# Optimum System for Diagnosing Power Quality in Electrical Microgrids
## 4 Results
### Performance of DiagElect  
To evaluate the performance of DiagElect as an electrical measurement network, specifically for identifying harmonic-injecting nodes, the experimental microgrid described in Section 2.3 was used. Notably, one SDMD was installed at each node of the microgrid to collect voltage and current measurements.  
Voltage and current measurements for each microgrid node were collected simultaneously and then received by the host computer, which processed the data according to the methodology outlined in Section 2.2. The computed parameters for harmonic source identification within the experimental microgrid, including the voltage and current THD, the total and fundamental active and reactive power components, and the HGI value, are presented in Table 4.  
Figure 9: Comparative performance of the proposed SDMD and Circutor® Percentages of deviations in both voltage and current, relative to the reference values provided by the grid emulator. (**a**) Percentage of voltage deviation. (**b**) Percentage of current deviation.  
The voltage and current THD for each microgrid node were computed using (1) and (2), respectively. The total and fundamental active and reactive power components were calculated using (3)-(6), and the HGI value was determined using (8).  
It is worth noting that the voltage THD is the same across all microgrid nodes because all the loads are connected to the same point: the PCC.  
The current THD values for nodes 1 and 2 are lower compared to those for nodes 3 and 4. The current THD values of nodes 1 and 2 are close to zero because these currents primarily consist of the fundamental component. In contrast, the higher current THD values for nodes 3 and 4 indicate that they are harmonic source nodes. Figure 10 shows the current spectra for nodes 3 and 4.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & **Node 1** & **Node 2** & **Node 3** & **Node 4** \\ \hline \(THD_{\text{V}}\) (\%) & 1.14 & 1.14 & 1.14 & 1.14 \\ \(THD_{\text{I}}\) (\%) & 1.13 & 1.16 & 28.90 & 66.46 \\ \(P_{\text{T}}\) (W) & 645.7 & 61.7 & 723.7 & 169.8 \\ \(P_{\text{I}}\) (W) & 645.6 & 61.6 & 724.2 & 169.9 \\ \(Q_{\text{T}}\) (Var) & 4.62 & 232.9 & 94.0 & 48.3 \\ \(Q_{\text{I}}\) (Var) & 4.62 & 232.9 & 94.7 & 47.5 \\ \(HGI\) (\%) & 0.00 & 0.53 & 23.79 & 56.97 \\ \hline \end{tabular}
\end{table}
Table 4: Computed parameters in each node of the microgrid.  
Figure 10: Current spectra corresponding to (**a**) node 3 and (**b**) node 4.  
Waveforms measurements for both voltage and current at each microgrid node are illustrated in Figure 11. Specifically, Figure 11a shows an unbalanced star-connected linear load consisting of three resistances (81 \(\Omega\), 124 \(\Omega\), and 250 \(\Omega\)) connected to node 1. Figure 11b illustrates a balanced star-connected linear load consisting of three inductive impedances (47 \(\Omega\) in series with 0.66 H) connected to node 2. Figure 11c displays three single-phase regulators connected in star with the same inductive load on the DC side (94 \(\Omega\) and 0.962 mH) connected to node 3. Figure 11d shows node 4, which is made up of a three-phase rectifier with a capacitive impedance (842 \(\Omega\) and 10 \(\mu\)F) connected on the DC side.  
Figure 11: _Cont._