A New Variable Step-Size P&O Algorithm with Power Output and Sensorless DPC Method for Grid-Connected PV System

Abstract

One of the popular topologies specially for low cost grid-connected photovoltaic systems is single-stage topologies. In these systems, the inverter is the only converter where both maximum power point tracking algorithm and grid side controller will be applied to it. Hence, the MPPT algorithm should be adapted with grid side controller for better transient response and to remove the internal control loops. One of the most popular MPPT algorithms and grid side controllers are P&O and direct power control, relatively. To combine them, an P&O with power output should be used. However, the response speed of controllers especially in single-stage system is very important. Therefore, since the dynamic of power is less than current or voltage, a fast P&O algorithm with power output is beneficial to exceed the transient response of the converter. Hence, a changing step-size P&O algorithm with power output is proposed in this paper. This controller regulates the power perturbation automatically, where the response speed of the system, power oscillations and accuracy in steady state can effectively improve. In addition, to reduce the hardware cost and size, a sensorless method is also presented for grid side controller.