Cage Induction Generator Research Articles

Cascaded H-Bridge Inverter for Wind Driven Isolated Squirrel Cage Induction Generators

Abstract: This paper describes the simulation andharmonics analysis of cascaded five-level H-bridge invertersfed induction motor load drive for islanding mode applications.The self – excited induction generator (SEIG) fed H-bridgeMulti-Level Inverter (MLI) for wind energy conversionsystems is chosen for several islanding mode applications. Inthis paper, the SEIG (for standalone systems) fed cascaded fivelevel inverter for induction motor load applications are clearlyexplained with the help of MATLAB / SIMULINK models. Thegenerated voltage of the wind driven SEIG is mainly dependingon the wind velocity fluctuations and appropriate loadconditions. The five level cascaded inverters have interfacewith the wind driven SEIG. By choosing appropriate value ofModulation Index (MI), the variable voltage and variablefrequency of the generator can be finely controlled. Thesimulation and harmonic analysis of the proposed inverter willbe discussed, and the total harmonic distortion of statorcurrent for different modulation index at different switchingfrequencies are evaluated and the speed and torque ofinduction motor for different load torques are plotted.Index Terms: Self – Excited Induction Generator (SEIG),Variable speed Wind Turbine, Multi Level Inverter (MLI),Induction Motor (IM), Modulation Index (MI).

A Proposed Strategy for Power Management of a Standalone Wind Energy Conversion System with Storage Battery

Several strategies have been suggested to optimize power extracted from the Standalone Variable Speed Wind Energy Conversion System (SVSWECS) using a Squirrel Cage Induction Generator (SCIG). Where, many of them use the battery as a storage unit for future use. However, the latter is assumed as an ideal component and that no maximum charging or critical limit. With the considered strategy, the generated wind power can be managed using a fast and reliable fully rugged electrical control. Indeed, the use of reliable Power Management and Control (PMC) algorithm where the battery current is well controlled. However, this solution allows maintaining the system operation in two stable modes.The considered system consists of an SCIG connected mechanically to the wind turbine through a gearbox, and electrically through a PWM rectifier to the DC bus capacitor, the latter is connected to the load and the battery through a PWM inverter and buck-boost converter respectively. In this paper, to approach the system to reality, a new PMC is proposed using a purely reliable electrical control. The Direct Torque Control (DTC) is used. The latter is combined with the Maximum Power Point Tracking (MPPT) technique and the State Of Charge (SOC) of battery. The important key of the proposed control strategy are the SOC and the sign of the difference between the generated and the demanded powers. The obtained simulations results are assessed and carried out using MATLAB/Simulink package and show the effectiveness and the performance of the proposed algorithm.

SCIG Based Wind Energy Integrated Multiterminal MMC-HVDC Transmission Network

Modular multilevel converter (MMC) based HVDC system for renewable energy integration has attracted the researcher’s interest nowadays. This paper proposes a control strategy for MMC based multiterminal HVDC system for grid integration of squirrel cage induction generator (SCIG) based wind energy systems. Unlike the average model, this work models the MMC using the aggregate model and develops multiterminal HVDC transmission network in MATLAB/Simulink. It further develops the MMC multiterminal HVDC transmission network in real time digital simulator (RTDS). Instead of simplified current source, the proposed network considers the complete dynamics of SCIG based wind source from generation to integration. It employs field-oriented control for optimum wind energy tracking and forms isolated AC grids using feed forward controller. The proposed MMC controller performance has been tested under severe balanced and unbalanced disturbances. The results from aggregate model based MMC network in MATLAB/Simulink and those of the experimental MMC network in RTDS are in full agreement. The results confirm optimum wind energy tracking, fulfill grid code requirements, and improve low voltage ride through capability.

Hybrid Power System Frequency Control including Wind Farm using Battery Storage System

Fixed speed wind turbine-squirrel cage induction generator (FSWT-SCIG) based wind farm (WF) is increasing significantly. However, FSWT-SCIG have no frequency control capability, which creates a significant problem on power system steady-state stability. This paper represents a new operational strategy to control frequency of the entire power system including large-scale FSWT-SCIG based WF by using battery storage system (BSS). The proposed cascaded control of BSS is designed to provide effective amount of real power during steady-state period to damp frequency fluctuations. To evaluate the validity of the proposed system, simulation studies are executed on a reformed IEEE nine-bus power system with three synchronous generators (SGs) and SCIG-based WF along with BSS. The simulation results indicate that the proposed system can be an effective solution to reduce frequency fluctuations of the hybrid power system during steady-state condition.

