Search Results (41)

With the increasing penetration of renewable energy and the rising demand for power quality, the dynamic performance and accuracy of grid-voltage detection have become crucial for the control of grid-following devices such as dynamic voltage restorers (DVRs). However, the conventional moving average filter (MAF) in grid-voltage detection suffers from inherent limitations in dynamic response. To address this issue, this paper proposes a voltage-detection method, which is based on an adaptive variable-parameter filtering algorithm termed MAF-MATCH-V. First, a cascaded filter model is constructed by integrating a zero-pole matcher (MATCH) with the MAF. Frequency-domain analysis demonstrates that the MATCH compensates for the mid- and high-frequency magnitude attenuation and reduces the phase delay of the MAF, thereby accelerating the dynamic response while preserving its harmonic-rejection capability. Second, the influence of the matching coefficient on the time-domain response is investigated, and a time-varying adaptive strategy is designed to balance rapid disturbance recognition with steady-state convergence. Finally, experimental results under various non-ideal grid conditions demonstrate that the proposed method achieves superior overall performance compared with conventional approaches. Specifically, MAF-MATCH-V realizes millisecond-level event recognition and zero steady-state error convergence, making it a practical solution for the real-time control of grid-following equipment in modern power systems. Full article

In the current energy landscape, power quality (PQ) emerges as a critical concern. Even when there is no fault on a line, PQ issues are common in all power networks since 90% of power systems’ loads are variable or inductive in nature. Variable loads cannot be avoided; hence, PQ concerns such as voltage swelling and sag will always arise. Voltage sag is one of the main issues within a distribution network, resulting in financial losses for the utility company and the customer. The Dynamic Voltage Restorer (DVR) effectively addresses voltage sags and minimizes total harmonic distortion (THD) in the distribution network. This paper proposed a novel control strategy to increase the PQ in a system. A Frilled Lizard Optimization-optimized fuzzy PI controller is proposed in this work to control the inverter. This proposed method improves the DVR’s ability to correct voltage sag and reduce total harmonic distortion as soon as possible. The PI control scheme is utilized initially to reduce the oscillations and remove the steady-state error. To increase the tendency rate of the error to zero, the PI method is applied to a fuzzy logic-based compensatory stage. The proposed approach is validated using pro-type models, as well as mathematical and Simulink modelling. In the Results Section, the performance of the proposed controllers with the DVR is tabulated and compared with other DVR controller schemes described in other research papers. Full article

The Dynamic Voltage Restorer (DVR), which is connected in series between the power grid and the load, can rapidly compensate for voltage disturbances to maintain stable voltage at the load end. To enhance the energy supply capacity of the DVR and utilize its shared circuit topology with photovoltaic (PV) inverters—which enables the dual functions of voltage compensation and PV-storage power generation—this study integrates PV and energy storage as a coordinated energy unit into the DVR, forming a PV-storage-integrated DVR system. The core innovation of this system lies in extending the voltage disturbance detection capability of the DVR to include harmonics. By incorporating a Butterworth filtering module and voltage fluctuation tracking technology, high-precision disturbance identification is achieved, thereby supporting power balance control and functional coordination. Furthermore, a multi-mode-power coordinated regulation method is proposed, enabling dynamic switching between operating modes based on PV output. Simulation and experimental results demonstrate that the proposed system and strategy enable smooth mode transitions. This approach not only ensures reliable voltage compensation for sensitive loads but also enhances the grid-support capability of PV systems, offering an innovative technical solution for the integration of renewable energy and power quality management. Full article

