A conversion device includes: an inductor electrically connected to the AC power grid; a first-stage converter configured to output a bus voltage according to the AC power grid, wherein the first-stage converter includes an N-level alternating current-direct current (AC-DC) converter, and the N-level AC-DC converter includes a plurality of switch bridge arms, wherein both an upper bridge arm and a lower bridge arm of each of the plurality of switch bridge arms of the N-level AC-DC converter include a plurality of semiconductor devices connected in series, and a rated withstand voltage Vsemi of each of the semiconductor devices is greater than or equal to (Vbus*δ)/((N−1)*Nseries*λ); and a second-stage converter configured to convert the bus voltage into an output voltage to supply energy to the load.

A conversion device includes: an inductor electrically connected to the AC power grid; a first-stage converter configured to output a bus voltage according to the AC power grid, wherein the first-stage converter includes an N-level alternating current-direct current (AC-DC) converter, and the N-level AC-DC converter includes a plurality of switch bridge arms, wherein both an upper bridge arm and a lower bridge arm of each of the plurality of switch bridge arms of the N-level AC-DC converter include a plurality of semiconductor devices connected in series, and a rated withstand voltage Vsemi of each of the semiconductor devices is greater than or equal to (Vbus*δ)/((N−1)*Nseries*λ); and a second-stage converter configured to convert the bus voltage into an output voltage to supply energy to the load.

A basic unit for a power converter, a power converter, and a universal power interface are disclosed. The basic unit includes an inductor, a power half-bridge, a first terminal, a second terminal, a third terminal, and a fourth terminal, where an end of the inductor is connected to a midpoint of the power half-bridge, and the other end of the inductor is connected to the first terminal; a source terminal of a lower bridge arm of the power half-bridge is connected to the second terminal and the fourth terminal; and a drain terminal of an upper bridge arm of the power half-bridge is connected to the third terminal. The manufacturing costs of a microgrid system and the difficulty of later maintenance can be reduced.

A matrix converter includes one or more current sensors structured to sense current flowing through the matrix converter, a matrix of switches including a number of solid state transistors, and a control circuit structured to detect faults in power flowing through the matrix converter based on the sensed current, to control the matrix of switches to drive an external device, and to control the matrix of switches to switch to prevent power from flowing internal to the matrix converter, or external to the external device in response to detecting a fault in power flowing through the matrix converter.

A control device for an MMC is disclosed. The control device for an MMC including a plurality of converter arms that include a plurality of sub-modules connected in series and that are connected to a DC link includes: an arm controller, which detects the arm current of a converter arm so as to determine whether a DC failure has occurred, and, if it is determined that the DC failure has occurred, transmits a bypass control signal for protecting a sub-module and notifies of the DC failure; a sub-module controller for controlling the sub-module so as to bypass a DC failure current according to the bypass control signal received from the arm controller; and a main controller, which detects, in real-time, the arm current of the converter arm and a voltage (DC link voltage) of the DC link, determines whether the DC failure is a temporary DC failure or a permanent DC failure on the basis of the detected arm current and DC link voltage if the occurrence of the DC failure is notified by the arm controller, and transmits, to the arm controller, a normal operation control signal for normal operation of the sub-module or a bypass control signal for bypassing of the DC failure current.

A control device for an MMC is disclosed. The control device for an MMC including a plurality of converter arms that include a plurality of sub-modules connected in series and that are connected to a DC link includes: an arm controller, which detects the arm current of a converter arm so as to determine whether a DC failure has occurred, and, if it is determined that the DC failure has occurred, transmits a bypass control signal for protecting a sub-module and notifies of the DC failure; a sub-module controller for controlling the sub-module so as to bypass a DC failure current according to the bypass control signal received from the arm controller; and a main controller, which detects, in real-time, the arm current of the converter arm and a voltage (DC link voltage) of the DC link, determines whether the DC failure is a temporary DC failure or a permanent DC failure on the basis of the detected arm current and DC link voltage if the occurrence of the DC failure is notified by the arm controller, and transmits, to the arm controller, a normal operation control signal for normal operation of the sub-module or a bypass control signal for bypassing of the DC failure current.

An AC-AC converter can include a stack of four switches. An input of the converter can be coupled across the stack of four switches, and an output of the converter can be taken from first terminal coupled to a connection point of first and second switches of the stack and a second terminal coupled to a connection point of third and fourth switches of the stack. The converter can further include a controller that operates the switches such that during a positive half cycle of an AC input voltage, the first and second switches are operated with an alternating 50% duty cycle and the third and fourth switches are constantly on, and during the negative half cycle of the AC input voltage, the third and fourth switches are operated with an alternating 50% duty cycle and the first and second switches are constantly on.

Transformer assembly including a first transformer stage having a plurality of first-stage transformer cells; and a second transformer stage. An input of the second transformer stage is connected to an output of the first transformer stage. A lightning impulse breakdown voltage of a transformer cell of the second stage is at least double of a lightning impulse breakdown voltage of transformer cells of the first stage.

A power supply system includes a plurality of power conversion devices connected in parallel with each other, a load state detector to detect an operating state of a load connected to the DC system, and a command generator to generate a distribution voltage command Vref Each of the power conversion devices includes a DC voltage controller to generate an output power command Pdc_ref based on a voltage of the DC system and the distribution voltage command Vref, and an AC/DC converter to convert AC power received from the main power source based on the output power command Pdc_ref and output the converted power to the DC system. The command generator generates the distribution voltage command Vref such that loss of the load connected to the DC system is reduced, based on a detection result of the load state detector.

AC to DC power supplies are disclosed. One AC to DC power supply includes a transformer having a primary side and a secondary side and a passive rectifier coupled to the secondary side of the transformer. The passive rectifier is configured to rectify AC power at the secondary side to DC power at an output of the rectifier. An active rectifier is configured to control voltages applied to the primary side of the transformer to induce a non-sinusoidal voltage at the secondary side of the transformer and a sinusoidal current drawn by the passive rectifier. An isolating DC-to-DC converter is coupled between the active rectifier and the output of the passive rectifier to magnetically couple power from the active rectifier to the output of the passive rectifier while galvanically isolating the active rectifier from the output of the passive rectifier.