Study On High Voltage Gain Quasi Z-Source Based DC-DC Converter Using Coupled-Inductor

Photovoltaic cells in series get access to the grid through centralized photovoltaic inverter, and the utilization rate and reliability of the system is very low under the circumstance of shadow. In order to achieve Maximum power point tracking, thus improve the utilization rate of photovoltaic cell, scholars actively explore independent PV module architecture with high voltage gain converter. Therefore, DC-DC converter with high voltage gain draws a widespread attention in recent years.Quasi Z-source DC-DC converter possesses high voltage gain, and is able to achieve higher voltage gain without extreme duty cycle. The working principle and steady state analysis of the quasi Z-source DC-DC converter is fully discussed in this paper. The voltage gain of quasi Z-source DC-DC converter considering circuit parasitic is presented. Both the design procedure of circuit parameters and the converter power loss analysis are given below. Theoretical analysis shows that:(1) The quasi Z-source DC-DC converter can achieve higher voltage gain comparing to Boost converter under the same duty cycle;(2) The quasi Z-source DC-DC converter can achieve high voltage gain without extreme duty cycle, thus the reverse recovery problem of rectifier diode is alleviated. Both simulation results and experimental results verify the correctness of the theoretical analysis.Combining coupled inductor technique and quasi Z-source DC-DC converter, a high voltage gain quasi Z-source converter using coupled inductor is presented. The working principle and steady state analysis of the converter are discussed, and the design procedure of circuit parameters and power loss analysis are given in this paper. Theoretical analysis shows that:(1) The presented converter harnesses the merit of high voltage of quasi Z-source DC-DC converter, and is able to achieve high voltage gain and small duty cycle, thus the reverse recovery problem of the diode caused by extreme duty cycle is alleviated. (2) By introducing coupled inductor technique, high voltage gain can be achieved through proper design of coupled inductor ratio. Meanwhile, the voltage stress over the MOSFET is alleviated, thus the conducting power loss is reduced, which leads to the improvement of overall efficiency.(3) The leakage energy flows to capacitor through diode, thus the voltage spike over MOSFET is avoided, and no absorb circuit is needed. An experimental platform was built to verify the correctness of theoretical analysis.Combining secondary winding of coupled inductor and switched capacitor technique, a high voltage gain quasi Z-source converter using coupled inductor voltage doubler cell is presented. The working principle and steady state analysis of the converter is discussed, and the design procedure of circuit parameters and power loss analysis are given in this paper. Theoretical analysis shows that:(1) Harnessing switched capacitor, voltage gain of the presented converter is further improved, along with the voltage stress over MOSFET, thus a MOSFET with low on-resistance can be chosen to improve the overall efficiency. (2) Introducing the coupled inductor technique, the presented converter can achieve high voltage gain with extreme duty cycle, which improves voltage gain in practice. (3) Leakage inductor helps rectifier diode turnoff with zero current, which further improves the reverse recovery problem of diode, along with the overall efficiency.