The conversion and utilisation of renewable energy generations often require grid-connected inverters. When applying LCL filter to remove power electronic chopping harmonics, the power quality faces two issues of resonance damping and grid voltage induced current distortion. Conventionally, two separate control algorithms are required to treat the two issues, requiring an additional current sensor, increasing control complexity and limiting performance. This study demonstrates that linear active disturbance rejection control (ADRC) is able to treat both resonance damping and grid voltage induced current distortion as overall disturbance at the same time through a single structure, while achieving higher power quality for dynamic, steady-state, small and large parameter setup, as well as parameter variations, as validated by experimental results. In principle, the ADRC can be configured with or without knowledge of the system model. This study also reveals that it is the measurement noise tolerance that makes the two configurations different in practice. By using model information in ADRC algorithm, the required bandwidth can be reduced, offering more tolerance to measurement noise. Moreover, the ADRC controller has only two parameters to tune for 'fast' or 'slow', which makes it easy for implementation.
This study introduces an innovative thermal model to accurately consider the heat transfer in the winding and end region of forced air-cooled motors, which is an attractive supplement of classical lumped parameter thermal network approaches. Through coupling of the analytical method and local numerical calculations, the effective length of the winding heat path and the air convection of the end region can be exactly considered. An improved analytical derivation of the equivalent thermal conductivity of the winding is applied. To reduce the errors caused by the irregular slot type, the winding thermal resistance is calculated by the 2D numerical calculations. After that, the 3D model of the end region is built to accurately calculate the end air velocity and end convection resistance. The unknown boundaries of the 3D end model are determined by a coupling iteration. The errors of the winding thermal resistance and end convection resistance are less than 3.12 and 11%, respectively, verified by simulations and temperature tests of the prototype. Finally, the mechanism of the end region convection and its influence on the temperature rise of the entire motor are discussed in detail.
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