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Conventional finite control set model predictive control (FCS-MPC) presents high computational burden especially in three-level neutral point clamped (NPC) converters. This paper proposes a low-complexity optimal switching time modulated model predictive control (OST-M2PC) method for three-level NPC converter. In the proposed OST-M2PC method, the optimal switching time is calculated using a cost function. Compared to conventional FCS-MPC, the proposed OST-M2PC method has a fixed switching frequency as well as better power quality. The proposed OST-M2PC can operate at a 20kHz sampling frequency, reducing the computational burden of the processor. Simulation and experimental results validate the operation of the proposed method. Index Terms-Finite control set model predictive control (FCS-MPC), modulated model predictive control (M2PC), permanent magnet synchronous motor (PMSM), optimal switching time modulated model predictive control (OST-M2PC).

In this paper, the equivalent relationship between the nearest-three-virtual space vector (NTV 2 ) and carrier-based pulse-width-modulation (CBPWM) scheme is established based on space vector coordinate for a threelevel neutral-point-clamped (3L-NPC) converter. Moreover, to solve the neutral-point (NP) voltage imbalance problem of the studied 3L-NPC converter-fed high-speed drives, an active modulation strategy with the generalized bias-offset injection technique is proposed. Meanwhile, the excessive computational burden is significantly overcome by the fast calculation approach. The effectiveness of the proposed modulation algorithm is validated through both simulation and experimental results obtained from a 45 kW, 32 krpm aircraft electric starter/generator (ESG) prototype system.

This paper presents a new electricity power generation architecture for the engine system of more electric aircraft (MEA). A starter/generator (SG) is connected to highpressure (HP) spool, and a generator is attached to low-pressure (LP) spool. Their outputs supply a common DC bus. A back-toback (B2B) converter is connected between the AC sides of two generators. There are two main contributions of the proposed idea. First, some power can be transferred from LP shaft to HP shaft via the B2B converter, which will benefit to reduce the fuel consumption and increase compressor surge margin of the engine. Second, the HP starter/generator could operate in a high speed without flux weakening, hence the magnitude of stator current will largely decrease when output same active power, leading to the reduction of overall power losses. Modeling and control method design are illustrated. The effectiveness of proposed power generation architecture, engine performance improvement and power loss reduction are verified.

This paper introduces an advanced space vector modulation technique for three-level neutralpoint-clamped (3L-NPC) converters. The studied 3L-NPC converters within aircraft electric starter generator (ESG) systems normally operate at high modulation index, low pulse ratio and full power factor range for most of the operation time. Conventional modulation techniques exhibit large neutral point voltage ripple and possible voltage imbalance under such conditions. The increase of neutral point voltage ripple implies significant increase in converter capacitor size and decrease in capacitor reliability. The modulation technique introduced in this paper achieves improved neutral point voltage balancing within each switching period through enhanced applications of small vectors and restriction on medium vectors. The advanced implementation of small vectors is achieved using a sharing factor aided by a robust incremental current prediction procedure. With the predicted machine currents, the proposed method enables the optimum application of small vectors to balance the neutral point voltages. Simulation results based on a PLECS/Simulink model and experimental results obtained from a 45kVA, 32krpm aircraft electric starter generator prototype platform validate the reduction of the neutral point voltage ripple.INDEX TERMS Aircraft, electric starter generator (ESG), high-speed drive, three-level neutral-pointclamped converter, pulse width modulation, predictive control, state observer