###### Abstract
One proposed inverter, called the neutral point clamped (NPC), which reduces the filter requirement, leakage current, and EMI, and a modified type of NPC called the Active NPC (ANPC), mitigate the limitations of NPC topology [16; 17]. In 2005, SMA proposed a new inverter topology called H5, which reduces CMV through eliminating the high-frequency component of CMV by detaching the power grid from the PV module during the zero-voltage state [18]. Another popular transformerless inverter is the HERIC (Highly Efficient and Reliable Inverter Concept) inverter, developed by Sunways in 2006. It consists of six switches and is based on the AC decoupling method in order to isolate the output inductor filter from the PV panel parasitic capacitance and achieve unipolar SPWM [15]. Therefore, this topology leads to reduced leakage current and EMI, increasing the efficiency and reducing the size [19]. A new type of inverter with the theoretical elimination of the leakage current derived from the conventional H6 inverter was proposed in [20]. Another transformerless topology based on the common ground technology is introduced, which connects the grid ground to the PV panels ground permanently, resulting in constant CMV. Therefore, according to the capacitor current equation, the leakage current will be eliminated completely. \[i_{CM}=C_{PV}\times\frac{dv}{dt} \tag{1}\]  
where \(i_{CM}\) is the common mode leakage current, \(C_{PV}\) is the parasitic capacitance of the PV panel, and \(\frac{dv}{dt}\) is the voltage variation across the parasitic capacitance. Based on the common ground method, a new concept was proposed in [6] in 2013, called the virtual DC bus, which is created by a flying capacitor. The virtual DC voltage supplies the negative current to the grid, while the positive current flows to the grid directly from the PV panel. However, in this topology, there are two or more switches in series during the active state which increases conduction losses and requires a relatively large capacitor, because it is charged only during the positive power cycle. A flying inductor inverter named after \"[PERSON]\" was proposed as a patent in [21], but it has no ability to deliver reactive power and is constructed with a large number of components. A new topology was proposed in [22] that charges the flying capacitor during the zero voltage state in both the positive and negative power cycle but has two extra diodes and one extra capacitor. Recently, a new topology proposed in [23] solved many of the drawbacks of previous types of transformerless inverters based on the flying capacitor, consisted of only four switches, one switch in series during active state, and proposed a modifying control method to lower the current stresses during the flying capacitor charging state. Additionally, it allows the capacitor to charge during the zero voltage state in both positive and negative power cycles, but it requires a bipolar blocking switch and still requires a relatively large capacitor. This paper proposes a new transformerless inverter topology based on the common ground concept and virtual DC bus. The proposed transformerless inverter is constructed of a buck-boost converter, a two-switch inverter, and an extra two switches with two diodes to achieve freewheeling and the zero voltage state for unipolar SPWM. The buck-boost converter is utilized to supply the flying capacitor continuously, in all inverter operation states, with the required energy that will be utilized in the negative power cycle. The two switches deliver the power into the grid during the negative and positive power cycle and the freewheeling paths provide the output inductor freewheeling path and help in achieving a unipolar SPWM control scheme. The proposed inverter reduces conduction losses, only one switch in the current path during each active state, reducing the flying capacitor size and stresses and allowing the capacitor to charge during all operation states. Additionally, this eliminates the leakage current (theoretically) because of the common ground structure.