Cage Induction Generator Research Articles

Multiphase Wind Energy Conversion Systems Based on Matrix Converter

This paper presents a new variable speed wind energy conversion systems (WECS). It is based on a six-phase asymmetrical squirrel cage induction generator (SCIG) and a matrix converter (MC) as power electronic interface between six-phase SCIG and electrical network. The analysis employs a rotor flux vector control algorithm and a scalar strategy modulated MC to control the generator. Characteristics of MC are used for maximizing the power tracking control when different wind speeds and delivering powers to the grid are simultaneously considered. The MC provides sinusoidal input and output voltages and a unity power factor, but causes an asymmetry in the generator. A current control strategy including the method of suppressing imbalance caused by this asymmetry is discussed. Some numerical simulations are carried out showing the effectiveness of the proposed WECS topology.

Assessing the Effective Parameters on Operation Improvement of SCIG based Wind Farms Connected to Network

As the penetration level of wind energy in power system increases, stable operation of power system would get impacted by wind turbine's characteristics. The stability issue derived from this fact that the squirrel cage induction generators (SCIG) used in these turbines potentially would cause voltage drop and voltage stability problems in network, regarding to its reactive power absorption tendency. Thus, detection of effective parameters in increment and reduction of unstability occurrence probability could make SCIG based wind farm predictable and eventually cause improvement in voltage stability margin of whole of power system. In this paper, effective factors of wind farm operation connected to the network are assessed and studied in two sections. The first section includes parameters which depend upon substantive and functional characteristics of induction generator and could threat the stability of power system. The second section containing such parameters and characteristics of power system as which are able to affect the stable operation of SCIGs and can be lead to instability in whole of the power system. Eventually reactive power has been identified as more effective option in system designing. The studies are concentrated on voltage stability and small signal stability. In order to make the results more practical, the 660KW inductive generator which is widely used in Iran is studied in this paper.

Improved Low Voltage Ride through Capability of a Fixed Speed Wind Generator Using Dynamic Voltage Restorer

Wind energy is one of the fastest growing renewable energy technologies in world. The new grid code proposes that the wind turbine should remain connected to the grid during voltage disturbances. Three phase voltage sags and faults cause reduction in voltage at the point of interconnection to the grid when fixed speed wind turbines connected to squirrel cage induction generators are employed resulting in disconnection of wind turbine from the grid. Dynamic voltage restorer is a series connected custom power device used for voltage compensation during sags and swells. In this paper, the Low voltage ride through capability of a fixed speed wind turbine is improved using dynamic voltage restorer. Simulation studies are done to determine the transient stability of a fixed speed wind turbine with squirrel cage induction generator using Matlab Simulink.

Analysis of Voltage Drop due to Change in Induction Generator Output during Grid Connection

Recently, there has been an increasing application of squirrel cage induction generators to small hydro power plants due to their simple and rugged structure, low construction cost and easy of maintenance. Induction generators receive a large inrush current at the time of grid connection, which causes a drop in the system voltage. The remaining voltage must be high enough to ensure the starting current of the motor. Induction machines have been designed with a variety of rotor shapes with the aim of reducing the current. In this paper, we analyzed the effects of induction generator capacity in order to ensure that the voltage drop does not exceed the allowable range during connection to the grid connection system.

Islanding operation of hybrid microgrids with high integration of wind driven cage induction generators

This paper proposes two control strategies for the islanding operation of hybrid microgrid with a high penetration of wind driven cage induction generators. The control strategies combine approaches traditionally applied to self-excited cage induction generators with recent approaches for microgrid’s islanding operation. The proposed control strategies aim to facilitate the higher integration of cage induction generators in microgrids. The first strategy is based on direct frequency and reactive power control while the second one uses an artificial grid to regulate the voltage amplitude and frequency. The proposed schemes are tested in PSCAD/EMTDC using a real wind speed pattern measured at Hokkaido Island of Japan. Simulation results show the successful operation of both schemes. The implementation simplicity and cost-effectiveness of both schemes are explained as well.

