Low-voltage Ride-through Capability Enhancement Research Articles

Marine Predator Algorithm-Based Optimal PI Controllers for LVRT Capability Enhancement of Grid-Connected PV Systems.

Photovoltaic (PV) systems are becoming essential to our energy landscape as renewable energy sources become more widely integrated into power networks. Preserving grid stability, especially during voltage sags, is one of the significant difficulties confronting the implementation of these technologies. This attribute is referred to as low-voltage ride-through (LVRT). To overcome this issue, adopting a Proportional-Integral (PI) controller, a control system standard, is proving to be an efficient solution. This paper provides a unique algorithm-based approach of the Marine Predator Algorithm (MPA) for optimized tuning of the used PI controller, mainly focusing on inverter control, to improve the LVRT of the grid, leading to improvements in the overshoot, undershoot, settling time, and steady-state response of the system. The fitness function is optimized using the MPA to determine the settings of the PI controller. This process helps to optimally design the controllers optimally, thus improving the inverter control and performance and enhancing the system's LVRT capability. The methodology is tested in case of a 3L-G fault. To test its validity, the proposed approach is compared with rival standard optimization-based PI controllers, namely Grey Wolf Optimization and Particle Swarm Optimization. The comparison shows that the used algorithm provides better results with a higher convergence rate with overshoot ranging from 14% to 40% less in the case of DC-Link Voltage and active power and also settling times in the case of MPA being less than PSO and GWO by 0.76 to 0.95 s.

Enhancement of low-voltage ride-through capability for virtual synchronous generators based on virtual impedance voltage control

Virtual Synchronous Generator (VSG)-based grid-forming converters (GFC) increasingly serve as interfaces between renewable energy resources and the power grids with high penetration. Although the emulation of the characteristics of Synchronous Generator (SG) enables GFC to provide virtual inertia and oscillation damping under the VSG control, it remains challenging to replicate the short-circuit behaviors of SGs under the grid voltage sag/recovery conditions. The existing technologies are limited and lack full functionalities in terms of power synchronization, overcurrent suppression and capability of dealing with asymmetric grid-faults. This paper presents a Virtual Impedance Voltage Control (VIVC) strategy to enhance the fault-ride-through capability of the converter under a variety of fault conditions. In the case of asymmetric faults, a negative-sequence current control is performed to mitigate the negative-sequence voltages and achieve the grid current balance. The fault current is restrained and the power synchronization is improved by the virtual reactance without oversizing the GFC. The simulation and experimental results validate the effectiveness of the proposed control strategies.

Enhancement of LVRT Capability in DFIG-Based Wind Turbines with STATCOM and Supercapacitor

Overvoltage and overcurrent resulting from various faults cause instability in Doubly Fed Induction Generator (DFIG)-based wind turbines connected to a grid. The grid code requirement must be met during faults to minimize the effect of these problems. Low Voltage Ride Through (LVRT) capability is used to meet the grid code requirement. It is important to use coordinate control for transient states in LVRT capability. This study aimed to improve the stator dynamics for ease of calculation and the rotor dynamic model by damping oscillations caused by balanced and unbalanced faults on the grid side. For this, electromotive force (emf) models were developed for stator and rotor dynamic modeling. Furthermore, for the coordinate control of the DFIG, models were developed for a lookup-table-based supercapacitor and a decoupled Static Synchronous Compensator (STATCOM). Using these models, analyses of three-phase and two-phase faults were conducted. Following different balanced and unbalanced faults within the grid, the system was stabilized in a short time, and the oscillations occurring during the faults were quickly damped using the LVRT models developed in this study.

RETRACTION NOTICE: Low-voltage ride-through capability enhancement of wind energy conversion system using an ant-lion recurrent neural network controller

RETRACTION NOTICE: Low-voltage ride-through capability enhancement of wind energy conversion system using an ant-lion recurrent neural network controller

Augmentation of Low Voltage Ride through (LVRT) Capability using ANN based electric spring for a Grid-tied Wind Energy Conversion System

