Modeling Inverter Losses for Circuit Simulation

Transformer-like inverter models can represent a very good alternative to common switch-diode models for simulation, reducing convergence problems and/or calculation time. They may also provide easier insight into the converter operation and power loss effects, at least from the point of view of the applicants, aiding for design and teaching purposes. The paper shows how conduction and switching losses can be incorporated in the transformer-like inverter model in a simple and intuitive way, which requires very few parameters and allows for separate modeling of lossless behavior, conduction losses and the switching losses. Loss models are proposed in some versions differing for the accuracy and simulation easiness. In any case, the resulting inverter lossy model is very compact and can be implemented by just a pair of nonlinear controlled sources as basic building blocks, available in any circuit simulation program, as the free of charge and widely used PSpice student version

Cost-effective Line Termination Net for IGBT PWM VSI AC Motor drives

The full performance of a series line termination net (LTN) has already been achieved by means of parallel ferrite-core inductors and not inductive power resistors, affecting integration and cost-effectiveness in medium-power PWM AC motor drives. A novel LTN design concept is here presented, namely IRONET, based on the exploitation of the inductor core loss as part of the wanted high-frequency LTN response. Iron cores are adopted instead of larger ferrite-core thanks to proper eddy-current density, set by design of lamination thickness and winding turns. The effective high-frequency behaviour of lossy power inductors is analysed and discussed, defining small-size R-C simple compensation. An IRONET prototype has been realised and tested for a 55 kW-rated IGBT induction motor, showing IRONET effectiveness very close to full performance even by common 0.35 mm laminations

Load Curves at DC Inverter Side: a Useful Tool to Predict Behavior and Aid the Design of Grid-connected Photovoltaic Systems

The paper proposes a novel analysis and design method providing the designer with an aid useful to compare different solutions and to optimize component dimensioning, in the field of electronic systems, for direct conversion of PV energy, devoted to be connected to an utility grid. The novel concept of load curve in DC frame is first introduced that allows to find the system steady-state operating point both in DC and AC frame leading to a prediction technique. Predictions by load curve technique are shown to be validated by experimental results obtained from an ad hoc designed prototype system. Then the technique is applied to evaluate the effect of parasitic parameters in working point displacement with respect to the design ideal case. As an example, this ability of the load curve technique to help the design is exploited in the practical case of a PV generator installed at the Polytechnic University of Turin and results are verified by means of PSpice simulations