An AC-to-AC modular multilevel converter (MMC) is configured to be connected between a three-phase AC system and a single-phase AC system. The MMC includes a number of converter arms connected in a ring to allow a circulating current to be circulated in the ring through each of the converter arms. Each converter arm includes series-connected converter cells. Phase terminals are arranged in the ring between the converter arms such that each of the converter arms is separated from neighboring converter arms by at least one of the phase terminals. The phase terminals include respective terminals for each of a first phase, a second phase and a third phase of the three-phase AC system and respective terminals for each of a positive conductor and a negative conductor of the single-phase AC system.

An AC-to-AC modular multilevel converter (MMC) is configured to be connected between a three-phase AC system and a single-phase AC system. The MMC includes a number of converter arms connected in a ring to allow a circulating current to be circulated in the ring through each of the converter arms. Each converter arm includes series-connected converter cells. Phase terminals are arranged in the ring between the converter arms such that each of the converter arms is separated from neighboring converter arms by at least one of the phase terminals. The phase terminals include respective terminals for each of a first phase, a second phase and a third phase of the three-phase AC system and respective terminals for each of a positive conductor and a negative conductor of the single-phase AC system.

A converter includes a transformer including primary windings and secondary windings, switches connected to the primary windings, an output inductor connected to the secondary windings, and a controller connected to the switches. The controller turns the switches on and off based on dwell times calculated using space vector modulation with a reference current {right arrow over (I)}.sub.ref whose magnitude changes with time.

A converter includes a transformer including primary windings and secondary windings, switches connected to the primary windings, an output inductor connected to the secondary windings, and a controller connected to the switches. The controller turns the switches on and off based on dwell times calculated using space vector modulation with a reference current {right arrow over (I)}.sub.ref whose magnitude changes with time.

In a power conversion device, a constant voltage can be supplied even when the voltage of an alternating current power supply fluctuates. A switching element Q1 and switching element Q2 are connected to a direct current power supply series circuit. A connection point of a direct current power supply and direct current power supply is a neutral point terminal, a connection point of the switching element Q1 and switching element Q2 is an output terminal, switch elements S1 and S2 are connected between the output terminal and neutral point terminal, switch elements S3 and S4 are connected between a terminal R of an alternating current power supply having a terminal S connected to the neutral point terminal, and the output terminal, and a first element and second element selected from among the switching elements Q1 and Q2 and switch elements S1 to S4 are turned on and off complementarily.

In a power conversion device, a constant voltage can be supplied even when the voltage of an alternating current power supply fluctuates. A switching element Q1 and switching element Q2 are connected to a direct current power supply series circuit. A connection point of a direct current power supply and direct current power supply is a neutral point terminal, a connection point of the switching element Q1 and switching element Q2 is an output terminal, switch elements S1 and S2 are connected between the output terminal and neutral point terminal, switch elements S3 and S4 are connected between a terminal R of an alternating current power supply having a terminal S connected to the neutral point terminal, and the output terminal, and a first element and second element selected from among the switching elements Q1 and Q2 and switch elements S1 to S4 are turned on and off complementarily.

The present application presents a solution that intends to solve the problem of providing a single-stage bidirectional power conversion system (PCS) with a controllable power factor and the capability to regulate the current in the DC side. Disclosed is a single-stage, bidirectional and high-frequency isolated PCS, comprising a high-frequency transformer (HFT), a three-phase-to-single-phase matrix converter (MC), a full-bridge (FB) AC to DC converter, and a control system, where the control system outputs are connected to the switches of the MC and the FB converter. Moreover, the PCS output can also form a DC network for energy supply of several devices. This system converts three-phase AC power input from the network into DC power output that can be used for example to charge an energy storage device or supply a direct current distribution system. It is also possible to convert DC power input into AC power output to supply the network.

A converter includes: a terminal that receives code-modulated power into which first alternating-current power has been code-modulated with a modulation code; and a circuit that converts the code-modulated power with a conversion code to generate second alternating-current power. The conversion code is based on the modulation code. A frequency of the second alternating-current power is higher than a frequency of the first alternating-current power.

A converter includes: a terminal that receives code-modulated power into which first alternating-current power has been code-modulated with a modulation code; and a circuit that converts the code-modulated power with a conversion code to generate second alternating-current power. The conversion code is based on the modulation code. A frequency of the second alternating-current power is higher than a frequency of the first alternating-current power.

A converter includes: a terminal that receives code-modulated power into which first alternating-current power has been code-modulated with a modulation code; and a circuit that converts the code-modulated power with a conversion code to generate second alternating-current power. The conversion code is based on the modulation code. A frequency of the second alternating-current power is lower than a frequency of the first alternating-current power.