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The high-order harmonics caused by traditional fixed switching frequency space vector pulse width modulation (SVPWM) technology cause serious electromagnetic interference problems in electric drive systems. Random switching frequency (RSF) SVPWM can be used to solve the problem of severe electromagnetic interference. The principles of SVPWM technology and RSF-SVPWM technology are introduced, and the influence of the increase of the spread spectrum range in RSF-SVPWM strategy on the system is discussed. To achieve good dispersion of high order harmonics in a small spread spectrum range, a novel RSF-SVPWM strategy based on dual frequency division is proposed. Taking the original central switching frequency as the midpoint, the initial complete variation range is divided into two local frequency bands, and their local central frequency points and local spread spectrum range are set. Taking the positive and negative of the ideal β axis voltage component in the two-phase static α-β coordinate system as the standard, after judging the specific frequency division band of each switching cycle, the switching frequency is randomized around the local central frequency point in the frequency division band. The simulation and experimental results show that compared to the traditional RSF-SVPWM strategy with a wider spread spectrum range, the new RSF-SVPWM strategy has equivalent high order harmonic dispersion effect. At the same time, the new RSF-SVPWM reduces the pulsation of the system current loop and outputs a relatively stable electromagnetic torque. The new RSF-SVPWM promotes the application of electric drive systems in high-end industry fields.

From the perspective of portable monitoring devices,we use an analog front-end AFE4490 design a module of Non-invasive blood oxygen measurement, used to collect human pulse wave signal and peak (valley) value detection and then use the principles of non-invasive oximetry calculated oxygen saturation (SPO2). This design of noninvasive oximetry module has the characteristics of small size, low power consumption, and the results of test show that the measurement of oxygen saturation are correct.