Research on an Improved Method for Maximum Power Point Tracking of Photovoltaic - Advanced Research on Computer Education, Simulation and Modeling - page 303

Fig. 5. Comparison of two algorithms for
output power

Fig. 6. Light mutation of two algorithm for
output power

method and improved method was simulated to verify the validity of the algorithm.
The curves of obtaining the PV output power are shown in Figure.5 and Figure.6.
Figure.5 shows the output power between traditional P&O method and improved
method at 1000W/m 2 and 25 ℃ . Figure. 6 shows the comparison chart of output
power about the two algorithms due to solar insolation change from 600 W/m 2 to
1000W/m 2 .
As can be seen from Figure 5, traditional P&O method's power oscillates at the
beginning of the process. After a period of time, the waveform gradually stabilized
and oscillated in a small area. It will reach maximum power about 0.35s and oscillate
largely around the MPPconversely, the power of improvement has a small oscillation
at the outset and achieves MPP about 0.15s. It could be drawn that the improved
algorithm has a quick tracking speed, high precision, small fluctuations around the
MPP. Figure 6 shows that the power of illumination intensity mutates from 600 W/m 2
to 1000W/m 2 which the traditional P&O method has a poor tracking accuracy, larger
fluctuations and a bad responsion when the light suddenly changes. Nevertheless, the
improved algorithm has a rapid responsion to light mutated, and be quickly stabilized
at MPP. It is proved that the improved algorithm has a better stability and high effi-
ciency in different illumination conditions.

5 Conclusion

The paper analysed the characteristics of the PV power system and proposed a new
MPPT control algorithm by combining with various control algorithms. The voltage
and current could be calculated by the open-circuit voltage, short-circuit current
online testing, thus the disturbance of PV system with traditional detection method. In
order to reduce the power oscillation around MPP and the “false judgement” phe-
nomenon, variable step P&O method was adopted by the idea of gradual approxima-
tion method to search step, so the MPP could be rapidly and accurately tracked.
Through the curve two algorithms in PV output power, the simulation results demon-
strate that the improved algorithm could quickly track the change of external envi-
ronment, also avoid the power fluctuation and have a good practical value.