Synchronous Power Control of Grid-Connected Power Converters under Asymmetrical Grid Fault

Weiyi Zhang,Joan Rocabert,J Ignacio Candela,Pedro Rodriguez

doi:10.3390/en10070950

Abstract

Control of grid-connected power converters is continuously developing to meet the grid codes, according to which the generation units should keep connected to the grid and further provide ancillary services, such as voltage and frequency support, negative sequence current injection, inertia emulation, etc. A virtual admittance controller is proposed in this paper for the objective of voltage support under asymmetrical grid faults. By using independent and selective admittances for positive and negative sequence current injection, the unbalanced voltage can be significantly compensated during asymmetrical faults. The controller is based on the generic control framework of the synchronous power controller (SPC), which is able to control a power converter with emulated and improved synchronous generator characteristics. Simulation and experimental results based on two paralleled 100 kW grid-connected power converters demonstrate the controller to be effective in supporting unbalanced voltage sags.

Highlights

Grid-connected power converters have been acting as an important interface between the renewables and the electrical grids
The conventional grid-connected power converters differ from synchronous generators mainly in the lack of the electromechanical characteristics
This paper develops a virtual admittance control structure, which is a part of the synchronous power controller (SPC) for grid-connected power converters

Summary

Introduction

Grid-connected power converters have been acting as an important interface between the renewables and the electrical grids. The conventional control of grid-connected power converters has been well validated in many applications and shows its effectiveness [1,2,3,4]. Along with the expansion of the renewable power generation plants, their impact on the power system has caused increasing attention [5,6]. The different performance of the converters compared to the traditional synchronous generators should be taken into account. The conventional grid-connected power converters differ from synchronous generators mainly in the lack of the electromechanical characteristics. The statics and dynamics of the renewable power generation units are both different compared with the synchronous generators

Methods

Results

Conclusion