Beijing Converters: Bridge Converters With a Capacitor Added to Reduce Leakage Currents, DC-Bus Voltage Ripples, and Total Capacitance Required

Abstract

Isolation transformers and bulky electrolytic capacitors are often used in power electronic converters to reduce leakage currents and voltage ripples but this leads to low power density and reduced reliability. In this paper, an auxiliary capacitor is added to the widely-used conventional full-bridge converter to provide a path for, and hence significantly reduce, the leakage current. The operation of the full-bridge converter is split into the operation of a halfbridge converter and a DC-DC converter so that the ripple energy can be diverted from the DC-bus capacitor to the auxiliary capacitor. Hence, the DC-bus capacitor can be significantly reduced while maintaining very low voltage ripples on the DC bus because it is only required to filter out switching ripples. The auxiliary capacitor is designed to allow high voltage ripples because its voltage is not supplied to any load. Accordingly, the auxiliary capacitor can also be very small as well. As a result, the total required capacitance becomes very small. The reduction ratio of the total capacitance is significant, which makes it costeffective to use film capacitors instead of electrolytic capacitors. The proposed converters can be also operated as an inverter without any restriction on power factor because the adopted four switches are all bidirectional in terms of power flow. Experimental results for both rectification and inversion modes are presented to demonstrate the performance of the proposed converter in reducing the ripples, the leakage currents and the total capacitance needed, with comparison to the conventional bridge converter without the auxiliary capacitor.

Research on SCESS-DFIG DC Bus Voltage Fluctuation Suppression Strategy for Frequency Inertia Regulation of Power Grid

“…When the SCESS-DFIG rotor side has multiple converters, DC BVF is the smallest, the instantaneous power of GSC is (19). converters.…”

“…Wang H aims at the problem of DC bus power imbalance and voltage fluctuation of Back-to-Back (BTB) PWM converter, the most direct and simple method is to increase the capacitance of capacitor [9] . Zhong Q C adopts a new topology of converter, and adds auxiliary capacitance can also stabilize the power imbalance of DC bus [19] . But this method will reduce the power density of converter, increase the volume and cost, and slow the dynamic response speed.…”

Reduction of DC-link Ripples for SiC-based Three-phase Four-wire Inverters with Unbalanced Loads

“…Although some solutions are proposed for singlephase converters, they can also be applied to three-phase converters. These solutions need extra active circuits to store the ripple energy so that the ripple energy flowing through the DC bus can be reduced or even completely eliminated [9]. However, the extra active switches and other components will increase the cost of the system.…”

A SiC-based Neutral Leg for the Three-phase Four-wire Inverter

“…Also, the DC-bus ripples cannot be fully eliminated so that no loads/sources can be directly connected to the DC-bus. Although there are many active power decoupling solutions to reduce both the ripples and capacitance in the DC bus [9], these solutions require extra switches and passive components, which increases the cost of the converter.…”