Abstract: While transient current magnitudes at different locations within a DC distribution system themselves are not a reliable indicator of fault location, it is recognized herein that accumulating energy or pseudo energy values provides a reliable basis for tripping the protection element at a fault location. Thus, in one aspect of the teachings herein, pseudo energy values are accumulated independently during a fault condition, for each of one or more protected branch circuits and the protection element for each such branch circuit is tripped responsive to the accumulated pseudo energy values reaching a defined pseudo energy threshold. The pseudo energy thresholds are defined so that the protection element in the branch circuit where the fault is located will trip first.

Abstract: According to one aspect of the teachings herein, various feeder connection arrangements and architectures are disclosed, for collecting electricity from wind turbines in an offshore collection grid that operates at a fixed low frequency, e.g., at one third of the targeted utility grid frequency. Embodiments herein detail various feeder arrangements, such as the use of parallel feeder connections and cluster-based feeder arrangements where a centralized substation includes a common step-up transformer for outputting electricity at a stepped-up voltage, for low-frequency transmission to onshore equipment. Further aspects relate to advantageous generation arrangements, e.g., tower-based arrangements, for converting wind power into electrical power using, for example, medium-speed or high-speed gearboxes driving generators having a rated electrical frequency for full-power output in a range from about 50 Hz to about 150 Hz, with subsequent conversion to the fixed low frequency for off-shore collection.

Abstract: According to one aspect of the teachings herein, a system for obtaining electricity from wind turbines provides advantageous operation with respect to offshore wind turbines where the size and weight of electricity generation and collection equipment are key considerations. The contemplated system includes an apparatus that is configured for collecting wind-generated electricity at a fixed low frequency and at a desired collection voltage, based on the advantageous configuration and use of a modular multilevel converter or MMC.

Abstract: Methods, systems, and computer readable media for adaptive out of step protection for power generators with load resynchronization capability are disclosed. According to one method, when a fault condition occurs in a load being supplied by a power generator, a number of pole slips expected to occur in the generator due to the fault before resynchronization is estimated. It is determined whether the estimated number of pole slips exceeds a threshold. An offline or online status of the generator is controlled based on the determination as to whether the estimated number of pole slips exceeds the threshold.

Abstract: Connection schemes for offshore power generation with an internal collection grid include a power generation system which includes a plurality of generator-rectifier subsystems. The scheme further includes a medium voltage DC (MVDC) collection network with positive pole cables and negative pole cables connected to the DC outputs of the generator-rectifier subsystems. At least one offshore substation includes a positive bus bar and a negative bus bar correspondingly connected to the positive pole cables and negative pole cables of the MVDC collection network and a plurality of main DC-DC converters. Each main DC-DC converter includes multiple modules connected to the MVDC bus bars and each module has a positive and a negative output such that the modules' outputs are serially connected to one another. The schemes may also include a high voltage DC (HVDC) transmission system connected to the modules' outputs and at least one DC/AC converter at an onshore substation.

Abstract: An improved method of fault detection in a high-voltage direct current (HVDC) power transmission line is provided. The fault detection is based on fault-induced travelling waves. The method comprises estimating an amplitude of fault-induced travelling waves at the fault location, and calculating a fault resistance (Rf) based on the estimated amplitude, an estimated pre-fault voltage at the fault location, and a surge impedance of the transmission line. The estimated fault amplitude and the estimated pre-fault voltage are calculated from voltage measurements performed at both ends of the transmission line. Further, a fault detection device is provided.

Abstract: An energy generation system includes a turbine, an electric generator, a step-up transformer, and a converter. The turbine is operable to extract energy from a fluid flow and convert the extracted energy into mechanical energy. The electric generator is operable to convert the mechanical energy from the turbine into AC electrical energy. The step-up transformer is operable to transfer the AC electrical energy at a lower voltage from the electric generator to a higher voltage. The converter is operable to convert the AC electrical energy at the higher voltage to DC electrical energy. The converter includes a converter leg for a phase of the AC electrical energy. The converter leg has an upper arm with a first plurality of sub-modules and a lower arm with a second plurality of sub-modules. Each sub-module is operable to function as a controlled voltage source.

Abstract: A system for producing electrical power based on wind energy is capable of predicting its power output. The system includes a set of wind turbine units, a first plurality of sensors each adapted to sense at least one wind characteristic at some of the wind turbine units, and a second plurality of sensors remotely located. At least one wind characteristic is estimated at the wind turbines not having one of the first plurality of sensors based on sensing by the first plurality of sensors and an estimate of changes in wind characteristic at wind turbine units caused by presence of other wind turbine units. The magnitude of electrical power production by the set of wind turbine units at at least one predefined point in time in the future is predicted based on the estimated wind characteristics and sensed wind characteristics.

Abstract: An improved method of fault detection in a high-voltage direct current (HVDC) power transmission line is provided. The fault detection is based on fault-induced travelling waves. The method comprises estimating an amplitude of fault-induced travelling waves at the fault location, and calculating a fault resistance (Rf) based on the estimated amplitude, an estimated pre-fault voltage at the fault location, and a surge impedance of the transmission line. The estimated fault amplitude and the estimated pre-fault voltage are calculated from voltage measurements performed at both ends of the transmission line. Further, a fault detection device is provided.

