## 7 Sustainable Transportation Applications Enabled by the Use of Matrix Converters
### More Electric Aircraft  
With the increasing growth of air traffic passenger demands, the aviation sector faces a wide set of new challenges. Civil aircraft represent 2.5% of the total carbon dioxide  
Figure 19: (a) Output voltage (b) output current of the current source rectifier (CSR).  
Figure 20: Simulation results of the proposed converter: input voltages (blue) and input currents (orange).  
emissions [139], a figure that will likely grow in the future years, not only due to the increasing demand of this sector, but also due to the transition of road transportation technologies to reduced carbon footprint transports such as EVs.  
More Electric Aircraft is a proposed concept in which the typical hydraulic, pneumatic and mechanical power sources that are required for all secondary power loads other than the aircraft thrust itself are replaced by electric power sources, promising increased efficiency, versatility, fault tolerance and weight reduction.  
Power electronics is the key enabling technology for electrification of aircraft [140], [141]. The need to build complex power systems with both AC and DC high-power buses at different voltages and different frequencies, while attaining extremely high power densities, is a current and a future challenge that yet requires more research and development.  
The inherent power density characteristics of matrix converters makes them good candidates to enable prominent technologies in the More Electric Aircraft, especially for AC/AC conversion [142].  
The use of a matrix converter as a ground power unit (GPU) has been proposed in [143] for the generation of high-quality 400 Hz three-phase supply featuring a 4 leg direct matrix converter.  
Matrix converters have also been proposed to convert power from the variable frequency generator (360 Hz-800 Hz) to a constant 400 Hz 110 VAC 3 Phase power bus [144] highlighting the minimum filtering requirements of the proposed solution. The use of indirect matrix converters as an interface between the generator and the 400 Hz bus is proposed in [145] where decoupled control strategies are provided for starting and generator operations. Matrix converters also allow the use of multi-phase generators such as shown in [146; 147], reducing the generators stress and increasing the overall reliability. New matrix converter-based topologies such as that proposed in [148] allow the creation of both a three-phase 400 Hz and DC buses using an indirect matrix converter with an additional intermediate stage for the regulation of a DC bus.  
Even though some authors do not consider the matrix converter as the preferred alternative for AC/DC conversion for More Electric Aircraft [142] several authors draw attention to the benefits of the use of matrix converters combined with high frequency transformers to create isolated DC buses [149]. Non isolated AC/DC matrix converters for aircraft use can also be found in literature [150], where authors suggest that the input power quality and the power density of the proposed converter makes it a desirable solution for large step-down voltage gains.  
Electro Mechanical Actuators (EMAs) are also a major component of the More Electric Aircraft where the use of matrix converters can be beneficial especially when the EMA supply is provided in AC. One particular application of a matrix converter as a brushless DC motor driver is presented in [151], where a fault tolerant controller is developed for a five-output phase matrix converter-based driver. A comparison between a single stage matrix converter and dual-stage CSI-VSI drivers for EMAs is presented in [151] revealing efficiency advantages of the use of a single stage direct matrix converter that ultimately leads to less heatsink requirements and, therefore, higher power density.