Abstract:
The DC fault has become one of the most serious obstacles for the development of DC system because of its wide impact range and large fault current. The modular multilevel converter (MMC) can realize the DC fault ride-through by deploying bipolar submodules, which however sacrifices the characteristics of both low construction cost and high efficiency under normal operation. In order to find out a MMC topology with consideration of hardware cost, operating efficiency and DC fault ride-through capability, four categories including thirteen kinds of modular topologies are derived by abstracting the general structure of DC-AC converter and allocating the basic modules for each arm. A T-type alternate arm multilevel converter is proposed with the arm phase-shift modulation that promises both high efficiency and DC fault ride-through. Various modular topologies with DC fault ride-through capability are compared in terms of construction costs, operating losses, reliability and applicability, which can provide a direction for DC-AC conversion applications.