A single-phase transformerless full-bridge photovoltaic grid-tie inverter is presented. It utilizes 1) a virtual ground technique to mitigate ground leakage current, 2) a hybrid pulsewidth modulation (HPWM) scheme to profile the output current and prevent sudden changes in the common-mode voltage, and 3) a nonlinear output inductor to attenuate current ripple around zero crossings and minimize filter size. The HPWM is effectively the same as unipolar PWM (UPWM), but with soft voltage transition modulation introduced around the zero crossings. Apart from low switching losses, the output filter is implemented with a minimum number of components to achieve high attenuation of ripple current. By deriving the switching trajectory, a mathematical model is formulated, and the ground leakage current and the output current with the traditional UPWM and the proposed HPWM schemes are compared. The output current harmonics caused by the nonlinear output inductor is analyzed by the Volterra theory. A 340 W, 380 Vdc/110 V ac, 50 Hz prototype has been built and evaluated.

中文翻译：

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使用具有软电压过渡和非线性输出电感的混合 PWM 来缓解单相光伏逆变器的漏地电流


提出了一种单相无变压器全桥光伏并网逆变器。它利用 1) 虚拟接地技术来减轻接地泄漏电流，2) 混合脉宽调制 (HPWM) 方案来分析输出电流并防止共模电压突然变化，以及 3) 非线性输出电感器来衰减电流零交叉附近产生纹波并最小化滤波器尺寸。 HPWM 实际上与单极 PWM (UPWM) 相同，但在过零附近引入了软电压转换调制。除了低开关损耗外，输出滤波器还采用最少数量的元件来实现纹波电流的高衰减。通过推导开关轨迹，建立了数学模型，并对传统 UPWM 和所提出的 HPWM 方案的接地泄漏电流和输出电流进行了比较。采用Volterra理论分析了非线性输出电感引起的输出电流谐波。已构建并评估了 340 W、380 Vdc/110 V ac、50 Hz 原型。