10. INTRODUCTIONSThe research on the solar battery photovoltaic output characteristics has an important significance in some aspects, such as in depth exploration of photovoltaic power generation mechanism and the development of the application of solar energy technology. Analyzing the change of parameters ,such as diode ideal factors（A） 、series resistor（Rs）and shunt resistance（Rp）,has an effect on the photovoltaic output characteristics ,and then research the change law of the photovoltaic output characteristics under any light intensity (light intensity) and environment temperature (environment temperature),which plays a guiding role for improving the utilization of solar energy methods and the development of a more efficient energy conversion device 1.At present, the equivalent circuit which contains diode and the Series-parallel resistance is a more accurate photovoltaic output characteristic mechanism model. But, as the strong light and temperature changes, the A, Rs and Rp changes. The Model is a nonlinear function with the parameters changes. It is difficult to solve the model parameters and calculate the maximum power point directly. Whats more, most of the existing documentation methods are the use of standard test conditions data provided by manufacturer, through simplifying photovoltaic characteristics equation approximately, only can solve model parameters under standard test conditions simultaneously, cant be 2extended to arbitrary light intensity and temperature conditions 2-3.Through analyzing A, Rs, Rp parameters which affect photovoltaic output characteristics law, this paper gives a method based on parabola extreme point to solve out maximum power point directly . Then, using maximum power point calculation process data, we build photovoltaic characteristics model parameters to solve out equation, obtain photovoltaic characteristic curve under arbitrary light intensity and temperature. Finally, aiming at the four types of solar batteries, we carry out experimental validation, error results get from calculation and analysis to prove the effectiveness of the methods.1. The analysis of model parameters affecting the photovoltaic output characteristicsIn the condition of light, solar battery photovoltaic output can be regarded as diode characteristic approximately. With the voltage changes, the current changes exponentially, we can get the relationship between the current and voltage of the output characteristics from literature4, as is shown in equation（1）：()()-e1sq UIR sAKTpho pUIRIIIR(1)In the equation, I: Output current (A), U: Output voltage (V), Iph: Light born current (A), Rs: Series resistance (), Rp: Parallel resistance (K ), A: Diode ideal constant, Io: Diode reverse saturated leakage current (A), 3q: charge quantity, K: Boltzmann constant, T: Environment temperature ().Under the short circuit conditions, U = 0 ，I = Isc ，because the low voltage can not reach the diode turn-on voltage, the current is tiny, so that scphscspIII RR;Under the open conditions, U = Uoc ，I = 0 ，There is () (e1)ocqU AKT ophocpIIUR5-6. According to short and open conditions circuit, we can get (2)-(3): (1)phscsPIIR R(2)()ocqUocscsAKT oscpUI RIIe R(3)Arrange (1)-(3),both sides of the equation multiply the output voltage simultaneously, we can get P-U output characteristic equation that only contains A, Rs and Rp parameters，as shown in (4) and get the regular that the parameters affect the P-U curve ,as shown in figure 1. 00.0040.0080.0120.0160.0200.10.20.30.40.50.6U/VP/WA =1.0 A =1.25 A =1.50 A =1.75 A =2.0(a)The regular that the parameter A affect the P-U characteristic curve400.0040.0080.0120.0160.0200.10.20.30.40.50.6 U/VP/WRs =0 Rs =4 Rs =8 Rs =16 Rs = (b)The regular that the parameter Rs affect the P-U characteristic curve00.0040.0080.0120.0160.0200.10.20.30.40.50.6U/VP/WRp =0 Rp =30 Rp =60 Rp =100 Rp =(c)The regular that the parameter Rp affect the P-U characteristic curveFig.1 Influence results between model parameters to P-U characteristic curvesThe analytical result of figure 1 shows that open circuit voltage Uoc affects the endpoint location of P-U characteristic curve, ideal constant A of diode affects the curvature of the curve, series resistance (Rs) affects the rake ratio of the end segment of curve, and parallel resistance (Rp) affects the rake ratio of the initial segment of the curve. The photovoltaic array is made up of the parallel battery unit series, and the A, Rs and Rp parameters also has the characteristics of series and paralleling, this article only researches the sampling process of the battery unit parameters. 5According to the equivalent circuit characteristics, we define the parameters range that A 1, 2, Rs, 0, Rp , 0 under the limit state. we substitute the Isc and Uoc, and the upper and lower limit data of the model parameters into (4), then can get P-U boundary curve, as is shown in dotted line of figure 2, the solid part of