Performance of three phase AI controller based UPQC to enhance power quality of hybrid RES

Day-by-day to reduce the greenhouse effects and increase the power generating capacity the dependency of renewable energy systems are increasing. Due to its uncertainty and continuously changing characteristics introducing power quality issues into the power system. The challenging task for electrical engineers is to produce quality of electrical power with less carbon emissions, especially in a weak grid systems. In this paper, built a new featured hybrid technological concept of renewable energy generating resources to reduce the greenhouse carbon emissions. For this, developed mathematical models of two renewable energy sources, proton exchange membrane fuel cell and wind energy system with a squirrel cage induction generator. To enhance the quality of power built a most promising custom power devise, an Artificial Neural Network controller based Unified Power Quality Conditioner. Further, presented performance of an Articial Neural Network Controller based unied power quality conditioner: to handle the voltage variations due to wind fluctuations, to enhance quality of power due to sags and swells.

Control Implementation of Squirrel Cage Induction Generator based Wind Energy Conversion System</p>

Trends towards PC-based computing platforms have given a path to innovate advanced, model-based control algorithms for the control of wind energy conversion systems. These advanced models allow us to gain increased reliability and improved efficiency. This work is focused on the digital signal processor based implementation aspects of a variable speed, grid connected; squirrel cage induction generator based wind energy conversion systems. Control design using a voltage source converter at the machine side have been described, designed, modeled and analyzed. A comprehensive analysis of the designed system is performed in terms of the active power harnessed, power quality and reactive power control. Optimal power point operation has been implemented so that highest available power is harnessed for varying wind velocities. A 2.2kW prototype with back to back connected voltage source converter has been implemented in hardware using TMS320F2812 digital signal processor. The experimental results illustrate the excellent performance of the system.

MGWO-PI controller for enhanced power flow compensation using unified power quality conditioner in wind turbine squirrel cage induction generator

Power quality is considered to be the major challenging one in the realization of the smart grid. So as to compensate for the issues occurring in power quality, active power filter (APFs) is mainly chosen as they are capable of filtering fast and has some active compensation. Also, load current related power quality constraint can be solved, such as unbalanced power, huge (Total harmonic distortion) THD level, and reduced power factor. For correcting the inappropriate supply of voltage and load current, the unified power quality conditioner (UPQC) and an effective integration of wind turbine are employed. A UPQC is a group of both shunt and series APF in a continuous manner having a conventional DC link capacitor. The voltage control of the DC link capacitor is significant in attaining a preferred performance on UPQC. In this paper, the UPQC with a Modified Grey Wolf Optimization (MGWO) based PI controller integrated with renewable energy like Wind turbine squirrel cage induction generator (SCIG) was implemented for the elimination of voltage and current harmonics imperfection precisely. Likewise, the Modified Grey Wolf Optimization (MGWO) was also exploited in UPQC. The performance analysis was made with UPQC, without UPQC, and with MGWO & UPQC and the simulation, outcomes are estimated and compared for the parameters THD values, load voltage and current. Also, the performance analysis was implemented in hardware prototype set-up and the results attained are depicted.

Modelling and analysis of distributed power generation schemes supplying unbalanced and non-linear load

This study presents a combined control strategy for stand-alone distributed power generation scheme, utilizing the squirrel cage induction generator (SCIG), and the permanent magnet synchronous generator (PMSG) in its structure. The combined control consists of both the machine side and load side converter control. The proposed load voltage controller, cascaded with the inner filter current controller, is designed for a load-side converter (LSC) to remove the harmonic component during non-linear loading and negative sequence component in case of unbalanced loading respectively. The control algorithm ensures to produce constant load voltage amplitude and frequency, with the change in both input power and non-linear and unbalanced loading scenarios. It also guarantees the sinusoidal load voltage under the mentioned loading conditions. Simultaneously, the dc-link voltage controller cascaded with the inner q-axis stator current controller is used for machine side converter (MSC) to keep the dc-link voltage at the prescribed level for both SCIG and PMSG during all the operating conditions. In this paper, an analysis of both the distributed generators based wind energy conversion systems under vector control for MSC provides the enhanced machine variable performance. The proposed control scheme is successfully implemented in MATLAB/Simulink environment. One scaled experimental prototype is developed, and real-time results are shown in the paper to validate the theoretical claims of the controllers.

