Design Of A Three Phase AC-Side Common-Mode Inductor

In recent years, switch-mode power electronic converters have gained considerable popularity

because of their compact size and high switching frequencies. This makes them

suitable for power processing in various applications, including photovoltaic systems and

electric vehicles. However, their high switching frequency capabilities have a drawback. A

high-frequency common-mode voltage coupled with the switching of the power converters

excites the parasitic capacitances of the system. It leads to the flow of common-mode current.

Since the common-mode current flows through an unintended path, it can potentially

interfere with the performance of system components. Passive filters can be used to mitigate

common-mode currents. Using a common-mode inductor in conjunction with strategically

placed capacitors makes it possible to limit the flow of common-mode current.

As part of this work, passive mitigation of common-mode current will be investigated in

a variable frequency drive system. In this regard, the process of designing a three-phase ac

common-mode inductor is explained. As a first step, a mitigation strategy is proposed and

described. Next, the issue of self-capacitance of the inductor is discussed. Afterwards, the

ac common-mode inductor is designed using a multi-objective optimization-based approach.

Following this are the design results, concluding the dissertation.