Sliding Mode Control of Single-Phase Grid Connected Quasi-Z-Source Inverter

 Abstract

Quasi-Z-source inverters (qZSI) are nowadays increasingly used owing to advantages like single stage operation, lower component rating, and continuous input current, and common DC rail. These benefits lead to investigate this converter for grid connected applications. This paper presents a grid connected quasi-Z-source inverter (qZSI) with both AC and DC side control. Sliding Mode Control (SMC) based controller for capacitor voltage regulation has been proposed to ensure a fast and dynamic response for wide variations in input voltage, output load, and reference controlled quantity. A detailed mathematical model of the system is presented. A stable and fast response of SMC has been demonstrated using simulation and is validated by experimental results.

Index Terms

1. Quasi-Z-Source Inverter
2. Sliding Mode Control (SMC)
3. Grid connected system

Schematic Diagram:

Fig. 1. Proposed grid connected quasi-Z-Source Inverter with closed loop control.

Expected Simulation Results:

Fig. 2. Simulation results for step change in input voltage from 250V to 300V (a) Input voltage (b) Capacitor voltage.

Fig. 3. Simulation results for step change in capacitor reference voltage from 400V to 500V (a) Capacitor voltage (b) Grid voltage and current..

Fig. 4. Comparison of Simulation results for step change in capacitor reference voltage (a) PI Controller (b) SM Controller.

Fig. 5. Simulation results for step change in grid feed current from 0.5A to 1.5A (a) Capacitor voltage (b) Grid voltage and current.

Conclusion

In this paper, SMC is used for controlling the dynamic response of the grid connected qZSI system. The detailed mathematical analysis of the SMC is done. Various aspects of the controller, are discussed in the paper, which include the selection method of the sliding surface, and the existence condition. The simulation and experimental result shows that the capacitor voltage controller gives a very fast response to a step change in reference value. Also, the controller is stable and robust for wide variations in input and output. A comparison of the proposed controller, with the PI controller, also clearly, proves the superiority, of the SMC based controller, over the classical controller.

References

[1] F. Z. Peng, ‘‘Z-source inverter,’’ IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 504-510, 2003. [2] P. C. Loh, D. M. Vilathgamuwa, Y. S. Lai, G. T. Chua, and Y. Li, ‘‘Pulse-width modulation of Z-source inverters,” IEEE Trans. Power Electron., vol. 20, no. 6, pp. 1346-1355, Nov. 2005.

[3] M. S. Shen, J. Wang, A. Joseph, F. Z. Peng, L. M. Tolbert, D. J. Adams, “Constant Boost Control of the Z-Source Inverter to Minimize Current Ripple and Voltage Stress,” IEEE Trans. on Ind. Appl., vol. 42, no. 3, pp. 770-778, 2006.

[4] V. P. Galigekere, M. K. Kazimierczuk, “Analysis of PWM Z-source DC-DC converter in CCM for steady state,” IEEE Trans. Circuits Syst. I, vol. 59, no. 4, pp. 854–863, Apr. 2012.

[5] R. Badin, Y. Huang, F. Z. Peng, H. G. Kim, “Grid Interconnected ZSource PV System,” in Proc. IEEE PESC 2007, Orlando, FL, pp. 2328-2333, 2007.