Coordinated Control Scheme of Battery Storage System to Augment LVRT Capability of SCIG-Based Wind Turbines and Frequency Regulation of Hybrid Power System

Fixed speed wind turbine-squirrel cage induction generator (FSWT-SCIG)-based wind farms (WFs) are increasing significantly. However, FSWT-SCIGs have no low voltage ride-through (LVRT) and frequency control capabilities, which creates a significant problem on power system transient and steady-state stability. This paper presents a new operational strategy to control the voltage and frequency of the entire power system, including large-scale FSWT-SCIG-based WFs, by using a battery storage system (BSS). The proposed cascaded control of the BSS is designed to provide effective quantity of reactive power during transient periods, to augment LVRT capability and real power during steady-state periods in order to damp frequency fluctuations. The cascaded control technique is built on four proportional integral (PI) controllers. The droop control technique is also adopted to ensure frequency control capability. Practical grid code is taken to demonstrate the LVRT capability. To evaluate the validity of the proposed system, simulation studies are executed on a reformed IEEE nine-bus power system with three synchronous generators (SGs) and SCIG-based WF with BSS. Triple-line-to-ground (3LG) and real wind speed data are used to analyze the hybrid power grid’s transient and steady-state stability. The simulation results indicate that the proposed system can be an efficient solution to stabilize the power system both in transient and steady-state conditions.

Determination of Minimum Reactive Power Compensation for the Stable Operation of Type-1 WTG in Grid-Connected mode

The current energy demand scenario leads to tremendous increase in the renewable energy sector, but the integration of these renewable causes various stability issues of the system. Increasing share Wind energy has several shortages due to its energy harnessed from the wind. These shortages can be improved by compensating reactive power into the wind plant. The wind farm consist of fixed speed squirrel cage Induction generator absorbs reactive power from the grid for stable operation and it can be injected using reactive power compensator. In this context, the main aim of the research is to find the minimum reactive power compensation required for stable operation for different rating of Type-1 WTG in grid connected mode. In this paper, a detailed model of constant speed Squirrel Cage Induction Generator is carried out in MATLAB/SIMULINK-2017a to analyze the need of reactive power compensation to maintain voltage and frequency stability of the system during normal condition. The work also focuses on to investigate the impact of induction generator inertia level on compensation level. The modified IEEE 5-bus radial distribution system is used to conduct these investigations and the simulation results clearly show that: (1) The necessity and minimum additional reactive power support to the wind farm to improve and maintain stability of the system; (2) the inertia level of wind farm and reactive power compensator level both are independent each other.

A proposal for the improvement of electrical energy quality by energy storage in flywheels applied to synchronized grid generator systems

In its industrial application, three-phase induction motors are subject to the drive of high inertial loads. This fact results in the storage of kinetic energy during their operation. Thereby, this work presents a method to connect the electric grid of a Squirrel Cage Induction Generator rotor (SCIG) coupled to a cylindrical flywheel of high inertial content to reduce small disturbances in the electric grid. The proposal is validated by means of experimental tests on a bench using toroidal inductors to mitigate the effects of the current transients in the injection of kinetic energy converted into electrical energy in the grid. The results showed that this system can supply a short-time undervoltage disturbance of up to 0.2 pu three-phase and 0.4 pu per phase.

Capacitor Bank Sizing for Squirrel Cage Induction Generators Operating in Distributed Systems

The design of the capacitor bank to be placed with the squirrel cage induction generator, when operating with a direct connection to the distribution system, is performed from the value of the magnetization reactance of the machine. Based on the experimental procedures, the necessary reactive power is simulated according to the induction generator loading. Therefore, with the increase in generated active power, a larger portion of reactive is required. The simulation indicates the values of ideal capacitors. Thus, an analysis is made of which magnetization reactance factor is ideal for the capacitor bank design designated for the generator. The characteristic curve for capacitor bank sizing is related to the load torque loading depending on the active power generated. Thus, this work contributes to the analysis of the self-excitation curve of the three-phase induction generator that operates in parallel with the steady-state power distribution network. Obtaining the active power generated as a function of the absorbed reactive power required for induction generator magnetization can be found.

