DC Link Research Articles

An Enhanced Second-Order Terminal Sliding Mode Control Based on the Super-Twisting Algorithm Applied to a Five-Phase Permanent Magnet Synchronous Generator for a Grid-Connected Wind Energy Conversion System

This paper presents the application of a proposed hybrid control strategy that is designed to enhance the performance and robustness of a grid-connected wind energy conversion system (WECS) using a Five-Phase Permanent Magnet Synchronous Generator (FP-PMSG). The proposed approach combines the second-order terminal sliding mode control technique (SO-STA) with the super-twisting algorithm (STA), with the main goal of benefitting from both their advantages while addressing their limitations. Indeed, the sole application of the SO-STA ensures rapid convergence and robust performances in nonlinear systems, but it leads to chattering and reduces the whole system’s efficiency. Therefore, by incorporating the STA, the obtained hybrid control can mitigate this issue by ensuring smoother control actions and a superior dynamic response. This designed hybrid control strategy improves the adaptability of the control system to wind fluctuations and enhances the system’s robustness against external disturbances and uncertainties, leading to higher reliability and efficiency in the wind energy conversion system. Furthermore, the proposed hybrid control allows optimizing the power extraction and boosting the WECS’s efficiency. It is worth clarifying that, besides this proposed control, a sliding mode controller is used for the grid side converter (GSC) and DC link voltage to ensure stable power transfer to the grid. The obtained simulation results demonstrate the effectiveness of the proposed strategy in improving the stability, robustness, and efficiency of the studied WECS under dynamic conditions, creating a promising solution for control in renewable energy systems operating under severe conditions.

Modelling and experimental validation of DSTATCOM using a deep belief learning network with an anti-wind-up regulator

This article proposes the shunt compensation capability improvement using a deep belief learning network approach (DBLN) with anti-wind-up regulator-supported distributed static compensator (DSTATCOM). Six subnets make up this proposed DBLN controller. Three subnets for each active and reactive mass part are employed to isolate the basic component of the output current. Numerous issues such as past and normalising weight and learning rates are engaged in the DBLN-based weight-updating formula to have a superior dynamic presence, reduce the computational load and achievesfaster estimation, etc. This proposed DBLN is suggested for both proportional-integral (PI) and anti-wind-up regulator to showcase the better DC link voltage which further leads to providing better PQ improvement. This method offers excellent dynamics and resilience to outside disturbances. The suggested study is examined by simulation and experimental development using MATLAB/Simulink by a real-time interface based on a dSPACE 1104 for healthier potential regulation, potential balancing, input current harmonic distortion and PF correction under different load scenarios.

Multi-Fault-Tolerant Operation of Grid-Interfaced Photovoltaic Inverters Using Twin Delayed Deep Deterministic Policy Gradient Agent

The elevated penetration of renewable energy has seen a significant increase in the integration of inverter-based resources (IBRs) into the electricity network. According to various industrial standards on interconnection and interoperability, IBRs should be able to withstand variability in grid conditions. Positive sequence voltage-oriented control (PSVOC) with a feed-forward decoupling approach is often adopted to ensure closed-loop control of inverters. However, the dynamic response of this control scheme deteriorates during fluctuations in the grid voltage due to the sensitivity of proportional–integral controllers, the presence of the direct- and quadrature-axis voltage terms in the cross-coupling, and predefined saturation limits. As such, a twin delayed deep deterministic policy gradient-based voltage-oriented control (TD3VOC) is formulated and trained to provide effective current control of inverter-based resources under various dynamic conditions of the grid through transfer learning. The actor–critic-based reinforcement learning agent is designed and trained using the model-free Markov decision process through interaction with a grid-connected photovoltaic inverter environment developed in MATLAB/Simulink® 2023b. Using the standard PSVOC method results in inverter input voltage overshoots of up to 2.50 p.u., with post-fault current restoration times of as high as 0.55 s during asymmetrical faults. The designed TD3VOC technique confines the DC link voltage overshoot to 1.05 p.u. and achieves a low current recovery duration of 0.01 s after fault clearance. In the event of a severe symmetric fault, the conventional control method is unable to restore the inverter operation, leading to integral-time absolute errors of 0.60 and 0.32 for the currents of the d and q axes, respectively. The newly proposed agent-based control strategy restricts cumulative errors to 0.03 and 0.09 for the d and q axes, respectively, thus improving inverter regulation. The results indicate the superior performance of the proposed control scheme in maintaining the stability of the inverter DC link bus voltage, reducing post-fault system recovery time, and limiting negative sequence currents during severe asymmetrical and symmetrical grid faults compared with the conventional PSVOC approach.

