DC Voltage Level–Based Power Supply Prioritization in Multi–Inverter System : Marine Use Case

Abstract

This paper introduces a multi-inverter system power supply prioritization method based on the system's DC voltage level. The purpose of the functionality is to first utilize the more desirable power source in the inverters' intermediate DC circuit to the fullest, before loading the less desirable one. This is done without any external controllers but rather utilizing existing inverter functionalities in a novel manner. First, the basic principle of the functionality is explained and then the operation is demonstrated in the marine environment by presenting monitoring data from a ship utilizing said function in 1.7 MW shaft generator system with 2.0 MW thruster connected to the intermediate DC circuit. The functionality enables to use the full benefits of the shaft generator as more fuel efficient power source, prior to the rest of the thruster's required power is taken from ship's auxiliary generators. This lowers the overall fuel consumption of the ship and helps to keep the ship's AC grid stable as only the power the shaft generator is not able to provide for the thruster is taken from the AC grid.