**4. Simulation studies**

The Boost converter circuit and two level Inverter circuit were simulated with the PLECS & PSIM power electronics simulation tools. The simulation parameters *Design of High Power Regenerative Battery Discharger System for Nuclear Power Plant DOI: http://dx.doi.org/10.5772/intechopen.98534*

were decided based on the design parameters and various input voltage selections as tabulated in **Table 3** [18].

The Schematic of converter circuit for all the input voltages are designed and typical 48 V DC Input simulation circuit is shown in **Figure 5** [19]. The switching patterns of two IGBTs (S1, S2) used in the two phase IBC is shown in **Figure 5** [20]. The phase shift between the two phase limbs is 180 degrees.

For all the three modes and the output of 560 V DC was achieved and corresponding output voltage, inductor currents and input current were obtained graphically [21]. The 48 V Input DC circuit is simulated for duty cycle of 0.9142 and the results are represented in **Figure 6** [22].

The output voltage obtained for 48 V DC input circuit in simulation has very low ripple voltage content within 1 Volt [23]. The inductor current ripple is 30% and the input current ripple is 15%, which are well within design limits. Similarly, the duty cycle 'D' is varied for input voltages 220 VDC and 360 V DC as per the **Table 3** and the corresponding graphical results are shown in **Figures 7** and **8** [24].

The simulation results show very less ripple in input current and voltage compared to any conventional boost converter [25]. The Inverter design parameters were arrived with conventional methods, output LC Filter is designed for reducing higher order harmonics at output current and smoothening the output current. The simulation parameters are tabulated in **Table 4**.


#### **Table 3.**

*Simulation parameters for interleaved boost converter.*

**Figure 5.** *Schematic of interleaved boost converter with 48 V input.*

**Figure 6.** *Waveforms of interleaved boost converter with 48 V input.*

**Figure 7.** *Waveforms of interleaved boost converter with 220 V input.*

*Design of High Power Regenerative Battery Discharger System for Nuclear Power Plant DOI: http://dx.doi.org/10.5772/intechopen.98534*

#### **Figure 8.**

*Waveforms of interleaved boost converter with 360 V input.*


#### **Table 4.**

*Simulation parameters for inverter.*

The Schematic of inverter simulation circuit with the PWM Generators is given in **Figure 9** and corresponding output voltage waveforms as obtained from simulation is shown in **Figure 10** [26, 27].

The FFT of output AC Voltage is shown in **Figure 11**. **Figure 11** also shows harmonic spectra in the waveform. The predominant harmonics in two level inverters are 5th and 7th harmonics, which is reduced by incorporating LC Filter at output [28]. The Δ-Δ Isolation Transformer at output gives circulating path for third harmonics zero sequence currents and thereby resulting very less third

**Figure 9.** *Simulation of two level inverter systems*

**Figure 10.** *Waveform of inverter O/P voltage.*

harmonic output to load [29]. THD at output is calculated to be 7.2% as tabulated in **Table 5** [30].
