Design og kontrol af Ground Power Units / Design and Control of Ground Power Units

The project was initiated by Axel Akerman A/S in order to develop and improve one of their main competences : Development and Production of Solid-State Ground Power Units. The project has its focus on the output performance and on the system design. The technical demands to the product increase due to the introduction of new airplane models and equipment. Nonlinear loads caused by electronic equipment in the airplane (e.g. TV, audio, power supply) equipped with diode rectifiers causes non-sinusoidal currents to be drawn from the GPU. These will cause voltage distortion at the output of the unit. The settling time at load changes should be in the range of 2-3 ms for the fundamental output voltage. Artificial methods for compensation of the distortion were developed and compared. to compensate for the harmonic distortion. Advanced cable models have been developed and a new compensation scheme has been presented that compensates for the cable voltage drop with both balanced and unbalanced loads. To save space/reduce the price of the unit, the passive output filter and the output transformer (galvanic isolation is required by regulations) should be as small as possible. The output filter reduces the inverter-induced distortion and the filter size can only be reduced, if the distortion level is reduced. Investigations on the inverter-filter-transformer system are therefore very relevant. The project is sponsored by the Danish Academy of Technical Science. (Uffe Borup, Frede Blaabjerg, John K. Pedersen; Bo Vork Nielsen, Soren Dahl, Axel Akerman A/S)