Introduction - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 1

1
Introduction
In this chapter, an overview of the topic is given at first, followed by some basics about power
processing and some hardware issues relevant to the design of power inverters. Moreover,
wind power systems, solar power systems and smart grid integration are briefly described to
set the scene for the rest of the topic.
1.1 Outline of the Topic
After making an introduction in this chapter and presenting preliminaries in Chapter 2, the
topic is divided into four Parts: Power Quality Control (Chapters 3-9), Neutral Line Provision
(Chapters 10-14), Power Flow Control (Chapters 15-21) and Synchronisation (Chapters 22-
23). The overall structure of the topic is shown in Figure 1.1. Some chapters are related to
more than one part, which is not shown in Figure 1.1 but will be mentioned below.
Part I is devoted to the power quality issues of the current fed into the grid and the output
voltage of an inverter. A current controller is designed in Chapter 3 with the H ∞ repetitive
control strategy so that the current injected into the grid is clean. This chapter is also directly
linked to Part III under the category of current-controlled strategies. Several control strategies
are presented in Chapters 4-8 to address voltage quality issues based on different mechanisms.
In Chapters 4 and 5, the controllers are designed based on the H ∞ repetitive control strategy,
with different sets of feedback signals and different models. Both the voltage quality and the
current quality are addressed in Chapter 6 with a cascaded current-voltage controller, according
to the H ∞ repetitive control strategy. In Chapters 4-6, the voltage quality issues are addressed
essentially from the control point of view as a tracking problem. The voltage quality issue can
also be addressed involving fundamental understanding about the degradation mechanisms
of voltage quality. In Chapter 7, it is shown that the output impedance of an inverter can
be changed to obtain inverters with inductive, resistive and capacitive output impedances,