*5.1. Normal Mode*

In order to investigate the performance of both HMSWZS and SHMS in terms of DC-side voltage fluctuation and average output power of the PV module under identical conditions, the DC-side voltage (VPV1) and output power (P1) of the PV module in the first H-bridge are shown in Figure 8. The simulation starts with the operation of the system under symmetrical condition (E = 1000 <sup>W</sup>/m<sup>2</sup> and T = 25 ◦C). In the simulation, since the focus of this paper is to study the influence of DC-side voltage fluctuation on the energy acquisition of PV module, the reference of the DC-side voltage is set directly at the maximum power point of PV module instead of adopting the MPPT algorithm. As shown in Figure 8, the maximum fluctuation of VPV1 is 4.95 V when HMSWZS is utilized, while that of SHMS is only 3.40 V, which is reduced by up to 31.30%. With the HMSWZS, the output power of the first PV module ranges from 220–255.1 W, and the average is about 251.9 W. Since the SHMS is utilized to reduce the DC-side voltage fluctuation, the output power ranges from 245–255.1 W and the average is about 253.4 W. Figure 9 shows the total output power (PT) of the CHB inverter with both methods. As shown in Figure 9, with HMSWZS, the total output power of the CHB inverter ranges from 1243–1275 W and the average is about 1262 W. When SHMS is utilized, the total output power of the CHB inverter ranges from 1256–1277 W and the average is about 1269.2 W. Compared with the HMSWZS, the e fficiency of the CHB inverter can be improved about 0.56% by adopting the SHMS. Therefore, under the normal mode, the SHMS has a superior capacity of suppressing the DC-side voltage fluctuation compared with the HMSWZS, thereby improving the energy collection of the PV module.

**Figure 8.** Simulation results under normal mode: the DC-side voltage (VPV1), and output power (P1) of the PV module in the first H-bridge with: (**a**) HMSWZS and (**b**) SHMS.

**Figure 9.** Simulation results of the total output power of the CHB inverter under the normal mode with: (**a**) HMSWZS and (**b**) SHMS.
