Abstract: Disclosed is a DC power supply device that includes: a transformer having a primary side and a secondary side; a diode rectifier connected at its input side to the secondary side of the transformer; an inverter connected at its output side to the secondary side of the transformer; and a controller. The inverter is controlled by the controller to generate reactive power and/or harmonics onto the secondary side of the transformer so as to regulate the DC voltage at the output side of the diode rectifier to a target value. The controller receives at its input side at least one DC signal outputted by the diode rectifier and uses the at least one DC signal to control the inverter.

Abstract: A power transmission network includes converters interconnected via electrical elements, at least one power flow router, and a controller. Each power flow router being operatively connected to the electrical elements, each power flow router configured to selectively control current flow in the electrical elements so as to direct power between two or more of the plurality of converters.

Abstract: Fault protection of a voltage source converter is provided. An apparatus has a chain-link circuit in series with a director switch. The chain-link circuit includes cells including an energy storage element and cell switching elements connected with anti-parallel diodes. Each cell switching element has a cell switching element controller. The director switch includes director switch units, each having a director switching element and a director switch unit controller. Each cell switching element controller monitors for a fault current and turns-off its associated cell switching element and reports a fault event to a fault controller. Each director switch unit controller monitors for a fault current and reports a fault event to the fault controller but the director switch unit control keeps its associated director switching element turned-on. The fault controller monitors for reports of fault events to order the cell switching elements of at least some of the cells to turn-off.

Abstract: A far-end power converter within a DC transmission network that includes a near-end power converter and at least one far-end power converter interconnected by portions of transmission medium. A method includes: establishing a linear time-invariant model of the transmission medium; determining a response characteristic of the time-invariant model; measuring an output operating property of the transmission medium at the near-end power converter; identifying one far-end power converter as being of interest; deriving a corresponding input operating property of the transmission medium at the far-end power converter of interest by applying an inverse of the response characteristic of the time-invariant model to the measured output operating property of the transmission medium at the near-end power converter; and comparing the derived input operating property with a fault characteristic to determine whether there is a fault on the far-end power converter of interest.

Abstract: Fault protection of a voltage source converter is provided. An apparatus has a chain-link circuit in series with a director switch. The chain-link circuit includes cells including an energy storage element and cell switching elements connected with anti-parallel diodes. Each cell switching element has a cell switching element controller. The director switch includes director switch units, each having a director switching element and a director switch unit controller. Each cell switching element controller monitors for a fault current and turns-off its associated cell switching element and reports a fault event to a fault controller. Each director switch unit controller monitors for a fault current and reports a fault event to the fault controller but the director switch unit control keeps its associated director switching element turned-on. The fault controller monitors for reports of fault events to order the cell switching elements of at least some of the cells to turn-off.

Abstract: A voltage source converter includes DC terminals for connection to a DC network, a plurality of converter limbs between the DC terminals, and a controller. Each converter limb includes first and second limb portions separated by a respective AC terminal, the AC terminal of each converter limb connecting to a multi-phase AC network. Each limb portion extends between a corresponding DC terminal and AC terminal. Each limb portion including a valve having switching element(s) and energy storage device(s), the switching element being switchable to selectively insert the energy storage device into the limb portion and bypass the energy storage device to control a voltage across that valve. The controller is programmed to control the switching of valves to form a current circulation path including the limb portions corresponding to the selected valves, the AC phases connected to the limb portions corresponding to the selected valves, and the DC network.

Abstract: A voltage source converter including a plurality of terminals, a plurality of switching elements, a plurality of energy storage devices connected between the plurality of terminals, and a controller. Each energy storage device stores and releases energy to provide a voltage, and the plurality of switching elements are arranged to be switchable to control flow of current through each energy storage device. The controller is programmed to operate in an energy regulation mode to regulate energy.

Abstract: In the field of high voltage direct current power transmission networks, a method of controlling a converter that includes at least one converter limb which corresponds to a respective phase of the converter, is described. The method includes obtaining a respective AC current demand phase waveform for each converter limb which the corresponding converter limb is required to track, and a DC current demand which each converter limb is also required to track. The method further determining a limb portion current for each limb portion that the limb portion must contribute to track the corresponding required AC current demand phase waveform and the required DC current demand, and providing a limb portion voltage source for each limb portion to achieve the corresponding limb portion current. The method carrying out mathematical optimization to determine one or more optimal limb portion currents and/or provide optimal limb portion voltage sources.

Abstract: A method of controlling a voltage source converter including a converter limb corresponding to a respective phase of the converter, each converter limb extending between first and second DC terminals and including first and second limb portions separated by an AC terminal and each limb portion including a chain-link converter which is operable to provide a stepped variable voltage source, includes the steps of obtaining a AC current demand phase waveform and a DC current demand for each corresponding converter limb is configured to track, and carrying out mathematical optimization to determine an optimal limb portion current for each limb portion must contribute to track the corresponding required AC current demand phase waveform and the required DC current demand while minimising current conduction losses within each limb portion and additionally managing the energy stored by each chain-link converter.

Abstract: A voltage source converter comprises a converter limb including first and second DC terminals for connection to a DC network. Each converter limb includes first and second limb portions which are separated by an AC terminal for connection to an AC network. Each limb portion includes a switching element connected with a chain-link converter that is operable to provide variable voltage. The voltage source converter includes a control unit to switch the switching element in each of the first and second limb portions between conducting and non-conducting configurations to selectively switch the corresponding chain-link converter, each switching element while in its non-conducting configuration transitions between a non-voltage supporting state and a voltage supporting state; and operate each chain-link converter while switched out of circuit to generate a varying voltage waveform to reduce the voltage range the corresponding switching element is exposed to in its voltage supporting state.

