Input Voltage Fluctuation Research Articles

Novel Droop-Based Techniques for Dynamic Performance Improvement in a Linear Active Disturbance Rejection Controlled-Dual Active Bridge for Fast Battery Charging of Electric Vehicles

Electric vehicles (EVs) are rapidly replacing fossil-fuel-powered vehicles, creating a need for a fast-charging infrastructure that is crucial for their widespread adoption. This research addresses this challenge by improving the control of dual active bridge converters, a popular choice for high-power EV charging stations. A critical issue in EV battery charging is the smooth transition between charging stages (constant current and constant voltage) which can disrupt converter performance. This work proposes a novel feedforward control method using a combination of droop-based techniques combined with a sophisticated linear active disturbance rejection control system applied to a single-phase shift-modulated dual active bridge. This combination ensures a seamless transition between charging stages and enhances the robustness of the system against fluctuations in both input voltage and load. Numerical simulations using MATLAB/Simulink R2024a demonstrated that this approach not only enables smooth charging but also reduces the peak input converter current, allowing for the use of lower-rated components in the converter design. This translates to potentially lower costs for building these essential charging stations and faster adoption of EVs.

Research on Cascaded On‐Board DC/DC Converter Based on Three‐Phase Interleaved LLC

ABSTRACTThe on‐board DC/DC converter proposed in this research consists of a Buck converter and a three‐phase interleaved LLC resonant converter. This paper analyzes the average current and output current ripple characteristics of the rear‐stage converter in addition to explaining the topology and working principles of the front‐stage Buck converter and the rear‐stage three‐phase interleaved LLC resonant converter. To establish a single‐phase fundamental equivalent circuit for the rear‐stage converter, apply the fundamental wave analysis method, and it is essential for comprehending the impact of relevant system parameters on voltage gain characteristics and resonant operating regions. Conducting research on the two‐stage on‐board DC/DC converter's control strategy involves establishing small‐signal circuit models for both front and rear stage converters, derivation of parameters for double closed‐loop control, and determination of the control strategy employing phase‐shifted current sharing for the rear‐stage converter in cases where significant tolerance exists in resonant components. The simulation for a two‐stage on‐board DC/DC converter results indicates that under various conditions of resonant component tolerance, the converter is capable of achieving balanced phase currents and demonstrates minimal output current ripple prior to capacitor filtering. A 1.5‐kW experimental prototype has been fabricated, and the experimental findings indicate that the output voltage remains stable at 13.8 V despite fluctuations in input voltage. The highest efficiency of the prototype is about 96.27%, and the utilization of phase‐shifting current balancing control results in a notable reduction in output current ripple. This provides more evidence that the design of a two‐stage on‐board DC/DC converter is correct.

Reflux Power Optimization of a Dual-Active Hybrid Full-Bridge Converter Based on Active Disturbance Rejection Control

The dual-active hybrid full-bridge (H-FDAB) DC–DC converter has great potential in medium-voltage high-power photovoltaic power station applications by introducing a three-level bridge arm to increase the output voltage range. However, its mathematical model and optimum modulation schemes have not been fully explored. Under the traditional PI control, the H-FDAB DC–DC converter will produce significant reflux power, which will lead to a decrease in converter efficiency and output voltage fluctuation. On this basis, this paper proposes a reflux power optimization strategy for an H-FDAB DC-DC converter based on active disturbance rejection control (ADRC). Firstly, the structure and power characteristics of the H-FDAB DC–DC converter are analyzed, and the relationship among the reflux power, the transmission power, and the phase shift angle is derived. Secondly, to reduce the complexity of the control calculation, upon the foundation of dual phase-shifting modulation, the Karush–Kuhn–Tucker (KKT) condition is used to solve for the phase shift angle that corresponds to the minimum reflux power. Simultaneously, we develop an ADRC loop utilizing an extended state observer (ESO) for the real-time estimation of system states. We also consider the sudden changes in input voltage, load switching, and transmission power fluctuations caused by reflux power optimization strategies as system disturbances and compensate for them accordingly. Finally, the experiments conclusively validate the designed control strategy’s correctness and feasibility.

