An arrangement for injection-based ground fault protection handling including a number of stator windings of an electric machine that are connected to a neutral point, a first transformer including at least one primary winding connected to at least one measurement point of the stator windings and at least one secondary winding for measuring an electrical quantity of the machine at the measurement point. There is also a second transformer having a primary winding connected between the neutral point and a ground potential and a secondary winding for connection to a signal generation and detection unit in order to inject a signal into the neutral point and receive a response. The impedance of the second transformer is in the range of the impedance of the machine.

An electrical converter (203) having an active diode-clamped multilevel topology is shown. Each clamping diode is connected in antiparallel with a switch (S5A, S5B). The converter comprises polyphase supply phases (A, B, C) each of which are connected via a respective phase leg (401, 402, 403) to dc rails (301, 302) and a dc-link capacitor. The dc-link capacitor includes a plurality of series-connected capacitors (404, 405). A controller is configured to, in response to an event signal, for each phase leg, activate a combination of switches therein to form a pair of parallel conduction paths to a midpoint (406) between two capacitors in the dc-link capacitor, thereby connecting each phase to the same node.

A wind turbine generator controller is described. The controller comprises switching circuitry, for selectively activating and deactivating one or more transducer circuits, and overcurrent detection circuitry, for detecting an overcurrent state in relation to one or more of the transducer circuits. The switching circuitry is responsive to the detection on an overcurrent state to selectively deactivate one or more of the transducer circuits.

A wind turbine generator controller is described. The controller comprises switching circuitry, for selectively activating and deactivating one or more transducer circuits, and overcurrent detection circuitry, for detecting an overcurrent state in relation to one or more of the transducer circuits. The switching circuitry is responsive to the detection on an overcurrent state to selectively deactivate one or more of the transducer circuits.

A method for monitoring a bank of ultracapacitors configured to power an alternating current (AC) pitch motor of a pitch system in a wind turbine is provided. The method includes obtaining, by one or more control devices, data indicative of a voltage associated with the bank of ultracapacitors. The method includes conducting, by the one or more control devices, a test operation of the bank of ultracapacitors at predetermined intervals of time to determine a capacitance associated with the bank of ultracapacitors. The method further includes performing, by the one or more control devices, one or more control actions based, at least in part, on the capacitance or the data indicative of the voltage.

A method for monitoring a bank of ultracapacitors configured to power an alternating current (AC) pitch motor of a pitch system in a wind turbine is provided. The method includes obtaining, by one or more control devices, data indicative of a voltage associated with the bank of ultracapacitors. The method includes conducting, by the one or more control devices, a test operation of the bank of ultracapacitors at predetermined intervals of time to determine a capacitance associated with the bank of ultracapacitors. The method further includes performing, by the one or more control devices, one or more control actions based, at least in part, on the capacitance or the data indicative of the voltage.

A system includes a generator. Three AC feeders are connected for feeding AC output from the generator. A rectifier is electrically connected to the three AC feeders and to a load via a first DC feeder and a second DC feeder. A first resistor connects between a first one of the DC feeders and ground. A first voltage sensor is operatively connected to detect voltage across the first resistor. A second resistor connects between the second DC feeder and ground. A second voltage sensor is operatively connected to detect voltage across the second resistor. A controller is configured to monitor for changes in common mode voltage based on the input from the first sensor and from the second sensor, and to determine presence of a fault if change in the common mode voltage exceeds a predetermined threshold.

A system includes a generator. Three AC feeders are connected for feeding AC output from the generator. A rectifier is electrically connected to the three AC feeders and to a load via a first DC feeder and a second DC feeder. A first resistor connects between a first one of the DC feeders and ground. A first voltage sensor is operatively connected to detect voltage across the first resistor. A second resistor connects between the second DC feeder and ground. A second voltage sensor is operatively connected to detect voltage across the second resistor. A controller is configured to monitor for changes in common mode voltage based on the input from the first sensor and from the second sensor, and to determine presence of a fault if change in the common mode voltage exceeds a predetermined threshold.

Protection devices prevent damage to synchronous generators during loss-of-field events. In various embodiments, a first protective element is associated with a first protection zone to protect a generator from a loss-of-field event at full load. A second protective element is associated with a second protection zone to prevent thermal overload during underexcited operation of the generator and to protect from loss-of-filed at light load. A third protective element associated with a third protection zone limits operation of the generator within the generator's specific steady-state stability limits. A fourth protective element is associated with a fourth protection zone to provide an alarm prior to operation of the second protective element. In various embodiments, characteristics and limits of each of the protective elements are defined in the same plane (specifically, the P-Q plane) to simplify settings and allow for visualization of the element characteristics and the generator capability curve at one or more temperatures or cooling capacities.

A method for controlling a wind power plant, the wind power plant including a plant controller for controlling a plurality of wind turbine generators. The method for controlling a wind power plant allows the wind power plant to continue operating through a grid fault in a weak grid environment. In the method, a fault recovery process is carried out with a wind turbine power controller during a wind turbine fault recovery state to determine a grid voltage (VWTG), compare the grid voltage to a predetermined reference voltage (Vref) to obtain a difference value, and determine a current reference (QrefVC) based on the difference value for generating a reactive current (Idref) for regulating the grid voltage to the predetermined reference grid voltage. A corresponding wind power plant is further provided.