Control method for eliminating DC harmonic voltage for grid-side converter of double-fed wind power generator

Abstract

The invention discloses a method for eliminating DC harmonic voltage for the grid-side converter of a double-fed wind power generator in the case of asymmetric power grid. The method adopts a phase-shift T / 4 delay negative sequence fast separation method, which performs positive-negative sequence separation on the voltage and current of the three-phase power grid, wherein the positive-negative sequence separation method has simple calculation which only includes addition, subtraction, multiplication and division, fast response that the positive-negative sequence component can be worked out only in 5 m and small delay which facilitates the design of PI parameters. In order to obtain good control effect, the positive-negative double-dq current control with completely symmetric structure is adopted. Therefore, the positive-negative sequence current instructions are both DC components and the PI regulator can realize floating control.

Description

technical field [0001] The invention belongs to the field of grid-side converter control strategies in the field of wind power generation, and in particular relates to a method for eliminating DC voltage harmonics under the condition of voltage asymmetry. Background technique [0002] With the deterioration of the earth's environment and the shortage of energy sources, the development of new energy sources is particularly important. Among the current new energy sources, wind power has the most mature technology and the cost closest to conventional energy sources. It has developed rapidly in recent years and played an important role in alleviating the increasingly serious energy crisis and environmental pollution. The current mainstream wind turbine model is double-fed variable-speed constant-frequency wind turbines, which have been widely used due to their advantages such as adjustable power factor, high efficiency, and small capacity of converter devices. [0003] In doubl...

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Problems solved by technology

In the literature "Research on the Control Strategy of PWM Rectifier under Unsymmetrical Power Grid Fault" (Master's Thesis of Zhejiang University, 2006.07.), the positive and negative sequence components are separated, but only the positive sequence components are considered in the positive sequence synchronous rotating coordinate system, and the establishment of control model, and did not propose a method for separating positive and negative sequence components

The document "VSC transmission operating under unbalanced AC conditions-analysis and control design" (IEEE Transactions On Power Delivery, 2005, 20(1): 427-434.) based on instantaneous active power and reactive power, for two sequence Two different control strategies are used for the component and the DC side voltage, so that the steady-state voltage ripple can be eliminated, but these two control strategies can only operate under steady-state conditions

The control strategy proposed in the document "PWM Rectifier and Its Control" (Mechanical Industry Press, 2003: 478.) can operate under asymmetrical grid conditions, but does not involve negative sequence components in the control strategy, which is precisely to reduce variable The only way to fluctuate the dc voltage of the rectifier

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