New split-winding doubly salient permanent magnet motor drive

A new split-winding doubly salient permanent magnet (DSPM) motor drive is proposed. This DSPM motor drive offers the advantages of high power density, high efficiency, and wide speed range. The corresponding operation, analysis, implementation, and experimentation are successively presented. Finally, experimental results are used to confirm that the proposed DSPM motor drive offers high efficiency over a wide output power range, exhibits good dynamic performance, and extends the constant-power operation range significantly.published_or_final_versio

Converter fault diagnosis and post-fault operation of a doubly-fed induction generator for a wind turbine

Wind energy has become one of the most important alternative energy resources because of the global warming crisis. Wind turbines are often erected off-shore because of favourable wind conditions, requiring lower towers than on-shore. The doubly-fed induction generator is one of the most widely used generators with wind turbines. In such a wind turbine the power converters are less robust than the generator and other mechanical parts. If any switch failure occurs in the converters, the wind turbine may be seriously damaged and have to stop. Therefore, converter health monitoring and fault diagnosis are important to improve system reliability. Moreover, to avoid shutting down the wind turbine, converter fault diagnosis may permit a change in control strategy and/or reconfigure the power converters to permit post-fault operation. This research focuses on switch fault diagnosis and post-fault operation for the converters of the doubly-fed induction generator. The effects of an open-switch fault and a short-circuit switch fault are analysed. Several existing open-switch fault diagnosis methods are examined but are found to be unsuitable for the doubly-fed induction generator. The causes of false alarms with these methods are investigated. A proposed diagnosis method, with false alarm suppression, has the fault detection capability equivalent to the best of the existing methods, but improves system reliability. After any open-switch fault is detected, reconfiguration to a four-switch topology is activated to avoid shutting down the system. Short-circuit switch faults are also investigated. Possible methods to deal with this fault are discussed and demonstrated in simulation. Operating the doubly-fed induction generator as a squirrel cage generator with aerodynamic power control of turbine blades is suggested if this fault occurs in the machine-side converter, while constant dc voltage control is suitable for a short-circuit switch fault in the grid-side converter.Wind energy has become one of the most important alternative energy resources because of the global warming crisis. Wind turbines are often erected off-shore because of favourable wind conditions, requiring lower towers than on-shore. The doubly-fed induction generator is one of the most widely used generators with wind turbines. In such a wind turbine the power converters are less robust than the generator and other mechanical parts. If any switch failure occurs in the converters, the wind turbine may be seriously damaged and have to stop. Therefore, converter health monitoring and fault diagnosis are important to improve system reliability. Moreover, to avoid shutting down the wind turbine, converter fault diagnosis may permit a change in control strategy and/or reconfigure the power converters to permit post-fault operation. This research focuses on switch fault diagnosis and post-fault operation for the converters of the doubly-fed induction generator. The effects of an open-switch fault and a short-circuit switch fault are analysed. Several existing open-switch fault diagnosis methods are examined but are found to be unsuitable for the doubly-fed induction generator. The causes of false alarms with these methods are investigated. A proposed diagnosis method, with false alarm suppression, has the fault detection capability equivalent to the best of the existing methods, but improves system reliability. After any open-switch fault is detected, reconfiguration to a four-switch topology is activated to avoid shutting down the system. Short-circuit switch faults are also investigated. Possible methods to deal with this fault are discussed and demonstrated in simulation. Operating the doubly-fed induction generator as a squirrel cage generator with aerodynamic power control of turbine blades is suggested if this fault occurs in the machine-side converter, while constant dc voltage control is suitable for a short-circuit switch fault in the grid-side converter

Grid side converter control of dfig and mitigation of voltage sag

Now days wind power energy is playing a major role in power industry. With the increase in application of wind power variety of new topologies are coming into picture. Among the different form of variable speed fixed frequency topologies DFIG is most popular form due to its efficiency and ability to allow wide range of speed variation at reduced converter size. Doubly Fed Induction Generator (DFIG) is basically a wound rotor induction generator which is used to fed power from both stator and rotor circuit. Stator feeds power directly to grid which is unidirectional. Rotor circuit is connected to a bidirectional ac/dc/ac converter having a common dc link bus. In rotor, power flow is bidirectional i.e. depending on the mode of operation the power flow is either from rotor side to grid or it may be from grid side to rotor. The rotor side converter also fed reactive power to DFIG so as it can run at a near unity power factor. The function of the grid voltage converter is to maintain the DC link voltage constant, which ultimately fed a constant amplitude ac voltage to rotor side for maintaining the flux constant. But when grid voltage variation occurs, the dc link voltage also varies, ultimately rotor input voltage varies. This causes abnormal input of reactive power to rotor circuit. So to maintain the reactive power demand of machine, it draw reactive power from grid, which may lead to a condition of voltage fluctuation at PCC. One solution to this problem may be compensation of grid voltage variation before grid converter circuit. This compensation of voltage sag is done by a custom power device, known as Dynamic Voltage Restorer (DVR). The current Topic discusses about the application of DVR to DFIG to compensate voltage sag of grid so that the voltage of DC link will remain constant

