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The operation of the induction machine as a generator is widely employed by generation systems based on wind power, hydropower, biomass and biofuels. However, the machine takes its excitation from external source of reactive power, which can mean that the induction generator is an inherently low power factor machine. This paper investigates a 2.2-kW three-phase induction machine designed to operate...
This paper investigates the effect of Series Dynamic Breaking Resistor (SDBR) sizing on a Doubly Fed Induction Generator (DFIG) based wind power conversion system. The boundary of the SDBR value is firstly derived by taking into account the controllability of the rotor side converter and the maximum allowable voltage of the stator. Then the impact of the SDBR value on the rotor current, stator voltage,...
Improved fault diagnostic techniques in wind turbines is a field of growing interest, given the negative impact that unexpected breakdowns have on the profitability of wind farms. New diagnostic techniques based on generator currents monitoring have recently been developed, but their use is still irrelevant despite the advantages that current monitoring presents versus monitoring vibrations. In part,...
Electric power systems are commonly interconnected for cost effiective robust delivery purposes. Transmission interconnection benefits from load diversity, variety of sources and fuel prices. In addition; nation-level grid interconnection offers increased reliability, reduction of power interruption and generation-cost minimization. Various techniques are applicable for grid interconnection like High...
A doubly-fed induction generator connected to a weak grid is presented. The grid is characterized by unbalanced voltage conditions, which introduces a negative sequence voltage to the stator windings. The negative sequence voltage conditions generate pulsations in the torque and power quantities of the generator, which affects its stability. Proportional plus resonant controllers are introduced into...
Wind turbine with proportion of its design and control concept, can produce electricity in different actual mode. This enables turbine to show a certain reaction in different faults. This operation, can be analyze and provide a suitable plan for construct, and also add to turbine control mechanism as necessity. The main goal of this paper is analyzing the stability of a fixed-speed wind turbine during...
The paper is concerned with the wind energy conversion system (WECS) applying doubly fed induction generator. It addresses the question whether the slip-torque characteristic of the generator belonging to short circuited rotor can be shifted along the slip axis only by the rotor voltage in the slip range ±0.3 resulting in more-less similar set of slip-torque characteristics as can be achieved with...
Dual stator winding induction generators (DSWIG) can provide controlled excitation and hence offer a brushless alternative to traditional synchronous machines or doubly fed induction machines (where a 2nd supply is injected to the rotor through a converter-inverter systems). These generators are a potential candidate for extraction of power from renewable energy resources such as wind, micro-hydro...
This paper shows new induction generation system for wind power generation. This system has the voltage source converter excited induction generator and the PFC converter to transfer the real power. Simulation and experimental results certifies that the dc/dc chopper control of the PFC converter can minimize the voltage source converter current, which only supplies exciting current for the induction...
Doubly fed induction generators using static frequency converters provide the possibility to have adjustable speed pump storage units where the active power can be controlled quickly for both generation (energy discharge) and pumping (energy storage) operation. However, high magnitude voltage spikes with high repetition rate and fast rise times (associated with PWM voltage of the converter) applied...
This paper analyzes nonlinear dynamics and stability in a network of fixed-speed induction generators. A typical example of the network appears in windfarms that have recently attracted a lot of interest as an alternative renewable energy resource with large capacity. In this paper, we derive a mathematical model representing nonlinear dynamics occurring in the induction generator network and then...
A micro-grid consisting of a 300kW wind turbine and a 40kW photovoltaic array is investigated under extreme operating gust (EOG) wind scenarios. The micro-grid is connected to the 380-V utility through a utility-side converter using natural-frame control, which provides a constant voltage of the DC link between the micro-grid and utility. The impact of the extreme gust wind variations on the micro-grid...
Based on Lyapunov stability theory, a holistic analysis approach is proposed for self-excited induction generator under no-load in the stationary reference frame with the transient mathematic model. Through analysis for initial transient states, a sufficient condition is fixed to be the limit cycle. The analytic formulas of the stator frequency, critical excitation capacitance and critical rotor speed...
The doubly fed induction generators (DFIGs) are used in almost 50% of the offshore and onshore wind power plants. The DFIGs offer advantages compared to fix speed induction generators. The DFIGs are sensitive to grid voltage disturbances and require additional protection for the rotor side power electronic converter, like crowbar protection. In the present paper two active crowbar topologies are compared,...
In this paper, an attempt has been made to predict the performance of grid connected induction generator (GCIG) due to different nature of grid faults. MATLAB/Simulink model for the power network as developed along with three phase induction machine model is used to observe the effects of faults on the transient performance of SCIG. Simulation result as obtained are found to be useful to predict the...
This paper compares two methods for rotor flux estimation of sensorless vector controlled squirrel-cage induction machine used in wind power applications. The compared methods are based on the integration of stator back electromotive force (back-emf) which is obtained from the machine parameters and measured voltages and currents. Rotor flux estimation based on the integration of back-emf leads to...
When the blade of the windmill crosses with the tower in wind power generation system, the wind pressure that blows against the blade becomes weak and the rotor speed decreases. The method using stator-flux-oriented vector control to prevent the effect of the tower shadow for the wind generator system with a wound rotor induction generator is proposed in this paper. The response to changes in active...
In this paper modelling and analysis of self excited dual stator winding induction generator (DSWIG) with a new method ‘fzero algorithm’ has been done. We develop the steady-state model of a dual three self-excited induction generator for stand-alone renewable generation dispenses with the segregating real and imaginary components of the complex impedance of the induction generator. Steady state performances...
This paper discusses the steady-state analysis and performance of self-excited induction generators (SEIG) driven by regulated and unregulated turbines. For constant-speed operation, a simple technique is used for the determination of the electrical frequency. Where for SEIG driven by an unregulated turbine, The turbine characteristics and the SEIG speed-torque characteristics are experimentally verified...
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