Development of Robust Starting System Using Sensorless Vector Drive for a Microturbine

This paper presents the development of a robust starting system for a microturbine (MT) with a single-shaft structure. Because the operating speed for the ignition and motoring of an MT is close to several tens of thousands of revolutions per minute, stable high-speed operation of the high-speed motor-generator (HSMG) is a critical issue in realizing a starting system for a single shaft. A sensorless vector inverter was developed for this high-speed operation. To successfully start an MT with the developed starter in practice, two new starting algorithms were proposed. One is a constant power output control algorithm that can maintain a perfect motoring schedule with significantly deteriorated performance of the input battery power in a vehicle under an extremely low temperature and severe engine drag. The other is a new reliable ignition verification logic that uses the inverter output current when the exhausted gas temperature sensor does not work properly. Since the two proposed algorithms are derived from the torque and $q$-axis current formulas for the vector drive, no additional hardware is required to apply them to an existing MT. In this paper, a single-shaft MT with a 10-kW inverter, 6-kW booster converter, and 25-kW HSMG was developed, and the proposed algorithms were applied to motoring. To verify the performance of the proposed algorithms, experiments were carried out under variable conditions, such as extremely low temperature $(-32\ ^{\circ}\hbox{C})$ and room temperature. The MT has used in a military truck for supplying electrical power and bleeding air.