Long Lifetime DC-Link Voltage Stabilization Module for Smart Grid Application Huai Wang * , Henry Chung † , Wenchao Liu † , Frede Blaabjerg * * Center of Reliable Power Electronics (CORPE), Department of Energy Technology, Aalborg University, Denmark. † Centre for Smart Energy Conversion and Utilization Research (CSCR), City University of Hong Kong, Hong Kong. hwa@et.aau.dk ; eesch@cityu.edu.hk ; wenchao.liu@cityu.edu.hk ; fbl@et.aau.dk ABSTRACT Power converters enable efficient and flexible control and conversion of electric energy among different smart grid players (i.e. producers, energy storage systems, and loads). One of the expected features of smart grid is that it will be more reliable compared to conventional grid. However, power converters are one kind of the lifetime limiting components applied in smart grid. One of the major causes is the malfunction of electrolytic capacitors (E-Caps) which are widely used for stabilizing the dc-link voltage in various types of power converters applied in smart grid. A dc-link module is therefore proposed in this paper with a reduced value of dc-link capacitor and a series voltage compensator. It allows the replacement of the popularly used E-Caps with alternatives of longer lifetime, like power film capacitors. The basic concept, implementation and operation principle of the dc-link module are given. The theoretical analysis is verified by simulation and experimental results. 1. INTRODUCTION The smart grid is characterized by a two-way flow of energy and information, which creates an automated, widely distributed energy generation and delivery network [1]. Fig. 1 gives a possible scenario of the future power system based on smart grid technologies [2]. Power electronic building blocks (PEBBs) and mechanical building blocks (MEBBs) are the intelligent energy conversion nodes interconnecting the producers, energy storage systems and loads. PEBBs composed of power converters enable efficient and flexible control and conversion of electric energy. However, the reliability issue of PEBBs as discussed in [3] is a challenge in smart grid applications. PEBBs have various architectures, of which the ones shown in Fig. 2 are dominant for power generation, transmission, and consumption in the smart grid. They are widely applied in lighting application, telecom power supplies, photovoltaic (PV) systems, wind turbine systems and so on. Multiple power converters are interconnected by a dc link. The dc- link voltage is supported by a capacitor bank for absorbing instantaneous power difference between the input source and output load, minimizing voltage variation on the dc link, and providing sufficient energy during the hold-up time of the system. Fig. 1. A possible scenario of the future power system based on smart grid technologies (PEBB- power electronic building block, MEBB- mechanical building block, ME- mechanical electrical interface) [2]. (a) Ac-dc-dc or dc-dc-ac power converters with a dc-link. (b) Ac-dc-ac power converters with a dc-link. (c) Ac-dc or dc-ac power converters with a dc-link. Fig. 2. Typical power electronic building blocks used in the smart grid (power flow from left-to-right, right-to-left, or bi-directional).