| Abstract |
This paper presents work carried out for the development of a power supply for a
fluid heater using an electrical tubular heat exchanger. The characteristics of this new heating technology are discussed to identify the load to supply. The developed converter comprises a
PWM rectifier to absorb sinusoidal line currents and an inverter that delivers square wave voltage to a 400 Hz transformer. Satisfactory results are obtained in opened loop for our
heating application in spite of a slight decrease of the power factor at mid-power. Modelling of the rectifier is presented and simulation results are compared to experiments. In our case, it
isn't necessary to control the response time of the DC-link current precisely because the time constant of the heating application is about a few minutes, so it is widely higher than the time constant of the power converter. However, PWM rectifiers can be used in many other applications and a non-linear control of DC-link current is also discussed. Simulation gives good results, there is no deterioration of harmonic pollution, the distortion ratio remains low. In order to improve the power factor at mid-power, a control method based on the phase shift
of the PWM sinusoidal references used for the rectifier is presented. It gives very satisfactory results since a very significant improvement of the power factor is obtained. |
