Bidirectional AC-DC Research Articles

Instantaneous-Power-Balance-Based Modulation With Natural Power Factor Correction for Single-Stage Bidirectional AC–DC DAB Converter

Instantaneous-Power-Balance-Based Modulation With Natural Power Factor Correction for Single-Stage Bidirectional AC–DC DAB Converter

Controlling of Solar Based Electric Vehicle Charging Station Through Intelligence Controller for G2V and V2G Modes

Abstract: Solar based electric vehicle (EV) charging station was proposed in this paper. The maximum power of a PV module varies due to changing temperature, solar radiation, and load. In order to extract the Maximum power point in this work, an MPPT system consisting of a PV module, a DC-DC converter, and a fuzzy logic controller is designed and simulated in Simulink. The EV battery SOC characteristic is observed to be fully charged within short period. In this paper single Phase grid and the PV system with the Fuzzy controller MPPT is connected to the DC link, which is connected to the EV. Also in the absence of solar PV energy, electric vehicle is charged from the grid. A battery of rating 100AH is charged with the solar PV panel using a boost converter which generates output voltage of 400V. Then the voltage is stepped down for buck operation according to 220 V battery requirement. A Bidirectional AC-DC rectifier is connected to the Grid, and the DC-DC boost converter for the MPPT and the DC-DC bidirectional Converter is connected to the EV for the Charging and Discharging of the EV. During charging and discharging modes the battery voltage and current is presented. It is clear that the grid voltage and current are in phase during charging. During discharging they are said to be out of phase indicating the reverse power flow.

Application and practice of portable bi-directional DC-AC energy storage converter based on second order generalized integrator phase-locked loop and HERIC circuit

In various industries, including the production of new energy and electric vehicles, portable bidirectional converters are crucial for enhancing power supply reliability. In recent years, these converters have become increasingly normal in daily life. Bidirectional converters have not been as popular or have not been used as much due to issues with phase tracking on grids connected to leakage current in the converter system. The essential features and principles of the portable bidirectional energy storage converter proposed in this paper, which is based on a second-order generalized integrator phase-locked loop, are theoretically investigated. Formulas are also generated using small signals to address this issue. PLECS simulation software was used for parameter design and algorithm simulation to test the effectiveness of the phase-locked loop under various operating situations. Therefore, a set of appropriate phase-locked structure models for this circuit was developed. An experimental verification platform was constructed to confirm the accuracy of the design parameters: the front stage uses the H-bridge; the backstage, which uses the front stage, adopts the H-bridge; and the rear stage adopts the topology platform of the HERIC topology + LCL filter circuit. The test data indicates that, the addition of the HERIC topology and soft switching resulted in a 94 % reduction in leakage current and a 1.6 % improvement in efficiency. Analysis and comparison results of the test data confirmed the consistency between the experimental effect and the design parameters, achieving the expected effect and proving the accuracy of the topology and mathematical model. The design methodology and design parameters of this thesis are useful and instructive for similar or related research.

Dynamic load reference based DQ-axis synchronous frame control method of grid connected PV hybrid microgrid

The hybrid AC-DC microgrid is a system that links AC and DC microgrids using a bidirectional AC-DC interface converter. The presence of dynamic loads is a major obstacle to the implementation of the microgrid concept, and those 50 % include asynchronous motors. This paper presents a control system for a hybrid microgrid that powers an electrical motor using the field-oriented control (FOC) method. This study investigates the significance of third-harmonic injected PWM (THIPWM) in reducing the necessary voltage across the DC bus while still achieving the required AC voltage at motor terminals. MATLAB/Simulink simulation tool and OPAL-RT for real-time simulations were used for validation of the proposed control. The outcomes show the tracking of the reference currents, achieving accurate torque control, managing various operating modes like grid-connected having SPWM and THIPWM, or operation with PV and battery sources. The research also highlights lower settling time values as well as lower total harmonic distortion (THD) compared to SPWM in different load conditions using THIPWM.

