Modelling & Design of a Prototype DC/DC Converter for Trip Coil Applications

Sammanfattning: High voltage circuit breaker testing is a major part in substation test industry. The minimum trip voltage test is one of the standard circuit breaker tests performed. In this master thesis, a prototype switch-mode DC/DC power supply with digital control has been designed and implemented on behalf of Megger Sweden AB targeting at assessing developing a battery-powered product dedicated to perform the minimum trip voltage test. The report consists of several parts. In the first part, the theoretical background on modelling switch-mode power converters in continuous and discrete domain is presented. Then, the presented modelling recipe is followed to model a synchronous four-switch double-mode DC/DC converter, which can operate either in buck or buck-boost mode. Given the preliminary specifications, the power components are dimensioned using an analytical approach. Digital voltage mode control is implemented for each mode. The whole system is modelled in Matlab/Simulink and its operation is verified by means of simulations. The modelled power converter is implemented as prototype. The power components are selected as a result of the dimensioning analysis. The digital control loop is implemented using a Texas Instruments C2000 micro-controller. Lab measurements are obtained for six different test cases and they are compared with the corresponding simulation results. The obtained measurement data depict close match to the simulated expected values, which verifies the modelling stage. Finally, discussion is hold on how layout and hardware issues have compromised the prototype design specifications. Moreover, concrete hardware changes are proposed that will enable improvements in the next prototype version.