Modeling and Control of Modern Electrical Energy Systems

5Direct-Current (dc) DERs

In a dc distributed energy resource (DER) application, the power electronic converter interfaces two sides which are of dc nature, such as a solar photovoltaic (PV) panel, a battery, the rectified voltage of a wind turbine, a dc load, or a dc microgrid. Furthermore, vector control of a three-phase DER in synchronous reference frame ( frame) is also largely similar to a dc DER application. This chapter provides an understanding of the control system objectives and challenges pertaining to such a system. Various scenarios are studied and their control objectives are taken into consideration and addressed.

Special attention is paid to the ability of converter controller to limit its current against severe disturbances such as transient short circuits. Grid support functions including dynamic (inertia) and static (droop) supports are treated. Grid-forming versus grid-following controllers are studied. Aspects with using higher order filters (such as an LCL filter) are also studied. The PV application is studied in further particular details.

We use the linear quadratic (LQ) optimal control theory for the design of controllers. This leads to a systematic way of designing modular controllers which enjoy an inherent optimality and robustness as demonstrated throughout the chapter using various studies.

5.1 Introduction

An introduction comprising the description ...