Pure sine wave generation in battery-less solar system using advanced control through single machine

Due to the reduction of conventional energy sources, humanity faces a critical challenge, forcing innovative solutions to bridge the growing gap between energy demand and supply. Solar energy has emerged as a promising alternative, owing to its efficiency and renewable nature. Despite their benefits, conventional solar power systems face many challenges, including their reliance on battery banks, which introduce complexities and inefficiencies, such as voltage fluctuations and harmonic content. To overcome these challenges, researchers propose a novel solution: the Dual Winding Machine (DWM). This innovative system integrates motor and generator functionalities within a single machine, operating on a dual stator core to achieve synchronous operation. In contrast to traditional setups, the DWM eliminates the need for batteries during periods of low solar energy. A crucial component in this novel approach is the utilization of a Zeta converter, which adjusts the switching frequency to regulate the DC voltage and machine terminals. By doing so, the DWM maintains a constant voltage supply without relying on a battery, mitigating the fluctuations observed in traditional solar power systems. The proposed solution offers several benefits over existing strategies. Firstly, by eliminating the need for a battery, the DWM reduces system complexity and enhances overall efficiency. The absence of a battery backup also minimizes the risk of fluctuations in the inverter's input voltage and mitigates potential increases in output harmonic content. This not only improves the reliability of the solar power system but also extends the lifespan of connected machinery, such as motors and electrical devices. Furthermore, simulations conducted using MATLAB and MAXWELL programs validate the effectiveness of the DWM, confirming its ability to generate harmonic-free sine waves without relying on a battery, thus representing a significant advancement towards more sustainable and reliable solar energy solutions. In summary, the DWM presents a promising solution to the challenges faced by conventional solar power systems, offering improved efficiency, reliability, and longevity.

Design of 3-level LLC converter voltage controller for wide input voltage fluctuations

The auxiliary power supply unit for railway vehicles delivers various power to the passenger car. Maintaining isolation between the catenary power line and the auxiliary power in the compartment is typically essential. To ensure electrical isolation, an efficient LLC resonant converter is utilized among isolated DC-DC converters. Generally, LLC resonant converter primarily employ PFM control method. However, there is a limitation in increasing the switching frequency at high input voltages, making it difficult to handle wide input voltage fluctuations from the overhead catenary power line. To overcome this limitation, the PFM control method is introduced alongside the existing PFM control method, resulting in the presence of two controllers. However, since these two controllers regulate the output voltage differently, there is a potential for output voltage overshoot due to significant input voltage fluctuations. This paper proposes a method that combines PFM and PWM controllers, along with feed-forward compensation, to address these issues. The effectiveness of this proposed method is validated through PSIM simulation and experimentation.

Stabilization of constant power loads and dynamic current sharing in DC microgrid using robust control technique

DC microgrids are appealing in distribution networks due to their high efficacy, stability, and ease of incorporation with renewable energy resources. In order to maintain system reliability, load sharing is crucial, because disturbances such as the constant power load (CPL), constant voltage load (CVL), uncertainty parameters, and variations in input voltage may result in instability. The conventional droop control method has been frequently employed to regulate the DC microgrid. However, under significant disturbances, conventional droop control is not suitable for achieving both accurate current sharing and acceptable voltage regulation. To tackle these limitations, this paper introduces a robust control for sharing load current and regulating DC bus voltage in a DC microgrid feeding a CPL and CVL. The proposed approach is split into two loops. The main loop, which is based on an RST controller, is used to regulate the current load sharing between two parallel boost DC/DC converters, handle the instability issue caused by disturbances, and improve system reliability. The DC bus voltage is adjusted using the secondary loop built using the proportional-integral (PI) controller. The key benefits are precise voltage regulation, load power sharing, and good reliability. Aside from that, the RST controller has great resilience, quick dynamic response, and strong stability for significant load fluctuations. The feasibility and efficacy of the proposed approach are confirmed by time-domain simulation results, and hardware-in-the-loop (HIL) testing under various scenarios. The obtained findings show that the suggested control strategy is capable of ensuring proportionate power-sharing while dealing with DC voltage instability under CPL, CVL, uncertainty parameters, and input voltage fluctuations.

