## 1 Introduction  
Nowadays, the increase in the world population, environmental pollution resulting from the burning of fossil fuels, and the need to deliver electricity to remote areas are factors that drive the use of renewable energy (RE). It is expected that these fundamental tasks and the fulfillment of international agreements related to the protection of the environment will be solved with the greater use of clean energy [1]. Solar, hydroelectric, and wind power are the primary sources that are being used by the new technologies [2]. Advances in electronic devices have led to an increase in power generation capacity from RE [3]. In 2016, the main contributions came from the European Union with 106 GW (Germany 41.3 GW), followed by China with 77.4 GW, Japan with 42.8 GW, and the United States with 40.9 GW for a total of 303 GW [4]. The power generation capacity from solar energy, in 2018, exceeded 505 GW [5]. The fast development of photovoltaic (PV) cell technologies, the continuous reduction of module costs, as well as advances in power electronics, are factors that drive the use of solar energy over other renewable energies [6]. Figure 1 shows the power generation capacity from the main sources of RE. The DC/AC converters are used in a wide variety of applications, from power supplies [7; 8; 9], to high-power industrial applications [10; 11; 12]. At present, they are also used as an interface for the control of motors for electric vehicles [13]. However, one of the most important uses is the transformation of the direct current generated by the photovoltaic panels, accumulators or batteries, into alternating current [14]. There are many points of view from which inverters are classified, one of the essential classifications is made according to their power supply. In this way, three types of inverters are established--Voltage Source Inverter (VSI) [15], Current Source Inverter (CSI) [16] and Z-Source Inverter (ZSI) [17]. As a summary, the main classifications of these power converters are presented in Figure 2.  
It is important to note that the average lifetime of DC/AC converters is over five years [19]. Research focuses on developing more durable topologies, reducing the installation and maintenance costs of PV systems. In this sense, Reference [20] presents a method for the accurate sizing of stand-alone photovoltaic (SAPV) residential generation systems for a pre-established reliability level. Figure 1: Electricity generation capacity scheme from renewable energy sources. Figure 2: DC/AC converters classification [18]. Grid-connected photovoltaic systems are typically categorized in two ways, with transformer and transformerless. For low-power applications, single-phase converters with a high or low-frequency transformer are generally used. It is possible to remove the transformer to reduce the weight, size, cost, and losses of the system. In this way, the efficiency of the inverter is increased by 1 or 2%. Therefore, the transformerless PV inverters are promising and attractive in industrial and academic fields [21]. However, due to the lack of galvanic isolation, high-frequency common-mode voltage (CMV) cause undesirable leakage current resulting in output-current distortion and safety trouble [22]. The leakage current depends mainly on the topology and the modulation strategy used. The main problems are--an increase in losses, current harmonics, safety issues, and interference problems of electromagnetic effect [23]. These problems have been reported in different papers [24; 25; 26; 27]. At this point, it is established that the leakage current depends on the value of CMV, the modulation strategy and the value of the parasitic capacitance [28]. At the same time, parasitic capacitance depends on [29]:  
* PV panel and frame structure. * The surface of the cells. * The distance between cells. * Weather conditions. * Type of electromagnetic compatibility filter.