Enhancing Power Quality in Standalone Microgrids Powered by Wind and Battery Systems Using HO Algorithm Based Super Twisting Sliding Mode Controllers

This paper addresses the challenge of enhancing power quality in a standalone microgrid powered by wind and battery systems. Fluctuations in wind power generation and unpredictable electricity demand significantly impact power quality. To mitigate these issues, a control strategy utilizing Super Twisting Sliding Mode (STSM) controllers tuned by the Hippopotamus Optimization Algorithm (HOA) is proposed. The HOA algorithm efficiently determines optimal STSM controller parameters, leading to improved system performance and stability. A comparative study was conducted against PI, Fuzzy Logic controllers, and other metaheuristic optimization algorithms (PSO, GWO, WOA). Simulation results, obtained using MATLAB/Simulink, demonstrate the superior performance of the proposed methodology. Specifically, during a simulated abrupt load change, the system exhibited rapid recovery with frequency reaching equilibrium, significantly faster than PI and Fuzzy Logic controllers. Moreover, the DC link voltage remained stable with fluctuations of only 2%, while the three-phase RMS voltages at the Point of Load Bus (PLB) maintained balanced and stable values. These results confirm the enhanced power quality and robust operation achieved with the proposed HOA-tuned STSM control strategy, outperforming other tested methods. The methodology effectively manages both the energy management system and improves power quality in standalone wind and battery-powered microgrids.

Performance Comparison and Characterization of IPMSM Drives Fed by Symmetrical and Asymmetrical Cascaded H-Bridge Inverters

This paper presents a comparative analysis of interior permanent magnet synchronous motor (IPMSM) drives powered by symmetrical and asymmetrical cascaded H-bridge multilevel inverters. The asymmetric topology operates using multiple DC sources with different voltage values, generating a voltage waveform with more output voltage levels than its traditional counterpart, all while maintaining the same hardware configuration. The main goal is to demonstrate that asymmetrical multilevel inverters are a promising option for improving the performance of electric drives while maintaining cost-efficiency and reliability. The proposed comparison is conducted through simulations in the MATLAB/Simulink R2024a environment, which allows an in-depth analysis of the dynamic performance of the electric drive. Additionally, the variation of the DC link input power of each H-bridge and the Total Harmonic Distortion (THD) of the voltage and current of the output of the converters were studied for different operating conditions in both cases. The obtained results were confirmed through real-time validation, demonstrating the applicability of electric drives powered by asymmetric converters and the advantages, in terms of efficiency, harmonic content and dynamic performance, in certain conditions of operation in terms of speed and applied load.

