การเชื่อมต่อคอนเวอร์เตอร์ชนิดควอไซน์สเตจเดียวเข้ากริดสำหรับระบบกักเก็บพลังงานแรงดันต่ำด้วยเทคนิคการมอดูเลตเชิงสเปซเวกเตอร์

Abstract

A quasi-single-stage converter (QSSC) consists of a dc-dc converter and an ac-dc converter, which are applied for bi-direction power flow grid connections for low-voltage energy storage systems. The power produced by a dc-dc converter is decreased when compared with a two-stage converter, resulting in improved overall efficiency. However, the unbalanced voltage in dual dc-port is due to the QSSC structure effect of the modulation technique, which is more complex, and the common mode voltage issue, which occurs from QSSC operation, which leads to common mode current that makes an error in the protection system. That consequence is low stability. This thesis suggests connecting grid-connected QSSCs to low-voltage energy storage systems so that power can flow in both directions. These systems would be controlled by real power and reactive power control systems. By using the dc voltage control technique, which is a simple and uncomplicated method, and the space vector modulation technique based on large and medium voltage vector selection, which design switching sequences to mitigate the common mode voltage problem. The proposed methods are verified by simulation results, and the results show good steady-state and dynamic performance