In view of the problem of steady state oscillation and tracking drift existed in the traditional perturbation and observation method as well its derived method

the relationship between the step size

its perturbation period and steady-state oscillation phenomenon by the tracking algorithm is analyzed by way of establishing small signal model of MPPT process

the optimal range of perturbation step and period is obtained and

a kind of improved variable step MPPT algorithm is proposed with the combination of the ratio of power voltage slop and current as the criteria condition of new perturbation step and perturbation direction to improve effectively the problem of steady state oscillation and the emergence of drift phenomenon. The improvement of the new algorithm over the traditional algorithm in the steady oscillation and drift issue is verified by the simulation and the feasibility of the proposed algorithm is proved.