Abstract: This patent discloses an active impedance-injection module for dynamic line balancing of a high-voltage (HV) transmission line. The impedance-injection module comprises a plurality of transformers each having a primary winding in series with a HV transmission line. Each transformer also has secondary windings, each connected to an individual electronic converter. The plurality of secondary windings are electrically isolated from the associated primary winding and extract power from the HV transmission line for operation of the converters and other circuits connected to the secondary windings. The active impedance-injection module is enabled to generate a controlled impedance, inductive or capacitive, to be impressed on the HV transmission line.

Abstract: Active impedance-injection module enabled for distributed power flow control of high-voltage (HV) transmission lines is disclosed. The module uses transformers with multi-turn primary windings, series-connected to high-voltage power lines, to dynamically control power flow on those power lines. The insertion of the transformer multi-turn primary is by cutting the line and splicing the two ends of the winding to the ends of the cut high-voltage transmission line. The secondary winding of the transformer is connected to a control circuit and a converter/inverter circuit that is able to generate inductive and capacitive impedance based on the status of the transmission line. The module operates by extracting power from the HV transmission line with the module floating at the HV transmission-line potential. High-voltage insulators are typically used to suspend the module from transmission towers, or intermediate support structures. It may also be directly suspended from the HV transmission line.

Abstract: Disclosed is a method for reducing the variation in voltage, due to Ferranti effect, using the impedance injection capability of distributed impedance injection modules. The Ferranti effect is an increase in voltage occurring at the receiving end of a long transmission line in comparison to the voltage at the sending end. This effect is more pronounced on longer lies and underground lines when the high-voltage power lines are energized with a very low load, when there is a change from a high load to a very light load, or the load is disconnected from the high-voltage power lines of the power grid. This effect creates a problem for voltage control at the distribution end of the power grid.

Abstract: A wind turbine is disclosed having a generator and rectifier and structured to provide direct current power that in one form is medium voltage direct current (MVDC). The wind turbine includes a crowbar circuit arranged to protect from a condition such as an overvoltage. The crowbar can be activated based on a voltage measurement or rate of change of voltage. A resistor can be coupled to the crowbar to absorb excess power provided by the generator during the overvoltage condition. Individual wind turbines in a wind farm can each have individual crow bars that can be activated based on local measurement of a voltage condition. In some forms the crowbar can be coupled with a transformer, for example coupled with a tertiary winding of a three winding transformer.

Abstract: A series injection device includes a power splitter coupled to two or more lines of an AC power system. The power splitter includes a coupling transformer for each phase of a single phase or polyphase AC circuit that includes the two or more lines. Each of the coupling transformers couples one of the phases of the two or more lines. The power splitter is configured to inject a first voltage of a first polarity into one or more of the two or more lines and inject a second voltage of a second polarity opposite the first polarity into at least one of the two or more lines via the same coupling transformers used to inject the first voltage. The first and the second voltages are controllable, and may or may not be independently variable.

Abstract: According to one aspect of the teachings herein, a controller communicatively couples to and advantageously exploits a distributed control network of an industrial plant by, for example, using information received over the distributed control network to predict the value of one or more electrical parameters of an electrical distribution grid of the industrial plant, and to generate and transmit converter control commands based on the predicted value(s). These converter control commands target one or more converters located within the electrical distribution grid, each converter having an Active Front End or AFE that allows the reactive power consumption of the converter to be adjusted via the converter control commands.

Abstract: Converter stations have real and reactive power set points initially determined as part of a main loadflow analysis routinely performed on the AC power system connected to the converter stations. Viable real and/or reactive power set points for the converter stations can be identified by calculating real and/or reactive power set point candidates for the converter stations before the main loadflow analysis is performed again on the AC power system. The power set point candidates are calculated based on information determined as part of a previous iteration of the main loadflow analysis on the AC power system. The power set point candidates which violate an operating constraint imposed on the AC power system are identified, and a region of valid power set points is defined for the converter stations that excludes the power set point candidates which violate an operating constraint imposed on the AC power system.

Abstract: A turbine-based energy generation system includes an electric generator and auxiliary load. A power system for the turbine-based energy generation system includes a main converter and an auxiliary converter. The main converter is operable to deliver power generated by the electric generator to a power collection system external to the turbine-based energy generation system when the main converter is coupled to the generator. The main converter is also operable to deliver power provided from the power collection system to the auxiliary converter when the main converter is decoupled from the generator. The auxiliary converter is operable to deliver power generated by the electric generator to the auxiliary load when the auxiliary converter is coupled to the generator. The auxiliary converter is also operable to deliver the power provided by the main converter from the power collection system to the auxiliary load when the auxiliary converter is decoupled from the generator.

Abstract: A fault in a DC power source, such as a battery string or a string of photovoltaic cells, is identified by detecting a change in an AC component of a residual current of the DC power source. In some embodiments, the DC power source is coupled to at least one DC bus and the methods further include generating an AC voltage on the at least one DC bus. For example, the DC power source may be coupled to a modulated DC bus of an uninterruptible power supply (UPS) system comprising an inverter having an input coupled to the DC bus. The inverter may be configured to generate an AC output voltage and the AC component has a frequency that is a harmonic of a fundamental frequency of the AC output voltage, such as a third harmonic of the fundamental frequency of the AC output voltage.

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: A turbine-based energy generation system includes an electric generator and auxiliary load. A power system for the turbine-based energy generation system includes a main converter and an auxiliary converter. The main converter is operable to deliver power generated by the electric generator to a power collection system external to the turbine-based energy generation system when the main converter is coupled to the generator. The main converter is also operable to deliver power provided from the power collection system to the auxiliary converter when the main converter is decoupled from the generator. The auxiliary converter is operable to deliver power generated by the electric generator to the auxiliary load when the auxiliary converter is coupled to the generator. The auxiliary converter is also operable to deliver the power provided by the main converter from the power collection system to the auxiliary load when the auxiliary converter is decoupled from the generator.

Abstract: Converter stations have real and reactive power set points initially determined as part of a main loadflow analysis routinely performed on the AC power system connected to the converter stations. Viable real and/or reactive power set points for the converter stations can be identified by calculating real and/or reactive power set point candidates for the converter stations before the main loadflow analysis is performed again on the AC power system. The power set point candidates are calculated based on information determined as part of a previous iteration of the main loadflow analysis on the AC power system. The power set point candidates which violate an operating constraint imposed on the AC power system are identified, and a region of valid power set points is defined for the converter stations that excludes the power set point candidates which violate an operating constraint imposed on the AC power system.

Abstract: A fault in a DC power source, such as a battery string or a string of photovoltaic cells, is identified by detecting a change in an AC component of a residual current of the DC power source. In some embodiments, the DC power source is coupled to at least one DC bus and he methods further include generating an AC voltage on the at least one DC bus. For example, the DC power source may be coupled to a modulated DC bus of an uninterruptible power supply (UPS) system comprising an inverter having an input coupled to the DC bus. The inverter may be configured to generate an AC output voltage and the AC component has a frequency that is a harmonic of a fundamental frequency of the AC output voltage, such as a third harmonic of the fundamental frequency of the AC output voltage.