Predictive Control of Three Phase AC/DC Converters

Chapter 3
Control Strategies for VSC
3.1 Overview
Several control methods for VSC has been proposed. According to [1] and [4]
these methods can be divided as follow:
• Voltage Oriented Control (VOC),
• Direct Power Control (DPC),
• Direct Power Control with Space Vector Modulator (DPC-SVM).
For line voltage sensorless operation, also concept of Virtual Flux has been presented
[9], [10].
In this Chapter these three groups will be described and characterized.
3.2 Voltage Oriented Control
Voltage Oriented Control - VOC, due to high dynamic and static performance, via
internal current control loops, became very popular, and has been permanently
improved.
The goal of the control system (Fig. 3.1) is to regulate DC-link voltage U DC
to follow reference value U DCref , while line current should be sinusoidal shape
and in phase with line voltage. VOC uses line currents i Labc , line voltages u Labc ,
and DC-link voltage U DC measurements. On the basis of DC-link voltage error
U DCerr , PI controller generates reference value of current in d axis I dref . To fulfill
unity power factor condition, referenced value of I qref current is equal to zero.
Next, current errors are delivered to PI controllers that generate commanded
VSC voltages U P dqref . After transformation into αβ coordinates, U P αβref are
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