Fault Ride Research Articles

Investigation of condition monitoring system for grid connected photovoltaic (GCPV) system with power electronics converters using machine learning techniques

Power systems protection has become more vital in recent years to ensure stability, reliability, security, and power quality due to the exponential growth of grid-connected photovoltaic (GCPV) systems. As a result, several nations have set new grid codes for the grid integration of PV plant installations to overcome these concerns. Investigating Fault Ride Through (FRT) capacity is one of the primary criteria for grid codes. For 3-phase GCPV systems, fault detection and classification approaches are proposed in this study. Firstly, different faults that occurred in the GCPV system are categorized and compared, with the critical and analytical evaluation of grid codes, particularly FRT requirements such as Low Voltage Ride Through (LVRT) and High Voltage Ride Through (HVRT) for different nations. Further, a detailed classification and a comparison of the existing FRT techniques are presented for better control methods based on system complexity, detection accuracy, and other evolutionary criteria. To ensure smooth grid operation, accurate fault detection and condition monitoring of the systems are required. This paper discusses a machine learning (ML) based technique for detecting faults in 3-phase GCPV systems. Multi-peak phenomena caused by FRT capabilities and anti-islanding detection are the main problems experienced while integrating a PV system into the local grid. The fault classification technique is developed using weighted K-nearest neighbor (WKNN) and fine Gaussian support vector machine (FGSVM) based ML approaches utilizing Wavelet Transform. The proposed ML-based findings show that the fault detection algorithm-based classification accuracy has significantly improved.

Study of the Crowbar's Functioning in Doubly Fed Induction Wind Generators: Towards Achieving Fault Ride Through Capability

This work examines the analysis of temporary behaviors and crowbar hardware layout for enhancing the fault ride-through capability (FRTC) in doubly fed induction wind generators (DFIWGs) A crowbar that is linked in parallel to the rotor side converter (RSC) is a feature found on the majority of DFIWGs these days to safeguard the RSC and DC-bus capacitor (DCBC). Previous studies demonstrated that the crowbar resistance has an impact on the DFIWG transient response's oscillations and peak values. In order to satisfy the FRTC criterion, the article initially methodically examines the DFIWG dynamics with and without a crowbar during a 100% voltage dip and studies the effects of two resistance values on the DCBC. It has been demonstrated that choosing a crowbar resistance greater than the permitted range may cause the DFIG FRT performance to decline. By actively addressing grid faults and improving performance, stability, and dependability, this integrated crowbar shows the potential of state-of-the-art control approaches for the dependable and efficient use of DFIWGs. MATLAB/Simulink is used to run robust simulations, and the results unambiguously show that the proposed model may significantly improve the FRTC of DFIWGs.

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%.

Intelligent Control of the Dynamic Voltage Restorer for Fault Ride Through Capability Enhancement of a Grid-Connected Photovoltaic Power Plant in accordance with Recent Moroccan Grid Code

Background: The recent development of small-scale, decentralized generation from renewable sources and the fall in the price of the equipment needed for this operation have given a new role to the distribution networks, which is to collect the energy produced by the smallest generation plants and deliver it to the end customers. However, the national Grid Codes present technical requirements in terms of FRT and particularly LVRT and HVRT which are imposed on PV plants connected to medium voltage distribution networks, to ensure the energy needed by the loads connected to the network at the time of the failure and especially sensitive ones. Methods: In this paper, an intelligent neural network approach is applied to the DVR control circuit to enable the requirements of the sensitive load connected near the PCC, and the system is tested in the presence of a non-linear load to demonstrate its efficiency for all situations. The proposed strategy is based on the implementation of an improved ANFIS and ANN control which are compared to a tuned PI controller, the approach intends to meet the technical requirement of the recently approved Grid Code in Morocco. The simulation is performed using MATLAB Simulink. Results: The proposed approach brings great improvement to the load side voltage waveforms, and numerical experiment findings demonstrate that it can successfully guarantee the technical requirements of the electrical grid code. Conclusion: The results obtained show better behavior of the system using ANFIS and ANN control strategy in the presence of a nonlinear load and a significant improvement of the voltage THD.

