Provided are a method and system for controlling a voltage. The method includes: acquiring a current output voltage of an inverter; calculating a current voltage error of the current output voltage relative to a given output voltage; inputting the current voltage error into a fuzzy controller to determine a target output voltage of the inverter; determining an amplitude adjustment command based on a difference between an amplitude of the target output voltage and an amplitude of the current output voltage; determining a phase adjustment command based on a difference between a phase of the target output voltage and a phase of the current output voltage; and adjusting an amplitude and a phase of an output voltage of the inverter according to the amplitude adjustment command and the phase adjustment command respectively, to maintain the output voltage of the inverter within a preset range.

A power conversion apparatus includes a filter capacitor, a contactor to electrically connect the filter capacitor to a power source or electrically disconnect the filter capacitor from the power source, and a failure determiner to determine whether a failure occurs in the contactor. When the contactor is kept closed during a determination period since closing of the contactor and a reduction in the voltage in the filter capacitor during the determination period is greater than or equal to a reference value, the failure determiner determines occurrence of a failure in the contactor.

A power conversion apparatus includes a filter capacitor, a contactor to electrically connect the filter capacitor to a power source or electrically disconnect the filter capacitor from the power source, and a failure determiner to determine whether a failure occurs in the contactor. When the contactor is kept closed during a determination period since closing of the contactor and a reduction in the voltage in the filter capacitor during the determination period is greater than or equal to a reference value, the failure determiner determines occurrence of a failure in the contactor.

A method and system include determining a resonant frequency of a vehicle system operably coupled with an external power source that provides voltage and current to the vehicle system. A first filter extracts a phase or a frequency component from the voltage provided by the external power source to generate a stabilizing voltage component. A second filter extracts a phase or a frequency component from the current provided by the external power source to generate a stabilizing current component. The stabilizing voltage component is out of phase with the stabilizing current component. A control input of a converter device of the vehicle system is determined based on the stabilizing voltage component, the stabilizing current component, and the resonant frequency. The stabilizing voltage component, the stabilizing current component, and the control input are communicated with the converter device to change the resonant frequency of the vehicle system.

A method and system include determining a resonant frequency of a vehicle system operably coupled with an external power source that provides voltage and current to the vehicle system. A first filter extracts a phase or a frequency component from the voltage provided by the external power source to generate a stabilizing voltage component. A second filter extracts a phase or a frequency component from the current provided by the external power source to generate a stabilizing current component. The stabilizing voltage component is out of phase with the stabilizing current component. A control input of a converter device of the vehicle system is determined based on the stabilizing voltage component, the stabilizing current component, and the resonant frequency. The stabilizing voltage component, the stabilizing current component, and the control input are communicated with the converter device to change the resonant frequency of the vehicle system.

A method for supplying power to railway operating elements that are arranged along a railway line. A terminal station has a power supply device. At least one substation has a power supply subunit for at least one connected railway operating element. An input-side control unit of the substation modifies the current consumption in the substation incrementally, with corresponding modification of the voltage of the power supply subunit to match the rated voltage of the railway operating element on the substation, and producing a coded message. The control device of the terminal station modifies the output voltage according to the coded message, until the rated voltage for the railway operating element is reached on the power supply subunit. When the nominal voltage is reached the power supply subunit is connected to the railway operating element.

A method for supplying power to railway operating elements that are arranged along a railway line. A terminal station has a power supply device. At least one substation has a power supply subunit for at least one connected railway operating element. An input-side control unit of the substation modifies the current consumption in the substation incrementally, with corresponding modification of the voltage of the power supply subunit to match the rated voltage of the railway operating element on the substation, and producing a coded message. The control device of the terminal station modifies the output voltage according to the coded message, until the rated voltage for the railway operating element is reached on the power supply subunit. When the nominal voltage is reached the power supply subunit is connected to the railway operating element.

A DC feeder voltage computing device includes a model information storing unit, a run history information storing unit, and a voltage setting value computing unit. The model information storing unit stores model information. The run history information storing unit stores, on a per train basis, run history information that indicates locations and power situations of a plurality of trains that run in a DC-electrified section on or before a preceding day. The voltage setting value computing unit computes, on the basis of the model information and the run history information, a voltage setting value for controlling a substation voltage to cause an amount of power consumption in the DC-electrified section to satisfy a preset condition.

A method of controlling a Modular Multilevel Converter (MMC) during a fault in a power grid to which the MMC is connected is disclosed. The MMC includes a plurality of phases, each including at least one phase leg. Each phase leg includes a plurality of series connected converter cells. The method includes determining that a fault has occurred in the power grid, the fault including a reduced voltage in the power grid. The method also includes, for each phase leg of the MMC, reducing the DC voltage of the phase leg by a predetermined amount from a nominal DC voltage to a reduced DC voltage, the DC voltage being the sum of all respective voltages over an energy storage of each cell of the phase leg. The method also includes determining that the fault has been cleared, whereby the voltage in the power grid is returned to nominal. The method also includes for each of the phase legs of the MMC, increasing the DC voltage back to the nominal DC voltage.

A method of controlling a Modular Multilevel Converter (MMC) during a fault in a power grid to which the MMC is connected is disclosed. The MMC includes a plurality of phases, each including at least one phase leg. Each phase leg includes a plurality of series connected converter cells. The method includes determining that a fault has occurred in the power grid, the fault including a reduced voltage in the power grid. The method also includes, for each phase leg of the MMC, reducing the DC voltage of the phase leg by a predetermined amount from a nominal DC voltage to a reduced DC voltage, the DC voltage being the sum of all respective voltages over an energy storage of each cell of the phase leg. The method also includes determining that the fault has been cleared, whereby the voltage in the power grid is returned to nominal. The method also includes for each of the phase legs of the MMC, increasing the DC voltage back to the nominal DC voltage.