Retrofit solution - mitigate 480V power system harmonics generated by automated guided vehicle charging system at container terminal

This paper describes a retrofit harmonic mitigation solution for the 480V power supply system designed for the battery charging system for the 72 automated guided vehicles (AGVs) at a large container terminal. The individual battery charging system for each AGV consists of 18 six-pulse thyristor modules, with each module rated at 7kW, 40V dc, and an AGV charging capacity of 126kVA at 720V dc. The supplier of the battery and battery charging equipment made no effort to mitigate harmonics and power quality issues in the design of the 480V power system. Design engineers for the container terminal performed a harmonic analysis when the power system design was configured based on the cabling and wiring information provided by the supplier. The analysis showed high harmonics, much higher than the limits prescribed in IEEE Std. 519. To achieve proper operation of the AGVs without affecting other automation equipment at the terminal, active filters were retrofitted. This paper discusses the test results for and limitations of mitigating harmonics for the first phase of retrofitting six active harmonic filters. This paper also provides recommendations for designing the port AGV power system.