## 4 Simulation Results
### Results of Actual Test for Smart Inverter Control
Moreover, under the high-frequency switching control of the switch, the measurement is susceptible to high-frequency signal interference, resulting in the distortion of the mea  
Figure 19: The output power regulation of the smart inverter when the per-unit value of mains voltage was between 1 p.u. and 1.03 p.u. Figure 18: When the per-unit value of mains voltage in smart inverter under Phase a was between 1 p.u. and 1.03 p.u. : (**a**) output voltage and current waveforms under the actual test; (**b**) partial waveform enlargement of Figure (**a**). sured current signal in Figure 18. The distortion of the current signal will also cause the distortion of the measured observed apparent power, real power, and reactive power signal in Figure 19.  
When the PVMA encountered a sudden drop in power generation due to the influence of unexpected shades from clouds or other climate factors, which set the per-unit value of the voltage of the grid-connected point between 0.97 p.u. and 1.0 p.u., the reactive power of the grid system was positive (Q > 0) and PF of the system was lagging. Therefore, the output current of the smart inverter should be controlled to be leading ahead of the output voltage, so the PF was leading, where the reactive power of the grid system could be provided to stabilize the voltage at the grid-connected point. Figure 20a,b displayed the output voltage and current waveforms under the actual test of the smart inverter under Phase a and the waveforms after partial enlargement, respectively. From Figure 20b, it could be observed that when the per-unit value of the voltage of the grid-connected point was between 0.97 p.u. and 1.0 p.u., the smart inverter started to control the output current, the phase was leading ahead of the output voltage, and the PF was adjusted to be leading for providing reactive power of the system. From the output power alteration under the actual test of the smart inverter in Figure 21, it was known that through the PF regulation of the smart inverter, the real power in grid fed from the inverter reduced from 1600 W to 1440 W but provided the reactive power of 774 VAr (Q < 0) to grid system. However, the total output of apparent power still maintained at the PVMA capacity of 1600 VA.  
Figure 20: When the per-unit value of mains voltage in smart inverter under Phase a was between 0.97 p.u. and 1 p.u. : (**a**) output voltage and current waveforms under the actual test; (**b**) partial waveform enlargement of Figure (**a**). Through results from the simulation and an actual test, it was verified that the developed photovoltaic smart inverter could provide or absorb reactive power for the grid system by controlling PF at the output end, so the voltage of the grid system could be stabilized. Therefore, the developed smart inverter in this paper is feasible and applicable. The test results of the three cases are summarized in Table 4. It can be seen from Table 4 that the converter can adjust the power factor (PF) at the end of the grid system by adjusting the output real power and reactive power, so that under the fixed output power of photovoltaic system, regardless of the increased or decreased system load, the grid system voltage of the parallel point can be controlled to a fixed value. Still, the output apparent power remains unchanged, that is, the same as the maximum output power of the PVMA. Since the power generation of the photovoltaic system is mainly to assist the power grid system in supplying power to the load, the power supply ratio is not large. Only when the load suddenly plummets and causes the voltage of the load terminal to rise sharply, the real power output of the smart inverter can be lowered and the reactive power absorbed by the smarter inverter can be increased while the power output of the photovoltaic system remains unchanged. The load terminal voltage is controlled to maintain the rated voltage to ensure the power supply quality of the power system. The simulation and actual test results under this condition have been verified in this paper.