A converter module for a multi-stage converter includes an energy storage device connected in parallel with a series circuit of a first and a second semiconductor switching unit. At least one of the semiconductor switching units has a bidirectional switch. A switch-on unit is connected in parallel with the bidirectional switch. With the switch-on unit there can be produced a switch-on voltage for switching on the bidirectional switch from a voltage dropping across the bidirectional switch. There is also disclosed a multi-stage converter having the novel converter module and a method for operating the converter module.

Disclosed is a phase-shifted square wave modulation technique for single-phase and three-phase IM2DC applications in HVDC/MVDC systems. A square wave based modulation waveform is applied to each cell of IM2DC and compared to the phase-shifted carrier waveforms to generate device gate signals. As a result, a higher equivalent switching frequency can be achieved, and square wave based arm and AC link waveforms will be generated. In addition, power flow of IM2DC can be controlled by a phase shift angle of the square modulation waveforms between HVS and LVS. The converter cell capacitors can be reduced in size because they are only required to smooth high switching frequency ripple components. In addition, lower TDR can be achieved due to the higher power transferring capability of square waves.

Disclosed is a phase-shifted square wave modulation technique for single-phase and three-phase IM2DC applications in HVDC/MVDC systems. A square wave based modulation waveform is applied to each cell of IM2DC and compared to the phase-shifted carrier waveforms to generate device gate signals. As a result, a higher equivalent switching frequency can be achieved, and square wave based arm and AC link waveforms will be generated. In addition, power flow of IM2DC can be controlled by a phase shift angle of the square modulation waveforms between HVS and LVS. The converter cell capacitors can be reduced in size because they are only required to smooth high switching frequency ripple components. In addition, lower TDR can be achieved due to the higher power transferring capability of square waves.

A power storage power conditioner includes an input part, a voltage-transforming part, a first input-output part, a converting part and a second input-output part. The voltage-transforming part transforms the voltage of DC power from the input part and the converting part into a second predetermined voltage. The first input-output part outputs the DC power of the voltage-transforming part to a battery unit, and inputs DC power from the battery unit. The voltage-transforming part transforms a voltage of the DC power from the first input-output part into a third predetermined voltage. The converting part converts the DC power from the input part and the voltage-transforming part into AC power. The second input-output part outputs the AC power to a power system or a load, and inputs AC power from the power system. The converting part converts the AC power from the second input-output part into DC power.

A power storage power conditioner includes an input part, a voltage-transforming part, a first input-output part, a converting part and a second input-output part. The voltage-transforming part transforms the voltage of DC power from the input part and the converting part into a second predetermined voltage. The first input-output part outputs the DC power of the voltage-transforming part to a battery unit, and inputs DC power from the battery unit. The voltage-transforming part transforms a voltage of the DC power from the first input-output part into a third predetermined voltage. The converting part converts the DC power from the input part and the voltage-transforming part into AC power. The second input-output part outputs the AC power to a power system or a load, and inputs AC power from the power system. The converting part converts the AC power from the second input-output part into DC power.

A series connectable power flow module is for connection to a power transmission line. The module has a full bridge inverter and a controller. The full bridge inverter has inputs for controlling charging and discharging a DC link capacitor. The controller is coupled to the inputs of the full bridge inverter. The controller is configured to separate a harmonic current from a line current flowing in the power transmission line. The controller operates the full bridge inverter in accordance with the separated harmonic current, to attenuate the harmonic current flowing in the power transmission line through injection of a DC link capacitor voltage.

An assembly having a multilevel power converter, which has at least one phase module, wherein the phase module has a plurality of modules, each with a first electrical module terminal and a second electrical module terminal. The plurality of modules includes modules of a first type, which are able to output a voltage of only one polarity or zero voltage at their first electrical module terminal and their second electrical module terminal. The plurality of modules includes modules of a second type, which are able to output a voltage of one polarity, a voltage of opposite polarity or zero voltage at their first electrical module terminal and their second electrical module terminal. Depending on the polarity of a voltage across the modules of the second type, a voltage limiting device limits the voltage.

A line commutated converter, LCC, for a high-voltage, direct current, HVDC, power converter comprises at least one bridge circuit for connection to at least one terminal of a DC system. Each bridge circuit comprises a plurality of arms, and each arm is associated with a respective phase of an AC system. Each arm comprises an upper and lower thyristor connected in series, an associated branch extending from between the upper and lower thyristors, and at least one capacitor module for each phase. The, or each capacitor module is operable to insert a capacitor into the respective arm of the bridge circuit.

A series compensation device suitable to double-circuit lines is disclosed. The device includes one series transformer and one converter. One converter and dual-circuit transmission lines are respectively connected to three windings of one series transformer. In the solution provided in the present application, the device can be independently installed in a power transmission system to be used as a static synchronous series compensator, and can also be used as a component of a unified power flow controller, a convertible static compensator, an interline power flow controller and a unified power quality conditioner to be connected to a power transmission system device in series. The device can save the capacity of a converter, improve the application efficiency of the series compensation device, and reduce the cost and area occupation.

An MMC includes arms configured with one unit converter or a plurality of cells connected in series. The main circuit of the cell includes a switching element and a DC capacitor. The power supply of the cell lowers voltage of the DC capacitor to generate power supply voltage to be supplied to the control circuit of the cell. The power supply includes a power supply circuit configured to convert input voltage provided between first and second input terminals from the DC capacitor into power supply voltage, a thyristor connected between the first and second input terminals electrically in parallel with the power supply circuit, a current-limiting resistor connected between terminals of the DC capacitor electrically in series with the thyristor, and a control unit configured to fire the thyristor when input voltage applied to the power supply circuit exceeds a threshold voltage.