Intelligent Integration of Vehicle-to-Grid (V2G) and Vehicle-for-Grid (V4G) Systems: Leveraging Artificial Neural Networks (ANNs) for Smart Grid

This paper presents a groundbreaking control strategy for a bidirectional battery charger that allows power to be injected into the smart grid while simultaneously compensating for the grid’s reactive power using an electric vehicle battery. An artificial neural network (ANN) controller is utilized for precise design to ensure optimal performance with minimal error. The ANN technique is applied to generate sinusoidal pulse width modulation (SPWM) for a bidirectional AC–DC inverter, with the entire algorithm simulated in MATLAB Simulink.The core innovation of this study is the creation of the ANN algorithm, which supports grid compensation using electric vehicle batteries, an approach termed “vehicle-for-grid”. Additionally, the paper details the PCB circuit design of the system controlled by the DSP F28379D board, which was tested on a three-phase motor. The total harmonic distortion (THD) of the proposed ANN algorithm is approximately 1.85%, compared to the MPC algorithm’s THD of about 2.85%. This indicates that the proposed algorithm is more effective in terms of the quality of the power injected into the grid. Furthermore, it demonstrates effective grid compensation, with the reactive power effectively neutralized to 0KVAR in the vehicle-for-grid mode

Advanced Grid Connectivity Using Hybrid Solar, Wind, and Battery Technologies

Global warming has led to the proliferation of electric vehicles, which seem to be the best option for internal combustion engines. With so many electric cars on the road, it's not practical or economical to charge cars using traditional power lines. Using renewable energy when charging stations control the electric vehicle. The project describes the charging system (SWCM) based on solar energy (250W), 15 modules in series and 2 parallel in series, and wind power (5.78kW) to generate electricity to charge the battery of the EV (electric vehicle). The regenerative charging station consists of wind turbines and PV (solar photovoltaic) modules. Charging mechanisms based on wind energy reduce CO2 and CO2-related emissions by reducing the need for fossil fuels to generate electricity. EV (electric vehicle) charging stations containing solar, wind, grid and BESS (battery energy storage systems) are designed according to the current situation. Additional grid support is also assumed to provide uninterrupted power to the charging stations without placing additional load on the grid. To balance the requirements, the system is connected to the grid via a three-phase bidirectional DC-AC (alternating current) frequency converter. The results show that the regenerative power generator is suitable for charging electric vehicles and creating a Pollution-free environment. The results are demonstrated with a MATLAB simulation run.

Bi-directional DC-AC using BLDC motor for electric and hybrid electric vehicles applications with reduced number of switches

Electric scooters often have a single design and are difficult to produce at a greater level than other forms of transportation. A possible cut electric scooter is built with the optimization design of the vehicle combustible wealth and the pollution characteristics in order to arrange to a correct solution by resolving each and every challenge. The engines' electrical systems are comprised of lead acid batteries. For the sake of a straightforward simulation procedure, the engine operates in two states ON and OFF while the vehicle's speed is regulated in three ranges roughly corresponding to high, medium, and low. The planetary speed ratio and the final drive speed ratio are gathered in the computation method's general outline. Utilizing simulation MATLAB, the findings of optimization strategies are resolved. This technique improves the fuel plenty and discharge quality of the possibility cut electric automobiles.

An Asymmetric Full-Bridge Bidirectional DC–AC Converter With Power Decoupling and Common-Mode Current Suppression for V2G Application

An Asymmetric Full-Bridge Bidirectional DC–AC Converter With Power Decoupling and Common-Mode Current Suppression for V2G Application

Modified EPS Control and Topology Modification for Two-Stage Bidirectional AC-DC Converter for V2G Applications

Abstract For the two-stage bidirectional AC-DC converter applied to vehicle-to-grid (V2G), this paper studies the modulation strategy and the topology of the dual active bridge (DAB) converter in the DC-DC stage. Aiming at the problem of large circulating current due to the fixed internal phase shift under the traditional extended phase shift (EPS) control, this paper modified the EPS modulation strategy by deciding whether the internal phase shift is generated by the primary or secondary side based on the voltage gain, which realizes the high-efficiency power transfer under wide voltage gain. To realize the full load range zero voltage switching (ZVS) with junction capacitors taken into account, it is proposed to parallel an additional auxiliary inductor between the bridge arms of the DAB converter, and the operating mechanism and the improved effect are analyzed in detail. Finally, a simulation circuit was built using PSIM software to verify the correctness.

