Hairpin windings are gaining increasing popularity in recent years due to their advantages in improving electrical machine performance while reducing manufacturing time and costs. Their geometrical features introduce new challenges and opportunities on thermal management. In particular, spray cooling is increasingly being used, since hairpin windings open up regular and accurately defined gaps in the end-windings compared to the traditional random windings. To date, technical literature on the effectiveness of spray cooling with hairpin windings is lacking, with no practical guidelines available to researchers. In this article, taking an existing hairpin-wound stator, a test rig is developed to investigate the cooling ability of different spray cooling setups on the end-windings. Three types of commercial spray nozzles are chosen to carry out a series of experiments, varying the oil flow rate, pressure, outlet velocity, and number of nozzles. The winding temperature and heat transfer coefficients are presented and discussed. Furthermore, the efficiency of spray cooling is reviewed based on the experimental results. Finally, suggestions on designing similar cooling setups and increasing the cooling efficiency are also provided.

In fuel cell vehicles, the output voltage of the fuel cell source is typically much lower than the voltage required by the DC bus and also this output voltage drops significantly as the output current increases. In order to match the output voltage of the fuel cell source to the DC bus voltage, a new DC-DC boost converter with a wide input range and high voltage gain is proposed to act as the required power interface, which reduces voltage stress across the power devices and operates with an acceptable conversion efficiency. A prototype rated at 300W/400V has been developed and the maximum efficiency of the proposed converter was measured as 95.01% at 300W. Experimental results are presented to validate the effectiveness of the proposed converter.

In this paper, a hybrid switched-capacitor/ switched-quasi-Z-source bidirectional dc-dc converter is proposed for electric vehicles (EVs) with hybrid energy sources, which has a wide voltage gain range in the bidirectional energy flows. Compared with the traditional quasi-Z-source bidirectional dc-dc converter, the proposed converter only changes the position of the main power switch, and employs a switched-capacitor cell at the output of the high voltage side. Therefore, the advantages of the wide voltage gain range and the lower voltage stresses across the power switches can be achieved. The operating principle, the voltage and current stresses across the power switches and the comparisons with other converters are analyzed in detail. Furthermore, the parameter design of the main components, the dynamic modelling analysis and the voltage control scheme are also presented. Finally, the experimental results obtained from a 400W prototype validate the characteristics and the theoretical analysis of the proposed converter.

A common ground switched-quasi-Z-source bidirectional dc-dc converter is proposed for electric vehicles with hybrid energy sources. The proposed converter is based on the traditional two-level quasi-Z-source bidirectional dc-dc converter, changing the position of the main power switch. It has the advantages of a wide-voltage-gain range, a lower voltage stress across the power switches, and an absolute common ground. The operating principle, the voltage and current stresses on the power switches, the comparisons with the other converters, the small signal analysis, and the controller design are presented in this paper. Finally, a 300 W prototype with U _high = 240 V and U _low = 40~120 V is developed, and the experimental results validate the performance and the feasibility of the proposed converter.

In practice, sensorless drive systems of interior permanent magnet synchronous motors (IPMSMs) are usually working in highly utilized conditions where fast changing uncertain loads, inverter losses, magnetic saturation and other disturbance exist. These issues could reduce the performance and stability, which become the main vulnerability of sensorless drives. Linear extended state observer (LESO) or Q-PLL is conventionally adopted to estimate the speed and position. Without compensation or adaptive methods, fast changing uncertainties cannot be observed thoroughly. In this paper, a third order super-twisting extended state observer (STESO) is proposed to enhance the dynamic performance of position and speed estimation for IPMSM. Utilizing the high-order extended state and super-twisting algorithm, fast convergence and disturbance estimation can be achieved in STESO. The effectiveness and stability of STESO are analyzed and an optimized parameter selection method is presented. Comparative experimental results between the LESO and STESO verify the effectiveness and improvement of the proposed STESO against rapid speed and load variations.