VSC- based HVDC System Capability to Ride Through Faults

VSC-HVDC is becoming an increasingly attractive technology for power network development. In order to establish itself a viable alternative it still has to address some issues, e.g., its response under fault situations on both AC and DC side. This paper makes a state-of-the-art review on how different converter topologies affect the Fault Ride Through (FRT) ability of the system. By comparing the different converter topologies, it is possible to underline the features that will be able to guarantee a successful FRT, which can be very helpful in order to choose the most suitable converter topology for different applications.

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.

Crowbar Protection Scheme for Fault Ride Through in a Doubly-fed Induction Generator

This study focusses on using a crowbar protection scheme to overcome the symmetrical voltage dips in a doubly fed induction generator (DFIG). The crowbar protection scheme is integrated into the wind energy conversion system of the DFIG. The implementation of this scheme provides automated fault ride-through during sudden transients which may otherwise lead to over current faults. The increased use of renewable sources for electricity generation leads to a reduction in pollution which directly benefits the environment. Sustained usage of renewable resources will be beneficial for the environment.

Addressing the Security risk of a Massive Deployment of Photovoltaic Power for Electric Power Systems

Future electric power systems will incorporate a high percentage of Photovoltaic (PV) power generation as a means of mitigating environmental issues including global warming and energy depletion. The author observes that if the increase in uncertainties brought about by the PV penetration cannot be prevented, then it will be difficult to carry out the N-1 security level. To ensure the N-1 security requirement is met despite the uncertainties, paper has suggested a new notion of "robust power system security" along with many conditions to be met. In this research, and offer a model of uncertainties caused by PV generation, and use robust power system security to guide our choice of parameters. Next, simulate the system to learn more about, how PV and load disconnections affect stability, and how Fault Ride Through (FRT) and Dynamic Voltage Support (DVS) influence stability. Finally, it is demonstrated that the massive penetration of PV would significantly raise the complexity of burden jobs in future power system operation planning and real-time operation.

Investigation of Transient Stability in Power System with Improved FRT Capable Solar PV Inverters

Most regions of the world have seen tremendous growth in distributed energy resources, especially photovoltaic (PV) generation. The penetration of PV generation into the power grid is high and hence it has a major impact in power system. The integration of solar PV plant into the power system has both negative as well as positive impacts on transient stability of the power system during faults. In this work, the proposed current amplitude limiting based Fault Ride Through (FRT) control algorithm is implemented in large scale power systems and enhancement of transient stability is also studied in terms of synchronous machine side and grid side parameters namely rotor speed deviation, load angle, relative rotor angle, active and reactive power. The transient stability of large-scale Grid Connected solar PV (GCPV) system is discussed in this article, when the system is incorporated with the proposed FRT control strategy. The large scale GCPV system is said to be stable, if the angular displacement between the machines in the system stays within predetermined limits. The parameters considered for transient analysis on the synchronous machine side are the rotor angle, rotor speed, and Critical Clearing Time. The proposed model is simulated in MATLAB Simulink and validated in 1 kW hardware setup of grid connected PV system which performs satisfactorily in terms of system parameters and transient stability improvement.

Fault Ride Through approach for Grid-Connected Photovoltaic System

This paper presents a fault ride-through approach for grid-connected photovoltaic (PV) systems, aimed at improving the system's response during voltage sags and limiting the maximum inverter current during symmetrical faults. A constant active current reactive power injection approach was developed for low-voltage ride-through (LVRT) operation of grid-connected solar PV inverters in low voltage grids. The method manages the active and reactive power references and satisfies grid code requirements while also addressing tripping problems caused by overcurrent. The approach improves the speed response of the power converters during voltage sags, resulting in better dynamic grid support. The authors evaluated the approach using a 2-kW single-phase grid-connected PV system and demonstrated its ability to inject the required reactive power during a fault to improve the voltage profile and achieve dynamic grid support requirements. The accuracy of the proposed methodology is identified to be 98.3%, and the detection time is reduced by a reasonable margin in accordance with the grid standards. Overall, the fault ride-through approach can enhance the performance and reliability of grid-connected PV systems, particularly in low voltage grids.