Recent Advancements and Application Of Z-Source Inverters

With the imminent energy crisis, mankind's demand for clean energy is increasing. Electricity, as the foundation of today's social development, its industry is developing at a high speed, and there is an urgent need for more efficient, stable and flexible power conversion solutions in the field of power electronics. However, traditional power electronics topologies encounter limitations, especially when confronted with wide-ranging input voltage fluctuations, posing challenges for meeting practical requirements. The Z-source inverter addresses issues inherent in conventional power electronic topologies. The Z-source inverter, a novel power electronic converter, has garnered significant attention in the power electronics domain due to its promising developmental prospects. The paper initially presents advancements in Z-source inverter topology, followed by a summary of pertinent technologies, including modulation techniques and closed-loop control strategies. Furthermore, it delves into a comprehensive examination of Z-source inverters, offering valuable references and insights to further enhance their performance and reliability. Finally, the challenges faced by Z-source inverters are discussed and possible directions of development are proposed.

Fuzzy control of synchronous buck converters utilizing fuzzy inference system for renewable energy applications

<p>In the present research, an innovative fuzzy control approach is developed specifically for synchronous buck converters utilized in renewable energy applications. The proposed control strategy effectively manages load changes, nonlinear loads, and input voltage variations while improving both stability and transient response. The method employs a fuzzy inference system (FIS) that integrates adaptive control, feedforward control, and multivariable control to guarantee optimal performance under a wide range of operating conditions. The design of the control scheme involves formulating a rule base connecting input variables to an output variable, which signifies the duty cycle of the switching signal. The rule base is configured to dynamically modify control rules and membership functions in accordance with load conditions, input voltage fluctuations, and other contributing factors. The performance of the control scheme is evaluated in comparison to conventional techniques, such as proportional integral derivative (PID) control. Results indicate that the advanced fuzzy control approach surpasses traditional methods in terms of voltage regulation, stability, and transient response, particularly when faced with variable load conditions and input voltage changes. As a result, this control scheme is highly compatible with renewable energy systems, encompassing solar and wind power installations where input voltage and load conditions may experience considerable fluctuations. This research highlights the potential of the proposed fuzzy control approach to significantly enhance the performance and reliability of renewable energy systems.</p>

Resonant DC/DC Converters: Investigating Phase-Shift Control

The paper presents an innovative approach to control the voltage of an LCL-T type converter at the output side against variation at input and load ports, utilizing a fixed-frequency phase-shift control scheme. The examination of the converter is performed employing a Fourier series method that takes into account the effect of n-harmonics. To assure high-frequency switches with a zero-voltage switching (ZVS) technique, the lagging pf mode is utilized. PSIM simulations were used to investigate the performance of a 300 W converter. With the minimal input voltage, all switches turn on with ZVS for all loading conditions, whereas the ZVS strategy loses by two switches when the voltage at the input is highest. The power loss calculations of each component are performed and presented in a pie chart. The findings of the experiments are presented and verified with theoretical and simulation results. It is demonstrated that for both input voltage and load fluctuations, a minor adjustment in pulse width is sufficient to keep the output voltage constant.

Real-time Thermal Energy Harvesting from Solar Radiation in Malaysia at Low-Temperature Difference

.Malaysia is located in a tropical climate with an abundance of solar radiation. Due to the low albedo of roofing material, around 20 % to 90 % of heat is absorbed from solar radiation. Thus, it is possible to harvest thermal energy from solar radiation using TEG, which promotes the diversity of renewable energy sources in Malaysia. Previous research evaluates the potential of thermal energy harvesting of the TEG open circuit voltage and unipolar condition. Thereby, this research focuses on designing and developing a thermal energy harvesting system (TEHS) for harvesting thermal energy at low-temperature differences from solar radiation. The TEHS can harvest thermal energy in bipolar conditions, different voltage levels, TEG input voltage fluctuations, and rapid weather-changing conditions during real-time field tests. Parallel with series balance TEG array configuration obtained impedance matching at 125 Ω. The field test method was conducted for 105 days. The maximum mean efficiency obtained is 94.33 %, with an output power range between 0.46 mW and 66.10 mW. The promising finding indicates that the developed TEHS is robust and capable of operating at optimum power transfer at uncontrollable solar radiation and weather conditions. In addition, the potential of the power generated evaluation is to be used as a power supply to several sensor nodes.

