A wind farm, and a method for controlling high voltage ride through, a system, a MMC and a machine-side converter therefor are provided. The method for controlling high voltage ride through control method for the wind farm includes: determining an amplitude of a voltage of a power grid; determining that a high voltage ride through event is occurred under a condition that the amplitude of the voltage of the power grid exceeds a first threshold; acquiring a fundamental frequency modulation wave of the MMC; superimposing a triple harmonic on the fundamental frequency modulation wave to obtain a superimposed modulation wave; and controlling the MMC to operate basing on the superimposed modulation wave.

Provided is a power management apparatus for controlling power distribution from a location that includes a storage battery and a current control type converter to another location that includes a storage battery, the power management apparatus including: a monitor unit that acquires a status of the storage battery at each location; a judgment unit that determines, based on the status of the storage battery at each location that has been acquired by the monitor unit, a duration of power distribution to a certain location, and one or more locations from which power is to be distributed to the certain location; and a control unit that controls each location serving as a distribution source such that power distribution is performed for the duration determined by the judgment unit.

Provided is a power management apparatus for controlling power distribution from a location that includes a storage battery and a current control type converter to another location that includes a storage battery, the power management apparatus including: a monitor unit that acquires a status of the storage battery at each location; a judgment unit that determines, based on the status of the storage battery at each location that has been acquired by the monitor unit, a duration of power distribution to a certain location, and one or more locations from which power is to be distributed to the certain location; and a control unit that controls each location serving as a distribution source such that power distribution is performed for the duration determined by the judgment unit.

A method of controlling output levels of an MMC converter to reduce fluctuation in a power grid frequency, which adjusts an output level of the MMC converter in response to a change in a power grid frequency of a power grid system in the MMC converter connected to a grid system, is proposed. The method includes a detection step of detecting a power grid frequency of a grid connected to the MMC converter in real time, a comparison step of comparing the detected power grid frequency with a preset reference power grid frequency, and an adjustment step of adjusting a number of output levels of the MMC converter to reduce a difference between the detected power grid frequency and the reference power grid frequency when the detected power grid frequency and the reference power grid frequency are different from each other.

A method of controlling output levels of an MMC converter to reduce fluctuation in a power grid frequency, which adjusts an output level of the MMC converter in response to a change in a power grid frequency of a power grid system in the MMC converter connected to a grid system, is proposed. The method includes a detection step of detecting a power grid frequency of a grid connected to the MMC converter in real time, a comparison step of comparing the detected power grid frequency with a preset reference power grid frequency, and an adjustment step of adjusting a number of output levels of the MMC converter to reduce a difference between the detected power grid frequency and the reference power grid frequency when the detected power grid frequency and the reference power grid frequency are different from each other.

A high voltage direct current power transmission series valve group control device, is used for regulating a series circuit having two or more valve groups provided with controllable power semiconductors respectively. Each valve group is provided with a current regulation unit and a voltage regulation unit. The current regulation unit controls a direct current current flowing through a valve group corresponding thereto, and the voltage regulation unit controls a voltage across two ends of a valve group corresponding thereto. One valve group is selected from the series valve group as a master control valve group, while the others are taken as slave control valve groups. The master control valve group selects a trigger angle output by the current regulation unit to control same, and the slave control valve group selects a trigger angle obtained after the trigger angle transmitted from the master control valve group and an output value of the voltage regulation unit pass through a subtractor to control same.

A high voltage direct current power transmission series valve group control device, is used for regulating a series circuit having two or more valve groups provided with controllable power semiconductors respectively. Each valve group is provided with a current regulation unit and a voltage regulation unit. The current regulation unit controls a direct current current flowing through a valve group corresponding thereto, and the voltage regulation unit controls a voltage across two ends of a valve group corresponding thereto. One valve group is selected from the series valve group as a master control valve group, while the others are taken as slave control valve groups. The master control valve group selects a trigger angle output by the current regulation unit to control same, and the slave control valve group selects a trigger angle obtained after the trigger angle transmitted from the master control valve group and an output value of the voltage regulation unit pass through a subtractor to control same.

The present invention relates to a power management system (PMS) for multiple energy storage systems (ESS) that is for integrated management of the system having multiple ESS for controlling a frequency and having a hierarchical control structure. The PMS for ESS comprises: a plurality of ESS; a local management system (LMS) for managing one or more ESS of the plurality of ESS for each local unit; an ESS Controller (ESSC) for general management of the LMS, judging a state of the LMS and determining an output value of one or more ESS in the LMS, and transmitting the determined output value to the respective ESS; and a PMS for general management of the entire system comprising the plurality of ESS, the LMS and the ESSC, judging the state of the entire system and participating in a power grid frequency control market through a grid operator contract, controlling the output of the LMS, and adjusting a control parameter for output control.

A control circuit is provided, including first and second terminals for connection to an electrical network; a current transmission path extending between the first and second terminals, the current transmission path including first and second current transmission path portions, the first and second current transmission path portions being arranged to permit a current flowing, in use, between the first and second terminals and through the first current transmission path portion to bypass the second current transmission path portion and to permit a current flowing, in use, between the first and second terminals and through the second current transmission path portion to bypass the first current transmission path portion; and a controller configured to selectively remove the or each energy storage device from the respective current transmission path portion to cause current to flow from the electrical network through the current transmission path and the or each energy conversion element.

A control circuit is provided, including first and second terminals for connection to an electrical network; a current transmission path extending between the first and second terminals, the current transmission path including first and second current transmission path portions, the first and second current transmission path portions being arranged to permit a current flowing, in use, between the first and second terminals and through the first current transmission path portion to bypass the second current transmission path portion and to permit a current flowing, in use, between the first and second terminals and through the second current transmission path portion to bypass the first current transmission path portion; and a controller configured to selectively remove the or each energy storage device from the respective current transmission path portion to cause current to flow from the electrical network through the current transmission path and the or each energy conversion element.