Circulating Current Control (CCC) of Grid-Connected Hybrid Modular Multilevel Converter (MMC) for Solid State Transformer (SST) Application
Journal
IECON Proceedings (Industrial Electronics Conference)
ISBN
9798350331820
Date Issued
2023-01-01
Author(s)
Abstract
For convenient interconnection with ac/dc grid, Solid State Transformer (SST) is the more preferable solution according to the current literature. Also, recent advancements in the configuration of Modular Multilevel Converter (MMC) shows how the Hybrid MMCs provide superior performance compared to the conventional half-bridge sub-module (HB-SM) MMC. The Hybrid MMC considered here makes the use of HB SMs in addition to Full-bridge (FB) SMs. For secure operation of MMC, the foremost control objectives need to be fulfilled viz., SM capacitor voltage control, circulating current control, output current control. Thus, the article mainly focuses on this primary control objectives for the grid connected Hybrid MMC, which will be acting as back-end converter of the SST. To balance the SM capacitor voltages of MMC, the reduced switching frequency (RSF) voltage balancing (VB) technique is used in this article. The impact of this technique is compared with the traditional VB method. Then based on double line frequency, dq-frame, the closed loop circulating current control is achieved to eliminate the second harmonic components in the arm currents. Closed loop output current control having the same logic as applicable to three-phase VSC is also implemented. Furthermore, open loop power flow control is used for generating the reference for closed loop current control. To evaluate the performance of the controller, a comparative analysis of Hybrid MMC with and without application of controllers, is executed using MATLAB simulation. The impact of RSF-VB and current controllers is also presented.
Subjects
Circulating Current Control (CCC) | Hybrid MMC | Modular Multilevel Converter (MMC) | Reduced Switching Frequency (RSF) | Solid State Transformer (SST)
Type
conference paper