Gradationally Controlled Voltage Inverter for More Electric Aircrafts 2019-01-1913

Over recent decades, there has been a lot of progress toward a more electric aircraft (MEA) to reduce emissions and fuel consumption. In MEAs, many subsystems that previously used hydraulic or pneumatic power have been replaced by electrical systems with inverters and electrical machines. Therefore, MEAs reduce the weight, i.e. fuel consumption, and maintenance cost. To achieve advanced electrical systems, the weight of inverters has significant importance. In this work, a gradationally controlled voltage (GCV) inverter is proposed to reduce the weight and enhance reliability. A GCV inverter can supply gradational quasi-sinusoidal voltages combining two different voltages from a 3-phase 3-level (main) inverter and three single-phase H-bridge (sub) inverters. A dc power supply is required only for the main inverter. A main inverter with Si-IGBTs supplies the fundamental voltage by only one switching in the fundamental period. Consequently, the switching loss is minimized and hence the weight of cooling systems can be reduced. Sub inverters, which have the half of dc-link voltage of the main inverter, employ SiC-MOSFETs with higher switching frequency and compensate for the sinusoidal voltage reference. Thus, a GCV inverter can supply quasi-sinusoidal voltages with low dv/dt. In addition, sub inverters cancel common mode (CM) voltages, which cause electromagnetic interference (EMI) noises, caused by the main inverter.　Therefore, a GCV inverter can reduce the weight required for passive filters that suppress dv/dt voltages and EMI noises using massive inductors. Furthermore, when sub inverters have faults, a GCV inverter can continue operation using the main inverter for all torque and machine speed. In a full paper, the circuit configuration and control method of the proposed GCV inverter are described. The operation with low losses and low noises is verified by simulations.