Real time control of shunt active power filter under distorted grid voltage and unbalanced load cond

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ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in

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Real-time control of shunt active power filter under distorted grid voltage and unbalanced load condition using self-tuning filter ABSTRACT: In this paper, an alternative control method is proposed to improve the harmonic suppression efficiency of the active power filter in a distorted and an unbalanced power system to compensate for the perturbations caused by the unbalanced nonlinear loads. The proposed method uses a self-tuning filter (STF) to process the grid voltage in order to provide a uniform reference voltage to obtain the correct angular position of the phase locked loop. Moreover, the required compensation currents are obtained by implementing another STF in the transformed set of currents in order to separate the fundamental and the harmonic currents. This allows the calculation of a precise reference current for the unbalanced, the non-linear and the variable load conditions. The proposed control method gives an adequate compensating current reference even for a nonideal voltage and unbalanced current conditions. The real-time control of the filter under the distorted and the unbalanced power system is developed in an RT-LAB real-time platform. The results obtained in the software-in-the-loop configuration are presented to verify the effectiveness of the proposed control technique.

SOFTWARE: MATLAB/SIMULINK

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0-9347143789/9949240245 BLOCK DIAGRAM:

Fig. 1 Block diagram of the APF and the proposed control method

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EXPECTED SIMULATION RESULTS:

Fig. 2 Voltage and the current waveforms a Ideal grid voltage b Non-ideal (distorted and unbalanced) grid voltage c Load currents under the ideal grid voltage d Load currents under the non-ideal grid voltage

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Fig. 3 Compensation of the grid current harmonics by using the conventional dq method a Under the ideal voltage b Under the non-ideal voltage, and by using the conventional pq method c Under the ideal voltage d Under the non-ideal voltage

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Fig. 4 Compensation of the grid current harmonics a By using the STF-based pq theory under the ideal voltage b By using the STF-based pq theory under the ideal voltage c By using the proposed method under the ideal voltage d By using the proposed method under the non-ideal voltage

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0-9347143789/9949240245 CONCLUSION: In this paper, the design of a control method that generates the correct reference current signal in order to satisfy the requirements of a harmonic suppression and a reactive power compensation, for the unbalanced non-linear load combinations under the case of the non-ideal grid voltage conditions have been discussed. An alternate method is proposed where two STF are applied to manage the distorted and the unbalanced voltage and current. In the proposed method, the distorted and the unbalanced voltages are first processed by using the STF to determine the correct angular positions. Then, a second STF is used to extract the balanced load current waveforms. This method eliminates the need for additional low-pass or high-pass filtering when extracting the harmonic components from the fundamental. A step-by-step performance study, in a real-time environment, shows that the proposed control technique is able to generate the proper compensating reference current during the steady state and the dynamic load change conditions under the distorted and the unbalanced grid voltage conditions.

REFERENCES: 1 Sasaki, H., Machida, T.: ‘A new method to eliminate AC harmonic currents by magnetic flux compensation-considerations on basic design’, IEEE Trans. Power Appar. Syst., 1971, PAS-90, (5), pp. 2009–2019 2 Gyugyi, L., Strycula, E.C.: ‘Active AC power filters’. Proc. IEEE Ind. Appl. Ann. Meeting, 1976, vol. 19-C, pp. 529–535 3 Singh, B., Al-Haddad, K., Chandra, A.: ‘A review of active filters for power quality improvement’, IEEE Trans. Ind. Electron., 1999, 46, (5), pp. 960–971 4 Mariun, N., Alam, A., Mahmod, S., Hizam, H.: ‘Review of control strategies for power quality conditioners’. National Power and Energy Conf. Proc., PECon 2004, 29–30 November 2004, pp. 109–115

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ELECTRICAL PROJECTS USING MATLAB/SIMULINK Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in

0-9347143789/9949240245 5 Akagi, H., Kanazawa, Y., Nabae, A.: ‘Instantaneous reactive power compensators comprising switching devices without energy storage components’, IEEE Trans. Ind. Appl., 1984, IA-20, (3), pp. 625–630

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