A Control Method of Overvoltage Suppression across the DC Capacitor in a Grid-Connection Converter Using Leg Short-Circuit of Power MOSFETs during the Initial Charge

This paper proposes a control method of initial charging of the dc-capacitor in voltage source power converters. The proposed method is suitable for the power converter equipped with a small dc capacitor and is capable of removing the initial charge circuit. The proposed method makes a leg short-circuit by using power devices in the power converter, which discharges the dc capacitor and suppresses its overvoltage due to the initial charge. The short-circuit operation is a short time period and is used one time in each leg for distributing the loss to each power devices. The experimental verification using a 200-V, 5-kVA three-phase converter shows that the proposed method can reduce the peak voltage of the dc capacitor from 520 V to 420 V. The experimental results exhibit a good capability of the proposed method of suppressing the overvoltage due to the initial charge without fatal damage to the power devices. As a result, the proposed method makes it possible to remove the initial charge circuit resulting in a reduction in the size and cost of power converters.