Page 147 - Modern Control of DC-Based Power Systems

CHAPTER FIVE

Control Approaches for Parallel
Source Converter Systems

This chapter is structured in the following way: First we start with cen-
tralized nonlinear control schemes. In Section 5.1 we introduce the
Linearizing State Feedback (LSF) where the nonlinearity is compensated.
Section 5.2 describes the Synergetic Control, which is a centralized
model-based control based on a manifold. In Section 5.3 the Immersion
and Invariance Control is presented, which designs a nonlinear control
law with guaranteed asymptote. In Sections 5.4 and 5.5 decentralized
control concepts are presented. Section 5.4 presents an Observer-based
control which decouples the power system on the basis of a Kalman filter
and results in a linear Two Degree Of Freedom (2DOF) controller. In
Section 5.5 a nonlinear Backstepping control law is presented which
combines two possible methods of power system decoupling. Method
one is based on a virtual current source, while method two relies on
power estimation which is based on an Adaptive Control law in
Section 5.6.In Section 5.7 we introduce a H N controller which offers
robustness and optimality in respect to uncertainties. In Section 5.8 we
explain the Sliding Mode Control (SMC) which has inherent robustness
properties and relies on the switching representation of the converters,
while the previous approaches use the state-space averaged model. The
chapter is summarized in Section 5.9 with a summary of the unique char-
acteristics of the presented control approaches.

5.1 LINEARIZING STATE FEEDBACK
In this section, a centralized nonlinear control method is considered
and later applied to a medium voltage DC (MVDC) system. It is called
the linearizing control technique [1]; other names often found in
literature are linearization via state feedback or loop cancelation [2]. This

Modern Control of DC-Based Power Systems. © 2018 Elsevier Ltd.
DOI: https://doi.org/10.1016/B978-0-12-813220-3.00005-3 All rights reserved. 111