Yuzheng Chen

High-speed Permanent Magnet Synchronous Machine (PMSM) sensorless control design is not without challenges, especially when the ratio of power electronic modulation frequency to electrical fundamental frequency (M-F ratio) is relatively low. The Model Reference Adaptive System (MRAS) is a mature sensorless control method and has been widely used in industrial drives. There, an observer is commonly used to estimate rotor speed and angle using machine voltages and currents. The estimated angle is then further implemented for voltage and current frame transformations. Thus, the MRAS sensorless control is indeed a strong-coupled, multi-variable and nonlinear system. This paper proposes a detailed MRAS sensorless control system design method in discrete-time domain for high speed drives with relatively low M-F ratio with good system stability confidence. A detailed discrete local-linearized small-signal model is developed and state-space evolution matrix of current closed-loop system has been derived. The system stability can be defined and analysed with its maximum eigenvalue and the controller design is to make sure that the maximum eigenvalue is falling within the stable region. This proposed design method has been validated on a dual three-phase PMSM by simulation and experiment results with selected stable design point.

This article shares with the aerospace community a case study of turboprop mild hybridization using a recently developed integrated drive system in the University of Nottingham, U.K., within the ACHIEVE project under EU H2020 CleanSky 2 program (project No. 737814). The developed drive system enables the green taxiing of a turboprop aircraft while on the ground with its engine OFF and as an electrical generator when the turboprop is in the air. The entire system is designed to be able to integrate within the power auxiliary gearbox (PAGB) of a turboprop aircraft. Some of the key features of the developed system include a high-speed permanent magnet machine (up to 14200 rpm) with a dual-three-phase design, silicon carbide (SiC)-based high power density (11.8 kW/L for the power converter, and 35.3 kW/L and 7.2 kW/kg for the machine active parts), integrated cooling design for high-temperature operation ( $>130~^{\circ }\text{C}$ ambient temperature), fault tolerance consideration with dual-channel operation capabilities, and sensorless control for entire operational conditions. This article is giving an overview of the design process of the electrical machine, power converters, and the cooling of the entire drive. The numerical analysis [finite element method (FEM) and computational fluid dynamics (CFD)] and some experimental results are presented to demonstrate the effectiveness and the desired performance of the developed integrated drive system.

This paper developed a dynamic hybrid field model (DHFM) for surface-mounted permanent magnet (SPM) motors coupled with external drive circuit considering motor saturation. In the proposed model, the iron saturation of SPM motor is equivalently replaced by the saturation current in the slot opening and therefore the analytical solution of the air-gap field is determined. Based on the air-gap field, the total flux linkage and electromagnetic torque is calculated. The instantaneous inductance is also derived from DHFM using frozen permeability method. The instantaneous back-EMF is determined by the flux linkage produced by PM separating from the total flux linkage. Hence, according to the circuit model and mechanical model, the winding current at next step can be obtained. The proposed model is more efficient in terms of computation and its accuracy is validated by FEM results.

Recent advancements in the power electronic device technologies, such as wide-band-gap devices including Silicon-Carbide (SiC) and Galium-Nitride (GaN), are acting as an enabling factor in development of compact power electronic systems. More specifically, the concept of More Electric Aircraft (MEA), which requires the aircraft's pneumatic systems to be replaced by electrical systems, can therefore greatly benefit from these emerging technologies in reduction of weight and volume of the aircraft such that range of aircraft can be increased. Various functions of aircraft e.g. actuation and engine-starting in MEAs are performed by power electronic converter based systems. With SiC and GaN devices, converters with densities even up to 70kW/L are easily achievable only when the envelope of the converter is cubical and not restricted. However, in case when a specific envelope is provided by the aircraft manufacturer, the component selection, layout and the design of power electronic converter to achieve high power density, within the restricted envelope, becomes extremely challenging. This paper presents the design of a circular-shaped 17.5kW/L – 97.6% efficient- SiC based two-level (2L) inverter for aircraft applications. Furthermore, the feasibility and design of the converter are supported by the experimental results rated at a power of 13kW.

A flux-weakening control algorithm with an improved stator flux linkage command's adjustment part of interior permanent magnet synchronous motors is proposed in this paper. The current commands are derived from lookup tables, which consider variation of motor parameters. The merits of this algorithm are the maximization of torque and high torque stability. Experimental results are demonstrated to verify the effectiveness of the proposed algorithm.

An improved torque feedforward control algorithm of interior permannet magnet synchronous machines (IPMSMs) is proposed in this paper. A new structure of reference current lookup table is proposed, calculating a cubic polynomial instead of traditional interpolation. This method saves data storing space and decreases computing time. Furthermore, a stator flux linkage and torque commands adjustment algorithm is proposed to increase the maximum torque output and decrease the fluctuation of torque. The optimal coefficients of the proposed algorithm is obtained through simulation and the simulation results vertify the improved torque performance of the proposed algorithm.

A maximum torque per ampere (MTPA) control based on virtual signal injection for interior permanent magnet synchronous motor (IPMSM) with fast dynamic response is proposed in this paper. A small square wave signal is mathematically injected into current angle for accurately tracking MTPA points. The extracted derivative of elctromagnetic torque is utilized to compensate the initially set current angle to the real MTPA operation current angle. Due to the absence of bandpass and lowpass filters which are essential in the sinusoidal injected signal scheme, this method shows good dynamic response. By incorporating a modified equation for the torque after signal injection, the steady-state accuracy is also enhanced. The d- and q-axes current references are obtained through the current vector magnitude and optimal current angle instead of using the torque equation with nominal motor parameters, which guarantees the accuracy of the output torque. The proposed scheme is parameter independent and no real signal is injected to the current or voltage command. Thus, the problems of high-frequency signal injection method are avoided. A prototype is set up and experiments are carried out to verify effectiveness and robustness of the proposed control scheme.

This paper proposes an improved stator flux control algorithm based on the torque feedforward control technique for interior permanent magnet synchronous motor (IPMSM). The proposed flux linkage control algorithm can prevent the d and q- axis voltages from saturation and improve the dynamic behavior. A lookup table is used in the torque feedforward control technique, which outputs the desired d and q-axis currents according to the two inputs: torque command and desired stator flux linkage magnitude. The method of constructing lookup table is mentioned. Simulations are carried out. The results prove the effectiveness of the proposed method.