Abstract: Systems and methods of wind power generation in electrical power systems are described. According to one aspect, a wind turbine system can include a down tower portion having a main transformer configured to transform medium voltage power to another voltage power, a tower portion having one or more medium voltage cables configured to transmit medium voltage power, and, a nacelle portion. The nacelle portion can include a generator comprising a stator and a rotor. The stator may be connected to one or more medium voltage cables via a stator power path. The nacelle portion also includes a power converter coupled to the rotor of the generator, and, a step-up transformer coupled to the power converter and the one or more medium voltage cables. The step-up transformer can be configured to step-up low voltage power to medium voltage power.

Abstract: A wind farm is presented. The wind farm includes a plurality of wind turbine stations, where each wind turbine station includes a wind turbine and a generator sub-system. The generator sub-system includes a doubly-fed induction generator configured to generate an alternating current voltage and a wind turbine station power converter. The wind farm further includes a power collection sub-system that includes a power bus and a sub-station power converter. The wind farm also includes a control system configured to determine a wind speed metric, estimate a corresponding frequency metric, calculate a desirable frequency based on the wind speed metric and frequency compensation ranges of the wind turbine station power converters, and generate and communicate control commands to the sub-station power converter based on the desirable frequency to allow the sub-station power converter to update a line frequency of a power bus voltage based on the desirable frequency.

Abstract: A method for isolating faults in an electrical power system connected to a power grid includes dividing the electrical power system into a plurality of power modules each including a plurality of electrical power subsystems and a substation. Each of the electrical power subsystems defines a stator power path and a converter power path for providing power to the power grid and having a partial power transformer. The method also includes coupling each of the power modules to the power grid via a primary electrical line. Further, the method includes monitoring the electrical power system for faults. In response to detecting a fault in one of the power modules, the method includes isolating the fault to the power module experiencing the fault. In contrast, if the fault is detected in the primary electrical line or the power grid, the method includes tripping the electrical power system.

Abstract: A power generation system is disclosed. The power generation system includes an engine coupled to a DFIG and a PV power source to supply a solar electrical power to the DFIG (108). The power generation system also includes a controller configured to operate the engine at a first operating speed corresponding to a first determined efficiency of the engine for a first desired level of an engine power in a first operating condition; or operate the engine at a second operating speed corresponding to a desired level of the second electrical power to be absorbed by a rotor winding and a second desired level of the engine power in a second operating condition, wherein the determined first efficiency is substantially close to a first maximum achievable efficiency of the engine. Method of operating the power generation system is also disclosed.

Abstract: An electrical power subsystem includes a generator comprising a generator stator and a generator rotor, and a power converter electrically coupled to the generator. The power converter includes a plurality of rotor-side converters electrically coupled in parallel, a line-side converter, and a regulated DC link electrically coupling the plurality of rotor-side converters and the line-side converter. The electrical power subsystem further includes a stator power path for providing power from the generator stator to the power grid, and a converter power path for providing power from the generator rotor through the power converter to the power grid.

Abstract: An electrical power system includes a cluster of electrical power subsystems, each of the electrical power subsystems including a power converter electrically coupled to a generator having a generator rotor and a generator stator. Each of the electrical power subsystems defines a stator power path and a converter power path for providing power to the power grid. The converter power path includes a partial power transformer. The electrical power system further includes a subsystem breaker configured with each of the electrical power subsystems, and a cluster transformer for connecting each cluster of electrical power subsystems to the power grid. The electrical power system further includes a cluster power path extending between each subsystem breaker and the cluster transformer, and a distortion filter electrically coupled to the cluster transformer. The distortion filter reduces harmonics in current flowing from the electrical power subsystems to the cluster transformer.

Abstract: An electrical power system connected to a power grid can include a generator having a stator and a rotor and a power converter. The stator is connected to the power grid via a stator power path. The power converter can include a line-side converter coupled to the power grid via a converter power path and a rotor-side converter coupled to a rotor bus of the rotor and the line-side converter via a DC link. The rotor-side converter is configured to convert a DC power on the DC link to an AC signal for the rotor bus. The power system can also include an active filter having one or more active controlled components. The active filter is coupled in parallel with the rotor-side converter to reduce harmonics of the electrical power system.

