Abstract: In the field of chain-link modules for voltage source converters, there is a need for an improved chain-link module. A chain-link module, for connection in series with other chain-link modules to form a chain-link converter selectively operable to provide a stepped variable voltage source within a voltage source converter, includes at least one pair of series-connected switching elements that are connected in parallel with a number of series-connected energy storage devices. Each energy storage device has an auxiliary power supply unit connected in parallel therewith to source energy therefrom for supply to an auxiliary chain-link module control circuit. The chain-link module also includes a modulation controller which is interconnected between each auxiliary power supply unit and the auxiliary chain-link module control circuit. The modulation controller is configured to modulate the proportion of energy supplied to the auxiliary chain-link module control circuit by each auxiliary power supply unit.

Abstract: In the field of chain-link modules for voltage source converters, there is a need for an improved chain-link module. A chain-link module, for connection in series with other chain-link modules to form a chain-link converter selectively operable to provide a stepped variable voltage source within a voltage source converter, includes at least one pair of series-connected switching elements that are connected in parallel with a number of series-connected energy storage devices. Each energy storage device has an auxiliary power supply unit connected in parallel therewith to source energy therefrom for supply to an auxiliary chain-link module control circuit. The chain-link module also includes a modulation controller which is interconnected between each auxiliary power supply unit and the auxiliary chain-link module control circuit. The modulation controller is configured to modulate the proportion of energy supplied to the auxiliary chain-link module control circuit by each auxiliary power supply unit.

Abstract: This application describes methods and apparatus for achieving voltage balancing of clamp capacitors of director switch units of a voltage source converter (VSC). An arm or director switch may be formed from a number of director switch units connected in series, each director switch unit having a semiconductor switching element such as an IGBT. Typically a clamp capacitor may be connected across the IGBT. In some arrangements a floating power supply may draw power from the clamp capacitor to provide power for the director switch unit. In the present application the director switch unit is operable in a voltage balancing mode such that the power drawn from the clamp capacitor varies based on the voltage across the clamp capacitor. In this way the power demand for power drawn from the clamp capacitor may have the characteristic of a resistive load.

Abstract: A module for use in a voltage source converter includes: first and second terminals; an energy storage device; at least one switching element to switch the energy storage device into or out of circuit with the terminals to selectively provide a voltage source; and a voltage-limiting component and/or a resistive element. The switching element(s) are switchable to selectively form a current path that passes through the voltage-limiting component and/or the resistive element and are further switchable to selectively switch the energy storage device into or out of circuit with the voltage-limiting component and/or the resistive element. The module includes electrical blocks including first and second pairs of electrical blocks connected in parallel with the energy storage device in a full-bridge arrangement. Each of the electrical blocks include a switching element, and one of the electrical blocks includes the voltage-limiting component and/or the resistive element.