The Study In Photovoltaic Grid Connected Inverter

With worldwide lack of energy sources and worsening of ecosystem environment, many countries around the world are actively searching for a new energy source that is continuable development and taintless. Solar source is much accounted of for its particular. Among the application of solar source, the grid-connected photovoltaic generates electricity technique have become the most prospected, turn to the main form of the solar photovoltaic application. As a necessary part of photovoltaic grid-connected system, the inverter has became the hotspot in power electronics field.A novel single phase buck-boost grid-connected inverter is presented for photovoltaic generation. The inverter consists of a buck-boost converter and a thyristor bridge inverter operated at the line frequency. It has the simple structure and low cost. The novel inverter needs only one high frequency devices and can get a good output waveform. Much less switching devices are used in the new structures compared with the existent structures. The control scheme is based on one cycle control. Low current distortion and unity-power-factor are achieved in the control loop. This article mainly discusses following topics:(1) Analyzing the principle of the new structure of buck-boost inverter in detail, deducing circuit structure in different switch states from equivalent circuits. Applying one-cycle control in the new inverter, and concluding the control function based on one-cycle control under the following conditions for unity power factor on the output a.c.side.(2) The fundamental one-cycle control function is a linear equation. The control equation deduced in second chapter is a quadratic equation. So, one-cycle control added a integration reset circuit .(3) A novel three phase buck-boost grid-connected inverter is presented for photovoltaic generation. The article analyzed the principle of three phase buck-boost inverter in detail, deduced control function similarly with the single phase. Finally the simulation waveforms were given to prove the validity of the theory analysis.(4) The maximum power point tracking (MPPT) control is a necessary part of photovoltaic grid-connected system. First, the article introduced the reason of MPPT, then introduced the ways to track maximum power point such as P&O algorithm, incremental conductance algorithm. In the second chapter, the control equation deduced...