An electric brake for wind turbine systems is proposed in this paper. Effective emergency electrical braking is needed if an overvoltage occurs due to grid failure. The derived circuits use high power thyristors corresponding to the high values of generated power from today's wind turbines. A practical confirmation with BLDC a generator is ongoing in the laboratory. The principle of operation is proved by the carried out simulations

The paper presents design considerations and a loss analysis of dc chokes in kW range, realized by different magnetic materials. Five designs under the same input parameters are realized with three different materials: ferrite (3F3), powder (sendust MS) and amorphous material (Microlite 245). An optimal design procedure is considered aimed at minimizing losses and volume of the component. A set of operating and construction parameters is analyzed. The obtained design results are verified by carried out simulations. Three of the compared DC chokes are realized, experimented and measured under the real operating conditions. The comparison of the three different materials is summarized and design recommendations are formulated regarding their use is such applications

-The current paper proposes an automated design approach for a previously developed passive converter circuits for wind turbine generators. This suggested approach allows to calculate the components for all passive converter circuits approved in European patent number PCT/EP2010/055637, where only minor changes in the source code of the mathematical and simulation software have to be made when different circuits are involved. An optimisation based on steepest descent method results in power/frequency (power/speed) curve that matches well the cubic dependence (P wtmax~ω 3 ) of the extracted power.Keywords -Converter circuit, Simulation, Wind energy.I. INTRODUCTION It is a valid fact that wind turbines are most efficient in variable speed mode [1][2][3][4]. The first electrical conversion AC/DC from the three phase generator has key role in the energy extraction. An active or passive rectifier will determine the type of electrical control that is used in the system. Usually the use of single three phase uncontrolled full wave rectifiers (passive) is limited to low power applications. An advantage is the lack of complicated control unit which significantly reduces the design time and the final price. Disadvantage is the poor electrical efficiency compared with the fully controlled thyristor or transistor rectifiers or so-called active.A novel design for passive converter circuit ( fig. 2.) improves the overall efficiency. The circuit includes the following components: two 3-phase full bridge uncontrolled rectifiers build with diodes D1÷D12, external inductors L ext1 ÷L ext3 and a simplified model of the permanent magnet synchronous generator consisting of voltage source V1÷V3 and inductor L gen1 ÷L gen3 for every single phase. The modeling of a power/frequency curve of a wind turbine with PMSG and passive converter is done by specifically developed methodology. It includes parametrical optimization of the values of L ext and L gen . As a result the power/frequency curve should match the well-known cubic dependence P wtmax ~ ω 3 [5].

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The article presents a comparison of advantages and disadvantages of a battery charger circuit with and without the use of DC-link capacitors in it. The specific application requirements, namely ultra-light electric vehicles, are set as lightness, efficiency and robustness of the design. Prove of greater reliability and improvement on maintenance costs without significant decrease in the quality of charging process with the removal of DC-link capacitors in rectifier and boost converter circuits is accomplished. The proposed circuit parameters are analyzed by carried out simulations.