Many rationally parametrized elliptic modular equations are derived. Each comes from a family of elliptic curves attached to a genus-zero congruence subgroup Γ0(N), as an algebraic transformation of elliptic curve periods, parametrized by a Hauptmodul (function field generator). The periods satisfy a Picard–Fuchs equation, of hypergeometric, Heun, or more general type; so the new modular equati...

In recent years, wind energy has become one of the most important and promising sources of renewable energy, which demands additional transmission capacity and better means of maintaining system reliability. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed spe...

This paper presents a new synchronization algorithm for grid connection of a doubly fed induction generator (DFIG) in a variable speed wind generation system. Stator flux-oriented vector control for backto-back PWM converters in the DFIG rotor circuit is used for synchronization process. By controlling the rotor d-axis current, the magnitude of the stator EMF is adjusted to be equal to the grid...

In this work we investigate some computational aspects of the eigenvalue calculation with edge elements; those include: the importance of the grid generator and nodeedge numbering. As the examples show, the sparse structure of the mass and stiffness matrices is highly influenced by the edge numbering. Tetrahedral grid generators are mainly designed for nodal based finite elements so an edge num...

An adaptive multilevel wavelet collocation method for solving multi-dimensional elliptic problems with localized structures is described. The method is based on multi-dimensional second generation wavelets, and is an extension of the dynamically adaptive second generation wavelet collocation method for evolution problems [Int. J. Comp. Fluid Dyn. 17 (2003) 151]. Wavelet decomposition is used fo...

This paper presents a coordinated control strategy for a hybrid wind farm with doubly-fed induction generator (DFIG)and direct-driven permanent-magnet synchronous generator (PMSG)-based wind turbines under symmetrical grid faults. The proposed low-voltage ride-through (LVRT) strategy is based on a novel current allocation principle and is implemented for individual DFIGor PMSG-based wind turbin...

The fast adaptive composite grid (FAC) method is a systematic process for solving differential boundary value problems. FAC uses global and local uniform grids both to define the composite grid problem and to interact for its fast solution. It can with little added cost substantially improve accuracy of the coarse grid solution and is very suitable for vector and parallel computation. This pape...

The doubly-fed generators (DFIG) have clear superiority for the applications of large capacity and limited-range speed control case due to the partially rated inverter, lower cost and high reliability. These characteristics enable the doubly-fed wound rotor induction machine to have vast applications in wind-driven generation.In this paper Combined Vector and direct power control (CVDPC) strate...

The matrix converter has many advantages in wind power system applications. Matrix converter is compact and highly efficient because it directly converts generated power from AC generator to AC grid without intermediate DC bus while conventional back-to-back converter systems requires many electrolytic capacitors in DC link bus which are bulky and have short life-time. Matrix converter has both...