MULTIVARIABLE ROBUST GRID CURRENTS CONTROL OF A SQUIRREL CAGE INDUCTION GENERATOR CONNECTED TO A WIND TURBINE

In this paper, a multivariable robust control strategy of a variable speed wind energy conversion system based on a squirrel cage induction generator (SCIG) is presented. Optimal speed control of the SCIG is achieved by a conventional PI controller combined with a Maximum Power Point Tracking (MPPT) strategy. The Indirect Field Oriented Control (IFOC) technique based on a simple Park (d-q) reference model is used to implement the proposed controller. Active and reactive power flow between the grid and the inverter is controlled via simultaneous H-infinity control of active and reactive currents of the grid and the DC link voltage. The switching technique of the inverter which is connected directly to the grid is controlled by a programmed PWM look-up table wave shaping. The robustness and performance of the proposed control scheme is evaluated on a comprehensive model of the wind energy conversion system using Matlab/Simulink.

Critical Clearing Time and Wind Power in Small Isolated Power Systems Considering Inertia Emulation

The stability and security of small and isolated power systems can be compromised when large amounts of wind power enter them. Wind power integration depends on such factors as power generation capacity, conventional generation technology or grid topology. Another issue that can be considered is critical clearing time (CCT). In this paper, wind power and CCT are studied in a small isolated power system. Two types of wind turbines are considered: a squirrel cage induction generator (SCIG) and a full converter. Moreover, the full converter wind turbine’s inertia emulation capability is considered, and its impact on CCT is discussed. Voltage is taken into account because of its importance in power systems of this kind. The study focuses on the small, isolated Lanzarote-Fuerteventura power system, which is expected to be in operation by 2020.

Modifying the aggregated wind farm model with a controller

A large wind farm can be simplified by the aggregated wind farm models for load flow, steady and transient stability studies. When a fault (such as a short circuit) happens in a large wind farm, some of wind turbines trip while others do not. This paper is to design a controller to modify the aggregated wind farm model in the case of one or more unit removed or added from the complete model. This is without stopping the simulation process during performing the steady state and transient analysis of the whole system. This controller can modulate the status of the wind turbines in the aggregated model in a given farm according to any change in this farm. By this controller, we save effort and time to change the status of wind turbines in the aggregated model. The proposed wind farm is composed of some smaller farms of permanent magnet synchronous generators (PMSGs) and others of squirrel cage induction generators (SCIGs).

Reduced converter topology for integrated wind and small‐hydro energy generation system

This study presents a robust and cost-effective microgrid topology for integrating two commonly available wind and small-hydro renewable energy sources. The proposed topology has two generators, one of them is self-excited squirrel cage induction generator driven by a small-hydro turbine and other one is permanent magnet brushless DC generator driven by a small-scale wind turbine. The proposed system is integrated using a voltage source converter and a boost converter which are maintaining voltage and frequency, mitigating power quality problems and performing mechanical sensorless maximum power point tracking, respectively. A battery bank is also used to balance the load and supply power mismatch and to ensure the supply for critical loads. The proposed control algorithm is tested and verified on a developed laboratory prototype of the system. Test results verify that voltage and frequency of the system are regulated and the power-quality-related issues are also resolved in this microgrid.

Transient Stability Analysis of Power System with Grid Integration of Wind Generation

Transient stability is one of the key issue in power system which to be explored further in the presence of wind generator integration into the power systems. Transients are occurring with sudden and severe disturbances like faults. Transient stability management is a great challenge in power system as transient leads to severe damage to the grid. This paper investigates the impact of Squirrel Cage Induction Generator (SCIG) and Doubly Fed Induction Generator (DFIG) on the power system transient stability of the two types of wind generators. SCIG is fixed speed and DFIG is variable speed wind generators. Fixed speed wind generators are more simple to operate and reliable but they are limited by the energy output of the wind turbine as far as stability issues are considered. Variable speed wind generators of similar rating can improve stability of the system. In the present paper sensitivity analysis, transient stability studies have been conducted on a modified IEEE 14 bus system. The simulations have been done in Power System Analysis Toolbox (PSAT), which is MATLAB compatible to evaluate power system and the results are presented.

