Abstract: An arrangement to determine a cell capacitor voltage value of a cell of a multi-cell power converter includes the cell and a control unit. The cell itself includes four power electronic valves interconnected as a full-bridge converter having a first and a second phase leg, where each phase leg includes a series-connection of two of the four power electronic valves and where the connection point between the two power electronic valves of each phase leg is externally connectable, a cell capacitor being connected in parallel to the first and the second phase legs, and four gate units, each being connected to a corresponding one of the power electronic valves as well as to the control unit.

Abstract: A voltage source converter including a string of series connected active semiconducting elements. The converter includes in case of an active semiconducting element failure a calculation element configured to calculate an operation dc voltage including a sum of dc ratings of each remaining active semiconducting element in the string, and a regulator configured to regulate the converter to assume the operation dc voltage over the converter.

Abstract: An arrangement for exchanging power with a three-phase electric power network comprises a Voltage Source Converter having three phase legs with each a series connection of switching cells. The three phase legs are interconnected by forming a delta-connection. The arrangement also includes a control unit configured to calculate a value for amplitude and phase position for a zero-sequence current for which, when circulated in the delta-connection circuit of the three phase legs, the balance of the total direct voltage of each of the three phase legs with respect to the other two phase legs is restored will there be an unbalance and control the semiconductor devices of switching cells of the phase legs to add such a zero-sequence current to the currents of each phase leg of the converter.

Abstract: Power exchanging arrangement, in shunt connection, with a three-phase electric power network including on one hand for each said phase a reactive impedance element and a Voltage Source Converter connected in series with said element, and on the other hand a control unit configured to control semiconductor devices of turn-off type of said converter for generating a voltage with a fundamental frequency being equal to the fundamental frequency of the voltage of the respective said phase and by that control a flow of reactive power between said arrangement and the respective phase of said electric power network. Each Voltage Source Converter includes a series connection of switching cells in the form of so-called H-bridges including two switching elements connected in parallel and each having at least two semiconductor assemblies connected in series. Each switching cell further comprises at least one energy storing capacitor connected in parallel with said switching elements.

Abstract: An arrangement for exchanging power, in shunt connection, with a three-phase electric power network includes a Voltage Source Converter having at least three phase legs with each a series connection of switching cells. Each switching cell has at least two semiconductor assemblies connected in series and having each a semiconductor device of turn-off- type and a rectifying element connected in anti-parallel therewith and at least one energy storing capacitor. A control unit is configured to control the semiconductor devices of each switching cell and to deliver a voltage across the terminals thereof being zero or U, in which U is the voltage across the capacitor. The control unit is also configured to calculate a value for amplitude and phase position for a second negative sequence-current or a zero-sequence voltage or a value of a dc current.

Abstract: An arrangement for exchanging power with a three-phase electric power network includes a Voltage Source Converter having three phase legs with each a series connection of switching cells. The three phase legs are interconnected in a neutral point by forming a wye-connection. The arrangement also includes a device connected to the neutral point of the converter and configured to provide a current path for a zero-sequence current. A control unit is configured to calculate a value for amplitude and phase position for a zero-sequence current for which, when added to said three phase legs upon generation of a negative-sequence current, the resulting energy stored in energy storing capacitors in each phase leg will be constant and to control semiconductor devices of said switching cells to add such a zero-sequence current to the currents of each phase leg of the converter.

Abstract: Voltage source converter based on a chain-link cell topology including one or more phases, each of the phases having one or more series-connected chain-link cell modules connected to each other. The output voltage of the voltage source converter is controlled by control signals applied to the series-connected chain-link cell modules. In case of failure of a chain-link cell module, that module is controlled, by the control signals, such that zero output voltage is provided at its output voltage AC terminal.

Abstract: An arrangement to determine a cell capacitor voltage value of a cell of a multi-cell power converter includes the cell and a control unit. The cell itself includes four power electronic valves interconnected as a full-bridge converter having a first and a second phase leg, where each phase leg includes a series-connection of two of the four power electronic valves and where the connection point between the two power electronic valves of each phase leg is externally connectable, a cell capacitor being connected in parallel to the first and the second phase legs, and four gate units, each being connected to a corresponding one of the power electronic valves as well as to the control unit.

Abstract: A voltage source converter including a string of series connected active semiconducting elements. The converter includes in case of an active semiconducting element failure a calculation element configured to calculate an operation dc voltage including a sum of dc ratings of each remaining active semiconducting element in the string, and a regulator configured to regulate the converter to assume the operation dc voltage over the converter.

Abstract: A device for compensation of the reactive power consumption of an industrial load, preferably an electric arc furnace or a plant for rolling of metallic materials, supplied from a three-phase (a, b, c) electric ac network, comprises a first compensation device for controllable consumption of reactive power and a second compensation device for generation of reactive power. The first compensation device comprises an inductor connected in series with a semiconductor connection controllable in dependence on a control order (.alpha.ref) supplied thereto. Control equipment is supplied with measured values of voltage (Ua, Ub, Uc) and current (Ia, Ib, Ic), respectively, at the load. The control equipment comprises devices for determination of the instantaneous consumption of active and reactive power by the load, and a control device which forms the control signal to the first compensation device in dependence on the consumption of reactive power and active power by the load.