Nonlinear Modeling and Control Strategy Based on Type-II T-S Fuzzy in Bi-Directional DC-AC Converter

Bi-directional DC-AC converters are widely used in the field of electric vehicle-to-grid. However, the inductance of the grid-side interface filter is affected by the length of the grid connection and the power level, which presents nonlinear characteristics. This poses challenges for high-performance grid waveform control. In this paper, a modeling method for bi-directional DC-AC grid-connected converters based on type-II T-S fuzzy models is proposed, and the corresponding type-II T-S fuzzy control strategy is designed to address the parameter uncertainty and non-linearity issues. Simulation results show that type-II T-S fuzzy control offers superior control performance and better current waveform quality compared to type-I T-S fuzzy control under uncertainty parameter conditions. The effectiveness of the proposed strategy is further validated through a 1 kW prototype of a bi-directional DC-AC converter.

Novel DC-link voltage regulation and seamless transfer control strategy of a battery-based microgrid system

The main challenge of modern microgrids (MGs) is the capability to operate in either grid-connected mode (GC) or islanding (IS) mode with DC-link voltage regulation for all the utilized parallel-connected DC-AC converters in the MG during all operating modes and, at the same time, is capable of transferring seamlessly between these two operating modes. This paper suggests a novel control strategy capable of operating a battery-based MG system in each of the GC and the IS modes and, at the same time, seamlessly transferring it between these two operating modes. A PQ controller is utilized to realize the GC operation, whereas a V/f controller is used for the IS operation. The smooth transfer between the two modes is accomplished by minimizing the transient variations in the MG voltage, current, frequency and phase at the point of common coupling (PCC). Additionally, the suggested strategy is qualified to deliver a novel regulation and a transient-free transition for the DC-link voltage of the used bi-directional DC-AC converter of the considered battery-based MG system. Therefore, the suggested control strategy can potentially improve the reliability of the considered battery-based MG system. The considered battery-based MG system is simulated and controlled by utilizing MATLAB/Simulink. The simulation results demonstrate that the suggested control strategy can effectively act during the operation of the considered battery-based MG system, either in the GC mode or the IS mode, and it can also effectively control the transitions between the two operating modes.

Design of a bidirectional EV charger using unit template-based current-controlled synchronous reference frame hysteresis

Abstract Existing distribution networks were not designed with large-scale electric vehicle (EV) charging infrastructure in mind. Integrating EV charging stations with the distribution grid might lead to power quality (PQ) issues at the point of common coupling (PCC). This work proposes a two-mode, unit template-based synchronous reference frame hysteresis current-controlled (SRF-HCC) three-phase Level 2 EV charger. Mode one focuses on charging the EV battery from the grid (G2V) and utilizes current and voltage control techniques to enhance battery life and performance. Whereas mode two enables the EV’s stored energy to be discharged to the grid (V2G) by the EV user, allowing the sale of power to support the transient effect of the grid voltage and frequency and enhancing the grid’s PQ. The HCC generates switching pulses for both the AC-DC and buck-boost converters. The SRF-based unit template-based control (SRF-UTC) method ensures system stability, voltage, and frequency regulation for power exchange with the grid by combining its efficiency with that of the HCC. The EV charger proposal comprises three primary components: a 3-phase bidirectional AC-DC converter, a bidirectional buck-boost converter, and a filter circuit. The proposed system was modeled using MATLAB/Simulink and evaluated in two case studies to assess its performance.

A Bidirectional Grid-Friendly Charger Design for Electric Vehicle Operated under Pulse-Current Heating and Variable-Current Charging

Low-temperature preheating, fast charging, and vehicle-to-grid (V2G) capabilities are important factors for the further development of electric vehicles (EVs). However, for conventional two-stage chargers, the EV charging/discharging instructions and grid instructions cannot be addressed simultaneously for specific requirements, pulse heating and variable-current charging can cause high-frequency power fluctuations at the grid side. Therefore, it is necessary to design a bidirectional grid-friendly charger for EVs operated under pulse-current heating and variable-current charging. The DC bus, which serves as the medium connecting the bidirectional DC–DC and bidirectional DC–AC, typically employs capacitors. This paper analyzes the reasons why the use of capacitors in the DC bus cannot satisfy the grid and EV requirements, and it proposes a new DC bus configuration that utilizes energy storage batteries instead of capacitors. Due to the voltage-source characteristics of the energy storage batteries, EV instructions and grid instructions can be flexibly and smoothly scheduled by using phase-shift control and adaptive virtual synchronous generator (VSG) control, respectively. In addition, the stability of the control strategy is demonstrated using small signal modeling. Finally, typical operating conditions (such as EV pulse preheating, fast charging with variable current, and grid peak shaving and valley filling) are selected for validation. The results show that in the proposed charger, the grid scheduling instructions and EV charging/discharging instructions do not interfere with each other, and different commands between EVs also do not interfere with each other under a charging pile with dual guns. Without affecting the requirements of EVs, the grid can change the proportion of energy supply based on actual scenarios and can also obtain energy from either EVs or energy storage batteries. For the novel charger, the pulse modulation time for EVs consistently achieves a steady state within 0.1 s; thus, the pulse modulation speed is as much as two times faster than that of conventional chargers with identical parameters.

