Method of improving identification precision of speedless sensor under condition of unbalanced network voltage

Abstract

The invention relates to a method of improving identification precision of a speedless sensor under the condition of unbalanced network voltage. The method comprises the steps that a wind power generator controlled by a double-fed control system is adopted; when the network voltage is in a balanced state, stator voltage and stator current serve as an input of an MRAS (Model Reference Adaptive System) reference model directly; and rotating speed data is obtained after PI (Proportional-Integral) adaptive rotating speed estimation. An improvement of the method is that when the network voltage is in an unbalanced state, negative sequence components of the voltage and the current due to unbalance of the network voltage are removed from the input quantity of the MRAS reference model. The method has the technical benefits that the speedless sensor meets a control requirement that the power generator works in the slight unbalanced state of the network voltage; the identification precision of the speedless sensor on the rotating speed in the unbalanced state of the network voltage is improved; an application scope of the speedless sensor is expanded; and fault toleration control of the double-fed wind power generator during a fault of a speed sensor is achieved.

Description

technical field [0001] The invention relates to a doubly-fed wind power generator control technology, in particular to a method for improving the identification accuracy of a speed sensor under the condition of unbalanced grid voltage. Background technique [0002] At present, the doubly-fed wind generator (DFIG) has become the mainstream model of megawatt-scale wind turbines due to its advantages of variable speed and constant frequency power generation; in the doubly-fed wind generator control system, the rotor speed signal is the The important parameters of machine vector control play a vital role in the control system, therefore, obtaining accurate speed data is of great significance for doubly-fed wind turbine control. [0003] In the prior art, the means used to obtain the generator speed generally include speed sensors such as optical code discs and speed sensors that conduct online observation of the speed signal through calculation; based on high-performance hardwar...

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Problems solved by technology

[0004] In the actual power system, wind turbines need to be able to run for a long time under the condition of slight unbalanced grid voltage and short-term operation when the grid voltage suddenly drops severely; at present, in the fault diagnosis and control design of the sensor, there is no Considering the reality of the grid voltage imbalance (this is due to the relatively small impact of the grid voltage imbalance on the speed sensor), compared to the speed sensor, the speed sensorless speed based on the model reference adaptive system (MRAS) The identification accuracy is more easily affected by the negative sequence component in the grid voltage unbalance

In MRAS-based speed identification, the basic requirement for the reference model is to be accurate, because the reference model is used as the benchmark for MRAS control, and only when the reference model is accurate can the sensorless speed sensor obtain a more credible identification value. In the existing technology, because the actual situation of the unbalanced grid voltage is not considered, the input of the MRAS reference model is not specially processed, resulting in the voltage and current input of the MRAS reference model containing both positive sequence components and negative sequence components; In actual operation, even small negative-sequence voltage and current components will cause large errors in online observation of rotational speed signals based on MRAS-based speed sensors (this is also a non-negligible problem in the research of double-fed wind turbines without speed sensors). an important question)

If the grid voltage is unbalanced, it is difficult to obtain accurate speed observation values ​​for double-fed wind turbines alone without speed sensors, which will directly affect the operation of the entire unit, and even lead to system instability in severe cases. Therefore, under unbalanced grid voltage , in the speed identification of double-fed wind turbine based on MRAS speed sensor, how to avoid the influence of speed identification accuracy by negative sequence voltage, current component and even harmonic interference component, and improve the identification accuracy of speed sensorless, this is the speed sensorless Issues to be solved in the study

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