Power Optimization of wind energy conversion system using T-S Fuzzy approach

This paper presents a maximum power point tracking control for a wind energy conversion system (WECS) using a squirrel cage induction generator (SCIG) which supplies a DC load through AC/DC converter. The goal of the developed fuzzy control law is to track the reference signals corresponding to the maximum power generation that leads to an optimal operation of the induction generator. First, the dynamics behaviour of the WECS is represented by a Takagi-Sugeno (T-S) fuzzy model. Then, a H∞ observer-based fuzzy controller is proposed to achieve a maximum power point tracking even when we consider a varying wind speed profile. The controller and observer gains are calculated by solving linear matrix inequalities (LMIs). Finally, simulation results are presented to illustrate the effectiveness of the proposed approach.

Application of FVSI, Lmn and CPF Techniques for Proper Positioning of FACTS Devices and SCIG Wind Turbine Integrated to a Distributed Network for Voltage Stability Enhancement

Induction power generators are the most popular wind energy conversion systems (WECS) because they do not require synchronization units. However, they usually draw a huge quantity of reactive power during disturbances. Hence, incorporating wind power into power networks may cause voltage instability. This paper presents the usage of STATCOM and SSSC FACTS devices for voltage stability enhancement of a distribution network with a squirrel cage induction generator (SCIG) wind power turbine. The continuation power flow (CPF) approach is utilized as a tool to determine the most suitable position of SCIG in the system. Also, voltage stability indices (FVSI and Lmn) are employed to estimate the stability margin of the system by figuring the weakest transmission lines and buses in order to locate the appropriate position where the FACTS devices should be installed. A comparison of the suitability of the FACTS devices to restore system stability was evaluated under 3-phase fault conditions. The results illustrated that STATCOM behaves better than SSSC when the system is restoring from a fault. Simulations and voltage stability assessment were carried out on the IEEE 14 bus test scheme using the PSAT simulation software package.

Reduced Output Fluctuations of Hybrid System using SCIG by Fuzzy Logic Controller

In this paper, the Squirrel Cage Induction Generator(SCIG) with distinct controllers to deal with a hybrid wind hydro scheme is employed. In order to reduce the output power fluctuations in SCIG, including energy storage in the battery, a fuzzy logic controller is proposed. This controller smoothens the reactive power to the supplied load by the wind generator. The proposed controller has faster convergence compared with usual PI controller under the presence of parametric variations and uncertainties. From literature, the control scheme as many controllers operates on the Proportional Integral control, which is easy to enforce and performs well under linear conditions of load. But the proposed controller operates not only linear load but also under nonlinear load conditions. Simulation results show the robustness of the proposed controller in eliminating the harmonics, efficiency and minimizing peak oscillations of the output voltage when compared with the conventional controller.

Advanced Fault-tolerant Control Strategy of Wind Turbine Based on Squirrel Cage Induction Generator with Rotor Bar Defects

Several research works in Wind Energy Conversion Systems (WECS) based on Squirrel Cage Induction Generator (SCIG) are developed for isolated site applications. Where, WECS are usually controlled by the Maximum Power Point Trucking (MPPT) algorithm in order to extract the maximum power from wind with constant operating point of SCIG. However, this WECS based on SCIG generator suffers from the problem of breaking rotor bars, therefore a failure in rotor bars is particularly a challenging task because: 1) it can change the operating point generated by MPPT algorithm, 2) increase mechanical vibrations, 3) affect the operation of gearbox, 4) inject a harmonic current in the grid. Therefore, Fault Tolerant Control (FTC) scheme is necessary to allow an optimum energy production, to reduce the maintenance costs and to increase the WECS availability. In this work, a new fault diagnosis approach based on frequency analysis of stator currents is used to detect the failure in bars of SCIG, then FTC algorithm is developed to adjust the pitch angle in max wind speed zone by determining a new operating point according to the wind speed, which leads to extend the lifetime of WECS. Simulation results using MATLAB SIMULINK showed a nominal current in healthy rotor bars and the lifetime of WECS was increased.

