Conducted Emission Simulation
The increasing complexity of nowadays wireless RF devices increases the demand for accurate and efficient simulations of large and complex RF designs. Identifying and predicting potential issues early in the design process saves resources, time, and money. As performance requirements increase and electronics proliferate, the risk of interference leading to degraded performance, unintended consequences—or even failure—rises dramatically. Electromagnetic compatibility (EMC) and meeting regulatory standards, for example CISPR 25, is highly needed in the electric vehicle industry. Using ANSYS HFSS combined with ANSYS Circuit tool, the full electric system can be simulated to identify and mitigate potential sources of EMI/EMC issues with reduced physical testing to deliver high-performance, safe and compliant designs.
Overview
In this blog we will be using the ANSYS Electronics Desktop (AEDT) to run a conducted emission analysis of full electric vehicle Including chassis, battery, cables, inverter, motor and an antenna, as seen below.
ANSYS HFSS will be used to simulate the full vehicle and ANSYS Circuit will be used to perform transient analysis to calculate the conducted emission of the full system.
HFSS Setup
In this demo we will simulate the vehicle model with HFSS. The HFSS model will be simulated at a frequency of 100 MHz with a frequency sweep from DC to 100 MHz with 401 points. The simulation takes 1 hour and 56 minutes to solve using a 24 core machine with a RAM need of ~ 76 GB. The figure shows the adaptive mesh generated by HFSS.
Full Circuit Model
After the HFSS simulation is completed, we can drag and drop the HFSS model into circuit. The HFSS model will be linked as an S parameter block. Below is the circuit model including the details of the whole system. The LISN component selected for this example uses the CISPR25 standards.
Battery
600 VDC battery is connected to the LISN for CE simulation and two capacitors are added to suppress some of the noise. Cables connects the battery to the busbar, as seen below.
Inverter
The 600 VDC from the battery is connected to the busbar and power the 3 SiC FET inverter. The SiC switching FET outputs the signal to the three terminals that are connected to cables that leads to the motor, as illustrated in the below figures.
Motor
The motor is represented in circuit with an equivalent circuit representation and is connected through cables.
Antenna
The model also has an antenna placed on the car roof. The antenna is connected to a matching network in circuit to improve the matching as seen below, and is terminated with a 50 ohm resistor in the circuit model.
Simulation Results
The below figure shows the voltage versus time of the power line at the output of the LISN.
we can also plot the switching waveform as shown below.
The circuit simulation also calculate the current versus time at each node in the circuit. For example, we can plot the motor current as shown below.
In circuit post processing, we can also use the built in FFT algorithm to calculate the spectral response of the transient simulation results. In the figure below, we show the conducted emission in dBuV at the LISN output.
After the circuit simulation is completed, we can push the calculated excitations back into HFSS to change the excitation magnitude and phase and update the fields plot as a post processing step without the need to resolve the HFSS model. Below we see the updated magnetic fields plot at 20 KHz after pushing the excitation.
A complete demonstration is provided in the video link below:
Downloadable Resources