## 3 Results
### Features of the Negative and Positive Power-Energy Divergence
\begin{tabular}{c c c} \hline \hline
**The Magnitude (\(\mathbf{d}\) of the** & **Frequency of Positive** & **Frequency of Negative** \\
**Day-Ahead PV Energy Forecast** & **Divergence in the Case of** & **Divergence in the Case of** \\
**Divergence Compared to the** & **Day-Ahead Forecast [\%]** & **Day-Ahead Forecast (Absolute** \\
**Real PV Energy Data [MWh]** & **Day-Ahead Forecast [\%]** & **Value] [\%]** \\ \hline \(0\)\(\times\)\(\leq\)\(10\) & \(13\) & \(17\) \\ \hline \(10\)\(\times\)\(\leq\)\(20\) & \(4\) & \(5\) \\ \hline \(20\)\(\times\)\(\leq\)\(30\) & \(4\) & \(4\) \\ \hline \(30\)\(\times\)\(\leq\)\(40\) & \(3\) & \(4\) \\ \hline \(40\)\(\times\)\(\leq\)\(50\) & \(4\) & \(3\) \\ \hline \(50\)\(\times\)\(\leq\)\(60\) & \(2\) & \(3\) \\ \hline \(60\)\(\times\)\(\leq\)\(70\) & \(3\) & \(3\) \\ \hline \(70\)\(\times\)\(\leq\)\(80\) & \(3\) & \(3\) \\ \hline \(80\)\(\times\)\(\geq\)\(90\) & \(3\) & \(2\) \\ \hline \(90\)\(\times\)\(\leq\)\(100\) & \(2\) & \(2\) \\ \hline \(100\)\(\times\)\(\leq\)\(5200\) & \(17\) & \(15\) \\ \hline \(200\)\(\times\)\(\leq\)\(300\) & \(13\) & \(13\) \\ \hline \(300\)\(\times\)\(\leq\)\(400\) & \(7\) & \(8\) \\ \hline \(400\)\(\times\)\(\leq\)\(500\) & \(6\) & \(5\) \\ \hline \(500\)\(\times\)\(\leq\)\(600\) & \(4\) & \(4\) \\ \hline \(600\)\(\times\)\(\leq\)\(700\) & \(2\) & \(3\) \\ \hline \(700\)\(\times\)\(\leq\)\(800\) & \(3\) & \(2\) \\ \hline \(800\)\(\times\)\(\leq\)\(900\) & \(2\) & \(1\) \\ \hline \(900\)\(\times\)\(\leq\)\(1000\) & \(1\) & \(0.4\) \\ \hline \(1000\)\(\times\)\(\leq\)\(1500\) & \(3\) & \(2\) \\ \hline \(1500\)\(\times\)\(\leq\)\(2000\) & \(1\) & \(1\) \\ \hline \(2000\)\(\times\)\(\leq\)\(2500\) & \(0.2\) & \(0.3\) \\ \hline \(2500\)\(\times\)\(\leq\)\(3000\) & \(0\) & \(0.05\) \\ \hline \hline \end{tabular} 
\begin{tabular}{c c c} \hline \hline
**The Magnitude (\(\mathbf{d}\) of the** & **Frequency of Positive** \\
**Day-Ahead PV Energy Forecast** & **Divergence in the Case of** & **Divergence in the Case of** \\
**Divergence Compared to the** & **Day-Ahead Forecast [\%]** & **Day-Ahead Forecast (Absolute** \\
**Real PV Energy Data [MWh]** & **Day-Ahead Forecast [\%]** & **Value] [\%]** \\ \hline \(0\)\(\times\)\(\leq\)\(10\) & \(13\) & \(17\) \\ \hline \(10\)\(\times\)\(\leq\)\(20\) & \(4\) & \(5\) \\ \hline \(20\)\(\times\)\(\leq\)\(30\) & \(4\) & \(4\) \\ \hline \(30\)\(\times\)\(\leq\)\(40\) & \(3\) & \(4\) \\  
Simulation Results of the Positive and Negative Divergence Reduction Potential of a Given Storage Size  
At the beginning of the research, the annual positive and negative TSO regulation need for a 1000 MWp PV system was summarized based on 15-min data during one year (Figure 7). The purpose of this was to determine the magnitude of the MWh differences between the years. The positive day-ahead regulation need varied between 78 and 89 GWh in the examined 5-year period. These values decreased by 20-30 GWh thanks to the most recent forecast method, and the average improvement reached 28%. In the case of the negative day-ahead data, the regulation need was between 76 and 92 GWh, and the best forecast reduced these values by 21-34 GWh. In this case, the average improvement was 31% (Figure 7). To understand the results of the simulations, the day of 12/07/2019 was separately simulated and the battery charge level started from 0% in this case (Figure 8). In the example, the black line represents the simulated PV power with a 1000 MWh Li-ion battery, and the goal was to try to keep the day-ahead or the most recent (intraday) PV forecast. In the case of a positive divergence (from the perspective of the PV system operators), because of the difference between the PV power without battery and the forecasted power data, the energy storage had been charged with this difference. Battery discharging happened to eliminate the need for positive TSO regulation. In the case of a discharged (or fully charged) battery, the balancing energy was provided by the grid (Figure 8).