A multilevel converter includes a power supply assembly with a plurality of phases, and a power cell assembly with first power cells and second power cells. The first power cells and second power cells have a same topology and a same current rating, and supply power to the plurality of phases of the power supply assembly. Each phase of the plurality of phases includes a first power cell and a second power cell of the power cell assembly, voltage ratings of the first power cells and the second power cells being different. Furthermore, a method for controlling a multilevel converter and an electric drive system comprising a multilevel converter are disclosed.

A power conversion method comprising: charging a plurality of energy storage devices of a power converter from an input power source; and sequentially coupling and decoupling energy storage devices of the plurality of energy storage devices to an output. Charging the plurality of energy storage devices comprises maintaining at least two of the plurality of energy storage devices at substantially different potentials.

A power conversion method comprising: charging a plurality of energy storage devices of a power converter from an input power source; and sequentially coupling and decoupling energy storage devices of the plurality of energy storage devices to an output. Charging the plurality of energy storage devices comprises maintaining at least two of the plurality of energy storage devices at substantially different potentials.

A power conversion device includes a power-supply shunt resistance that is provided between an inverter and the negative-voltage side of a DC power supply, and respective-phase lower-arm shunt resistances that are provided between the power-supply shunt resistance and respective-phase lower-arm switching elements. Respective-phase lower-arm voltages, that are respective voltages between the negative-voltage side of the DC power supply and connection points between the respective-phase lower-arm switching elements and the respective-phase lower-arm shunt resistances, are detected to calculate respective-phase currents that flow through a load device in accordance with detection values of the respective-phase lower-arm voltages, and to control a carrier frequency of a carrier signal, which serves as a reference frequency of each drive signal, according to a change in a specific control parameter A.

A power conversion device includes a power-supply shunt resistance that is provided between an inverter and the negative-voltage side of a DC power supply, and respective-phase lower-arm shunt resistances that are provided between the power-supply shunt resistance and respective-phase lower-arm switching elements. Respective-phase lower-arm voltages, that are respective voltages between the negative-voltage side of the DC power supply and connection points between the respective-phase lower-arm switching elements and the respective-phase lower-arm shunt resistances, are detected to calculate respective-phase currents that flow through a load device in accordance with detection values of the respective-phase lower-arm voltages, and to control a carrier frequency of a carrier signal, which serves as a reference frequency of each drive signal, according to a change in a specific control parameter A.

A multilevel converter includes a power supply assembly with a plurality of phases, and a power cell assembly with first power cells and second power cells. The first power cells and second power cells have a same topology and a same current rating, and supply power to the plurality of phases of the power supply assembly. Each phase of the plurality of phases includes a first power cell and a second power cell of the power cell assembly, voltage ratings of the first power cells and the second power cells being different. Furthermore, a method for controlling a multilevel converter and an electric drive system comprising a multilevel converter are disclosed.

A primary-side inverter is connected to three output terminals of six output terminals included in a motor with an open winding structure including windings of three independent phases and a secondary-side inverter is connected to the remaining three output terminals. Direct current power is supplied to the inverters, and a control device performs PWM control on the inverters by using a switching pattern in which the numbers of phases where each is turned on are equal, and in the switching pattern, ON of only an upper is continued in one phase from among the three phase outputs, OFF of only a lower is continued in another phase, and the upper and lower are alternately turned on and off such that mutual phases are opposite in the remaining one phase in one cycle of an electric angle of the motor over a plural carrier cycles in PWM control.