Fault Ride-through Capability Research Articles

FRT Capability Enhancement of DFIG-based Wind Turbine with Coordination Control of MSVC and FCL

Objective: To address the problems of various FRT (fault ride through) schemes in DFIG (doubly fed induction generator) systems, especially their applicability under different voltage sags, a combination scheme of an MSVC (minimized series voltage compensator) and FCL (fault current limiter) is proposed. Methods: Based on the analysis of the mathematical model of the DFIG and considering the capacity and volume in the process of practical engineering, the application structure and specific control strategy of an MSVC in DFIG systems are designed on the stator side, and the application effect is analyzed theoretically. Simultaneously, the application structure and control strategy of the FCL is proposed on the rotor side, and the application effect of the combination scheme is theoretically deduced and analyzed. Moreover, the simulation model is built on the MATLAB/Simulink platform. Results: The simulation results show that the scheme can quickly and effectively recover the fault voltage of the DFIG under different voltage sag degrees and has better dynamic performance. At the same time, it can effectively limit the fault current and suppress the DC-link voltage of the rotor side, and the transition process is relatively stable. Conclusion: The purpose of improving the FRT capability of the DFIG system is realized.

A Generalized Load Model Considering the Fault Ride-Through Capability of Distributed PV Generation System

Considering the voltage stability problem brought by large-scale distributed PV access to the distribution network, this paper proposes a generalized load model that considers the fault ride-through capability of distributed PV. Firstly, the detailed model of the distribution network is established, and the detailed model is calibrated based on the measured data, the simulation errors are below 1%. And then establish a generalized load model considering distributed PV high and low voltage traversal ability. The sensitivity analysis results are used to rank the parameters to be identified, and the parameters with higher sensitivity are identified. The parameters are obtained from the detailed model and measured data, and four sets of parameters are identified and simulated under different PV penetration rates and fault conditions. The calculated fitting errors are less than 1%. The results show that the generalized load gray box model of the distribution network with distributed PV high and low voltage ride-through capability can reflect the dynamic characteristics of the distribution network well.

Synchronverters With Fault Ride-Through Capabilities for Reliable Microgrid Protection During Balanced and Unbalanced Faults

Synchronverters With Fault Ride-Through Capabilities for Reliable Microgrid Protection During Balanced and Unbalanced Faults

Novel chattering free binomial hyperbolic sliding mode controller for asymmetric cascaded E-type bonded T-type multilevel inverter-based dynamic voltage restorer to meliorate FRT capability of DFIG-based wind turbine

The endurance capability of Doubly Fed Induction Generator (DFIG)-based wind turbine to network against different disturbances is an important criterion to meet the recent grid codes requirements. This generator has to provide the required energy under the perturbation conditions which is principally specified by Fault Ride-Through (FRT) capability. It refers to safe and continuous operation of DFIG without interruption which has been performed by Dynamic Voltage Restorer (DVR) using fast and accurate compensation of the voltage fluctuations. This paper aims to introduce an innovative quasi-sinusoidal voltage synthesizer for DVR to enhance the power quality and power delivery. Hence, a new Asymmetric Cascaded E-type Bonded T-type Multilevel Inverter (ACEBTMI) with binary geometric progression form of DC sources is proposed to provide high-step staircase sinusoidal voltage containing low semiconductor switches. Then, accurate triggering signals for the suggested ACEBTMI corresponding to the voltage fluctuations have been provided by new Chattering Free Binomial Hyperbolic Sliding Mode Controller (CFBHSMC). To validate compensation capability of the proposed DVR, ACEBTMI part has been compared with some traditional and familiar multilevel inverters, and also CFBHSMC part has been compared with SMC, FLC and PID controllers. In precise, the simulation results have definitely confirmed the accurate tracking and robust control performance of CFBHSMC to support ACEBTMI-based DVR which enables DFIG to ride-through different voltage perturbations.

