EMI Filter Performance of Transformerless Topology for Photovoltaic Applications

Abstract

This paper presents the deterministic approach to clarify the inductance and capacitance of a low-pass filter. Suitable values depend on the power system quality and system stability. Besides, the effectiveness of a low-pass filter on suppressing the electromagnetic interference (EMI) noise by Pulse width modulation (PWM) is investigated. As a well-known, total harmonic distortion of output voltage strongly relies on the filter parameters. Similarly, a transformerless topology of Photovoltaic (PV) applications with unipolar PWM has a big problem with the leakage current. Its magnitude relies on resonance condition in common-mode current loop are not clearly explained. Moreover, the common-mode (CM) and differential-mode (DM) voltages are measured by a line impedance standard network (LISN). These values need to satisfy the Electromagnetic Compatibility (EMC) limits. In some cases, an additional EMI filter is needed to restrain the high CM and DM noises under the EMC limits. The real values at the install location of the PV inverters which are measured without a LISN are totally different. So, this paper investigates the performance of the EMI filter through comprehensive simulation results for a representative PV application.