Mitigation Emission Strategy Based on Resonances from a Power Inverter System in Electric Vehicles

Abstract

Abstract:Large dv/dt and di/dt outputs of power devices in the DC-fed motor power inverter can generate conducted and/or radiated emissions through parasitics that interfere with low voltage electric systems in electric vehicles (EVs) and nearby vehicles. The electromagnetic interference (EMI) filters, ferrite chokes, and shielding added in the product process based on the "black box" approach can reduce the emission levels in a specific frequency range. However, these countermeasures may also introduce an unexpected increase in EMI noises in other frequency ranges due to added capacitances and inductances in filters resonating with elements of the power inverter, and even increase the weight and dimension of the power inverter system in EVs with limited space. In order to predict the interaction between the mitigation techniques and power inverter geometry, an accurate model of the system is needed. A power inverter system was modeled based on series of two-port network measurements to study the impact of EMI generated by power devices on radiated emission of AC cables. Parallel resonances within the circuit can cause peaks in the S21 (transmission coefficient between the phase-node-to-chassis voltage and the center-conductor-to-shield voltage of the AC cable connecting to the motor) and Z11 (input impedance at Port 1 between the Insulated gate bipolar transistor (IGBT) phase node and chassis) at those resonance frequencies and result in enlarged noise voltage peaks at Port 1. The magnitude of S21 between two ports was reduced to decrease the amount of energy coupled from the noise source between the phase node and chassis to the end of the AC cable by lowering the corresponding quality factor. The equivalent circuits were built by analyzing current-following paths at three critical resonance frequencies. Interference voltage peaks can be suppressed by mitigating the resonances. The capacitances and inductances generating the parallel resonances and responsible elements were determined by the calculation through the equivalent circuits. A combination of mitigation strategies including adding common-mode (CM) ferrite chokes through the Y-caps and the AC bus bar was designed to mitigate the resonances at 6 MHz, 11 MHz, and 26 MHz related to the CM conducted emission by IGBT switching and the radiated emission of the AC cable. The values of Z11 decreased respectively by 15 dB at 6 MHz, 0.4 dB at 11 MHz, and 11.5 dB at 26 MHz and the values of S21 decreased respectively by 8.6 dB at 6 MHz, 7 dB at 11 MHz, and 6.3 dB at 26 MHz. An equivalent model of the power inverter system for real-time simulation in time domain was built to validate the mitigation strategy in simulation software PSPICE.

The Effect of Distributed Parameters on Conducted EMI from DC-Fed Motor Drive Systems in Electric Vehicles

“…A rather simple measurement-based SPICE model of the motor power inverter has been presented [12] to quickly identify the parts responsible for EMI and help predict resonances between the two ports of the motor power inverter by a straightforward correlation between the system geometry and the parasitic circuit elements [27]. A detailed analysis of current paths and the equivalent circuits at three important resonance frequencies have been presented to determine the EMI propagation path in the Energies 2017, 10, 1 3 of 17 motor drive system [6]. A combination of mitigation strategies was designed to mitigate the CM conducted emission by IGBT switching and the radiated emissions of AC cables.…”

“…Electromagnetic interference (EMI) considerations in EVs have become increasingly important, as the electromagnetic compatibility (EMC) regulations for EVs (typically defined from 10 kHz to 30 MHz) have become more stringent [6]. The DC-fed motor drive system of EVs, consisting of the electric motor, power inverter, and electronic controller has an essential role in EVs [7].…”

A Topology-Based Approach to Improve Vehicle-Level Electromagnetic Radiation

“…This technique can be used in the high frequency range, but the whole system is required to be modeled to acquire the network parameter. Reference [19] studied the EMI generated by the power inverter system in EV based on series of a two-port network.…”

A Parametric Conducted Emission Modeling Method of a Switching Model Power Supply (SMPS) Chip by a Developed Vector Fitting Algorithm

“…This method directly establishes the CE model of SMPS for analysis without considering the specific parameters of the switching power supply. In terms of behavioral model construction, Norton or Thevenin equivalent can generally be used to give an equivalent circuit of a CE model, and its parameters are determined by analysis or test [8,9]. In addition to these two aspects, there are other methods for modeling SMPS, such as using a concept-named fast reconstruction method (FRM) to deal with the time domain simulation of common mode conducted disturbances [10].…”