Operation of aerial inspections vehicles in HVDC environments Part B: Evaluation and mitigation of magnetic field impact

Using robotic systems to conduct remote inspections of offshore wind farm HVDC converter stations has been proposed as a promising solution to reduce the operation and maintenance (O&M) down-time and costs. However, the nature of the electromagnetic field environment inside HVDC valve halls presents a challenge for the operation of traditional off-shelf inspection robots. High electrostatic interference to inspection unmanned aerial vehicles (UAV) has been studied in Part A of this paper. In Part B, the impact of the external magnetic field on the operation of an inspection quadcopter's propulsion motors is assessed. An experimental method is proposed to identify the maximum magnetic field tolerable by off-the-shelf quadcopter motors. The reported method can be used to test commercial off-the-shelf quadcopter motors to identify their suitability for use in HVDC valve halls inspection robots. The paper experimental results show the failure of direct torque control (DTC) algorithm, that is used in quadcopters speed controllers in mitigating the magnetic field impact on motor's speed and current consumption. (paper)