Variable and Fixed Switching Frequency Based HCC Methods for Grid-Connected VSI with Active Damping and Zero Steady State Error Major Electrical Projects

ABSTRACT

This paper presents variable and fixed switching frequency based hysteresis current control (HCC) methods for single-phase grid-connected voltage source inverters (VSI) with LCL filter. The main feature of the proposed HCC methods is that the reference inverter current is generated through a proportional-resonant (PR) controller for achieving zero steady-state error in the grid current. The consequence of using PR controller is eliminating the need for using derivative operations in generating the reference inverter current. Furthermore, active damping method is employed to damp the LCL resonance. An equation is derived for variable switching frequency. Fixed switching frequency operation is achieved by modulating the hysteresis band. The performance of both HCC methods has been validated by simulation and experimentally. It is reported that the proposed HCC methods not only preserve the inherent features of the conventional HCC methods, but also damp the LCL resonance using an active damping method and guarantee zero steady-state error in the grid current.

 KEYWORDS:

  1. Fixed switching frequency
  2. Grid-connected inverter
  3. Hysteresis current control
  4. Variable switching frequency.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Single-phase grid-connected VSI with the proposed HCC methods. (a) Variable switching frequency based HCC, (b) Fixed switching frequency based HCC.

Fig. 1. Single-phase grid-connected VSI with the proposed HCC methods. (a) Variable switching frequency based HCC, (b) Fixed switching frequency based HCC.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulation and experimental results of , , , and obtained by: (a) the variable switching frequency based HCC, (b) the fixed switching frequency based HCC.

Fig. 3. Simulation and experimental results of , , and obtained by: (a) the variable switching frequency based HCC, (b) the fixed switching frequency based HCC. 

CONCLUSION

In this study, variable and fixed switching frequency based HCC methods are presented for single-phase grid-connected VSI with LCL filter. Unlike the conventional HCC methods, the proposed HCC methods employ the reference inverter current generated with the PR current controller by processing the grid current error. The use of PR controller ensures zero steady-state error in the grid current independently from the hysteresis bandwidth. In addition, the need for using derivative operations in generating the reference inverter current is eliminated by using PR controller. Also, active damping method is employed to damp the LCL resonance. A formula is derived for the variable switching frequency. The fixed switching frequency operation is achieved by modulating the hysteresis band obtained from the derived variable switching frequency equation. The performances of both HCC methods are validated by experimental investigation. These results show excellent performance in terms of dynamic response, robustness, zero steady-state error, and low THD in the grid current. Hence, the proposed HCC methods not only preserve the inherent features of the HCC methods, but also damp the LCL resonance using an active damping method and guarantee zero steady-state error in the grid current.

REFERENCES

  • Blaabjerg, R. Teodorescu, M. Liserre, and A. V. Timbus, “Overview of control and grid synchronization for distributed power generation systems,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 1398–1409, Oct. 2006.
  • Abu-Rub, M. Malinowski, and K. Al-Haddad, Power Electronics for Renewable Energy Systems, Transportation and Industrial Applications. Hoboken, NJ, USA: Wiley, 2014.
  • Pena-Alzola, M. Liserre, F. Blaabjerg, R. Sebastion, J. Dannehl, and F. W. Fuchs, “Analysis of the passive damping losses in LCL-filter-based grid converters,” IEEE Trans. Power Electron., vol. 28, no. 6, pp. 2642–2646, Jun. 2013.
  • Dannehl, F. W. Fuchs, S. Hansen, and P. B. Thogersen,”Investigation of active damping approaches for PI-based current control of grid-connected pulse width modulation converters with LCL filters,” IEEE Trans. Ind. Appl., vol. 46, no. 4, pp. 1509-1517, Jul./Aug. 2010.
  • Pan, X. Ruan, C. Bao, W. Li, and X. Wang, “Capacitor-current feedback active damping with reduced computation delay for improving robustness of LCL-type grid-connected inverter,” IEEE Trans. Power Electron., vol. 29, no. 7, pp. 3414–3427, Jul. 2014.

Leave a Reply

Your email address will not be published.