Squirrel Cage Induction Generator Research Articles

LCL Filter Design of STATCOM using Genetic Algorithm Scheme for SCIG Based Microgrid Operation

In a microgrid static Compensator (STATCOM) is the most prominent inverter circuit for stabilizing the bidirectional power flow requirements of the system. This inverter circuit is the primary source of harmonics when the supply current feeds from the microgrid to the main grid. Improved control strategy and proper filter design may give solution to these issues and so, there is a huge scope of research in the field of the converter control techniques and filter designing for such microgrid based power system. The key objectives of this paper are (i) to develop an adequate current control scheme for adjusting real and reactive power fluctuations produced by load time to time, and (ii) to reduce the harmonic level of output characteristics in terms of real and reactive power flow and current frequency. For this, an approach is presented to estimate the filter design parameters for current controlled STATCOM connected to squirrel cage induction generator (SCIG) based microgrid. A nature-inspired optimization namely, genetic algorithm (GA), is implemented to estimate the most suitable parameters for the LCL filter. Results obtained through GA are validated with a conventional mathematical method in terms of real and reactive power flow through microgrid along with harmonic-based studies.

Performing Wind System with Rectifier with Near Sinusoidal Input Current

The RNSIC-1 (rectifier with near sinusoidal input currents converter), is the foundation of a wind generator system that is presented. The three inductances that make up a traditional RNSIC–1 converter are eliminated in the proposed arrangement, and the SCIG generator's leakage inductances fill their place. This is what makes it new. The wind system's role in the load currents is discussed. Lower power losses, smaller harmonic input currents, fewer EMI issues, excellent dependability, and cheaper costs are characteristics of the new wind system. This new wind system could be used for partial variable speed wind turbines (usually 70% to 100% synchronous speed) and lower hydro connector squirrel cage induction generators (SCIG).

Analysis and design of wind energy system based on nonlinear speed controller

This paper presents a control fuzzy robuste strategy for a squirrel cage Induction generator (SCIG)-based wind energy conversion system. Control strategies is presented along with the mathematical modeling of the employed configuration. The maximum power point extraction of the wind turbine is addressed along with the proposed strategy. The approach method is introduced to control the generator speed and regulate the flux. The wind system is then simulated in Matlab-Simulink and the developed model is used to illustrate the behavior of the system. The simulation results are presented and discussed at the end of this paper.

An intelligent wind turbine with yaw mechanism using machine learning to reduce high-cost sensors quantity

In this paper, with the assistance of some tools and a machine learning model, a smart wind turbine was formed that eliminates some expensive sensors and reduces sensor complexity. Squirrel cage induction generator (SCIG) and six rotor blades make up the proposed design, and depending on the wind's direction, the turbine itself can rotate the rotor hub to produce energy more effectively. Additionally, two stepper motors are coupled to the yaw mechanism with the aid of the rotor hub, and the entire controlling procedure will depend on the direction of the wind. The rotor hub must continuously revolve in the same direction as the wind to maximize wind energy utilization. Additionally, to correctly predict wind degrees, a machine learning model was deployed. Random forest regression was used to train and predict the wind direction. The model is deployed in Raspberry Pi, where the incoming sensor values are being stored. Using the generated data, machine learning model was trained and it can be concluded that the model can potentially replace some of the expensive sensors to reduce cost. The model can be used for similar weather conditions only based on machine learning model and fewer sensors.

An adaptive control strategy for grid-forming of SCIG-based wind energy conversion systems

