Variable Frequency Transformers for Increased Wind Penetration

Abstract: This paper aims to explore the possibility of synchronous generator (SG) based wind energy generation system feeding an isolated load using a latest power transmission technology i.e. variable frequency transformer (VFT). The proposed configuration does not employ any power electronics based interface as in conventional SG based stand-alone wind energy conversion systems (SWECS). For analysis, the simulation models of proposed configuration as well as conventional configuration have been developed under MATLAB-Simulink environment. A series of studies on power fed from the SG to the different loads at various SG input speeds has been carried out with the developed models. Further to analyze the effectiveness of the proposed method; the efficiency, total harmonic distortion (THD) of output voltage and THD of output current of the proposed method have been compared with those of the conventional method. From obtained results, it is observed that the proposed method is simple and does not produce harmonics. Moreover to validate the proposed scheme, an experimental analysis has been carried out. Further, the cost analysis of both systems has also been carried out. From the cost analysis, it is observed that the proposed system is cheaper than the conventional system.

Abstract: Conventional grid connected synchronous generator (SG) based wind energy generation system (WEGS) incorporates sophisticated power electronic control system in it which produces harmonics and this deteriorates the quality of output power. Hence, this paper presents a new method for grid integration of SG based WEGS using variable frequency transformer (VFT). The proposed method does not employ any power electronic based interface for grid integration of SG based WEGS and hence does not produce harmonics. Moreover, control of the proposed method is simple. In order to realize the proposed scheme, a digital simulation model of the proposed method has been developed under MATLAB/ Simulink environment. The power flow from the SG to the grid using the model has been studied and its results have been discussed.

Abstract: The Variable Frequency Transformer (VFT) is basically a controllable, bidirectional transmission device that can transfer power in-between asynchronous power system networks. The construction of VFT is similar to conventional asynchronous machines, where the two separate electrical networks are connected to the stator winding and the rotor winding, respectively. One power system is connected with the rotor side of the VFT and another power system is connected with the stator side of the VFT. The electrical power is exchanged between the two networks by magnetic coupling through the air gap of the VFT and both are electrically isolated. This paper gives an overview about core components, commissioning, mechanical design, model, operation, analysis and applications of VFT.

Abstract: As environmental concerns have focussed attention on the generation of electricity from clean and renewable sources, wind energy has become the world's fastest growing energy source. The authors dr ...

Abstract: This paper proposes the utilization of water storage ability to improve wind park operational economic gains and to attenuate the active power output variations due to the intermittence of the wind-energy resource. An hourly-discretized optimization algorithm is proposed to identify the optimum daily operational strategy to be followed by the wind turbines and the hydro generation pumping equipments, provided that a wind-power forecasting is available. The stochastic characteristics of the wind power are exploited in the approach developed in order to identify an envelope of recommended operational conditions. Three operational conditions were analyzed and the obtained results are presented and discussed.

Abstract: The paper discusses the implications of the increasing capacity of synchronous generators at the remote ends of rural distribution networks where the line resistances are high and the X/R ratios are low. Local voltage variation is specifically examined and two methods of compensation are proposed. The first of them is a deterministic system that uses a set of rules to switch intelligently between voltage and power factor control modes, while the second is based on a fuzzy inference system that adjusts the reference setting of the automatic power factor controller in response to the terminal voltage. Extensive simulations have verified that the proposed approaches may increase the export of real power while maintaining voltage within the statutory limits.

Abstract: Power electronics and exotic energy storage devices are making wind power steady enough to compete with conventional electricity sources. Systems based on advanced power electronics and energy storage devices are massaging and managing power flows from wind turbines, enabling them to contribute to electricity grids without putting those grids at risk. Not only are the technologies making wind power more palatable to grid operators, they are even making it possible for engineers to finally harness wind energy's tremendous potential in wind-swept, remote locales. This article discusses the power electronic and energy storage technologies used in wind power.

Abstract: Sustainability of the future energy supply based on renewable resources is a long-term strategic objective in view of limited fossil resources and avoidance of emissions and toxic waste. Of the various resources, available now or in future, wind is presently considered in Europe to hold most promise in the next few decades for contributing a sizable part of the electrical energy; generating electricity from wind is state of the art and feeding large amounts of wind power to the electrical grid is believed by many to be unproblematic. With recent data from one of the four control areas in Germany it is discussed how a sustainable energy supply based on off-shore wind power and pumped storage, called a "wind and water"-model, might look. It turns out that such an energy scheme, while feasible in principle, would require an immense storage capacity which would be impossible to realize. Thermal generation continues to be needed, based on various energy carriers, among them biomass according to availability