Field Weakening Strategies to Suppress Intermediate DC-DC Conversion Stages in Hybrid Construction Machinery

Hybrid Construction Machinery differs from conventional Hybrid and Full Electric Vehicles since the electrification can be applied not only to the traction system, but also and mainly to its attachments, which generally are the major responsible for diesel consumption. A dc-dc converter stage is usually applied between the battery bank and the motor drive in order to properly deal with the substantial battery voltage variation as a function of its state-of-charge (SoC). This work presents how a field weakening strategy can be applied to a Permanent Magnet Synchronous Machine (PMSM) drive in order to allow direct connection of the batteries to its dc link, therefore suppressing the need of a dc-dc stage and, consequently, reducing the hybridization costs, weight and volume. Simulation results are presented in a ditch excavation cycle.