A method of operating an electric vehicle charging apparatus for a vehicle to grid interface comprising a first full bridge converter configured to convert a grid supply to a DC link and a primary full bridge converter connected to the DC link and configured to provide an output alternating current for use in vehicle charging. The method includes detecting a charging power requirement for a vehicle; determining a required voltage for the DC link to enable the converter to supply power for satisfying the charging power requirement when operating at full duty cycle; operating the primary full bridge converter at full duty cycle; controlling the voltage of the DC link to the required voltage.

Method for determining parameter of a passive impedance adapter applicable to VSC-HVDC, including: S1. obtaining VSC-HVDC impedance and VSC-HVDC impedance curve X(f) based on VSC-HVDC impedance; S2. estimating upper limit value of the main capacitor in the passive impedance adapter; S3. calculating adapter parameter curve X.sub.adapter(f); S4. determining value of the main capacitor and varying value of the main resistor until min[X(f)−X.sub.adapter(f)] is maximized; determining whether min[X(f)−X.sub.adapter(f)]>k holds; S5. If min[X(f)−X.sub.adapter(f)]>k does not hold, increasing the value of the main capacitor and performing steps S2-S4 until min[X(f)−X.sub.adapter(f)]>k holds when the value of the main capacitor is within the range of the value of the main capacitor, storing the parameters in an available parameter set; S6. reducing the value of the main capacitor, and storing the parameters when min[X(f)−X.sub.adapter(f)]>k holds in the available parameter set; S7. selecting the available parameters from the available parameter set.

A power margin tracking control method and system for a multi-terminal high-voltage direct current converter station are provided. A power adjustment factor is introduced on the basis of a droop coefficient, to realize a self-adaptive regulation of a converter station operation mode to a real-time fluctuation of a wind and solar power. In this way, the system operation stability and the power fluctuation allocation capability in a grid-connected system are improved. Furthermore, a DC voltage deviation in the multi-terminal high-voltage direct current grid is reduced.

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.

A converter station, for a bipole power transmission scheme, includes a first voltage source converter and a second source converter. Each converters have a first terminal as transmission conduit and a second terminal as a return conduit. The second terminal of the return conduit of the first converter is electrically connected to the first terminal of the transmission conduit of the second converter as being a same terminal. Both voltage source converters also includes at least one converter limb which extends between the first and second terminals of each converters. The or each converter limb includes first and second limb portions that are separated by a corresponding first and second AC terminal which is for connection to a respective phase of a first or second AC network.

There is provided a switching valve for a voltage source converter. The switching valve comprises a plurality of modules, each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a controller configured to selectively control the switching of the switching elements to select one or more of the modules to contribute a or a respective voltage to a switching valve voltage, wherein the controller is configured to selectively carry out a module selection by: assigning each module with a respective address in an address queue; in a respective one of a plurality of sampling events, selecting one or more voltage contributing modules in order of its assigned address in the address queue; and between different sampling events, changing the order of selecting the or each voltage contributing module based on its assigned address in the address queue.

A power margin tracking control method and system for a multi-terminal high-voltage direct current converter station are provided. A power adjustment factor is introduced on the basis of a droop coefficient, to realize a self-adaptive regulation of a converter station operation mode to a real-time fluctuation of a wind and solar power. In this way, the system operation stability and the power fluctuation allocation capability in a grid-connected system are improved. Furthermore, a DC voltage deviation in the multi-terminal high-voltage direct current grid is reduced.

The disclosure relates to a line commutated converter, LCC, for a high-voltage direct current, HVDC, power converter. The LCC comprises at least one bridge circuit for connection to at least one terminal of a DC system. Each bridge circuit comprises at least two arms, and each arm is associated with a phase of an AC system. Each arm comprises one or more upper thyristor valves and one or more lower thyristor valves connected in series, and a branch extending from between the upper and lower thyristor valves. Each arm further comprises a parallel capacitor module comprising at least one parallel capacitor being connected in parallel between at least one pair of branches comprising a first branch and a second branch wherein during commutation of a flow of current in the first branch to a flow of current in the second branch, the at least one parallel capacitor is configured to discharge current in to the second branch in the same direction as the flow of current in the second branch.

A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.

A method of operating an electric vehicle charging apparatus for a vehicle to grid interface comprising a first full bridge converter configured to convert a grid supply to a DC link and a primary full bridge converter connected to the DC link and configured to provide an output alternating current for use in vehicle charging. The method includes detecting a charging power requirement for a vehicle; determining a required voltage for the DC link to enable the converter to supply power for satisfying the charging power requirement when operating at full duty cycle; operating the primary full bridge converter at full duty cycle; controlling the voltage of the DC link to the required voltage.