Low Voltage Ride-through Ability Research Articles

Finite-Control-Set Model Predictive Control for Low-Voltage-Ride-Through Enhancement of PMSG Based Wind Energy Grid Connection Systems

Grid faults are found to be one of the major issues in renewable energy systems, particularly in wind energy conversion systems (WECS) connected to the grid via back-to-back (BTB) converters. Under such faulty grid conditions, the system requires an effective regulation of the active (P) and reactive (Q) power to accomplish low voltage ride through (LVRT) operation in accordance with the grid codes. In this paper, an improved finite-control-set model predictive control (FCS-MPC) scheme is proposed for a PMSG based WECS to achieve LVRT ability under symmetrical and asymmetrical grid faults, including mitigation of DC-link voltage fluctuation. With proposed predictive control, optimized switching states for cost function minimization with weighing factor (WF) selection guidelines are established for robust BTB converter control and reduced cross-coupling amid P and Q during transient conditions. Besides, grid voltage support is provided by grid side inverter control to inject reactive power during voltage dips. The effectiveness of the FCS-MPC method is compared with the conventional proportional-integral (PI) controller in case of symmetrical and asymmetrical grid faults. The simulation and experimental results endorse the superiority of the developed FCS-MPC scheme to diminish the fault effect quickly with lower overshoot and better damping performance than the traditional controller.

Power Quality and Low Voltage Ride Through Capability Enhancement in Wind Energy System Using Unified Power Quality Conditioner (UPQC)

The various approaches used to improve the Low Voltage Ride Through (LVRT) capabilities of DFIG-based wind turbine systems are investigated in this study (WT). The Type-III WT machine, which is primarily based on DFIG, is connected to the grid without a digital power interface, resulting in unmanageable terminal voltage or reactive electricity output. As a consequence, novel LVRT approaches based on the deployment of additional active interface technologies were given in this work. The problem of low voltage faults is now being addressed using a variety of approaches. By analyzing LVRT approaches for DFIG-based WECS, this research attempts to discover such working ways by bridging the gap in terms of overall adaptive performance, operative complexity of controllers, and cost-effectiveness. This study suggests ways to improve LVRT's ability to rely on the relationship arrangement in three major areas based on their grid integrations. The wind turbine system is connected to a DVR, STATCOM, and UPQC in this study for active and reactive power regulation throughout the fault detection procedure. Using UPQC with SRF theory offers improved reaction during faults to increase active power and maximum compensation in reactive power with synchronous reference frame and without synchronous reference frame operation presented in this paper.

Study of stability after low voltage ride-through caused by phase-locked loop of grid-side converter

In a power system with a high percentage of converter coupled generation, dynamic characteristics of the converter affects the stability of the whole power system. The interaction of the various control loops of the grid-side converter, e.g., the phase-locked loop and the DC link voltage control loop, dominates the various dynamic characteristics of the grid-side converter, including its low voltage ride-through ability. In this paper, the phase-locked loop is modeled and analyzed and a stability criterion for the converter, depending on the grid impedance, is obtained. According to this criterion, a common low voltage ride-through test device based on the shunt impedance voltage sag generator is analyzed. The results show that, and explain why, the test device cannot reproduce the characteristics of the practical grid, which is also verified by experiments using a controller-Hardware-in-the-loop system.

Optimal Transient Search Algorithm-Based PI Controllers for Enhancing Low Voltage Ride-Through Ability of Grid-Linked PMSG-Based Wind Turbine

