# Solutions to Increase PV Hosting Capacity and Provision of Services from Flexible Energy Resources
## 3 Simulation Results and New Frequency Adaptive _Pu_-Droop  
In this section, the main simulation results regarding potential solutions which could increase LV distribution networks' PV hosting capacity and provision of flexibility services from small-scale DER are presented. In Section 3.1, the focus of the simulations was in the following issues (Table 2):  
* Effect of BESSs utilization (Cases 4a-5b), two or three BESSs (with default _PU_-droops on BESSs). * Potential DER (PV and BESS) unit _Pf_- and _PU_-control interactions during future scenarios with very high PV penetration and very low load in (i) steady-state, (ii) over-frequency, and (iii) under-frequency situations to study the effect of: \[ \begin{array}{ll}\odot&\text{additional {\emph{PU}-control blocking logic (Cases 2a-4b and 5b);}}\\ \odot&\text{different {\emph{Pf}-} and {\emph{QU}-droop settings (Cases 3a-3b).}}\end{array} \]
* Effect of remote LV voltage measurement from PV (further in LV network) connection point to BESS at closest MV/LV secondary substation in order to maximize PV production during very low loads (Case 4b). * Effect of adapting the OLTC setting during very low load situations (Cases 1b, 2b, 3b, and 4a-5b). After that, Section 3.1 presents simulation results by utilizing measured 30 min real-life frequency data from SSG (Case 6). Finally, in Section 3.2. frequency adaptive _PU_-droops for PVs and BESSs during larger under- and over-frequency situations are proposed (Cases 7a-7b). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{**WTs** **} & \multirow{2}{*}{**PVs** **} & \multirow{2}{*}{**BESSs** **} & **QU-Droop** & _PU-Droop_ of** & _Pf-Droop_ of** & _PI-Droop_ & **PI-Blocking** & **OlTC Set** \\  & & & & **PVs/BESSs** & **PVs/BESSs** & **PVs/BESSs** & **PVs/BESSs** & **with PVs/BESSs** & **Value** \\ \hline
1a & 1 & 5 & 0 & 1/– & 1/– & 1/– & No & 20.7/1.035 \\
1b & 1 & 5 & 0 & 1/– & 1/– & 1/– & No & 20.0/1.0 \\
2a & 1 & 5 & 0 & 1/– & 1/– & 1/– & Yes & 20.7/1.035 \\
2b & 1 & 5 & 0 & 1/– & 1/– & 1/– & Yes & 20.0/1.0 \\
3a & 1 & 5 & 0 & 2/– & 1/– & 2/– & Yes & 20.7/1.035 \\
3b & 1 & 5 & 0 & 2/– & 1/– & 2/– & Yes & 20.0/1.0 \\
4a & 1 & 5 & 2 & 1/1 & 1/1 & 1/1 & Yes & 20.0/1.0 \\
4b & * & 1 & 5 & 2 & 1/1 & 1/1 & 1/1 & Yes & 20.0/1.0 \\
5a & 1 & 5 & 3 & 1/1 & 1/1 & 1/1 & No & 20.0/1.0 \\
5b & 1 & 5 & 3 & 1/1 & 1/1 & 1/1 & Yes & 20.0/1.0 \\ \hline \hline \end{tabular} WT is wind turbine, PV is photovoltaic unit, BESS is battery energy storage unit, *) remote voltage (U_PV_2) measurement from PV 2 connection point to BESS 1 control through communication, **) number of units.  
\end{table} 
Table 2: Simulation study cases, very low load in all cases (see Figure 2). \begin{table}
\begin{tabular}{c c} \hline \hline
**Time (s)** & **Initial Condition/Action** \\ \hline \(t=0\)–110 & PV unit active power (\(P_{\text{PV}}\)) is at nominal *) i.e., 300 or 450 kW \\ \(t=10.5\) & WT active power (\(P_{\text{WT}}\)) increases from initial 0.5 to 1.5 MW *) \\ \(t=15.0\) & WT active power (\(P_{\text{WT}}\)) increases from 1.5 to 2.5 MW *) \\ \(t=19.0\) & WT active power (\(P_{\text{WT}}\)) increases from 2.5 to 3.6 MW *) \\ \(t=30\)–40 & Over-frequency situation (50.07 Hz) **) \\ \(t=50\)–60 & Over-frequency situation (50.25 Hz) **) \\ \(t=70\)–80 & Under-frequency situation (49.9 or 49.4 Hz) **) \\ \(t=90\)–100 & Part of the load participates in demand response and disconnects from the LV network \\  & In all study cases of Table 2 PVs _QU_-droop is primary and _PU_-droop secondary local voltage control method \\ \hline \hline \end{tabular}  
* If voltage at PV or WT connection point is between min. and max. limits, **) _Pf_-control of PVs/BESSs participates in frequency control according to their _Pf_-droops.  
\end{table} 
Table 3: Simulation sequence actions and other issues in study cases (see Table 2 and Figure 1).