Research Outputs
Modulation and control of Series/Parallel Module for ripple-current reduction in star-configured split-battery applications
Split-battery converters based on cascaded H-bridges (CHBs) are gaining popularity due to their excellent physical modularity. During operation, however, the batteries experience substantial current ripple. Conventional ripple-current reduction methods rely on bulky passive components or complicated control. This article presents modulation and common-mode voltage injection methods for cascaded double-H-bridge converters (CHB 2). The control methods directly mitigate the source of the ripple current—the fluctuating arm power—by exploiting the parallel interconnection across the CHB 2 arms. In the lab setup, the proposed solution approximately halves the battery current ripple compared to the CHB counterpart. Finally, this article studies component sizing and limitations of the proposed solution.
Modular multilevel Series/Parallel converter for bipolar DC distribution and transmission
This article proposes a novel bipolar-type dc system suitable for both distribution and transmission systems based on modular multilevel series/parallel converters (MMSPCs). The system features decoupled operations of each pole of the bipolar system, being able to operate in both asymmetrical and regenerative modes. This enables two independent dc systems by using a single grid-tied converter. The MMSPC is based on a three-switch cell configuration and enables a simple balancing mechanism in combination with a wide range of output voltage frequencies. The simple balancing mechanism is the key to enable the dc operation and lead to simpler scalability for different voltage levels. Theoretical studies and experimental results are provided to verify and characterize the proposed system.
Hybrid energy storage system based on a multioutput multilevel converter
Energy storage systems (ESSs) allow improving the stability and efficiency of the electrical grids with a high penetration of renewable energy sources. Moreover, the use of Hybrid ESSs (HESSs) enables storage solutions with both high-energy and high-power densities, by combining different storage technologies such as diverse battery chemistries, ultracapacitors, or hydrogen fuel cells to name a few. In this article, an HESS-based multioutput multilevel (MOM) converter is presented. The proposed topology enables decoupled control of each ac converter voltage output. The internal switching states further allow the use of different storage units and high-quality multilevel voltage in each ac output. The mathematical model of the proposed topology and the defined operation region of the system, besides a model-predictive control strategy, are developed. Finally, simulation and experimental results validate the performance of the proposed topology.
Operation of a hybrid energy storage system based on a cascaded multi-output multilevel converter with a carrier-based modulation scheme
Hybrid Energy Storage Systems (HESSs) have gathered considerable interest due to their potential to achieve high energy and power density by integrating different storage technologies, such as batteries and capacitors, to name a few. Among the various topologies explored for HESSs, the multi-output multilevel converter stands out as a promising option, offering decoupled operation of the AC ports while maintaining an internal balance among the diverse storage units. In this paper, the operation and restrictions of a HESS based on a multi-output multilevel converter with a carrier-based modulation scheme are presented. The study provides compelling evidence of the correct operation of the proposed modulation scheme and highlights its advantages, including simplicity and stability.