Analysis of Doubly Fed Induction Generator-based wind turbine system for fault ride through capability investigations

A Doubly Fed Induction Generator has a stator winding directly coupled with grid whereas rotor is to the grid via a fault-prone converter. In early times, when a fault occurred, these generators were required to disengage from the grid. However, due to the increased penetration, grid operators demanded WTs remain connected to the grid. Thus, this paperwork integrates crowbar protection with a Battery Energy Storage System (BESS) to improve Fault Ride Through (FRT) capability. For performance evaluation under transient conditions, a three-phase symmetrical fault is imposed at a time of 2 seconds. By using the suggested technique, the DC-link voltage is observed to improve and remain at 1150 V with minor fluctuation. Likewise, the stator and rotor currents are observed to remain at their nominal value after 2.15 seconds. MATLAB-Simulink software is used for modeling and simulation by obtaining all the system’s actual parameters from ADAMA-II Wind Farm.

An Enhanced AC Fault Ride through Scheme for Offshore Wind-Based MMC-HVDC System

This study presents an improved, communication-free Fault Ride-Through (FRT) strategy for type-3 and type-4 wind turbine integrated modular multilevel converter-based high-voltage direct current (MMC-HVDC) systems in offshore wind power plants (OWPPs). The research aims to enhance the reliability and resilience of OWPPs by ensuring their connection with AC grids remains intact during and after faults. Simulation results conducted on a 580 kV, 850 MW MMC-HVDC system using PSCAD/EMTDC software v.4.6.2 demonstrate quick post-fault recovery operation and the ability to effectively manage DC link and capacitor voltages within safe limits. Furthermore, the circulating current (CC) and capacitor voltage ripple (CVR) remain within acceptable limits, ensuring safe and reliable operation. The study’s major conclusion is that the proposed FRT strategy effectively mitigates the adverse effects of short circuit faults, such as a rapid rise in DC-link voltage, on the performance of the MMC-HVDC system. By promptly suppressing DC-link overvoltage, the proposed FRT scheme prevents compromising the safe operation of various power electronics equipment. These findings highlight the significance of FRT capability in OWPPs and emphasize the practical applicability of the proposed strategy in enhancing the reliability of offshore wind power generation.

Bipolar Cascaded Modular H7 Current Source Converter for HVDC Grid With Simple DC Fault Ride Through Capability

Nowadays, one of the major challenges to develop the HVDC grid is the effective and economical dc fault protection technique, which is normally realized by the dc circuit breakers (DCCBs). However, the dc circuit breaker is quite complex and expensive. Therefore, to explore an alternative solution, this paper proposes a bipolar cascaded modular H7 current source converter for HVDC grid with simple dc fault ride through capability and then analyzes its dc fault behavior and consequently proposes the protection scheme, which can reduce the design requirement of DCCBs, even handle dc faults only with mechanical switches. PSCAD simulation and experiment results are demonstrated to validate the feasibility of the proposed topology and fault protection scheme.

Cooperative Fault Ride Through Strategy for Paralleled Grid-Tied Converters

Parallel systems are the trend of the grid-tied converters, which can improve the transmission power. Under fault conditions, the operation of the converter needs to be switched safely to ensure no disconnection. The cooperation between multiple converters can better cope with fault conditions and support the grid voltage. This paper proposes a coordinated fault ride through strategy. This strategy can ensure that the converters transfer the required reactive power into the grid according to their ability, and calculates the current feasible region. The residual capacity is used to transmit photovoltaic power within the current feasible region. Thus, the converters can operate within the safety region and help to restore the grid voltage. Simulation results verify the correctness of the proposed strategy.

