## 4 Power Converter Topologies
### AC Grid Stage (AC-DC Converters)  
PV-grid connected charging systems for EV/PHEV can be connected either to a low voltage (LV) or a medium voltage (MV) AC grid [25]. However, this paper is focused on the LV AC source. In PV/grid-tied EV charging systems, unidirectional or bidirectional inverters can be used, though, bidirectional inverters are often used to enable the V2G mode of operation or to feed the excess power from the PV to the grid, as will be explained later in another section. Inversion and rectification are the two modes of operation of a bidirectional inverter. When operating in the inversion mode, the power on the DC bus is fed back to the grid, synchronizing the magnitude and frequency with that of the AC grid, acting as a DC-AC inverter. In contrast, when operating as a rectifier, power is transferred from the grid to the DC bus, configured as an AC-DC converter. Therefore, the inverter used in this stage must be able to operate in any of the current/voltage quadrants [13; 16; 54]. The following are the bidirectional AC-DC inverter topologies that will be discussed:  
1. One-phase half-bridge (HB) bidirectional boost inverter (Figure 7a);
2. One-phase voltage source inverter (VSI) full-bridge (FB) bidirectional boost inverter (Figure 7b); \begin{table}
\begin{tabular}{c c c c c c} \hline \hline Ref. & DC-DC Topology & Advantages & & **Disadvantages** & **Applications** \\ \hline \hline \multirow{8}{*}{[29; 42]} & \multirow{8}{*}{Buck-Boost Converter} & & \(\bullet\) & There are many & \\  & & & & harmonic components & \\  & & & in the input current & & \\  & & & & & It has a high input & \\  & & & & voltage ripple & \\  & & & & & It has substantial & \\  & & & in any operating region of & & noise issues & \\  & & & the PV module (from I\({}_{\text{SC}}\) to & & It is more complex & \\  & & & & and expensive & \\  & & & & & and voltage stress on & \\
29; 42] & Buck-Boost Converter & & & & It is able to track the & \(\bullet\) & Used for \\  & & & modules’ MPF at varying & & proportional & \\  & & & conditions’ irradiance, & to efficiency & \\  & & & temperature and load & & \(\bullet\) & Lower efficiency than & \\  & & & & the boost converter & & \\  & & & & The switch drive & \\  & & & & is floated & \\  & & & & It has output & \\  & & & & inverted polarity & \\ \hline \hline \multirow{8}{*}{[29; 42]} & \multirow{8}{*}{Cuk Converter} & \multirow{8}{*}{Cuk Converter} & \(\bullet\) & This converter can operate & & \\  & & in any operating region of & & High number of & \\  & & the PV module (from I\({}_{\text{SC}}\) to & & passive components & \\  & & & & & It has high electrical & \\  & & & & Prevent large harmonics at & \\  & & & the input & \(\bullet\) & The switch drive & \\  & & & & It is more reliable and less & \\  & & & noisy than other topologies & & \\  & & & due to the inductors at the & & inverted polarity & \\  & & & input and output & & \\ \hline \hline \multirow{8}{*}{[29; 42]} & \multirow{8}{*}{SEPIC Converter} & \multirow{8}{*}{SEPIC Converter} & \(\bullet\) & It has output & & \\  & & & non-inverted polarity & & \\ \cline{1-1}  & & & The switch drive is & & \\ \cline{1-1}  & & & grounded, simplifying the & & \\ \cline{1-1}  & & & gate-drive circuitry & & \\ \cline{1-1}  & & & Less ripple on input side & & \\ \cline{1-1}  & & & due to the continuous & & \\ \cline{1-1}  & & & input current & & \\ \cline{1-1}  & & & This converter can operate & & \\ \cline{1-1}  & & & in any operating region of & & \\ \cline{1-1}  & & & the PV module (from I\({}_{\text{SC}}\) to & & \\ \cline{1-1}  & & & V\({}_{\text{OC}}\)) & & \\ \hline \hline \end{tabular}
\end{table}