EMI noise control methods suitable for electric vehicle drive systems

Methods to control electromagnetic interference (EMI) noises, especially common mode currents and radiations that are generated in electric vehicle (EV) drive systems, were studied using an electric vehicle (EV) prototype. Fast fourier transform (FFT) analyses of the voltage and current appearing in the EV drive systems showed that electromagnetic interference (EMI) noise sources are produced by voltage fluctuations occurring at the time of switching operations and the produced noise sources cause common mode currents to flow into the ground when the body frame is connected to the ground. Moreover, the flowing common mode currents induce radiated EMI noises, while the generated EMI noises are transmitted between the inverter, batteries, and motors. Thus, the produced radiated EMI noises have an effect on nearby vehicles. A method was proposed that controls common mode currents produced in EV drive systems so as to prevent a series resonance phenomenon from occurring in common current paths formed in EV drive systems. This method is also effective in controlling radiated EMI noises. Furthermore, to control radiated EMI noises, another method was proposed that cancels the surface currents flowing in P and N power transmission lines between the inverter and batteries. Effectiveness of these proposed EMI noise control methods was verified from simulations and experiments.