Overvoltage suppression filter design methods based on voltage reflection theory

Abstract

To reduce voltage overshoot at the motor terminal, RLC filters are used at the inverter side with an objective of increasing the rise time, while RC filters are used at the motor side as a means of reducing the load impedance at high frequency. However, no clear optimal method for determining the filter parameters has appeared. In this work, we propose filter design methods that fully utilize given conditions such as cable length, cable inductance, cable capacitance, and the reflection coefficient at the inverter side. For determining the parameters of the RLC filter, the filter transfer function is utilized to make the rise time long enough to achieve desirable overshoot level at motor terminals. In choosing the parameters of the RC filter, the reflection coefficient is regarded as a transfer function between the incident and reflected voltages, and the capacitance is chosen so that cancellation occurs between the reflected voltage and its resulting incident voltage. The validity of the proposed design method is supported by simulation results, which are also compared with the experimental results.