A Sensorless Power Reserve Control Strategy for Two-Stage Grid-Connected PV Systems

Abstract

Due to the still increasing penetration of grid connected Photovoltaic (PV) systems, advanced active power control functionalities have been introduced in grid regulations. A power reserve control, where namely the active power from the PV panels is reserved during operation, is required for grid support. In this paper, a cost-effective solution to realize the power reserve for two-stage grid-connected PV systems is proposed. The proposed solution routinely employs a Maximum Power Point Tracking (MPPT) control to estimate the available PV power and a Constant Power Generation (CPG) control to achieve the power reserve. In this method, the solar irradiance and temperature measurements that have been used in conventional power reserve control schemes to estimate the available PV power are not required, and thereby being a sensorless approach with reduced cost.

Existing System

Photovoltaic Array Maximum Power Point Tracking Techniques.

Proposed System

A cost-effective sensorless power reserve control strategy for two-stage grid-connected PV systems has been proposed in this paper. The cost-effectiveness of the proposal lies in the sensorless estimation of the available PV power, which is achieved by routinely employing a fast MPPT operation. Then, the estimated available power is used for calculating the set-point to limit the extracted PV power with the CPG operation. At the grid-side, the stored energy in the dc-link is adaptively controlled to minimize the power fluctuation during the available PV power estimation process, where the excessed energy is temporarily stored in the dc-link.

Architecture

System configuration and control structure of a two-stage grid connected PV system with the Sensorless Power Reserve Control strategy