A power conversion system includes one power conversion device and one or more power conversion devices. The power conversion device includes a power converter that controls output voltage to be a preset voltage to apply the preset voltage to a load on the basis of an output from a power supply. The power conversion device controls the power converter so that a detected value of the first voltage detected by a voltage detector becomes a preset voltage value. The power conversion devices each include a power converter that controls output current to be a preset current to supply the preset current to the load on the basis of an output from a power supply. The power conversion devices each controls operation of the power converter on the basis of the detected value of the first voltage. The power conversion device controls operation of the power converter by changing the first voltage.

A power conversion system includes one power conversion device and one or more power conversion devices. The power conversion device includes a power converter that controls output voltage to be a preset voltage to apply the preset voltage to a load on the basis of an output from a power supply. The power conversion device controls the power converter so that a detected value of the first voltage detected by a voltage detector becomes a preset voltage value. The power conversion devices each include a power converter that controls output current to be a preset current to supply the preset current to the load on the basis of an output from a power supply. The power conversion devices each controls operation of the power converter on the basis of the detected value of the first voltage. The power conversion device controls operation of the power converter by changing the first voltage.

A power control system includes: a first AC/DC converter; a second AC/DC converter; a first switch connected between a first transmission line of a first power system having a first system frequency and the first AC/DC converter; a second switch connected between the first transmission line and the second AC/DC converter; a third switch connected between a second transmission line of a second power system having a second system frequency and the first AC/DC converter; a fourth switch connected between the second transmission line and the second AC/DC converter; a fifth switch connected between the first AC/DC converter and the second AC/DC converter; and a control device. When the first and second AC/DC converters are caused to operate as AC/DC converters in a BTB (Back to Back) method, the control device controls at least the fifth switch to be in a closed state.

A power conversion system includes one power conversion device and one or more power conversion devices. The power conversion device includes a power converter that controls output voltage to be a preset voltage to apply the preset voltage to a load on the basis of an output from a power supply. The power conversion device controls the power converter so that a detected value of the first voltage detected by a voltage detector becomes a preset voltage value. The power conversion devices each include a power converter that controls output current to be a preset current to supply the preset current to the load on the basis of an output from a power supply. The power conversion devices each controls operation of the power converter on the basis of the detected value of the first voltage. The power conversion device controls operation of the power converter by changing the first voltage.

A converter controller is provided, by which the current valves are controlled by means of a switching frequency. It is provided to alter the switching frequency in a step-wise manner between a first and at least one second integral multiple of the grid frequency. According to the invention, this is effected in that the switching frequency is switched over cyclically, and a frequency spacing between the switching frequencies is at least double the grid frequency, specifically in such a manner that none of the switching frequencies is an integral multiple of another of the switching frequencies. In this way, harmonics can be selectively reduced, no intermediate frequencies being produced, owing to the integrality in relation to the grid frequency.

A converter controller is provided, by which the current valves are controlled by means of a switching frequency. It is provided to alter the switching frequency in a step-wise manner between a first and at least one second integral multiple of the grid frequency. According to the invention, this is effected in that the switching frequency is switched over cyclically, and a frequency spacing between the switching frequencies is at least double the grid frequency, specifically in such a manner that none of the switching frequencies is an integral multiple of another of the switching frequencies. In this way, harmonics can be selectively reduced, no intermediate frequencies being produced, owing to the integrality in relation to the grid frequency.

Apparatus and methods for recovering energy in a petroleum, petrochemical, or chemical plant as described. The apparatus includes a fluid process stream flowing through a petroleum, petrochemical, or chemical process zone. There are at least one variable-resistance power-recovery turbine, a portion of the first process stream flowing through the first power-recovery turbine to generate electric power as direct current therefrom. There is a single DC to AC inverter electrically connected to at least one power-recovery turbine, and the output of the DC to AC inverter electrically connected to a first substation.

A microgrid control system includes a power transmission system configured to supply power to a microgrid, the microgrid configured to receive power from the power transmission system and to supply power to at least one or more distributed generators or into at least one or more loads, a DC converter configured to convert power that is supplied to the microgrid, and a converter control unit configured to measure a first power frequency variation of the microgrid and a second power frequency variation of the power transmission system and to control active power that is transmitted to the microgrid by the DC converter.

A microgrid control system includes a power transmission system configured to supply power to a microgrid, the microgrid configured to receive power from the power transmission system and to supply power to at least one or more distributed generators or into at least one or more loads, a DC converter configured to convert power that is supplied to the microgrid, and a converter control unit configured to measure a first power frequency variation of the microgrid and a second power frequency variation of the power transmission system and to control active power that is transmitted to the microgrid by the DC converter.

Systems and method for synchronizing power generators with a power grid are provided. One system among various implementations includes a plurality of synchronization modules, wherein each synchronization module corresponds to one power generator. The synchronization modules are configured to output a control signal to adjust a frequency of the respective power generator to correspond with the frequency of the existing power grid. The system also includes a central controller in communication with the plurality of synchronization modules. The central controller is configured to determine a propagation delay with respect to each synchronization module. The propagation delay is a measure of time for a signal to propagate from the respective synchronization module to the central controller. The central controller is further configured to send a control signal to each synchronization module to control when each synchronization module connects the respective power generator to the existing power grid.