Simultaneous Control of Battery Charging and Load-Following for Gasoline Electric Power Systems with Output Ratio Control by a Single Parameter

Abstract

Combustion engine-based gasoline electric power system is another solution to extend flight time of the multi-copter drones, which are parallelly connected with batteries. In general, the control unit charges the battery based on the SOC (state of charge) signal from the BMU (battery management unit). If the SOC is less than predefined threshold, the control unit starts battery charging by adjusting the engine power until the battery is charged up to specific SOC (Kim in A study on the preliminary design of series hybrid-electric propulsion system for a fixed wing VTOL unmanned aerial vehicle. Master’s Degree Thesis in Hanyang University, 2016; Zhang and Mi in World Electr Veh J 3:843–848, 2009). This method is well known as Hysteresis or Bang-bang control and is good enough for generic gasoline electric power systems. Since the continuous charge and discharge characteristics of this method, it keeps the battery busy so the lifetime of the battery would be shortened and the system efficiency is affected by the battery charge/discharge efficiency. In this thesis, a control method for simultaneous battery charging and load-following for gasoline electric power systems is presented. This proposed method enables not only the gasoline electric power system to follow the load power in real time but also emulates CC–CV (constant current, constant voltage) battery charging and output ratio control features by only a single user control parameter. Moreover, thanks to the load-following feature, the battery stays in almost idle state (no charge/discharge) in normal operation so it makes the battery’s lifetime longer, and the system efficiency is not affected by charge/discharge efficiency of the battery.