Real-time V2G simulator for grid system frequency and voltage regulation with fault ride-through capabilities

Electric vehicles (EVs) have become one of the promising power grid ancillary services. They can help reduce the intermittent of renewable energy sources by supporting active power and frequency control services. Additionally, bi-directional chargers included into EV batteries can supply/consume reactive power for voltage regulation. To improve voltage quality, a unique control approach is devised to offer fault ride-through. In this study, real-time charging optimization schemes based on particle swarm optimization are developed to coordinate the EVs charging/discharging power with the grid power dispatches depending on the charging priority and preferential electricity prices. Five different car user profiles including different initial state of charge and plug in state have been depicted. Different optimum issues are carried out with comprehensive simulations employing hardware in the loop via real-time simulation for a modified IEEE 14-bus test system. Where different frequency and voltage controls, management strategies, variant fault scenarios, benefits, and challenges for power system regulation with EVs are illustrated. According to the simulation results, the proposed optimized charging strategies reduce the total expenses of EV parking station by 40 % compared to other cases, hence maximizing EV owner satisfaction. The net load curve is smoothed and reduced by 11 %, particularly during peak period.

Perturbation estimation based single-loop decoupling control strategy for DC-based DFIG to augment MPPT and FRT capabilities

This paper proposes a single-loop decoupling controller with high-gain perturbation observer (HP-FLC) for double-VSC DFIG which can be connected to DC grid to extract maximum wind power and improve fault ride-through (FRT) capability. Lumped perturbation terms are defined in the HP-FLC to include all unknown, time-varying dynamic and external perturbations, which are actively estimated by high-gain perturbation observer. Then, a more time-efficient single-loop feedback decoupling controller is designed to compensate the perturbation estimation. This control strategy combines the advantages of classical feedback controller and perturbation observer, which is separated from the accurate system model and easy to implement. Simulation results show that the proposed control strategy can achieve better wind power extraction and stronger FRT capability compared with double-loop feedback linearization controller (DL-FLC) and single-loop feedback linearization controller (SL-FLC), and the transient performance is better than that of the sliding-mode feedback controller (SMC-FLC). Finally, an experimental platform is built to confirm the practical implementation of the proposed approach.

Voltage regulation during short-circuit faults in low voltage distributed generation systems

As the penetration of inverter-based distributed generations into microgrids continues to rise, the significance of power electronic inverters in modern power systems becomes increasingly pronounced. They are designed to have fault ride-through capabilities, enabling them to sustain operation even during and after fault conditions. This paper presents a novel voltage compensation strategy based on the line impedances addressing both positive and negative-sequence aspects, for a three-phase three-wire inverter deployed to regulate the low-voltage network during unsymmetrical faults, thereby preserving voltage stability. The control strategy is carried out in a synchronous reference frame (dq) to govern the positive and negative-sequence voltages and currents of the inverter. By synthesizing AC currents, the inverter restores the positive-sequence voltage to its rated value while mitigating negative-sequence voltage at the point of common coupling arising from unsymmetrical faults. Through MATLAB/Simulink, are investigated three unsymmetrical fault scenarios (single line-to-ground, line-to-line, and double line-to-ground faults) within the low-voltage distribution network of the 18-bus European Cigré, incorporating three inverters equipped with the proposed voltage support capability. The results confirm that inverter-interfaced distributed generators with local voltage support can improve the system’s fault ride-through capability by reducing voltage drops and unbalances.

FRT capability improvement of a wind power system using support vector regression and deep neural network models

ABSTRACT The increasing energy demand and environmental conditions have led many countries to favor renewable energy,such as wind and solar,over conventional power plants. As per the Central Electricity Authority (CEA), India’s wind power capacity has grown substantially, reaching 45,154 MW in 2023, from 22,465 MW in 2013. However, integrating wind generators to an existing power system network can reduce transient stability during faults. To prevent wind turbine disconnection during faults, Indian grid code authorities mandate Fault Ride Through (FRT) or Low Voltage Ride Through (LVRT) capability for wind turbines. This paper proposes Dynamic Voltage Restorer (DVR) for enhancing the FRT capability of a constant speed wind turbine. Analysis and simulation are done on a fixed speed wind turbine employing Squirrel Cage Induction Generator (SCIG) under balanced and unbalanced voltage sags. Performance of DVR with two Artificial Intelligence-based controllers, Support Vector Machines(SVM) Regression Model Based Supervised Machine Learning algorithm, and Deep Neural Network (DNN) controller, is analysed and compared. The SVM Regression algorithm, achieves 100% voltage sag compensation under unbalanced voltage sags, reduces torque pulsations to 25% and maintains rotor speed at rated values, enabling the turbine to remain connected to the grid. Additionally it reduces Total Harmonic Distortion to 2%.