Abstract: An electrical power system includes a system-level controller and a plurality of clusters of subsystems defining a stator power path and a converter power path for providing power to the power grid. The converter power path includes a partial power transformer. The system further includes a cluster transformer connecting each cluster to the power grid and a plurality of cluster-level controllers communicatively coupled with the system-level controller. Each of the clusters is communicatively coupled with one of the cluster-level controllers. Thus, the system-level controller regulates system-level active and/or reactive power based on required active or reactive power for the system, respectively, and compares the system-level active or reactive power with preferred values thereof.

Abstract: A method for controlling voltage of a DC link of a power converter of an electrical power system connected to a power grid includes operating the DC link to an optimum voltage set point that achieves steady state operation of the power converter. The method also includes monitoring the power grid for one or more transient events that may be an indicator of one or more sub-synchronous control interaction (SSCI) conditions occurring in the electrical power system. Upon detection of the transient event(s) occurring in the power grid, the method also includes immediately increasing the optimum voltage set point to a higher voltage set point of the DC link. Moreover, the method includes operating the DC link at the higher voltage set point until the sub-synchronous control interaction(s) is damped, thereby optimizing voltage control of the DC link.

Abstract: A method for controlling an electrical power system connected to a power grid includes receiving a reactive power command and a measured reactive power and generating a reactive power error signal based on a difference between the reactive power command and the measured reactive power. Further, the method includes receiving, via a reactive power regulator, the reactive power error signal. Moreover, the method includes generating, via the reactive power regulator, a voltage command based on the error signal. The method also includes generating, via a droop control, a voltage droop signal. In addition, the method includes generating a voltage error signal as a function of the voltage droop signal and at least one of the voltage command or a measured terminal voltage. Thus, the method further includes generating, via a voltage regulator, a reactive current command based on the voltage error signal.

Abstract: A method for controlling voltage of a DC link of a power converter of an electrical power system connected to a power grid includes operating the DC link to an optimum voltage set point that achieves steady state operation of the power converter. The method also includes monitoring the power grid for one or more transient events that may be an indicator of one or more sub-synchronous control interaction (SSCI) conditions occurring in the electrical power system. Upon detection of the transient event(s) occurring in the power grid, the method also includes immediately increasing the optimum voltage set point to a higher voltage set point of the DC link. Moreover, the method includes operating the DC link at the higher voltage set point until the sub-synchronous control interaction(s) is damped, thereby optimizing voltage control of the DC link.

Abstract: A power system is presented. The power system includes a first converter including a first output terminal a first control unit coupled to the first converter, a second converter including a second output terminal, where the second converter is coupled in parallel to the first converter, and a second control unit coupled to the second converter. The second control unit is configured to measure a plurality of phase currents at the second output terminal, determine a harmonic current transmitted by the second converter based on single phase current of the plurality of measured phase currents, and change a time-period of at least one switching cycle of a carrier wave of the second converter based on the determined harmonic current to synchronize with a carrier wave of the first converter.

Abstract: Power converters for use in wind turbine systems are included. For instance, a wind turbine system can include a full power generator having a stator and a rotor. The generator is configured to provide a low voltage alternating current power on a stator bus of the wind turbine system. The wind turbine system includes a power converter configured to convert the low voltage alternating current power provided on the stator bus to a medium voltage multiphase alternating current output power suitable for provision to the electrical grid. The power converter includes a plurality of conversion modules, each conversion module comprising a plurality of bridge circuits. Each bridge circuit includes a plurality of silicon carbide switching devices coupled in series. Each conversion module is configured to provide a single phase of the medium voltage multiphase alternating current output power on a line bus of the wind turbine system.

