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SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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Part III – SV Theory Applied to Sinusoidal BPMS Motor<br />

In Part III the SV models of a sinusoidal BPMS motor are derived. In the first section, the phasevariable<br />

electrical model of the synchronous machine is reduced to the two-phase model in the<br />

stationary reference frame (both the real-valued vector-matrix version and the complex-valued<br />

space vector version are given). Then the model is transformed to the rotor reference frame. The<br />

second section examines torque production in both frames. Finally, the third section gives the<br />

electromechanical simulation model in both frames.<br />

Electrical Models<br />

The phase-variable model of the brushless permanent magnet motor will be transformed into the<br />

stationary and rotor reference frames.<br />

Stationary Frame<br />

From Chapter 2 and Appendix B, the stator voltage equations are given by Equation (3.123),<br />

where the voltages are the line-neutral voltages. Equation (3.124) is the vector-matrix form. Since<br />

the inverter can apply voltages that contain a ZS component, we should rewrite the equations<br />

using the pole voltages. Although, when the Clarke (or SV) transform is used to express the<br />

variables in the stationary frame, the ZS component cannot be represented anyhow and the ZS<br />

component cannot drive any current so it seems there is no problem. However, this also means<br />

that the three circuits represented by Equation (3.123) are not independent, and this is a problem.<br />

It turns out that the math takes care of this—performing the derivation in terms of pole voltages<br />

(which requires use of the phase interference matrix) will yield the same results as those given<br />

here. Since using the terminal voltages is simpler, it is presented here and the explanation is<br />

deferred to Appendix D.<br />

vAN R iA Ls iA eA d<br />

v<br />

<br />

<br />

<br />

R<br />

<br />

i<br />

<br />

<br />

<br />

L<br />

<br />

i<br />

<br />

<br />

<br />

e<br />

<br />

BN B s B B<br />

dt <br />

v CN R i C L s i C e C <br />

(3.123)<br />

d<br />

vabc Riabc Lsiabc e<br />

abc<br />

(3.124)<br />

dt<br />

It is convenient to use the time derivative operator d / dt to combine the resistance and<br />

inductance matrices and eliminate the derivative of the current vector. In traditional general<br />

143

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