*2.3. PV Plant Configuration*

Typical information of a PV generation system is shown in Table 1. A PV system contains inverters by based on own topology: central, string, multistring, and module integrated. The general form of the hybrid system takes a large-scale PV farm that is suitable for the ESS compensation plan. Thus, central and multistring topologies (more than 30 kilowatts (kW)) would be appropriate in this analysis. The PV connection that includes the inverter and transformer based on both topologies is described in Figure 3. As shown in the figure, in the case of a multistring topology, a common DC area is formed at connection point of several single strings. Since the DC-DC converters could measure each connection point of the string, a power flow analysis for generating a modified ESS signal could be simplified. In other words, the feasibility study for the multistring topology can be progressed based on one single array that makes up a string (the matrix for the modules is larger than that of the converters). The generalized string structure in [27] is used in this analysis. To secure the robustness in terms of power extraction, a MW-scaled PV is connected to the grid through a central inverter topology [28]. With the topology, a mega-voltage-ampere (MVA) class DC/AC inverter can accommodate several thousands of PV panels. However, unlike other topologies, the central topology exhibits low levels of flexibility and high mismatching losses due to its huge configuration characteristics.

As mentioned earlier, the main focus of this paper is to check control constraint of the accuracy improvement plan. A more detailed description of the structure can be found in [13]. In order to explain the ESS operation plan, a DC power flow method applied on two topologies is described in Section 3. In addition, simulation studies to find availability according to expected delays are discussed in Section 4.


**Table 1.** Numerical information of PV inverter topologies.

**Figure 3.** Configuration of PV inverter topologies (**a**) multistring (**b**) central.
