E-goverment service evaluation in Rwanda: A design perspective

Abstract

for the single-phase inverter. It is in this chapter that the state of art is deeply identified. The third chapter proposes a topology that is based on a design of an inverter using a topology that replaces an electrolytic capacitor in DC-link by a much smaller polypropylene capacitor in the DC-link. It shows the benefit of using the polypropylene capacitors instead of electrolytic capacitors. The proposed topology can use a standard three-phase transistor bridge for a single-phase grid connected inverter. The bridge is used in a different way for single-phase injection with one leg for boost and two legs for an H-bridge. It is in this chapter that a DC voltage modulation technique is analyzed. Moreover, the calculation of RMS currents for the proposed topology compared to the classical topology is presented in this chapter. Chapter 4 analyses the stability of the DC-link of the proposed topology, partly using numerical inverse Laplace transform. The stability is not granted due to an inherent resonance of the topology. The validation of the stability was done by simulation as well as by a lab experiment. The fifth chapter proposes frequency synchronization using a Double Integration Method (DIM) after a brief discussion about drawbacks of the typical phase locked loop (PPL) control for single-phase inverters. The chapter presents some simulation, and lab results related to the DIM. The sixth chapter presents a design of an IGBT gate driver. It proposes a circuit with desaturation protection using the undervoltage protection of the gate driver. This chapter presents the simulation and lab results of the designed IGBT gate driver. The seventh chapter focuses on testing the whole system. In this chapter, the system was connected to the grid to test the inductor current control. Chapter 8 draws some conclusions and recommendations for the future work.