# A PMSG Wind Energy System Featuring Low-Voltage Ride-through via Mode-Shift Control
## 6 Experimental Verification
Since the voltage sag is less than 50%, \(I_{d}=0\), \(I_{q}=2A\) during the dip when applying the proposed technique in \(P_{grid}=0\), \(Q_{grid}=30\) W compared to the values of \(P_{grid}=60\) W, \(Q_{grid}=0\) VAR without the proposed technique. Since MPPT is terminated in the proposed technique, boost inductor current \(I_{b}\) changes from \(I_{b}=2\)A to \(I_{b}=0\), and generator current becomes \(i_{a-gen}=0\); thus, the generator active \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Parameter** & **Value** \\ \hline \(P_{gm}\) & Rated power (\(kW\)) & 0.31 \\ \(\bar{R}_{a}\) & Stator Resistance (\(\Omega\)) & 12.5 \\ \(\bar{\sigma_{f}}\) & Field Flux linkage & 0.36 \\ \(\bar{f}\) & Moment of Inertia (kg.m\({}^{2}\)) & 0.016 \\ \(\bar{v}_{gm}^{a}\) & Nominal Voltage at 1500 rpm (V) & 200 \\ \(\bar{f}_{c}\) & PWM switching frequency (Hz) & 5000 \\ \(\bar{f}_{dc}\) & Boost converter inductance (mH) & 10 \\ \(\bar{C}_{r}\) & Input boost converter capacitor (μF) & 1200 \\ \(\bar{C}_{k}\) & DC-link capacitor (μF) & 2200 \\ \(V_{dc}\) & DC-link reference voltage (V) & 100 \\ \(v_{grid}\) & Line-line grid voltage (V) & 40 \\ \(\bar{L}\) & Grid filter and coupling transformer inductance (mH) & 2 \\ \(R\) & Grid filter and coupling transformer resistance (\(\Omega\)) & 1.5 \\ \(f_{grid}\) & Grid frequency (Hz) & 50 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experimental set-up parameters. Figure 13: Experimental results during 70% symmetrical grid voltage dip without the proposed control scheme: (**a**) phase ‘a’ grid voltage \(v_{grid}\) and d-axis grid voltage \(V_{d}\); (**b**) phase ‘a’ grid current \(i_{grid}\) and DC-link voltage \(V_{dc}\); (**c**) d- and q-axis grid currents \(I_{d}\) and \(I_{q}\); (**d**) grid active power \(P_{grid}\) and reactive power \(Q_{grid}\) ; (**e**) Boost chopper current \(I_{b}\) and PMSG speed \(n\); (**f**) PMSG Line-line voltage \(v_{ab-gen}\), phase a-current \(i_{a-gen}\) and active power \(P_{gen}\). power \(P_{gen}\) will be zero. The shaft mechanical speed \(n\) increases from 900 to approximately 1012 rpm with the suggested control technique, equivalent to 1.1 p.u. After the dip is cleared, the MSC recovers back the PMSG speed while the GSC retakes the charge of the DC-link voltage. Energy stored in the rotor inertia during the dip incident is being released into the grid while the generator and grid currents reach their pre-fault values. Experimental grid current results, for both cases (swap and non-swap schemes) are analyzed during LVRT as shown in Figure 15. Grid current THD is enhanced during LVRT from 12% with the non-swap scheme to 5% using swap control. This confirmed the ability of the swap to decouple the DC-link voltage control dynamics from the grid current one during LVRT, thus enhancing THD during fault. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Results** & & \\
**During Fault** & & \\ \hline \hline  & **No Mode-Shift Control** & **With Mode-Shift Control** \\ \hline \(h_{t}\) (A) & 2 & 0 \\ \hline \(l_{t}\) (A) & 4 & 0 \\ \hline \(l_{t}\) (A) & 0 & –2 \\ \hline \(l_{pub}\) peak (A) & 4 & 2 \\ \%THD & 12\% & 5\% \\ \hline \(V_{kt}\) (V) & 160 & 100 \\ \hline \(P_{grid}\) (W) & 60 & 0 \\ \hline \(Q_{grid}\) (W) & 0 & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Experimental performance results. Figure 14: Experimental results during 70% symmetrical grid voltage dip using the proposed control scheme: (**a**) phase ‘a’ grid voltage \(v_{grid}\) and d– axis grid voltage \(V_{d}\); (**b**) phase ‘a’ grid current \(i_{grid}\) and DC– link voltage \(V_{dc}\); (**c**) dq– axis grid currents \(l_{d}\) and \(l_{q}\); (**d**) grid active power \(P_{grid}\) and reactive power \(Q_{grid}\); (**e**) Boost chopper current \(l_{b}\) and PMSG speed \(n\); (**f**) PMSG Line-line voltage \(v_{ab-gen}\), phase a– current \(i_{d-gen}\) and active power \(P_{gen}\).