# Application of a High-Power Reversible Converter in a Hybrid Traction Power Supply System
## 5 Simulation and Experiment
### Coordinated Control Experiments  
Two sets of high-power reversible converters have been successfully applied in the SHILIHE and XIDIAOYUTAI traction substations of Beijing Metro Line 10 (Beijing, China) as a demonstration example. The parameters of the reversible converters are shown in Table 5.  
The system main circuit of the traction substation is shown in Figure 16. \(U_{\text{ac}}\) indicates the voltage of the AC 10 kV grid, \(i_{\text{ac1}}\) indicates the AC current of the reversible converter, \(i_{\text{ac2}}\) and \(i_{\text{ac3}}\) indicate the AC current of each 12-pulse rectifier, respectively, \(i_{\text{dc1}}\) indicates the DC current of the reversible converter, \(i_{\text{dc2}}\) and \(i_{\text{dc3}}\) indicate the DC current of each 12-pulse rectifier, respectively, and \(U_{\text{dc}}\) indicates the DC bus voltage. The reversible converter has the same DC output characteristic as shown in Figure 5b. Figure 17 shows the voltage and current waveforms on the 10 kV side when the reversible converter and two 12-pulse rectifiers are working in parallel. As shown in Figure 17a, when the train is speeding up, the reversible converter and two 12-pulse rectifiers all work in the rectifying state: they share the train power. As shown in Figure 17b, when the train is slowing down, the reversible converter works in the inverting state, and the two 12-pulse rectifiers are blocked because of the high DC bus voltage. It is obvious that the AC current waveforms of the reversible converter are higher qualified than that of the 12-pulse rectifiers. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Short-Circuit Point** & **Parameters** & **Calculation Results** & **Simulation Results** \\ \hline \multirow{3}{*}{PSC, \(x=10\) m} & \(t_{1}\) & 1.9 ms & 2 ms \\  & \(i_{\text{L}}(t_{1})\) & 23,000 A & 22,800 A \\  & \(I_{\text{m}}\) & 3886 A & 3780 A \\ \hline \multirow{3}{*}{RSC, \(x=1.7\) km} & \(t_{1}\) & 14.6 ms & 15.5 ms \\  & \(i_{\text{L}}(t_{1})\) & 2572 A & 2000 A \\ \cline{1-1}  & \(I_{\text{m}}\) & 2550 A & 3000 A \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The comparison between the simulation results and theoretical calculation results. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline AC grid voltage & 10 kV & Transformer capacity & 1.6 MVA \\ DC rated voltage & 750 V & IGBT specification & 2400 A/1700 V \\ Converter capacity & 2 MW & Switching frequency & 2 kHz \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Parameters of the reversible converter. Figure 16: Main circuit of the traction substation in Beijing Metro Line 10. Figure 17: _Cont._  
Figure 18 shows the DC voltage and current waveform when the reversible converter and a 12-pulse rectifier are working in parallel. The meanings of the symbols are shown in Figure 16.  
As seen in Figure 18, along with the increase of traction power of the train, the DC bus voltage decreases significantly, but the DC current of the reversible converter and 12-pulse rectifier unit increase immediately. However, it is obvious that the current increase rate of the reversible converter is greater than that of the 12-pulse rectifier unit. The trends basically agree with the DC output curves  
Figure 17: AC current waveforms when the reversible converter and two 12-pulse rectifiers work in parallel. (**a**) train in traction state; (**b**) train in regenerative braking state. Figure 18: DC voltage and current waveforms when the reversible converter and a 12-pulse rectifier work in parallel. shown in Figure 5b. When the train work state is changed to braking from traction, the current of both 12-pulse rectifiers reduce to zero, but the DC current of the reversible converter changes from positive to negative, which means that the regenerative braking energy of the train has been fed back to the AC 10 kV grid through the reversible converter.