Abstract: The present invention discloses a coordinated control method for power distribution system with DC bus electrification scheme and apparatus thereof. The method comprises: detecting what kind of disturbances occurs, and at least one of following steps: restoring the voltages of the failed DC buses if power loss is detected on the DC buses due to temporary or permanent failures of upstream power supplies; controlling the voltage of the abnormal DC buses if overvoltage or under-voltage is detected on the DC buses due to internal or external disturbances; and supporting the voltages of the abnormal AC buses if overvoltage or under-voltage is detected on the AC buses due to internal or external disturbances. The methods and apparatus can further improve the fault-ride-through capability for power plant under external or internal disturbances, and facilitate smooth automatic switching process between two DC buses etc.

Abstract: An energy generation system includes a turbine, an electric generator, a step-up transformer, and a converter. The turbine is operable to extract energy from a fluid flow and convert the extracted energy into mechanical energy. The electric generator is operable to convert the mechanical energy from the turbine into AC electrical energy. The step-up transformer is operable to transfer the AC electrical energy at a lower voltage from the electric generator to a higher voltage. The converter is operable to convert the AC electrical energy at the higher voltage to DC electrical energy. The converter includes a converter leg for a phase of the AC electrical energy. The converter leg has an upper arm with a first plurality of sub-modules and a lower arm with a second plurality of sub-modules. Each sub-module is operable to function as a controlled voltage source.

Abstract: A power generation system includes at least one generator having at least two sets of stator windings, an active rectifier comprising power cell based modular converters associated with each set of generator windings. Each set of windings is connected to an AC voltage side of the associated active rectifier, with each active rectifier having a positive DC voltage output and a negative DC voltage output. The DC voltage outputs of active rectifiers are connected to each other in series. A medium voltage DC (MVDC) collection network comprises positive pole cables and negative pole cables, wherein each positive pole cable is connected to the positive DC voltage output of a first active rectifier and each negative pole cable is connected to the negative DC voltage output of a last active rectifier. A substation receives the negative and positive pole cables of the MVDC collection network for further transformation and transmission.

Abstract: Connection schemes for offshore power generation with an internal collection grid include a power generation system which includes a plurality of generator-rectifier subsystems. The scheme further includes a medium voltage DC (MVDC) collection network with positive pole cables and negative pole cables connected to the DC outputs of the generator-rectifier subsystems. At least one offshore substation includes a positive bus bar and a negative bus bar correspondingly connected to the positive pole cables and negative pole cables of the MVDC collection network and a plurality of main DC-DC converters. Each main DC-DC converter includes multiple modules connected to the MVDC bus bars and each module has a positive and a negative output such that the modules' outputs are serially connected to one another. The schemes may also include a high voltage DC (HVDC) transmission system connected to the modules' outputs and at least one DC/AC converter at an onshore substation.

Abstract: Apparatus and method for controlling power in an auxiliary power system of a thermal power plant having a generator and one or more auxiliary buses. The apparatus includes adjustable speed drives and capacitance sources for connection to the one or more auxiliary buses and sensors for measuring voltage and reactive power on the one or more auxiliary buses. A controller is operable to control the adjustable speed drives and the capacitance sources to control the power factor of the auxiliary power system, while providing steady state voltage regulation and dynamic voltage support.

Abstract: Multi-terminal HVDC systems and control methods therefore are disclosed. Methods for controlling multi-terminal HVDC systems having a plurality of converter stations may include receiving a plurality of measurements from a plurality of measurement units disposed on the HVDC system, identifying from the measurements a disruption within the HVDC system, monitoring the measurements to identify a steady-state disrupted condition for the HVDC system, calculating a new set point for at least one of the plurality of converter stations, which new set point may be based on the steady-state disrupted condition and the measurements, and transmitting the new set point to the at least one of the plurality of converter stations. In some examples, the HVDC systems may include an HVDC grid interconnecting the plurality of converter stations and a controller communicatively linked to the plurality of measurement units and the plurality of converter stations.

Abstract: Methodologies adjust a component failure rate for electric power network reliability analysis. A component may include subcomponents and the failure of each subcomponent may be feature dependent. Features are measurable or observable inputs, which can affect the life of one or more subcomponents. The failure rate of a particular component may be obtained according to its real conditions. The methodologies can be used to do condition-based reliability analysis for electric power networks, in order to obtain a maintenance/replacement/operation strategy.

Abstract: A systematic approach is presented for the development and implementation of cost-effective transmission asset maintenance strategies. The overall concept and methodology are based on transmission reliability and risk management and address the value of preventive maintenance activities. This may help electric network utilities conduct maintenance policy assessment, region-wide criticality analysis, and optimal maintenance resource allocation and task scheduling.

Abstract: A computer implemented method uses a database of detailed, comprehensive utility operating and financial information. The method comprises: (1) feature based matching or similarity based benchmark and focus group selection; (2) a performance assessment procedure comprising multi-perspective analysis; and (3) multi-attribute business profiling and performance improvement potential analysis. As part of the performance assessment step, data corresponding to different utilities in a selected benchmark group are compared with each other to find their strengths and weaknesses. Interpretation of these gaps provides the cause of such gaps. Composite ranking analysis is used so that a composite score of at least one utility business is obtained.

Abstract: Methodologies adjust a component failure rate for electric power network reliability analysis. A component may include subcomponents and the failure of each subcomponent may be feature dependent. Features are measurable or observable inputs, which can affect the life of one or more subcomponents. The failure rate of a particular component may be obtained according to its real conditions. The methodologies can be used to do condition-based reliability analysis for electric power networks, in order to obtain a maintenance/replacement/operation strategy.

Abstract: A systematic approach is presented for the development and implementation of cost-effective transmission asset maintenance strategies. The overall concept and methodology are based on transmission reliability and risk management and address the value of preventive maintenance activities. This may help electric network utilities conduct maintenance policy assessment, region-wide criticality analysis, and optimal maintenance resource allocation and task scheduling.