One of the crucial issues in the expansion of isolated wind energy conversion systems (WECSs) is the design of a grid forming control structure that is robust to changes of the system’s operating point in the steady-state as well as transient conditions. This paper has addressed the voltage/frequency control of a local microgrid as well as flux and slip control of a squirrel cage induction generator that feeds the microgrid via a back-to-back converter in an isolated WECS. An adaptive nonlinear voltage control structure has been proposed for load side converter (LSC) consists of a constant frequency voltage regulator and a current controller based on the Lyapunov function method (LFM), which are connected in cascade. In an outer loop, the reference current of LSC is generated by the voltage regulator designated for maintaining the voltage/frequency of the microgrid. In an inner loop, the reference signals are robustly tracked by the current controller. In a novel reference frame that its angle difference with the stationary reference frame is determined by a dual loop DC link voltage controller, an LFM-based nonlinear flux controller is proposed for the machine side converter (MSC). Using the proposed flux control structure, in addition to maintaining the flux magnitude at a nominal value, by controlling the generator slip through adjusting the speed of the proposed reference frame, the power balance is established and the DC voltage is maintained at a pre-set value. The performance of the proposed controllers has been investigated through simulation in the MATLAB® software. The obtained results confirm the robustness and stability of the proposed control structure with respect to various disturbances and uncertainties.

Dynamic analysis of grid-connected hybrid wind farm

Since the last couple of years, the expansion of grid-connected wind farms (WFs) has increased dramatically. The wind turbine might be a fixed-speed squirrel cage induction generator (FSWT-SCIG) or a variable speed wind turbine with a doubly-fed induction generator (VSWT-DFIG). The main disadvantage of FSWT-SCIG is its lack of ability to adjust power quality. Inversely, the VSWT-DFIG is a competitive wind turbine technology that allows for the effective management of both active and reactive power outputs. Moreover, it has some extraordinary functionaries rather than FSWTSCIG. However, the major downside to this system is that it only has a partial rating AC/DC/AC power converter, which is extremely expensive. Hence, to reduce the overall cost combining the implementation of VSWT-DFIG and FSWT-SCIG in a WF could be a feasible alternative. Therefore, a novel DFIG control technique is proposed in this article, which can keep the connection point voltage of the hybrid WF stable during dynamic analysis. To evaluate the proposed controller responses PSCAD/EMTDC software has been used.

TCSC Application for Transient Stabilization of Wind Turbine with Fixed Speed Induction Generator

Wind turbines (WTs) are a desirable alternative to traditional nonrenewable power resources as a result of recent environmental concerns. Some of them are fixed speed wind generator (FSWG) and have been integrated to power system by squirrel cage induction generator (SCIG). Induction machine absorbs reactive power during all operating conditions, especially at fault condition may result in severe voltage drop which can lead to generator outage. This outage disconnects a significant amount of active power and consequently leads to frequency instability. In order to prevent induction generator (IG) outages in short circuit failures, this paper investigates thyristor-controlled series capacitor (TCSC) device as a candidate solution. TCSC compensates the IG terminal voltage drop by adjusting transmission line impedance at fault condition. In the proposed method, a metaheuristic technique means that shuffled frog leaping algorithm (SFLA) has been utilized to optimize the TCSC controller gains. The proposed scheme can be applied for both SCIGs and wound rotor induction generators (WRIGs) which is another advantage of this method. Single-machine infinite bus system is considered as case study, and various operating conditions and disturbances have been considered to verify the effectiveness of the proposed method.

Comparative Study of Grid Frequency Stability Using Flywheel-Based Variable-Speed Drive and Energy Capacitor System

Recently, there has been a rise in the integration of renewable energy sources into power grids. As a result of this, there is a need to carry out new studies in order to understand the dynamics of power grids during disturbances that is mainly caused by the stochastic nature of wind energy. The operation of modern power grids that are tied to wind farms follows a stipulated grid requirement or grid codes, considering the allowable threshold frequency variation during grid dynamics. This paper presents a comparative study of two frequency control schemes considering grid frequency stability using two frequency control topologies. A novel dynamic flywheel scheme with a doubly fed induction generator (DFIG) variable-speed wind turbine with the coordinated control of excess kinetic energy and mechanical torque during operation was the first scheme, and a control strategy of an energy capacitor system (ECS) with a squirrel cage induction generator fixed-speed wind turbine (FSWT) was the second scheme. The salient part of this study was that the DFIG maximum point power tracking for effective smoothing of the output of the wind generator in the first scheme was designed based on the control strategy of its reference power to achieve smoothing of the wind power at the terminals of the wind generator. The model system employed in this work was a wind farm that is tied to a conventional power grid made of steam and hydro synchronous turbines. For an effective and fair comparison of results, the same natural wind speed was used in PSCAD/EMTDC for both schemes. When no control, Scheme 1, and Scheme 2 were implemented, the frequency dips were 47.20, 49.99, and 49.99 Hz with overshoots of 50.500, 50.005, and 50.001 Hz and recovery times of over 600.00, 0.01, 0.01 s, respectively, for the frequency variable.

