TUTORIALS

Assist. Prof. Philippe Gray, PhD., 

University of Calgary, Canada

Dr. Philippe Gray received his B.A.Sc. (Hons.) degree in engineering science, M.A.Sc. and Ph.D. degrees in electrical engineering from the University of Toronto in 2010, 2013 and 2022, respectively. From 2012 to 2013, Dr. Gray was a Visiting Researcher at ABB Corporate Research in Västerås, Sweden. From 2014 until 2017, he was a System Design Engineer at General Electric in Stafford, UK, working on high-voltage direct current (HVDC) transmission schemes. From 2022 until 2023, Dr. Gray was a Senior Power Electronics Engineer at Lucid Motors in California, where he worked on the onboard charger design. He is currently an Assistant Professor in the Schulich School of Engineering at the University of Calgary. His research interests include developing advanced power electronic converter technologies and resolving system-level integration challenges in future converter-dominated grids.

One of the next frontiers for dc grid technology will be last mile of power delivery. For dc to be pervasive at distribution voltage levels, dc-dc converters for tapped power applications with low-cost and high-efficiency potential will be required. These converters would serve a similar function to a secondary distribution transformer in ac grids. Recently a new class of converters has been introduced for this purpose, termed the current shaping modular multilevel dc–dc converter (CS-MMC). Due to the combined use of current source and voltage source modules, no internal string inductors are required, enabling high effective frequencies to be achieved. In this presentation, an overview of the CS-MMC converter class will be presented along with some of the latest research findings into a bidirectional current-fed multilevel structure with zero-current switching with a primary application being direct charging of a high-voltage battery from a medium-voltage dc line.

Nowadays, with an increased share of renewable energy sources and rapid development of the vehicle-to-grid (or so-called V2G) technology, the power grid has become a more interconnected network of different sources and loads. This evolution also increases the demands from medium-voltage circuit breakers (MVCBs), in terms of both more controlled and higher number of switching operations. Therefore, next-generation MVCBs must exhibit higher endurance, as well as fast and accurate switching capability. Compared to classical spring-based devices, MVCBs driven by electromagnetic (EM) actuators are inherently more controllable, and they have longer lifetime owing to a reduced number of moving parts. Therefore, EM actuation is a key enabler to meet the increasing demands of the future power distribution grids.

This tutorial provides a review of the state-of-the-art linear electromagnetic actuators used in power distribution grid control and protection apparatus, such as circuit breakers. Firstly, key actuation requirements of the considered application are summarized. Then, different classes of actuators are introduced. Their key operating principles are comparatively discussed using example cases of known actuator solutions from literature. 

Ton Duc Do 

To protect our planet and tackle the global warming, electric vehicles (EVs) become an important solution to replace the gasoline vehicle. Being supported by relative technologies like motor design, motor drives, and wireless power transfer, EVs have grown up considerably all over the world. Especially, the practical application of in-wheel-motor (IWM) allows many revolutionary development in the field of EV. This makes IWM-EV to be a novel and advanced motion control system. This presentation will focus on the most primary issue of IWM-EV. It is called traction control, which generates the proper motion between the wheels and the road surface. The most challenge is to design the traction control system which operates stably and robustly under the nonlinearity of vehicle dynamics and the variation of road friction. To this end, we have proposed and developed several approaches. (i) By treating each wheel as a local agent, it is possible to optimally control the slip ratios via a hierarchically linear quadratic regulator. (ii) On the other hand, passivity theory can be utilized to distributed the motor torque to each wheel to simultaneously achieve two objectives: minimization of energy consumption and whele slip prevention. (iii) Recently, we have validated some advanced techniques for driving force control by estimating the road condition using on-board sensors. In addition, the classical circle criterion has been shown a theoretical framework to guarantee system stability of driving force control. The aforementioned studies will be introduced together with the experimental results using real vehicles, joint-research results with the industrial circles, and educational activities for both Vietnamese and Japanese students.

Phuong Nguyen 

With the requirements for high-performance operation of traction machines in EV application, the demagnetization of permanent magnets (PM) can occur, depending on the temperature, current magnitude, current phase angle, designed PM operating point, or combined effect of the above factor. This tutorial  will  comprehensively introduce the effect of design factors and operation characteristics in the motor, such as permanent magnets (PMs), flux barriers (FBs), characteristic current (Ich), impact of excitation current, current phase angle, and the field weakening (FW) under high temperature and high current density operations, on the demagnetization problems of interior PM (IPM) and permanent magnet-assisted synchronous reluctance motors (PMa-SynRM). 

The “demagnetization ratio” as an index is applied to evaluate the demagnetization level of PM in the motor. First, the motor performance over a wide speed range is analyzed. Then, the impact of demagnetization on the flux density distribution and the proportion of motor torque components, i.e.,  reluctance  torque  and  electromagnetic  torque,  associated  with  different  PM  and  FB arrangements,  is  evaluated.  The  analysis  results  reveal  the  relationship  between  PM demagnetization and design parameters, and also the impact of high current phase angle combined with the effect of high temperature is the major cause of irreversible demagnetization. In addition, when PM demagnetization problems occur, it affects the air gap flux density and electromagnetic force distribution on the stator frame of the motors. This leads to an increase in the acoustic noise and vibration of the motors. Therefore, with the proper designs, the demagnetization issue in the motors can significantly improve, and the acoustic noise and vibration are reduced without much affecting the performance of the motors. Finally, Finite element analysis (FEA) is used to evaluate and validate the studies.