Dynamic speed protection method and system for double-fed fan virtual inertia frequency modulation

Abstract

The invention discloses a dynamic rotating speed protection method and system for virtual inertia frequency modulation of a doubly-fed fan. The method comprises the steps that an MPPT curve power reference value is obtained according to the rotating speed of the fan; performing virtual inertia control on the deviation between the actual frequency and the rated frequency to obtain an additional active reference signal added on the basis of the MPPT curve power reference value; performing dynamic rotation speed protection on the fan electromagnetic power actually output at the previous moment, the rotation speed of the fan and the product of delta f and the virtual inertia control differential coefficient to obtain output power; According to the power reference value, the extra active powerreference signal and the output power, obtaining the electromagnetic power output by the fan at the current moment. The output power of the fan can slowly drop to the maximum power tracking curve according to the change of the rotating speed of the rotor in the frequency modulation process, excessive reduction of the rotating speed of the fan is avoided, the fan can automatically recover to the original maximum power point after frequency modulation is finished, and therefore the stability and economical efficiency of the fan in the frequency modulation process are guaranteed.

Description

technical field [0001] The invention relates to the technical field of virtual inertia frequency modulation, in particular to a dynamic speed protection method and system for double-fed fan virtual inertia frequency modulation. Background technique [0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art. [0003] The rotor speed of Doubly-Fed Induction Gen-erator (DFIG) is decoupled from the system frequency and cannot respond to changes in system frequency. Large-scale DFIG units connected to the grid will inevitably weaken the frequency stability of the system. Therefore, the power grid guidelines of many countries require that the wind turbines connected to the grid must have certain frequency modulation capabilities. In this regard, scholars at home and abroad have conducted a lot of research and proposed a series of wind power frequency modulation control strategies. Thes...

AI Technical Summary

Problems solved by technology

The speed limit protection strategy proposed by the existing technology can make the fan speed directly exit the frequency regulation when the speed reaches its lower limit of 0.7pu, avoiding the excessive drop of the speed, but this strategy can easily cause the secondary drop of the system frequency

In response to this problem, two control methods have been proposed in the literature: one is to modify the power curve form of the fan after it exits frequency modulation, to replace the original Maximum Power Point Tracking (MPPT) mode, to avoid a large power drop, However, this method increases the difficulty of the design of the exit curve, and greatly prolongs the recovery time of the fan speed; another method is to control the speed to make the fan run at a new stable point, so that the fan does not have to quit frequency regulation, avoiding The lower limit of the speed is reached, which directly prevents the secondary frequency drop. However, after the frequency returns to stability, the wind turbine will deviate from the MPPT operating point, and the maximum utilization of wind energy cannot be realized, which reduces the economic performance of the wind farm.

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