基于分布式控制的减小开关数量模块化多电平串并联电池储能系统

In this article, a novel reduced-switch-count sub-module (SM) topology for a modular multilevel converter with series and parallel connection capability has been proposed. In existing topologies for such converters, a pulse-width modulation (PWM) carrier skew, or a reference mismatch between SMs in a distributed/decentralized control implementation can lead to invalid switching states being encoded, thereby shorting one or more dc sources within the converter. This in turn forces atypical SM implementations that are not compatible with established control methods. In contrast, the proposed topology eliminates these undesirable current flow paths under such scenarios, enabling existing distributed/decentralized control implementations to be naturally extended to converters with parallel connectivity. The proposed topology uses a simple multi-carrier PWM scheme. It does not introduce additional switches in the conduction path during series-connected states over a conventional H-bridge SM. A distributed control implementation has been described for a grid-connected battery energy storage system utilizing the proposed topology. A five-sub-module prototype with 4 kWh battery capacity has been built. Experimental results from operating the prototype in both standalone and grid-following mode, connected to the 120 V utility grid, validate the viability of the proposed topology and the associated control scheme. It is expected that the reduced cost and complexity enabled by the reduced switch count and distributed/decentralized control implementation will result in an accelerated adoption of these converter topologies.