Abstract
In order to improve the dynamic response speed and the steady-state performance of the DC side bus voltage of the wind power grid-connected inverter, a mathematical model of a typical three-phase voltage type PWM (Pulse Width Modulation, PWM) grid-connected inverter was established, and its traditional voltage-current double closed loop with proportional-integral control method was analyzed. Then a second-order linear active disturbance rejection controller that does not depend on system model information was designed to replace the traditional voltage outer loop proportional-integral controller, thus a new double closed-loop control structure was formed to control it. The frequency domain theory was used to analyze the convergence of the third-order linear extended state observer and the influence of the total disturbance on the performance of the third-order linear extended state observer. The parameter tuning scheme of the designed controller was given. Finally, the 1.5 MW direct-driven permanent magnet wind power generation system was built in the Matlab/Simulink software and the control effects of the two control modes under different working conditions are compared. The simulation results show that the control scheme designed in this paper is superior to the traditional proportional-integral controller which has good anti-interference characteristics and robustness. Especially it has a good stability effect on DC side bus voltage fluctuations.
Highlights
In recent years, with the continuous improvement of installed capacity of wind power generation systems, the grid-connected inverter—as an interface device directly connected with the power grid in wind power generation systems which controls performance—will directly affect the quality of output power and the operating efficiency of the system [1,2]
For the control of the DC side bus voltage of the wind power grid-connected inverter, traditional method generally adopts the double closed loop structure of the voltage outer loop and the current inner loop based on the grid voltage vector orientation [5]
The direct current signal provided by the inner loop controller is converted into an alternating current signal in stationary coordinates by coordinate transformation, and the signal is used as a pulse-triggered modulation signal, thereby realizing control of the DC side bus voltage
Summary
With the continuous improvement of installed capacity of wind power generation systems, the grid-connected inverter—as an interface device directly connected with the power grid in wind power generation systems which controls performance—will directly affect the quality of output power and the operating efficiency of the system [1,2]. For the control of the DC side bus voltage of the wind power grid-connected inverter, traditional method generally adopts the double closed loop structure of the voltage outer loop and the current inner loop based on the grid voltage vector orientation [5]. For the grid-side, a novel controller is proposed for the first time to be successfully used for the direct-drive wind energy conversion system, combining a proportional complex integral current inner loop based on stationary reference frame for regulating the grid-side current with a DC voltage outer loop for stabilizing the DC bus voltage. The wind power grid-connected inverter, as a complex system with non-linearity, multi-variable coupling and vulnerable to grid voltage fluctuations and load changes, is difficult to establish an accurate mathematical model for, which is one of the reasons for the unsatisfactory results of traditional control schemes. Mathematical Model and Traditional Control Strategy of Wind Power Grid-Connected Inverter
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