This work proposes an effective control technique for enhancing the stability of Doubly Fed Induction Generator-Based Wind Turbines (DFIG-WTs) connected to the grid during voltage sag and swell events, ensuring the reliable and efficient operation of wind energy systems integrated with the grid. The proposed approach integrates a Dynamic Voltage Restorer (DVR) in series with a Wind Turbine Generator (WTG) output terminal to enhance the Fault Ride-Through (FRT) capability during grid disturbances. To develop a flexible control strategy for both unbalanced and balanced fault conditions, a combination of feedforward and feedback control based on a sliding mode control (SMC) for DVR converters is used. This hybrid strategy allows for precise voltage regulation, enabling the series compensator to inject the required voltage into the grid, thereby ensuring constant generator terminal voltages even during faults. The SMC enhances the system’s robustness by providing fast, reliable regulation of the injected voltage, effectively mitigating the impact of grid disturbances. To further enhance system performance, Model Predictive Control (MPC) is implemented for the Rotor-Side Converter (RSC) within the back-to-back converter (BTBC) configuration. The main advantages of the predictive control method include eliminating the need for linear controllers, coordinate transformations, or modulators for the converter. Additionally, it ensures the stable operation of the generator even under severe operating conditions, enhancing system robustness and dynamic response. To validate the proposed control strategy, a comprehensive simulation is conducted using a 2 MW DFIG-WT connected to a 120 kV grid. The simulation results demonstrate that the proposed control approach successfully limits overcurrent in the RSC, maintains electromagnetic torque and DC-link voltage within their rated values, and dynamically regulates reactive power to mitigate voltage sags and swells. This allows the WTG to continue operating at its nominal capacity, fully complying with the strict requirements of modern grid codes and ensuring reliable grid integration. Full article

Doubly Fed Induction Generator (DFIG)-based Wind Energy Systems (WESs) have become increasingly prominent in the global energy sector, owing to their superior efficiency and operational flexibility. Nevertheless, DFIGs are notably vulnerable to fluctuations in the grid, which can result in power quality issues—including voltage swells, sags, harmonic distortion, and flicker—while also posing difficulties in complying with Fault Ride-Through (FRT) standards established by grid regulations. To address the previously mentioned challenges, this paper develops an integrated approach utilizing a Dynamic Voltage Restorer (DVR) in conjunction with a Lithium-ion storage system. The DVR is coupled in series with the WES terminal, while the storage system is coupled in parallel with the DC link of the DFIG through a DC/DC converter, enabling rapid voltage compensation and bidirectional energy exchange. Simulation results for a 2 MW WES employing DFIG modeled in MATLAB/Simulink demonstrate the efficacy of the proposed system. The approach maintains terminal voltage stability, reduces Total Harmonic Distortion (THD) to below 0.73% during voltage sags and below 0.42% during swells, and limits DC-link voltage oscillations within permissible limits. The system also successfully mitigates voltage flicker (THD reduced to 0.41%) and harmonics (THD reduced to 0.4%), ensuring compliance with IEEE Standard 519. These results highlight the proposed system’s ability to enhance both PQ and FRT capabilities, ensuring uninterrupted wind power generation under various grid disturbances. Full article

In existing two-stage single-phase dynamic voltage restorer (DVR) voltage sag mitigation devices, the output-side power contains a pulsating component at twice the fundamental frequency (2f₀), leading to the presence of second-order ripple currents (SRCs) on the DC input side. This, to some extent, affects the reliability of the system and has a significant impact on the lifespan of energy storage devices. In this study, the dual-loop control method of the buck/boost converter is combined with the virtual impedance auxiliary control strategy to suppress SRCs. Compared to existing solutions, this method offers the advantages of being fast, stable, and reliable, while the virtual impedance auxiliary control strategy is flexible and easy to implement. The feasibility and stability of this strategy were verified using a 3 kW DVR prototype. When applying the two virtual impedance methods, the second harmonic content was reduced from 39.64% to 1.74% and 1.78%, respectively. The proposed control strategy demonstrates significant effectiveness in suppressing second harmonic currents. Full article

Electric vehicles are replacing conventional vehicles in today’s world due to their eco-friendly operation and reduced maintenance. Although EVs offer advantages over conventional vehicles, there is a limited number of charging stations, and numerous power quality issues have emerged at these locations. This is due to the voltage, current, or frequencies being abnormal, which leads to sudden voltage drops, voltage swells, long interruptions, and short interruptions occurring at the charging stations. To address issues arising from client-side anomalies, we attach conventional FACTS devices closer to the load end. One such dependable custom power gadget for dealing with voltage sag is the one developed in this article, and it is called an enhanced dynamic voltage restorer (DVR). The proposed device continuously monitors the load voltage waveform and injects (or absorbs) the balance (or surplus) voltage into (or away from) the load voltage whenever a sag occurs. We develop a reference voltage waveform to achieve the aforementioned capabilities. In this paper, the methods of compensation for these problems at charging stations are discussed. Furthermore, the power quality problems are compensated for by the proposed system using an SVPWM controller. Simulation and real-time implementation are carried out, and the results are discussed. The inclusion of SVPWM control significantly improves voltage regulation and reduces THD by 60–70% compared to conventional PWM methods, which achieve only 40–50% reduction. The proposed DVR is designed for single-phase applications, making it suitable for low-voltage distribution systems and sensitive industrial loads. The proposed model provides a rapid response time (<10 ms), and the efficiency of the proposed DVR is found to be 92%, which is greater than that of conventional designs (86%). Full article

