Virtual synchronous control method and device for high-voltage direct current grid-connected island doubly-fed wind farm

Abstract

The invention relates to a virtual synchronous control method and device for island double-fed wind power plant high-voltage direct current grid connection. The method comprises the following steps: configuring a direct current power supply for a direct current bus of a DFIG wind turbine generator back-to-back converter, and adopting a vector control method of fixed alternating voltage to providestarting power supply for black starting of a high-voltage direct current system; using VSG into the control for grid connection and normal operation of a DFIG wind turbine generator, after the VSG realizes reactive voltage droop control through a rotor side converter, wherein a grid-side converter can be flexibly switched into unit power factor control, and simultaneously the direct current powersupply exits; adopting frequency regulation and correction control method, and realizing system sending end bus frequency stabilization and active balance by a rectifier; adopting batched successivestarting in the whole wind power plant, and thus realizing virtual synchronous control for island DFIG type wind power plant high-voltage direct current grid connection. The power loss and construction cost can be reduced, the stability is improved, and the method can be applied in the high-voltage direct current grid connection field of new energy resources.

Description

technical field [0001] The invention relates to the field of high-voltage direct current grid-connected new energy sources, in particular to a virtual synchronization control method and device for high-voltage direct-current grid-connected island doubly-fed wind farms. Background technique [0002] In recent years, offshore wind farms and large wind farms far from the main grid have emerged. It should be noted that, for the geographical locations of these two types of wind farms, there is no existing AC power grid to transmit the electric energy generated by them, so they can be called island wind farms. Transmitting the power generated by an island wind farm to the main AC grid is a key technical challenge. First, wind turbines based on traditional vector control can generally be equivalent to current sources, and an external voltage source is needed to assist multiple wind turbines to achieve stable operation. Second, the doubly-fed wind turbine (DFIG) has become one of ...

AI Technical Summary

Problems solved by technology

However, there are some serious deficiencies or defects in this scheme: 1) The startup process of the system and its control strategy are the prerequisites for the normal operation of the system, which must be carefully studied

It should be noted that the connection of DFIG islands to LCC-HVDC is similar to the connection of passive loads. In the absence of strong AC grid support, there is dynamic coupling between the output of the converter based on PLL vector directional control and the voltage of the common coupling point of the wind farm. relationship, which can easily lead to the risk of frequency (synchronization) instability

3) In this scheme, the vector control method of DFIG makes active power and frequency approximately decoupled, so HVDC control of the bus frequency at the sending end cannot effectively control the active power balance at the sending end, and it is also difficult to control the system frequency stability

3) Once the large-capacity STATCOM is put into operation, it must play a regulating role in real time, resulting in large power loss and operation and maintenance costs

However, it is still a blank to apply the VSG control idea to the LCC-HVDC grid-connected control strategy of the island DFIG type wind farm.

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