A measurement data based method for identifying wind turbine generators which cause sub-synchronous oscillations in a complex power system has a theoretical foundation of the open-loop modal resonance and the parallel filter design. The advantages of the present invention are as follows. 1) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system using measurement data instead of parametric model. Hence, it simplifies the computation and reduces the modeling cost effectively. 2) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system precisely with reduced amount of measurement data, reducing the cost of hardware and data measurement effectively. 3) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system based on the open-loop modal resonance theory.

An airfoil body may include a plurality of tubercles along a leading edge of the airfoil body and a plurality of crenulations along a trailing edge of the airfoil body, wherein at least one of a position, a size, and a shape of the plurality of tubercles and the plurality of crenulations varies in a non-periodic fashion. The non-periodic fashion may be according to a Fibonacci function and may mimic the configuration of a pectoral fin of a humpback whale. The tubercles and crenulations may be defined with respect to a pivot point. The spanwise profile, including the max chord trailing edge curvature, may closely follow divine spirals and related Fibonacci proportions. The spanwise chord thickness may vary in a nonlinear pattern. Related methods are also described.

The invention relates to a method for producing or designing a leading edge of a lifting structure, wherein starting at the midpoint of the base (0,0), a curve is applied to the profile of the structure, the length L.sub.1 of which is according to the maximum thickness of the NACA section in the base of the profile H.sub.0 in the base and is defined by the equation L.sub.1=0.0510H.sub.0.sup.20.0790H.sub.0+15.5790, and the maximum height of which on the x-axis is located at point L.sub.1/2 and defined by means of the relationship x=0.0137(L.sub.1).sup.1.4944, the shape of said curve being defined by means of the equation: (yy.sub.0)=0.0000000107x.sup.6+0.0000016382x.sup.50.0000794412x.sup.4+0.0010194142x.sup.3+0.0097205322x.sup.2+0.0136993913x, and the rest of the curve being calculated by means of an iterative process according to the above.

A measurement data based method for identifying wind turbine generators which cause sub-synchronous oscillations in a complex power system has a theoretical foundation of the open-loop modal resonance and the parallel filter design. The advantages of the present invention are as follows. 1) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system using measurement data instead of parametric model. Hence, it simplifies the computation and reduces the modeling cost effectively. 2) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system precisely with reduced amount of measurement data, reducing the cost of hardware and data measurement effectively. 3) The present invention can identify the wind turbine generators which cause the SSOs in the complex power system based on the open-loop modal resonance theory.

The invention relates to a method for producing or designing a leading edge of a lifting structure, wherein starting at the midpoint of the base (0,0), a curve is applied to the profile of the structure, the length L.sub.1 of which is according to the maximum thickness of the NACA section in the base of the profile H.sub.0 in the base and is defined by the equation L.sub.1=0.0510H.sub.0.sup.20.0790H.sub.0+15.5790, and the maximum height of which on the x-axis is located at point L.sub.1/2 and defined by means of the relationship x=0.0137(L.sub.1).sup.1.4944, the shape of said curve being defined by means of the equation: (yy.sub.0)=0.0000000107x.sup.6+0.0000016382x.sup.50.0000794412x.sup.4+0.0010194142x.sup.3+0.0097205322x.sup.2+0.0136993913x, and the rest of the curve being calculated by means of an iterative process according to the above.

A hydraulic turbine according to an embodiment includes a turbine body, a running water surface provided in the turbine body, the running water surface defining a channel for water, and a coating layer provided on the running water surface, the coating layer being formed by water-repellent paint or hydrophilic paint.

An airfoil body may include a plurality of tubercles along a leading edge of the airfoil body and a plurality of crenulations along a trailing edge of the airfoil body, wherein at least one of a position, a size, and a shape of the plurality of tubercles and the plurality of crenulations varies in a non-periodic fashion. The non-periodic fashion may be according to a Fibonacci function and may mimic the configuration of a pectoral fin of a humpback whale. The tubercles and crenulations may be defined with respect to a pivot point. The spanwise profile, including the max chord trailing edge curvature, may closely follow divine spirals and related Fibonacci proportions. The spanwise chord thickness may vary in a nonlinear pattern. Related methods are also described.

Embodiments of the present invention generally relate to a new controller and a new control method for a hydraulic turbine and a synchronous generator, particularly to attenuate the effect of the vortex rope pressure oscillations on the active power.