Optimizing Solar Energy Use in Electric Vehicle Charging for Sustainable Transport

A sustainable transportation goal is the integration of renewable energy into electric vehicle charging stations. This work aims at optimizing solar powered EV charging systems by means of novel techniques, which will lead to improving power flow management and ensuring system stability with Power Allocation Grey Wolf Optimization (PA_GWO). The effectiveness of the PA_GWO algorithm was evaluated under varying solar irradiation conditions with and without the optimization algorithm, on key performance metrics that include power quality, DC link voltage stability, and energy utilization. A fuel cell system was integrated into the system as an auxiliary source of energy to ensure the system runs continuously and offers consistent power supply during low solar irradiation periods. It improved the operational efficiency and management of power by integrating the fuel cell and PA_GWO. MATLAB/Simulink tools were used in modeling, simulation, and performance analysis for overall evaluation of the system's behavior and techniques for optimization. The results were positive and thus confirm better performance with potential to offer improved efficiency and reliability and more sustainable solar-based EV charging stations as solutions toward a shift in the entire world toward green transportation and renewable energy.

Precise Excitation of a Switched Reluctance Machine under Regenerative Mode in High-Speed Operation

The implementation of electric machines in electric and hybrid electric vehicles offers some advantages, including the ability to operate in regenerative mode. Switched reluctance (SR) machines have been alternative solutions due to their characteristics. Operating an SR machine in propulsion mode requires high torque and minimal torque ripple, while producing optimal output power in regenerative mode is required. In high-speed operation, when the back electromotive force is greater than the DC link voltage, single pulse-based methods are often used. Torque ripple problems can be neglected due to rotor inertia. In this paper, a single pulse-based control for SR machines in high-speed operation under regenerative and discontinuous conduction modes is analyzed. Excitation to magnetize the rotor and generation process to produce output power are compared to determine the effectiveness of energy saving during regenerative mode. By using a simple control strategy, precise excitation angles can be obtained to turn the machine on and off. Experimental work has been done to support the analysis. They show that by using proper excitation angles, the optimal output power can be generated.

A Modular Step-Up DC/DC Converter for Electric Vehicles

A step-up DC/DC converter is required to match the fuel cell’s stack voltage with the DC-link capacitor of the propulsion system in fuel cell-based electric vehicles (FCEVs). Typically, the nominal voltage of a single fuel cell ranges from 0.5 V to 1 V, and the DC-link voltage usually lies between 400 V and 800 V. This article proposes a new modular step-up DC/DC converter capable of providing a wide voltage-boosting range from the input to the output side using series-connected isolated boosting submodules (SMs). Modified versions of boost and Cuk converters are designed and used as the SMs to deliver a flexible output voltage, combining the voltage-boosting capability with the ability to embed a medium/high-frequency transformer, which provides both galvanic isolation and an additional degree of voltage boosting while drawing a continuous input current from the fuel cell with minimal ripple, enhancing performance. The proposed modular converter offers the advantages of improved controllability, scalability, and greater reliability, particularly during partial faults. The feasibility of the proposed converter is demonstrated through computer simulations conducted using MATLAB/SIMULINK® R2024a software where a DC link of 400 V is created from 50 V input sources. Additionally, a 1 kW small-scale prototype is designed and controlled using a TMS320F28335 digital signal processor to validate the mathematical analysis and simulation results, where the SMs are controlled to create a DC link of 100 V from four 25 V input sources with an electrical efficiency of approximately 95%.

Series Active Power Filter for Power Quality Improvement

The paper discusses the theoretical framework and operating principles of the SAPF, including its control strategies based on instantaneous reactive power theory and synchronous reference frame theory. The design criteria for the SAPF components, such as the voltage source inverter, DC link capacitor, and coupling transformer, are also elaborated to ensure optimal performance. Simulation studies using MATLAB/Simulink are conducted to evaluate the effectiveness of the proposed SAPF under various power quality disturbance scenarios. The results demonstrate that the SAPF effectively compensates for voltage sags, swells, and harmonics, maintaining voltage stability and reducing total harmonic distortion (THD) to within acceptable standards. Additionally, a prototype of the SAPF is developed and tested in a laboratory environment, confirming the simulation results and showcasing the practical feasibility of the solution. The study concludes that the Series Active Power Filter is a robust and versatile solution for power quality improvement in modern electrical distribution systems. Future work may involve exploring hybrid configurations combining series and parallel active filters for comprehensive power quality management and the development of advanced control algorithms for enhanced performance under dynamic load conditions.

