PD monitoring of power electronic converters

• Main Author: Giussani, Riccardo
• Other Authors: Sloan, Robin
• Published: University of Manchester 2016
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727946

Wind turbine converters used in multi-megawatt machines will operate at high voltages, particularly in future generations of wind turbines where direct connections to a HVDC backbone are made. Given the pressure to achieve high power densities in a converter to minimise the space utilised, the pressure on the high voltage insulation system to be reduced in size to the minimum possible is great. With it, this brings the increased risk of electrical discharge within the system insulation. The PhD project has therefore examined a number of issues: a) Evaluation of the risks posed to HV power electronic systems from electrical discharge: on the basis of a literature survey, discussions with converter manufacturers and the application of standard HV engineering models, the risks to a power electronic system in the wind turbine application will be assessed. b) Theoretical assessment of potential monitoring techniques: Given the risks that have been described in (a) above, the possible ways in which monitoring could be applied will be investigated. Each risk will be assessed to confirm that discharge mechanism that results in failure/damage will produce some form of measurable signal (whether this is through voltage, current acoustic, RF etc.). c) Experimental assessment of sensors for use in HV power electronic monitoring: Using a HV source within an anechoic chamber (to provide RF and acoustic noise reduction), a range of HV defects that could occur in power electronic systems will be simulated. The ability of suitably characterised sensors to detect the defects will be assessed. The research has then focus on RF detection of PD to develop a measurement method that can be applied to operating s power electronic converters (EPC).Firstly the RF emissions of several types of discharge have been studied in depth alongside the study of the effect of the environmental pressure on the signature of the different discharges. Then, the knowledge gathered was applied to perform and verify the effectiveness of RF measurements to online detect PD within operating EPC. Finally the applicability of the RF technique was verified for the detection of other electrical discharges (non-PD like) as electrical tracking.