embedded &amp;amp; Internet of Things systems.

ANALYSIS, DESIGN AND SIMULATION OF ZVS BASED HIGH CONVERSION RATIO ISOLATED DC-DC BUCK CONVERTER FOR ENERGY STORAGE SYSTEM

In this paper, a novel zero voltage switching (ZVS) is based high conversion ratio bidirectional DC-DC converter for the energy storage system proposed. Within the buck mode, the proposed converter is like that of a cascade consisting of an isolated buck-boost converter and a buck converter, thus achieving a high step-down ratio. Similarly, in the boost mode, the converter is analogous to the cascaded structure consisting of a boost converter and an isolated buck-boost converter, and then a high step-up ratio is achieved. Thus, a high conversion ratio has been established with the proposed converter. In addition to this ZVS eliminates switching losses and improves conversion efficiency. Furthermore, the validity and performance of the proposed converter are verified employing a prototype.

Modeling a residential grid-connected PV system with battery–supercapacitor storage: Control design and stability analysis

The increased penetration of renewables and the variable behavior of solar irradiation makes the energy storage important for overcoming several stability issues that arise in the power network. The current paper examines the design and stability analysis of a grid-connected residential photovoltaic (PV) system with battery–supercapacitor hybrid energy storage. The battery and supercapacitor packs are connected to the common 400 V DC-bus in a fully active parallel configuration through two bidirectional DC–DC converters, hence they have different voltage levels and their power flow is controlled separately. A detailed small-signal stability analysis is considered for the design of the current controllers for the bidirectional converters of the battery and supercapacitor. An important contribution here is that a detailed stability analysis is performed for both the boost and the buck mode of operation for the battery and supercapacitor converters, resulting in more accurate tuning of the controllers. Moreover, the small-signal stability analysis of the voltage source inverter (VSI) is considered in order to design the DC-bus voltage controller, where a reference output current is obtained using a phase-locked loop (PLL) for grid synchronization. The proposed model is developed and simulated in the MATLAB/Simulink software environment, based on mathematical analysis and average modeling. The simulation results verify the dynamic performance of the proposed model, through several rapid changes in PV generation and in load demand. Also, the model works properly and responds extremely fast during different mode transitions, exhibiting a very fast DC-bus voltage regulation with a very small ripple voltage (a maximum of ± 0.625%). Finally, the supercapacitor handles the rapid changes occurring within 0.2 s, hence this can relieve the battery stress and extend the battery lifetime.

Bidirectional Battery Interface in Standalone Solar PV System for Electrification in Rural Areas

In a standalone photovoltaic (PV) system, a bidirectional DC converter (BDC) is needed to prevent the battery from damage caused by DC bus voltage variation. In this paper, BDC was applied in a standalone solar PV system to interface the battery with a DC bus in a standalone PV system. Therefore, its bidirectional power capability was focused on improving save battery operation while maintaining high power quality delivery. A non-isolated, buck and boost topology for the BDC configuration was used to interface the battery with the DC bus. PID controller-based control strategy was chosen for easy implementation, high reliability, and high dynamic performance. A simulation was conducted using MATLAB Simulink program. The simulation results show that the implementation of the BDC controller can maintain the DC bus voltage to 100 V, have high efficiency at 99.18% in boost mode and 99.48% in buck mode. To prevent the battery from overcharging condition, the BDC stops the charging process and then works as a voltage regulator to maintain the DC bus voltage at reference value.

Design of Energy Storage Photovoltaic Power Generation Device and Neural Network Method for Photovoltaic Power Prediction

The series-parallel combination of the photovoltaic array can meet the needs of different applications such as high power or low power with the continuous optimization of photovoltaic cell materials and the increasing improvement on efficiency of photovoltaic cell. This exploration takes the independent photovoltaic power generation (PPG) device as the research goal. The system includes a photovoltaic array, Boost rectifier, single-phase photovoltaic inverter, battery and bi-directional DC/DC converter. Single-phase photovoltaic inverter is employed for the AC load power supply, and a lead-acid battery is adopted for energy storage. Buck mode and Boost mode are modeled respectively based on the analysis of the converter topology, and the designed model is employed to control the converter. Back propagation neural network (BPNN) is introduced to analyze the factors which can affect the output power of PPG. In experiment, the effective value of output voltage, output voltage, and current waveform of single-phase inverter are analyzed. The analysis results show that the output voltage changes suddenly with the load, and the device can be followed again within a few milliseconds, which means that the device has good dynamic performance. The corresponding output frequency fluctuates at a small amplitude (±1%) when the output voltage is above 220 V. Meanwhile, the distortion of the output waveform is less than 1%. The ripple coefficient of the output voltage is less than 1% when the operating mode of PPG (boost and Buck) is changed. The neural network is introduced to select the appropriate parameters (irradiation intensity, relative humidity, ambient temperature and wind speed), and the results show that the environmental temperature exerts a great influence on the output power of PPG.

