SUPPRESSION OF THE DC COMPONENT IN GRID INJECTION CURRENT FOR PHOTOVOLTAIC GRID-TIED INVERTERS

Do Thanh Hieu; Tran Xuan Tien; Nguyen Van Nhan; Ngo Van Tuan

Do Thanh Hieu Hung Yen University of Technology and Education
Tran Xuan Tien Hung Yen University of Technology and Education
Nguyen Van Nhan Hung Yen University of Technology and Education
Ngo Van Tuan Hung Yen University of Technology and Education

Keywords: Grid-tied inverter, DC component, Harmonics, Low pass filter

Abstract

This work deals with identifying the main causes of DC component appearance by analyzing the relationship between the DC component in grid injection current and the deviation existing in sampling value of AC voltage and AC current. Then the DC component is separated through a low-pass filter circuit. The DC component is eliminated by an appending closed-loop control. Simultaneously, a high pass filter (HPF) is introduced to filter sampling voltage value, which suppressed the deviation of the sampling voltage value. In addition, the phase delay existing in the current loop, which improves the power factor, will be compensated by the phase leading of the HPF. Eventually, the effectiveness of the proposed method is verified through the test of the total harmonic distortion (THD) index, the power factor, and the DC component index of the grid-injection current under different load conditions.

References

Kerekes, T., Teodorescu, R., Rodriguez, P., Vazquez, G., and Aldabas, E., A New High-Efficiency Single-Phase Transformerless PV Inverter Topology. IEEE Transactions on Industrial Electronics, 2011, 58, pp. 184-191.

Infield, D. G., Onions, P., Simmons, A. D. and Smith, G. A., Power quality from multiple grid-connected single-phase inverters. IEEE Transactions on Power Delivery, 2004, 19, pp. 1983-1989.

Blewitt, W. M., Atkinson, D. J., Kelly, J. and Lakin, R. A., Approach to low-cost prevention of DC injection in transformerless grid connected inverters. IET Power Electronics, 2010, 3, pp. 111-119.

AS 4777.2, Grid connection of energy system via inverters Part 2: inverter requirements Australia. 2002.

IEEE 929-2000, IEEE Recommended Practice for Utility interface of photovoltaic (PV) Systems, 3 April, 2000.

González, R., López, J., Sanchis, P. and L. Marroyo, Transformerless inverter for single-phase photovoltaic systems. IEEE Trans. Power Electron., 2007, no. 2, pp. 693-697.

Guo, X., Wu, W., Herong, W. and G. San, DC injection control for grid-connected inverters based on virtual capacitor concept. Proc. IEEE Electrical Machines and Systems Conf., Wuhan, China, 2008, pp. 2327-2330.

Armstrong, M., Atkinson, D. J. C., Johnson, M. and T. D. Abeyasekera, Auto-calibrating DC link current sensing technique for transformerless, grid connected, H-Bridge inverter systems. IEEE Trans. Power Electron, 2006, 5, pp. 1385-1393.