Improvement of power system stability in wind connected generator by using PSAT

Voltage stability in power systems is a major problem that receives international attention. An open and free source piece of software, Power System Analysis Toolbox (PSAT) is used in this study to create a model of modified IEEE 14 bus system. Models of two recently created wind turbines—the Squirrel Cage Induction Generator (SCIG) and Doubly Fed Induction Generator (DFIG)—are connected to a modified IEEE 14 bus system. The stability of the power system is examined in this work in relation to the effects of Squirrel Cage Induction Generator (SCIG) and Doubly Fed Induction Generators (DFIG). Here, both DFIG and SCIG, which have variable speeds, are regarded as wind generators. In this work, a small signal stability investigation using SCIG and DFIG wind turbine systems was carried out on a modified IEEE 14 bus system. The results of their simulation were analysed.

Impact of DC link brake chopper design on the LVRT behavior of full-scale converter wind turbines

Wind turbines (WTs) are loaded by the wind and by the electrical grid. A low voltage ride through (LVRT) is a special load case for WTs, which can be critical for their drivetrain. They are usually less severe for WTs with a full-scale converter (FSC); however, in some cases there are still loads observable in the mechanical drivetrains of WTs with FSCs. Different aspects like the brake chopper design, the control and specifications of the grid side converter (GSC) as well as the grid and fault parameters affect these loads. In this paper, three different LVRT behaviors of a WT with a squirrel-cage induction generator (SCIG) and a FSC were investigated via simulations. In the worst case, a sharp peak in the electromagnetic torque of the generator after fault clearance is possible. The cause lies in the GSC control, especially the phase-locked loop (PLL), and can also be influenced by adjusting the control parameters, brake chopper and filter design. The resulting mechanical drivetrain torque, on the other hand, is increased by only 2.9% for a very short time. Thus, the loading of the mechanical drivetrain components is only slightly increased. Therefore, the risk of damage to the mechanical components of the FSC WT due to grid faults is relatively low.

Hybrid Wind-Solar Power System with a Battery-Assisted Quasi-Z-Source Inverter: Optimal Power Generation by Deploying Minimum Sensors

This paper presents a hybrid renewable energy system (RES) including wind and photovoltaic (PV) power sources. The wind energy subsystem (WES) consists of a squirrel-cage induction generator (SCIG) driven by a variable-speed wind turbine (WT) and corresponding power electronic converter, by means of which a speed-sensorless indirect-rotor-field-oriented control of the SCIG is implemented. The outputs of both the WES and PV power source rated 1.5 kW and 3.5 kW, respectively, are connected to the DC bus, with the quasi-Z-source inverter (qZSI) acting as an interlinking converter between the DC bus and the AC grid/load. An advanced pulse-width-modulation scheme is applied to reduce the qZSI switching losses. The considered RES can operate both in grid-tie and island operation, whereas the battery storage system—integrated within the qZSI impedance network—enables more efficient energy management. The proposed control scheme includes successively executed algorithms for the optimization of the WES and PV power outputs under varying atmospheric conditions. A perturb-and-observe PV optimization algorithm is executed first due to the significantly faster dynamics and higher-rated power of the PV source compared to the WES. The WES optimization algorithm includes two distinct fuzzy logic optimizations: one for extraction of the maximum wind power and the other for minimization of the SCIG losses. To reduce the number of the required sensors, all three MPPT algorithms utilize the same input variable—the qZSI’s input power—thus increasing the system’s reliability and reducing the cost of implementation. The performance of the proposed hybrid RES was experimentally evaluated over wide ranges of simulated atmospheric conditions in both the island and grid-tie operation.

