With the extinction of fossil fuels and high increase in power demand, the necessity for renewable energy power generation has increased globally. Solar PV is one such renewable energy power generation, widely used these days in the power sector. The inverters used for power conversion suffer from power losses in the switching elements. This paper aims at the detailed analysis on switching losses in these inverters and also aims at increasing the efficiency of the inverter by reducing losses. Losses in these power electronic switches vary with their types. In this analysis the most widely used semiconductor switches like the insulated gate bipolar transistor (IGBT) and metal oxide semiconductor field effect transistor (MOSFET) are compared. Also using the sinusoidal pulse width modulation (SPWM) technique, improves the system efficiency considerably. Two SPWM-based singlephase inverters with the IGBT and MOSFET are designed and simulated in a MATLAB Simulink environment. The voltage drop and, thereby, the power loss across the switches are compared and analysed. The proposed technique shows that the SPWM inverter with the IGBT has lower power loss than the SPWM inverter with the MOSFET.

High-speed switching capabilities of SiC MOSFET power modules allow building high power converters working with elevated switching frequencies offering high efficiencies and high power densities. As the switching processes get increasingly rapid, the parasitic capacitances and inductances appearing in SiC MOSFET power modules affect switching transients more and more significantly. Even relatively small parasitic capacitances can cause a significant capacitive current flow through the SiC MOSFET power module. As the capacitive current component in the drain current during the turn-off process is significant, a commonly used method of determining the switching power losses based on the product of instantaneous values of drain-source voltage and drain current may lead to a severe error. Another problem is that charged parasitic capacitances discharge through the MOSFET resistive channel during the turn-on process. As this happens in the internal structure, that current is not visible on the MOSFET terminals. Fast switching processes are challenging to measure accurately due to the imperfections of measurement probes, like their output signals delay mismatch. This paper describes various problems connected with the correct determination of switching power losses in high-speed SiC MOSFET power modules and proposes solutions to these problems. A method of achieving a correct time alignment of waveforms collected by voltage and current probes has been shown and verified experimentally. In order to estimate SiC MOSFET channel current during the fast turn-off process, a method based on the estimation of nonlinear parasitic capacitances current has also been proposed and verified experimentally

The increased power density, reduced switching losses with minimum electromagnetic interference (EMI), and high efficiency are essential requirements of power converters. To achieve these characteristics, soft power converters employing soft switching techniques are indispensable. In this paper, a ZCS/ZVS PWM AC/DC converter topology has been emphasized, which finds applications in high power systems such as automobile battery charging and renewable energy systems. This converter scheme maintains zero current and zero voltage switching conditions at turn on and turn off moments of semiconductor switches, respectively and soft operation of rectifier diodes that lead to negligible switching and diode reverse recovery losses. Moreover, it improves power quality and presents high input power factor, low total harmonic distortion of the input current (THDI) and improved efficiency. The validity of theoretical analysis of the proposed converter has been carried out experimentally on a 10 kW laboratory prototype. Experimental results prove that the soft switching operation of the semiconductor switches and diodes is maintained at 98.6% rated load efficiency. In addition, the performance evaluation has been performed by comparative analysis of the proposed converter with some prior art high power AC/DC converters. Efficiencies of the proposed and prior art high power topologies have been determined for different load conditions. The highest efficiency, power factor and lower THDI of the proposed converter topology complies with international standards.

Soft-switching technologies can effectively solve the problem of switching losses caused by increasing switching frequency of grid-connected inverters. As a branch of soft-switching technologies, load-side resonant soft-switching is a hotspot for applications of high-frequency inverters, because it has the advantage of achieving soft-switching without using additional components. However, the traditional PI control strategy based on the linear model is prone to destabilization and non-robust dynamic performance when large signal perturbation occurs. In this paper, a novel Passivity-Based Control (PBC) method is proposed to improve the dynamic performance of load-side resonant soft-switching grid-connected inverter. Besides, the model based on the Port Controlled Hamiltonian (PCH) model of the soft switching inverter is carried out, and the passivity-based controller is designed based on the established model using the way of interconnection and damping assignmentpassivity based control (IDA-PBC). Both stable performance and dynamic performance of the load-side resonant soft-switching inverter can be improved over the whole operating range. Finally, a 750 W load-side resonant soft-switching inverter simulation model is built and the output performance is compared with the traditional PI control strategy under stable and dynamic conditions. The simulation results show that the proposed control strategy reduces the harmonic distortion rate and improves the quality of the output waveforms.