Each cell of a cell assembly for a converter may include: first and second terminals, switching elements, and a capacitor. The cells are connected in series such that, for each pair of neighbouring cells, the first terminal of a first cell is connected to the second terminal of a second cell. Each cell includes a bypass connected to the first and second terminals that bypasses switching elements in a short circuit configuration and does not bypass the switching elements in an open circuit configuration. Each cell has a cell controller providing control signals to the sw itching elements to connect the capacitor to the first and second terminals or to bypass the capacitor. The cell controller provides a control signal to the bypass unit of neighbouring cells to change its configuration between the short circuit and open circuit configurations.

A power converter includes two arms for each phase between DC terminals, and each arm is formed by connecting a plurality of converter cells in series. A control device includes an arm voltage command generation unit which generates, for each arm, an arm voltage command for the plurality of converter cells. The arm voltage command is generated by superimposing a zero-phase-sequence voltage command having a frequency component that is three times an AC fundamental frequency. Phase adjustment of the zero-phase-sequence voltage command is performed on the basis of voltage of a DC capacitor in the converter cell and the arm voltage command.

One or more systems, devices, and/or system-implemented methods are provided that can facilitate provision of varying AC output voltage or DC output voltage, including selectively separately providing a positive voltage output, a negative voltage output and no voltage output. A device can comprise a battery cell, and a controller connected to the battery cell and that varies output from the battery cell, wherein the controller is configured to cause the battery cell to selectively separately provide negative output voltage, positive output voltage and no output voltage. A method can comprise varying output polarity from a multi-cell battery cluster and selectively providing one or both of alternating current (AC) voltage output or direct current (DC) voltage output from the multi-cell battery cluster due to the varying of the output polarity.

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.

The application relates to an electric converter for converting AC or DC input into an electric AC or DC output. A swap circuit with controllable electric switches serves to selectively swap connection of a plurality of DC power banks (DCBs) between an input terminal and an output terminal, thus selectively connecting the DCBs to an electric source or an electric load. The DCBs are formed as series of interconnected submodules (SMs) each having electric energy storage elements (ESEs) and a switching circuit for selectively by-passing or connecting the ESEs. By properly controlling the swap circuit and the switching of the SMs, the converter can be used for DC-AC, DC-DC, AC-DC, or AC-AC conversion, allowing multilevel output.

A voltage source converter as well as a method and computer program product for controlling the converter. The converter includes at least one phase leg connected between a first DC terminal having a first voltage and a second DC terminal having a second voltage, the phase leg including an upper arm and a lower arm with cells, where a junction between the arms is connected to a corresponding AC terminal. The converter also includes a control unit configured to control the cells to output a train of pulses of trapezoidal shape where the generation of a first control signal for a first cell used to initiate a transition between two levels of a pulse coincides with the decision that a transition is to be made.

A power converter includes at least one arm having a plurality of converter cells cascaded to each other. Each of the converter cells includes a pair of input/output terminals, a plurality of switching elements, and a power storage element. The power storage element is electrically connected to the input/output terminals through the switching elements. A control device generates a control signal for controlling on and off of the switching elements of each converter cell. The control device generates the control signal by pulse width modulation control based on a modulation command signal including an AC component having a fundamental frequency and corresponding to a command value of an output voltage between the input/output terminals, in each converter cell, such that a harmonic component included in the output voltage and having a predetermined frequency that is an integer multiple of the fundamental frequency is suppressed.

The present disclosure relates to the field of electric power system, and more particularly to a topology of a series-connected MMC with a small number of modules, where the topology is composed of a three-phase bridge circuit, half-bridge valve strings, a three-phase filter inductor, and a three-phase grid frequency transformer. The topology of a series-connected MMC with a small number of modules in the present disclosure needs only two half-bridge valve strings, thus greatly reducing the number of the submodules as compared with the conventional MMC structure. When achieving the same high DC voltage output, the present disclosure can improve the power density of the MMC, realize stable three-phase AC output voltage, and further achieve balance of capacitor voltages in the two half-bridge valve strings. Compared to the conventional MMC topology, the topology in the present disclosure can reduce the number of submodules by nearly 2/3, and has a greater AC-DC voltage transfer ratio, thus reducing the cost of the MMC converter, reducing the device size, and improving the power density.

An AC to DC conversion device has first and second AC input terminals arranged to be coupled respectively to first and second terminals of a phase of an AC current generator, an H-bridge rectification device comprising two pairs of diodes, each pair being coupled to a respective one of the AC terminals to produce a DC output comprising a rectified back EMF waveform, and a waveform generator. The waveform generator comprises an output coupled to the DC output of the H-bridge rectification device, and is configured to input a unidirectional waveform to the DC output having the same magnitude and fundamental frequency as the rectified back EMF, phase shifted by a predetermined angle relative to the rectified back EMF waveform.

A power supporting arrangement includes a DC network having a first DC line with a first DC potential, a second DC line with a second DC potential, and an energy storage system that includes a first energy storage unit connected in a branch between the first and the second DC lines. A first group of phase arms is connected in a wye-configuration between the power grid and the first DC line and a second group of phase arms connected in a wye-configuration between the power grid and the second DC line. The first and second groups of phase arms are controllable as a voltage source converter. A third group of phase arms is connected to the power grid in a wye-configuration. The third group of phase arms have a neutral point and being controllable to support the power grid with reactive power.