無電流感測最大功率追蹤之交錯返馳式光伏能量轉換系統

Interleaved Flyback Inverter Controlled by Sensorless Current MPPT for Photovoltaic Energy Conversion System

本文提出無電流感測最大功率追蹤之交錯返馳式光伏能量轉換系統，此為一市電並聯型直流／交流太陽能轉換器，其具控制較簡單及隔離之特性。返馳式轉換器以正弦脈波寬度調變 （sinusoidal pulse-width modulation, SPWM） 訊號來控制，並聯交流輸出側以一全橋式架構做低頻切換，實現此太陽能轉換器具單功因交流電流輸出。為降低輸出電流之漣波，分散開關元件承受之應力，提升轉換效率，並改善散熱問題，本文採用交錯返馳式轉換器，能使太陽能轉換器散熱更加容易，並減少輸出濾波電感和濾波電容值。為降低轉換器電路之體積及成本，提出一無電流感測器最大功率追蹤方式，不需使用傳統最大功率追蹤 （maximum power point tracking, MPPT） 所需之電流感測元件，而以太陽能輸出之電壓與估算導通週期來計算太陽能電池之輸入功率，以達成最大功率追蹤之目的。

This paper presents an interleaved flyback inverter controlled by asensorless current maximum power point tracking (MPPT) for Photovoltaic(PV) energy conversion system. The small PV system adopts a DC/ACinverter in parallel with an AC grid. The PV system has a simple controllerand galvanic isolation characteristics. The flyback converter uses sinusoidalpulse-width modulation (SPWM) to control, and operates in discontinuousconduction mode. The output of the flyback converter through a full bridgeswitch controlled by utility frequency is connected in parallel with the AC grid to achieve a single phase AC sinusoidal current output. In order todecrease the output current ripple, disperse switch stress, increase conversionefficiency and improve the heat dissipation problem, the interleaved flybackconverters are used to render heat dissipation easier and reduce the values ofthe output filter inductor and filter capacitor. Furthermore, in order toreduce circuit size and cost of the small PV, the MPPT of the PV systemadopts the sensorless current method. The sensorless current MPPT utilizesestimating the PV power by measuring the PV voltage and calculating theduty cycle to achieve the MPPT function.