Abstract
For improving the performance of a doubly fed induction generator (DFIG) system under a harmonically distorted grid, this paper proposes a coordinated control strategy which is effective for grid inter-harmonics as well as grid integer harmonics. In order to suppress the negative impacts caused by grid harmonics, including inter-harmonics, this paper introduces an additional harmonics suppression controller, which contains a Chebyshev high-pass filter and a modified lead element considering the delay compensation. The proposed controller is employed in the rotor side converter (RSC) and grid side converter (GSC). Based on the proposed harmonics suppression controller, a coordinated control strategy between RSC and GSC is developed, in which the control targets, including the sinusoidal output current, constant power, or steady generator torque, can be achieved for DFIG, while GSC is responsible for maintaining the sinusoidal total current to guarantee the power quality of the grid connection. The effectiveness of the proposed method is verified by the theoretical analysis, and the experimental results derived using a 1 kW DFIG system validate the correctness of the theoretical analysis.
Highlights
Due to the usage of power electronics devices and non-linear loads [1,2,3,4], harmonics is a subsistent problem in power grid
For guaranteeing that doubly fed induction generator (DFIG) have the capability of covering generator performance and power quality simultaneously, this paper develops a collaborative control for DFIG system based on the improved harmonics suppression controller
The existing controller for harmonics suppression is based on resonator basically, the resonator is only valid at the fixed frequency so the existing methods are invalid for the inter-harmonics
Summary
Due to the usage of power electronics devices and non-linear loads [1,2,3,4], harmonics is a subsistent problem in power grid. The grid codes indicate that the distortions in the output current have to be limited for DFIG system with the connection to grid [2,3], in which the harmonic components between the third and. For the operation of DFIG system under 5th and 7th orders grid harmonics, the traditional method based on phase sequence decomposition has the disadvantages of the inevitable control delay and complicated calculation. To overcome this problem, multi-PI [5], PR or PIR [6], and direct resonant control (DRC) [7] have been developed to replace the traditional method. The nonlinear control methods include model predictive control and sliding
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