A power converter (system interconnection inverter) is used to convert DC power, generated in a photovoltaic power system or the like, into AC power and supply it to a power system. This power converter includes: a boosting converter configured to boost a DC voltage; and an inverter configured to convert the direct current into alternating current. Upon switching of a switching element of the boosting converter, the inverter, or the like, common mode voltage (neutral point potential) is fluctuated.
A single-phase inverter has an H bridge configuration employing a switching element, and is subjected to 3-level PWM control, for example. Due to this control, common mode voltage is fluctuated. The fluctuation of the common mode voltage causes leakage current flowing to a ground (earth) and high-frequency noise. The high-frequency noise is reduced by inserting a common mode choke coil between a pair of output terminals of a DC power supply and a pair of input terminals of a boosting circuit (see Japanese Patent Laying-Open No. 2011-147238).
Upon of switching of the switching element of the boosting converter or the inverter, ringing occurs. A conventional common mode choke coil can reduce noise in a low frequency region such as a switching frequency. However, according to various experiments conducted by the inventor of the present application, it was found that the noise reduction effect is low in a high frequency region such as a ringing frequency and a frequency of a harmonic wave thereof.
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