Abstract
The high dv/dt and di/dt outputs from power devices in a high-low voltage DC-DC converter on electric vehicles (EVs) can always introduce the unwanted conducted electromagnetic interference (EMI) emissions. A conducted EMI prediction and mitigation strategy that is based on transfer function for the high-low voltage DC-DC converter in EVs are proposed. A complete test for the DC-DC converter is conducted to obtain the conducted EMI from DC power cables in the frequency band of 150 kHz-108 MHz. The equivalent circuit with high-frequency parasitic parameters of the DC-DC converter is built`1 based on the measurement results to acquire the characteristics of the conducted EMI of the DC power cables. The common mode (CM) and differential mode (DM) propagation coupling paths are determined, and the corresponding transfer functions of the DM interference and CM interference are established. The simulation results of the conducted EMI can be obtained by software Matlab and Computer Simulation Technology (CST). By analyzing the transfer functions and the simulation results, the dominated interference is the CM interference, which is the main factor of the conducted EMI. A mitigation strategy for the design of the CM interference filter based on the dominated CM interference is proposed. Finally, the mitigation strategy of the conducted EMI is verified by performing the conducted voltage experiment. From the experiment results, the conducted voltage of the DC power cables is decreased, respectively, by 58 dBμV, 55 dBμV, 65 dBμV, 53 dBμV, and 54 dBμV at frequency 200 kHz, 400 kHz, 600 kHz, 1.4 MHz, and 50 MHz. The conduced voltage in the frequency band of 150 kHz–108 MHz can be mitigated by adding the CM interference filters, and the values are lower than the limit level-3 of CISPR25 standard (GB/T 18655-2010).
Highlights
Electric vehicles, as the new energy products of energy conservation and environmental protection, have gradually become the focus of consumers’ attention [1]
The fast switching of these power semiconductor devices like MOSFET, IGBT, used in the high-low voltage DC-DC converter is controlled by pulse width modulation (PWM), resulting in the conducted electromagnetic interference (EMI) of electric vehicles (EVs)
The conducted EMI of the high-low voltage DC-DC converter mainly comes from the common mode (CM) interference
Summary
As the new energy products of energy conservation and environmental protection, have gradually become the focus of consumers’ attention [1]. In the narrow space of EVs, the high-voltage system, including the motor drive system, DC-DC converter system, and on-board charger, etc., and the low-voltage system, Energies 2018, 11, 1028; doi:10.3390/en11051028 www.mdpi.com/journal/energies. Energies 2018, 11, 1028 such as the battery management system (BMS), the vehicle control units (VCU), and malfunction detecting and recording instrument are applied [2]. The fast switching of these power semiconductor devices like MOSFET, IGBT, used in the high-low voltage DC-DC converter is controlled by pulse width modulation (PWM), resulting in the conducted electromagnetic interference (EMI) of EVs. Besides, the conducted-EMI may generate some radiated EMI to influence or even damage a part of onboard components, such as wireless devices, analog devices, sensors of EVs, etc.
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