An Improved DC-Link Voltage Control Strategy for Grid Connected Converters

 ABSTRACT:

This paper presents a robust control strategy to improve dc-link voltage control performances for Grid connected Converters (GcCs). The proposed control strategy is based on an adaptive PI controller and is aimed to ensure fast transient response, low dc-link voltage fluctuations, low grid current THD and good disturbance rejection after sudden changes of the active power drawn by the GcC. The proportional and integral gains of the considered adaptive PI controller are self-tuned so that they are well suited with regard to the operating point of the controlled system and/or its state. Several simulation and experimental results are presented to confirm and validate the effectiveness and feasibility of the proposed dc-link voltage control strategy.

KEYWORDS:

1.      DC-link voltage control

2.      adaptive PI controller

3.      Grid connected Converters

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1. Commonly used control structure for Grid-connected Converters

 EXPECTED SIMULATION RESULTS

Fig. 2. Simulation results (ξ=0.7, Vdc init=100V, Vdc

*=150, i=0 at t=0s and i=Imax at t=0.5s) (a) Comparison between standard PI control and adaptive PI control  (b) waveform of the selected ωn value for the adaptive PI controller

CONCLUSION:

This paper presented an improved dc-link voltage controller based on an adaptive PI controller with an anti-windup process. The proportional and integral gains of the proposed PI controller are self-tuned so that the following constraints are satisfied: 1) no overshoot after step jumps of the dc-link voltage reference input; 2) fast dynamic response after step jumps of the dc-link voltage reference; 3) fast dynamic response after step jump of the input current i and 4) low grid current THD value during steady state operation. The considered control was experimentally tested on a prototyping platform. The obtained experimental results are quite similar to simulation results and show the effectiveness and reliability of the adopted control strategy.

REFERENCES:

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