Development of Grid-Forming and Grid-Following Inverter Control in Microgrid Network Ensuring Grid Stability and Frequency Response

This paper proposes a control strategy for grid-following inverter control and grid-forming inverter control developed for a Solar Photovoltaic (PV)–battery-integrated microgrid network. A grid-following (GFL) inverter with real and reactive power control in a solar PV-fed system is developed; it uses a Phase Lock Loop (PLL) to track the phase angle of the voltages at the PCC and adopts a vector control strategy to adjust the active and reactive currents that are injected into the power grid. The drawback of a GFL inverter is that it lacks the capability to operate independently when the utility grid is down due to outages or disturbances. The proposed grid-forming (GFM) inverter control with a virtual synchronous machine provides inertia to the grid, generates a stable grid-like voltage and frequency and enables the integration of the grid. The proposed system incorporates a battery energy storage system (BESS) which has inherent energy storage capability and is independent of geographical areas. The GFM control includes voltage and frequency control, enhanced islanding and black start capability and the maintenance of the stability of the grid-integrated system. The proposed model is validated under varying irradiance conditions, load switching, grid outages and temporary faults with fault ride-through (FRT) capability, and fast frequency response and stability are achieved. The proposed model is validated under varying irradiance conditions, load switching, grid outages and line faults incorporating fault ride-through capability in GFM-based control. The proposed controller was simulated in a 100 MW solar PV system and 60 MW BESS using the MATLAB/Simulink 2023 tool, and the experimental setup was validated in a 1 kW grid-connected system. The percentage improvement of the system frequency and voltage with FRT-capable GFM control is 69.3% and 70%, respectively, and the percentage improvement is only 3% for system frequency and 52% for grid voltage in the case of an FRT-capable GFL controller. The simulation and experimental results prove that GFM-based inverter control achieves fast frequency response, and grid stability is also ensured.

Development and Validation of the High-Voltage Direct-Current Modular Multilevel Converter (HVDC-MMC) Model for Converter Transformer Protection Studies.

The electrical protection of power networks with fault contribution from inverter-based power sources imposes new application challenges that have to be dealt with by protection engineers. This paper describes the development of a study case model of an HVDC-MMC link for testing the protection behaviour of connected converter transformers. The paper summarises the implementation and validation of the converter control as well as enhancements to provide Fault Ride-Through capability and fast fault current injection as required by the German Technical Connection Rules for HVDC. The grid code standard requires positive- and negative-sequence reactive current injection in the case of grid faults. A Doubled Decoupled Synchronous Reference Frame Phase Locked Loop (DDSRF-PLL) for Vector Current Control (VCC) is implemented. Additionally, a Fault Detection and Fault Ride-Through Reference Generator with a Current Limitation strategy is introduced. Though these techniques are well described in the literature, the DDSRF is improved for current control stability. The relationship between the parameters of the PLL and the control, as well as the behaviour of the protection system, are demonstrated. Grid faults with large voltage dips pose a significant challenge to the stability of the control system. Nevertheless, it is shown that with the developed model, it is possible to make general statements about the protection behaviour in an inverter-based environment.