In view of the sudden grid voltage distortions, such as voltage sags and unbalances, that may occur in photovoltaic (PV) grid-connected systems under local shading conditions, this paper proposes a control strategy integrating a linear active disturbance rejection controller (LADRC)-based virtual synchronous generator (VSG) and an active disturbance rejection controller (ADRC)-based dynamic voltage restorer (DVR). To enhance the stability and response speed of the PV inverter system, a novel LADRC-based voltage–current dual closed-loop control strategy with pre-synchronization is designed, ensuring stable operation of the inverter and load. To address the overshooting issues found in traditional PI control under local shading, the ADRC-based DVR compensates for PV system voltage fluctuations, achieving rapid voltage distortion compensation and ensuring grid-connected system safety. Simulink experiments verify the feasibility and effectiveness of the proposed control strategy in improving transient voltage quality in PV systems affected by local shading. The total harmonic distortion rates of voltage and current are both less than 0.5%, which significantly improves the performance compared to existing research. Full article

Dynamic voltage restores (DVRs) are usually used to mitigate the effect of voltage sag and guarantee sufficient power supply for sensitive loads. However, three-phase voltage cannot be compensated to the desired balance voltage under unbalanced three-phase loads by traditional DVRs with a three-phase, three-leg inverter. To address this problem, a three-phase, four-leg inverter-based DVR is first introduced in this paper, and then the state space model in its continuous form and discrete form are established, respectively. A two-step predictive method is proposed for the prediction of the output voltage in each switching state by the established voltage prediction model. Finite-control-set model predictive control (MPC) is developed to be used in the three-phase, four-leg inverter-based DVR. Its dynamic response is effectively improved by the proposed MPC method under various voltage sag conditions. The proposed DVR control strategy is validated via MATLAB/Simulink-R2022b simulations, which demonstrate its effectiveness in voltage compensation under various sag conditions. Full article

To address the issue of uncertainty in the occurrence time of voltage sags in power grids, which affects power quality, a voltage state prediction method based on LSTM neural networks is proposed for predicting voltage states. For the problem of quickly and accurately compensating for voltage sags, a DVR system based on a new approach law of sliding mode variable structure control is proposed, which significantly reduces chattering, improves response speed, and enhances the robustness of the system. The stability of the system is proven based on Lyapunov stability theory. Simulation experiments are conducted to analyze the voltage state prediction effect based on the LSTM neural network and the compensation effect of the novel reaching law of sliding mode variable structure control under different levels of voltage sag, validating the effectiveness and correctness of the proposed solution. Full article

Due to advances in power electronics technology and the evolution of automation devices, the number of electrical devices that are sensitive to power quality is rapidly increasing, and for this reason, users are increasing their demand for high quality. To meet power quality demands, many power conversion devices are used, including dynamic voltage restorers (DVRs). DVRs are recognized as devices that can effectively manage problems such as voltage segments, swells, and harmonics. DVR control requires many samples for harmonic compensation, which has the disadvantage of being complicated to implement due to fast digital signal processing computation and the application of the cyclic discrete Fourier transform. In this paper, a high-precision DVR system configuration is proposed that compensates for harmonics using a periodically equivalent time-interval sampling technique and a novel circular-structured memory filter. The proposed circular-structured multi-pointer memory filter is an effective filter algorithm for high-precision input voltage measurement because it can remove noise and compensate for the delay of the phase angle of the filter in voltage measurement. A simulation and DVR prototype system were built, and the feasibility and effectiveness of the phase angle multi-filter voltage detection method and the compensation method were verified by experiments. Full article