Fault Analysis of a Small PV/Wind Farm Hybrid System Connected to the Grid

The dynamic modeling, control, and simulation of renewable energy sources connected to the electrical grid are investigated in this study. Photovoltaic (PV) systems and wind systems connected to the power grid via the point of common connection (PCC) were the only two systems included in our study. Simulation and control methodologies are provided. For both PV arrays, the method of extracting maximum power point tracking (MPPT) is utilized to obtain the highest power under standard test conditions (STC: 1000 W/m2, 25 °C). A power electronics converter that can transform DC voltage into three-phase AC voltage is required to connect a PV system to the grid. Insulated gate bipolar transistors (IGBTs) are utilized in a three-level voltage source converter (VSC). The distribution network is connected to this three-phase VSC by way of a step-up transformer and filter. During synchronous rotation in the d−q reference frame, the suggested control for the three-level solar power system that is connected to the grid is constructed. To obtain a power factor as near to one as possible, the phase-locked loop (PLL) is employed to align the angle of the power grid voltage with the angle of the current coming from the inverter. Squirrel-cage induction generators (SCIGs), which are utilized as fixed speed generators and are linked directly to the power network, are the foundation of the wind system. Additionally, a pitch angle control approach is suggested to keep the wind turbine’s rotor speed stable. MATLAB/Simulink software is utilized to model and simulate the suggested hybrid system. Under fault scenarios such as the line to line to line to ground fault (LLLG fault), the suggested hybrid system’s dynamic performance is examined. The simulation results prove the ability to manage the small hybrid system that combines solar and wind power, as well as its dynamic performance.

Load Voltage Control of a Wind Turbine-driven Three-phase Squirrel-Cage Induction Generator in an Islanded Microgrid

The intermittent nature of the wind resources and reactive power consumptions are major issues associated with squirrel cage induction generator wind power system when operated in an island microgrid mode. The resultant effect of these two issues are continuous fluctuations of load voltage which has adverse effects on electrical devices. This paper proposes a voltage regulation technique based on proportional controller and phase deposition sine pulse width modulation (PDSPWM) for the control of 5-level neutral point clamped multilevel inverter. The instantaneous voltage tracking strategy based on root mean square value of microgrid voltage was adopted to regulate and maintain the output load voltage at 400 𝑉𝑟𝑚𝑠 despite rotor fluctuations with wind speeds. The simulation was carried out in a MATLAB/SIMULINK environment and the performance of the control scheme was found to be excellent.

A grid forming control for wind energy conversion systems

This paper presents an effective and practical structure to improve voltage and frequency regulation in grid-forming control of self-excited induction generator-based wind energy conversion systems. In the proposed control structure, in addition to a fixed parallel excitation capacitor, a small wound rotor synchronous generator is also used as a reactive power compensator. The excitation voltage of the small synchronous generator is controlled in such a way that by injecting the required amount of reactive power, this generator maintains the balance between the inductive and the capacitive reactive powers in the isolated system, and thus, improves the system voltage regulation. In addition, an active power control is proposed in which the speed of the prime mover of the self-excited squirrel cage induction generator is adjusted in such a way that the active power of the small synchronous generator is maintained at zero value. The proposed power controller, by creating the balance between the generated and the consumed active powers, improves the frequency regulation of the wind energy conversion system. The validity and effectiveness of the proposed structure are demonstrated through both simulation studies and experimental implementation. The obtained results confirm that the poor regulation of voltage and frequency, which is one of the major drawbacks of self-excited induction generator-based wind energy conversion systems, has been significantly mitigated by using the proposed method.

