A method of improvement of torque limit control based on dual feedback wind turbines

Abstract

The invention discloses an improved torque limit control method based on a double-fed wind turbine, comprising the following steps: when a power system after wind power grid-connected encounters a frequency disturbance accident, the active output of the double-fed wind turbine increases instantaneously, and then the active power is increased. The output decreases as a quadratic function of rotational speed until the difference between the output electromagnetic power of the DFIG and the captured mechanical power approaches zero; then the active power of the DFIG first ramps down slowly with time, and then remains constant until it tracks the output value with the maximum power equal, and finally return to the maximum power tracking control state. The invention enables the doubly-fed fan to have a faster speed recovery speed, at the same time, it can avoid the problem of secondary frequency drop to the greatest extent, and can effectively improve the lowest point of frequency drop in different frequency responses.

Description

technical field [0001] The invention relates to the technical field of electromechanical control, in particular to an improved torque limit control method based on a doubly-fed wind turbine. Background technique [0002] In recent years, variable-speed wind turbines (WTGs), typically represented by doubly-fed induction generators (DFIGs), have become the most widely used wind turbines on the market due to their advanced control performance. The unit realizes variable speed and constant frequency control of the wind turbine through the rotor side-connected inverter to capture the maximum wind energy. However, the power electronic converter decouples the fan speed from the grid frequency, and the rotational kinetic energy contained in the rotor cannot be effectively released, making little contribution to the inertia of the power system, which will adversely affect the frequency stability. Therefore, how to let wind turbines participate in the system frequency control is the ...

AI Technical Summary

Problems solved by technology

However, since the control process only establishes the active-time relationship, ignoring the changes in rotational speed and mechanical power, it is easy to cause excessive release of rotor kinetic energy

At the same time, the inertial response capability of the fan will weaken as the speed decreases, resulting in insufficient follow-up active power during the frequency recovery process, resulting in a secondary frequency drop phenomenon

When the system frequency drops twice, it will seriously affect the power quality and affect or even destroy the production process of various departments

At the same time, it will cause great harm to the steam turbine in the power plant, causing a significant drop in the output of the thermal power plant's machinery, resulting in a reduction in the output of the generator, a lack of power, a further drop in frequency, and even a frequency collapse.

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