Power Flow Control with a Single Stage Grid Connected Pv Mechanism with a Multilevel Inverter

There is potential to feed excess electricity to the grid for more efficient and cost-effective power utilization when solar PV arrays are installed widely in comparison to other renewable power output. The primary objective of this article is to use a multilevel inverter to operate autonomously regulate the active and reactive power flow. A vector control system that rotates synchronously with the grid frequency has been devised in both direct and quadrature reference frames. Two current control loops have been implemented to control the current delivered to the grid so that it will has low total harmonic distortion and is in phase with the grid voltage. To run the inverter at a suitable DC link voltage which corresponds to maximum power-which is established by the MPPT algorithm, a DC voltage control loop has also been implemented. Inverters that are connected to the grid are commonly utilized to enhance dispersed generation and power eminence.

Calculation and measurement of motor and converter losses according to IEC 61800-9-2 ED2

Calculated and measured motor and converter losses are compared using the example of a four-pole asynchronous motor with a rated output of 110 kW, operated on a standard converter. The determination of the motor losses using the polynomial approach to describe the motor losses in the field weakening range shows a clear deviation from the measurements. To calculate the converter losses, an equation for calculating the losses in DC link chokes was shown. The polynomial approach to describe the motor losses as a function of torque and speed can also be used for converters in the constant flux range. The semi-analytical model for calculating the converter losses shows satisfactory accuracy even when the motor is operated in the field weakening range.

Performance analysis of interlinking converter exchanging power between AC/DC renewable microgrids with advanced control technique

In a distribution system there are many types of AC/DC microgrids integrated at different locations. These microgrids may contain conventional or renewable sources which generate power using natural resources. The power generated by these microgrid sources is uncertain as the natural resources are unpredictable. Therefore, powers from these AC/DC micro grids need to be shared so as to compensate the load demand throughout the distribution system. An interlinking converter (ILC) is connected between the AC/DC microgrids operated by a novel advanced PQ control technique. Both the DC and AC microgrids are interconnected through ILC achieving power exchange between them as per the power demand and generation on both microgrids. Different operating conditions are considered for the analysis and the simulation of these modules are done using MALTAB/Simulink software. Several parameters like DC link voltage, ILC currents, point of common coupling (PCC) frequency, total harmonic distortions (THDs) and active power values are considered for validating the stability of the considered system.

SEPIC Based BLDC Motor Control for Electric Vehicles

Abstract: This paper presents a BLDC motor that can be utilized in electric vehicle applications where speed control is necessary. It is driven by a single-ended primary inductive converter (SEPIC). The inverter that feeds the motor uses PWM-based switching; however, a SEPIC converter in the DC link can be used to adjust the voltage level. Electronic commutation gating pulses are provided to the inverter input and the DC input. It is effective for electric vehicles since it uses a converter that switches to manage voltage. The SEPIC is lightweight and suitable for use with small electric cars. This paper describes using a SEPIC converter to drive a BLDC motor. The BLDC motor's closed-loop speed control is modelled using MATLAB /SIMULINK, and the simulation's outcomes are presented.

Vehicle-to-Grid Power Transfer Method for Electric Vehicles using off-board charger

This article explores a power transfer technique from vehicle to grid (V2G) via the construction of an off-board charger for electric cars (EVs). The charger accommodates several charging modes, such as grid-to-vehicle (G2V), vehicle-to-vehicle (V2V), and vehicle-to-grid (V2G), facilitating efficient and adaptable energy management. In G2V mode, the charger utilizes grid power to recharge electric vehicle batteries, whilst V2V mode enables direct energy transfer between electric vehicles, circumventing the grid. The novel integration of G2V and V2V modes enables the concurrent use of grid electricity and energy from other electric vehicles, therefore diminishing grid reliance and enhancing power efficiency. The system has a three-phase pulse width modulation (PWM) rectifier that sustains a constant DC link voltage and attains a unity power factor on the grid side, therefore adhering to the IEEE 519 standard for total harmonic distortion (THD). Furthermore, a half-bridge bidirectional DC/DC converter guarantees consistent charging and discharging currents, hence improving the reliability and efficiency of the charging process. This holistic strategy enhances dynamic energy flow and grid stability while providing possible economic advantages to electric vehicle owners and operators via the integration of renewable energy sources and sophisticated management algorithms for improved energy use and storage.