Abstract: A method of identifying a faulty sub-module of a chain-link converter is provided, wherein the chain-link converter includes a plurality of sub-modules with each sub-module including at least one switching element and an energy storage device which together are selectively operable to provide a voltage source. The method comprises the steps of: measuring a switching characteristic of each sub-module of the chain-link converter; establishing a switching characteristic signature of the chain-link converter; and identifying the or each sub-module with a switching characteristic that deviates from the switching characteristic signature as being a faulty sub-module.

Abstract: A voltage source converter for interconnecting first and second electrical networks, including first and second terminals for connection to the first electrical network, and a primary converter limb extending between the first and second terminals including first and second primary limb portions separated by a third terminal connectable to the second electrical network. The converter further including a second chain-link converter connected to the third terminal and a control unit configured to selectively operate one or more chain-link modules to generate a discontinuous pulse width modulation voltage waveform. The converter further including a controller configured to selectively operate each chain-link converter to control the configuration of a discontinuous pulse width modulation voltage waveform at the third terminal.

Abstract: A synthetic test circuit, comprising: a device under test including a chain-link converter under test, comprising a plurality of test modules, each test module including module switches connected with an energy storage device; a terminal connected to the device under test; at least one injection circuit operably connected to the terminal, the injection circuit including a source, the source including a source chain-link converter, which includes a plurality of source modules, each source module including a plurality of module switches connected with at least one energy storage device; a controller being configured to operate each source module to selectively bypass the corresponding energy storage device and insert the corresponding energy storage device into the corresponding source chain-link converter so as to generate a voltage across the source chain-link converter and thereby operate the injection circuit to inject a current waveform and/or a voltage waveform into the chain-link converter under test.

Abstract: A synthetic test circuit, for performing an electrical test on a device under test, is provided. The circuit includes a terminal connectable to the device under test; a voltage injection circuit-operably connected to the terminal, the voltage injection circuit including a voltage source, the voltage source including a chain-link converter, the chain-link converter including a plurality of modules, each module including a plurality of module switches connected with at least one energy storage device; and a controller-configured to operate each module of the voltage injection circuit to selectively bypass the or each corresponding energy storage device and insert the or each corresponding energy storage device into the chain-link converter so as to generate a voltage across the chain-link converter and thereby operate the voltage injection circuit to inject a unidirectional voltage waveform into the device under test.

Abstract: A method is provided for controlling a converter including at least one converter limb corresponding to a respective phase of the converter, the or each converter limb extending between first and second DC terminals and including first and second limb portions separated by an AC terminal, each limb portion including a converter arm, at least one of the limb portions including at least one director arm, the or each director arm including a director switch. The method comprises the steps of obtaining a respective AC current demand phase waveform for the or each converter limb, and a DC current demand, both of which the or each converter limb is required to track; determining a limb portion current; timing the current ramp profile of the determined director arm current for the director arm or the one of the director arms; and providing a limb portion voltage source for each limb portion.

Abstract: A voltage source converter, for interconnecting electrical networks, comprises a converter structure which includes a terminal for connection to the first electrical network and a terminal for connection to the second electrical network. The converter structure also includes at least one module that is connected between the terminals. The module includes at least one energy storage device and at least one switching element. The energy storage element and switching element are operable to selectively provide a voltage source. The converter structure still further includes an integrated passive fault current limiter that is configured to present a first impedance to a normal current flowing in the voltage source converter during normal operation of the voltage source converter, and is configured to present a second impedance to a fault current flowing in the voltage source converter during a fault condition. The first impedance is lower than the second impedance.

Abstract: A method of identifying a faulty sub-module of a chain-link converter is provided, wherein the chain-link converter includes a plurality of sub-modules with each sub-module including at least one switching element and an energy storage device which together are selectively operable to provide a voltage source. The method comprises the steps of: measuring a switching characteristic of each sub-module of the chain-link converter; establishing a switching characteristic signature of the chain-link converter; and identifying the or each sub-module with a switching characteristic that deviates from the switching characteristic signature as being a faulty sub-module.

Abstract: A voltage source converter for interconnecting first and second electrical networks, including first and second terminals for connection to the first electrical network, and a primary converter limb extending between the first and second terminals including first and second primary limb portions separated by a third terminal connectable to the second electrical network. The converter further including a second chain-link converter connected to the third terminal and a control unit configured to selectively operate one or more chain-link modules to generate a discontinuous pulse width modulation voltage waveform. The converter further including a controller configured to selectively operate each chain-link converter to control the configuration of a discontinuous pulse width modulation voltage waveform at the third terminal.

Abstract: In the field of high voltage direct current (HVDC) power transmission, a converter comprises three converter limbs, each corresponding to a respective phase of the converter, each extending between first and second DC terminals and each including first and second limb portions separated by an AC terminal. Each limb portion that is operable to provide a stepped variable voltage source. The converter also includes a first controller that is programmed to selectively operate for one converter limb at a time the chain-link converter in each limb portion thereof to simultaneously adopt a current-conducting configuration and thereby define a fully-conducting converter limb to sequentially route via each said fully-conducting converter limb a DC current demand (IDC) between the first and second DC terminals.

Abstract: In the field of high voltage direct current power transmission networks, a method of controlling a converter that includes at least one converter limb which corresponds to a respective phase of the converter, is described. The method includes obtaining a respective AC current demand phase waveform for each converter limb which the corresponding converter limb is required to track, and a DC current demand which each converter limb is also required to track. The method further determining a limb portion current for each limb portion that the limb portion must contribute to track the corresponding required AC current demand phase waveform and the required DC current demand, and providing a limb portion voltage source for each limb portion to achieve the corresponding limb portion current. The method carrying out mathematical optimization to determine one or more optimal limb portion currents and/or provide optimal limb portion voltage sources.