This paper depicts a new attempt to apply a novel transient search optimization (TSO) algorithm to optimally design the proportional-integral (PI) controllers. Optimal PI controllers are utilized in all converters of a grid-linked permanent magnet synchronous generator (PMSG) powered by a variable-speed wind turbine. The converters of such wind energy systems contain a generator-side converter (GSC) and a grid-side inverter (GSI). Both of these converters are optimally controlled by the proposed TSO-based PI controllers using a vector control scheme. The GSC is responsible for regulating the maximum power point, the reactive generator power, and the generator currents. In addition, the GSI is essentially controlled to control the point of common coupling (PCC) voltage, DC link voltage, and the grid currents. The TSO is applied to minimize the fitness function, which has the sum of these variables’ squared error. The optimization problem’s constraints include the range of the proportional and integral gains of the PI controllers. All the simulation studies, including the TSO code, are implemented using PSCAD software. This represents a salient and new contribution of this study, where the TSO is coded using Fortran language within PSCAD software. The TSO-PI control scheme’s effectiveness is compared with that achieved by using a recent grey wolf optimization (GWO) algorithm–PI control scheme. The validity of the proposed TSO–PI controllers is tested under several network disturbances, such as subjecting the system to balanced and unbalanced faults. With the optimal TSO–PI controller, the low voltage ride-through ability of the grid-linked PMSG can be further improved.

Enhancement of low voltage ride-through ability of the photovoltaic array aided by the MPPT algorithm connected with wind turbine

PurposeBy means of the massive environmental and financial reimbursements, wind turbine (WT) has turned out to be a satisfactory substitute for the production of electricity by nuclear or fossil power plants. Numerous research studies are nowadays concerning the scheme to develop the performance of the WT into a doubly fed induction generator-low voltage ride-through (DFIG-LVRT) system, with utmost gain and flexibility. To overcome the nonlinear characteristics of WT, a photovoltaic (PV) array is included along with the WT to enhance the system’s performance.Design/methodology/approachThis paper intends to simulate the control system (CS) for the DFIG-LVRT system with PV array operated by the MPPT algorithm and the WT that plays a major role in the simulation of controllers to rectify the error signals. This paper implements a novel method called self-adaptive whale with fuzzified error (SWFE) design to simulate the optimized CS. In addition, it distinguishes the SWFE-based LVRT system with standard LVRT system and the system with minimum and maximum constant gain.FindingsThrough the performance analysis, the value of gain with respect to the number of iterations, it was noted that at 20th iteration, the implemented method was 45.23% better than genetic algorithm (GA), 50% better than particle swarm optimization (PSO), 2.3% better than ant bee colony (ABC) and 28.5% better than gray wolf optimization (GWO) techniques. The investigational analysis has authenticated that the implemented SWFE-dependent CS was effectual for DFIG-LVRT, when distinguished with the aforementioned techniques.Originality/valueThis paper presents a technique for simulating the CS for DFIG-LVRT system using the SWFE algorithm. This is the first work that utilizes SWFE-based optimization for simulating the CS for the DFIG-LVRT system with PV array and WT.

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.

A robust control scheme for grid-connected photovoltaic converters with low-voltage ride-through ability without phase-locked loop

A robust control scheme with low-voltage ride-through ability is presented for grid-connected photovoltaic converters that operate under harsh conditions such as voltage sags and unknown disturbances and parameters. The proposed strategy allows for flexible active and reactive power injection into the grid during asymmetrical voltage sags without using a phase-locked loop or positive and negative sequence components. In addition, the same controllers are used under both normal operation and voltage sags, thus, lowering the control system’s complexity. The scheme is conceived by combining uncertainty-and-disturbance-estimation compensation and repetitive control for the dc voltage and phase currents, respectively. Controller design is carried out systematically and closed-loop stability is proven through Lyapunov’s analysis. Several simulation case studies are presented using the SimPowerSystemsTM toolbox of MATLAB/Simulink computing environment to demonstrate the performance of the proposed control system under voltage sags, unknown disturbances, abrupt changes in operating conditions, and parametric uncertainties.