Bidirectional DC-AC converter for photovoltaic solar system in Home Electrical Networks

This paper presents the results obtained in the design, implementation and testing of a bidirectional CSI (Current source inverter) converter, which is capable of delivering and taking power from the grid to charge a 72 V battery bank. This converter is sized within a photovoltaic solar system designed for homes in the city of Tunja, based on real data to estimate the average consumption of a typical home in the "Cooservicios" sector of the city, proposing two ways of working the system, one to obtain a constant average consumption and another in which the total consumption is zero. The converter is implemented with all its components, digital and power stages, using for the control a TMS 320F28377S microcontroller from C2000 family, of Texas Instruments. The implementation meets specifications of: bidirectional operation as an inverter and as a rectifier, output power of 469 W, efficiency around 80%, highlighting the considerably high value required for the input inductance of 0.3 H that causes losses in the system.

Voltage-Oriented Control-Based Three-Phase, Three-Leg Bidirectional AC–DC Converter with Improved Power Quality for Microgrids

Renewable energy sources (RESs) and energy storage schemes (ESSs) integrated into a microgrid (MG) system have been widely used in power generation and distribution to provide a constant supply of electricity. The power electronics converters, particularly the bidirectional power converters (BPCs), are promising interfaces for MG infrastructure because they control the power management of the whole MG system. The controller of BPCs can be designed using several different control strategies. However, all the existing controllers have system stability, dynamics, and power quality issues. Therefore, this study demonstrates the development of an LCL-filtered grid-connected bidirectional AC–DC converter’s (BADC) control strategy based on voltage-oriented control (VOC) to overcome these issues. The proposed VOC-based inner current control loop (ICCL) is implemented in synchronous dq-coordinate with the help of proportional-integral (PI) controllers. An observer-based active damping (AD) is also developed in order to estimate the filter capacitor current from the capacitor voltage instead of directly measuring it. This developed AD system helps to damp the resonance effect of the LCL filter, improves system stability, and also eliminates the practical challenges of measuring capacitor current. The proposed controller with AD is able to realize bidirectional power transfer (BPT) with reduced power losses due to the elimination of passive damping and improved power quality, system dynamics, and stability. The mathematical modeling of the suggested system was developed, and the structure of the system model was established in the MATLAB/Simulink environment. The performance of the proposed system was validated with real-time software-in-the-loop (RT-SIL) simulation using the OPAL-RT simulator for a 16 kVA converter system. The real-time (RT) simulation results show that the BADC with the proposed control scheme can provide better dynamic performance and operate with tolerable total harmonic distortion (THD) of 2.62% and 2.71% for inverter and rectifier modes of operation, respectively.

Analysis and Design of an Integrated Bidirectional Three-Phase AC–DC Resonant Converter

This paper proposes a novel isolated bidirectional AC-DC converter where the front end and primary side of DC-DC isolated converter are merged giving rise to 25&#x0025; fewer devices. Owing to the integrated topology the devices of the proposed converter are naturally soft switched and the size of the filtering components in the AC-DC stage is reduced compared to a low frequency hard switched AC-DC stage. A Space Vector Modulation (SVM) and control technique is proposed for generating switching pulses for DC link voltage control and bidirectional power transfer. A design optimization technique is proposed to mathematically determine the switching frequency of the converter and subsequently, the resonant tank parameters based on the operating conditions, topology, modulation, and the Wide Band Gap (WBG) Silicon Carbide (SiC) device characteristics. The proposed converter and its design approach are validated through prototyping for a scaled-down bidirectional charger for warehouse Electric Vehicles (EVs), and experimental results from two test cases, one with the actual grid with an input ac line (<i>i.e.,</i> 208&#x00A0;V) voltage and second with an AC power supply of input line (<i>i.e.,</i> 400&#x00A0;V) voltage. The former is tested for a peak power rating of 2.5&#x00A0;kW and the later is tested for a 5&#x00A0;kW output power. The switching frequency from the proposed optimization method is determined to be around 130&#x00A0;kHz for both cases. Peak efficiency of 95.3&#x0025; is achieved. The battery voltage varies from 350-600&#x00A0;V.

