| At present, energy consumption of the whole world is increasing constantlywhich makes the energy crisis more and more serious. Consequently, environmentalissues are getting worse. As a result, a large number of countries exert their power toenhance the development of renewable energy in order to alleviate the aboveproblems. Solar energy which is clean, safe and inexhaustible have aroused widelyattention. In the recent years, phototvoltaic micro-inverter has been a focus of currentresearch because of its low cost and high efficiency.This paper describes the advantages, operating principles and control strategies ofswitched capacitor DC-DC converter. Moreover, switched-capacitor-based step-upresonant converter has been selected to be applied to the micro-inverter. However, thisconverter is incapable of line and load regulation which also means the maximumpower point tracking (MPPT) fails to be achieved. To elimate the disadvantage, thispaper proposes a new micro-inverter topology by combineing interleaved Boost ciruitto switched capacitor circuit.In addition, this paper presents an improved multistage variable-step method toachieve MPPT. Matlab simulation was applied to compare the characteristics ofimproved variable-step algorithm with the traditional one, this algorithm tracks themaximum power point more quickly and the steady-state performance is better.Furthermore, the algorithm can still guarantee the quickness and accuracy of MPPTwhen the environmental conditions change suddenly and tremendously.Finally, a photovoltaic micro-inverter simulation model is built to achieve theimproved MPPT algorithm, boost of the PV cell output voltage, regulation of DC-busvoltage and control of current feed into grid. Further, a110W hardware experimentplatform is set up. The voltage of power supply is30V and the DC output can beraised to334V. Both simulation and experiment can prove the feasibility of thepresented topology of micro-inverter based on switched capacitor circuit. |
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