Abstract: The disclosure provides a frequency support method, device and wind farm for a wind farm and belongs to the technical field of new energy power generation and grid connection. In the frequency support method, a state that can reflect a frequency modulation capability of a wind turbine is designed, measured, and recorded as a consistency factor of frequency modulation. Each wind turbine is controlled to exchange the consistency factors with two adjacent wind turbines. Each wind turbine combines its own consistency factors with the consistency factors of two adjacent wind turbines to generate consistent added power through a PI link and adjusts real-time frequency modulation output based on the consistency added power. In this way, the states of the wind turbines in the wind farm are similar during the frequency support process, so that a reasonable distribution of frequency support power is achieved.

Abstract: The disclosure provides a frequency support method, device and wind farm for a wind farm and belongs to the technical field of new energy power generation and grid connection. In the frequency support method, a state that can reflect a frequency modulation capability of a wind turbine is designed, measured, and recorded as a consistency factor of frequency modulation. Each wind turbine is controlled to exchange the consistency factors with two adjacent wind turbines. Each wind turbine combines its own consistency factors with the consistency factors of two adjacent wind turbines to generate consistent added power through a PI link and adjusts real-time frequency modulation output based on the consistency added power. In this way, the states of the wind turbines in the wind farm are similar during the frequency support process, so that a reasonable distribution of frequency support power is achieved.

Abstract: A control method, a control device and a wind farm system for a wind turbine frequency support are provided. The control method includes the following: calculating a comprehensive inertia power value by using a wind farm frequency modulation capability level coefficient when a frequency accident occurs in the wind farm; obtaining a real-time rotational speed of each wind turbine to calculate a state factor that changes in real time, where each wind turbine adjusts a state reference power value of its own by exchanging the state factor with a neighboring wind turbine; and determining instantaneous stator power of each wind turbine by using a MPPT part corresponding to the rotational speed, the comprehensive inertia power value, and the state reference power value, so as to control each wind turbine to perform frequency support until a predetermined frequency support time is reached.

Abstract: The present invention discloses a stereoscopic DC-DC converter for power transfer between two DC grids, the converter comprises a first converter, a second converter and a third converter, a positive terminal of the first converter is connected to a positive terminal of a second DC grid, a negative terminal of the first converter is connected to a positive terminal of the second converter, a negative terminal of the second converter is connected to a positive terminal of the third converter, a negative terminal of the third converter is connected to a negative terminal of the second DC grid, in the meantime, a positive terminal of the second converter is also connected to a positive terminal of a first DC grid, and the negative terminal of the second converter is also connected to a negative terminal of the first DC grid.

Abstract: The present invention discloses a hybrid converter and a wind power generating system, the hybrid converter including a voltage source converter, a line commutated converter and a line commutated converter, a positive DC terminal of the voltage source converter is connected to a negative DC terminal of the line commutated converter, a positive DC terminal of the line commutated converter is connected to a positive DC transmission line, a negative DC terminal of the voltage source converter is connected to a positive DC terminal of the line commutated converter, and a negative DC terminal of the line commutated converter is connected to a negative DC transmission line. The present invention features a self-commutating capability, can be directly connected to a wind farm to convert wind power to DC power, and is able to improve rated voltage and rated power of the hybrid converter, technology of each component thereof is mature, and system reliability thereof is high.

Abstract: A multiport DC-DC autotransformer for interconnecting three or more DC systems. The autotransformer includes 2N?1 converters sequentially connected in series at a DC side, and connected to an AC transmission line via an AC link at an AC side, and a positive terminal of the ith converter of the 2N?1 sequentially connected converters and a negative terminal of the (2N?i)th converter are respectively connected to a positive terminal of the ith DC system and a negative terminal thereof, where N represents the number of DC systems, and i represents the serial number of converters. Also disclosed are a method for determining power rating of each converter of the multiport DC-DC autotransformer, and a method for controlling the autotransformer. Most power can be transferred between different DC systems via a direct electrical connection without DC-AC-DC conversion.

Abstract: The present invention discloses a stereoscopic DC-DC converter for power transfer between two DC grids, the converter comprises a first converter, a second converter and a third converter, a positive terminal of the first converter is connected to a positive terminal of a second DC grid, a negative terminal of the first converter is connected to a positive terminal of the second converter, a negative terminal of the second converter is connected to a positive terminal of the third converter, a negative terminal of the third converter is connected to a negative terminal of the second DC grid, in the meantime, a positive terminal of the second converter is also connected to a positive terminal of a first DC grid, and the negative terminal of the second converter is also connected to a negative terminal of the first DC grid.

Abstract: A sub-module for a modular multi-level converter, a converter comprising the sub-module, and an application thereof. The sub-module comprises a first switching module (1), a second switching module (2), a direct current capacitor (4), and a third switching module (3). The first switching module (1) and the second switching module (2) are connected in series, a negative end of the first switching module (1) is connected to a positive end of the second switching module (2), and the switching modules (1, 2, 3) are each formed by connecting a full-controlled device and a diode in an antiparallel mode. A positive electrode and a negative electrode of the direct current capacitor (4) are connected to a positive end of the first switching module (1) and a negative end of the second switching module (2).

Abstract: A multiport DC-DC autotransformer for interconnecting three or more DC systems. The autotransformer includes 2N?1 converters sequentially connected in series at a DC side, and connected to an AC transmission line via an AC link at an AC side, and a positive terminal of the ith converter of the 2N?1 sequentially connected converters and a negative terminal of the (2N?i)th converter are respectively connected to a positive terminal of the ith DC system and a negative terminal thereof, where N represents the number of DC systems, and i represents the serial number of converters. Also disclosed are a method for determining power rating of each converter of the multiport DC-DC autotransformer, and a method for controlling the autotransformer. Most power can be transferred between different DC systems via a direct electrical connection without DC-AC-DC conversion.

Abstract: The present invention discloses a hybrid converter and a wind power generating system, the hybrid converter comprising a voltage source converter, a line commutated converter and a line commutated converter, a positive DC terminal of the voltage source converter is connected to a negative DC terminal of the line commutated converter, a positive DC terminal of the line commutated converter is connected to a positive DC transmission line, a negative DC terminal of the voltage source converter is connected to a positive DC terminal of the line commutated converter, and a negative DC terminal of the line commutated converter is connected to a negative DC transmission line. The present invention features a self-commutating capability, can be directly connected to a wind farm to convert wind power to DC power, and is able to improve rated voltage and rated power of the hybrid converter, technology of each component thereof is mature, and system reliability thereof is high.