A robust SMES control for enhancing stability of distribution systems fed from intermittent wind power generation

The voltage and frequency stability issues of power systems are the main challenges that arise from high penetration levels of wind energy systems. This paper presents an effective solution for voltage and frequency stability problems by using a superconducting magnetic energy storage (SMES) system controlled with a fuzzy logic controller (FLC). The proposed control system can suppress the voltage and frequency fluctuations due to the high variations of wind speed. In addition, the proposed control system is suitable for both balanced and unbalanced distribution systems with high penetration levels of wind turbines (WTs). A squirrel cage induction generator (SCIG) is selected in the case study, which represents the worst scenario of WT generation from the voltage and frequency stability aspects. This is due to the high reactive power consumed by the SCIG from the utility grid during steady state and voltage fluctuations that may lead to harmful consequences for power system components. The proposed control method is validated using the IEEE 33-bus radial distribution network (RDN), wherein the SMES and WT systems are connected to the weakest points of the RDN. The obtained results demonstrate the superior performance of the proposed FLC-SMES system for alleviating the voltage and frequency fluctuations of the distribution power system during high variations of wind power.

Squirrel cage induction generator to 140 bus weak distribution power grid connection using i-UPQC for voltage fluctuations

This paper develops an optimal power transmit strategy for 140 bus weak distribution power grid connecting squirrel cage induction generator (SCIG) and integrated unified power quality conditioner (i-UPQC). To meet technical standards and earn operational profits in electricity market can consequently increases the operational cost. As to decrease the operational cost basis, the optimal location of i-UPQC on 140 bus power system for voltage control can be determined. The integrated-proposed controller can modulate the predictions of weak power grid, maintenance cost, wind power and voltage fluctuations. The proposed model is validated using SCIG data for weak distribution power grid and i-UPQC capacity. Results address the effectiveness of the method and help to weak power grid to ensure optimal location and energy schedule. The results motivate weak power grid operators to adjust i-UPQC real and reactive output powers to overcome the power quality problem called weak power grid.

Combined control of stand-alone energy conversion scheme for distributed sources: Development and performance analysis

This paper has addressed the variable speed and constant frequency (VSCF) generation from the uncontrolled prime mover-based scheme for a stand-alone system. The small and medium scale wind energy conversion systems, usually dealing with this uncontrolled nature of prime movers, has been handled by the scheme, in this paper. The distributed generation unit (DGU) has considered a squirrel cage induction generator (SCIG) and a back to back converter in its structure. The DGU is developed with a load voltage control, including the filter elements, for the load side voltage source converter (LVSC) and a three-stage control for the generator side voltage source converter (GVSC). This combined controller for the DGU enables it to operate under both input and output side variations. Further, the controller is able to supply constant voltage at a constant frequency throughout the operation. The developed control is successfully implemented in the simulation environment, and the performance of the system is analyzed thoroughly. The variations, considered here are the d-axis component of load voltage, load impedance, dc- link voltage, and the prime mover speed. The performance of the control is verified experimentally with a prototype in reduced power scale in real-time. The results in both environments are found to be satisfactory.

Frequency and voltage control of microgrid with high WECS penetration during wind gusts using superconducting magnetic energy storage

The intermittent behavior of wind power generation results in a fast variation of both frequency and voltage magnitudes of isolated microgrids with high wind power penetration. In this paper, a hybrid energy microgrid with wind energy conversion system (WECS) and diesel synchronous generators are analyzed during wind gust conditions. Superconducting magnetic energy storage (SMES) is connected at the same node of the WECS to mitigate the intermittent wind power generation. A developed fuzzy logic controller has been applied to achieve active power sharing. The damping of voltage fluctuation depends on SMES reactive power, which is controlled by a voltage source converter. The studied microgrid comprises 33 nodes, two diesel SGs, and two WECSs of squirrel cage induction generator type at 30% penetration level. The results demonstrate the effectiveness of the proposed control strategy to mitigate the frequency fluctuations during the wind speed gusts by smoothing power output from WECSs/SMES system. Moreover, voltage control is achieved by injecting reactive power from the SMES system. All simulations are performed by MATLAB/Simulink package.