Abstract: A method for operating a multi-level bridge power converter includes arranging a plurality of switching devices including at least four inner switching devices and at least two outer switching devices in an active neutral point clamped topology. The method also includes determining whether any of the switching devices is experiencing a failure condition by implementing a failure detection algorithm. The failure detection algorithm includes generating a blocking state logic signal by comparing a switching device voltage and a threshold reference voltage for each of the switching devices, determining an expected voltage blocking state for each of the switching devices based on gate drive signals of the switching devices and an output current direction, and detecting whether a failure condition is present in any of the switching devices based on the blocking state logic signals and the expected voltage blocking states of the switching devices.

Abstract: A method and associated system provide grid-forming mode (GFM) control of an inverter-based renewable energy source having an asynchronous machine connected to a power grid. The method includes deriving a power error signal (PER) between a real power output (PB) from the renewable energy source and a power reference (PREF) representing a desired power output of the renewable energy source. With an inertial power regulator, a phase shift angle (?IT) is generated from the power error signal (PER) to provide virtual synchronous machine (VSM) control functionality to the GFM control of the renewable energy source. A power angle compensation (??) is applied to the phase shift angle (?IT) from the inertial power regulator to dampen power oscillations and load fluctuations during transient power events.

Abstract: A method for operating a generator of a wind turbine includes generating, via a controller, a time series of a plurality of operating signals of the generator. The method also includes applying at least one algorithm to the time series of the plurality of operating signals of the generator to generate a processed time series of the of the plurality of operating signals of the generator. Moreover, the method includes identifying, via the controller, patterns in the processed time series of the plurality of operating signals of the generator to identify one or more of at least one slip event occurring in the slip coupling or a surface health of the slip coupling. Further, the method includes implementing, via the controller, a control action when the at least one slip event occurring in the slip coupling is identified or the surface health of the slip coupling is indicative of degradation in the slip coupling.

Abstract: A method for operating a power system connected to a power grid includes providing an active filter in the converter power path. Further, the method includes determining a change in attenuation of harmonics of the power system over a predetermined frequency spectrum that is needed to comply with one or more grid code requirements of the power grid. Thus, the method includes actively controlling, via a controller, the active filter to provide the change to the attenuation of the harmonics of the power system so as to mitigate the harmonics of the power system.

Abstract: A system and method are provided for controlling a wind turbine. Accordingly, a controller of the wind turbine detects a transient grid event and generates a torque command via a drive-train-damper control module. The torque command is configured to establish a default damping level of a torsional vibration resulting from the transient grid event. The controller also determines at least one oscillation parameter relating to the torsional vibration and determines a target generator torque level based thereon. The target generator torque level corresponds to an increased level of damping the torsional vibration relative to the default damping level.

Abstract: A method for mitigating voltage disturbances at a point of interconnection (POI) of a grid-forming inverter-based resource (IBR) due to flicker includes receiving a voltage reference command and a voltage feedback. The voltage feedback contains information indicative of the voltage disturbances at the POI due to the flicker. The method also includes determining a power reference signal for the IBR based on the voltage reference command and the voltage feedback. Moreover, the method includes generating a current vector reference signal based on the power reference signal, the current vector reference signal containing a frequency component of the voltage disturbances. Further, the method includes generating a transfer function of a regulator based on the frequency component to account for the flicker effect. In addition, the method includes generating a current vector based on a comparison of the current vector reference signal and a current vector feedback signal.

Abstract: A method of mitigating high frequency harmonics in an output current of an electrical power system connected to a power grid includes providing an active harmonic filter in a stator power path connecting a stator of the generator to the power grid. Further, the method includes controlling, via a controller, the active harmonic filter to selectively extract a high frequency harmonic component from the output current. The method also includes determining, via the controller, whether the high frequency harmonic component is a positive sequence harmonic or a negative sequence harmonic. Moreover, the method includes compensating, via the controller, for the high frequency harmonic component based on whether the high frequency harmonic component is the positive sequence harmonic or the negative sequence harmonic to mitigate the high frequency harmonics in the output current.

Abstract: A method of mitigating high frequency harmonics in an output current of an electrical power system connected to a power grid includes providing an active harmonic filter in a stator power path connecting a stator of the generator to the power grid. Further, the method includes controlling, via a controller, the active harmonic filter to selectively extract a high frequency harmonic component from the output current. The method also includes determining, via the controller, whether the high frequency harmonic component is a positive sequence harmonic or a negative sequence harmonic. Moreover, the method includes compensating, via the controller, for the high frequency harmonic component based on whether the high frequency harmonic component is the positive sequence harmonic or the negative sequence harmonic to mitigate the high frequency harmonics in the output current.

Abstract: A method for operating an asynchronous inverter-based resource connected to a power grid as a virtual synchronous machine to provide grid-forming control thereof includes receiving a frequency reference command and/or a voltage reference command. The method also includes determining at least one power reference signal for the inverter-based resource based on the frequency reference command and/or the voltage reference command. Further, the method includes generating at least one current vector using the power reference signal(s). Moreover, the method includes determining one or more voltage control commands for the inverter-based resource using the at least one current vector.

Abstract: Systems and methods are disclosed for improved fault diagnostics of electrical machines under dynamic load oscillations. The systems and methods may rely on one or more different algorithms for performing such fault diagnostics. One example, algorithm may involve determining a ratio of an instantaneous real power and a reactive power of the motor.

Abstract: The present application relates to a method for controlling a power system connected to a power grid, including: receiving a reactive power instruction and a measured reactive power from a generator; generating a reactive power error signal based on the difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal; generating a voltage instruction based on reactive power error signal; generating a voltage droop signal based on a reference reactance and a voltage at a point of common coupling; generating a voltage error signal according to at least one of the voltage instruction or the measured terminal voltage of the generator and the voltage droop signal; and producing a reactive current instruction for the converter power path based on the voltage error signal. The present application also discloses a control system for a power system connected to a power grid and a wind farm.

