Abstract
In the permanent magnet direct-drive wind power grid-connected system, in order to solve the coupling problem between d -axis and q -axis currents and to improve the disturbance rejection performance of direct current (DC) bus voltage under grid faults, a new dual closed-loop structure based on linear active disturbance rejection control (LADRC) is proposed. This new dual closed-loop control includes current inner loop decoupling control and DC bus voltage outer loop control with first-order LADRC. As the LADRC has the advantages of decoupling and disturbances rejection, it is applied to the control of wind power grid-connected inverter. Through analysis, it is demonstrated that the current decoupling control is simpler than proportional integral (PI) control algorithm, the dynamic response speed is faster, and the DC bus voltage control has better anti-disturbance. Finally, a 1.5 MW direct-drive permanent magnet wind power system was established through digital simulation, and the control effects of the two control modes under different working conditions are compared. The simulation results verify that the proposed dual closed-loop control based on first-order LADRC is superior to PI double closed-loop control in terms of decoupling performance and disturbance rejection performance under grid faults.
Highlights
At present, the contradiction between the increasing power demand, the shortage of energy supply, and the deteriorating environmental problems makes traditional power generation methods face severe challenges [1,2]
In the control of grid-side converter of the wind power system, the outer loop is adjusted according to the error between the feedback of direct current (DC) bus voltage and the given value to stabilize the DC bus voltage
It is concluded that the decoupling control of the current inner loop of three-phase inverter is based on the feedforward control algorithm, that is to say, the proportional integral (PI) regulation results of each axis current contain other axis current information, the injected component and the coupling amount generated by the control object are the same, and the direction is opposite
Summary
The contradiction between the increasing power demand, the shortage of energy supply, and the deteriorating environmental problems makes traditional power generation methods face severe challenges [1,2]. The control effect of the grid-connected inverter directly affects power quality output from wind turbines. Double closed-loop structure is usually applied to grid-connected control of grid-side converter in wind power system, that is, voltage outer loop control and current inner loop control [7]. Energies 2020, 13, 1090the actual wind power grid-connected inverter system is a complex system 3that of 22 is nonlinear, strong coupling, multivariable, and easy to be affected by the grid voltage fluctuation [23] It isItdifficult to establish an accurate mathematical model, whichwhich leads leads to theto unsatisfactory control control effect the traditional method. By controlling the DC quantities, the AC quantities can be controlled, which brings convenience to the analysis and design of the system
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