DC-link voltage balancing and control of qZ-source inverter fed induction motor drive

<span lang="EN-US">Poor performance of the motor drive system is caused when the direct current-link (DC-link) capacitor voltages of the inverter are not sufficiently generated. This is mainly because of the various load torque changes and input voltage fluctuation. The qZ-source inverter operates with a fully shoot-through technique. This technique causes mismatching between the upper and lower DC-link capacitor voltages. Without capacitor voltage-balancing function, the desired DC-link capacitor voltages could not be provided or maintained when there are load and speed changes. A Sawtooth carrier-based simple boost triple-sixty-degree (TSD) pulse width modulation (PWM) technique is used to drive the qZ-source T-type inverter because this technique can give a more significant boost DC-link voltage than a traditional simple boost PWM technique. Proportional integral (PI) controller is applied for the DC-link voltage controller to achieve the fast response and less steady-state error. The simulation model was constructed for a 4 kW, 400 V, 1,400 rpm induction motor (IM) drive system used in rolling mill using MATLAB/Simulink with and without voltage balancing function. As a result, DC-link voltages of the qZ-source T-type inverter fed the induction motor drive system could be controlled using a capacitor voltage-balancing function and the output power of the motor from the simulation result is approximately equal to 4 kW.</span>

Intelligent ISSA-Based Non-Singular Terminal Sliding-Mode Control of DC–DC Boost Converter Feeding a Constant Power Load System

In response to the issue of system oscillations in direct current (DC) microgrid systems with constant power loads (CPL), this paper proposes a non-singular terminal sliding-mode control (NTSMC) strategy based on the improved salp swarm algorithm (ISSA). Firstly, the state-feedback exact linearization technique is employed to establish a linearized model of the converter system. Then, the NTSMC based on a composite sliding-mode surface is designed to achieve rapid convergence and effectively weaken the chattering issue in traditional sliding-mode control, ensuring a constant power supply to the load. The parameters of the proposed NTSMC are optimized using the ISSA, which introduces an intelligent NTSMC. Finally, a MATLAB/Simulink simulation model is established. The simulation results show that the ISSA-based composite sliding-mode surface NTSMC system designed for DC microgrid systems with CPL exhibits high robustness and guarantees ideal steady-state characteristics and dynamic responses when input voltage fluctuations and load disturbances occur.

Analysis and Design of a New High Voltage Gain Interleaved DC–DC Converter with Three-Winding Coupled Inductors for Renewable Energy Systems

In this article, a new non-isolated interleaved DC–DC converter is proposed to provide a high voltage conversion ratio in renewable energy systems. The converter configuration is composed of a two-phase interleaved boost converter integrating a voltage-lift capacitor and three-winding coupled inductor-based voltage multiplier modules to achieve high step-up voltage conversion and reduce voltage stresses on the semiconductors (switches and diodes). The converter can achieve a high voltage conversion ratio when working at a proper duty ratio. The voltage stresses on the switches are significantly lower than the output voltage, which enables engineers to adopt low-voltage-rating MOSFETs with low on-state resistance. The switches can turn on under zero-current switching (ZCS) conditions because of the leakage inductor series reducing switching losses. Some diodes can naturally turn off under ZCS conditions to alleviate the reverse–recovery issue and to reduce reverse–recovery losses. The input current has small ripples due to the interleaved operation. The leakage inductor energy is recycled and voltage spikes on the switches are avoided. The proposed converter is suitable for applications in which high voltage gain, high efficiency and high power are required. The principle of operation, steady-state analysis and design considerations of the proposed converter are described in detail. In addition, a closed-loop controller is designed to reduce the effect of input voltage fluctuation and load change on the output voltage. Finally, a 1000 W laboratory prototype is built and tested. The theoretical analysis and the performance of the proposed converter were validated by the experimental results.

