继电器旁路的两级式光伏并网逆变器研究

Research on Two-Stage PV Grid-Tied Inverter With By-Pass Relay

针对目前两级式光伏并网逆变器存在的转换效率问题,提出一种改进型的电路拓扑,在光伏电池与母线电容之间旁接一个继电器,由光伏电池输出电压值通过滞环比较器控制继电器的通断与两种工作模式的选择。前级升压电路停止工作,主电路电流经继电器到直流母线,后级逆变器实现最大功率点跟踪和并网功能,避免了前级电路升压电感和二极管造成的损耗,提高了转换效率。Matlab仿真实验和3k W样机实验结果都验证了本改进拓扑的可行性和控制策略的有效性。

An advanced topology is introduced to improve the converting efficiency of the double-stage PV grid-tied inverter, which includes a by-pass relay between PV cell and bus capacitance. The on-off switch of relay and two working modes of the inverter are determined by the output signal of hysteresis comparator of which input signal is the voltage of PV cell. The first-stage boosted circuit stops working and the by-pass relay picks up which the current of main circuit goes through. The second-stage inverter realizes max power point tracking and grid connection, so the dissipation caused by boost inductance and diode disappears. The topology and strategy are not only realized in Matlab, but also verified in a 3kW single-phase double-stage photovoltaic grid-tied inverter.