Pulse Density Modulation Applied to Series Resonant Inverter and Ac‐Ac Conversion

The PDM control joins together between the concepts of soft switching and hard switching. Its application to the series resonant inverter cancels the switching losses and uses dc bus without storage capacity. Objectively, the PDM controls led to ac‐ac converters with high efficiency (zero switching loss), small size (no storage capacity) and with the possibility of a self power factor correction. However, the operating analysis of these converters is very complex because the operation is done on two time scales and leaves questions unanswered. The average modeling facilitates the analysis of the operation and leads to establish: (i) an analytical expression of the power factor, (ii) the linearity conditions of the power characteristic, and (iii) a model of ac‐ac series resonant multi‐converter which is independent of the carriers. In the case of ac‐ac series resonant multi‐converter, the coordination of carriers allows to shape the power characteristic. Among the three types of coordination presented, there is an original coordinate that linearizes the power characteristic. The results are validated by simulations carried out in Matlab SimPower systems

Model-free control of dc/dc converters

International audienceA new "model-free" control methodology is applied for the first time to power converters, and in particular to a buck converter, and to a Cuk converter. We evaluate its performances regarding load and supply variations. Our approach, which utilizes "intelligent" PI controllers, does not require any converter identification while ensuring the stability and the robustness of the control synthesis. Simulation and experimental results show that, with a simple control structure, insensitivity to power supply fluctuations and to large load variations is ensured

Comparative Study of NPC and Cascaded Converters Topologies

Abstract-Multilevel converters have many advantages which are the capacity to generate a very good quality of waveforms, the reduced switching frequency, the low energy loss and the low effort on power devices. They are used in different power electronic applications including statics synchronous compensators (STATCOM). This paper presents a comparative study of Neutral Point Clamped (NPC) and H-bridge cascaded converters. A theoretical analysis of NPC and cascaded multilevel is presented. The generalized study for N levels converters topologies is derived. The theoretical study is validated using computer simulation in Matlab/Simulink/SimpowerSystems environment. Output voltage and total harmonic distortion are compared