Comprehensive Analysis of PV and Wind Energy Integration into MMC-HVDC Transmission Network

Renewable energy will play a vital role in greenhouse gas emissions reduction. However, renewable energy is located far away from the load center. Modular multilevel converter-(MMC) based VSC-HVDC systems became competitive for remotely located renewable energy grid integration. Unlike the average model for MMC and renewable energy side converter, this paper presents a detailed model-based control and analysis of the MMC-HVDC system for solar and wind energy integration. Furthermore, it optimally tracks PV energy employing the modified incremental conductance method and wind energy using field-oriented control. Instead of decoupled control, a feedforward controller is utilized to establish a standalone AC voltage for renewable energy grid integration. This work considers a doubly fed induction generator (DFIG), permanent magnet synchronous generator (PMSG), and squirrel cage induction generator (SCIG) for wind energy integration. The results from MATLAB/SIMULINK platform agree with the controller hardware in the loop results from RTDS-dSPACE platform. The results confirmed the optimum solar and wind energy tracking during wind speed, irradiance, and temperature variations. However, it improved the fault ride-through capability during balanced and unbalanced low voltage disturbances at the point of common coupling (PCC) of AC grid.

Sensorless Control of Variable-Speed SCIG Wind Energy Conversion Systems Based on Rotor Flux Estimation Using ROGI-FLL

In this article, a novel sensorless control method for variable-speed squirrel-cage induction generator (SCIG) wind power systems with simple rotor flux estimation is proposed. The rotor flux linkages are estimated using a reduced-order generalized integrator (ROGI)-frequency-locked loop (FLL), which regards the rotor back electromotive forces (EMFs) found from the generator model as its inputs. Based on these rotor flux linkages, the rotor flux angle can be estimated through direct trigonometric relations. Then, to avoid the speed estimation error caused by the FLL under stator frequency variations, the synchronous speed is estimated from the aforementioned rotor flux angle via the derivative. Owing to the excellent harmonic rejection capability of the ROGI, the proposed rotor flux estimation is robust against measured high-frequency ripple components. The analysis of ROGI response in the presence of dc offset in the rotor back EMFs is provided as well, and it shows that the proposed method is not faced with the saturation under those conditions. Performance comparisons between the proposed method and the existing dual second-order generalized integrator (SOGI)-FLL-based method have been conducted via both simulations and experiments, thereby verifying the feasibility of the proposed method.

Alpha Harris Hawks Optimization based Overcurrent Relay Coordination with Hybrid Time-Current-Voltage Characteristics Considering the Grid-Connected Distributed Generation

The conventional protection schemes may lead towards the inadvertent operation of the protection devices with the increased penetration of renewable energy sources based distributed generation (RES-DG) in distribution networks (DN). The miscoordination and the malfunctioning of directional overcurrent relays (DOCR) may occur due to significant change in the fault current level (FCL) and the change in the network topology form the radial to ring topology caused by the RES-DG. Optimization algorithms (OA) and modification in relay characteristics were mostly used to tackle the DOCR miscoordination problem. However, in this paper, a fast and an accurate protection coordination scheme is proposed to eliminate the DOCR miscoordination and to reduce the overall operation time of DOCRs by employing an advance optimization algorithm along with an innovative modification in the relay characteristics. In the first step, time-current characteristics (TCC) of the conventional DOCR are modified to a hybrid time-current-voltage (TCV) characteristics by including the effect of the fault voltage in the relay characteristics equation. Thereafter, the performance of conventional Harris Hawk’s optimization (HHO) is enhanced with an improvement in the exploration strength of the HHO by an adaptive mutation-selection of the alpha hawks during each iteration named as alpha-HHO (α-HHO). The protection coordination problem is formulated as a non-linear constrained optimization problem. The proposed protection scheme is evaluated on the IEEE-8 bus meshed DN. The standard IEEE-8 bus test system is modified by integrating multiple squirrel cage induction generators and PV-based RES-DGs at optimal bus locations. Detailed numerical studies are carried out with the help of simulations to show the performance of the proposed scheme. The results are compared with the existing protection schemes reported in recent literature. The investigation results show that the highest reduction in overall relay operating time with zero mis-coordination is achieved with the proposed scheme.