Design and Control of Two-Stage DC-AC Solid-State Transformer for Remote Area and Microgrid Applications

The critical challenges with integrating renewable energy into the grid are smooth power flow control, isolation between the high-voltage and low-voltage networks, voltage regulation, harmonic isolation, and power quality regulation. This paper considers the design and construction of a two-stage DC-AC solid-state transformer based on wide bandgap (WBG) semiconductor technologies, an optimized medium-frequency transformer, and PI and dq controllers for supplying urban area electric drive systems and microgrid applications. The designed SST consists of a dual active bridge (DAB) DC-DC converter followed by a DC-AC three-phase inverter. Each stage of the SST was simulated with independent controllers. The proposed system was initially developed in MATLAB/Simulink and a laboratory prototype was constructed to verify the results experimentally. Resistive and inductive load were used to test the load disturbance to evaluate the voltage regulation performance. This work has comprehensively provided the performance of a double stage (DC-DC and DC-AC converter) by taking into consideration input voltage, load disturbance, and voltage tracking both in simulation and experiment. The dual active bridge with its controller is able to maintain the desired output reference voltage with minimal voltage ripples under input voltage fluctuations and load variations. Similarly, the three-phase DC-AC converter’s controller exhibits better performance in tracking the desired reference voltage and producing well-regulated AC voltage with low harmonic distortion.

Time-domain Dynamic-performance-improvement Method for Pulse-width-modulated DC-DC Converters Based on Eigenvalue and Eigenvector Sensitivity

For pulse-width modulated (PWM) DC-DC converters, the input voltage fluctuation and load variation in practical applications make it necessary for them to have better dynamic performance to meet the regulation requirements of the system. The dynamic-performance-improvement method for PWM DC-DC converters is mainly based on indirect dynamic performance indices, such as the gain margin and phase margin. However, both settling time and overshoot in the time domain are important in practical engineering. This makes it difficult for designers to obtain a clear understanding of the time-domain dynamic performance that can be achieved with improved control. In this study, a direct analysis of the time-domain dynamic characteristic of PWM DC-DC converters is performed. A dynamic-performance-improvement method based on eigenvalues and eigenvector sensitivity (E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> S-based DPIM) is proposed to directly improve the time-domain dynamic performance index of PWM DC-DC converters. By considering a boost converter with proportional-integral control as an example, an additional virtual inductor current feedback control was designed using the proposed dynamic-performance-improvement method. Simulation and experimental results verify the validity and accuracy of the proposed dynamic-performance-improvement method.

Robust Nonsingular Terminal Sliding Mode Control of a Buck Converter Feeding a Constant Power Load

In recent years, DC microgrid systems feeding constant power loads (CPLs) have been given a particular focus due to their effect on the overall system stability caused by their electrical characteristics behaving as negative incremental impedance. To address this issue, this paper investigates the stabilization of a DC bus voltage in a DC microgrid (MG) feeding a CPL. The output voltage of the main DC bus is stabilized by using a robust nonsingular terminal sliding mode controller that is characterized by the elimination of the singularity problem that arises from the conventional terminal sliding mode controller. The CPL is emulated by a boost converter where its output voltage is tightly regulated. The system is investigated in terms of voltage following and disturbance rejection. The robustness and effectiveness of the proposed control strategy are assessed against input voltage fluctuations and power demand variations. The proposed controller is validated through simulations and an experimental setup.

