Active power decoupling scheme of symmetrical LCL structure in single‐phase grid‐connected voltage source inverter for ultra‐high voltage transmission

Abstract

SummaryThe voltage source converter (VSC) is an important component of ultra‐high voltage (UHV) technology, where the former is responsible for converting new energy sources into electricity and the latter enables the transmission of electricity over long distances. However, the VSC has a serious problem of oscillation power under three‐phase unbalance, which comes from the single‐phase voltage source inverter (VSI) that is the basic structure of VSC. So there is always the requirement for active power decoupling (APD). Conventional passive solutions increase the overall size significantly, and existing active solutions either require the addition of a decoupling topology or rely strongly on their own original topology and more complex control. To overcome this drawback, this paper proposes an improved APD method with a combination of topology‐type and control‐type decoupling features for single‐phase VSI based on the symmetrical LCL filter for solving the power oscillation problem of VSC at the source. The proposed structure can decrease common mode interference and can absorb the oscillation power by the original filter capacitors of the LCL filter. Besides, the original circuit components can be reused, and the decoupling is simple enough to achieve APD without affecting the full bridge control. Next, the control is optimized to reduce the compensation error and input voltage. Finally, the experimental device is carried out to verify the effectiveness of the proposed method.