English

This paper presents the design of Shunt Active power filter and simplified control of hybrid system (wind -hydel) system connected to two back-to-back converters in which one is connected to hydel turbine and the other is connected to wind turbine system through squirrel cage induction generators (SCIG) feeding three phase loads in isolated locations. The main objective of this work is to provide a better control algorithm for the VSC and to achieve maximum power tracking (M.P.T) through rotor speed control of the wind turbine driven S.C.I.G under varying speeds at the machine side and to control the magnitude and frequency of the voltage at load side and to eliminate the ripple content in the wave forms and to create the system balanced. The system also ensures in sending the power generate by SCIGw is complete to the load through the load- side converter and remaining power be store into ESBS. And at the identical time if the required active power of the load is more than the total power generated by SCIGw and SCIGh. Then the deficit power is supplied by the ESBS. Simulation models of the proposed hybrid system with SAPF and the simulation results are obtained in MATLAB using Simulink and Sim Power System set toolboxes, with different load condition at different wind conditions Keywords-small-hydel, squirrel-cage induction generator (SCIG), MPT, Voltage Source Converter (VSC.), Shunt Active Power Filter (SAPF).

Fault Ride-Through Capability of DSTATCOM for Distributed Wind Generation System

<span>In this paper, fault ride through analysis of a low voltage distribution system augmented with distributed wind generation using squirrel cage induction generator and distribution static compensator (DSTATCOM) is carried out through modeling and simulation study in MATLAB. The impact of different types of unbalanced (single line to ground) fault in a low voltage distribution system in normal and severe conditions are studied and analysed in details. Analysis on system instability is also shown in case of sever fault condition. A distribution Static Compensator (DSTATCOM) is used to improve fault ride through (FRT) capability of wind generation system by compensating positive sequence voltage. A comparison of dynamic response of the system with and without DSTATCOM and effects of DSTATCOM on voltage and generator speed are presented. The simulation results shows that DSTATCOM is capable of reducing the voltage dips and improving the voltage profiles by providing reactive power support to distributed wind generation system under balanced as well as unbalanced faults condition and enhances the fault ride through capability of the wind generator</span>

Dual stator winding variable speed asynchronous generator: optimal design and experiments

In the present paper is carried out a theoretical and experimental study of dual stator winding squirrel cage asynchronous generator (DSWA) behavior in the presence of saturation regime (non-sinusoidal) due to the variable speed operation. The main aims are the determination of the relations of calculating the equivalent parameters of the machine windings to optimal design using a Matlab code. Issue is limited to three phase range of double stator winding cage-induction generator of small sized powers, the most currently used in the small adjustable speed wind or hydro power plants. The tests were carried out using three-phase asynchronous generator having rated power of 6 [kVA].

Power Quality Improvement Using Custom Power Devices in Squirrel Cage Induction Generator Wind Farm to Weak-Grid Connection by using neuro-fuzzy control

<p>Wind farm is connected to the grid directly.The wind is not constant voltage fluctuations occur at point of common coupling (PCC) and WF terminal . To over come this problem a new compensation strategy is used . By using Custom power devices (UPQC).It injects reactive power at PCC . The advantages of UPQC is it consists of both DVR and D-STATCOM . DVR is connected in series to the line and it injects in phase voltage into the line .D-STATCOM is connected shunt to the line .The internal control strategy is based on management of active and reactive power in series and shunt converters of UPQC . The power exchainge is done by using DC-link</p>

Asymmetrical Fault Ride Through as Ancillary Service by Constant Power Loads in Grid-Connected Wind Farm