Enhancing FRT capability of DFIG based on RC-crowbar considering the resonance and matching control strategies for different fault degrees

This paper compares the problems existing in the current fault ride-through (FRT) schemes of the doubly-fed induction generator (DFIG), and deeply analyzes the transient characteristics of DFIG during FRT. A comprehensive FRT scheme is proposed to improve the FRT capability by using an RC-crowbar and matching control strategy switching. The main innovation of this scheme lies in the consideration of resonance and other factors in the capacitance design of the RC-crowbar. To ensure that the DFIG still has good FRT capability after the RC-crowbar is cut off in advance in the later stage of FRT, an improved rotor side converter (RSC) control strategy is proposed for this situation. At the same time, to balance the reactive power on the stator side and accelerate the recovery of stator voltage throughout the entire FRT period, the control strategy of the grid side converter (GSC) is also improved. The comprehensive FRT scheme proposed in this paper can dynamically switch based on the degree of fault so that it still has good FRT ability when applied to different degrees of faults. Finally, the correctness and effectiveness of the proposed comprehensive FRT scheme were verified through simulation experiments.

Enhancing Fault Ride-Through and Voltage Support Capability for MMC-HVDC Integrated Offshore Wind Farms Based on Multi-Mode Matching

Enhancing Fault Ride-Through and Voltage Support Capability for MMC-HVDC Integrated Offshore Wind Farms Based on Multi-Mode Matching

Grid-Connected Converter With Grid-Forming and Grid-Following Modes Presenting Symmetrical and Asymmetrical Fault Ride-Through Capability

Grid-Connected Converter With Grid-Forming and Grid-Following Modes Presenting Symmetrical and Asymmetrical Fault Ride-Through Capability

Power System Integration of Electric Vehicles: A Review on Impacts and Contributions to the Smart Grid

In recent years, electric vehicles (EVs) have become increasingly popular, bringing about fundamental shifts in transportation to reduce greenhouse effects and accelerate progress toward decarbonization. The role of EVs has also experienced a paradigm shift for future energy networks as an active player in the form of vehicle-to-grid, grid-to-vehicle, and vehicle-to-vehicle technologies. EVs spend a significant part of the day parked and have a remarkable potential to contribute to energy sustainability as backup power units. In this way, EVs can be connected to the grid as stationary power units, providing a range of services to the power grid to increase its reliability and resilience. The available systems show that EVs can be used as alternative energy sources for various network systems like smart grids, microgrids, and virtual power plants besides transportation. While the grid–EV connection offers various contributions, it also has some limitations and effects. In this context, the current study highlights the power system impacts and key contributions of EVs connected to smart grids. Regarding the power system impacts in case of EV integration into smart grids, the challenges and difficulties are categorized under the power system stability, voltage/current distortions, load profile, and power losses. Voltage/current distortions like sags, unbalances, harmonics, and supraharmonics are also detailed in the study. Subsequently, the key contributions to the smart grid in terms of energy management, grid-quality support, grid balancing, and socio-economic impacts are explained. In the energy management part, issues such as power flow, load balancing, and renewable energy integration are elaborated. Then, the fault ride-through capability, reactive power compensation, harmonic mitigation, and grid loss reduction are presented to provide information on power quality enhancement. Lastly, the socio-economic impacts in terms of employment, net billing fees, integration with renewable energy sources, and environmental effects are elucidated in the present study.

Arm integrated double capacitor submodule for modular multilevel solid-state transformers with DC short-circuit fault ride-through capability

Arm integrated double capacitor submodule for modular multilevel solid-state transformers with DC short-circuit fault ride-through capability

Multi-modular bridge-type FCL for enhancing FRT capability of VSC-HVDC connected offshore wind plants during AC faults

This paper presents a novel concept Multi-Modular Bridge-Type Fault Current Limiter (MMBFCL) for enhancing the fault ride-through (FRT) capability in Voltage Source Converter (VSC)-based High-Voltage Direct-Current (HVDC) systems. The MMBFCL can be directly connected to HVDC system in ac grid side without series connection of semiconductor switches and series injection transformers. Also, the limiting resistor of each module is determined based on binary arrangements to provide a multi-step insertion resistor BFCL to limit the fault current and enhance the FRT capability under different voltage sag levels. The principle operation and control system of the MMBFCL is described. Then, the performance of the MMBFCL for enhancing the FRT is validated through time domain simulations by PSCAD/EMTDC software in a HVDC integrated wind farm system. Also, the performance of the MMBFCL is compared with the single-modular BFCL (SMBFCL). Simulation results reveal that the MMBFCL compensate the voltage sag for each voltage sag levels without any over voltage at the HVDC terminal. Also, it has superior performance than SMBFCL.

