*2.1. ES-2 Topology*

The circuit diagram of a single-phase ES-2 is shown in Figure 2, enclosed within the dashed line. The ES is built up around an VSI whose output voltage, designated with *vi*, is proportional to *Vdc* as well as to the modulation index of VSI. The control of the ES, not shown in the figure, acts on the VSI through the delivery of the gating signals for its switches and is aimed at imposing an ES output voltage with the required values for its magnitude and phase.

**Figure 2.** ES-2 circuit diagram.

In Figure 2, *R*1 and *L*1 denote the impedance of transmission line, and *Z*2 and *Z*3 denote the CL and the NCL. Moreover, *vG* is the equivalent voltage of the system generators. In order to make it simple and consistent with existing definitions, it is also called line voltage here. *vES* represent the the ES output voltage. *iG* represents the current entering into the PCC, and *iL* and *i*3 represent the currents at the VSI output and through the NCL, respectively. Lastly, *vS* represents the PCC voltage that coincides with the voltage across the CL.
