MMC converter station low-voltage ride-through method based on resonance controllers and control system

Abstract

The invention discloses an MMC converter station low-voltage ride-through method based on resonance controllers and a control system. In order to solve the problem of output current distortion of an MMC converter station when an asymmetric fault of a power grid occurs, suppression of negative-sequence and zero-sequence components and an internal loop current in the output current is realized through three resonance controllers respectively. Compared with the existing method for respectively controlling the positive and negative sequence components of the current under a forward and reverse rotation synchronous coordinate system, the method is simpler in control structure and can suppress the zero-sequence current and further improve the power sending-out capability of the MMC converter station, thereby reducing the design capacity of a DC chopper, reducing the engineering construction cost, and even realizing the fault ride-through operation of the system under the condition that the DC chopper does not need to be input when the fault is relatively light. The MMC converter station low-voltage ride-through method based on resonance controllers is simple in structure and remarkable in effect and has high engineering practical value.

Description

technical field [0001] The invention relates to a low-voltage ride-through method and control system of an MMC converter station based on a resonance controller, which is suitable for 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 ba...

AI Technical Summary

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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