MMC converter station low voltage ride through method and system based on resonant controller

Abstract

The invention discloses a low-voltage ride-through method and control system of an MMC converter station based on a resonance controller. This method aims at the problem of distortion of the output current of the MMC converter station when the asymmetric fault of the power grid occurs, and realizes the suppression of the negative sequence, zero sequence components and internal circulating current in the output current through three resonant controllers. Compared with the existing method of separately controlling the positive and negative sequence components of the current in the positive and negative synchronous coordinate system, the control structure of this method is simpler, and the zero-sequence current can be suppressed to further improve the power output of the MMC converter station. capacity, thereby reducing the design capacity of the DC chopper, lowering the cost of engineering construction, and even realizing the fault ride-through operation of the system without using the DC chopper when the fault is minor. In the present invention, the low-voltage ride-through method of the MMC converter station based on the resonant controller is simple in structure, remarkable in effect, and has strong engineering practical value.

Description

technical field [0001] The invention relates to a low-voltage ride-through method and system of an MMC converter station based on a resonance controller, which is applicable to the technical field of power electronics. Background technique [0002] In recent years, with the vigorous development of offshore wind power, the construction of offshore wind farms has gradually shifted from short-distance and small-capacity to deep-sea and large-scale. Due to its mature technology and low equipment cost, the traditional AC transmission technology is more suitable for offshore wind farms with low capacity and short distance. However, when it faces the deep sea, there are problems such as high line cost, large reactive power loss, and weak support for wind farms. Therefore, generally when the routing distance exceeds 70-80km, it is the current development consensus to adopt more economical and effective HVDC transmission technology. The flexible DC transmission technology based on ...

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Problems solved by technology

However, this method needs to separate the positive and negative sequence components of the voltage and current, and also needs to use two sets of control systems to control the positive and negative sequence components separately in two coordinate systems. In addition, the common mode current needs to be transformed into a third The control structure is very complicated, and the control parameters need to be redesigned.

In addition, since the power grid fault point is connected to the MMC by a connection transformer, when the connection transformer adopts Y 0 / Y 0 When connected, an additional zero-sequence circuit will be generated

At this time, the output current of the MMC converter will contain a large number of zero-sequence components, which will further lead to distortion of the current waveform and seriously affect the power delivery capability of the converter.

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