单相双级式光伏并网逆变器

Single-phase double-stage photovoltaic grid-connected inverter

分析了单相双级式光伏并网系统的工作原理,使用直流电源加可变电阻来模拟太阳能电池的输出特性曲线,并对其可行性进行了理论分析。提出了一种改进的变步长占空比扰动法,提高了系统的快速性和高效性。详细分析了以DSP为核心的单相光伏并网逆变器的并网策略,设计了并网逆变器的电压、电流双闭环控制系统。其中外环为直流电压控制,控制并网逆变器直流输入端电压稳定;内环为并网电流控制,控制并网逆变器的输出电流与电网电压同频、同相。在锁相跟踪控制中,提出了一种软硬件相结合的改进方法,可有效提高跟踪锁相的精度。实验结果表明所设计的并网逆变器能够实现最大功率点跟踪,并能实现输出电流精确跟踪电网电压,功率因数可达0.998。

The working principle of single-phase double-stage photovoltaic grid-connected inverter is analyzed.DC power supply with variable resistor is used to simulate the characteristic curve of solar cell output and its feasibility is analyzed theoretically.An improved duty ratio perturbation method with variable step is introduced to improve the rapidity and efficiency of system.The grid-connection strategy of DSP-based inverter is analyzed in detail and its double close-loop control is designed.The outer DC voltage control loop is to keep DC input voltage stable and the inner grid current control loop is to ensure the output current have the same frequency and phase angle of grid voltage.The software-hardware combined phase locked tracking is presented to improve its accuracy.The experimental results show that the designed inverter tracks the maximum power point quickly and the output current tracks grid voltage accurately.Its power factor is up to 0.998.