The introduction of distributed generation (DG) into low voltage (LV) systems demands that the generation system remain grid connected during voltage sags to ensure the operational stability. The DG consisting of fixed speed squirrel cage induction generator (SCIG)-based wind turbines is unable to provide reactive power control and needs a dedicated compensating device. Under asymmetrical grid faults the negative sequence flux circulation in the airgap introduces the torque oscillations that lead to the reduction of lifetime of the generation system. This paper proposes the use of distributed constant power loads (CPLs) for asymmetrical fault ride through (FRT) instead of using a centralized STATCOM. It has also been observed that the compensation of negative sequence voltage improves the performance of SCIG by eliminating the torque ripples. The compensation of positive sequence voltage avoids a possible voltage collapse at the LV distribution level and improves the reliability and stability of the wind farm. Centralized compensation of the asymmetrical grid fault by a STATCOM is compared with the distributed compensation by CPLs. The results suggest that each individual CPL injects lower current for maximum FRT enhancement compared to a dedicated STATCOM.

Modeling and Control of Standalone Direct-Driven PMSG WECS for Grid Compatibility at Varying Wind Speeds

Wind energy is one of the most available and exploitable forms of renewable energy. Variable speed PMSG based Wind Energy Conversion System (WECS) offers many advantages compared to the fixed speed squirrel cage induction generators such as improved stator output operation at better power factor, no maintenance cost for gear box (as it is direct-driven) reduction in weight and losses, higher efficiency and ability to run at low speeds. The elimination of the gear box and brushes can enhance the efficiency of wind turbine by 10%. In this paper a Permanent Magnet Synchronous Generator (PMSG) is modeled whose stator is connected to the constant single phase load (in place of grid) through AC/DC thyristors based rectifier followed by capacitor (dc-link) and DC/DC converter control. Overall arrangement provides constant output to connected load if applied with proper controlling techniques. Hence this proposed wind generation system design can be extended for grid connection also via DC/AC inverter control. Results are simulated and verified in MATLAB/Simulink platform at constant rated (12m/s) and varying (stepped) wind speed for smooth and constant output voltage. DOI: http://dx.doi.org/10.11591/telkomnika.v13i3.7097

Robust and Efficient Control of Wind Conversion System based on a Squirrel Cage Induction Generator (SCIG)

This paper presents a control strategy for a squirrel cage Induction generator (SCIG)based wind energy conversion system. Control strategies of the AC/DC converter 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 backstepping approach 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.

Experience in Developing a Single-Phase Two Winding 5 kW Self-excited Induction Generator for Off-Grid Renewable Energy Based Power Generation

This paper deals with the design and development of a novel single-phase two winding self-excited squirrel cage induction generator (SEIG) for off-grid renewable energy based power generation. The principles underlying the design process and experience with SPEED design tool are described to design a 5 kW, 50 Hz, 230 V, 4 pole single phase AC generator. All possible configurations to reduce harmonic components of induced e.m.f. are attempted for desired performance and to get an optimum design keeping in view the manufacturing constraints. The development of a prototype based on this design has been completed with the help of an industry. Typical test results on the prototype are presented to demonstrate its performance. Computed results are obtained with a design based computational procedure for performance analysis and a critical comparison is made with test results.

Nonlinear Control of Variable wind Speed Conversion System Based on a Squirrel Cage Induction Generator (SCIG)

This study presents a control strategy for a Squirrel Cage Induction Generator (SCIG)-based wind energy conversion system. Control strategies of the AC/DC/AC converter 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 backstepping approach 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 study.

Diagnosis of Wind Energy System Faults Part I : Modeling of the Squirrel Cage Induction Generator

Generating electrical power from wind energy is becoming increasingly important throughout the world. This fast development has attracted many researchers and electrical engineers to work on this field. The authors develop a dynamic model of the squirrel cage induction generator exists usually on wind energy systems, for the diagnosis of broken rotor bars defects from an approach of magnetically coupled multiple circuits. The generalized model is established on the base of mathematical recurrences. The winding function theory is used for determining the rotor resistances and the inductances in the case of n- broken bars. Simulation results, in Part. II of this paper, confirm the validity of the proposed model.