采用Boost的两级式光伏发电并网逆变系统

Boost-based Two-level Grid-connected Photovoltaic Inverter System

在光伏并网发电中,为了提高效率,必须实行最大功率点跟踪,而为了实现并网,直流侧电压必须高于电网电压幅值,这就限制了光伏电池电压的调节范围。对一种单相光伏发电并网逆变系统进行了研究,它由Boost DC/DC电路和逆变桥组成。前级Boost斩波电路则通过调节占空比而改变光伏阵列的输出电压,实现最大功率点跟踪;后级逆变电路采用电压外环,电流内环的双环控制方法,电压外环控制逆变侧电容电压的稳定,电流内环控制并网电流实现并网。在这种系统中,最大功率点跟踪和并网是相互独立的,互不干扰,使整个系统更加灵活可靠。主要研究了逆变系统各重要元件参数的选取方法以及逆变系统的控制方法。最后用MatlabR2007a/Simulink进行了仿真,证明了该逆变系统的可行性。

In grid-connected photovohaiC （PV） system, maximum power point tracking （MPPT） for PV modules must be executed to achieve higher efficiency. For grid connecting, the dc voltage of the inverter must be higher than the amplitude of grid voltage which restricts the output voltage of PV modules. Consequently, a grid-connected photovohaic inverter system is researched. The inverter system is composed of a Boost DC/DC chopper in series with an inverter. The boost chopper changes the output voltage of the PV array by adjusting the duty cycle, by which the MPPT was achieved. The controller for the inverter system contains inner current loop and external volt- age loop. The external loop stabilizes the voltage of the capacitor of the inverter, while the inner current loop controls the grid-connecting current. The MPPT and the control of the grid-connected inverter are independent from each other which make the PV system more flexible and reliable. The design of main component＇s parameters and the control strategy for the inverter system is also presented. The simulation in MatlahR2007a/Simulink confirms the effectiveness of the inverter system.