A Single-Phase Buck Matrix Converter with High-Frequency Transformer Isolation and Reduced Switch Count

ABSTRACT:

In this paper, a new type of matrix converter also called a single-phase high-frequency transformer  isolated (HFTI) buck matrix converter (MC) is proposed. The proposed converter can provide step-down operation of the input voltage with various types of output voltages such as; in-phase and out-of-phase output voltages, rectified (or positive) output voltage, and output voltage with step-changed frequency. By incorporating HFT isolation, the proposed MC saves an extra bulky line frequency transformer, which is required for the conventional MCs to provide electrical isolation and safety, when used in application such as dynamic voltage restorers (DVRs), etc. Two different circuit variations of the proposed HFTI MC are presented with and without  continuous output currents, with the latter having less passive components. The safe-commutation strategy is also employed for the proposed HFTI MC to provide current path for the inductor during dead-time, which avoids switch voltage spikes without adding any snubber circuits. The operation principle and circuit analysis of the  proposed MC are presented, and switching strategies are also developed to obtain various output voltages. Moreover, a prototype of the proposed MC is fabricated, and experiments are performed to produce in-phase/out-of-phase and rectified output voltages, and output voltage with step-changed frequency.

KEYWORDS:

  1. High-frequency transformer
  2. In-phase and out-of-phase operations
  3. Rectified output
  4. Single-phase matrix converter
  5. Step-changed frequency

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

In this paper, a buck MC is proposed with HFT isolation. The proposed MC is capable of providing various types of output voltages, such as in-phase, out-of-phase and rectified output voltages. Moreover, the frequency of the output voltage can be changed in steps, so that it is integer multiple or integer fraction of the input voltage frequency. The use of HFT isolation in the proposed MC for electrical isolation and safety benefits in that it removes the need for extra bulky line frequency transformer, which is added with conventional non-isolated MCs for applications as DVRs.

Two different secondary side structures of the proposed HFTI buck MC are proposed, with one having continuous output current, and the other having discontinuous out current but with one inductor and capacitor less. The soft-commutation strategy is suggested for the proposed MC, which avoids switch voltage spikes without using any snubber circuits. The operation principle and circuit analysis of the proposed converter are presented and switching strategies are also developed to obtain various output voltages. Moreover, a 200 W laboratory prototype of the proposed MC is fabricated, and experiments are performed to produce in-phase/out-of-phase and rectified output voltages, and output voltage with step-changed frequency.

REFERENCES:

[1] F. Z. Peng, L. Chen, and F. Zhang, “Simple topologies of PWM ac-ac converters,” IEEE Power Electron. Letters, vol. 1, no. 1, pp. 10– 13, Mar. 2003.

[2] T. B. Lazzarin, R. L. Andersen, and I. Barbi, “A switched-capacitor three-phase ac-ac converter,” IEEE Trans. Ind. Electron., vol. 62, no. 2, pp. 735–745, Feb. 2015.

[3] H. F. Ahmed, H. Cha, A. A. Khan, and H.-G. Kim, “A family of high-frequency isolated single-phase Z-source ac-ac converters with safe-commutation strategy,” IEEE Trans. Power Electron., vol. 31, no. 11, pp. 7522–7533, Nov. 2016.

[4] C. Liu, B. Wu, N. R. Zargari, D. Xu and J. Wang, “A novel three-phase three-leg ac-ac converter using nine IGBTs,” IEEE Trans. Power Electron., vol. 24, no. 5, pp. 1151–1160, May. 2009.

[5] C. B. Jacobina, I. S. d. Freitas, E. R. C. d. Silva, A. M. N. Lima, and R. L. d. A. Riberio, “Reduced switch count dc-link ac-ac five-leg converter,” IEEE Trans. Power Electron., vol. 21, no. 5, pp. 1301–1310, Sep. 2006.

 

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