# Effect of Demand Side Management on the Operation of PV-Integrated Distribution Systems
## 3 Results and Discussion
### Case III: With CVR, without DG and DLC  
The algorithm used starts by making all tap-changing transformers go to their default tap position (defined as 1.0 pu voltage), and it takes two set points V\({}_{\text{min}}\) and V\({}_{\text{s}}\). The algorithm measures the voltage at all loads in the 33-kV region every 30 min, and then it decides whether to increase, decrease or not change the tap position. If any load bus has a voltage lower than V\({}_{\text{min}}\) the tap position is increased; if any load bus has a voltage higher than V\({}_{\text{s}}\) while all other load buses' voltages are higher than V\({}_{\text{min}}\), the tap position is decreased; and, if all load buses' voltages are between V\({}_{\text{min}}\) and V\({}_{\text{s}}\) no change will occur. For the IEEE 30-Bus test system, V\({}_{\text{s}}\) must be set to 1.08 or less p.u. If it is chosen higher than 1.08, the saved energy will drop significantly (the CVR algorithm will be rendered useless). When the taps of the tap-changing transformers are lowered, the voltages of the 33-kV region buses drop, but the voltage of bus 29 remains slightly higher than 1.08 for all relevant tap positions, which is why whatever V\({}_{\text{s}}\) is chosen, bus 29 will ensure that the algorithm will lower the taps until the bus with the lowest voltage in the 33-kV region (bus 26) will be just above 0.9 p.u. The V\({}_{\text{s}}\) threshold will be entirely different for different test systems. One can see the voltage profile of the 30-Bus IEEE system in Figure 8. The buses of interest here are the following buses found in the 33-kV region: 10, 12, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24, 26, 29 and 30. The aforementioned buses' voltages can be seen to drop after the algorithm is implemented. In addition, as a result of voltage reduction, the active and reactive powers have dramatically reduced, as presented in Tables 2 and 3. The fact that the CVR reduced 3% of the real power consumed by most loads in the 33-kV region is a testimony of how effective this technique is. The voltage reduction done should affect no customer negatively since they are getting an appropriate value of voltage (more than 0.9 pu), and they are getting constant power. The algorithm used is a closed loop control algorithm, which means that, not matter what load shape or massive load changes have happened, this algorithm can detect them (every 30 min) and try to adapt (sometimes a little bit slowly). The CVR algorithm managed to decrease consumed power, reduce system losses and provide the system with a voltage control scheme to automatically manage rapid voltage changes. Figure 7: Case II: Voltage profile with/without DG. In Figure 9, one can see the voltages on buses 10, 17 and 26 along the 24-h simulation with a varying load shape. The voltages were reduced to a very good extent while remaining above the V\({}_{\text{s}}\) a considerable amount of time, which is still fine since this will be nearly impossible to overcome when dealing with a lot of loads that have different voltages. The important notion is that all the load buses' voltages remained above V\({}_{\text{min}}\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Bus/Load (\#)**} & **Active Power** & **Active Power** & **Active Power** & **Reduction** \\  & **without CVR (kW)** & **with CVR (kW)** & **Reduction (kW)** & **Percentage (\%)** \\ \hline
10 & 1606 & 1556.3 & 49.7 & 3.09 \\ B12 & 3105 & 3042.3 & 62.7 & 2.02 \\ B14 & 1713.3 & 1651.7 & 61.6 & 3.60 \\ B15 & 2264.1 & 2169.2 & 94.9 & 4.19 \\ B16 & 968.08 & 936.29 & 31.79 & 3.28 \\ B17 & 2488.3 & 2393.2 & 95.1 & 3.82 \\ B18 & 882.03 & 834.02 & 48.01 & 5.44 \\ B19 & 2617.7 & 2467.3 & 150.4 & 5.75 \\ B20 & 606.83 & 575.37 & 31.46 & 5.18 \\ B21 & 4831.5 & 4600.9 & 230.6 & 4.77 \\ B23 & 881.73 & 832.41 & 49.32 & 5.59 \\ B24 & 2395.1 & 2241.4 & 153.7 & 6.42 \\ B26 & 958.49 & 865.54 & 92.95 & 9.70 \\ B29 & 657.45 & 596.35 & 61.1 & 9.29 \\ B30 & 2897 & 2580.5 & 316.5 & 10.93 \\ \hline \hline \end{tabular}
\end{table}