Abstract: Method and apparatus are provided for determining a grid condition, such as a weakened grid condition, and controlling a power plant, such as a wind or solar power plant, in a manner which is appropriate to the grid condition. The method includes measuring (14) output parameters of a generator, such as a wind turbine or PV generator. The measured output parameters include reactive power and voltage. The method further includes determining (16) a relationship between the measured output parameters of the generator. The relationship between the measured output parameters of the generator is indicative of a condition of a power grid to which the plant supplies power. The method allows controlling (18) the plant responsive to the relationship between the measured output parameters of the generator to avoid onset of oscillatory behavior, which could otherwise occur in the power plant in the presence of a weakened grid condition.

Abstract: A method and a controller for continuously operating a plurality of electric energy generating machines during a high voltage condition at a point of common coupling of the plurality of electric energy generating machines are provided herein. The method includes a) sensing a voltage level at the point of common coupling exceeding a permitted voltage level; b) curtailing an active power output of the plurality of electric energy generating machines such that a reactive capability of the plurality of electric energy generating machines is increased; c) establishing a set point of an electric quantity being present at the point of common coupling such that a reactive electric component providable by the electric energy generating machines is increased; and d) controlling an electric energy generating machine based on the set point of the electric quantity such that the high voltage condition at common coupling is at least partially remedied.

Abstract: A wind turbine generator park (1) for supplying power to a power system (37), the park having an assigned first droop response characteristic for use in responding to an under-frequency occurrence on the power system (37). The park comprises a first comparator (108) for generating a first signal when the park is operating according to a curtailed condition, a second comparator (100) for indicating that a change in a frequency of a voltage or current on the power system (37) is greater than a first threshold value, and a controller (114) responsive to the first and second signals for controlling the park according to a second response characteristic causing the park (1) to supply an amount of power to the power system (37) greater than the power supplied according to the first droop response characteristic.

Abstract: Method and apparatus are provided for determining a grid condition, such as a weakened grid condition, and controlling a power plant, such as a wind or solar power plant, in a manner which is appropriate to the grid condition. The method includes measuring (14) output parameters of a generator, such as a wind turbine or PV generator. The measured output parameters include reactive power and voltage. The method further includes determining (16) a relationship between the measured output parameters of the generator. The relationship between the measured output parameters of the generator is indicative of a condition of a power grid to which the plant supplies power. The method allows controlling (18) the plant responsive to the relationship between the measured output parameters of the generator to avoid onset of oscillatory behavior, which could otherwise occur in the power plant in the presence of a weakened grid condition.

Abstract: A method and a controller for continuously operating a plurality of electric energy generating machines during a high voltage condition at a point of common coupling of the plurality of electric energy generating machines are provided herein. The method includes a) sensing a voltage level at the point of common coupling exceeding a permitted voltage level; b) curtailing an active power output of the plurality of electric energy generating machines such that a reactive capability of the plurality of electric energy generating machines is increased; c) establishing a set point of an electric quantity being present at the point of common coupling such that a reactive electric component providable by the electric energy generating machines is increased; and d) controlling an electric energy generating machine based on the set point of the electric quantity such that the high voltage condition at common coupling is at least partially remedied.

Abstract: A wind turbine generator park (1) for supplying power to a power system (37), the park having an assigned first droop response characteristic for use in responding to an under-frequency occurrence on the power system (37). The park comprises a first comparator (108) for generating a first signal when the park is operating according to a curtailed condition, a second comparator (100) for indicating that a change in a frequency of a voltage or current on the power system (37) is greater than a first threshold value, and a controller (114) responsive to the first and second signals for controlling the park according to a second response characteristic causing the park (1) to supply an amount of power to the power system (37) greater than the power supplied according to the first droop response characteristic.

Abstract: A method and system for controlling the output power from a renewable energy installation (10) to a utility grid (56) having a predetermined bound for a variation in output power per unit of time is provided. The method and system includes constraining an output signal of a controller (76) to an upper and/or lower limit via a limiter (78), wherein the upper and/or lower limit comprises a predetermined upper and/or lower bound for a variation in output power per unit of time. The constrained output signal is then applied to the plurality of electricity generators (12, 14, 16) to limit the variation in output power per unit of time according to the predetermined bound.