The present invention provides a Pulse Width Modulation (PWM) method for a Cascaded H-bridge (CHB) converter. Each phase of the converter is provided with n Cascaded H-bridge rectifier circuits, or may also be provided with n Cascaded H-bridge rectifier circuits+1 redundant H-bridge rectifier circuit. The method includes following steps of: S1, generating groups of sinusoidal signals as reference waveforms, and generating n carrier signals having sequentially decreasing levels and equal amplitudes to correspond to the H-bridge rectifier circuit at the first to the n.sup.th levels, where the levels of the n carrier signals are cascaded to fill the voltage amplitude of a unipolar half cycle of the reference waveform; and S2, determining PWM signals for controlling power transistors of the corresponding H-bridge rectifier circuits based on each reference waveform and each carrier signal. According to the present invention, the CHB converter allows the MV grid to be directly coupled with a LV side without a conventional transformer, which reduces the heat loss and balances the distribution of heat loss between the power transistors and between the H-bridges at all levels, thus prolonging the service life.

A resonant parallel triple active bridge converter comprising a DC port configured to receive DC energy, an AC port configured to produce AC energy, and an AC line cycle energy storage port, coupled to both the DC port and the AC port, where the AC line cycle energy storage port comprises an energy storage device for storing energy during an energy conversion process.

A method and apparatus for providing welding-type power is disclosed. It includes an input circuit, a dc bus, an output circuit, and a control module. The input circuit receives power and provides an intermediate signal to the bus. The output circuit receives the dc bus and provides an ac welding-type output. The output circuit includes a half-bridge output inverter with at least first and second switches. The output inverter further includes an output control circuit. The output control circuit provides freewheeling paths that includes control switches, the output, antiparallel diodes. The control module has a four quadrant control module that provides control signals to the half bridge output inverter and provides modulating control signals to the first and second output control switches. The modulating signals cause the output control switches to be turned on and off multiple times to control a rate of change of output current.

A power supply circuit includes at least two input terminals that receive an input voltage, a transformer including a primary side electrically connected to the input voltage, a rectifier electrically connected to a secondary side of the transformer, and a boost switch electrically connected in parallel with the rectifier and a pair of output voltage terminals that include a first output voltage terminal and a second output voltage terminal. The input voltage is electrically connected to an AC source, and each of the at least two input terminals receives a different phase of the AC source.

A power conversion device includes a power converter including at least a first converter for converting battery power output by a battery into first output power of a first voltage waveform based on an input or set output waveform profile and outputting the first output power from a first terminal pair and a second converter for converting the battery power into second output power of a second voltage waveform of a rectangular shape and outputting the second output power from a second terminal pair and configured to supply a load with third output power of an alternating current (AC) control waveform generated by adding the first output power to the second output power, and a controller configured to output a voltage command value for outputting the first output power as the output waveform profile to the first converter to the power converter on the basis of the input request command value of output power for the load and the voltage value of the third output power output by the power converter.

An inverter device includes a converter circuit and a filter. The converter circuit converts a DC input voltage into an AC intermediate voltage based on six control signals, and includes first and second converters. Each of the first and second converters includes three switches, two diodes and a coupled inductor circuit. The switches of the first converter operate respectively based on three of the control signals. The switches of the second converter operate respectively based on the other three of the control signals. The filter filters the AC intermediate voltage to generate an AC output voltage.

A power conversion apparatus connected to three or more voltage units, includes three or more power conversion circuits connected to respective units of the three or more voltage units; and a multiport transformer connected to the three or more power conversion circuits at mutually different ports, in which at least one voltage unit of the three or more voltage units is an electrical load.

A drive circuit for driving an electro-optical device like an optically switchable glazing, e.g. a glass panel provided with a PDLC or SPD layer, comprises a set of input terminals for receiving an alternating input voltage at a first frequency; a set of output terminals for supplying an alternating output voltage at a second frequency; a control circuit generating a control signal dependent on an input signal, the input signal representing a charge state of the electro-optical device; and a current-direction circuit for controlling a current-flow direction of an electrical current in response to the control signal. The control circuit and the current-direction circuit are thereby configured to control the second frequency such that the electro-optical device is prevented from degradation, while keeping an energy consumption low.

A multilevel stage of a bidirectional AC power converter, comprising: a set of switches in series, a set of capacitors in series, the set of capacitors being in parallel with the set of switches; a number of sets of diodes in series; a center tap along the set of switches in series; and a pair of taps, respectively after the first and before the last switch of the set of switches in series; wherein each node between respective capacitors is connected to a node between respective diodes. A converter first stage for a 3-level converter has 6 switches, two capacitors, and two diodes, with the junction between diodes connected to the junction between capacitors, and the diode legs between switches 2-3 and 4-5. The center tap is between switches 3-4, and the pair of taps between switches 1-2 and 5-6.

A power conversion system comprising, three full wave LLC resonant converters each of which has an associated high frequency isolation transformer, a full wave rectifier and an unfolding inverter, to provide a direct connection to a Medium Voltage (MV) three-phase grid for a high power photovoltaic system.