Modelling and Control Design of Pitch-Controlled Variable Speed Wind Turbines

This chapter provides an overall perspective of modern wind power systems, including a discussion of major wind turbine concepts and technologies. More specifically, of the various wind turbine designs, pitch-controlled variable speed wind turbines controlled by means of power electronic converters have been considered. Among them, direct-in-line wind turbines with full-scale power converter and using direct-driven permanent magnet synchronous generators have increasingly drawn more interests to wind turbine manufactures due to its advantages over the other variable-speed wind turbines. Based on this issue, major operating characteristics of these devices are thoroughly analyzed and a three-phase grid-connected wind turbine system, incorporating a maximum power point tracker for dynamic active power generation is presented. Moreover, a simplified state-space averaged mathematical model of the wind turbine system is provided. An efficient power conditioning system of the selected wind turbine design and a new three-level control scheme by using concepts of instantaneous power in the synchronous-rotating d-q reference frame in order to simultaneously and independently control active and reactive power flow in the distribution network level are proposed. Dynamic system simulation studies in the MATLAB/Simulink environment is used in order to demonstrate the effectiveness of the proposed multi-level control approaches in d-q coordinates and the full detailed models presented. The fast response of power electronic devices and the enhanced performance of the proposed control techniques allow taking full advantage of the wind turbine generator.Fil: Molina, Marcelo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Mercado, Pedro Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentin

Wind as a Renewable Source of Energy

This report describes about he wind power and its potential that can be harnessed in the future to meet the current energy demand. With detailed description of the wind turbine and the wind generator focus has been given on the interconnection of the generators with the grid and the problems associated with it. The use of power electronics inn the circuitry and their applications have also been emphasized. In the end a voltage stability analysis has been done with respect to various models of the wind turbines to find the best way to clear faults and have optimum output

Comparison of low voltage ride through capabilities of synchronous generator with STATCOM and DFIG based wind farms

Includes bibliography.Increase in wind generation and grid-integration of wind energy technologies has resulted from an increasing demand of cheap and clean electricity across the globe. Wind generators are available as small, medium and large scale electric generators, usually in the range of 1kW to 100MW and are usually installed in areas rich in wind resource which may or may not be located close to the load centres. Wind energy penetration has increased since the 1970s with the total worldwide capacity of installed wind power reaching about 282,275 MW. Apart from technical issues of grid-integration, research is also being done to investigate the participation of wind energy systems to enhance grid performance through fault ride-through capabilities, providing voltage control and power quality improvement etc. The goal of a Fault Ride Through (FRT) or Low Voltage Ride Through (LVRT) system is to enable a wind farm (WF) to withstand a severe voltage dip at the connection point and still stay connected to the power system as long as the fault persists. Wind turbine designs are required to incorporate LVRT capability as per Grid Code’s requirements only if they are technically needed for a reliable and secure power system operation. The basic requirement for LVRT is that the wind turbines must maximise their reactive power injections to the network without exceeding the turbine limits. The maximisation of reactive current must continue for at least 150msafter the fault clearance or until the grid voltage is recovered within the normal operation range. It is important here to discuss here the immediate impact of the voltage dip on the wind farm (WF) operation. During the voltage dip caused by the fault, the active power provided to the grid by the WF is instantaneously reduced. This power becomes at least temporarily lower than the mechanical power available at the rotor hence the rotor speed of the wind generator increases. It is required for the LVRT capability of the WF, that the wind generators of the WF must not disconnect from the grid during fault persistence, either due to over-speeding or under voltage protections. After the clearing of the fault that led to the voltage dip, the voltage at the wind turbine bus would increase. It is also required that the wind generators should resume their power supply to the network without losing stability

The impact of wind generators on a Powe system's transient stability

This thesis discusses the investigations carried out on the different types of wind generators and how these would affect the transient stability of a hypothetical power network as presented in this report. Focus was on the transient responses of the conventional synchronous generator’s rotor angle and terminal voltage when connected to different types of wind generators. The three different wind generator technologies explored were the squirrel cage induction generator (SCIG), doubly-fed induction generator (DFIG) and the converter driven synchronous generator (CDSG)

Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine

Optimal performance of the electric machine/drive system is mandatory to improve the energy consumption and reliability. To achieve this goal, mathematical models of the electric machine/drive system are necessary. Hence, this motivated the editors to instigate the Special Issue “Mathematical Approaches to Modeling, Optimally Designing, and Controlling Electric Machine”, aiming to collect novel publications that push the state-of-the art towards optimal performance for the electric machine/drive system. Seventeen papers have been published in this Special Issue. The published papers focus on several aspects of the electric machine/drive system with respect to the mathematical modelling. Novel optimization methods, control approaches, and comparative analysis for electric drive system based on various electric machines were discussed in the published papers