Electric Spring (ES) is an innovative approach for distributed voltage control (DVC) whereas at the same time accomplishing nominal demand-side management (DSM) technique for continuously varying renewable energy sources. In order to demonstrate the efficiency of ES when deployed in enormous quantities across the grid-connected power distribution system, it is important to build easy and reliable simulation models of ES that can be integrated into large-scale simulation studies of the power system. The ES study gap identification method defines the ES dynamic simulation methodology that is appropriate for the WECS grid-connected voltage and frequency control studies. The integration of WECS to the electric grid leads to many serious power quality problems. Low voltage ride through (LVRT) capability improvement is one of the important constraints in grid connected WECS. This articleexamines the enhancement of LVRT capability of Doubly Fed Induction Generator (DFIG) based grid connected WECS by usingES. The effectiveness of proposed Artificial Neural Network (ANN) based Electric spring controller is compared with existing PI controller using MATLAB/Simulink software. It is evident that the proposed controller nurtures the trustworthiness of WECS when integrated with existing electric power grid system.

Coordinated Sequential Control of Individual Generators for Large-Scale DFIG-Based Wind Farms

To enhance the Low-voltage Ride Through (LVRT) capability of large-scale centralized wind farms is essential for the safety of the wind farm and the security of the power system. However, the LVRT capability enhancement coordinating the control and protection of individual wind generators merits consideration. To contribute in this way, a Coordinated Sequential Control (CSC) strategy is proposed in this manuscript. Regarding different voltage disturbance scenarios, the goal of voltage control is determined in real-time. To keep as many wind turbines operating grid-connected as possible, a multi-staged coordination strategy is set according to the critical time to ride through the fault. The reactive power control and the shedding of the wind turbines are coordinated in the three stages of the CSC. According to the simulation results, more wind turbines can be kept grid-connected by using the proposed control strategy. Comparison studies are made among several types of coordinating strategies, emphasizing the advantages of the proposed method in terms of both validation and real-time performance.

Low-Voltage Ride-Through Techniques in DFIG-Based Wind Turbines: A Review

In recent years, considerable advances were made in wind power generation. The growing penetration of wind power makes it necessary for wind turbines to maintain continuous operation during voltage dips, which is stated as the low-voltage ride-through (LVRT) capability. Doubly fed induction generator (DFIG)-based wind turbines (DFIG-WTs), which are widely used in wind power generation, are sensitive to disturbances from the power grid. Therefore, several kinds of protection circuits and control methods are applied to DFIG-WTs for LVRT capability enhancement. This paper gives a comprehensive review and evaluation of the proposed LVRT solutions used in DFIG-WTs, including external retrofit methods and internal control techniques. In addition, future trends of LVRT solutions are also discussed in this paper.

Enhancement of low-voltage ride-through capability of permanent magnet synchronous generator wind turbine by applying state-estimation technique

Purpose The purpose of this study is to propose a control scheme based on state estimation algorithm to improve zero or low-voltage ride-through capability of permanent magnet synchronous generator (PMSG) wind turbine. Design/methodology/approach Based on the updated grid codes, during and after faults, it is necessary to ensure wind energy generation in the network. PMSG is a type of wind energy technology that is growing rapidly in the network. The control scheme based on extended Kalman filter (EKF) is proposed to improve the low voltage ride-through (LVRT) capability of the PMSG. In the control scheme, because the state estimation algorithm is applied, the requirement of DC link voltage measurement device and generator speed sensor is removed. Furthermore, by applying this technique, the extent of possible noise on measurement tools is reduced. Findings In the proposed control scheme, zero or low-voltage ride-through capability of PMSG is enhanced. Furthermore, the requirement of DC link voltage measurement device and generator speed sensor is removed and the amount of possible noise on the measurement tools is minimized. To evaluate the ability of the proposed method, four different cases, including short and long duration short circuit fault close to PMSG in the presence and absence of measurement noise are studied. The results confirm the superiority of the proposed method. Originality/value This study introduces EKF to enhance LVRT capability of a PMSG wind turbine.