A High-Efficiency Bidirectional Single-Stage AC-DC Converter Under Wide Voltage Range for Fast Chargers

In this article, a single-stage four-phase interleaved totem-pole AC–DC converter for fast charger applications that require high power, wide battery voltage range, and bidirectional operation capabilities is proposed. Due to the four-phase interleaving effect, the grid side switches can operate at duty cycle of 0.25 or 0.5 so that the grid current always achieves ripple-free. A method for secondary side duty cycle generation is proposed for reducing the circulating power and input current total harmonic distortion (THD) under a wide voltage range. The control system is shown to be simple and reliable. An integrated four-phase transformer is designed using one core. Experimental results from a 7.5 kW prototype with an output voltage range of 150 to 750 V are provided to validate the proposed concept.

A Bidirectional Isolated Dual-Phase-Shift Variable-Frequency Series Resonant Dual-Active-Bridge GaN AC–DC Converter

This article presents a novel single-stage series resonant dual-active-bridge (SR-DAB) for grid-con- nected bidirectional ac–dc energy storage applications. The single-phase SR-DAB is connected to the grid with an unfolding bridge on the ac side. Three SR-DABs are utilized to connect to a three-phase grid. A control scheme that combines dual-phase shifts and variable frequency is proposed to achieve zero voltage switching and power factor correction over a wide range of ac and dc voltages and loads. A series of comparisons in terms of inductor root mean square current, turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> current of all transistors are conducted at different loads to prove the advantage of the proposed converter over the traditional dual-active-bridge-based ac/dc converter. A GaN-based hardware prototype connecting the 480Y/240/208 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> three-phase grid to a 48-V battery was developed with a peak efficiency of 97.2%.

A Boost-Inductorless Electrolytic-Capacitorless Single-Stage Bidirectional Isolated AC–DC Converter

With the development of wide-bandgap devices, bidirectional isolated ac–dc converter becomes an attractive solution to realize highly compact, highly efficient power conversion for electric vehicle (EV) chargers and energy storage applications. However, in the existing literature, regardless of two-stage or single-stage isolated ac–dc converters, the circulating current in boost inductors is inversely proportional to the inductance value, resulting in large volume and high loss of the converter. In this article, a boost-inductorless electrolytic-capacitorless single-stage bidirectional ac–dc converter with high-frequency isolation is proposed. With the introduction of a center-tapped transformer, the proposed converter can achieve nearly zero circulating current without any boost inductor, thus overcoming the drawbacks mentioned above. Equivalent circuit analysis is applied to illustrate the operation principle and advantages of the proposed topology. A detailed comparison between the proposed topology and the state-of-the-art is also provided. The experimental results obtained from a 3.6 kW, 140 kHz single-phase EV charger prototype are given as the proof-of-the-concept. It is demonstrated that the proposed converter prototype realizes a peak efficiency of 96.4% with only 38 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> H total inductance and 6.33 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> F total capacitance.

A SWISS-Rectifier-Based Single-Stage Three-Phase Bidirectional AC–DC Inductive-Power-Transfer Converter for Vehicle-to-Grid Applications

Three-phase bidirectional ac–dc inductive power transfer (IPT) systems for vehicle-to-grid applications are conventionally based on a two-stage architecture. However, poor conversion efficiency, high component counts, and high control complexity are distinct disadvantages. Even though a few single-stage ac–dc IPT systems based on matrix-type converters were proposed, it remains a challenge for achieving sinusoidal input current, zero-voltage switching, and high efficiency simultaneously. In this article, a new single-stage three-phase bidirectional ac–dc IPT converter is proposed. The proposed converter is based on a newly proposed multi-active-bridge converter coupled to a SWISS front end. As a result, the proposed converter inherits not only the merits of low distortion of input current, high efficiency, and output short-circuit protection, but also achieves soft-switching operation resulting from the proposed modulation strategy and the property of the double-sided <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> compensation network. The operating principle and mathematical analysis of the proposed converter are discussed. Experimental results are presented to verify the performance of the converter.