This paper presents the small signal modeling using the state space averaging technique and reliability analysis of a three-phase z-source ac-ac converter. By controlling the shoot-through duty ratio, it can operate in buck-boost mode and maintain desired output voltage during voltage sag and surge condition. It has faster dynamic response and higher efficiency as compared to the traditional voltage regulator. Small signal analysis derives different control transfer functions and this leads to design a suitable controller for a closed loop system during supply voltage variation. The closed loop system of the converter with a PID controller eliminates the transients in output voltage and provides steady state regulated output. The proposed model designed in the RT-LAB and executed in a field programming gate array (FPGA)-based real-time digital simulator at a fixedtime step of 10 μs and a constant switching frequency of 10 kHz. The simulator was developed using very high speed integrated circuit hardware description language (VHDL), making it versatile and moveable. Hardware-in-the-loop (HIL) simulation results are presented to justify the MATLAB simulation results during supply voltage variation of the three phase z-source ac-ac converter. The reliability analysis has been applied to the converter to find out the failure rate of its different components.
 Razzaghi R., Mitjans M., Rachidi F. et al., An automated FPGA real-time simulator for power electronics and power systems electromagnetic transient applications, Electric Power System Research, vol. 141, pp. 147156 (2016).
 Higashikawa K., Urasaki S., Inoue M. et al., Hardware-in-the-loop simulation of superconducting devices for DC electric railway systems based on a real-time digital simulator, IEEE Trans. on Applied Superconductivity, vol. 26, no. 4 (2016).
 Prasad H., Maity T., Real-time simulation for performance evaluation of bidirectional quasi z-source inverter based medium voltage drives, COMPEL-The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 35, no. 3, pp. 11231135 (2016).
 Tavana N.R., Dinavahi V., A general framework for FPGA-based real-time emulation of electrical machines for HIL applications, IEEE Trans. on Ind. Electronics, vol. 62, no. 4, pp. 20412053 (2015).
 Prasad H., Maity T., Real-time performance analysis of modified z-source inverter-fed induction motor drives using xilinx system generator, EPE Journal, vol. 26, no. 4, pp. 142-152 (2016).
 Peng F.Z., Z-Source Inverter, IEEE Trans. on Ind. Appl., vol. 39, no. 2, pp. 504-510 (2003).
 Prasad H., Maity T., Singh V.K., A Simple Transformerless Buck-Boost Switching Voltage Regulator, Asian Power Electronics Journal, vol. 8, no. 2, pp. 57-61 (2014).
 Prasad H., Maity T., Singh V.K., Transformer less Voltage Regulator, IEEE International Conf. on Green Computing, Communication and Electrical Eng., pp. 1-5 (2014).
 Fang X., Three Phase Z-Source AC-AC converter, IEEE International Power Electronics and Motion Control Conference, pp. 621-624 (2006).
 Zhang F., Fang X., Peng F.Z., Qian Z., A New Three Phase AC-AC Z-Source Converter, IEEE Applied Power Electronics Conference and Exposition, pp. 123-126 (2006).
 Sonar S., Maity T., Minu M., Single phase transformerless wide range ac boost voltage regulator based on z-source network, International Journal of Electrical Power & Energy System, vol. 47, pp. 193197 (2013).
 Liu J., Hu J., Xu L., Dynamic Modeling and Analysis of z-Source converter - Derivation of AC Small Signal Model and Deigns-Oriented Analysis, IEEE Trans. on Power Electronics, vol. 22, no. 5, pp. 17861796 (2007).
 Galigekere N.V.P., Kazimierczuk M.K., Small-Signal Modeling of Open-loop PWM Z-Source Converter by Circuit-Averaging Technique, IEEE Trans. on Power Electronics, vol. 28, no. 3, pp. 12861296 (2013).
 Gajanayake C.J., Vilathgamuwa D.M., Loh P.C., Small-Signal and Signal-Flow-Graph Modeling of Switched Z-Source Impedance Network, IEEE Power Electronics Letters, vol. 3, no. 3, pp. 111116 (2005).
 Loh P.C., Vilathgamuwa D.M., Gajanayake C.J. et. al., Transient Modeling and Analysis of Pulse- Width Modulated Z-Source Inverter, IEEE Trans. on Power Electronics, vol. 22, no. 2, pp. 27822789 (2007).
 Prasad H., Maity T., Design of a Stable and Efficient Z-Source AC-AC Converter using Small Signal Analysis, IEEE Power, Communication and Information Technology Conf., pp. 190194, (2015).
 Rim C.T., Hu D.Y., Cho G.H., Transformers as Equivalent Circuits for Switches: General Proofs and D-Q Transformation-Based Analysis, IEEE Transformations on Industry Applications, vol. 26, no. 4, pp. 777785 (1990).
 Masrur M.A., Studies on the Effect of Filtering, Digitization, and Computation Algorithm on the ABC-DQ Current Transformation in PWM Inverter Drive System, IEEE Trans. on Vehicular Technology, vol. 43, no. 2, pp. 356-365 (1955).
 Galigekere V.P., Kazimierczuk M.K., Analysis of PWM z-source DC-DC converter in CCM for steady state, IEEE Trans. Circuits and Systems, Part I, regular papers, vol. 59, no. 3, pp. 854863 (2012).
 Chan N., A Generalized Reliability Function for Systems of Parallel Components, IEEE Trans. on Reliability, vol. 17, no. 2, pp. 199-201 (1968).
 Todri A., Marek-Sadowska M., Reliability Analysis and Optimization of Power-Gated ICs, IEEE Trans. on very Large Scale Integration (VLSI) Systems, vol. 19, no. 3, pp. 457-468 (2011).
 Alam M.K., Khan M.H., Reliability Analysis and Performance Degradation of a Boost Converter, IEEE Trans. on Industry Applications, vol. 50, no. 6, pp. 3986-3994 (2014).
 Military Handbook, Reliability Prediction of Electronic Equipment, Washington, DC, USA (1991).