Enhancement of DFIG LVRT Capability During Extreme Short-Wind Gust Events Using SMES Technology

Wind energy is one of the premier renewable energy sources that have gained popularity during the last decade. Among the currently available wind energy conversion systems (WECS), doubly fed induction generator-based technology has been widely employed due to its superior advantageous. The key features of the DFIG-based WECS include its ability to capture more wind energy and support the grid with large reactive power during short disturbance events. On the other hand, DFIG is very sensitive to grid faults which affect its fault ride through (FRT) capability. Furthermore, extreme wind gust even for short durations may lead to the violation of the low voltage ride through (LVRT) threshold limits set by worldwide transmission line operators. This situation cannot be mitigated by the turbine blades pitch controller since the response of the pitch mechanical control is much slower than the rapid dynamic change in the wind speed during short duration of wind gust events. While DFIG FRT capability has been discussed in several papers in the literature, not much attention was given to the mitigation of the effects of extreme wind gust of short duration on the DFIG performance. In this paper, the effect of various levels of wind gust on the performance of a DFIG-based wind energy conversion grid-connected system is investigated and mitigated using a new controller for superconducting magnetic energy storage (SMES) unit. A combination of hysteresis current and fuzzy logic controllers is employed to control the voltage source converter and the DC-DC chopper interfacing the SMES coil with the investigated system. Simulation results reveal the effectiveness of the proposed SMES controller that can be easily implemented within existing as well as new WECS installations.

An integrated reactive power control strategy for improving low voltage ride-through capability

Among all renewable energies, wind power is rapidly growing, whereby it has the most participation to supply power. Doubly fed induction generator (DFIG) is the most popular wind turbine, as it can play a very significant role to enhance low voltage ride through (LVRT) capability. Ancillary services such as voltage control and reactive power capability are the main topics in wind power control systems that should be handled profoundly and carefully. The lack of reactive power during fault period can result in instability in generators and/or disconnection of the wind turbine from the power system. The main aims of this study are to illustrate the most effective approaches subject to improve the efficiency, stability, and reliability of wind power plant associated with LVRT capability enhancement. This effectiveness and efficiency are demonstrated by, firstly, comparison between all types of wind turbines, focusing on the ancillary services, after the existing advanced control strategies. According to the literature, there is a consensus that modifying converter-based control topology is the most effective approach to enhance LVRT capability in DFIG-based wind turbine (WT). Therefore, an advanced integrated control strategy is designed by considering the effect of the rotor side converter (RSC) and the grid side converter (GSC). A model of the wind power plant is presented based on the control objectives. MATLAB/Simulink is also used to illustrate the effectiveness of the designed algorithm.

LVRT capability enhancement of DFIG based wind turbine with coordination control of dynamic voltage restorer and inductive fault current limiter.

According to the coordination control of a dynamic voltage restorer (DVR) and an inductive fault current limiter (FCL), this paper proposes an efficient low-voltage ride-through (LVRT) scheme for a doubly fed induction generator (DFIG) based wind turbine. The DVR is located to the DFIG’s stator circuit for stabilizing the terminal voltage and decreasing the generator current. The inductive FCL is connected to the DFIG’s rotor circuit for suppressing the rotor overcurrent and protecting the converter. Theoretical discussions on structure, principle and scale criterion of the combined DVR-FCL are conducted, and simulation analyses of the proposed approach to handle symmetrical and asymmetrical faults are done in MATLAB/Simulink. In this study, the dynamic characteristics of the DFIG during the faults are analyzed from multiple aspects, and a detailed comparison of the proposed approach and the single action of DVR or FCL is carried out. From the simulation results, the effectiveness and superiority of the proposed approach are well demonstrated.

RETRACTED: Low-voltage ride-through capability enhancement of wind energy conversion system using an ant-lion recurrent neural network controller

This paper proposes a hybrid controller to improve the low-voltage ride-through ability of the grid-connected wind energy conversion system. The hybrid controller is the joined execution of the ant-lion optimizer with the recurrent neural network called the ant-lion recurrent neural network. At voltage drop and fault conditions, the proposed control technique guarantees the low-voltage ride-through ability of the wind energy conversion system. The ant-lion optimizer in the perspective of objective function approach will be utilized in the offline manner to distinguish the optimal solutions from the accessible looking space and it makes the training dataset. Identifying the low-voltage ride-through ability, the ant-lion optimizer method considers voltage, current, and real and reactive power. Using these parameters, the objective function of the ant-lion optimizer strategy is described and explained. The recurrent neural network predicts the best possible control signals of grid-side and generator-side converters in light of the achieved dataset. The proposed method is utilized for system regulation and instability problem of voltage amid the fault conditions. In this way, the system’s low-voltage ride-through capability is upgraded and besides, the many-sided quality is diminished with the help of the proposed strategy. By applying the comparative investigation with the existing approaches, the proposed control procedure is actualized in the MATLAB/Simulink working stage and the performances are assessed.

