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Sami Pettersson

Gerardo Escobar

Francisco Canales

Tero Viitanen

Mario Schweizer

Antonio Coccia

Ngai-Man Ho

Leonardo-Augusto Serpa

Ki-Bum Park

Daniel Christen

Alexandre Oudalov

Adrian Vasile Timbus

Frederick Kieferndorf

Gernot Riedel

Hemant Bishnoi

Mikko Paakkinen

Yales De-Novaes

A system and method for compensating a faulty switch in a multi-level flying capacitor converter includes a converter capacitor arranged in parallel to an input, a first and second converter switches arranged respectively between first and second ends of the converter capacitor, first and second bypass switches respectively arranged in parallel to the first and second converter switches, wherein operation includes detecting a faulty converter level that includes at least one of the first and second converter switches, discharging all capacitors arranged in parallel to the input of the multi-level converter, wherein all capacitors comprise the converter capacitors and an input capacitor; closing the first and second bypass switches of the faulty converter level; adapting a modulation of the converter switches of the other converter levels; and restarting the multi-level converter.

Method and a device for compensating a faulty switch in a multi-level flying capacitor converter

A flying capacitor switching cell-system includes at least two flying capacitor switching cells, wherein each of the cells comprises an arrangement of at least one semiconductor system, and wherein the cells are in parallel in an electrical circuit.

Flying capacitor switching cell-system

A protection circuit for a power converter with cascaded bipolar and/or unipolar semiconductors is provided. The protection circuit includes at least one comparator circuit which is adapted to monitor a voltage characteristic on a collector-emitter path of at least one semiconductor which is arranged in a polarity selection stage of the power converter and/or to monitor a voltage characteristic on at least one capacitor, which is arranged in the power converter. The at least one comparator circuit is further adapted to output an electrical signal, representing the voltage characteristic of the semiconductor and/or the at least one capacitor to at least one evaluation unit. The at least one evaluation unit is further adapted to evaluate the result from the at least one comparator circuit and to deactivate the semiconductors in case that the voltage characteristic of the semiconductors and/or the capacitors deviate from a predetermined threshold.

Protection scheme for power converters utilizing cascaded bipolar and unipolar power semiconductor devices

A converter circuit with short-circuit protection can include a plurality of phase legs having a series connection of normally-on switches, between voltage rails of a DC voltage link, a DC link capacitor, and AC voltage connection points between the normally-on switches. A phase-to-phase short-circuit protection circuit includes a parallel connection of a resistive component and a controllable switch. The phase-to-phase short-circuit protection circuit including a first terminal connected to an AC voltage connection point and a second terminal forms an input or an output of the converter circuit; and a controllable switch is connected in series with the DC link capacitor. Upon lack of control of the normally-on switches the controllable switch of the at least one phase-to-phase short-circuit protection circuit and the controllable switch of the phase leg short-circuit protection circuit are adapted to be controlled to a non-conductive state.

Converter circuit

An exemplary method and apparatus for detecting islanding conditions of a distributed grid are disclosed, wherein transfer of power through a power electrical unit is controlled on the basis of a control reference. The apparatus includes a first stage and a second stage performing a respective portion of the method. The first stage injects a reactive component to the control reference, and, for at least one electrical quantity of the grid, determines a change in the quantity induced by the injected component, and determines, on the basis of the change in the electrical quantity, whether to move to the second stage of the method. The second stage, for at least one electrical quantity of the grid, determines a value of the electrical quantity, forms a positive feedback term using at the determined value adding a positive feedback term to the control reference, determines a change in an electrical quantity induced by the feedback term, and determines islanding condition on the basis of the change in the quantity induced by the feedback term.

Method and apparatus for detecting islanding conditions of a distributed grid

An exemplary method and an apparatus implementing the method for an arrangement having a three-phase, multi-level inverter, an output LCL-filter connecting the inverter to a grid, and a virtual-ground connection between the LCL-filter and the neutral point of the DC-link. The method includes determining a zero-sequence component of an LCL-filter inverter-side current, calculating a zero-sequence damping and balancing voltage term based on the LCL-filter inverter-side current zero-sequence component and voltages over the two halves of the DC-link, and adding the zero-sequence damping and voltage balancing term to the output voltage reference.

Method and apparatus for zero-sequence damping and voltage balancing

A method and an apparatus for controlling a grid-connected converter which includes a boost converter, a buck converter, and a current source inverter having an output CL filter. An input of the buck converter input is connected to an output of the boost converter, and an input of the current source inverter is connected to an output of the buck converter. The method includes controlling a boost converter input voltage, controlling a boost converter output voltage through control of a buck converter output voltage, and controlling the current source inverter to produce an AC current from the buck converter output voltage. The apparatus implements the method.

Method and apparatus for controlling a grid-connected converter

An exemplary method and arrangement for estimating the frequency and the positive sequence of a fundamental component of a measured three-phase voltage are disclosed (&#x3bd;). The method includes measuring the three-phase voltage (&#x3bd;), calculating estimates of a fundamental frequency voltage component ({circumflex over (&#x3bd;)}) and a difference ({circumflex over (&#x3c6;)}) between positive and negative sequence components of the fundamental frequency voltage from an error ({tilde over (&#x3bd;)}) between the measured three-phase voltage (&#x3bd;) and at least one of the calculated estimates of the fundamental frequency voltage component ({circumflex over (&#x3bd;)}) and from an estimate of the angular frequency ({circumflex over (&#x3c9;)}) of the fundamental frequency voltage component, wherein the estimate of the angular frequency ({circumflex over (&#x3c9;)}) of the fundamental frequency voltage component is calculated from at lest one of the estimated differences ({circumflex over (&#x3c6;)}) and from the error ({tilde over (&#x3bd;)}) between the measured three-phase voltage and at least one of the calculated estimates of the fundamental frequency voltage component.

Method and arrangement for estimating angular frequency

A method of controlling the grid-side current of a single-phase grid-connected converter having an LCL filter connected between the output of the converter and the grid includes measuring a grid voltage and at least one signal in a group of signals consisting of a grid-side current, a converter-side current and a capacitor voltage, estimating the fundamental component of the grid voltage, forming a grid-side current reference, a converter-side current reference and a capacitor voltage reference for the grid-side current of the LCL filter, forming estimates for the non-measured signals in the group of signals, forming a grid-side current difference term, a converter-side current difference term and a capacitor voltage difference term, and controlling the output voltage of the converter based on the grid voltage, a formed injection term and a formed estimate of the harmonic distortion term to produce a grid side current corresponding to the current reference.

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Wettingen, Switzerland

Sami Pettersson