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Coordinated Control Of Dual PWM Converters For VSCF Wind Energy Generation

Posted on:2005-03-08Degree:MasterType:Thesis
Country:ChinaCandidate:C LuFull Text:PDF
GTID:2132360122997793Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
Compared with conventional cycloconverters, dual PWM converters have better input and output performances, less harmonic currents and a wider frequency adjustment range. The rotor-side converter is responsible for maximal wind energy capturing and independent regulation of reactive power output from the stator of the doubly-fed induction generator (DFIG) through vector control. The grid-side converter diverts the rotor power to or from the grid using a DC-link between the two converters. Large aluminum electrolytic capacitors are normally installed to reduce the DC-link voltage fluctuation. But the aluminum electrolytic capacitor has several drawbacks from the viewpoints of size, weight, cost, and reliability which bottlenecks the lifespan extension of the whole system. In this thesis, a novel coordinated control strategy is proposed to minimize the DC-link capacitor.Firstly, based on the analysis of the dynamic mathematical model of DFIG and its stator-flux-oriented vector control, a dual-closed-loop PI control scheme is developed and realizes decoupled control of the active and reactive power. Simulation study is carried out on the platform of MATLAB/SIMULINK?and validates the proposed strategy, which will guide designing and debugging the practical software and hardware systems.Secondly, the mathematical model of the three-phase PWM converter in d-q synchronous reference frames is thoroughly investigated. Comparative simulation study is carried out to evaluate the performance of the non-coordinated control with current state decoupling and grid voltage feed-forward compensation, coordinatedcontrol with load current feed forward, and the proposed novel coordinated control strategy. Simulation results demonstrates the superiority of the novel coordinated control strategy over its counterparts in less DC-link voltage fluctuation and faster stabilization. Thus smaller capacitor can be adopted with the same fluctuation voltage allowed, which counts a great deal in practical applications.Lastly, DSP software is implemented on the laboratory prototype of a three-phase PWM converter. Experimental results show that three-phase PWM converters are advantageous in high power factor, small input-line current harmonic distortion and bi-directional power flow. Furthermore, the validity and superiority of coordinated control with load current feed forward are experimentally verified featuring faster DC-link voltage regulation and power balancing with smaller voltage fluctuation and faster recovery.
Keywords/Search Tags:VSCF wind energy generation, vector control, dual PWM converter, coordinated control
PDF Full Text Request
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