간단한 듀티비 제어 기법에 의한 quasi Z-소스 동적전압보상기

The quasi Z-source dynamic voltage restorer using the conventional switching scheme was able to obtain only the compensation voltage in the out of phase buck-boost mode for voltage swell compensation of the power source and the in-phase boost mode compensation voltage for more than 50% voltage sag compensation. Since this method cannot compensate for the voltage sag of 1-50%, which mainly occurs in industrial fields, a method of connecting additional quasi Z source converter in series and parallel was studied. In this study, a simple duty ratio scheme was proposed which is can be operated as an out of phase buck boost mode to compensate for swell, an in-phase boost mode to compensate for sag of 50% or more and an in-phase buck mode to compensate for sag of 1-50%. In order to prove the validity of this study, PSIM simulation and DSP based experiment were performed. As a result, by the proposed duty ratio control scheme, it was possible to compensate both the in-phase buck boost mode and the out of phase buck boost mode for sag and swell with a single quasi Z-source dynamic voltage compensator. Finally, for each load of 50Ω and 100Ω even if the voltage sag and swell were generated step by step by 10%, the voltage compensation rate remained almost 1, and the THD of the voltage was all good at 5% or less.

Optimasi Battery Charging pada Pendingin Minuman dengan Sumber Solar Cell untuk Beban Peltier Menggunakan Buckboost Converter

Currently, many electronic devices use the energy source from the solar cell which is stored in a battery. The battery is a portable, rechargeable power source. Solar energy is very suitable when converted to electrical energy because the amount of sunlight is infinite even though there is a period of time between sunrise and sunset. Converting solar energy to electrical energy requires a solar cell. One method that can be done is using the buck boost converter method with solar cell sources to create a battery charging control system. The Buck Boost Converter method was chosen because it can stabilize the output voltage from the solar cell when the weather is uncertain. If the light intensity of the sunlight is dim, the output voltage of the panel will also be low, then the converter will be in boost mode to increase the voltage level, on the other hand, if the light intensity of the panel output voltage will also be high, the converter will be in buck mode to lower the voltage level. The output voltage of this control system is maintained according to the battery charging voltage standard, which is 14 volts DC.

Control of Three Phase BLDC Motor for Electric Vehicles by using Four Quadrant Operation

In this paper the four quadrant operation implemented for the recovery of electric vehicles. BLDC motor is used in EV, and bi-directional DC-DC converter is connected to the VSI (voltage source inverter). Bi-directional DC-DC converter performed to modes that is, buck mode and boost mode, energy is recovered through this mode. In buck mode utilized the energy for drive the motor and in the boost mode regeneration of energy and charged the battery. This proposal operated in MATLAB\Simulink software. By using this method we can improve the energy management of electric vehicles when vehicles in motoring mode bi-directional converter did buck operation and utilized energy for driving vehicles. During electric vehicles often start and stop, this operation proposes recovery of kinetic energy of motor and stored it in battery through the regenerative braking. Through electric vehicles going on downhill, drive speed develops more than reference speed, controlled speed offer energy and this energy return to battery.

간단한 듀티비 제어에 의한 quasi Z-소스 교류 컨버터의 4상한 전압제어 기법

When controlling the output voltage of a quasi-Z-source AC converter, the conventional switching method can only obtain the output voltage of in-phase boost mode and out-of-phase buck boost mode. Therefore, a cascade connection method of an additional quasi-Z-source AC converter was studied to obtain the in-phase buck voltage required in the industrial field. Since this method uses two converters, the hardware is bulky and there are problems such as resonance. In this study, we propose a simple duty ratio control method that can operate in the in-phase buck mode in addition to the in-phase boost mode and the out of phase buck-boost mode without additional quasi Z source AC converter. To verify the validity of this study, PSIM simulations and experiments were performed. As a result, the proposed method can operate not only in the in-phase boost and out of phase buck-boost modes, but also in the in-phase buck mode, and the output voltage is kept constant in the transient state of a sudden load change. Finally, the input power factor and efficiency are more than 90% in most areas when operating in the in-phase mode, but relatively low in the out of phase mode.

