Abb Research Ltd.

Leonardo-Augusto Serpa

Antonio Coccia

Sami Pettersson

Gerardo Escobar

Francisco Canales

Ngai-Man Ho

Mikko Paakkinen

Alexandre Oudalov

Adrian Vasile Timbus

Yales De-Novaes

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

A method is disclosed for controlling single-phase DC/AC converters, along with a converter arrangement having at least two single-phase DC/AC converters. A controller is provided which can control the at least two single-phase DC/AC converters, and an isolation transformer, wherein outputs of the at least two single-phase DC/AC converters are cascade-connected with each other and an input of the isolation transformer. The controller is configured to control the at least two single-phase DC/AC converters to deliver power from their inputs to their outputs by turns.

Method for controlling single-phase DC/AC converters and converter arrangement

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.

Control method for single-phase grid-connected LCL inverter

An exemplary non-isolated DC-DC converter for a solar power plant, can be adapted to connect to a full-bridge inverter. The converter includes positive and negative input terminals, and positive and negative output terminals. A plurality of switches, diodes, inductors and capacitors are connected in a circuit configuration to the input and output terminals. A control means is connected to the circuit for controlling the switching of a first, second, and third switch between an open and closed state.

Growing community of inventors

Zurich, Switzerland

Leonardo-Augusto Serpa