Abstract: The system and method described herein provide grid-forming control of a power generating asset having a double-fed generator connected to a power grid. Accordingly, a stator-frequency error is determined for the generator. The components of the stator frequency error are identified as a torsional component corresponding to a drivetrain torsional vibration frequency and a stator component. Based on the stator component, a power output requirement for the generator is determined. This power output requirement is combined with the damping power command to develop a consolidated power requirement for the generator. Based on the consolidated power requirement, at least one control command for the generator is determined and an operating state of the generator is altered.

Abstract: The present application relates to a method for controlling a power system connected to a power grid, including: receiving a reactive power instruction and a measured reactive power from a generator; generating a reactive power error signal based on the difference between the reactive power instruction and the measured reactive power; receiving the reactive power error signal; generating a voltage instruction based on reactive power error signal; generating a voltage droop signal based on a reference reactance and a voltage at a point of common coupling; generating a voltage error signal according to at least one of the voltage instruction or the measured terminal voltage of the generator and the voltage droop signal; and producing a reactive current instruction for the converter power path based on the voltage error signal. The present application also discloses a control system for a power system connected to a power grid and a wind farm.

Abstract: A method for preventing damage in a bearing of a generator of an electrical power system includes monitoring one or more electrical signals of a power conversion assembly of the electrical power system. The method also includes estimating an impedance path of common mode current from a terminal to ground using the operating parameter(s) of the power conversion assembly. Further, the method includes determining a one or more magnitudes and/or a one or more phase angles of the impedance path at different frequencies, such a switching frequency and/or harmonics. Moreover, the method includes determining whether the impedance path is indicative of degradation in at least one of bearing insulation or a ground brush of the generator based on a change in the one or more magnitudes and/or the one or more phase angles. In addition, the method includes implementing a control action when the impedance path is indicative of degradation in the bearing insulation and/or the ground brush of the generator.

Abstract: A method for mitigating voltage disturbances at a point of interconnection (POI) of a grid-forming inverter-based resource (IBR) due to flicker includes receiving a voltage reference command and a voltage feedback. The voltage feedback contains information indicative of the voltage disturbances at the POI due to the flicker. The method also includes determining a power reference signal for the IBR based on the voltage reference command and the voltage feedback. Moreover, the method includes generating a current vector reference signal based on the power reference signal, the current vector reference signal containing a frequency component of the voltage disturbances. Further, the method includes generating a transfer function of a regulator based on the frequency component to account for the flicker effect. In addition, the method includes generating a current vector based on a comparison of the current vector reference signal and a current vector feedback signal.

Abstract: The system and method described herein provide grid-forming control of a power generating asset having a generator, such as a double-fed generator, connected to a power grid. Accordingly, a stator-frequency error is determined for the generator. The components of the stator frequency error are identified as a damping component corresponding to a tower damping frequency and a stator component. Based on the stator component, a power output requirement for the generator is determined. This power output requirement is combined with the damping power command to develop a consolidated power requirement for the generator. Based on the consolidated power requirement, at least one control command for the generator is determined and an operating state of the generator is altered.

Abstract: The system and method described herein provide grid-forming control of a power generating asset having a double-fed generator connected to a power grid. Accordingly, a stator-frequency error is determined for the generator. The components of the stator frequency error are identified as a torsional component corresponding to a drivetrain torsional vibration frequency and a stator component. Based on the stator component, a power output requirement for the generator is determined. This power output requirement is combined with the damping power command to develop a consolidated power requirement for the generator. Based on the consolidated power requirement, at least one control command for the generator is determined and an operating state of the generator is altered.

Abstract: A method for preventing damage in a bearing of a generator includes monitoring, via a controller, one or more electrical signals of the power conversion assembly. The method also includes converting the electricals signal(s) to a frequency domain. Further, the method includes extracting one or more spectral components in frequency bands of the frequency domain around one or more known characteristic frequencies of the bearing. Moreover, the method includes determining at least one characteristic of the spectral component(s) in the frequency bands. In addition, the method includes comparing the characteristic(s) of the spectral component(s) in the frequency bands to at least one baseline value. The method further includes generating a fault signal or a baseline signal for the bearing based on the comparison. In response to the fault signal being generated, the method includes implementing a control action.

Abstract: A method for operating a generator of a wind turbine includes generating, via a controller, a time series of a plurality of operating signals of the generator. The method also includes applying at least one algorithm to the time series of the plurality of operating signals of the generator to generate a processed time series of the of the plurality of operating signals of the generator. Moreover, the method includes identifying, via the controller, patterns in the processed time series of the plurality of operating signals of the generator to identify one or more of at least one slip event occurring in the slip coupling or a surface health of the slip coupling. Further, the method includes implementing, via the controller, a control action when the at least one slip event occurring in the slip coupling is identified or the surface health of the slip coupling is indicative of degradation in the slip coupling.

Abstract: A method for preventing damage in a bearing of a generator includes monitoring, via a controller, one or more electrical signals of the power conversion assembly. The method also includes converting the electricals signal(s) to a frequency domain. Further, the method includes extracting one or more spectral components in frequency bands of the frequency domain around one or more known characteristic frequencies of the bearing. Moreover, the method includes determining at least one characteristic of the spectral component(s) in the frequency bands. In addition, the method includes comparing the characteristic(s) of the spectral component(s) in the frequency bands to at least one baseline value. The method further includes generating a fault signal or a baseline signal for the bearing based on the comparison. In response to the fault signal being generated, the method includes implementing a control action.