基于有源钳位的无变压器型单相光伏并网逆变器

An Active Voltage Clamp Transformerless Inverter for Single-Phase Photovoltaic Grid-Connected Systems

为了抑制无变压器型光伏并网系统中的高频共模漏电流,传统的无变压器型逆变拓扑通常在并网电感续流阶段切断交流侧与直流侧的电气连接,减少共模电压的高频脉动。但是,由于系统的共模电压在并网电感续流阶段处于悬浮状态,受到共模回路的电路寄生参数的影响,不可避免地引起高频共模漏电流。本文从漏电流抑制原理出发,提出了一种新型的无变压器型单相光伏并网逆变电路,该电路通过将并网电感续流阶段的共模电压钳位至母线电容中点的方式,消除系统共模电压扰动,从而有效抑制系统的共模漏电流。此外,该电路的器件损耗低,可以获得较高的电能转换效率。文中详细分析了电路的几种工作模态,给出了一种适用于该电路的PWM控制方法。同时,通过理论分析,将该电路与已有的拓扑进行了性能比对。最后,搭建了2k W的实验原理样机,验证了该电路在光伏并网系统中的有效性。

The DC-AC decoupling technique is usually adopted in conventional transformerless photovoltaic inverter to suppress the leakage current induced by the common-mode voltage variation. However, the leakage current still exists due to the existence of the parasitic parameters of the circuit. A novel transformerless inverter is proposed for photovoltaic grid-connected systems, which suppresses the leakage current by clamping the common-mode voltage to half of the input dc voltage. The proposed topology can also achieve the high efficiency due to the low conducting losses. Besides, a PWM control method is given out for the inverter according to the analysis of the operational principle. Furthermore, comparison among several topologies is presented to explore the performance of the proposed topology. Finally, a 2kW prototype is built to verify the effectiveness of the inverter.