# A Secondary Reconfigurable Inverter and Its Control Strategy
## 3 Results and Discussion  
### Simulation Results and Discussion  
The circuit model of the secondary reconfigurable inverter shown in Figure 1 was built in MATLAB/Simulink platform to verify the feasibility and effectiveness of the proposed reconfigurable  
Figure 5: The proposed control strategy flow figure. inverter in this article. This paper adopts the controlling strategy connecting the constant-voltage, constant-frequency control method and the switch pulse resetting algorithm. The main parameters of the reconfigurable inverter applied in islanded micro-grid are shown the following Table 3.  
The simulation waveforms of the reconfigurable inverter applied to the islanded microgrid in the normal operating state and various faulty states are shown as follows. Set the system operating in normal state during 0-0.1 s and operating in the faulty state during 0.1-0.2 s.  
The simulation results of the inverter without reconfigurable structure are shown in Figure 6, which include the waveforms of the output voltages, the output currents and the deviations between output voltages with reference voltages. Figure 7 shows the simulation results of the inverter with a reconfigurable structure. \begin{table}
\begin{tabular}{c c} \hline \hline
**Main Parameters** & **Value** \\ \hline Reference voltage amplitude \(U_{m}\backslash\)V & 220 \\ Reference voltage frequency \(f\backslash\)Hz & 50 \\ DC side voltage \(u_{dc}\backslash\)V & 400/800 \\ IGBT switch frequency \(k\)Hz & 10 \\ Output side filter inductance \(L_{0}\backslash\)mH & 1.2 \\ Output side filter capacitance \(C_{0}\backslash\)μF & 4000 \\ Load resistance value \(R_{L}\backslash\Omega\) & 12 \\ Load inductance value \(L_{L}\backslash\)mH & 1.4 \\ \(K_{p}\) of PR & 0.6 \\ \(K_{R}\) of PR & 500 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The main parameters of the simulation model. Figure 6: Simulation results of the non-reconfigurable inverter: (**a1**) output voltages under faulty phase a; (**a2**) output voltages under faulty phase b; (**a3**) output voltages under faulty phase c; (**b1**) currents under faulty phase a; (**b2**) currents under faulty phase b; (**b3**) currents under faulty phase c; (**c1**) voltage deviations under faulty phase a; (**c2**) voltage deviations under faulty phase b; (**c3**) voltage deviations under faulty phase c.  
When the DC side voltage is set as 400 V and without reconfigurable structure in the inverter, Figure 6a1,b1,c1 show output voltages, currents and deviations between the output voltage with the reference voltage corresponding to faulty phase a, respectively. Figure 6a2,b2,c2 show output voltages, currents and deviations between the inverter output voltage with the reference voltage corresponding to faulty phase b, respectively. Figure 6a3,b3,c3 show output voltages, currents and deviations between the inverter output voltage with the reference voltage corresponding to faulty phase c, respectively. It can be seen from the waveforms that the inverter voltages and the currents of the inverter are the expected standard sinusoidal waves when the inverter is running in the normal state at 0-0.1 s. Moreover, the deviation among the inverter output voltage with reference voltage is very small at about 3 V. After 0.1 s, the inverter is running in the faulty state. The inverter output voltage and output current are seriously distorted, and a three-phase imbalance appears. The deviation among inverter output voltage with reference voltage is too large. Take case 1 in Table 1 as an example to verify the feasibility and validity of the proposed topology and the control algorithm in this simulation. The power switch V1 is faulty, and the inverter is reconstructed from TPSS to TPFS to be fault-tolerant. The DC voltage is set as 800 V in the reconfigurable inverter. Figure 7a-c are output voltages, currents and deviations between the output voltage with the reference voltage, respectively.