ЕЛЕКТРОМЕХАНІЧНІ ХАРАКТЕРИСТИКИ БЕЗКОНТАКТНОГО ДВИГУНА З ПОСТІЙНИМИ МАГНІТАМИ ПРИ ШИРОТНО-ІМПУЛЬСНОМУ ЖИВЛЕННІ

The paper is devoted to the study of the characteristics and operating modes of a brushless permanent magnet motor in the structure of an electric drive with a two-wire external power supply from a voltage source with pulse-width regulation. The dependences of the motor rotation frequency, the stator current effective value and the average value of the current in the DC link of the voltage inverter, as well as the dependences of the torque coefficient on the average value of the motor torque are given. The influence of the frequency of the pulse supply voltage on the operating modes of the motor is studied. The current and torque limitation modes of the motor in a system with a single-position relay controller and a fixed transistor shutdown interval former are studied. Ref. 12, fig. 16.

Improved direct ripple power predictive control of single-phase rectifier based on ripple separation

Voltage ripple is introduced to the DC link when a single-phase rectifier operates, which affects the energy balance of both the DC and AC sides. Accurate acquisition and fast, precise tracking of the decoupling capacitor voltage and decoupling inductor current reference values are challenges in the design of active power decoupling controllers. This article employs instantaneous ripple power control, shifting the focus from the accuracy of the decoupling capacitor voltage and decoupling inductor current reference values to the accuracy of the ripple power reference value. A ripple separation-based active power decoupling control strategy is proposed. By designing a time-varying observer, the amplitude feedback signal of the output voltage’s second-harmonic ripple is extracted in real time to generate the ripple power reference, enhancing its accuracy and reliability. The endpoint equivalent modulation method is adopted to track the instantaneous ripple power. Compared with traditional finite control set model predictive control, it achieves better tracking performance at the same control frequency, with a fixed switching frequency. Additionally, measures are proposed to address input current distortion caused by output voltage ripple entering the rectifier’s grid-side current control loop. This avoids the pollution of the input current by the output ripple voltage. Simulations and experimentations are performed to test the proposed control strategy.

A bidirectional DC/DC converter for renewable energy source-fed EV charging stations with enhanced DC link voltage and ripple frequency management

The amount of electricity that the grid must supply has increased as the number of electric vehicles (EVs) has increased. The best way to minimize power pollution between the automobile and the grid is to use an EV charging station to establish a bidirectional connection with an energy storage unit (ESU). This paper proposes a bidirectional DC/DC converter for battery available at the renewable energy sources (RES) fed charging station. This bidirectional DC-DC converter has important advantages such as dc link voltage stress reduction and the ripple frequency of inductor current is two times of the converter's switching frequency. The proposed converter consists of two identical Zero Voltage Transition (ZVT) cells and each cell includes a capacitor, two resonant inductors and a supplementary switch which is combined with the traditional three level topology that enables both buck and boost operating modes. The simulation-based analysis has been done using MATLAB/Simulink. The simulation results have been verified with the help of experimental setup is presented for the converter module for validating the charging station.

