Aspects are described for line frequency commutated voltage source converters for multiphase modular multilevel converters. A voltage source converter (VSC) capacitor voltage of a multiphase VSC of a multiphase power converter can be identified. The multiphase VSC can include a half-bridge circuit for each phase of the multiphase power converter. A circuit parameter can be identified and utilized to determine an arm voltage of an arm of a branch of the multiphase converter. Switch control signals can be generated to insert or bypass the VSC capacitor for the arm of the branch of the multiphase converter device, based at least in part on a comparison between the arm voltage and the VSC capacitor voltage.

Power converters can include a plurality of switching devices and a combination of one or more inductors and one or more flying capacitors. Both boost and buck converters may employ such topologies, and can achieve high efficiency and small size in at least some applications, including those with high conversion ratios. A control circuit can generate a first pair of complementary gate drive signals to drive a first complementary switch pairs and a second pair of complementary gate drive signals to drive a second complementary switch pair. The control circuit can vary a phase shift between the first pair of complementary gate drive signals and the second pair of complementary gate drive signals to regulate the flying capacitor voltage.

A first capacitor and a second capacitor are connected in series through a neutral point on the DC side of an inverter. A first converter receives an input voltage from a power source and outputs a first DC voltage to the first capacitor. A second converter receives a common input voltage and outputs a second DC voltage to the second capacitor. A control circuit controls the first converter such that the first DC voltage is controlled in accordance with a preset first voltage command value and controls the second converter such that the second DC voltage is controlled in accordance with a second voltage command value set equivalent to the first voltage command value.

A power conversion device includes a power conversion circuit unit including a plurality of leg circuits. Each of the leg circuits includes a plurality of converter cells each having a capacitor and connected in series to each other. Each of the plurality of converter cells is a first converter cell including at least two switching elements or a second converter cell including at least four switching elements. The power conversion device further includes a control device. The control device operates the plurality of the first converter cells that are controlled not based on a circulating current circulating between the plurality of leg circuits as a voltage source that outputs a circulating voltage in a circulation circuit indicating a closed circuit that does not include a DC circuit and an AC circuit, and operates the plurality of the second converter cells to control the circulating current in the circulation circuit.

A modulator for a flying-capacitor type multilevel converter receives, at an input, a time-variant reference signal and provides, at an output, a sequence of target levels, to provide switching signals for switching between discrete output levels of the multilevel converter according to the shape of the reference signal. The modulator determines a critical level as an intermediate output level of the multilevel converter which is closest to the level of the reference signal; and outputs only target levels corresponding to output levels different from the critical level.

A voltage balancing circuit for a double-boost DC/DC converter includes a split DC-link having a first midpoint, outer directional devices and inner switches parallel-connected to the DC-link, wherein the outer directional devices are connected to capacitors of the split DC-link and to the inner switches. The inner switches are connected to each other at a second midpoint. A DC source terminal, to which a DC source is connectable in parallel over inductances to the inner switches, is included. An inductance is connected to the midpoint of the DC link and to the midpoint of the inner switches.

The present disclosure provides a control method of a DC/DC converter and a related DC/DC converter. The control method allows for: detecting a difference between a first voltage and a second voltage; if an absolute value of the difference between the first voltage and the second voltage is greater than or equal to a preset value, reselecting desired operating states of respective switches in a 1-level state according to the difference between the first voltage and the second voltage and a direction of an average current from a fourth node to a first passive network in the 1-level state; and thus outputting a control signal to enable the voltage difference between the first capacitor and the second capacitor to be reduced, thereby effectively adjusting the neutral-point voltage balance of the DC/DC converter.

For a serial multiplex inverter in which each phase includes cells connected serially, wherein each cell includes switching elements and is configured to output a level of +1 (ON), a level of zero (OFF), and a level of −1 (ON) as output levels by operation of the switching elements, a control device includes a switching load distribution control section. This control section is configured to: store information about an ON-output duration of each of the cells and information about an OFF-output duration of each of the cells; for a shift pattern from ON to OFF in the cells, put OFF a gate signal for one of the cells whose ON-output duration is the longest of the cells; and for a shift pattern from OFF to ON in the cells, put ON a gate signal for one of the cells whose OFF-output duration is the longest of the cells.

A power conversion device includes a power conversion circuit unit including a plurality of leg circuits, and a control device. Each of the leg circuits includes a plurality of first converter cells each having a capacitor and connected in series to each other and a plurality of second converter cells each having the capacitor and connected in series to each other. The plurality of first converter cells are controlled not based on a circulating current circulating between the plurality of leg circuits, and the plurality of second converter cells are controlled based on the circulating current. The control device executes control processing for increasing a current flowing through the second converter cell when a voltage at the capacitor in the second converter cell is less than a first threshold value.

The three-level direct current converter includes: a flying capacitor, a plurality of switch groups, a drive circuit, and a control circuit. The control circuit includes at least an on-time generator. When a voltage on the flying capacitor deviates from a half of a power supply voltage, the on-time generator changes a charging current of a capacitor of the on-time generator to adjust an output on-time signal, and outputs the on-time signal to the drive circuit. The drive circuit generates a drive pulse signal based on the on-time signal to drive switch statuses of the plurality of switch groups, to adjust charging time and discharging time of the flying capacitor, where an absolute value of a difference between the voltage on the flying capacitor and the half of the power supply voltage is less than or equal to a preset threshold.