Various embodiments according to the present invention relate to a power conversion device and method, the device comprising: a converter; a capacitor unit including a plurality of capacitors for storing input voltage input thereto; a switch unit connected to the capacitor unit and including a plurality of switches for selectively connecting at least one capacitor among the plurality of capacitors to the converter; and a controller connected to the capacitor unit and the switch unit, wherein the controller determines at least one capacitor satisfying a specified condition, among the plurality of capacitors, sets at least one switch among the plurality of switches to be turned on, the at least one switch corresponding to the at least one capacitor, and sets at least another switch among the plurality of switches except for the at least one switch, to be turned off, so that the at least one capacitor and the converter are electrically connected and configured to allow at least partial voltage of the input voltage, stored in the at least one capacitor, to be supplied to the converter. Therefore, a power conversion device, disposed on a circuit on which the plurality of capacitors (or cells) is connected in series to a power supply unit, can establish selective connection by using the switch unit, so as to adjust input voltage and provide the adjusted input voltage to the converter, and can reduce switching loss of the power conversion device. Various other embodiments are possible.

A power converter for transforming electrical power between direct current (DC) power and alternating current (AC) power is provided, as well as a controller therefor and associated methods and systems. The power converter comprises: a first set of packed U-cell converters connectable between a first common connection point and a first terminal of an external circuit, the first common connection point connecting to a first terminal of a DC circuit element; a second set of packed U-cell converters connectable between a second common connection point and a second, opposite terminal of the external circuit, the second common connection point connecting to a second, opposite terminal of the DC circuit element; and a controller configured for controlling the operation of the first and second sets of packed U-cell converters.

A three-level converter includes a high-voltage side unit, a low-voltage side unit, a flying capacitor, a first switch to a fourth switch, and a control unit. When a voltage of the flying capacitor falls outside a safe target voltage range, the control unit may control the third switch and the fourth switch to be normally open, and control, based on the voltage of the flying capacitor and a voltage of the low-voltage side unit, each of the first switch and the second switch to be turned on or off, so that the voltage of the flying capacitor falls within the target voltage range. Alternatively, the control unit may control the first switch and the second switch to be normally open, and control, based on the voltage of the flying capacitor and a voltage of the low-voltage side unit.

A fault handling system of a solid-state transformer, including a first power unit and a second power unit that are cascaded and connected is provided. The first power unit includes a first auxiliary supply, a first control module, and a first communication module. The first auxiliary supply and the first control module are both electrically connected to two ends of a first busbar capacitor. The first control module is configured to detect a voltage of the first busbar capacitor. The second power unit includes a second auxiliary supply and a second control module. The second auxiliary supply and the second control module are both electrically connected to two ends of a second busbar capacitor. The first communication module outputs fault information to the second control module when the first control module detects that the voltage of the first busbar capacitor is greater than a threshold.

The present disclosure provides a high voltage device built from modular low voltage cells. Each low voltage cell includes a plurality of low voltage semiconductor devices and one or more low voltage passive components. Each cell can be a current-bidirectional two-quadrant switch or a four-quadrant switch. All the cells may be identical and controlled with a delay time in between. Therefore, the total on and off time of the high voltage device can be controlled to reduce the output equivalent dv/dt. The cell's voltage balancing can be achieved through a control algorithm disclosed herein.

In an MMC-based power conversion device, a control device generates, for each leg circuit, a first voltage command value not based on circulating current circulating between a plurality of leg circuits and a second voltage command value based on the circulating current. A plurality of individual controllers are provided respectively corresponding to a plurality of converter cells and generate a gate control signal for controlling turning on and off of a switching element of the corresponding converter cell, based on the first voltage command value and the second voltage command value. When generating the gate control signal using pulse width modulation, each individual controller modulates a carrier signal in accordance with the second voltage command value such that the pulse width of the gate control signal changes in accordance with the second voltage command value.

A power device may have at least two capacitors in series with each other and in parallel with a DC power source. The power device may have at least a first converter that has at least a controller configured to balance a voltage of the at least two capacitors. The power device may have at least a second converter connected to the at least two capacitors. The second converter may have at least three input conductors, each connected to a terminal of the at least two capacitors. The second converter may have at least two output conductors. The second converter may have at least a switching circuit between the at least three input conductors and at least two output conductors. The second converter may have at least a controller configured to operate the switching circuit. The second converter may passively preserve the voltage balance between the at least two capacitors.

An amplifier comprises: an input stage, a pulse width modulation stage, and a switched output stage. During operation, the input stage receives an input signal (such as an audio signal). The input stage adjusts the input signal based on feedback from the switched output stage of the amplifier. According to one configuration, the feedback from the switched output stage is a voltage across a flying capacitor disposed in the switched output stage. The pulse width modulation stage uses the adjusted input signal or signals to produce respective pulse width modulation signals that are subsequently used to drive (control) switches in the switched output stage. The switches in the switched output stage generate an output voltage to drive a load based on states of the pulse width modulation signals. Adjustments applied to the input signal based on the feedback maintains the magnitude of the flying capacitor voltage at a desired setpoint.

A four-level rectifier may include an output, a first capacitor, a second capacitor, a third capacitor, and three phases. The first, second, and third capacitors may be connected in series. The output may be connected between the first capacitor and the third capacitor. Each of the three phases may include an input, a first diode, a second diode, a first switch, a second switch, and a third switch. The first diode may be connected between the input and the first capacitor. The second diode may be connected between the input and the third capacitor. The first switch may be connected between the input and the second switch and the third switch. The second switch may be connected to the first capacitor and to the second capacitor. The third switch may be connected to the second capacitor and to the third capacitor.

The present disclosure provides a three-phase AC/DC converter aiming for low input current harmonic. The converter includes an input stage for receiving a three-phase AC input voltage, an output stage for at least one load, and one or more switching conversion stages, each stage including a plurality of half bridge modules. The switches in each module operate with a substantially fixed 50% duty cycle and are connected in a specific pattern to couple a DC-link and a neutral node of the input voltage. The AC/DC converter further includes one or more controllers adapted to vary the switching frequency of the switches in the switching conversion stages based on at least one of load voltage, load current, input voltage, and DC-link voltage. The converter can also include one or more decoupling stages, such as, inductive components adapted to decouple the output stage from the switching conversion stages.