Development of improved sparrow search-based PI controller for power quality enhancement using UPQC integrated with medical devices

Photovoltaic (PV) panel interfaces with the grid create the issues regarding power quality such as voltage distortion, voltage harmonics, etc. To mitigate the harmonics in PV systems, Active Power Filters (APF) are taken. Unified Power Quality Conditioner (UPQC) is utilized for alleviating the problems correlated with voltage dip/swell in source voltage that has regulated the load voltage absolutely. On the other hand, the existing researches do not solve the power quality problems such as Voltage Stability Index (VSI), UPQC cost and power loss. Power quality is taken as the main demanding one in the analyzing the smart grid. Thus, APFs are primarily selected for compensating the problems occurring in power quality as they has some active compensation and are competent of filtering fast. Moreover, power quality constraint with load current must be addressed, which considers the factors like reduced power factor, huge Total Harmonic Distortion (THD) level, and unbalanced power. To reach the ideal efficiency on UPQC, the voltage control of the DC link capacitor is important. Thus, a new power quality enhancement model with UPQC especially for medical devices is focused. The UPQC-connected medical devices are suggested with a new Adaptively Updating-Sparrow Search Algorithm (AU-SSA)-based Proportional plus Integral (PI) controller, which is integrated with renewable energy like wind turbine Squirrel Cage Induction Generator (SCIG) to eliminate the current and harmonics imperfection accurately. This model implements a new power quality enhancement model by formulating a newly derived objective function. Finally, the experimental verification of the proposed scheme is done.

A Comprehensive Modeling for Wind Turbine Generator and DSTATCOM into Backward/Forward Load Flow Algorithm

Backward/forward load flow algorithm is commonly used in the power system, particularly in radial distribution networks. However, the rapid development in the power electronics technologies makes power systems more flexible with the integration of Renewable Energy Resources (RESs) and compensation devices. Consequently, this paper presents simple models for wind turbine generators based on Squirrel Cage Induction Generator (SCIG) and Distribution Static Synchronous Compensator (DSTATCOM) into a backward/forward load flow algorithm. In the wind generator model, the mechanical powers are collected from the manufactures data where the electrical power is calculated through the SCIG equivalent circuit and injected as negative loads at the connected buses. The second model in this paper is the DSTATCOM devices which are utilized to recover the SCIG reactive power. In the proposed model, the connected DSTATCOM bus is converted to a voltage-controlled bus (PV-bus type) with zero active power. Moreover, the reactive power of the DSTATCOM is updated during the iterative process until the load flow convergence. The simplified models for both wind generators and DSTATCOM are validated based on standard IEEE 33-bus and 85-bus radial distribution systems. The obtained results show the feasibility and effectiveness of the proposed models.

A variable wind harvesting based induction generator using variable voltage and variable frequency converter for renewable energy applications

ABSTRACT This paper proposes the design and development of a power electronic converter intended for induction generator (IG) to harvest the power generated from variable wind in a wind energy conversion system (WECS). The squirrel cage induction generator (SCIG) is anticipated for fairly fixed speed operation, while its speed should be super-synchronous with respect to the synchronous speeds corresponding to the frequency of the receiving alternating current bus bar. In the existing WECS, SCIG requires a minimum wind velocity below which generation is not possible. The novelty of the proposed method is that the range of wind velocities can be selected over which generation is possible. To achieve this, the proposed system makes use of a variable voltage and variable frequency converter (VVVFC). Depending upon the wind velocity, the frequency of the VVVFC is adjusted such that the speed of the turbine and hence the IG are virtually maintained at super synchronous speeds with respect to the frequency of the AC side of the VVVFC. In addition, the perturb and observe-based maximum power point tracking (MPPT) scheme is also implemented. The proposed methodology also includes a series compensated buck–boost converter (SCBBC) inserted between the battery and the direct current link of the final inverter that feeds an RL load. Simulation in the MATLAB Simulink environment is carried out, and an experimental prototype has also been developed to validate the proposed method. Based on the results, it is found that the proposed variable speed system with the integration of VVVFC, SCBBC, and MPPT harvests is 78% greater than the conventional fixed speed system.