Predictive Control of Three Phase AC/DC Converters

4 CHAPTER 1. INTRODUCTION
trol in three phase inverters [19], [20], [21], [22], [23], [24], [25], [26], [27], [28],
rectifiers [29], [30], active filters [31], [32], power factor correctors [33], power
factor preregulators [34], [35], uninterruptible power supplies [36], [37], [38], DC-
DC converters [39] and torque control of induction machines [40]. This method
is being used, when a fast dynamic response is required. However, parameters
mismatch, unmodeled delays, and other errors in the model deteriorate control
performance.
Model Predictive Control (MPC) has been successfully used in practical applications
in recent decades. Theoretical results and applications have been presented
in many books and survey papers [41], [42], [43], [44], [45], [46], [47], [48].
The MPC can be divided into two main groups: with continuous control sets,
where modulator realizes switching states, and finite control set MPC, which
directly controls power converter switches.
Feature VSF CSF
Switching Variable Constant
frequency
SVM blocks No No
Coord. trans. No No
Direct control of: Line powers Line powers
Estimation of: Virtual Flux Virtual Flux
and Powers and Powers
Current ripple High Low
Sampling High Low
frequency
Line voltage Yes Yes
sensorless
Table 1.2: Comparison of predictive control methods
The finite control set method (FS-MPC) meets very well discrete nature of
power converters. Taking into account the finite set of possible switching states
of the power converter, which depends on the possible combinations of the “on”
and “off ” switching states of the power switches, the optimization problem is
reduced to the evaluation of all possible states, and selection of the one which
minimizes value of the defined cost function. In view of switching frequency the
FS-MPC methods can be divided into two groups: Variable Switching Frequency
(VSF) and Constant Switching Frequency (CSF). Both approaches have been
briefly compared in Tab. 1.2. Although, one advantage of predictive control
is that its concepts are very simple and intuitive. Using predictive control it is
possible to avoid the cascaded structure, which is typically used in a linear control
scheme. However, power converters are nonlinear systems. Additionally, the
dynamic of cascade structure is limited because of use conventional PI controllers,