Abstract:
A wind turbine converter system (3) with a rectifier (4) and an inverter (5) and a converter controller (11) has at least first and second converter strings (24, 25). The converter system is controlled by a master-converter controller (13) and a slave-converter controller (12). The master-converter controller (13) controls the first converter string (25) and the slave-converter controller (12) controls the second converter string (24). The master-converter controller (13) receives commands from a superordinate wind turbine controller (21), provides the slave-converter controller (12) with string-control commands on the basis of the superordinate control commands, and controls the conversion operation of the first converter string (25) on the basis of the superordinate control command. The slave-converter controller (12) receives the string-control commands from the master-converter controller (13) and controls the conversion operation of the second converter string on the basis of the string-control commands received. The first and the second converter strings (24, 25) can be arranged in a bipolar configuration giving access to a neutral point (62). Fault detection can be performed based on the current through the neutral (62). The system is capable of fault ride-through. Also, in case of failure of the master-converter controller (13), a redundant unit takes its place.
Abstract:
A method of operating a wind turbine is provided. The wind turbine comprises a turbine rotor with at least one blade having a variable pitch angle, a power generator, and a power converter connected to the power generator via a first circuit breaker and to a power grid via a second circuit breaker. According to the method, overvoltage events at the power grid are monitored. If an overvoltage event is detected, the method comprises opening the first circuit breaker and the second circuit breaker, disabling active operation of the power converter, connecting a power dissipating unit to the power generator to dissipate power output from the power generator, and moving the pitch angle of the at least one blade towards a feathered position.
Abstract:
The invention relates to a method for controlling a wind turbine with a generator (1) comprising a stator (2), comprising a rotor (4) with at least two rotor poles (6), each of which comprises a pole winding (32, 42) for generating a magnetic field that is directed towards the respective rotor pole (6), and comprising an air gap (8) between the stator (2) and the rotor (4). The method has the following steps: - controlling each excitation current flowing through each pole winding (32, 42), - varying at least one of the excitation currents relative to at least one of the additional excitation currents, and/or - varying at least one of the excitation currents dependent on the position of the rotor (4) with respect to the stator (2).
Abstract:
A power converter configured to improve power capture in a wind turbine during low wind speed operation is disclosed. The power converter converts the power generated by the alternator of the wind turbine into a suitable AC current for delivery to a utility grid or to an electric load independent of the utility grid. The power converter is configured to operate in multiple operating modes, utilizing both synchronous and non-synchronous control methods, to extend the operating range of the power converter. During non-synchronous operation, the power converter utilizes a modulation routine that may either vary the dead-time compensation period during a constant modulation period or vary the modulation period with a constant on-time. A seamless transfer between non-synchronous and synchronous control methods with low total harmonic distortion (THD) improves the range of power generation for wind generators.
Abstract:
A method of operating a power generation system includes operating a power generation system to generate an electric power output. At least a portion of the electric power output is dissipated in a flow battery by charging the flow battery using the portion of the electric power output and self-discharging the flow battery.
Abstract:
A method and a system for generating auxiliary power for an islanded wind turbine are described, wherein the wind turbine may comprise a generator configured to provide power to a main grid. The method comprises: detecting an island mode of operation wherein said wind turbine is electrically disconnected from said main grid; in response to said disconnection, adjusting the rotational speed of said wind turbine to a value within a range of low rotational speeds; converting said generator output to a value suitable for charging said auxiliary power distribution system; and, connecting the output of said converter to said auxiliary power distribution system.
Abstract:
A wind power plant is provided. The wind power plant comprises at least one wind turbine and a power plant controller. The power plant controller is configured to detect whether a grid voltage exceeds a predefined threshold, and if it has detected that the grid voltage exceeds the predefined threshold, the power plant controller sends a reactive power reference to the at least one wind turbine, thereby causing the at least one wind turbine to reduce its reactive power output in response to the reactive power reference.