A PLL-free robust control scheme with application to grid-connected fuel cell DGs under balanced and unbalanced conditions

A robust control scheme for the power electronic converter interface of grid-connected fuel cell distributed generators is presented. The scheme enables them to operate under various limiting factors that can severely affect performance such as voltage sags, parametric uncertainties, unknown disturbances and noise. The control strategy adds low voltage ride-through ability to the grid-connected system without requiring a specialized phase locked loop that is often an integral part of the control systems used under unbalanced grid conditions, and therefore, simplifying its design and lowering its computational complexity. The dc-dc and dc-ac converters are controlled using two different controllers: the uncertainty and disturbance estimation controller for the dc-side voltage, and the repetitive controller for the grid-side currents. The control system is designed with the objectives of robustness, fast transient response, disturbance rejection and low voltage ride-through ability. A number of simulation case studies are presented using the SimPowerSystems™ toolbox of MATLAB/Simulink computing environment to highlight the performance of the proposed control scheme under both symmetrical and asymmetrical voltage sags,parametric uncertainties, and abrupt operating condition changes. The control system is also tested through digital implementation on a low-cost microcontroller to validate its performance.

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.

Fault current limiter‐battery energy storage system for the doubly‐fed induction generator: analysis and experimental verification

Weak low voltage ride-through (LVRT) ability and unstable output power are two major problems faced by the doubly-fed induction generator (DFIG). To solve these two problems simultaneously, a commercially available fault current limiter-battery energy storage system (FCL–BESS), which is suitable to be applied in a microgrid, is proposed in this study. During normal operation, the FCL–BESS stabilises the output power of DFIG by compensating the fluctuating component of DFIG output power with energy buffering capability provided by the battery energy storage system (BESS). On occurrence of a grid fault, the FCL–BESS enhances the LVRT ability of DFIG by inserting the fault current limiting inductor into the stator, which weakens the rotor back electromagnetic force voltage and limits the rotor overcurrent. The FCL–BESS also stabilises the DC-link voltage by the BESS, which further strengthens the controllability of grid-side converter and rotor-side converter. Moreover, the FCL–BESS is able to help grid voltage recover fast and smoothly by providing power support to the grid. Experiments under different conditions have been carried out with a 2 kW prototype to evaluate the performance of the proposed FCL–BESS. Experimental results show that the FCL–BESS have much better performance than using single fault current limiter or BESS and can solve the two problems faced by the DFIG simultaneously and effectively.

Control Strategy of Three-Phase Photovoltaic Inverter under Low-Voltage Ride-Through Condition

The new energy promoting community has recently witnessed a surge of developments in photovoltaic power generation technologies. To fulfill the grid code requirement of photovoltaic inverter under low-voltage ride-through (LVRT) condition, by utilizing the asymmetry feature of grid voltage, this paper aims to control both restraining negative sequence current and reactive power fluctuation on grid side to maintain balanced output of inverter. Two mathematical inverter models of grid-connected inverter containing LCL grid-side filter under both symmetrical and asymmetric grid are proposed. PR controller method is put forward based on inverter model under asymmetric grid. To ensure the stable operation of the inverter, grid voltage feedforward method is introduced to restrain current shock at the moment of voltage drop. Stable grid-connected operation and LVRT ability at grid drop have been achieved via a combination of rapid positive and negative sequence component extraction of accurate grid voltage synchronizing signals. Simulation and experimental results have verified the superior effectiveness of our proposed control strategy.

The Study of Energy Storage Technology Application in Wind Power Integration

The classification and application range of energy storage technology are briefly introduced. Challenges for large-scale wind power integration are summarized. With regard to the problems in system stability, low voltage ride-through ability of wind the turbine generator, and power quality, the paper elaborated some solutions based on energy storage technology, and analyzed their advantages and disadvantages. With the character of energy storage technology combined, the paper put forward some advice of energy storage technology applying in wind power integration.

Improve the LVRT Ability of Wind Farm with DFIG by Combination of SVC and DVR

According to the demand of low voltage ride through (LVRT) in China, the operation features of DFIG during grid fault are analyzed. A new topology combining SVC with a novel DVR is put forward in this paper. The problems such as slow voltage recovery in early time of the grid fault and over compensation of voltage in the later time of the fault are overcome. The over current in rotor side of DFIG during the grid fault is restricted at the same time. The simulation model for the new topology is built in MATLAB/Simulink. The effectiveness of the topology in improving the ability of LVRT is verified.