Application of a Superconducting Fault Current Limiter to Enhance the Low-Voltage Ride-Through Capability of Wind Turbine Generators

The penetration of wind turbine generators onto the grid has grown worldwide at unprecedented rates in recent years. This raises the concern that the tripping of wind turbine generators could potentially cause system collapses. To alleviate these concerns, wind turbine generators need to maintain connection with the grid when a grid fault occurs. This has provoked many countries to adopt low-voltage ride-through (LVRT) for wind turbine generators. The LVRT is the capability of wind turbine generators to maintain connectivity during certain periods of voltage sag. The wind turbine generators should be connected to the grid to support fault recovery. Also, wind turbine generators must provide reactive power according to the grid voltage sag. Therefore, much research has been focused on enhancing LVRT capability. To enhance LVRT capability, this paper proposes the application of a superconducting fault current limiter (SFCL) in the system. The fault current was suppressed and the voltage sag was improved through the application of the SFCL. By improving the voltage sag, the wind turbine generator and the grid were able to maintain a connection. However, suppression of the fault current can cause a problem in the overcurrent relay (OCR) trip time delay. The trip time delay was solved by OCR resetting. Through a power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC), the enhancement of LVRT capability and improvement of the trip delay was confirmed.

An adaptive control strategy of crowbar for the low voltage ride-through capability enhancement of DFIG

Abstract Doubly-fed induction generator (DFIG) is sensitive to the disturbance of grid voltage, and its low voltage ride-through (LVRT) technology is still a hotspot issue. Rotor side crowbar is widely used to realize LVRT. However, traditional fixed crowbar can’t strike a balance between the limitation of rotor over current and DC-bus over voltage, and the crowbar is usually activated repeatedly due to the inappropriate deactivation strategy. Based on the analysis of rotor current considering crowbar operations, an improved LVRT method that dynamically adjusting crowbar resistance and adaptively deactivating the crowbar circuit is proposed. The corresponding adaptive control strategy and the resistance setting method are given. With the proposed scheme, both the rotor current and DC-bus voltage can be controlled within the restriction. Besides, the crowbar can be deactivated in the least time under the precondition of avoiding being reactivated, which will effectively reduce the absorbed reactive power from the system and benefit the service life of switching devices. The effectiveness of proposed LVRT scheme is verified by MATLAB/Simulink simulation.

LVRT capability enhancement of DFIG-based wind farms by using capacitive DC reactor-type fault current limiter

Low-voltage ride-through (LVRT) is the core of grid code requirements for grid connection of wind farms (WFs). This paper presents a capacitive DC reactor-type fault current limiter (CDRFCL) for LVRT capability enhancement of doubly-fed induction generator (DFIG)-based WFs. The CDRFCL is based on the conventional DC reactor-type fault current limiter (DRFCL), which is modified to overcome its limitations of operation and is adapted with the WF environment. To check the effectiveness of the proposed CDRFCL, its performance is compared with the series dynamic braking resistor (SDBR). The WF is modeled with equivalent aggregated DFIG. The PSCAD/EMTDC simulation results show that the CDRFCL is an effective solution for enhancement of LVRT capability and limitation of fault current contribution (FCC) of WFs.

Comparison of Superconducting Fault Current Limiter and Dynamic Voltage Restorer for LVRT Improvement of High Penetration Microgrid

For a high penetration microgrid, improving its low-voltage ride-through (LVRT) capability under some minor or temporary faults can contribute to reinforcing power support and reducing network instability. In this paper, the comparison of a superconducting fault current limiter (SFCL) and a dynamic voltage restorer (DVR) for LVRT capability enhancement of a 10-kV microgrid is conducted. Concerning the microgrid which includes distributed photovoltaic generation, energy storage and loads, the effects of the SFCL and the DVR are compared in detail, and related theoretical analysis, simulation study, and economical evaluation are carried out. From the demonstrated results, the suggested two devices can both assist the microgrid to achieve the LVRT operation, but the economics of the DVR are weaker than the SFCL. Moreover, compared to the DVR, the SFCL enables the energy storage unit to offer better control effects in power stabilization. From technical and economic perspectives, the SFCL is a more preferable choice than the DVR.