In this study, the author presents the results of a survey on the utilisation of a dynamic voltage restorer (DVR) in power systems to alleviate voltage problems that result in sags, swells and fluctuations in voltage outside the required steady limits. A methodology based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement is adopted for conducting and reporting on the review, while the Scopus database is used to locate the relevant publications. A total of 68 publications qualify for inclusion in the survey. A bibliometric analysis covering the number of publications per annum, the top 10 most-cited journals and the top 10 most-cited publications is performed. The information from the selected publications is extracted, summarised and categorised into network scenarios for the use of DVRs, topologies and optimisation of DVRs; strategies for DVR controllers; and platforms that evaluate the feasibility of DVR topologies and controllers. Moreover, research trends and gaps are evaluated. Finally, potential areas for future research are proposed. This study provides an overview of the research on the use of a DVR to resolve voltage problems and is a resource for researchers generally interested in distributed flexible AC transmission systems (DFACTSs) and particularly interested in DVRs. Full article

Photovoltaic (PV) systems are crucial to the production of electricity for a newly established community in Egypt, especially in grid-tied systems. Power quality (PQ) issues appear as a result of PV connection with the power grid (PG). PQ problems cause the PG to experience faults and harmonics, which affect consumers. A series compensator dynamic voltage restorer (DVR) is the most affordable option for resolving the abovementioned PQ problems. To address PQ difficulties, this paper describes a grid-tied PV combined with a DVR that uses a rotating dq reference frame (dqRF) controller. The main goal of this study is to apply and construct an effective PI controller for a DVR to mitigate PQ problems. The artificial rabbits optimization (ARO) is used to obtain the best tune of the PI controller. The obtained results are compared with five optimization techniques (L-SHADE, CMAES, WOA, PSO, and GWO) to show its impact and effectiveness. Additionally, Lyapunov’s function is used to analyze and evaluate the proposed controller stability. Also, a mathematical analysis of the investigated PV, boost converter, and rotating dqRF control is performed. Two fault test scenarios are examined to confirm the efficacy of the suggested control approach. The parameters’ (voltage, current, and power) waveforms for the suggested system are improved, and the system is kept running continuously under fault periods, which improves the performance of the system. Moreover, the findings demonstrate that the presented design successfully keeps the voltage at the required level with low THD% values at the load side according to the IEEE standards and displays a clear enhancement in voltage waveforms. The MATLAB/SIMULINK software is used to confirm the proposed system’s performance. Full article

This paper presents an improvement to the fault ride-through (FRT) capabilities for a wind turbine that employs a switched reluctance generator (SRG) using a dynamic voltage restorer (DVR). The wind turbine may be disconnected from the grid by voltage sag, swell, and faulty line voltage in the grid. To improve the stator voltage of an SRG during grid failures, the DVR is applied to inject voltage at the point of common coupling (PCC) into the grid voltage. A control strategy for the DVR based on fuzzy logic controller (FLC) is proposed in this study to improve the FRT capability and meet the grid codes while avoiding the disconnection of the turbine from the grid. MATLAB/SIMULINK simulation validated the effectiveness and performance of this approach under three test cases: balanced sag, unbalanced sag, and a single line-to-ground fault. In addition, the total harmonic distortions utilizing different controllers were compared in sag mode. Furthermore, the simulation results exhibited significant improvement in transient and steady-state response, thus verifying the effectiveness of the control strategy compared to traditional methods. Full article

With the prevalence of renewable energy sources such as wind power in the power system, analyzing the fault characteristics of systems composed of DFIGs is becoming increasingly important. Therefore, this article analyzes, at first theoretically, the fault characteristics of a doubly fed induction generator (DFIG) during fault periods. It was found that the fault current of the DFIG exhibited the frequency offset phenomenon, which is affected by the depth of voltage dips and can negatively impact traditional distance protection. Furthermore, a method using a dynamic voltage restorer (DVR) based on superconducting magnetic energy storage (SMES) was adopted to compensate for the fault voltage of DFIG, which can mitigate the voltage dips of the DFIG. This method can not only achieve the fault ride through for DFIG but also significantly improve the frequency offset of the fault current during fault periods. Finally, a model composed of a 2.5 MW DFIG-based wind turbine and a 2.5 MW DVR-based SMES was built using a real-time digital simulator (RTDS) platform, and the simulation results showed that the fault stator voltage of DFIG can be compensated at a rated value of 0.69 kV, and the frequency of fault current can be maintained at 50 Hz These results validate the excellent performance of the method in achieving the fault ride through of DFIG and improving the frequency offset of the fault current by comparing multiple type faults while employing different protection methods. Full article