Robust Enhanced Voltage Range Control for Industrial Robot Chargers

The two-stage converter has become a popular off-board topology for high power charging due to its high efficiency and economy. However, a series of performance degradations caused by operating frequencies which deviate from the resonant frequency are its most significant disadvantage. This drawback has become a particularly significant challenge in industrial robot charging applications. This paper proposes a linear segmented voltage control strategy that allows the voltage to be manipulated in segments depending on the state of charge. It allows for a wider voltage range while achieving excellent control accuracy and compelling operational performance. Not only is the implementation of this control strategy discussed, but engineering issues such as which adjustments to the parameters of the LLC resonant tank are required are also analysed. In addition, it is discussed how the PFC module should be adjusted for the output voltage under this control strategy. Finally, a prototype with a maximum output power of 20 kW is produced to verify the various performance improvements of this strategy in high-power charging applications.