Calculation of current limiting reactance of hybrid SFCL for low voltage ride-through capability enhancement in DFIG wind farms

This paper presents a new approach for the low voltage ride-through capability enhancement of doubly-fed induction generator (DFIG) wind farms using a hybrid superconducting fault current limiter (SFCL) of the first peak current limiting type, which has the advantage of a fast recovery time. A design for the hybrid SFCL, focusing on current limiting reactor (CLR) reactance calculation, is proposed in this paper to determine an appropriate value for the CLR reactance that satisfies the grid code requirements of the DFIG wind turbines. High-temperature superconductors (HTS) such as Bi-2212, YBCO, Bi-2223, Ti-2223, and Hg-1223 are investigated for use in the hybrid SFCL. The recovery time and first peak current reduction effectiveness are the criteria for selecting the HTS. In the proposed method, a during-fault voltage from the grid code requirement is used as an input parameter to compute the reactance of the CLR. Based on the results of the base-case simulations conducted on the DIgSILENT PowerFactory software, the Bi-2223 HTS with the first peak of fault current less than 4.5 kA and recovery time of 2.5 s is selected for adoption in the hybrid SFCL. The calculated results of the proposed method are compared with the simulation results of the hybrid SFCL, in terms of the DFIG wind turbine fault ride-through capability enhancement, to demonstrate that the performance of the proposed method satisfies the grid code requirements.

Power Quality Improvement and LVRT Capability Enhancement of Wind Farms by Means of an Inductive Filtering Method

Unlike the traditional method for power quality improvement and low-voltage ride through (LVRT) capability enhancement of wind farms, this paper proposes a new wind power integrated system by means of an inductive filtering method, especially if it contains a grid-connected transformer, a static synchronous compensator (STATCOM) and fully-tuned (FT) branches. First, the main circuit topology of the new wind power integrated system is presented. Then, the mathematical model is established to reveal the mechanism of harmonic suppression and the reactive compensation of the proposed wind power integrated system, and then the realization conditions of the inductive filtering method is obtained. Further, the control strategy of STATCOM is introduced. Based on the measured data for a real wind farm, the simulation studies are carried out to illustrate the performance of the proposed new wind power integrated system. The results indicate that the new system can not only enhance the LVRT capability of wind farms, but also prevent harmonic components flowing into the primary (grid) winding of the grid-connected transformer. Moreover, since the new method can compensate for reactive power in a wind farm, the power factor at the grid side can be improved effectively.

A low-voltage ride-through capability enhancement scheme of doubly fed induction generator based wind plant considering grid faults

This paper presents an improved low-voltage ride-through (LVRT) capability scheme of a grid connected doubly fed induction generator (DFIG) during any type of grid fault. In this context, an effective switching strategy based on computation of rotor current components has been suggested for the proposed passive protection circuits of a rotor side converter (RSC). Simultaneously, the RSC will control the fundamental rotor current within its available capacity for providing reactive power to the faulty grid. The proposed passive protection circuits comprise both stator and rotor side series resistor based passive compensators. The stator passive compensator will only be operated at starting and ending instant of fault to restrict rotor inrush current regardless of the type of fault. On the other hand, the rotor passive compensator is conditionally activated at the time of unbalanced fault to keep the overall rotor current under control. During both types of fault, RSC performs dual functions as partially scaled active compensator cum fractional reactive power generation controlling element. Thus, coordinated operation of passive compensator(s) and RSC will improve the LVRT ability of DFIG based wind power plants under any fault scenario. Various simulations are performed on 1.5 MW DFIG to show the advantage of this proposed control strategy.

Low Voltage Ride-through Capability Enhancement of Doubly Fed Induction Generator Based Wind Turbines under Voltage Dips

<span lang="EN-US">Based on the advantages of doubly fed induction generator (DFIG)-based wind turbine (WT). This paper proposes a new control strategy to improve the ride-through capability of DFIG-based WTs in the event of a grid fault. The proposed method is performed by using the DFIG converters control and the addition of the damping resistances connected to the DC circuit, to follow the requirements defined by the grid codes. The proposed ride-through solution limits the peak values of the DC link voltage, the rotor inrush current, electromagnetic torque and DFIG transient response at the times of occurrence and clearing the fault. The proposed solution is simulated and compared with the crowbar solution using MATLAB/Simulink environment.</span>