Discontinuous conduction mode Buck converter with high efficiency

Discontinuous conduction mode Buck converter with high efficiency

Grid‐connected buck–boost inverter without shoot‐through issue and with reduced voltage stress

SummaryGrid‐connected buck–boost inverters are used in wide input‐voltage range application. However, there is a shoot‐through problem in traditional grid‐connected inverters. Moreover, voltage stress of semiconductors is high in conventional buck–boost inverters. Therefore, a grid‐connected buck–boost inverter without shoot‐through issue and with reduced voltage stress is presented. The proposed inverter is a single‐stage system. When input voltage is higher than the grid voltage, the proposed inverter works in buck mode; when input voltage is lower than the grid voltage, it operates in boost mode. Thus, voltage stress of semiconductors is reduced. Only one switch is operated in high frequency in each period, so efficiency of the inverter can be improved. Operating principle of the proposed inverter is illustrated. Voltage stress analysis, loss calculation, and filter design guidelines and example are given. Finally, simulation and experimental results of a 300‐W proposed inverter confirm the theoretical analysis.

A flux estimation method for three‐phase dual‐active‐bridge DC/DC converters

This study proposes an estimation method of flux density in high-frequency transformers of three-phase dual-active-bridge transformers. The steady-state analysis shows that the flux in the converter is different in Buck and Boost modes and depending on load and voltage gain condition. From that, a closed-form formula is proposed to estimate the flux swing in the core. Unlike the conventional estimation technique, the proposed one represents the flux as a function of input and output voltages and the phase shift value. Finite element analysis confirms that the proposed formula can predict the flux with less than 4% error. The proposed formula can also help to improve the prediction of temperature profile of the transformers with a high accuracy of less than 1 degree Celsius in the mid- to high-power range as validated in experiments. The proposed flux estimation method can be used in designing the converter or in predicting the converter behaviour under critical conditions such as load changing or starting, and so forth, to help protect the transformers from saturation or DC bias.

Twenty-Five Years of Single-Stage Buck–Boost Inverters: Development and Challenges

Single-stage buck&#x2013;boost inverters have overcome the shortcomings posed by conventional voltage source inverters (VSI) and current source inverters (CSI). VSIs can produce only ac waveforms with a value less than or equal to the applied dc-link voltage (the buck mode), and CSIs can produce only ac waveforms with values greater than or equal to the applied dc-link voltage (the boost mode). On the other hand, single-stage buck&#x2013;boost inverters can provide a stepped-up/down output voltage, thus accommodating a wide input voltage range. The literature claims single-stage buck&#x2013;boost inverters are more efficient, less bulky, and able to operate across a wide input voltage range. So why does the industry still love conventional VSIs with a back-ended dc&#x2013;dc converter or a step-up transformer?

Wide input/output control strategy for multiphase series capacitor bidirectional DC–DC converters

The series capacitor converter is one kind of high-gain bidirectional DC–DC converter based on interleaved and switched capacitor techniques. For the n-phase series capacitor converter, n times voltage gain when compared with the traditional boost converter under a specific duty cycle, as well as automatic current sharing among phases can be achieved. The specific duty cycle is (n − 1)/n to 1 in the boost mode and 0 to 1/n in the buck mode, which means that it is not suitable for wide input and/or wide output applications. To solve this issue, an 180° interleaved switching strategy is proposed in this paper. The proposed strategy is more suitable for converters to widen the working duty cycle range. The working principle, voltage gain and current distribution/sharing characteristics with the duty cycle ranging from 0 to 1 are analyzed and calculated in greater detail. In addition, as one of the n-phase series capacitor converters, a small signal model of a three-phase series capacitor converter is built, and a dual closed-loop controller is studied and designed. Finally, an experimental prototype with an input voltage that varies from 10 to 30 V and an output voltage of 100 V is built and tested. Results obtained with the prototype verify the correctness of the proposed switching strategy.