PERFORMANCE ANALYSIS OF D-STATCOM COMPENSATOR(10)

Control of DSTATCOM by SRF Theory

Fig. 9 shows the extraction of real fundamental current component of load current by SRF theory and the performance of the DSTATCOM is controlled by SRF theory is presented in Fig. 10. The simulation is carried out for similar load changes and unbalanced conditions as of previous case. The effect of delay due to LPF used for filtering signals in d-q frame can be seen in extracted reference currents waveform in Fig. 9. The generation of voltage templates (sine and cosine) plays an important role in calculation of reference source currents. These templates are generated using PLL and therefore the tuning of PLL is crucial.

The operation of PLL slows and it also imposes some amount of delay in computation.

Control of DSTATCOM by Adaline based Algorithm

Extraction of reference currents by Adaline based current DSTATCOM is shown in Fig. 12. It can be observed that the DSTATCOM controlled by the Adaline is able to meet the load changes within one cycle of the sine wave. The advantage of the Adaline based extractor is that it requires less computation efforts and therefore the implementation of this technique is much simpler. Moreover, the inherent linearity of Adaline makes it as a fast technique. The speed of convergence can be varied by varying the value of n (convergence-coefficient).

Fig7Performance Analysis
Fig.7 : Reference current extraction using P-Q theory

Fig8Performance Analysis
Fig. 8 : Dynamic performance of DSTATCOM controlled by P-Q theory
Fig9Performance Analysis
Fig. 9 : Reference current extraction using SRF theory

Fig10Performance Analysis
Fig.10 : Dynamic performance of DSTATCOM controlled by SRF theory

Fig11Performance Analysis
Fig. 11 : Reference current extraction using ADALINE theory

Fig12Performance Analysis
Fig. 12 : Dynamic performance of DSTATCOM controlled by ADALINE theory

CONCLUSIONS

The mathematical derivation of the p-q and SRF theory has been employed to demonstrate the behavior of DSTATCOM.

An Adaline based control technique has resulted in considerable improved performance of DSTATCOM. The Adaline based technique utilizes LMS algorithm to calculate the weights, and all the calculations are performed online therefore the algorithm is able to extract reference current components in case of varying load condition which otherwise is not possible with other neural network based current extraction techniques. MATLAB based results have verified the effectiveness of these control algorithms.

APPENDIX

Voltage Source converter: DC link capacitor Cdc=1000^F, AC inductor=4mH, Ripple Filter: C=10^F and R=8Q, fs=20kHz. Supply voltage 415 V, Line frequency-50HZ

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