Grid-connected photovoltaic system based on switched-inductor quasi-Z-source inverter and its low voltage ride-through control strategy

Compared with traditional Z-source and quasi-Z-source inverter, switched-inductor quasi-Z-source has higher booster multiple, lower capacitance stress, and higher conversion efficiency. Therefore, it is very suitable for grid-connected photovoltaic power generation system. This paper analyzes the voltage boosting theory of the switched-inductor quasi-Z-source inverter which is applied to grid-connected photovoltaic power generation system. For the imbalanced power grid voltage sag situation, this paper puts forward a low voltage ride-through (LVRT) control strategy. System realizes the unity power factor running and has a good LVRT ability under imbalanced power grid voltage sag. At last, the simulation and experimental results are shown to verify the correctness of the control method.

The Influence of Rotor Arrester on Low Voltage Ride through Behavior of Doubly-Fed Induction Generator

Low voltage ride through (LVRT) behavior is one of the key indices of wind turbine grid-integration evaluation. The key electric components of wind turbine, such as converter, control system had been researched. While other components of wind turbine, such as the rotor arrester, are also non-ignorable. Firstly, overvoltage of rotor during the LVRT is analyzed and one failure test has been presented because of rotor arrester performance. Finally, the rotor arrester has impact not only on the LVRT ability of wind turbine, but also damage to other hardware by on-site testing.

Research of STATCOM Impact on Wind Farm LVRT and Protection

Because of the wind turbine which possesses low voltage ride through (LVRT) capability can keep on working during the system fault, greatly reduce the adverse effects of power grid and ensure the relay protection reliability. However, the asynchronous wind turbine which widely used in home and abroad doesn’t have enough LVRT capability. So this paper proposes a method to enhance the LVRT capability of fixed speed induction generator (FSIG) based on wind farm using static synchronous compensator (STATCOM). And this paper establishes the simulation model of asynchronous wind generator wind farm and STATCOM in Matlab/Simulink software; the research results show that the STATCOM device can improve asynchronous wind farm LVRT capability. Then analysis the asynchronous wind generator which possess LVRT ability characteristics and the time of the action protection relations．According to the current wind farm system protection configuration, studying the asynchronous wind farm which with STATCOM device effect on protection configuration of system and the existing problems. At last, putting forward some reasonable measures of improving LVRT cooperate with relay protection characteristics and minimizing probability of wind power units take off the grid． DOI: http://dx.doi.org/10.11591/telkomnika.v10i8.1650 Full Text: PDF

Overview on Key Technologies of Grid-Connected Wind Power Based on Energy Storage

In order to promote the development of wind power and accelerate the efficient use of new energy sources, countries have brought energy storage systems into grid-connected wind farms to achieve efficient and stable operation of the wind power plant. This paper recounts the latest development status and trend of wind power at home and abroad, and introduces the principle of power conversion between energy storage system and wind farm. Based on the existing research results, it analyses power system stability related to wind power, low voltage ride-through ability of wind turbine, wind power penetration limit, as well as power quality issues. It also describes the new ideas about how to use energy storage technologies to solve the problems faced by the wind power.

Symmetrical Short Circuit Current Characteristics of Doubly Fed Induction Generator Wind Turbine with Crowbar Protection

Doubly fed induction generator (DFIG) is now becoming one of most widely used wind turbines in global market for wind power generation, due to its outstanding advantages. However, the DFIG is sensitive to grid faults. The DFIG will have to be removed from the grid if there’s no protection appliance in it. Therefore, the crowbar protection is widely used in the world for improving the low voltage ride-through ability of wind turbines. This paper analysed the operating characteristics and short-circuit current of DFIG under symmetrical short-circuit fault with respect to different sags to grid voltage, which on the basis of DFIG wind turbine with crowbar protection. And the expressions of short-circuit current under symmetrical short-circuit fault for DFIG were derived. The effectiveness of the expression was simulated in PSCAD/EMTDC.