Enhancement of fault ride-through capability of three-level NPC converter-based HVDC system through robust nonlinear control strategy

Voltage source converter-based high-voltage direct current (VSC-HVDC) transmission systems are becoming increasingly popular for long-distance power transmission due to their numerous advantages. However, the fault ride-through (FRT) capabil-ity of VSC-HVDC systems during AC faults remains a key challenge that needs to be addressed to ensure their uninterrupted operation under challenging grid conditions. This paper presents and analyzes a novel nonlinear control scheme based on a robust sliding mode control approach to improve the FRT capability of VSC-HVDC systems. The proposed control scheme based on the modification of the converter’s active power to make it more sensitive to any changes in voltage magnitude at the points of common coupling (PCCs) on the AC side. This helps to maintain the DC voltage sta-bility and prevent the converter from tripping during AC faults. The performance of the proposed control scheme is evaluated using a series of ex-perimental investigations using a digital signal processor (DSP) within Processor-in-the-Loop (PIL) quasi-real-time simulation. The PIL simulations closely examine the system’s response to AC faults with varying remaining voltages and durations. The results demonstrate that the proposed control scheme can effectively improve the FRT capability of VSC-HVDC systems and ensure their stable operation during AC faults.

Experimental study on fault ride-through capability of VSC-based HVDC transmission system

Experimental study on fault ride-through capability of VSC-based HVDC transmission system

Analysis of Fault Ride through the Improvement of PV Power Plant Based on Capacitive Bridge Fault Current Limiter Using Machine Learning

Photovoltaic power plant (PVPP) has increased importance among renewable energy sources due to their ability to be connected more easily to a modern power grid. However, the reliability and stability operation of a grid-connected PVPP system is very important to ensure even during grid faults. In this study, a capacitive bridge fault current limiter (CBFCL) using a machine learning (ML) method is applied to enhance the fault ride-through (FRT) capability of a grid-connected PVPP system. Three different protection methods called DC chopper, CBFCL, and DC chopper + CBFCL are designed to prevent the harmful effects of overcurrent that occurs during grid faults to protect the grid-connected PVPP system. The ML algorithm can be trained on historical data to predict optimum control parameters based on real-time conditions such as normal and fault operations of the grid-connected PVPP system. An ensemble classification algorithm has the best results among the four classification algorithms in machine learning methods. The ensemble classification algorithm is separately implemented into the control systems of three protection strategies. Bagged Trees and Subspace KNN classifiers in ensemble classification methods have obtained an impressive accuracy of 98% in ML classification methods. The simulation results illustrate that the DC chopper + CBFCL based ensemble provides the best protection for the grid-connected PVPP system compared to other protection systems.

Modeling and Simulation of Energy Storage Performance of Renewable Energy Storage System

In recent times, there has been a notable increase in attention towards the reduction of greenhouse gas emissions and the enhancement of energy security. Over the past decade, there has been a significant increase in the incorporation of intermittent renewable energy sources (RESs), such as photovoltaic (PV) and wind energy, into the existing power system. However, the integration of this system hinders the reliable and steady running of the grid due to many operational and control challenges. Several challenges exist, including generation uncertainty, voltage and angular stability, power quality issues, reactive power support, and fault ride-through capabilities. The electricity produced by renewable energy sources (RESs) exhibits fluctuations due to meteorological phenomena beyond human control, such as wind speed and sunlight intensity. Energy storage systems (ESSs) play a crucial role in mitigating volatility by effectively storing excess electricity generated and facilitating its availability when needed. This study utilises the MATLAB/Simulink programme to develop an optimised configuration model for the wind hybrid power storage system.