Design of an Optimal Adoptive Fault Ride through Scheme for Overcurrent Protection of Grid-Forming Inverter-Based Resources under Symmetrical Faults

As the integration of inverter-based resources (IBRs) is rapidly increasing in regard to the existing power system, switching from grid-following (GFL) to grid-forming (GFM) inverter control is the solution to maintain grid resilience. However, additional overcurrent protection, especially during fault transition, is required due to limited overcurrent capability and the high magnitude of spikes during fault recovery in IBRs, specifically in the GFM control mode. Furthermore, the power system stability should not be compromised by the employment of additional fault ride through (FRT) schemes. This article presents the design and implementation of an adoptive fault ride through (FRT) scheme for grid-forming inverters under symmetrical fault conditions. The proposed adoptive FRT scheme is comprised of two cascaded power electronic-based circuits, i.e., fault current ride through and a spikes reactor. This adoptive FRT scheme optimizes the fault variables during the fault time and suppresses the fault clearing spikes, without affecting system stability. A three-bus inverter-based grid-forming model is used in MATLAB/Simulink for the implementation of the proposed scheme. Further, a conventionally used FRT scheme, which includes fault current reactors, is simulated in the same test environment for justification of the proposed adoptive scheme. The adoptive FRT scheme is simulated for both time domain and frequency domain to analyze the response of harmonic distortion with the suppression of the fault current. Moreover, the proposed scheme is also simulated under the GFL mode of IBRs to justify the reliability of the scheme. The overall simulation results and performance evaluation indices authenticate the optimal, fault tolerant, harmonic, and spike-free behavior of the proposed scheme at both the AC and DC side of the grid-forming inverters.

Enhancing the Power Quality of Grid Connected Photovoltaic System during Fault Ride Through: A Comprehensive Overview

Enhancing the Power Quality of Grid Connected Photovoltaic System during Fault Ride Through: A Comprehensive Overview

Symmetrical Multi-pole MMC-HVDC with DC Fault Ride Through Capability Using HBSM

—The modular multilevel converter (MMC) has proven to be the most advanced voltage source converter (VSC). For long-distance power transfer, high-voltage DC (HVDC) is the best choice. Across the globe, electric power networks are witnessing rapid growth in MMC-HVDC installation to meet the ever-growing power demand. The existing AC transmission lines can be converted to DC lines by adding converters. The MMC-based multi-pole HVDC presents an adequate solution for upgradation. However, more study is required to make it a reality. The present paper attempts to bridge this gap. The proposed study can be divided into two parts. Initially, the concept of symmetrical multi-pole MMC-HVDC is proposed, and its mathematical relations have been derived. The multi-pole has been subdivided into an even and an odd configuration. The half-bridge submodule (HBSM)-based MMC lacks DC fault handling capability. The second part of the study includes controller and fault analysis of the HBSM-based tri-pole MMC HVDC. The study shows the severity of the pole-to-pole faults, leading to a complete shutdown of the transmission line. A controller and an algorithm for the DC fault-ride-through (FRT) have been proposed. The proposed controller has digital switches to temporarily bypass the real-time measurement values with measurements taken under healthy conditions. An impact analysis of the parameters of one MMC on the equilibrium of the entire multi-pole configuration is performed. The performance of the proposed controller has been carried out on a real-time digital simulator (RTDS). The proposed controller and FRT algorithm ensure that the tri-pole HVDC maintains the power supply during all DC faults. In the worst-case scenario, the shutdown is averted with a 50% reduction in power transfer capability. The transients in active and reactive power are minimized and eliminated within a cycle. Further, using the most economical and simplest submodule ensures the configuration without any additional cost.