Power Quality Improvement using Solar Fed Multilevel Inverter Based STATCOM

The major goal about suggested technique is to use a PSO-based proportional-integral (PI) controller towards enhance power quality performance about three-phase grid-connected inverter system. An approach like aforementioned tries to stabilize output current &amp; voltage, lower harmonics, &amp; lessen DC link input voltage fluctuation. Through reducing error about voltage regulator &amp; current controller schemes in inverter system, particle swarm optimization (PSO) technique was used towards adjust PI controller settings. When compared to conventional approach, simulation results show certain optimal parameters PI controller created among PSO produces better performance index results. According towards various research, reactive power supply can only modestly reduce voltage sags while totally mitigating harmonics using specialized power devices. Effective &amp; dependable use about PV solar farm inverters as STATCOMs is required towards guarantee certain generating units stay connected towards grid during voltage sags &amp; towards enhance system performance during abnormal circumstances.

A Novel Single-Stage Common-Ground Zeta-Based Inverter With Nonelectrolytic Capacitor

Aiming at the key problems of the existing nonisolated photovoltaic (PV) inverter, such as the common mode (CM) leakage current, the voltage up and down ability, and the service life restricted by the electrolytic capacitor, a novel single-stage common-ground zeta-based inverter with nonelectrolytic capacitor is proposed in this article. The proposed inverter is based on zeta dc converter and has the inherent voltage conversion characteristics of zeta converter, which makes it more suitable for PV system with wide input voltage fluctuation range. In addition, common-ground structure is adopted in this inverter, which can shorten the parasitic capacitor of the PV array to the ground. Therefore, it can effectively suppress the CM leakage current, reduce the shutdown frequency of the PV system, and improve the utilization rate of solar energy. Moreover, the proposed inverter does not contain electrolytic capacitors, which avoids the problem of high maintenance cost due to the short service life and high equivalent series resistance of electrolytic capacitors. First, the topology of the proposed inverter is given, and the modulation and operating principle are analyzed. Second, the passive components are analyzed. Finally, a 1 kW prototype is built for experimental verification. The experimental results verify the correctness of the theoretical analysis and simulation.

A Direct Actual-Power Control Scheme for Current-Fed Dual-Active-Bridge DC/DC Converter Based on Virtual Impedance Estimation

High dynamic performance is an essential requirement for the dual-active-bridge (DAB) dc/dc converters. As dc voltage sources, they should maintain the desired output voltage instantly under all working conditions. However, the previous literature mainly focus on the dynamic control of the voltage-fed DAB converters, and the existing control schemes for the current-fed DAB converters achieve limited dynamic performance. Aiming at improving the dynamic performance, a direct actual-power control (DAPC) scheme based on virtual impedance estimation (VIE) is proposed for the current-fed DAB converters in this article. The proposed DAPC scheme is based on a parallel structure instead of the series structure of existing control schemes, and it realizes fast dynamic control through combining actual power control with the VIE method. The proposed DAPC scheme can obtain the fastest transient response for the output voltage without voltage overshoot in transient conditions, such as load step change, input voltage fluctuation, and the desired output voltage step change. Besides, a leakage inductor precharging method is integrated into the DAPC scheme to avoid the current mismatching. Finally, the proposed DAPC schemes are compared with two existing control schemes and tested in a scale-down experimental prototype. Experimental results verify the effectiveness of the proposed DAPC scheme.

Review on Performance Analysis of Three Control Techniques for Buck Converter feeding a Resistive Load

In power systems, DC/DC converters are used to reduce or improve the dc voltage level. A dc/dc converter's major difficulty is controlling the output dc voltage closer to the desired set-point voltage at the load and input voltage fluctuation. Designers aim for better efficiency, reduced harmonics, and higher power while keeping converter size and power under safe limits. Several control techniques are used in dc/dc converters to overcome the problems mentioned above. This paper compares the transient performance of three control techniques, namely proportional-integral-derivative (PID) control, fuzzy logic control (FLC), and sliding mode control (SMC) methods, after a brief introduction of these techniques. Secondly, the three techniques have performed simulation results of a buck converter feeding a resistive load. Comparative analyses are presented for various conditions such as input voltage and load variation tests. It is observed that SMC outperforms the other two methods for both simulation scenarios.