Grid Voltage Estimation and Current Control of Single-Phase Grid-Connected Converter without Grid Vo

Abstract

This paper investigates the possibility of estimating the grid voltage and controlling a single-phase grid connected converter without a dedicated grid voltage sensor. The main focus is given to current controlled architectures which need phase locked loops (PLL) for their operation. The grid voltage estimation method is proposed based on the active and reactive power delivered by the converter to the grid. In addition to the estimation of the grid voltage, the proposed method also generates the unit vectors and frequency information similar to a conventional PLL structure. The influence of various parameters like the dead-time, equivalent loss resistance, and the filter inductance on the proposed estimation method is studied in details.

Existing System

PLL Algorithm, line current shaping algorithm

Proposed System

This paper presented an estimation method of the grid voltage in single phase grid connected converter system without the need of a grid voltage sensor. The proposed method can be used as an alternative to conventional PLL structures which need a dedicated voltage sensor. The estimation algorithm was able to extract the fundamental component of the grid voltage under distorted grid conditions and generate the unit vectors from it. In addition, it gave an estimation of the grid frequency. The system model required for the controller design was presented. The effect of the dead-time on the proposed estimation method was studied and a model for the voltage drop due to the dead-time was developed. The effects of parameter mismatch, basically the filter inductor inductance and equivalent loss resistance, on the estimated voltage were also analyzed.

Architecture

A single-phase grid connected converter