Abstract: Systems and methods of wind power generation in electrical power systems are described. According to one aspect, a wind turbine system can include a down tower portion having a main transformer configured to transform medium voltage power to another voltage power, a tower portion having one or more medium voltage cables configured to transmit medium voltage power, and, a nacelle portion. The nacelle portion can include a generator comprising a stator and a rotor. The stator may be connected to one or more medium voltage cables via a stator power path. The nacelle portion also includes a power converter coupled to the rotor of the generator, and, a step-up transformer coupled to the power converter and the one or more medium voltage cables. The step-up transformer can be configured to step-up low voltage power to medium voltage power.

Abstract: A hybrid power generation system is presented. The system includes a first power generation subsystem including a prime mover driving a generator including a rotor and a stator, one or more first conversion units coupled to at least one of the rotor and the stator, a first direct current (DC) link, and one or more second conversion units coupled to a corresponding one or more first conversion units via the first DC link. The system includes one or more second power generation subsystems coupled to the first power generation subsystem and one or more power conversion subunits including one or more first bridge circuits coupled to a corresponding one or more second bridge circuits via one or more transformers, where at least one of the one or more second power generation subsystems and the first power generation subsystem includes the one or more power conversion subunits.

Abstract: A method for operating a wind turbine during partial load operation includes determining a power output of the wind turbine. The method also includes determining whether the power output is below a rated power of the wind turbine. If the power output is at the rated power, the method includes maintaining a speed set point of the wind turbine equal to a rated speed set point. However, if the power output is below the rated power, then the method includes varying, via a controller, the speed set point of the wind turbine as a function of a torque of the wind turbine in a non-monotonic torque-speed relationship.

Abstract: Systems and methods for operating a cluster transformer operably coupled to cluster of DFIG wind turbines in low-wind conditions are provided. A wind turbine cluster system can include at least one DFIG module, a cluster transformer, and a control device configured to control operation of the cluster transformer based at least in part on a wind parameter. Each DFIG module can include a doubly fed induction generator comprising a rotor configured to generate AC power at a first voltage, a stator configured to generate AC power at a second voltage, and a power conversion system coupled to the rotor to convert power at the first voltage to power at the second voltage. The cluster transformer can be configured to receive power at the second voltage from the at least one DFIG module and convert the power at the second voltage to power at a third voltage.

Abstract: A wind farm is presented. The wind farm includes a plurality of wind turbine stations, where each wind turbine station includes a wind turbine and a generator sub-system. The generator sub-system includes a doubly-fed induction generator configured to generate an alternating current voltage and a wind turbine station power converter. The wind farm further includes a power collection sub-system that includes a power bus and a sub-station power converter. The wind farm also includes a control system configured to determine a wind speed metric, estimate a corresponding frequency metric, calculate a desirable frequency based on the wind speed metric and frequency compensation ranges of the wind turbine station power converters, and generate and communicate control commands to the sub-station power converter based on the desirable frequency to allow the sub-station power converter to update a line frequency of a power bus voltage based on the desirable frequency.

Abstract: A method for reactive power control of a wind farm having a plurality of clusters of wind turbines with a cluster transformer connecting each cluster of wind turbines to a power grid is provided. The method includes receiving, via a plurality of cluster-level controllers, a reactive power command from a farm-level controller. The method also includes generating, via the cluster-level controllers, a cluster-level reactive current command for each cluster of wind turbines based on the reactive power command. Further, the method includes distributing, via the cluster-level controllers, a turbine-level reactive current command to turbine-level controllers of the wind turbines based on the cluster-level reactive current command.

Abstract: An electrical power system includes a cluster of electrical power subsystems, each of the electrical power subsystems including a power converter electrically coupled to a generator having a generator rotor and a generator stator. Each of the electrical power subsystems defines a stator power path and a converter power path for providing power to the power grid, the converter power path including a partial power transformer. Each of the electrical power subsystems further includes a low voltage distribution panel electrically coupled to the converter power path, a first switch on the stator power path, and a second switch on the converter power path.