Research on Electromagnetic Compatibility Technology for Electric Vehicle Motor Drive Systems
In today's automotive industry, electric vehicles (EVs) are becoming increasingly popular due to their environmental friendliness and energy efficiency. However, with the rise in the number and power of power electronic converters in EVs compared to conventional vehicles, electromagnetic compatibility (EMC) issues have grown more complex and critical. The motor drive system, being one of the three core systems of an EV and the primary power conversion device, plays a crucial role in ensuring the vehicle’s reliable and safe operation. Its electromagnetic compatibility directly impacts the functionality and reliability of the entire vehicle.
Given the significance of EMC, this paper explores the electromagnetic disturbance characteristics and propagation mechanisms within the motor drive system of electric vehicles. By analyzing these factors, we propose several strategies to enhance the EMC performance of the system. These include suppressing disturbance sources, optimizing system grounding, implementing electromagnetic shielding, and improving the overall system layout. The solutions presented in this study have been successfully applied to a pure electric vehicle, meeting national standard requirements. Our approach has proven effective in resolving EMC challenges in electric vehicles.
The motor drive system of an EV comprises multiple components, including the motor controller, which consists of a main circuit, control circuit, chassis, radiator, and cabling. The main circuit includes power modules like IPMs or IGBTs, which are major sources of electromagnetic disturbance. These components generate high-frequency switching currents and voltages, leading to significant electromagnetic noise. This noise can propagate through both conduction and radiation pathways, affecting the system's EMC performance.
Another significant source of disturbance originates from the motor itself. As an inductive device, the motor generates strong pulse currents during operation, which can travel through the power network and radiate into the surrounding environment. These disturbances often manifest as irregular pulse flows across a broad spectrum, ranging from approximately 10 kHz to 1 GHz.
To address these challenges, our study proposes several solutions:
1. **Disturbance Source Suppression**: We designed the power busbar with low parasitic inductance using a laminated busbar structure. This reduces the surge current and spike voltage, significantly lowering electromagnetic interference. Additionally, we implemented single-capacitor absorption loops and ensured that each IGBT gate driver operates on an independent power supply with a reverse bias voltage of -8V to mitigate noise.
2. **Propagation Path Elimination**: Grounding, decoupling, and shielding designs play a vital role in mitigating electromagnetic interference. We adopted separate grounding for strong and weak circuits, ensuring proper separation between digital and analog grounds. Furthermore, we utilized multi-point and single-point grounding methods and employed photoelectric isolation to block disturbances.
3. **System Immunity Enhancement**: A well-thought-out layout is essential for improving system immunity. We separated strong and weak power lines and used isolated power supplies for digital and analog signals. Additionally, we enhanced the EMC design of the control power supply by adding common mode chokes, sustain capacitors, decoupling capacitors, and filter capacitors. The control panel was also carefully designed to minimize interference, incorporating electrical isolation, derating, and appropriate filtering and decoupling circuits.
Experimental results demonstrate the effectiveness of our proposed solutions. Before applying the EMC rectification scheme, the vertical polarization test for radiation disturbances showed severe over-standard results. After implementation, the motor system met the Class 3 requirements for radiated emissions according to CISPR25:2008, with the main frequency points reduced by more than 50 dB.
In conclusion, our research provides valuable insights into enhancing the electromagnetic compatibility of motor drive systems in electric vehicles. By addressing disturbance sources, optimizing propagation paths, and improving system immunity, we have developed a comprehensive EMC solution that ensures reliable and efficient operation of electric vehicles. This work contributes to advancing the field of automotive electromagnetics and supports the broader adoption of electric vehicles.
— Journal of Tianjin University of Technology —
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