Research on an Improved Method for Maximum Power Point Tracking of Photovoltaic - Advanced Research on Computer Education, Simulation and Modeling - page 299

control algorithm was proposed. Through the simulation experiments, the results
show that the algorithm has good dynamic and steady-state performance.

2 Tracking Principle of PV MPP

Maximum power point tracking is a self-optimizing process, namely, by controlling
the PV terminal voltage U, the battery under a variety of sunlight and temperature
conditions can intelligently output maximum power, which is the MPPT principle of
PV. Output power of PV are greatly influenced by the external environment, ambient
temperature, sunlight intensity, and output voltage. The relationship of PV output
current and voltage [4] are:

qU

⎩ ⎨ ⎧ ⎭ ⎬ ⎫

.

I = I − I exp( ) − 1

(1)

s 0

AkT

I ,U is output current and voltage of PV cell respectively; I s is short-current under
the condition of 25 ℃ and 1000w/m 2 ;I o is reverse saturation current of PV; T is the
temperature of PV;k is Boltzmann's constant (k=1.38×10 23 J/K);q is electronic charge
(q =1.6×10-19C); A is diode characteristic factors (T=300K, A is approximately equal
to 2.8).
Figure. 1 shows the output power characteristics of P-U curve [5]. P-U curve is a
single convex curve. When the cell voltage is less than the maximum power point
Umax, the output power increases with the increasing U; when the operating voltage
is greater than the maximum power point voltage Umax, the output power decreases
with the increaseing U.

Fig. 1. PV output power characteristics of P-U curve

3 Improved MPPT Control Strategy

Traditional P&O method is a commonly method in the MPP tracking.The thought of
controlling algorithm is: measuring the current power output of photovoltaic cells P1,
then at the initial output voltage U adding a small Δ , the output power will be
changed to P 2 , comparing P 2 with P 1 . If the power increases, it will continue to use the
initial disturbance. If the power is reduced, it will change the direction of the initial
disturbance. This method is simple and easy to be implemented, but there will be