BEGA Starter/Alternator—Vector Control Implementation and Performance for Wide Speed Range at Unity Power Factor Operation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The Biaxial Excitation Generator for Automobiles (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles. This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range. A vector control structure is proposed for BEGA operation during motoring and generating, at unity power factor with zero <formula formulatype="inline"><tex Notation="TeX">$d$ </tex></formula>-axis current <formula formulatype="inline"><tex Notation="TeX">$(i_{d})$</tex></formula> and zero <formula formulatype="inline"><tex Notation="TeX">$q$</tex></formula>-axis flux <formula formulatype="inline"><tex Notation="TeX">$(\Psi_{q})$ </tex></formula> control. In such conditions, BEGA behaves like a separately excited dc brush(commutator) machine, in the sense that no stator inductance voltage drop occurs in such constraint control conditions. A high <formula formulatype="inline"><tex Notation="TeX">$i_{q}$</tex></formula> current is required in order to cancel the <formula formulatype="inline"><tex Notation="TeX">$q$</tex></formula>-axis flux, during unity power factor operation. This engages higher copper losses in the machine under light load. In order to minimize the copper losses, for lower load levels, a current referencer is proposed. Due to higher dc field excitation time constant, the dc field current response is not very fast, particularly for high-current excursion. In order to increase the torque response quickness, the <formula formulatype="inline"><tex Notation="TeX">$d$</tex></formula>-axis current <formula formulatype="inline"><tex Notation="TeX">$i_{d}$</tex> </formula> is controlled with a nonzero reference value only during transients, when there is a difference between the reference and measured dc field currents. This way, high dynamic performance is secured. Implementation, digital simulation, and experimental results validate the proposed solutions. </para>