Virtual inertia extraction from a DC bus capacitor in a three−phase DC/AC inverter-based microgrid with seamless synchronisation operation modes

It is crucial to employ power electronics converters for energy transfer in distributed energy resources such as photovoltaics, and wind energy system. Thus, parameters such as voltage, current, active and reactive powers, and frequency referred to the AC side need to be controlled. The local load could be operated either from converter itself or grid, hence the system could be called microgrid. In this paper, the active and reactive powers would be controlled separately when the inverter is connected to the grid. While in the islanded or autonomous mode, the proposed control would support the voltage and frequency. The proposed controller would be designed and function as the synchronous machine's voltage regulator and governor. The virtual synchronous machine is adopted to obtain the inertia and the concept is that the frequency of the grid is linked to the virtual frequency or so called the virtual speed of the rotor. The virtual frequency is obtained directly from the DC bus voltage of the inverter and this is achieved by allowing the DC link capacitor voltage to swing boarder than the grid frequency by making the capacitor voltage imitating frequency of grid. Where the frequency of grid is associated to the virtual frequency which is derived directly from DC capacitor voltage, thus, large level of inertia is extracted. The basic formulation, supervisory control, extraction the inertia from DC capacitor voltage, coordination transition, and evaluation the stability is presented in this paper. The mimic operation of the inverter as Synchronous Machine SM can make the distributed energy resources to be operated in either grid − connected or islanded modes without the need to adopt control structure for the required mode. In addition, it provides robust performance in comparison with the traditional current, voltage and frequency control approaches. Moreover, the controller would be implemented for inverter having any type of filters and it is resilient to any variations in the filter and grid parameters. Furthermore, there is no concerning regarding instability problems, where it achieves the synchronisation smoothly and swiftly, and it is appropriate for implemented digitally.

Optimizing power output in hybrid photovoltaic/wind systems: a nonlinear back-stepping approach for enhanced efficiency and stability

Abstract This paper investigates the challenge of controlling hybrid renewable energy systems (HRES), specifically those combining wind energy and photovoltaic sources, under varying environmental conditions such as fluctuating wind speeds and partial shading. The primary objective is to develop a robust backstepping control strategy that enhances the system’s stability and energy efficiency while ensuring seamless grid integration through the use of dual-fed induction generators. The study uses advanced modeling techniques, including maximum power point tracking for wind turbines and particle swarm optimization for photovoltaic systems, to optimize energy capture. A detailed simulation framework was designed to validate the effectiveness of the control strategy under different climatic scenarios. Quantitative results show that the wind turbine achieved over 95% power recovery, the DC link voltage remained stable within 0.5% of the reference, and photovoltaic energy extraction was optimized with 98% accuracy, even under partial shading. These findings indicate that the proposed control strategy significantly enhances the performance, reliability, and adaptability of the HRES. This work offers a promising contribution to the integration of renewable energy sources into the electrical grid, supporting a more sustainable energy future.

A frequency control strategy with DC microgrid systems for EV stations

ABSTRACT Fluctuations in power supply and demand lead to frequency deviations, which have detrimental effects on the operation of electrical devices and equipment. Therefore, the implementation of effective frequency control mechanisms is essential for enhancing the strength and dependability of microgrid systems. Research aims to develop a frequency control mechanism for an electrical grid system that integrates both wind and photovoltaic (PV) energy sources. The proposed system utilises a Doubly Fed Induction Generator (DFIG) system with frequency controller for regulating frequency and balancing source and demand of power in the grid. To optimise the solar power output, a Luo converter is implemented, which offers high efficiency with improved conversion of power. Additionally, an adaptive neuro fuzzy inference system (ANFIS) maximum power point tracking (MPPT) controller is engaged to ensure optimal regulation of photovoltaic system. DC link obtained from the PV system is then utilised for powering DC loads and charging electric vehicles (EVs) effectively. In order to accomplish this, a bidirectional converter is used, which permits power flow in both ways and facilitates effective EV charging from the microgrid system. The validation of research is conducted on MATLAB software, and the results proves greater converter efficiency of 94.93%, with reduced total harmonic distortion (THD) of 1.24%.