Z源逆变器光伏发电系统变量调制范围随动的两级控制研究

Z源逆变器光伏发电系统是一种具有升/降压功能的单级系统,可以通过调节直通占空比实现前级光伏电池的最大功率跟踪（MPPT）控制,然后由逆变器调制因子m实现并网控制.提出了一种直通占空比调制范围上限随动的两级控制策略.该策略兼顾了两级控制和单级控制的优点：充分利用了直通零矢量,使逆变器的调制因子m增大,直流电压利用率高,相应的有源器件的电压应力和逆变器输出电流谐波得到很大地改善;消除了光伏电池和电网之间的影响.仿真和实验结果验证了理论分析的正确性与实用性.

Two-Stage Control Strategy with Variable Shoot-Through Duty Cycle Maximum Range on Z-Source Inverter PV System

The Z-source inverter photovoltaic system is a single-stage system, which has buck/boost characteristic. It achieves the maximum power point tracking （MPPT） with the control shoot-through duty cycle and fulfills the grid-connection with the modulation index m. A two-stage control technique for the Z-source inverter based on the PV system, with variable shoot-through duty cycle maximum range, has been presented. The output voltage of the Z-source inverter with the proposed control method can faithfully follow the reference voltage regardless of the variable dc-link input voltage. With the proposed control technique, the modulation index rn increases. Thus, the dc-link input voltage has been fully utilized, the voltage stress of the active devices and the harmonics in the output current of the inverter have been improved greatly, and the confrontation between the PV output power MPPT and grid has been eliminated. The theoretical analysis is verified by simulation and experimental results.