Real-Time Simulation and Energy Management Attainment of Microgrids

The rapid spread of Microgrid systems has led to the need for an intensive analysis of the system to avoid several challenges such as stability, reliability, power balance, and other aspects. In this context, real-time simulation plays a vital role in the overall system study before the actual implementation stage. This helps avoid many on-site problems of the Microgrid by simulating the system and studying different operation scenarios. This paper uses the OPAL-RT simulator to perform a real-time simulation of an MG case study. Furthermore, it examines the implementation of the Fault Ride Through technique to overcome the total disconnection of the PV system following unpredictable faults. Moreover, a Load curtailment solution method is proposed in this study, to meet the balance and stable operation of the MG. The results prove the effectiveness of both techniques, with FRT implementation reducing the losses by about 62%, and the Load curtailment algorithm maintaining the balance of the MG.

Optimization-Based Methodology to Design the MMC's Sub-Module Capacitors

This paper proposes an optimization-based size reduction methodology for Modular Multilevel Converters (MMC), focusing on minimizing the converter's sub-module capacitor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{SM}$</tex-math></inline-formula> . The analysis is performed considering both the converter's current and voltage limitations and the Transmission System Operator (TSO) Fault Ride Through (FRT) requirements. By means of a steady-state analysis, the time-domain expressions of the converter's arms energies are obtained and their behavior throughout the MMC's operating range is shown. Based on these expressions, the optimization-based problem to reduce the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{SM}$</tex-math></inline-formula> size is developed and its constraints are imposed to ensure that the converter's voltage and current levels are within its design limitations. The suggested method is compared with different approaches for distinct active and reactive power set-points, where it is shown that the SM capacitor size can be reduced up to 24% in comparison with the method with worst performance and up to 7% regarding the best method used for comparison purposes. Furthermore, time-domain simulations of the MMC considering several AC voltage sags are performed in order to demonstrate that the dynamics of the SM capacitor and the arm applied voltages are within acceptable margins during the different operations.

A Novel Protection Method to Enhance the Grid-Connected Capability of DFIG based on Wind Turbines

This paper proposes a robust protection technology to enhance the grid-connected capability of the doubly fed induction generator (DFIG) based on wind turbines (WTs) under low voltage ride through (LVRT) conditions. The proposed method to control the rotor side converter (RSC) and grid side converter (GSC) uses proportional–integral (PI) controllers. The protection devices are the static compensator (STATCOM), crowbar, series dynamic resistor (SDR), and DC-chopper, with the proposed method to control STATCOM using proportional–integral (PI) controllers and the proposed method to control the rest of the protection devices based on the allowable threshold values of rotor current and DC-link voltage. The protection coordination strategy between them is proposed to avoid the disconnection between the rotor circuit and grid, maintain the DC-link at constant voltage, enhance the dynamic response of WT, and improve the voltage response at the point of common coupling (PCC) of WT. The DFIG-WT of 2 MW-575 V connecting to the 34-bus IEEE network is carried out to verify the effectiveness of the proposed method under the conditions of symmetrical and asymmetrical faults, and the LVRT requirements of the Spanish grid code are considered. The obtained simulation results using the PSCAD/EMTDC software show that the rotor current, DC-link voltage, voltage PCC, and power oscillation damping are significantly improved compared to not using it or applying the conventional method based on passivity theory. Therefore, the LVRT capability of the proposed DFIG-WT system is significantly enhanced, and it has enough ability to continue to provide electrical energy to the power network. Abbreviation DFIG, Doubly Fed Induction Generator; DVR, Dynamic Voltage Restorer; FACTS, Flexible AC Transmission System; FRT, Fault Ride Through; FS-WT, Fixed-Speed Wind Turbine; GSC, Grid Side Converter; LVRT, Low Voltage Ride Through; PCC, Point of Common Coupling; PI, Proportional–Integral; PMSG, Permanent Magnet Synchronous Generator; PWM, Pulse Width Modulated; RSC, Rotor Side Converter; SDR, Series Dynamic Resistor; STATCOM, Static Compensator; SVC, Static Var Compensator; UPFC, Unified Power Flow Controller; VS-WT, Variable-Speed Wind Turbine; SLG, Single Line-to-Ground; LL, Line-to-Line; LLG, Double Line-to-Ground; WT, Wind Turbine