Modeling and Simulation of Soft Switching in Traction Inverter
Examensarbete för masterexamen
Electric power engineering (MPEPO), MSc
Gandla, Lakshmi Priya
In this thesis, two soft switching inverter topologies the Active Clamped Resonant DC Link Inverter (ACRDCLI) and theAuxiliary Resonant Commutated Pole Inverter (ARCPI) are designed. Their performance is compared with the Hard Switched Inverter (HSI) in simulations. In order to ensure the balance of the soft switching resonant circuit and to achieve a certain reference current, the parame ters of the circuit components are selected according to the references and modified appropriately. The load is modelled as a Permanent Magnet Synchronous Machine (PMSM) equivalent circuit and the parameters are taken from the Finite Element Method (FEM) data based on a fixed operating point. The total power losses in the switches are calculated based on the loss profile in Piecewise Linear Electrical Circuit Simulation (PLECS). Hysteresis current control and Space Vector Pulse Width Modulation (SVPWM) are used to control the current of the ACRDCLI and the ARCPI respectively. Two different state machines have also been designed to ensure the proper operation of the two soft switching topologies. The same control method is used for two HSIs as a control group to have a fair comparison. By simulating each topology under the similar conditions it can be concluded that each topology can output similar power and the total losses in two soft switching topologies are reduced by 18% compared to HSI, especially in switching losses by 98% at 33 kHz switching frequency. Due to the circuit complexity and poor Total Harmonic Distortion (THD) perfor mance of the ACRDCLI only the ARCPI is further analysed for different switching frequencies and current operating points. At high switching frequency of 80 kHz the THD value for the ARCPI is 0.286 % and for the HSI the THD is 0.366 %. With increasing switching frequency the THD for the ARCPI is smaller than the HSI and the ACRDCLI. The ARCPI gives the maximum efficiency of 97.57 % at 25 kHz switching frequency. Compared to the HSI there is an efficiency improvement of 1.71 % with the ARCPI at high switching frequency.